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Wild Populations of the Chinese alligator approach extinction
Biological Conservation 103 (2002) 93–102 www.elsevier.com/locate/biocon
Wild Populations of the Chinese alligator approach extinction John Thorbjarnarsona,*, Xiaoming Wangb, Shao Mingc, Lijun Heb, Youzhong Dingb, Yuelong Wud, Scott T. McMurrye a Wildlife Conservation Society, 2300 Southern Blvd, Bronx, NY 10460 USA Department of Biology, East China Normal University, 3663 Zhong Shan Road, Shanghai 200062, China c Anhui Research Center of Chinese Alligator Reproduction, Xuanzhou, Anhui 242034, China d Anhui Forestry Bureau, 47 Wuwei Road, Heifei, Anhui 230001, China e The Institute of Environmental and Human Health, Reese Center, Texas Tech University, 1207 Gilbert Drive, Lubbock, TX 79416, USA b
Received 6 June 2000; received in revised form 28 January 2001; accepted 2 May 2001
Abstract The Chinese alligator, Alligator sinensis, is on the verge of becoming extinct in the wild as a result of loss of natural wetlands in the lower Changjiang valley. Chinese alligators are only known from a small region in southeastern Anhui province, a fraction of its former distribution. Within this area, a 433 km2 reserve has been declared that contains 13 designated habitat sites totaling 41 ha. The sites consist of small ponds located within or adjacent to villages, are completely surrounded by rice fields, or are biologically marginal oligotrophic ponds set in low hills. Alligators are only present at 10 of the 13 designated sites, with the largest groups containing a maximum of 10–11 animals and one adult female. In recent years nesting is known from only four areas, but the eggs are routinely collected and hatchlings retained in the Anhui alligator breeding center. The total population of wild Chinese alligators is probably < 130 and is declining at an annual rate of 4–6%. If present trends continue, the Chinese alligator will be the first species of crocodilian to become extinct in the wild in historical times. Conservation efforts need to focus on protection of remaining wetlands and wetland restoration, and the inclusion of Chinese alligators in the active management of protected wetlands sites throughout the species’ historic distribution. # 2001 Elsevier Science Ltd. All rights reserved. Keywords: Chinese alligator; Conservation; Status; Extinction; China; Alligator sinensis
1. Introduction The Chinese alligator, Alligator sinensis, locally referred to as Yang Zi E (Yangtze alligator) or Tu Long (earth, or muddy dragon), is a small crocodilian that has a rich tradition of cultural symbolism in China. Historically, the Chinese alligator was distributed over a wide geographic area in the lower Changjiang (also known as the Yangtze) river system in southeastern China (Huang, 1982; Chen, 1985). The lower reaches of the Changjiang formerly hosted a spectacular array of lakes, marshes and seasonally flooded wetlands. However, this was one of the first areas where humankind developed rice cultivation, some 7000 years ago, and intensive agricultural development has taken a tremendous toll on the region’s low-elevation habitats * Corresponding author. Tel. +1-718-220-4069; fax: +1-718-3644275. E-mail address: [email protected] (J. Thorbjarnarson).
(Scott, 1989). By the late nineteenth and early twentieth centuries, alligators had disappeared from most of their former range and were restricted to a few marshy regions along the lower course of the Changjiang (Huang, 1987; Chen, 1990; Thorbjarnarson and Wang, 1999). Throughout the twentieth century, Chinese alligator populations continued to decline and their range shrink. By the 1950s, alligators were only found along the southern bank of the Changjiang extending from Pengze (Jiangxi Province) to the western shore of the Taihu lake and south to the foothills of the mountainous regions of southern Anhui (Huangshan mountains; Huang, 1981; Chen, 1990), and adjacent sections of Jiangsu and Zhejiang provinces. At this time Chinese alligators were still found in lakes, some streams and marshes in lowland regions along the Changjiang, and in small ponds in low hills (Huang, 1981). By the 1970s, the species’ range was even further restricted to a small region in southern Anhui and neighboring Zhejiang
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Province. Huang (1981) notes that during this time alligators were less frequently found in the typical habitat of low-elevation marshy wetlands, which had been almost completely transformed into rice paddies, and were increasingly restricted to small ponds in hills where agriculture, and human disturbance, was less intense. In 1972 the Chinese government listed the Chinese alligator as a Class I endangered species, providing it the highest degree of legal protection (Wan et al., 1998). Enforcement of regulations prohibiting the capture or killing of wild alligators, however, was not entirely effective, particularly during the 1970s and early 1980s (Watanabe, 1982). Since 1979, Chinese alligator management focused on captive breeding, and centers were established in Anhui and Zhejiang provinces (Wan et al., 1998). The Anhui Research Center for Chinese Alligator Reproduction (ARCCAR) is the largest facility housing >7000 Chinese alligators and serving as the administrative center for alligator management in Anhui Province. A 433-km2 reserve for Chinese alligators was created in the mid-1980s, encompassing a fivecounty region that contained virtually all the remaining areas with wild Chinese alligators. However, little information is available on the status of the last remaining groups of alligators in this area over the last 25 years (Thorbjarnarson and Wang, 1999). Here we present the results of a 1999 survey of the wild population of Chinese alligators. We examine recent evidence of population decline, the current status of the wild population, and the reasons for population decline.
2. Methods Field surveys were conducted from July through October 1999 at 26 sites within the five county region of the National Chinese Alligator Reserve (NCAR), including all 13 sites officially designated by the Chinese government for the protection of the Chinese alligator (here referred to as ‘‘designated sites’’; Fig. 1). At each site we mapped the ponds using a laser rangefinder and compass, characterized the physical nature of the ponds and vegetation, and conducted interviews with local residents. At most of the 13 designated sites the Anhui Forestry Bureau (AFB) employed a local farmer as a caretaker to oversee the protection of the Chinese alligators. The caretaker and other local farmers were good sources of information regarding the number of alligators, the locations of their burrows, recent nesting, and the history of habitat modification in the region. At these sites we estimated the number of alligators based on (1) nocturnal spotlight counts and (2) information provided by the local alligator caretaker and other farmers. Chinese alligators are extremely wary
and difficult to observe, so we used the number of individuals seen as an estimate of minimum population size. The number of alligators estimated by the local caretakers and farmers were generally consistent and based on observations made during their frequent work around the ponds. These observations were made over a period of many years and we feel represent a potential maximum number of alligators at each site. Residents were also questioned concerning alligator nesting and the location of nest sites. We conducted nocturnal spotlight counts only if there was evidence that Chinese alligators were present within the last three years at a particular site. These counts were initiated shortly after dark (ca. 20:00) and typically were completed before 23:00 due to the small size of most areas. We located alligators by their reflected eyeshine using headlamps or a 12-V portable spotlight. Nocturnal surveys were conducted by either walking around the perimeter of ponds, using locally available wooden boats (two sites: Hongxin, Yantang), or a two-person inflatable rubber boat. When sighted, we approached alligators as closely as possible to estimate total length (TL) in 50-cm size-class categories. The sites we surveyed represent the largest known remaining groups of alligators. In other parts of the NCAR, farmers occasionally reported the presence of individual alligators to the local AFB office. Based on these reports, and a questionnaire survey completed by the AFB in 1998, the county forestry departments were able to estimate the number of alligators in areas we did not visit. Recent alligator population trends were determined by comparing the results of our survey with information on past nesting and previous estimates of alligator population size for individual counties and sites.
3. Results 3.1. Population size Chinese alligators were observed at seven of the 13 designated sites, and we counted a total of 20 individuals at these sites (Table 1). Based on information from local caretakers and farmers, Chinese alligators had been extirpated at three of the 13 sites and the maximum number of alligators in the other 10 designated sites was estimated to be 60. In addition to the designated sites, we visited 13 other sites where the AFB believed Chinese alligators might persist. In these areas, we observed Chinese alligators at two sites, and counted a total of three individuals. Estimates from AFB staff and local farmers suggest that a maximum of 15 alligators remain at six of these sites. Overall, we found recent evidence (confirmed sightings,
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active burrows, nests) of Chinese alligators at 16 of 26 sites. We counted 23 Chinese alligators at nine sites, but information from AFB and local residents suggests there may be as many as 75 alligators present at the 16 sites (Table 1). Remaining groups of Chinese alligators contained few individuals. Four of the surveyed sites had one alligator (Table 1). The largest remaining groups had a maximum of 10–11 animals, and this was the case at four sites. We classified the size of 18 of the 23 alligators seen (Fig. 2). The size-class distribution indicated a preponderance of adult alligators and a scarcity of juveniles. The smallest animals observed were 70–80 cm TL juveniles seen at two sites. Based on reports from farmers and the results of a 1998 questionnaire survey of the NCAR, the AFB estimated that there may be as many as 55 Chinese alligators outside of the areas we surveyed (Jinxiang-10; Xuancheng—20; Guangde—5; Nanling—10; Langxi— 10). In all cases these were believed to be isolated individual alligators. Based on a maximum of 75 Chinese alligators at the 26 sites surveyed, and 55 isolated individuals at other sites, we estimate that the total number of Chinese alligators in the NCAR does not exceed 130 individuals. This represents the entire wild population as there are
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no known groups of wild Chinese alligators outside the NCAR. 3.2. Nesting and reproductive potential of the wild population Four Chinese alligator nests were found in 1999. We located nests at the Shaungken and Zhongqiao designated sites (the eggs of which were collected and taken to ARCCAR), and at Zhuangtou. Subsequently, ARCCAR reported another nest was located and collected at Yishan village in Xuancheng county. Eggs in the Zhuangtou nest were left in situ but failed to hatch. Only two of the designated sites had evidence of successful reproduction within the last 5 years, as indicated by the presence of juveniles (Table 1). 3.3. Recent alligator mortality In the NCAR, recent mortality of Chinese alligators or their emigration from designated sites was due to a variety of causes (Table 2). The accidental killing of Chinese alligators, while infrequent, is probably a significant source of mortality given the small size of the wild population. Alligators that emigrate from these sites enter areas of less suitable habitat, for example rice
Fig. 1. Location of the 13 designated Chinese alligator habitat sites in the National Chinese Alligator Reserve. Each site is identified by letter as represented in Table 1. Other sites where alligators have been reported in the last 3 years are indicated with asterisks. The location of the ARCCAR breeding center is indicated with a BC, and the Zhaungtou site is marked with ZT.
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fields or other modified landscapes and presumably end up as displaced, isolated individuals. Flooding and drought are significant factors that contribute to alligator mortality or emigration. At two sites the last known adult females died as a result of ingesting rodents poisoned in nearby fields and houses and thrown into the ponds. 3.4. Recent population trends County and site-specific information suggests that the small wild population continues to decline. AFB records from Langxi county illustrate decline in the number of villages from which Chinese alligators were reported (Fig. 3). While the number of Chinese alligators reported at each of these villages is unknown, the shrinking area from which they are reported provides evidence of population decline. Today, alligators are known from
only one site in Langxi county (Zhangcun). The average annual loss of villages in Langxi county reporting alligators from 1975 to 1999 was 4%. The AFB surveyed 66 villages for Chinese alligators in Nanling county in 1986. At that time, 193 alligators were estimated to be present in 23 villages. However, the number has subsequently declined precipitously (Fig. 4). In 1998 the AFB estimated the Chinese alligator population in Nanling county to be 32 animals in nine villages. The average annual decline (1986–1998) was 6.4% for the number of alligators, and 5.4% for the number of villages reporting Chinese alligators. Some information also exists for Chinese alligator population trends from specific sites between 1981 (Huang et al., 1985) and 1999 (our surveys; Table 3). The overall decline of 84% between 1981 and 1999 indicates an annual average loss of 4.7%. At the Hongxin site, in Xuancheng county, data from Zhu (1997)
Table 1 Summary of 1999 survey resultsa County
Site Site code
Jinxiang
E F D *
Shaungken Zhongqiao Yantang Liang Zhong Lin Zhi Ma’an
1.71 3.37 2.53 1.07 0.81 0.84
6 5 1 3 1 2
Yes Yes Yes No No No
3 1 0 0 0 0
No No No No No No
10 4 1 0 0 0
1999 1999 1992 1970s
1 3 1 1 1 1
0.285 0.674 2.530 0.357 0.810 0.420
5.85 1.19 0.40 0.00 0.00 0.00
Xuancheng
H * G ZT
Yanlin Maogia Hongxin Zhuangtou Li Yun Miao
0.36 1.25 8.44 6.08 0.67
2 2 1 7 1
Yes No Yes No No
0 0 4 2 0
No No No No No
1 3 10 5 1
1970s 1997 1996 1999 1991
2 3 2 3 2
0.180 0.625 8.440 0.869 0.670
2.78 2.40 1.18 0.82 1.49
Guangde
M L
Zhucun Jiagu Qian Mou Yuan
2.76 1.22 –
1 3 1
Yes Yes No
3 0 0
Yes Noc No
5 2 0
1997 1998
2 3 1
2.760 0.407
1.81 1.64
Nanling
B A C *
Changle Xifeng Zhalin Heyi Liu Dian Shangma Tian Guan Song Cun
0.28 2.83 2.08 2.11 – 2.20 1.67 0.39
3 1 1 2 1 1 1 3
Yes Yes Yes No No No No No
5 0 3 1 0 0 0 0
yes no no no no no no no
11 0 5 3 0 0 1 2
1996 1980s 1993 1970s 1970s
1 3 3 1 1 3 2 1
0.093 2.830 2.080 1.055
39.29 0.00 2.40 1.42
2.200 1.670 0.130
0.00 0.60 5.13
Wang Jiameu Huang Shugang Zhangcun Yuan Cun
7.64 5.35 2.29 0.50
1 4 2 1
Yes Yes Yes No
0 0 1 0
no no no no
0 0 11 0
1950s 2 1983 1 1996 1 2
7.640 1.338 1.145 0.500
0.00 0.00 4.80 0.00
Langxi
Designated sites All sites a
I K J
40.86
Pond area No. Protected? Total Juveniles Estimated Last (ha) ponds seen number nest
31 58.45
20 57
60 23
Habitat Average Population typeb pond size density (ha)
1.318 75
1.47 1.654
1.28
Sites that are not officially designated are in italics. Site codes refer to Fig. 5. Population density (alligators/ha) calculated using estimated (maximum) population values. b Habitat types are defined in the text. c There were unconfirmed reports of yearling alligators from Jiagu.
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provided evidence of reduction in the number of Chinese alligators over a 4-year period. At this site annual nesting ceased in 1996 and the last known adult female was found dead in 1999. The dates of last known nesting at each of 17 sites visited during our 1999 survey provides evidence for a decline in population reproductive output (Table 1). While in some cases these were imprecise descriptions (e.g. the 1960s), at most sites there was a good record of when the last eggs were laid (Fig. 5). Ominously, the decline has been particularly rapid since the mid-1990s and, for the first time ever, there were no wild nests reported in 1998 (with the possible exception of an unconfirmed report from Jiagu). Only one confirmed report of Chinese alligators outside the NCAR has come in recent years. In 1995, a large male (1.99 m TL) was captured and later released in Ma’anshan County in eastern Anhui along the Changjiang (Fig. 1). However, this was likely a transient animal that had been washed down one of the rivers from the NCAR during flooding. There have been no subsequent reports of alligators in this region.
Fig. 2. Size-class distribution of 18 Chinese alligators observed in the wild.
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3.5. Current status of habitat in the NCAR Although the designated sites are probably the best remaining areas for Chinese alligators, the total pond area was small (41 ha in 31 ponds), and the only area considered protected is the pond, or ponds, and not any surrounding land. The cultivation of rice and other crops frequently extends to the very edge of ponds. In many cases, there is no fringe of vegetation between the water and the cultivated fields, and at several sites (Zhongqiao, Zhucun, Yantang and Hongxin), shallow water sections of the ponds had been diked and reclaimed for rice paddies. At other sites (e.g. Shaungken, Yantang), recent construction of dikes or water control structures significantly altered the hydrology at the sites, making them less favorable to aquatic wildlife. The ponds themselves are very small, with a mean size of 1.32 ha, and at some sites mean pond size was as small as 0.09 ha (Changle). The largest pond was the 8.4 ha reservoir at Hongxin. The total size of ponds at 24 of the 26 visited sites (the two others were sections of rivers where it was impossible to delimit an area) was 58.5 ha (total of 55 ponds). In many cases, farm houses were located along the edge of the pond, and in other cases ponds are located in the midst of villages. Although
Fig. 3. Number of villages in Langxi county where Chinese alligators were reported present from 1975 to 1999. Data from Langxi office of the Anhui Forestry Bureau.
Table 2 Reports of recent sources of alligator mortality or emigration in the National Chinese Alligator Reserve Site
Reported source of mortality or emigration and year
Shaungken Zhongqiao Yantang Yantang Liang Zhong Hongxin Zhaungtou Zhucun Changle Xifeng Heyi Huang Shugang
Construction of dike and loss of part of available habitat—1991 Hatchlings dying during winter from lack of a burrow—1989–1992 Accidental shooting of last adult female while rabbit hunting—1995 Change in stream hydrology resulting in lower water temperature, increased current and more variable water level—1992 Pond drying up—1997 Last adult female died eating poisoned rodents—1999; egg collection—prior to 1996 Egg collection—1996, 1997 Juvenile accidentally killed by eel fishermen—1998 Last adult female died eating poisoned rodents—1998 Dam broke, pond emptied out—1991 Floods—1999 Floods—1983
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ponds at the designated sites are protected, water in the ponds remains under the control of the surrounding community, and is used to irrigate farmland during periods of drought, for buffalo wallows, fish farms, or rearing ducks. Under these conditions, conflicts between people and alligators are inevitable. Burrowing even a small distance into the shores of ponds will take alligators into agriculture fields, and alligator movements between ponds damages rice plants. To better understand the current distribution of alligators in the NCAR, we categorized habitats into three main types: Type 1. Relictual wetlands in low, broad, fertile valleys along principal river courses. Areas dominated by agriculture, principally rice. Type 2. Intermediate; ponds in low hill valleys (< 100 m altitude) but with significant agriculture in the valley above the pond.
Type 3. Ponds situated in low hill valleys (< 100 m altitude) at the upper edge of rice cultivation and the lower edge of tree plantations. Type 1 habitat represents the closest approximation to what was historically good alligator habitat: low elevation, alluvial floodplains containing a variety of wetlands including marshes, ponds and streams. Today, these areas have been heavily settled and the wetlands have either disappeared or been highly altered. The major rivers have levees along their banks and natural floodplains no longer exist. The principal stream tributaries of rivers have been diked and divided to form ponds which are ringed with agricultural fields and villages. Shallow ponds and marshes have been converted into rice paddies. The few type 1 habitats with alligators represent tiny remnants of formerly extensive natural wetlands. They typically are groups of small ponds (mean 2.9 ponds per site, average pond size 0.6 ha) in the midst of agricultural settlements. Nevertheless, despite their small size and the intense human use, these areas support half Table 3 Population decline of alligators at four sites where population size was estimated in 1981 and 1999a
Fig. 4. Trend in the number of number of villages reporting Chinese alligators, and the number of alligators observed and estimated present in Nanling county since 1986. Data from the Nanling Forestry Department.
Site
1981 Estimate
1999 Estimate
% Decline
Yantang Shipu Yanlin Heyi
3 4 3 22
1 0b 1 3
67 100 67 86
Total
32
5
84
a
1981 values from Huang et al., 1985. Nanling Forestry Department staff report that alligators have disappeared from the Shipu site. b
Fig. 5. Number of sites reporting alligator nests by year. Data for 17 sites visited during 1999 survey. Based on a starting point of 1955, the overall decline has been 82.4% over 44 years ( 1.8% per year).
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of the known wild alligator population (Table 1). Soils in these areas were richly organic and many of the sites had significant shallow water habitat and aquatic vegetation, both rooted and floating. At these sites we readily observed natural alligator prey (aquatic insects, crustaceans, snails, frogs, eels). Type 3 ponds offered reduced human land-use pressures but marginal alligator habitat. These sites were characterized by clearwater (oligotrophic) ponds with little aquatic vegetation or natural, shallow-water habitat. Like type 1 areas, these sites typically have multiple, small ponds (mean 2.86 ponds/site, average size 0.95 ha), but are located in hilly, partly forested terrain on rocky soil with high clay content that makes burrowing difficult. While adult alligators can survive in these ponds, they represent poor or marginal habitat. At one type 3 site (Zhalin) that was used as a release site for alligators from other areas, we were told many of the alligators left the pond and were recaptured in rice paddies further down the valley. Type 3 ponds may be less suitable for juveniles alligators than for adults, and the overall density of alligators is only half that of the type 1 sites. Despite the fact that two of the three areas where nesting is taking place fall into this category, we found no evidence for juvenile alligators at any type 3 habitat. Type 2 habitats ranged from small ponds in rice fields to medium-sized ponds in rolling hills surrounded by dry-ground agriculture. The two largest designated sites are type 2 habitats (Hongxin and Wang Jiameu), and principally for this reason the mean pond size of type 2 habitats was more than twice that of type 3 sites (mean 1.14 ponds/site, average pond size 2.76 ha). Because of the size of these two ponds, plus the relatively large size of the Zhucun site, type 2 habitats had nearly half of the surface area of protected ponds, but only about one quarter of the estimated alligator population. Hongxin offers what is perhaps the best chance for undertaking habitat improvements with the goal of maintaining a wild group of alligators. The other large type 2 site (Wang Jiameu), however, is one of the designated sites without alligators or adequate habitat.
4. Discussion 4.1. Population size and distribution trends In southern Anhui Province, alligators have probably persisted longer than in neighboring provinces as a result of the more recent initiation of agriculture in some marginal areas, a lower overall human population density and the prevalence of low hills with ponds (type 3 habitats) that offer a last refuge for alligators. Nevertheless, the number of alligators in Anhui declined
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sharply between the 1950s and the 1970s. Of 29 regions where alligators were relatively common in the 1950s, they were easily seen in only four by 1976, and had disappeared completely from nine (Chen in Fu, 1994). Huang (1981) reported that between 1956 and 1976, the number of known alligators in 11 counties in Anhui and neighboring provinces had declined from 360 to 120, an average annual decline of 3.3%. By the late 1980s, wild Chinese alligators remained only in Anhui Province, principally in small ponds in agricultural valleys and hills in five counties (Nanling, Jinxiang, Guangde, Langxi, Xuancheng), which together comprise the NCAR. Outside the NCAR, including all the sites where alligators were previously found bordering the Changjiang (Wuhu, Ningguo and Dongtu counties), ARCCAR staff report alligators were extirpated during the last 20 years. In the early 1980s, surveys in Anhui Province estimated the wild population of alligators was at least 300 individuals, comprised mostly of juveniles or subadults (Watanabe, cited in Groombridge, 1982). Based on these and other surveys, Chen Bihui calculated that approximately 500 alligators remained in the wild during this period (People’s Republic of China, 1992; Webb and Vernon, 1992). Another, more extensive survey of 129 villages (423 bodies of water) in the NCAR was organized by ARCCAR in 1985 and 1987, and estimated the number of wild alligators was 735 (People’s Republic of China, 1992). Based on this population estimate, and the fact that between 1979 and 1983 212 alligators were collected from the wild to stock the ARCCAR breeding center, it is not unlikely that approximately 1000 wild Chinese alligators were living in Anhui Province during the late 1970s. In 1994, staff from ARCCAR observed 77 Chinese alligators during spotlight counts in the NCAR (Li et al., 1996). From these counts the total alligator population in the surveyed areas was estimated to be 253, and extrapolating to the entire five-county region, the total number of remaining wild Chinese alligators was calculated to be 667–740 (Li et al., 1996). Their estimate was based on the assumption that only one third of the sites within the reserve were surveyed. But because all the principal locations actually known to have Chinese alligators were visited, the validity of this extrapolation is questionable and the total wild population was most likely considerably less than reported. Zhou (1997) provided population estimates of 378– 747 for the NCAR from 1985 to 1994. However, it is unclear how these population estimates were made. Wan et al. (1998) indicated that in 1997, the population of wild alligators was reduced to approximately 400, but no details were provided. While these survey results are hard to interpret because of a lack of information on where and how they were conducted, most current evidence suggests the total number of wild Chinese alligators declined from
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approximately 1000 wild alligators in the late 1970s to the current estimate of 5130. 4.2. Factors responsible for population decline Chinese alligators are rarely tolerated by local farmers in the lower Changjiang valley. Alligators prey on small livestock (particularly ducks), and their burrows interfere with water control structures vital for rice cultivation. Many farmers believe alligators reduce the number of fish in ponds. Hsiao (1934) stated that when ‘‘convenient’’ alligators were killed by farmers for food, but other accounts suggest that during most of the nineteenth and twentieth centuries people did not eat alligators. Nevertheless, B. Chen (personal communication) reported that after 1986, people in Anhui began eating alligator believing it was dragon meat. Although the sale of captive alligator meat from ARCCAR was approved at two restaurants, one in Xuancheng (near the ARCCAR) and one in Beijing, an illegal market emerged, and in recent years there were at least two cases of people catching and selling live alligators. The collection of live alligators, principally for zoos, has also played a significant role in the demise of wild populations (Thorbjarnarson and Wang, 1999). Wetland loss is a widespread problem throughout China, and in view of the rapid economic development of the country, this problem will continue, or even be exacerbated, in the near future (Chen and Chen, 1997) The disappearance of wetland has been particularly severe in the middle and lower Changjiang region, and this has had disastrous impacts on native wildlife. From the late sixteenth to the early twentieth century (Qing Dynasty), there was a large migration of people from the north into the lowland Changjiang region (Huang, 1982; Chen, 1990), converting the river’s floodplain into agricultural fields. However, during this period some lands were set aside as cattle ranches for the Manchu Mandarins, and in these regions of natural marshland farming was prohibited, creating de facto habitat reserves for alligators and other marsh wildlife. The Changjiang floodplain to the south of Wuhu, one of the last strongholds of the species until the mid-twentieth century, was one of these areas (Chen, 1990). Loss of wetlands continued into modern times, and today virtually the entire area is under cultivation (Watanabe, 1982). Many areas where alligators now occur are small ponds created in the late 1950s and early 1960s, during the ‘‘Great Leap Forward’’ with its emphasis on increasing rural agriculture. The use of chemicals to control the snail vectors of schistosomaiasis, and the application of large amounts of chemical fertilizers and insecticides may also affect the Chinese alligator (Chen, 1990, Thorbjarnarson and Wang, 1999). During our surveys we found clear evidence that alligators were dying from eating poisoned
rodents. Zhou (1997) reported that in 1984 two alligators died from the effects of insecticides in a farm in Jinxiang county. Increased drought and flooding that result from loss of natural vegetation throughout eastern China have also led to significant mortality of alligators (Watanabe, 1982; Zhou, 1997) or forced animals to move overland where they are captured or killed (Chen, 1990). The last individuals at Liang Zhong in Jinxiang county reportedly left the area during the drought of 1997. At the Hong Shugang (Langxi county) designated site alligators were regularly seen until the floods of 1983, when many were dispersed into the surrounding floodplain or downstream in the Langchuan river. 4.3. Factors determining the current distribution of alligators in the NCAR The nature of the existing habitats in the NCAR place severe limitations on the survival of wild alligators. While the reserve is large (433 km2), it encompasses a mixed agricultural–urban landscape with more than 2 million people (Thorbjarnarson and Wang, 1999). Ponds in the low valleys (habitat type 1 and most type 2) offer habitats favored by alligators, but intense conflicts with people. The persistence of alligators in these rich agricultural regions is due to the fact that the they are relatively innocuous and cryptic, and also because they are long-lived, so even if breeding groups no longer exist, isolated individuals may remain for many years. However, there are also a variety of site-specific habitat factors that appear to explain why alligators are found in certain areas and not in others. The agricultural and land-use history of the site is certainly a factor. In other cases, the presence of alligators is merely a reflection of the fact that the site has been used to release animals found in rice paddies or other inappropriate locations. At other sites, the prolonged existence of alligators is a result of specific habitat factors which buffer the alligators from intense human population pressures. At some sites alligators may have been able to persist because of a complex assemblage of former floodplain streams, now divided into numerous small ponds, provide a number of refuges. However, in most sites the survival of alligators appears to be related largely to the availability of relatively undisturbed areas for nesting. In some locations, the stream or pond habitat used by the alligators is bordered on one side by a partially forested, and relatively unused, hillside that provides nesting habitat. In other areas, small islands fulfill the same role. In type 3 habitats, ponds are usually surrounded by little used hillsides with scrub vegetation or pine plantations that offer nesting habitat. However, because of the small size of nearly all the remaining sites, and the intensity of the human population pressures that surround them, these
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factors have, at best, merely determined which are the last areas from which wild alligators will be extirpated. At one type 3 site (Zhalin), despite being surrounded by largely forested hillsides, having a small island that was used (until 1993) for nesting, and being the principal release site for alligators found in Nanling county, the estimated alligator population numbers only five individuals. 4.4. Management alternatives: habitat protection, rehabilitation, and the establishment of viable populations The question of adequate habitat is the most critical aspect determining the future of the Chinese alligator. The long-term survival of alligators outside of the breeding centers and zoos will rest on the establishment of protected sites of sufficient size to support viable populations and meet their ecological needs. The designated sites in the NCAR are inadequate to insure the long-term viability of wild Chinese alligator populations. Providing adequate habitat will require either improving the existing sites (both in terms of habitat quantity and quality), or locating new areas that would be more easily restored or that currently offer adequate alligator habitat. In this regard, the conservation of wild alligators would best be made a part of wetland protection and restoration efforts in Anhui and other areas within the historical distribution of the species. Ideally, this would include the establishment of wetlands reserves where alligators, and other native wildlife, can be protected together. Alternatively, small wetlands reserves can be established specifically for alligators, either within the NCAR or in other areas where remnant habitat patches remain or can be restored. Nevertheless, agricultural land use pressures on all potential sites are intense, and efforts to establish wetland reserves for wildlife will require the active involvement of local communities and land-use planners as part of a process to improve the quality of life for the farmers that depend on the lands in question. Additionally, there are other vital issues that need to be addressed, particularly those related to genetic and health-related considerations as a result of the small size of the existing groups and the consideration of options for reintroducing alligators into new areas using captive reared animals from ARCCAR. The current management of wild Chinese alligators protects the animals themselves, but not their habitat. However, at present, the Chinese government is developing plans for a more comprehensive management approach (Wan et al., 1998). While the plan does not present many details, or a timetable for implementing its objectives, it represents an important first step towards the development of a strategy for the long-term conservation of alligators in the wild.
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5. Conclusions The current status of the Chinese alligator is an amalgam of contradictions. There is a large declared reserve, but natural habitat is virtually non-existent. The wild population is tiny and highly fragmented, but a large number (>7000) of captive animals exist in China and to a lesser degree in zoos outside the country. What is clear, however, is that the Chinese alligator, as one of the last vestiges of a formerly diverse lower Changjiang megafauna, is poised to become extinct in the wild in the next few decades. Most remaining wild alligators exist as small groups or single individuals lost in an agricultural landscape. Natural reproduction appears to be limited to four sites at present. Areas where Chinese alligators were found were highly altered and marginal or unsuitable in terms of habitat quality and quantity. Even if the wild nests hatched, the prospects for survival of hatchling alligators at these sites are low, and efforts to increase the survivorship of hatchlings will only provide limited benefits due to the physical limits in size of the existing sites. However, even the positive aspects of this dismal assessment are moot as wild nests are collected and incubated at ARCCAR, and the young remain in captivity. The few surviving alligators are now in a downward spiral, succumbing to human population pressures by being unintentionally poisoned, shot or killed by fishermen. Our survey indicated that given the current management of the NCAR, there is little medium- or long-term future for alligators in the wild. The future of Chinese alligators in the wild will rest on efforts to rehabilitate areas of adequate habitat, and the establishment of viable populations at these sites by releasing captivereared alligators.
Acknowledgements We were hosted by the Anhui Provincial Government, and the following people: Mr. Kui Chu Shi, Director, Anhui Provincial Natural Protection and Management Agency; Mr. Gu Chang Ming, Anhui Provincial Natural Protection and Management Agency, Mr. Xie Wan-Shu, Director, Anhui Research Center of Chinese Alligator Reproduction, Mr. Wang Chao Lin, ViceDirector, ARCCAR. Professor Sheng Helin assisted us on our initial visit to Anhui, and in Shanghai Endi Zhang provided considerable support. George Schaller provided advice as well as a vehicle. Professor Chen Bihui generously shared his knowledge of Chinese alligators with us. We are grateful to our driver Xu Jun for his skill. Funding for the survey was provided by the Walt Disney Company Foundation and the Wildlife Conservation Society.
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References Chen, B., 1985. Chinese Alligator. Anhui Science and Technology Press, Hefei, Anhui, PRC (in Chinese). Chen, B.C., 1990. The past and present situation of the Chinese alligator. Asiatic Herpetological Research 3, 129–136. Chen, J., Chen, K., 1997. The conservation status of wetlands in China and their future prospects. In: Prentice, R.C., Jaensch, R.P. (Eds.), Development Policies, Plans and Wetlands. Proceedings of Workshop 1 of the International Conference on Wetlands and Development. Wetlands International, Kuala Lumpur, pp. 117–126. Fu, J. 1994. Conservation, management and farming of crocodiles in China. In Crocodiles. Proceedings of the 2nd Regional (Eastern Asia, Oceania, Australasia) Meeting of the Crocodile Specialist Group. IUCN—The World Conservation Union, Gland, Switzerland. Groombridge, B., 1982. Amphibia—Reptilia Red Data Book. Part 1. Testudines, Crocodilia and Rhynchocephilia. IUCN, Gland, Switzerland. Hsiao, S.D., 1934. Natural history notes the Yangtze alligator. Peking Natural History Bulletin 9, 283–293. Huang, C. 1982. The ecology of the Chinese alligator and changes in its geographical distribution. In: Crocodiles. Proceedings of the 5th Working Meeting of the IUCN/SSC Crocodile Specialist Group, Gainesville, FL, pp. 54–62. Huang, Z., 1981. The Chinese alligator. Oryx 16, 139–140. Huang, Z., Lin, H., Zhang, S., 1985. An analysis of the remote sensing image of the Chinese alligator habitat. Oceanologica et Limnologica Sinica 16, 35–42 (in Chinese with English summary). Huang, M., Jin, Y., Cai, C., 1987. Fauna of Zhejiang. Zhejiang
Science and Technology Publishing House, Hangzhou, China (in Chinese). Li, C., Shao, M., Zhu, H., Nie, J., 1996. Current status of Alligator sinensis. Chinese Biodiversity 4, 83–86 (in Chinese with English summary). People’s Republic of China, 1992. Registration of the Anhui Research Centre of Chinese Alligator Reproduction for Alligator sinensis. Proposal to CITES, Kyoto, Japan. Scott, D.A. (Compiler), 1989. A directory of Asian wetlands. IUCN, The World Conservation Union, Gland, Switzerland. Thorbjarnarson, J., Wang, X., 1999. The conservation status of the Chinese alligator. Oryx 33, 152–159. Wan, Z., Gu, C., Wang, X., Wang, C. 1998. Conservation, management and farming of crocodiles in China. In: Crocodiles. Proceedings of the 14th Working Meeting of the Crocodile Specialist Group. IUCN—The World Conservation Union, Gland, Switzerland and Cambridge, UK, pp. 80–100. Watanabe, M.E., 1982. The Chinese alligator: is farming the last hope? Oryx 17, 176–181. Webb, G.J.W., Vernon, B., 1992. Crocodilian management in the People’s Republic of China—a review with recommendations. In: Ross, J.P. (Ed.), Crocodile Conservation Action. A Special Publication of the Crocodile Specialist Group of the Species Survival Commission of the IUCN—The World Conservation Union. Gland, Switzerland. IUCN—The World Conservation Union, Gland, Switzerland, pp. 1–27. Zhou, Y.J., 1997. Analysis of the decline of the wild Alligator sinensis population. Sichuan Journal of Zoology 16, 137 (in Chinese). Zhu, H.X., 1997. Observations on a wild population of Alligator sinensis. Sichuan Journal of Zoology 16, 40–41 (in Chinese).
Wild Populations of the Chinese alligator approach extinction John Thorbjarnarsona,*, Xiaoming Wangb, Shao Mingc, Lijun Heb, Youzhong Dingb, Yuelong Wud, Scott T. McMurrye a Wildlife Conservation Society, 2300 Southern Blvd, Bronx, NY 10460 USA Department of Biology, East China Normal University, 3663 Zhong Shan Road, Shanghai 200062, China c Anhui Research Center of Chinese Alligator Reproduction, Xuanzhou, Anhui 242034, China d Anhui Forestry Bureau, 47 Wuwei Road, Heifei, Anhui 230001, China e The Institute of Environmental and Human Health, Reese Center, Texas Tech University, 1207 Gilbert Drive, Lubbock, TX 79416, USA b
Received 6 June 2000; received in revised form 28 January 2001; accepted 2 May 2001
Abstract The Chinese alligator, Alligator sinensis, is on the verge of becoming extinct in the wild as a result of loss of natural wetlands in the lower Changjiang valley. Chinese alligators are only known from a small region in southeastern Anhui province, a fraction of its former distribution. Within this area, a 433 km2 reserve has been declared that contains 13 designated habitat sites totaling 41 ha. The sites consist of small ponds located within or adjacent to villages, are completely surrounded by rice fields, or are biologically marginal oligotrophic ponds set in low hills. Alligators are only present at 10 of the 13 designated sites, with the largest groups containing a maximum of 10–11 animals and one adult female. In recent years nesting is known from only four areas, but the eggs are routinely collected and hatchlings retained in the Anhui alligator breeding center. The total population of wild Chinese alligators is probably < 130 and is declining at an annual rate of 4–6%. If present trends continue, the Chinese alligator will be the first species of crocodilian to become extinct in the wild in historical times. Conservation efforts need to focus on protection of remaining wetlands and wetland restoration, and the inclusion of Chinese alligators in the active management of protected wetlands sites throughout the species’ historic distribution. # 2001 Elsevier Science Ltd. All rights reserved. Keywords: Chinese alligator; Conservation; Status; Extinction; China; Alligator sinensis
1. Introduction The Chinese alligator, Alligator sinensis, locally referred to as Yang Zi E (Yangtze alligator) or Tu Long (earth, or muddy dragon), is a small crocodilian that has a rich tradition of cultural symbolism in China. Historically, the Chinese alligator was distributed over a wide geographic area in the lower Changjiang (also known as the Yangtze) river system in southeastern China (Huang, 1982; Chen, 1985). The lower reaches of the Changjiang formerly hosted a spectacular array of lakes, marshes and seasonally flooded wetlands. However, this was one of the first areas where humankind developed rice cultivation, some 7000 years ago, and intensive agricultural development has taken a tremendous toll on the region’s low-elevation habitats * Corresponding author. Tel. +1-718-220-4069; fax: +1-718-3644275. E-mail address: [email protected] (J. Thorbjarnarson).
(Scott, 1989). By the late nineteenth and early twentieth centuries, alligators had disappeared from most of their former range and were restricted to a few marshy regions along the lower course of the Changjiang (Huang, 1987; Chen, 1990; Thorbjarnarson and Wang, 1999). Throughout the twentieth century, Chinese alligator populations continued to decline and their range shrink. By the 1950s, alligators were only found along the southern bank of the Changjiang extending from Pengze (Jiangxi Province) to the western shore of the Taihu lake and south to the foothills of the mountainous regions of southern Anhui (Huangshan mountains; Huang, 1981; Chen, 1990), and adjacent sections of Jiangsu and Zhejiang provinces. At this time Chinese alligators were still found in lakes, some streams and marshes in lowland regions along the Changjiang, and in small ponds in low hills (Huang, 1981). By the 1970s, the species’ range was even further restricted to a small region in southern Anhui and neighboring Zhejiang
0006-3207/01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved. PII: S0006-3207(01)00128-8
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Province. Huang (1981) notes that during this time alligators were less frequently found in the typical habitat of low-elevation marshy wetlands, which had been almost completely transformed into rice paddies, and were increasingly restricted to small ponds in hills where agriculture, and human disturbance, was less intense. In 1972 the Chinese government listed the Chinese alligator as a Class I endangered species, providing it the highest degree of legal protection (Wan et al., 1998). Enforcement of regulations prohibiting the capture or killing of wild alligators, however, was not entirely effective, particularly during the 1970s and early 1980s (Watanabe, 1982). Since 1979, Chinese alligator management focused on captive breeding, and centers were established in Anhui and Zhejiang provinces (Wan et al., 1998). The Anhui Research Center for Chinese Alligator Reproduction (ARCCAR) is the largest facility housing >7000 Chinese alligators and serving as the administrative center for alligator management in Anhui Province. A 433-km2 reserve for Chinese alligators was created in the mid-1980s, encompassing a fivecounty region that contained virtually all the remaining areas with wild Chinese alligators. However, little information is available on the status of the last remaining groups of alligators in this area over the last 25 years (Thorbjarnarson and Wang, 1999). Here we present the results of a 1999 survey of the wild population of Chinese alligators. We examine recent evidence of population decline, the current status of the wild population, and the reasons for population decline.
2. Methods Field surveys were conducted from July through October 1999 at 26 sites within the five county region of the National Chinese Alligator Reserve (NCAR), including all 13 sites officially designated by the Chinese government for the protection of the Chinese alligator (here referred to as ‘‘designated sites’’; Fig. 1). At each site we mapped the ponds using a laser rangefinder and compass, characterized the physical nature of the ponds and vegetation, and conducted interviews with local residents. At most of the 13 designated sites the Anhui Forestry Bureau (AFB) employed a local farmer as a caretaker to oversee the protection of the Chinese alligators. The caretaker and other local farmers were good sources of information regarding the number of alligators, the locations of their burrows, recent nesting, and the history of habitat modification in the region. At these sites we estimated the number of alligators based on (1) nocturnal spotlight counts and (2) information provided by the local alligator caretaker and other farmers. Chinese alligators are extremely wary
and difficult to observe, so we used the number of individuals seen as an estimate of minimum population size. The number of alligators estimated by the local caretakers and farmers were generally consistent and based on observations made during their frequent work around the ponds. These observations were made over a period of many years and we feel represent a potential maximum number of alligators at each site. Residents were also questioned concerning alligator nesting and the location of nest sites. We conducted nocturnal spotlight counts only if there was evidence that Chinese alligators were present within the last three years at a particular site. These counts were initiated shortly after dark (ca. 20:00) and typically were completed before 23:00 due to the small size of most areas. We located alligators by their reflected eyeshine using headlamps or a 12-V portable spotlight. Nocturnal surveys were conducted by either walking around the perimeter of ponds, using locally available wooden boats (two sites: Hongxin, Yantang), or a two-person inflatable rubber boat. When sighted, we approached alligators as closely as possible to estimate total length (TL) in 50-cm size-class categories. The sites we surveyed represent the largest known remaining groups of alligators. In other parts of the NCAR, farmers occasionally reported the presence of individual alligators to the local AFB office. Based on these reports, and a questionnaire survey completed by the AFB in 1998, the county forestry departments were able to estimate the number of alligators in areas we did not visit. Recent alligator population trends were determined by comparing the results of our survey with information on past nesting and previous estimates of alligator population size for individual counties and sites.
3. Results 3.1. Population size Chinese alligators were observed at seven of the 13 designated sites, and we counted a total of 20 individuals at these sites (Table 1). Based on information from local caretakers and farmers, Chinese alligators had been extirpated at three of the 13 sites and the maximum number of alligators in the other 10 designated sites was estimated to be 60. In addition to the designated sites, we visited 13 other sites where the AFB believed Chinese alligators might persist. In these areas, we observed Chinese alligators at two sites, and counted a total of three individuals. Estimates from AFB staff and local farmers suggest that a maximum of 15 alligators remain at six of these sites. Overall, we found recent evidence (confirmed sightings,
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active burrows, nests) of Chinese alligators at 16 of 26 sites. We counted 23 Chinese alligators at nine sites, but information from AFB and local residents suggests there may be as many as 75 alligators present at the 16 sites (Table 1). Remaining groups of Chinese alligators contained few individuals. Four of the surveyed sites had one alligator (Table 1). The largest remaining groups had a maximum of 10–11 animals, and this was the case at four sites. We classified the size of 18 of the 23 alligators seen (Fig. 2). The size-class distribution indicated a preponderance of adult alligators and a scarcity of juveniles. The smallest animals observed were 70–80 cm TL juveniles seen at two sites. Based on reports from farmers and the results of a 1998 questionnaire survey of the NCAR, the AFB estimated that there may be as many as 55 Chinese alligators outside of the areas we surveyed (Jinxiang-10; Xuancheng—20; Guangde—5; Nanling—10; Langxi— 10). In all cases these were believed to be isolated individual alligators. Based on a maximum of 75 Chinese alligators at the 26 sites surveyed, and 55 isolated individuals at other sites, we estimate that the total number of Chinese alligators in the NCAR does not exceed 130 individuals. This represents the entire wild population as there are
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no known groups of wild Chinese alligators outside the NCAR. 3.2. Nesting and reproductive potential of the wild population Four Chinese alligator nests were found in 1999. We located nests at the Shaungken and Zhongqiao designated sites (the eggs of which were collected and taken to ARCCAR), and at Zhuangtou. Subsequently, ARCCAR reported another nest was located and collected at Yishan village in Xuancheng county. Eggs in the Zhuangtou nest were left in situ but failed to hatch. Only two of the designated sites had evidence of successful reproduction within the last 5 years, as indicated by the presence of juveniles (Table 1). 3.3. Recent alligator mortality In the NCAR, recent mortality of Chinese alligators or their emigration from designated sites was due to a variety of causes (Table 2). The accidental killing of Chinese alligators, while infrequent, is probably a significant source of mortality given the small size of the wild population. Alligators that emigrate from these sites enter areas of less suitable habitat, for example rice
Fig. 1. Location of the 13 designated Chinese alligator habitat sites in the National Chinese Alligator Reserve. Each site is identified by letter as represented in Table 1. Other sites where alligators have been reported in the last 3 years are indicated with asterisks. The location of the ARCCAR breeding center is indicated with a BC, and the Zhaungtou site is marked with ZT.
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fields or other modified landscapes and presumably end up as displaced, isolated individuals. Flooding and drought are significant factors that contribute to alligator mortality or emigration. At two sites the last known adult females died as a result of ingesting rodents poisoned in nearby fields and houses and thrown into the ponds. 3.4. Recent population trends County and site-specific information suggests that the small wild population continues to decline. AFB records from Langxi county illustrate decline in the number of villages from which Chinese alligators were reported (Fig. 3). While the number of Chinese alligators reported at each of these villages is unknown, the shrinking area from which they are reported provides evidence of population decline. Today, alligators are known from
only one site in Langxi county (Zhangcun). The average annual loss of villages in Langxi county reporting alligators from 1975 to 1999 was 4%. The AFB surveyed 66 villages for Chinese alligators in Nanling county in 1986. At that time, 193 alligators were estimated to be present in 23 villages. However, the number has subsequently declined precipitously (Fig. 4). In 1998 the AFB estimated the Chinese alligator population in Nanling county to be 32 animals in nine villages. The average annual decline (1986–1998) was 6.4% for the number of alligators, and 5.4% for the number of villages reporting Chinese alligators. Some information also exists for Chinese alligator population trends from specific sites between 1981 (Huang et al., 1985) and 1999 (our surveys; Table 3). The overall decline of 84% between 1981 and 1999 indicates an annual average loss of 4.7%. At the Hongxin site, in Xuancheng county, data from Zhu (1997)
Table 1 Summary of 1999 survey resultsa County
Site Site code
Jinxiang
E F D *
Shaungken Zhongqiao Yantang Liang Zhong Lin Zhi Ma’an
1.71 3.37 2.53 1.07 0.81 0.84
6 5 1 3 1 2
Yes Yes Yes No No No
3 1 0 0 0 0
No No No No No No
10 4 1 0 0 0
1999 1999 1992 1970s
1 3 1 1 1 1
0.285 0.674 2.530 0.357 0.810 0.420
5.85 1.19 0.40 0.00 0.00 0.00
Xuancheng
H * G ZT
Yanlin Maogia Hongxin Zhuangtou Li Yun Miao
0.36 1.25 8.44 6.08 0.67
2 2 1 7 1
Yes No Yes No No
0 0 4 2 0
No No No No No
1 3 10 5 1
1970s 1997 1996 1999 1991
2 3 2 3 2
0.180 0.625 8.440 0.869 0.670
2.78 2.40 1.18 0.82 1.49
Guangde
M L
Zhucun Jiagu Qian Mou Yuan
2.76 1.22 –
1 3 1
Yes Yes No
3 0 0
Yes Noc No
5 2 0
1997 1998
2 3 1
2.760 0.407
1.81 1.64
Nanling
B A C *
Changle Xifeng Zhalin Heyi Liu Dian Shangma Tian Guan Song Cun
0.28 2.83 2.08 2.11 – 2.20 1.67 0.39
3 1 1 2 1 1 1 3
Yes Yes Yes No No No No No
5 0 3 1 0 0 0 0
yes no no no no no no no
11 0 5 3 0 0 1 2
1996 1980s 1993 1970s 1970s
1 3 3 1 1 3 2 1
0.093 2.830 2.080 1.055
39.29 0.00 2.40 1.42
2.200 1.670 0.130
0.00 0.60 5.13
Wang Jiameu Huang Shugang Zhangcun Yuan Cun
7.64 5.35 2.29 0.50
1 4 2 1
Yes Yes Yes No
0 0 1 0
no no no no
0 0 11 0
1950s 2 1983 1 1996 1 2
7.640 1.338 1.145 0.500
0.00 0.00 4.80 0.00
Langxi
Designated sites All sites a
I K J
40.86
Pond area No. Protected? Total Juveniles Estimated Last (ha) ponds seen number nest
31 58.45
20 57
60 23
Habitat Average Population typeb pond size density (ha)
1.318 75
1.47 1.654
1.28
Sites that are not officially designated are in italics. Site codes refer to Fig. 5. Population density (alligators/ha) calculated using estimated (maximum) population values. b Habitat types are defined in the text. c There were unconfirmed reports of yearling alligators from Jiagu.
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provided evidence of reduction in the number of Chinese alligators over a 4-year period. At this site annual nesting ceased in 1996 and the last known adult female was found dead in 1999. The dates of last known nesting at each of 17 sites visited during our 1999 survey provides evidence for a decline in population reproductive output (Table 1). While in some cases these were imprecise descriptions (e.g. the 1960s), at most sites there was a good record of when the last eggs were laid (Fig. 5). Ominously, the decline has been particularly rapid since the mid-1990s and, for the first time ever, there were no wild nests reported in 1998 (with the possible exception of an unconfirmed report from Jiagu). Only one confirmed report of Chinese alligators outside the NCAR has come in recent years. In 1995, a large male (1.99 m TL) was captured and later released in Ma’anshan County in eastern Anhui along the Changjiang (Fig. 1). However, this was likely a transient animal that had been washed down one of the rivers from the NCAR during flooding. There have been no subsequent reports of alligators in this region.
Fig. 2. Size-class distribution of 18 Chinese alligators observed in the wild.
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3.5. Current status of habitat in the NCAR Although the designated sites are probably the best remaining areas for Chinese alligators, the total pond area was small (41 ha in 31 ponds), and the only area considered protected is the pond, or ponds, and not any surrounding land. The cultivation of rice and other crops frequently extends to the very edge of ponds. In many cases, there is no fringe of vegetation between the water and the cultivated fields, and at several sites (Zhongqiao, Zhucun, Yantang and Hongxin), shallow water sections of the ponds had been diked and reclaimed for rice paddies. At other sites (e.g. Shaungken, Yantang), recent construction of dikes or water control structures significantly altered the hydrology at the sites, making them less favorable to aquatic wildlife. The ponds themselves are very small, with a mean size of 1.32 ha, and at some sites mean pond size was as small as 0.09 ha (Changle). The largest pond was the 8.4 ha reservoir at Hongxin. The total size of ponds at 24 of the 26 visited sites (the two others were sections of rivers where it was impossible to delimit an area) was 58.5 ha (total of 55 ponds). In many cases, farm houses were located along the edge of the pond, and in other cases ponds are located in the midst of villages. Although
Fig. 3. Number of villages in Langxi county where Chinese alligators were reported present from 1975 to 1999. Data from Langxi office of the Anhui Forestry Bureau.
Table 2 Reports of recent sources of alligator mortality or emigration in the National Chinese Alligator Reserve Site
Reported source of mortality or emigration and year
Shaungken Zhongqiao Yantang Yantang Liang Zhong Hongxin Zhaungtou Zhucun Changle Xifeng Heyi Huang Shugang
Construction of dike and loss of part of available habitat—1991 Hatchlings dying during winter from lack of a burrow—1989–1992 Accidental shooting of last adult female while rabbit hunting—1995 Change in stream hydrology resulting in lower water temperature, increased current and more variable water level—1992 Pond drying up—1997 Last adult female died eating poisoned rodents—1999; egg collection—prior to 1996 Egg collection—1996, 1997 Juvenile accidentally killed by eel fishermen—1998 Last adult female died eating poisoned rodents—1998 Dam broke, pond emptied out—1991 Floods—1999 Floods—1983
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ponds at the designated sites are protected, water in the ponds remains under the control of the surrounding community, and is used to irrigate farmland during periods of drought, for buffalo wallows, fish farms, or rearing ducks. Under these conditions, conflicts between people and alligators are inevitable. Burrowing even a small distance into the shores of ponds will take alligators into agriculture fields, and alligator movements between ponds damages rice plants. To better understand the current distribution of alligators in the NCAR, we categorized habitats into three main types: Type 1. Relictual wetlands in low, broad, fertile valleys along principal river courses. Areas dominated by agriculture, principally rice. Type 2. Intermediate; ponds in low hill valleys (< 100 m altitude) but with significant agriculture in the valley above the pond.
Type 3. Ponds situated in low hill valleys (< 100 m altitude) at the upper edge of rice cultivation and the lower edge of tree plantations. Type 1 habitat represents the closest approximation to what was historically good alligator habitat: low elevation, alluvial floodplains containing a variety of wetlands including marshes, ponds and streams. Today, these areas have been heavily settled and the wetlands have either disappeared or been highly altered. The major rivers have levees along their banks and natural floodplains no longer exist. The principal stream tributaries of rivers have been diked and divided to form ponds which are ringed with agricultural fields and villages. Shallow ponds and marshes have been converted into rice paddies. The few type 1 habitats with alligators represent tiny remnants of formerly extensive natural wetlands. They typically are groups of small ponds (mean 2.9 ponds per site, average pond size 0.6 ha) in the midst of agricultural settlements. Nevertheless, despite their small size and the intense human use, these areas support half Table 3 Population decline of alligators at four sites where population size was estimated in 1981 and 1999a
Fig. 4. Trend in the number of number of villages reporting Chinese alligators, and the number of alligators observed and estimated present in Nanling county since 1986. Data from the Nanling Forestry Department.
Site
1981 Estimate
1999 Estimate
% Decline
Yantang Shipu Yanlin Heyi
3 4 3 22
1 0b 1 3
67 100 67 86
Total
32
5
84
a
1981 values from Huang et al., 1985. Nanling Forestry Department staff report that alligators have disappeared from the Shipu site. b
Fig. 5. Number of sites reporting alligator nests by year. Data for 17 sites visited during 1999 survey. Based on a starting point of 1955, the overall decline has been 82.4% over 44 years ( 1.8% per year).
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of the known wild alligator population (Table 1). Soils in these areas were richly organic and many of the sites had significant shallow water habitat and aquatic vegetation, both rooted and floating. At these sites we readily observed natural alligator prey (aquatic insects, crustaceans, snails, frogs, eels). Type 3 ponds offered reduced human land-use pressures but marginal alligator habitat. These sites were characterized by clearwater (oligotrophic) ponds with little aquatic vegetation or natural, shallow-water habitat. Like type 1 areas, these sites typically have multiple, small ponds (mean 2.86 ponds/site, average size 0.95 ha), but are located in hilly, partly forested terrain on rocky soil with high clay content that makes burrowing difficult. While adult alligators can survive in these ponds, they represent poor or marginal habitat. At one type 3 site (Zhalin) that was used as a release site for alligators from other areas, we were told many of the alligators left the pond and were recaptured in rice paddies further down the valley. Type 3 ponds may be less suitable for juveniles alligators than for adults, and the overall density of alligators is only half that of the type 1 sites. Despite the fact that two of the three areas where nesting is taking place fall into this category, we found no evidence for juvenile alligators at any type 3 habitat. Type 2 habitats ranged from small ponds in rice fields to medium-sized ponds in rolling hills surrounded by dry-ground agriculture. The two largest designated sites are type 2 habitats (Hongxin and Wang Jiameu), and principally for this reason the mean pond size of type 2 habitats was more than twice that of type 3 sites (mean 1.14 ponds/site, average pond size 2.76 ha). Because of the size of these two ponds, plus the relatively large size of the Zhucun site, type 2 habitats had nearly half of the surface area of protected ponds, but only about one quarter of the estimated alligator population. Hongxin offers what is perhaps the best chance for undertaking habitat improvements with the goal of maintaining a wild group of alligators. The other large type 2 site (Wang Jiameu), however, is one of the designated sites without alligators or adequate habitat.
4. Discussion 4.1. Population size and distribution trends In southern Anhui Province, alligators have probably persisted longer than in neighboring provinces as a result of the more recent initiation of agriculture in some marginal areas, a lower overall human population density and the prevalence of low hills with ponds (type 3 habitats) that offer a last refuge for alligators. Nevertheless, the number of alligators in Anhui declined
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sharply between the 1950s and the 1970s. Of 29 regions where alligators were relatively common in the 1950s, they were easily seen in only four by 1976, and had disappeared completely from nine (Chen in Fu, 1994). Huang (1981) reported that between 1956 and 1976, the number of known alligators in 11 counties in Anhui and neighboring provinces had declined from 360 to 120, an average annual decline of 3.3%. By the late 1980s, wild Chinese alligators remained only in Anhui Province, principally in small ponds in agricultural valleys and hills in five counties (Nanling, Jinxiang, Guangde, Langxi, Xuancheng), which together comprise the NCAR. Outside the NCAR, including all the sites where alligators were previously found bordering the Changjiang (Wuhu, Ningguo and Dongtu counties), ARCCAR staff report alligators were extirpated during the last 20 years. In the early 1980s, surveys in Anhui Province estimated the wild population of alligators was at least 300 individuals, comprised mostly of juveniles or subadults (Watanabe, cited in Groombridge, 1982). Based on these and other surveys, Chen Bihui calculated that approximately 500 alligators remained in the wild during this period (People’s Republic of China, 1992; Webb and Vernon, 1992). Another, more extensive survey of 129 villages (423 bodies of water) in the NCAR was organized by ARCCAR in 1985 and 1987, and estimated the number of wild alligators was 735 (People’s Republic of China, 1992). Based on this population estimate, and the fact that between 1979 and 1983 212 alligators were collected from the wild to stock the ARCCAR breeding center, it is not unlikely that approximately 1000 wild Chinese alligators were living in Anhui Province during the late 1970s. In 1994, staff from ARCCAR observed 77 Chinese alligators during spotlight counts in the NCAR (Li et al., 1996). From these counts the total alligator population in the surveyed areas was estimated to be 253, and extrapolating to the entire five-county region, the total number of remaining wild Chinese alligators was calculated to be 667–740 (Li et al., 1996). Their estimate was based on the assumption that only one third of the sites within the reserve were surveyed. But because all the principal locations actually known to have Chinese alligators were visited, the validity of this extrapolation is questionable and the total wild population was most likely considerably less than reported. Zhou (1997) provided population estimates of 378– 747 for the NCAR from 1985 to 1994. However, it is unclear how these population estimates were made. Wan et al. (1998) indicated that in 1997, the population of wild alligators was reduced to approximately 400, but no details were provided. While these survey results are hard to interpret because of a lack of information on where and how they were conducted, most current evidence suggests the total number of wild Chinese alligators declined from
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approximately 1000 wild alligators in the late 1970s to the current estimate of 5130. 4.2. Factors responsible for population decline Chinese alligators are rarely tolerated by local farmers in the lower Changjiang valley. Alligators prey on small livestock (particularly ducks), and their burrows interfere with water control structures vital for rice cultivation. Many farmers believe alligators reduce the number of fish in ponds. Hsiao (1934) stated that when ‘‘convenient’’ alligators were killed by farmers for food, but other accounts suggest that during most of the nineteenth and twentieth centuries people did not eat alligators. Nevertheless, B. Chen (personal communication) reported that after 1986, people in Anhui began eating alligator believing it was dragon meat. Although the sale of captive alligator meat from ARCCAR was approved at two restaurants, one in Xuancheng (near the ARCCAR) and one in Beijing, an illegal market emerged, and in recent years there were at least two cases of people catching and selling live alligators. The collection of live alligators, principally for zoos, has also played a significant role in the demise of wild populations (Thorbjarnarson and Wang, 1999). Wetland loss is a widespread problem throughout China, and in view of the rapid economic development of the country, this problem will continue, or even be exacerbated, in the near future (Chen and Chen, 1997) The disappearance of wetland has been particularly severe in the middle and lower Changjiang region, and this has had disastrous impacts on native wildlife. From the late sixteenth to the early twentieth century (Qing Dynasty), there was a large migration of people from the north into the lowland Changjiang region (Huang, 1982; Chen, 1990), converting the river’s floodplain into agricultural fields. However, during this period some lands were set aside as cattle ranches for the Manchu Mandarins, and in these regions of natural marshland farming was prohibited, creating de facto habitat reserves for alligators and other marsh wildlife. The Changjiang floodplain to the south of Wuhu, one of the last strongholds of the species until the mid-twentieth century, was one of these areas (Chen, 1990). Loss of wetlands continued into modern times, and today virtually the entire area is under cultivation (Watanabe, 1982). Many areas where alligators now occur are small ponds created in the late 1950s and early 1960s, during the ‘‘Great Leap Forward’’ with its emphasis on increasing rural agriculture. The use of chemicals to control the snail vectors of schistosomaiasis, and the application of large amounts of chemical fertilizers and insecticides may also affect the Chinese alligator (Chen, 1990, Thorbjarnarson and Wang, 1999). During our surveys we found clear evidence that alligators were dying from eating poisoned
rodents. Zhou (1997) reported that in 1984 two alligators died from the effects of insecticides in a farm in Jinxiang county. Increased drought and flooding that result from loss of natural vegetation throughout eastern China have also led to significant mortality of alligators (Watanabe, 1982; Zhou, 1997) or forced animals to move overland where they are captured or killed (Chen, 1990). The last individuals at Liang Zhong in Jinxiang county reportedly left the area during the drought of 1997. At the Hong Shugang (Langxi county) designated site alligators were regularly seen until the floods of 1983, when many were dispersed into the surrounding floodplain or downstream in the Langchuan river. 4.3. Factors determining the current distribution of alligators in the NCAR The nature of the existing habitats in the NCAR place severe limitations on the survival of wild alligators. While the reserve is large (433 km2), it encompasses a mixed agricultural–urban landscape with more than 2 million people (Thorbjarnarson and Wang, 1999). Ponds in the low valleys (habitat type 1 and most type 2) offer habitats favored by alligators, but intense conflicts with people. The persistence of alligators in these rich agricultural regions is due to the fact that the they are relatively innocuous and cryptic, and also because they are long-lived, so even if breeding groups no longer exist, isolated individuals may remain for many years. However, there are also a variety of site-specific habitat factors that appear to explain why alligators are found in certain areas and not in others. The agricultural and land-use history of the site is certainly a factor. In other cases, the presence of alligators is merely a reflection of the fact that the site has been used to release animals found in rice paddies or other inappropriate locations. At other sites, the prolonged existence of alligators is a result of specific habitat factors which buffer the alligators from intense human population pressures. At some sites alligators may have been able to persist because of a complex assemblage of former floodplain streams, now divided into numerous small ponds, provide a number of refuges. However, in most sites the survival of alligators appears to be related largely to the availability of relatively undisturbed areas for nesting. In some locations, the stream or pond habitat used by the alligators is bordered on one side by a partially forested, and relatively unused, hillside that provides nesting habitat. In other areas, small islands fulfill the same role. In type 3 habitats, ponds are usually surrounded by little used hillsides with scrub vegetation or pine plantations that offer nesting habitat. However, because of the small size of nearly all the remaining sites, and the intensity of the human population pressures that surround them, these
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factors have, at best, merely determined which are the last areas from which wild alligators will be extirpated. At one type 3 site (Zhalin), despite being surrounded by largely forested hillsides, having a small island that was used (until 1993) for nesting, and being the principal release site for alligators found in Nanling county, the estimated alligator population numbers only five individuals. 4.4. Management alternatives: habitat protection, rehabilitation, and the establishment of viable populations The question of adequate habitat is the most critical aspect determining the future of the Chinese alligator. The long-term survival of alligators outside of the breeding centers and zoos will rest on the establishment of protected sites of sufficient size to support viable populations and meet their ecological needs. The designated sites in the NCAR are inadequate to insure the long-term viability of wild Chinese alligator populations. Providing adequate habitat will require either improving the existing sites (both in terms of habitat quantity and quality), or locating new areas that would be more easily restored or that currently offer adequate alligator habitat. In this regard, the conservation of wild alligators would best be made a part of wetland protection and restoration efforts in Anhui and other areas within the historical distribution of the species. Ideally, this would include the establishment of wetlands reserves where alligators, and other native wildlife, can be protected together. Alternatively, small wetlands reserves can be established specifically for alligators, either within the NCAR or in other areas where remnant habitat patches remain or can be restored. Nevertheless, agricultural land use pressures on all potential sites are intense, and efforts to establish wetland reserves for wildlife will require the active involvement of local communities and land-use planners as part of a process to improve the quality of life for the farmers that depend on the lands in question. Additionally, there are other vital issues that need to be addressed, particularly those related to genetic and health-related considerations as a result of the small size of the existing groups and the consideration of options for reintroducing alligators into new areas using captive reared animals from ARCCAR. The current management of wild Chinese alligators protects the animals themselves, but not their habitat. However, at present, the Chinese government is developing plans for a more comprehensive management approach (Wan et al., 1998). While the plan does not present many details, or a timetable for implementing its objectives, it represents an important first step towards the development of a strategy for the long-term conservation of alligators in the wild.
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5. Conclusions The current status of the Chinese alligator is an amalgam of contradictions. There is a large declared reserve, but natural habitat is virtually non-existent. The wild population is tiny and highly fragmented, but a large number (>7000) of captive animals exist in China and to a lesser degree in zoos outside the country. What is clear, however, is that the Chinese alligator, as one of the last vestiges of a formerly diverse lower Changjiang megafauna, is poised to become extinct in the wild in the next few decades. Most remaining wild alligators exist as small groups or single individuals lost in an agricultural landscape. Natural reproduction appears to be limited to four sites at present. Areas where Chinese alligators were found were highly altered and marginal or unsuitable in terms of habitat quality and quantity. Even if the wild nests hatched, the prospects for survival of hatchling alligators at these sites are low, and efforts to increase the survivorship of hatchlings will only provide limited benefits due to the physical limits in size of the existing sites. However, even the positive aspects of this dismal assessment are moot as wild nests are collected and incubated at ARCCAR, and the young remain in captivity. The few surviving alligators are now in a downward spiral, succumbing to human population pressures by being unintentionally poisoned, shot or killed by fishermen. Our survey indicated that given the current management of the NCAR, there is little medium- or long-term future for alligators in the wild. The future of Chinese alligators in the wild will rest on efforts to rehabilitate areas of adequate habitat, and the establishment of viable populations at these sites by releasing captivereared alligators.
Acknowledgements We were hosted by the Anhui Provincial Government, and the following people: Mr. Kui Chu Shi, Director, Anhui Provincial Natural Protection and Management Agency; Mr. Gu Chang Ming, Anhui Provincial Natural Protection and Management Agency, Mr. Xie Wan-Shu, Director, Anhui Research Center of Chinese Alligator Reproduction, Mr. Wang Chao Lin, ViceDirector, ARCCAR. Professor Sheng Helin assisted us on our initial visit to Anhui, and in Shanghai Endi Zhang provided considerable support. George Schaller provided advice as well as a vehicle. Professor Chen Bihui generously shared his knowledge of Chinese alligators with us. We are grateful to our driver Xu Jun for his skill. Funding for the survey was provided by the Walt Disney Company Foundation and the Wildlife Conservation Society.
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