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Extinct Species
8. Extinct Species
Caribbean Monk Seal
Japanese Sea Lion
Baiji
Steller’s Sea Cow
547
Miller, 1918
Baiji
Extinct
Baiji — Lipotes vexillifer
Recently-used synonyms None. Common names En. – baiji, Yangtze River dolphin; Sp. – delfín del Yangtze; Fr. – dauphin fluviatile de Chine, baiji. Taxonomic information Cetartiodactyla, Cetacea, Odontoceti, Lipotidae. Molecular studies suggest the baiji may have had a common ancestor with the boto and franciscana, but not with the South Asian river dolphin. It was a relict species. Species characteristics Outside of China, very little was known of the baiji’s biology until the 1970s and 1980s. Baijis had a fairly typical river dolphin appearance. These animals were moderately robust, with long, slightlyupturned beaks, rounded melons, and broad rounded flippers. There were bulging “cheeks” on the face. The dorsal fin was fairly prominent, but low and triangular, with a wide base — it was set about 2/3 of the way back from the beak tip. The eyes were small and set higher on the face, compared to those of oceanic dolphins.
548
Although their vision was apparently poor, the eyes were functional. The blowhole was a longitudinal oval. Baijis had rather simple, countershaded color patterns. They were predominantly gray to bluish-gray above and white to ashy-white on the ventral surface. There were light patches and brushings on the side of the face and the side of the tail stock. Each tooth row of the baiji’s mouth contained 31 – 36 conical teeth. Male baijis reached sizes of 2.3 m and 157 kg, and females reached 2.6 m and over 167 kg. In addition to females being somewhat larger than males, there were some other, minor differences in external morphology between the sexes. Apparently, newborn Yangtze River dolphins were about 92 cm in length. Recognizable geographic forms None. Distribution In recent times, the baiji was found only in the middle and lower reaches of the mainstream Yangtze River in China (a length of about 1,400 km). The historical range was much broader, including waters of the Yangtze estuary, and several large lakes that dolphins entered during the flood season. They tended to congregate near confluences and sand bars with large eddies. Ecology and behavior Groups of two to six baijis were most commonly seen, but aggregations of up to 16 animals sometimes formed. Mixed groups with finless porpoises were quite common (in the most recent surveys, about 63% of sightings). The porpoises appeared to behave aggressively towards baijis on some occasions, although it is not known if this was typical. Baiji groups in recent surveys consisted of about 57% adults, 26% juveniles, and 17% calves. These dolphins were generally shy of boats, and their surfacings were shallow, often exposing only the top of the head, dorsal fin, and a small part of the back. They generally breathed with little surface disturbance, and most submersions were 10 – 30 sec long, with occasional
Baiji
Extinct
Extinct Species
A dead baiji, which was killed by rolling hook fishing gear, lies along the banks of the Yangtze River. The low, extremely wide-based dorsal ridge and “cheeks” are distinctive to this species. This animal appears to be emaciated. PHOTO: ZHOU KAIYA, COURTESY of S. LEATHERWOOD
A captive baiji swims in the clear waters of its tank in China. The waters of its natural habitat are in fact, very murky. Wuhan Institute of Hydro biology. PHOTO: WANG DING
Qi Qi lived in captivity for 22 years and died in 2002. Now apparently extinct, the baiji lived only in the Yangtze River of China. Wuhan Institute of Hydrobiology. PHOTO: WANG DING Much of what we know about the biology of the baiji came from studies of just a couple of captive individuals. Most famous of these was Qi Qi, shown here. Wuhan Institute of Hydro biology. PHOTO: WANG DING
549
Baiji
Extinct
M a r i n e M a m m a l s o f t h e Wo r l d
longer dives (the longest ones recorded were slightly under 3.5 min). Baiji movements included both short- and longdistance (200+ km) meanderings. Breeding occurred mainly in the first half of the year; the peak calving season was February to April. Males reached sexual maturity at ages of about 4 years, and females did so at about 6 years. The oldest known individual was 30 years old. It is assumed that there was only a single population, although this was never tested. Feeding and prey Baijis were apparently opportunistic feeders. A large variety of freshwater fish species made up the diet of the baiji, the only limitation probably being size. Threats and status For most of the past several decades, the baiji was widely acknowledged to be the most critically-endangered cetacean in the world. In fact, sightings in the new millennium had become exceedingly rare. Although protected by Chinese law (it was a “Protected Species of the First Order”), and direct killing was considered rare, other threats were rampant. The main threat was probably mortality from non-selective fishing gear, such as rolling hooks (a type of snagging “longline”), and dynamite and electric fishing (the latter became a major threat, accounting for about 40% of baiji mortalities).
550
Habitat deterioration/destruction was another major factor, as the Yangtze River has been dramatically modified to meet the needs of the huge surrounding human population (by some assessments, nearly 10% of the world’s total). Other conservation issues included pollution, vessel collisions, and prey depletion. The genetic and demographic consequences of extremely low population size, although often overlooked, were another class of problems. In the latter half of the 1900s and early 2000s, as the threats got more serious, Chinese officials had been attempting to remove animals from the river, and placing them into a “semi-natural reserve.” However, even this became infeasible, as living specimens were hard to find. A 3,500-km survey by an international team of experts, which covered nearly all of the species’ known range over a 6-week period in late 2006, failed to observe or acoustically detect a single dolphin. Only sporadic, undocumented sightings have been reported since. It is therefore virtually certain that the species is now extinct. Sadly, the baiji became the first species of cetacean to be exterminated by human activities. IUCN status Critically Endangered (IUCN has not yet officially declared it “Extinct”).
Japanese Sea Lion —Zalophus japonicus
Japanese Sea Lion
Extinct
(Peters, 1866)
Exact appearance unknown; Japanese sea lion is thought to most closely resemble the California sea lion (shown here).
Adult Female
Adult Male
Pup
Recently-used synonyms Zalophus californianus japonicus. Common names En. –Japanese sea lion; Sp. –lobo marino de Japón; Fr. –lion de mer de Japon. Taxonomic information Carnivora, Otariidae. Currently, the Japanese sea lion is considered a separate species. Until recently, most authors classified it, along with Galapagos and California sea lion, as subspecies of Z. californianus. Species characteristics Very little information exists on the appearance of this animal, but it was once considered a subspecies of the California sea lion. In an account from
Last Known Location
otter and seal hunters working in the western Pacific in the early 20th century, the “black sea lion” was said to have been present, in addition to Steller sea lions. This common name may point out that some animals, presumably adult males, as is the case for most adult male California sea lions, were very dark brown to black. A mid-19th century work gives a description of females as “straw colored with a darker throat and chest,” which is also consistent with the coloration of female and juvenile California sea lions. Adult males were 2.5 m, females 1.4 m, and a 4month-old pup was 65 cm long and 9 kg, according to a Japanese zoologist in the 1950s. A study in 2004 examined 12 skulls and found them to be significantly longer than the skulls of adult male California sea lions. Recent efforts to retrieve data on length and weight and reconstruct parameters suggest the range of standard length (nose to end of the tail) of a small number of adult males to be 2.28–2.49 m and for one sub-adult female to be 1.63 m. A single adult male of total length of 2.88 m (nose to the end of the hindflippers) was estimated to weigh 493.7 kg. If this is representative of the species, the Japanese sea lion may have been 10% longer and 30% heavier than the California sea lion. The difference between Japanese sea lions and California sea lions was large enough that only the largest adult male California sea lion skulls reached the length of the shortest adult male Japanese sea lion skulls. Japanese sea lion skulls are also longer and wider in a number of measurements, 551
Japanese Sea Lion
Extinct
M a r i n e M a m m a l s o f t h e Wo r l d
They were also found throughout the Kuril Island Archipelago to southernmost Kamchatka, Russia. A recent review lists 28 locations around the islands of Japan and the south end of Sakhalin Island that were used by Japanese sea lions, with four sites known to have served as locations with breeding: Liancourt Rocks (also known as Takeshima, or Dokdo, Islands), Kyuroku-jima Island, Aomori Prefecture, and Shikine-jima and Onbase-jima Islands near Tokyo. Ecology and behavior Very little information is available on these animals, although they were assumed to be similar to the California sea lion. They were said to be good divers, although studies on diving were never There are very few photos of Japanese sea lions, such as these at an undated, unknown location conducted. Breeding was said to ocon a rocky reef. The group includes several large, dark adult males with thick necks and pale faces cur from April to July. and muzzles. At least one animal appears to have a sagittal crest, as seen on adult male California Feeding and prey Japanese sea lions sea lions. There are also a number of smaller animals, several of which are partly or wholly pale. PHOTO: SHIMANE PREFECTURAL GOVERNMENT (NAKAWATaSE ALBUM), COURTESY OF T. SUYAMA AND T. YAMADA apparently fed on fishes. Historical information from a review stated that and also had a significantly taller sagittal crest. Taken they were caught in “fixed nets,” that they ate yellowtail together, these findings also suggest that adult male (Seriola lalandi) and fed on sardines and squid, but no Japanese sea lions were larger than adult male California other information is available. sea lions. Only one adult female Japanese sea lion skull Threats and status The Japanese sea lion is probably extinct. was examined in this study, so it was not possible to draw A comprehensive survey has not been made to determine if the species might still exist, and there has been only a conclusions about females from skulls. Only a single photograph was found for preparation minimal effort to search for specimens, accounts, data, and of this account, and on careful examination, the large photographs in Japan, South and North Korea, and Russia. animals closely resemble adult male California sea lions, There is a long history of hunting and harvesting for meat, with a prominent sagittal crest and the appearance of a pelts, and fat for rendering of lamp oil that goes back to the pale colored mask in the face that contrasts with the very Jo¯mon period (approximately 5,000 years ago, or more). dark body. Observers in the former range of this species From the mid-19th century until World War II, sea lions should be vigilant, and detailed notes should be made of were harvested with firearms and nets. During a period any otariids that cannot be readily identified as Steller sea of apparent intensive harvesting from 1904 –1911, an eslions or northern fur seals. For field identification pur- timated 14,000 sea lions of both sexes and all ages were poses, Japanese sea lion features should be presumed to harvested at Liancourt Rocks alone. Estimates are that 30,000 –50,000 animals may have been present in the midbe similar to those of California sea lion. 19th century. The last population estimates available were Recognizable geographic forms None. Can be confused with Japanese sea lions shared their range of 100 animals on Liancourt Rocks and a total population with Steller sea lions and northern fur seals. Assuming that of 300 by the late 1950s. The species probably became exJapanese sea lions were similar to California sea lions, re- tinct sometime in the late 1950s. Reports of sightings from fer to the “Can be confused with” section for California as recently as December 1975 from Liancourt Rocks were published recently, but no evidence was provided. Hope of sea lions. Distribution Japanese sea lions were found at least from the the remote possibility of a remnant colony surviving in an end of the Korean Peninsula and along the northwestern isolated area of the former range still exists, however the coast and the southern end of Japan, along both coasts, prevailing opinion is that the species is extinct. throughout the Sea of Japan to southern Sakhalin Island. IUCN status Extinct.
552
Recently-used synonyms Monachus tropicalis. Common names En. – Caribbean monk seal, West Indian monk seal; Sp. – foca monja del Caribe, foca fraile del Caribe; Fr. – phoque moine des Caraïbes. Taxonomic Information Carnivora, Phocidae. Until recently, the three monk seal species were in the genus Monachus. However, the extinct Caribbean monk seal and the Hawaiian monk seal are more closely related to each other genetically and morphologically than either is to the Mediterranean monk seal. In 2014, the new genus Neomonachus was proposed for the two allied species of the New World, and accepted by the Society for Marine Mammalogy. Species characteristics Adult Caribbean monk seals were brown with a grayish tinge above, due to the tips of the hairs being lighter. The color became lighter on the sides, and transitioned to yellowish-white below. The end of the muzzle and upper and lower lip areas on the sides of the 100W
90W
80W
70W
NORTH AMERICA
30N
C aribbean Sea
15N
1,000 NM
Caribbean Monk Seal (Neomonachus tropicalis) Global Distribution
Primary Range Last Colony Last Sighting
60W
muzzle were yellowish-white. Adult vibrissae were predominantly whitish and smooth, with a few having darker bases, and still other short vibrissae were entirely dark. No difference in coloration was noted between males and females. Younger animals tended to be paler than adults, appearing more yellowish dorsally, with ochre tones ventrally, and a dusky central area at the end of the muzzle. Like Hawaiian monk seals, Caribbean monk seals were said to occasionally have green algae growing on the pelage. Females had four abdominal mammae. Newborn pups had a long, soft, glossy black lanugo coat that persisted for an unknown period of time. The vibrissae of pups were uniformly dark. Generally, these seals were described as having very few scars from fighting, although one large adult male was observed with gashes and scars that resembled seams. Adult Caribbean monk seals reached at least 2.4 m in length, (females may have been slightly larger than males). Hawaiian monk seals of comparable length to the largest reported Caribbean monk seals weigh 170 – 270 kg. Pups were probably about 1 m and 16 – 18 kg at birth. The dental formula was: I 2/2, C 1/1, PC 5/5. Can be confused with No other pinniped species regularly inhabits the former range of the Caribbean monk seal. Hooded, harbor, and less frequently, harp seals are known to stray occasionally as far south as the central east coast of Florida, near the edges of the Caribbean monk seal’s former range. A monk seal could easily be distinguished from all of the above by the following collection of features: their long unspotted and unbanded body, brownish dorsal and pale ventral coloration, broad flat head and muzzle, and smooth unbeaded vibrissae. California sea lions that have escaped from captivity have also been reported from the Gulf of Mexico, but otariid seals differ from monk seals by the presence of external ear pinnae, long oarlike foreflippers, and a long narrow head and dog-like 553
Caribbean Monk Seal
(Gray, 1850)
Extinct
Caribbean Monk Seal — Neomonachus tropicalis
Caribbean Monk Seal
Extinct
M a r i n e M a m m a l s o f t h e Wo r l d
female was hauled out in the vicinity of a female suckling a pup. Hauledout groups of 20 – 40 were observed and reference was made to groups of 100 or more in earlier times. An otherwise undescribed group of five animals hauled out together included a large, scarred adult male. On another occasion, collectors encountered a group whose composition and numbers were not given, but the seals were “huddled together.” Young Caribbean monk seals were also said to rest in pools of water, presumably A rare photograph, from around 1910, of a Caribbean monk seal. This was one of three animals for thermoregulation. Several descripcollected in 1909 and exhibited at the New York Aquarium. Its age and sex are unknown. Captured tions exist of the vocalizations of the at Arrecifés Triángulos or Arrecife Alacrán, Mexico. PHOTO: COURTESY OF THE american Museum of Caribbean monk seal. A young aniNatural History, DEPARTMENT OF MAMMALOGY ARCHIVES mal briefly held in captivity was said muzzle. West Indian manatees shared part of the range to grunt like a pig, and bark, growl and snarl like a dog. In of Caribbean monk seals and were similar in color. Key another account, seals approached by hunters were said differences are the larger size, greater mass and width of to “bark in a hoarse, gurgling, death-rattle tone.” adult manatees, and the muzzle and head shape, with the Feeding and prey There is no information on the seals’ food seal having a much smaller head and larger eyes. Also, the and feeding habits. The animals collected in 1886 all had large paddle on the manatee is strikingly different than the stomachs that had fluid only, or were empty. The assumption is that their diet consisted of fish and crustaceans. hindflippers on any seal. Distribution This monk seal once inhabited most of Threats and status The Caribbean monk seal is now exthe Caribbean Sea, southern Florida, the waters of the tinct, and extensive searches have been unsuccessful. Bahamas, and the Gulf of Mexico, except for the northern A recent study calculated that prior to European con– 338,000 monk seals ranged across the and western Gulf, where sightings are unconfirmed. The tact, 233,000 last stronghold of the species was the Serrana Bank, a Caribbean in 13 – 14 breeding colonies. The first references to the species are from the voyages of Christopher remote reef lying between Jamaica and Nicaragua. Ecology and behavior Observations made in the field, Columbus (1494), and exploitation of the New World, and from animals collected in the 19th century, provide particularly after the development of the sugar industry, evidence that pups were born from at least late fall to led to the seals being hunted heavily for oil. Records show early winter. A long pupping season is known for both that in 1688, monk seals were numerous enough at colothe Hawaiian and Mediterranean monk seals, which also nies to enable sealers to take “hundreds” in a single day. live in subtropical habitats, and it is reasonable to assume Colonies at the edge of the species’ range disappeared in this was the case for the Caribbean monk seal. Animals the 18th century. By 1850, the commercial hunt was no collected in December 1886 included newborn pups, longer viable, and as the species became rare, large sums and several females with term fetuses. Also, an animal were paid for zoo and museum specimens, such as the described as recently weaned was encountered in the 49 monk seals collected in December 1886. By 1922, the seals had been extirpated from the northern Caribbean. spring, and a female with a large fetus was taken in July. It can be inferred that the Caribbean monk seal was Yet another factor in the seals’ demise may have been ina social species, possibly similar to the Hawaiian monk tensive commercial fishing that reduced the availability of seal. The 49 specimens collected in December 1886 were their prey. The last breeding colony to survive was on the all taken from three small cays in three days. The collec- Serrana Bank, and the last confirmed sighting of a monk tors describe finding females (with term fetuses) hauled seal was at Serranilla Bank in 1952. out near one another, and in another case a pregnant IUCN Status Extinct.
554
Steller’s Sea Cow—Hydrodamalis gigas
Steller’s Sea Cow
Extinct
(Zimmerman, 1780)
Recently-used synonyms None. Common names En.–Steller’s sea cow; Sp.–vaca marina de Steller; Fr.–rhytine de Steller. Taxonomic information Sirenia, Dugongidae. Although classified with the dugong in the family Dugongidae, the Steller’s sea cow was very distinctive and is generally placed in a separate subfamily. Species characteristics The external morphology of the Steller’s sea cow is not well-known, since the species was exterminated in 1768, before it could be studied in any detail. One thing is clear—this was a very large sirenian. It was rotund, especially in the summer, when feeding was good. It had a relatively-small head (only about 10% of body length) and horizontal flukes with a notch. The short, stubby forelimbs were about 60–70 cm long, with no nails or claws (and in fact, they lacked finger bones as well). The skin was rough on most of the body (so much so that people referred to it as like “bark”), although 180
160E
160W
60N
Bering Sea Commander Is. Aleutian Is.
50N
P a c i fi c O c e a n 1,000 NM
Steller’s Sea Cow (Hydrodamalis gigas) Global Distribution
Primary Range Secondary Range
somewhat smoother on the back. It was very thick, up to at least 3 cm thick in places. There was a sparse covering of white hairs on the body, as well as stiff white bristles on the lips and foreflippers. The nostrils were rounded, and the eyes small and black. There were no external ear pinnae, only minute auditory openings. Steller’s sea cow was brownish-black on the body, with a few white patches and streaks, especially on the undersides. Functional teeth were completely absent, and grinding of food was done by keratinized masticatory plates inside the mouth. These were apparently white in color and “boat-shaped.” These massive animals grew to lengths of at least 7.52 m. The weights attained by these animals are not known, but have been estimated to be somewhere between 4,000–10,000 kg. They were, by far, the largest of the sirenians. Distribution These animals lived only in the shallow, nearshore waters of the subarctic Bering Sea. They were found along the Commander Islands, and probably also occurred in the western Aleutian Islands. They were said to come very close to shore during high tide. A skull fragment from Monterey Bay, California, and other evidence suggests that historically the species may have ranged farther south. Ecology and behavior Steller’s sea cows often congregated in small herds in shallow waters. Young were said to have been kept at the front of the group, surrounded by adults on the sides and from behind. While largely defenseless, Steller’s sea cow’s huge size may have kept it safe from most enemies, except killer whales (and of course, humans). Seabirds often picked parasites from the animals’ backs. Not much is known of the behavior of this species. They spent most of their time feeding in kelp beds, near the islands. However, they apparently had difficulty submerging, due to their great buoyancy. They floated with their backs exposed and lifted their heads to breathe 555
Steller’s Sea Cow
Extinct
M a r i n e M a m m a l s o f t h e Wo r l d
mostly in the autumn. Copulation is said to have taken place in the early spring months, and gestation lasted more than one year. Feeding and prey Steller’s sea cows fed mostly on algae, especially kelp. They apparently only ate the leafy parts of the plants. Threats and status Steller’s sea cow was discovered in 1741, and after just 27 years of relentless exploitation by (mostly Russian) fur traders, it became extinct in 1768. It was hunted with harpoons from boats, and with spears and hooks from shore. It was highly prized for its meat, skin and Since the species went extinct in the 1700s, there are no photos of Steller’s sea cow. However, this model from the Natural History Museum of Milan provides a good indication of what this unusual blubber by explorers and hunters in marine mammal would have looked like. PHOTO: V. FOGATO the North Pacific. The meat was used for food, the skin for shoes and boats, every 4 to 5 min. They pulled themselves through the and the fat for food and lamp oil. It was thought by those shallows with their short forelimbs, and used their flukes who observed them that the population was larger than both vertically and horizontally to move through the it actually was (pre-exploitation numbers were estimated water. Apparently, they sometimes slept on their backs. at about 1,500 to 2,000 animals), and there was no reAnimals were observed to stand by injured conspecifics. straint on the wasteful hunting. Later reports of sightings They were thought to have been largely mute, with few of this species have been convincingly refuted, and there sounds heard from them (although of course, no under- is no doubt that it is long extinct, the first modern marine water recordings were made). mammal species to be wiped out through human ignoVirtually nothing is known about reproduction in this rance and greed. species, except that a single young was born, apparently IUCN Status Extinct.
556
Caribbean Monk Seal
Japanese Sea Lion
Baiji
Steller’s Sea Cow
547
Miller, 1918
Baiji
Extinct
Baiji — Lipotes vexillifer
Recently-used synonyms None. Common names En. – baiji, Yangtze River dolphin; Sp. – delfín del Yangtze; Fr. – dauphin fluviatile de Chine, baiji. Taxonomic information Cetartiodactyla, Cetacea, Odontoceti, Lipotidae. Molecular studies suggest the baiji may have had a common ancestor with the boto and franciscana, but not with the South Asian river dolphin. It was a relict species. Species characteristics Outside of China, very little was known of the baiji’s biology until the 1970s and 1980s. Baijis had a fairly typical river dolphin appearance. These animals were moderately robust, with long, slightlyupturned beaks, rounded melons, and broad rounded flippers. There were bulging “cheeks” on the face. The dorsal fin was fairly prominent, but low and triangular, with a wide base — it was set about 2/3 of the way back from the beak tip. The eyes were small and set higher on the face, compared to those of oceanic dolphins.
548
Although their vision was apparently poor, the eyes were functional. The blowhole was a longitudinal oval. Baijis had rather simple, countershaded color patterns. They were predominantly gray to bluish-gray above and white to ashy-white on the ventral surface. There were light patches and brushings on the side of the face and the side of the tail stock. Each tooth row of the baiji’s mouth contained 31 – 36 conical teeth. Male baijis reached sizes of 2.3 m and 157 kg, and females reached 2.6 m and over 167 kg. In addition to females being somewhat larger than males, there were some other, minor differences in external morphology between the sexes. Apparently, newborn Yangtze River dolphins were about 92 cm in length. Recognizable geographic forms None. Distribution In recent times, the baiji was found only in the middle and lower reaches of the mainstream Yangtze River in China (a length of about 1,400 km). The historical range was much broader, including waters of the Yangtze estuary, and several large lakes that dolphins entered during the flood season. They tended to congregate near confluences and sand bars with large eddies. Ecology and behavior Groups of two to six baijis were most commonly seen, but aggregations of up to 16 animals sometimes formed. Mixed groups with finless porpoises were quite common (in the most recent surveys, about 63% of sightings). The porpoises appeared to behave aggressively towards baijis on some occasions, although it is not known if this was typical. Baiji groups in recent surveys consisted of about 57% adults, 26% juveniles, and 17% calves. These dolphins were generally shy of boats, and their surfacings were shallow, often exposing only the top of the head, dorsal fin, and a small part of the back. They generally breathed with little surface disturbance, and most submersions were 10 – 30 sec long, with occasional
Baiji
Extinct
Extinct Species
A dead baiji, which was killed by rolling hook fishing gear, lies along the banks of the Yangtze River. The low, extremely wide-based dorsal ridge and “cheeks” are distinctive to this species. This animal appears to be emaciated. PHOTO: ZHOU KAIYA, COURTESY of S. LEATHERWOOD
A captive baiji swims in the clear waters of its tank in China. The waters of its natural habitat are in fact, very murky. Wuhan Institute of Hydro biology. PHOTO: WANG DING
Qi Qi lived in captivity for 22 years and died in 2002. Now apparently extinct, the baiji lived only in the Yangtze River of China. Wuhan Institute of Hydrobiology. PHOTO: WANG DING Much of what we know about the biology of the baiji came from studies of just a couple of captive individuals. Most famous of these was Qi Qi, shown here. Wuhan Institute of Hydro biology. PHOTO: WANG DING
549
Baiji
Extinct
M a r i n e M a m m a l s o f t h e Wo r l d
longer dives (the longest ones recorded were slightly under 3.5 min). Baiji movements included both short- and longdistance (200+ km) meanderings. Breeding occurred mainly in the first half of the year; the peak calving season was February to April. Males reached sexual maturity at ages of about 4 years, and females did so at about 6 years. The oldest known individual was 30 years old. It is assumed that there was only a single population, although this was never tested. Feeding and prey Baijis were apparently opportunistic feeders. A large variety of freshwater fish species made up the diet of the baiji, the only limitation probably being size. Threats and status For most of the past several decades, the baiji was widely acknowledged to be the most critically-endangered cetacean in the world. In fact, sightings in the new millennium had become exceedingly rare. Although protected by Chinese law (it was a “Protected Species of the First Order”), and direct killing was considered rare, other threats were rampant. The main threat was probably mortality from non-selective fishing gear, such as rolling hooks (a type of snagging “longline”), and dynamite and electric fishing (the latter became a major threat, accounting for about 40% of baiji mortalities).
550
Habitat deterioration/destruction was another major factor, as the Yangtze River has been dramatically modified to meet the needs of the huge surrounding human population (by some assessments, nearly 10% of the world’s total). Other conservation issues included pollution, vessel collisions, and prey depletion. The genetic and demographic consequences of extremely low population size, although often overlooked, were another class of problems. In the latter half of the 1900s and early 2000s, as the threats got more serious, Chinese officials had been attempting to remove animals from the river, and placing them into a “semi-natural reserve.” However, even this became infeasible, as living specimens were hard to find. A 3,500-km survey by an international team of experts, which covered nearly all of the species’ known range over a 6-week period in late 2006, failed to observe or acoustically detect a single dolphin. Only sporadic, undocumented sightings have been reported since. It is therefore virtually certain that the species is now extinct. Sadly, the baiji became the first species of cetacean to be exterminated by human activities. IUCN status Critically Endangered (IUCN has not yet officially declared it “Extinct”).
Japanese Sea Lion —Zalophus japonicus
Japanese Sea Lion
Extinct
(Peters, 1866)
Exact appearance unknown; Japanese sea lion is thought to most closely resemble the California sea lion (shown here).
Adult Female
Adult Male
Pup
Recently-used synonyms Zalophus californianus japonicus. Common names En. –Japanese sea lion; Sp. –lobo marino de Japón; Fr. –lion de mer de Japon. Taxonomic information Carnivora, Otariidae. Currently, the Japanese sea lion is considered a separate species. Until recently, most authors classified it, along with Galapagos and California sea lion, as subspecies of Z. californianus. Species characteristics Very little information exists on the appearance of this animal, but it was once considered a subspecies of the California sea lion. In an account from
Last Known Location
otter and seal hunters working in the western Pacific in the early 20th century, the “black sea lion” was said to have been present, in addition to Steller sea lions. This common name may point out that some animals, presumably adult males, as is the case for most adult male California sea lions, were very dark brown to black. A mid-19th century work gives a description of females as “straw colored with a darker throat and chest,” which is also consistent with the coloration of female and juvenile California sea lions. Adult males were 2.5 m, females 1.4 m, and a 4month-old pup was 65 cm long and 9 kg, according to a Japanese zoologist in the 1950s. A study in 2004 examined 12 skulls and found them to be significantly longer than the skulls of adult male California sea lions. Recent efforts to retrieve data on length and weight and reconstruct parameters suggest the range of standard length (nose to end of the tail) of a small number of adult males to be 2.28–2.49 m and for one sub-adult female to be 1.63 m. A single adult male of total length of 2.88 m (nose to the end of the hindflippers) was estimated to weigh 493.7 kg. If this is representative of the species, the Japanese sea lion may have been 10% longer and 30% heavier than the California sea lion. The difference between Japanese sea lions and California sea lions was large enough that only the largest adult male California sea lion skulls reached the length of the shortest adult male Japanese sea lion skulls. Japanese sea lion skulls are also longer and wider in a number of measurements, 551
Japanese Sea Lion
Extinct
M a r i n e M a m m a l s o f t h e Wo r l d
They were also found throughout the Kuril Island Archipelago to southernmost Kamchatka, Russia. A recent review lists 28 locations around the islands of Japan and the south end of Sakhalin Island that were used by Japanese sea lions, with four sites known to have served as locations with breeding: Liancourt Rocks (also known as Takeshima, or Dokdo, Islands), Kyuroku-jima Island, Aomori Prefecture, and Shikine-jima and Onbase-jima Islands near Tokyo. Ecology and behavior Very little information is available on these animals, although they were assumed to be similar to the California sea lion. They were said to be good divers, although studies on diving were never There are very few photos of Japanese sea lions, such as these at an undated, unknown location conducted. Breeding was said to ocon a rocky reef. The group includes several large, dark adult males with thick necks and pale faces cur from April to July. and muzzles. At least one animal appears to have a sagittal crest, as seen on adult male California Feeding and prey Japanese sea lions sea lions. There are also a number of smaller animals, several of which are partly or wholly pale. PHOTO: SHIMANE PREFECTURAL GOVERNMENT (NAKAWATaSE ALBUM), COURTESY OF T. SUYAMA AND T. YAMADA apparently fed on fishes. Historical information from a review stated that and also had a significantly taller sagittal crest. Taken they were caught in “fixed nets,” that they ate yellowtail together, these findings also suggest that adult male (Seriola lalandi) and fed on sardines and squid, but no Japanese sea lions were larger than adult male California other information is available. sea lions. Only one adult female Japanese sea lion skull Threats and status The Japanese sea lion is probably extinct. was examined in this study, so it was not possible to draw A comprehensive survey has not been made to determine if the species might still exist, and there has been only a conclusions about females from skulls. Only a single photograph was found for preparation minimal effort to search for specimens, accounts, data, and of this account, and on careful examination, the large photographs in Japan, South and North Korea, and Russia. animals closely resemble adult male California sea lions, There is a long history of hunting and harvesting for meat, with a prominent sagittal crest and the appearance of a pelts, and fat for rendering of lamp oil that goes back to the pale colored mask in the face that contrasts with the very Jo¯mon period (approximately 5,000 years ago, or more). dark body. Observers in the former range of this species From the mid-19th century until World War II, sea lions should be vigilant, and detailed notes should be made of were harvested with firearms and nets. During a period any otariids that cannot be readily identified as Steller sea of apparent intensive harvesting from 1904 –1911, an eslions or northern fur seals. For field identification pur- timated 14,000 sea lions of both sexes and all ages were poses, Japanese sea lion features should be presumed to harvested at Liancourt Rocks alone. Estimates are that 30,000 –50,000 animals may have been present in the midbe similar to those of California sea lion. 19th century. The last population estimates available were Recognizable geographic forms None. Can be confused with Japanese sea lions shared their range of 100 animals on Liancourt Rocks and a total population with Steller sea lions and northern fur seals. Assuming that of 300 by the late 1950s. The species probably became exJapanese sea lions were similar to California sea lions, re- tinct sometime in the late 1950s. Reports of sightings from fer to the “Can be confused with” section for California as recently as December 1975 from Liancourt Rocks were published recently, but no evidence was provided. Hope of sea lions. Distribution Japanese sea lions were found at least from the the remote possibility of a remnant colony surviving in an end of the Korean Peninsula and along the northwestern isolated area of the former range still exists, however the coast and the southern end of Japan, along both coasts, prevailing opinion is that the species is extinct. throughout the Sea of Japan to southern Sakhalin Island. IUCN status Extinct.
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Recently-used synonyms Monachus tropicalis. Common names En. – Caribbean monk seal, West Indian monk seal; Sp. – foca monja del Caribe, foca fraile del Caribe; Fr. – phoque moine des Caraïbes. Taxonomic Information Carnivora, Phocidae. Until recently, the three monk seal species were in the genus Monachus. However, the extinct Caribbean monk seal and the Hawaiian monk seal are more closely related to each other genetically and morphologically than either is to the Mediterranean monk seal. In 2014, the new genus Neomonachus was proposed for the two allied species of the New World, and accepted by the Society for Marine Mammalogy. Species characteristics Adult Caribbean monk seals were brown with a grayish tinge above, due to the tips of the hairs being lighter. The color became lighter on the sides, and transitioned to yellowish-white below. The end of the muzzle and upper and lower lip areas on the sides of the 100W
90W
80W
70W
NORTH AMERICA
30N
C aribbean Sea
15N
1,000 NM
Caribbean Monk Seal (Neomonachus tropicalis) Global Distribution
Primary Range Last Colony Last Sighting
60W
muzzle were yellowish-white. Adult vibrissae were predominantly whitish and smooth, with a few having darker bases, and still other short vibrissae were entirely dark. No difference in coloration was noted between males and females. Younger animals tended to be paler than adults, appearing more yellowish dorsally, with ochre tones ventrally, and a dusky central area at the end of the muzzle. Like Hawaiian monk seals, Caribbean monk seals were said to occasionally have green algae growing on the pelage. Females had four abdominal mammae. Newborn pups had a long, soft, glossy black lanugo coat that persisted for an unknown period of time. The vibrissae of pups were uniformly dark. Generally, these seals were described as having very few scars from fighting, although one large adult male was observed with gashes and scars that resembled seams. Adult Caribbean monk seals reached at least 2.4 m in length, (females may have been slightly larger than males). Hawaiian monk seals of comparable length to the largest reported Caribbean monk seals weigh 170 – 270 kg. Pups were probably about 1 m and 16 – 18 kg at birth. The dental formula was: I 2/2, C 1/1, PC 5/5. Can be confused with No other pinniped species regularly inhabits the former range of the Caribbean monk seal. Hooded, harbor, and less frequently, harp seals are known to stray occasionally as far south as the central east coast of Florida, near the edges of the Caribbean monk seal’s former range. A monk seal could easily be distinguished from all of the above by the following collection of features: their long unspotted and unbanded body, brownish dorsal and pale ventral coloration, broad flat head and muzzle, and smooth unbeaded vibrissae. California sea lions that have escaped from captivity have also been reported from the Gulf of Mexico, but otariid seals differ from monk seals by the presence of external ear pinnae, long oarlike foreflippers, and a long narrow head and dog-like 553
Caribbean Monk Seal
(Gray, 1850)
Extinct
Caribbean Monk Seal — Neomonachus tropicalis
Caribbean Monk Seal
Extinct
M a r i n e M a m m a l s o f t h e Wo r l d
female was hauled out in the vicinity of a female suckling a pup. Hauledout groups of 20 – 40 were observed and reference was made to groups of 100 or more in earlier times. An otherwise undescribed group of five animals hauled out together included a large, scarred adult male. On another occasion, collectors encountered a group whose composition and numbers were not given, but the seals were “huddled together.” Young Caribbean monk seals were also said to rest in pools of water, presumably A rare photograph, from around 1910, of a Caribbean monk seal. This was one of three animals for thermoregulation. Several descripcollected in 1909 and exhibited at the New York Aquarium. Its age and sex are unknown. Captured tions exist of the vocalizations of the at Arrecifés Triángulos or Arrecife Alacrán, Mexico. PHOTO: COURTESY OF THE american Museum of Caribbean monk seal. A young aniNatural History, DEPARTMENT OF MAMMALOGY ARCHIVES mal briefly held in captivity was said muzzle. West Indian manatees shared part of the range to grunt like a pig, and bark, growl and snarl like a dog. In of Caribbean monk seals and were similar in color. Key another account, seals approached by hunters were said differences are the larger size, greater mass and width of to “bark in a hoarse, gurgling, death-rattle tone.” adult manatees, and the muzzle and head shape, with the Feeding and prey There is no information on the seals’ food seal having a much smaller head and larger eyes. Also, the and feeding habits. The animals collected in 1886 all had large paddle on the manatee is strikingly different than the stomachs that had fluid only, or were empty. The assumption is that their diet consisted of fish and crustaceans. hindflippers on any seal. Distribution This monk seal once inhabited most of Threats and status The Caribbean monk seal is now exthe Caribbean Sea, southern Florida, the waters of the tinct, and extensive searches have been unsuccessful. Bahamas, and the Gulf of Mexico, except for the northern A recent study calculated that prior to European con– 338,000 monk seals ranged across the and western Gulf, where sightings are unconfirmed. The tact, 233,000 last stronghold of the species was the Serrana Bank, a Caribbean in 13 – 14 breeding colonies. The first references to the species are from the voyages of Christopher remote reef lying between Jamaica and Nicaragua. Ecology and behavior Observations made in the field, Columbus (1494), and exploitation of the New World, and from animals collected in the 19th century, provide particularly after the development of the sugar industry, evidence that pups were born from at least late fall to led to the seals being hunted heavily for oil. Records show early winter. A long pupping season is known for both that in 1688, monk seals were numerous enough at colothe Hawaiian and Mediterranean monk seals, which also nies to enable sealers to take “hundreds” in a single day. live in subtropical habitats, and it is reasonable to assume Colonies at the edge of the species’ range disappeared in this was the case for the Caribbean monk seal. Animals the 18th century. By 1850, the commercial hunt was no collected in December 1886 included newborn pups, longer viable, and as the species became rare, large sums and several females with term fetuses. Also, an animal were paid for zoo and museum specimens, such as the described as recently weaned was encountered in the 49 monk seals collected in December 1886. By 1922, the seals had been extirpated from the northern Caribbean. spring, and a female with a large fetus was taken in July. It can be inferred that the Caribbean monk seal was Yet another factor in the seals’ demise may have been ina social species, possibly similar to the Hawaiian monk tensive commercial fishing that reduced the availability of seal. The 49 specimens collected in December 1886 were their prey. The last breeding colony to survive was on the all taken from three small cays in three days. The collec- Serrana Bank, and the last confirmed sighting of a monk tors describe finding females (with term fetuses) hauled seal was at Serranilla Bank in 1952. out near one another, and in another case a pregnant IUCN Status Extinct.
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Steller’s Sea Cow—Hydrodamalis gigas
Steller’s Sea Cow
Extinct
(Zimmerman, 1780)
Recently-used synonyms None. Common names En.–Steller’s sea cow; Sp.–vaca marina de Steller; Fr.–rhytine de Steller. Taxonomic information Sirenia, Dugongidae. Although classified with the dugong in the family Dugongidae, the Steller’s sea cow was very distinctive and is generally placed in a separate subfamily. Species characteristics The external morphology of the Steller’s sea cow is not well-known, since the species was exterminated in 1768, before it could be studied in any detail. One thing is clear—this was a very large sirenian. It was rotund, especially in the summer, when feeding was good. It had a relatively-small head (only about 10% of body length) and horizontal flukes with a notch. The short, stubby forelimbs were about 60–70 cm long, with no nails or claws (and in fact, they lacked finger bones as well). The skin was rough on most of the body (so much so that people referred to it as like “bark”), although 180
160E
160W
60N
Bering Sea Commander Is. Aleutian Is.
50N
P a c i fi c O c e a n 1,000 NM
Steller’s Sea Cow (Hydrodamalis gigas) Global Distribution
Primary Range Secondary Range
somewhat smoother on the back. It was very thick, up to at least 3 cm thick in places. There was a sparse covering of white hairs on the body, as well as stiff white bristles on the lips and foreflippers. The nostrils were rounded, and the eyes small and black. There were no external ear pinnae, only minute auditory openings. Steller’s sea cow was brownish-black on the body, with a few white patches and streaks, especially on the undersides. Functional teeth were completely absent, and grinding of food was done by keratinized masticatory plates inside the mouth. These were apparently white in color and “boat-shaped.” These massive animals grew to lengths of at least 7.52 m. The weights attained by these animals are not known, but have been estimated to be somewhere between 4,000–10,000 kg. They were, by far, the largest of the sirenians. Distribution These animals lived only in the shallow, nearshore waters of the subarctic Bering Sea. They were found along the Commander Islands, and probably also occurred in the western Aleutian Islands. They were said to come very close to shore during high tide. A skull fragment from Monterey Bay, California, and other evidence suggests that historically the species may have ranged farther south. Ecology and behavior Steller’s sea cows often congregated in small herds in shallow waters. Young were said to have been kept at the front of the group, surrounded by adults on the sides and from behind. While largely defenseless, Steller’s sea cow’s huge size may have kept it safe from most enemies, except killer whales (and of course, humans). Seabirds often picked parasites from the animals’ backs. Not much is known of the behavior of this species. They spent most of their time feeding in kelp beds, near the islands. However, they apparently had difficulty submerging, due to their great buoyancy. They floated with their backs exposed and lifted their heads to breathe 555
Steller’s Sea Cow
Extinct
M a r i n e M a m m a l s o f t h e Wo r l d
mostly in the autumn. Copulation is said to have taken place in the early spring months, and gestation lasted more than one year. Feeding and prey Steller’s sea cows fed mostly on algae, especially kelp. They apparently only ate the leafy parts of the plants. Threats and status Steller’s sea cow was discovered in 1741, and after just 27 years of relentless exploitation by (mostly Russian) fur traders, it became extinct in 1768. It was hunted with harpoons from boats, and with spears and hooks from shore. It was highly prized for its meat, skin and Since the species went extinct in the 1700s, there are no photos of Steller’s sea cow. However, this model from the Natural History Museum of Milan provides a good indication of what this unusual blubber by explorers and hunters in marine mammal would have looked like. PHOTO: V. FOGATO the North Pacific. The meat was used for food, the skin for shoes and boats, every 4 to 5 min. They pulled themselves through the and the fat for food and lamp oil. It was thought by those shallows with their short forelimbs, and used their flukes who observed them that the population was larger than both vertically and horizontally to move through the it actually was (pre-exploitation numbers were estimated water. Apparently, they sometimes slept on their backs. at about 1,500 to 2,000 animals), and there was no reAnimals were observed to stand by injured conspecifics. straint on the wasteful hunting. Later reports of sightings They were thought to have been largely mute, with few of this species have been convincingly refuted, and there sounds heard from them (although of course, no under- is no doubt that it is long extinct, the first modern marine water recordings were made). mammal species to be wiped out through human ignoVirtually nothing is known about reproduction in this rance and greed. species, except that a single young was born, apparently IUCN Status Extinct.
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