- Email: [email protected]
Food hiding and enrichment in captive Asian elephants
APPLIED ANIMAL BEHAVIOUR SCIENCE
ELSEVIER
Applied Animal Behaviour
Science 56 (1998) 77-82
Food hiding and enrichment in captive Asian elephants Christoph Wiedenmayer Abteilung Tiergartenbiologie,
Uniuersitiit Ziirich, Ziirichbergstrasse Accepted
* 221, Ziirich 8044, Switzerland
19 June 1997
Abstract Asian elephants (Elephas maximus) kept in zoos usually spend less time foraging than their wild conspecifics. In order to increase foraging in a group of captive Asian elephants, peanuts were hidden above a distinctive outdoor enclosure structure, the stone border. It was expected that the elephants would learn this association and increase food searching in the outdoor enclosure. After training, the elephants searched more above the stone borders than during baseline, which indicates that they learned the relationship between stone borders and peanuts. But hiding food did not enhance searching behaviour. Therefore, this method of food hiding did not represent an environmental enrichment. 0 1998 Elsevier Science B.V. Keywords:
Learning;
Elephants;
Environmental
enrichment
1. Introduction Although Asian elephants (Elephas maximus) have been kept traditionally by humans for hundreds of years, it is still debated how they should be housed in zoos (see American Association of Zoo Keepers, 1994). Wild Asian elephants spend a high proportion of their active time foraging (McKay, 1973; Vancuylenberg, 1977). Foraging requires elephants to locate potential food sources, manipulate them to get access to food and feed on them (Eltringham, 1982). In contrast, in many zoos, food is delivered to the elephants in large, spatially and temporally concentrated amounts which the elephants
* Corresponding author. Developmental Psychobiology, University, 722 W 168th Street Box 40, New York, + 1-212-543-5467; e-mail: cpw [email protected]
College of Physicians and Surgeons of Columbia NY 10032, USA. Tel.: + l-212-543-5706; fax:
0168.1591/98/$19.00 0 1998 Elsevier Science B.V. All rights reserved. PII SO168-1591(97)00091-9
78
C. Wiedenmayer/Applied
Animal Behmiour
Science 56 (1998) 77-82
can exploit very rapidly. Therefore, feeding procedures such as scattering and hiding small edible items in the enclosure have been proposed to increase foraging and are used in several zoos (e.g., Holst, 1990; Green, 1993). However, experimental data on the effect of such environmental enrichment measures in elephants are rare. The aim of the present study was to measure the influence of hidden food on the location and frequency of inspection of the environment by elephants. Food was presented to the elephants along enclosure structures, stone borders, rather than scattered at random, in order to identify some of the cues that they used to organise their search (Bell, 1991). It was hypothesised that (a) the elephants would learn the relationship between food and the border and would orient their searching accordingly, and that (b) this learning process would result in an overall increase in the frequency of food searching behaviour. It was assumed that increased searching is closer to the behaviour of wild elephants and therefore that hidden food presentation can be regarded as enrichment of housing conditions.
2. Methods 2.1. Animals and housing The group at Zurich Zoo consisted of three unrelated, wild-born female elephants, Druk, Chhukha (both 27 yrs) and Ceyla (19 yrs), and the two daughters of Ceyla, Komali (10 yrs) and Panang (5 yrs), both born at Zurich Zoo. They were housed in an elephant exhibit which consisted of an indoor platform (75 m’) and an outdoor enclosure (860 m2) (for details of the exhibit, see Schmidt, 1973). During the night, the elephants stayed indoors. They were given access to the outdoor enclosure in the morning. In the late afternoon, the animals were brought back into the house. They were fed indoors around 17:00 h. Food items such as hay, straw, bread, vegetables, fruits and pellets were presented on the floor of the platform. In addition, once or twice a day a few fresh tree branches were supplied in the outdoor enclosure. During the food hiding experiments there was no additional food available for the elephants in the outdoor enclosure. 2.2. Procedure 2.2.1. Baseline Baseline data were collected on searching behaviour without hidden food present. Before the elephants entered the outdoor enclosure around 10:00 h, the observer walked around the outdoor enclosure without hiding food to control for potential odour cues. Searching behaviour, defined as holding or moving of the trunk disc pointed toward the ground from a distance of < 10 cm, was recorded for each elephant by instantaneous sampling at intervals of 20 s during 1 h/day. This hour immediately followed the release of the elephants into the outdoor enclosure. One-hour observations were repeated on nine days during six weeks in March and April, 1994.
C. Wiedenmayer/Applied
Animal Behaoiour Science 56 (19981 77-82
79
2.2.2. Training The elephants had to learn the association between food and a particular structure of their environment. Stone borders were chosen as structures, because they occurred in four locations in the outdoor enclosure and because the elephants’ locomotion indicated that they also perceived them as distinct features. The stone borders varied in length between 4 m and 13 m, were 20 cm high and consisted of a continuous slightly curved row of stones. Peanuts were chosen as food items, because they were highly preferred by the elephants at Zurich Zoo. In pilot observations, it was found that the elephants could not locate peanuts on the ground visually; peanuts presented in such a way can thus be regarded as hidden. In contrast, apple halves were immediately detected and additionally elicited searching behaviour in their surround. Therefore, to orient the elephants’ searching during training, half an apple was placed in the middle above each stone border to provide a visible cue. A total of 2.5 peanuts was placed above the stone borders on both sides of the four apple-halves in a row at intervals of 1 m. As in the baseline, searching behaviour was recorded for 1 h/day after the elephants entered the outdoor enclosure. When the elephants searched at the upper edge of the stone borders (width of area 30 cm), searching was defined as ‘searching above’; if they searched at the ground below the stone borders (width 30 cm), searching was defined as ‘searching below’. In addition, the rate of finding food items was determined. Food presentation and data collection were carried out on 14 days during seven weeks in May, June and July, 1994. 2.2.3. Testing Searching behaviour was measured after the training. Again, 25 nuts were presented above the stone borders, but without visible cues, the apple-halves. The nuts were presented in the same specific locations as in the training phase. Data were recorded as in the other phases, on seven days distributed irregularly over seven weeks in August and September, 1994.
3. Results 3.1. Orientation
of searching
behaviour
During testing, searching behaviour above the stone borders was significantly increased (Mann-Whitney U-test, two-tailed, Z = -2.40, P < 0.02), in contrast to searching below the stone borders, which did not change significantly (Mann-Whitney U-test, two-tailed, Z = - 1.57, P > 0.1; Table 1). After entering the outdoor enclosure, the elephants spread, walked to the stone borders, and moved their trunk discs along these structures. When an elephant’s trunk disc came close to or touched a nut, she picked it up and ate it. Few social interactions occurred during this searching phase. The elephants found two thirds of the nuts within 10 min (Fig. l), but they did not always find all 25 nuts within 1 h. The locations of the nuts not found varied across trials.
80 Table 1 Searching
C. Wiedenmayer/AppliedAnimalBehauiourScience 56 (1998) 77-82
of the five elephant cows above the stone borders in % of total searching Above stoneborder
Druk Chhukha Ceyla Komali Panang
during baseline and testing
Below stoneborder
Baseline
Testing
Baseline
Testing
3.0 0.0 5.0 3.0 6.7
12.4 9.1 5.3 15.3 22.6
16.0 0.8 10.8 15.1 15.2
2.5 1.1 8.0 9.5 9.0
Fig. 1. Cumulative SD of 14 trials).
percent of nuts found by a group of five elephants during the 60 min of testing (mean and
3.2. Frequency
of searching
behaviour
The frequency of total searching behaviour across baseline, not differ (Kruskal-Wallis test, H = 0.14, P > 0.9; Table 2).
Table 2 Total searching behaviour training and testing
Druk Chhukha Ceyla Komali Panang
of the five elephant
cows in % of the observation
training
and testing did
time during baseline,
Baseline
Training
Testing
6.0 1.6 18.3 16.2 12.7
5.8 3.8 14.1 18.6 13.1
6.3 3.1 13.9 16.7 13.2
during
C. Wiedenmayer/Applied
Animal Behauiour Science 56 (1998) 77-82
4. Discussion
This experiment shows that elephants searched more above the enclosure structure stone border after they had repeatedly found peanuts there. This increase indicates that the elephants learned the relationship between stone borders and peanuts. They appear to have formed a searching rule about where to find food after entering the outdoor enclosure. Although this searching rule oriented their searching behaviour, they did not find all of the nuts in every trial. They did not pick up all nuts because either they could not remember the precise location of every nut, or because they were not motivated to search longer as peanuts may not be very rewarding food stimuli for elephants. Learning is facilitated if the spatial cue and the food are both part of a particular physical structure (Brown and Gass, 1993). A contiguity such as that between the nuts and the stone border is often characteristic of conditions in the wild. Macaques organise their foraging search in relation to the food’s proximity to specific classes of environmental structures such as river edges or trees (Menzel, 1991, 1996). In contrast to macaques, Asian elephants are mainly nonselective bulk feeders on poor quality food such as grass (Vancuylenberg, 1977; Eltringham, 1982). Nevertheless, they also feed on high-quality foods such as fruits, which are located at distinct habitat structures which require selective foraging (McKay, 1973; Sukumar, 1989). Hiding food is thought to mimic natural conditions and to be a form of environmental enrichment (Hutchins et al., 1984; Carlstead and Shepherdson, 1994). In small cats and wild dogs, hiding small food items in wood piles increased exploration not just prior to finding the food, but for some time after it had been found (Shepherdson et al., 1993; Ings et al., 1997). The rationale of the present study was that if elephants found favorite food distributed according to a specific pattern, they would increase their searching, at least during a certain time. Although the elephants learned to search for food, hiding food did not enhance searching behaviour. Nuts elicited a local increase of searching behaviour, but the elephants did not extend their searching to other structures of the enclosure, not even to the lower parts of the stone borders. Either Asian elephants cannot be motivated to search for peanuts during a large proportion of their time due to their nonselective feeding habits, an interpretation supported by the rapid decrease of the finding rate after 10 min, or the association to be learned was too easy to affect the searching behaviour. Future studies designed to test whether other patterns of food hiding or other types of food are more effective in Asian elephants can help resolve this question.
Acknowledgements This research was supported by the Zurich Zoo and the Department of Zoo Biology of the University of Zurich. I would like to thank Director Dr. Alex Ribel and Prof. Dr. Hans Kummer for their advice and support. Dr. Charles Menzel and Dr. Hans Schmid helped in reviewing this manuscript.
82
C. Wiedenmayer/Applied
Animal Behauiour Science 56 (1998) 77-82
References American Association of Zoo Keepers, 1994. Animal keepers’ forum: special elephant management issue, 21. Bell, W.J., 1991. Searching Behaviour. Chapman & Hall, London. Brown, G.S., Gass, C.L., 1993. Spatial association learning by hummingbirds. Anim. Behav. 46, 487-497. Carlstead, K., Shepherdson, D., 1994. Effects of environmental enrichment on reproduction. Zoo Biol. 13, 447-458. Eltringham, S.K., 1982. Elephants. Blandford Press, Poole. Green, C., 1993. Enriching an elephant’s environment. Shape Enrich. 2, 5-6. Holst, B., 1990. Behavioural enrichment-a catalogue of ideas. Copenhagen Zoo, Denmark. Hutchins, M., Hancocks, D., Crockett, C., 1984. Naturalistic solutions to the behavioural problems of captive animals. Zool. Garten. 54, 28-42. Ings, R., Waran, N.K., Young, R.J., 1997. Effect of wood-pile feeders on the behaviour of captive bush dogs (Speorhos uenaticus). Anim. Welfare 6, 145-152. McKay, G.M., 1973. Behaviour and ecology of the Asiatic elephant in southeastern Ceylon. Smithsonian Contribution to Zoology, 125. Menzel, C.R., 1991. Cognitive aspects of foraging in Japanese monkeys. Anim. Behav. 41, 397-402. Menzel, CR., 1996. Structure-guided foraging in long-tailed macaques. Am. J. Primatol. 38, 117-132. Schmidt, C.R., 1973. New elephant house at Zurich Zoo. Int. Zoo Yearb. 13, 241-243. Shepherdson, D.J., Carlstead, K., Mellen, J.D., Seidensticker, J., 1993. The influence of food presentation on the behaviour of small cats in confined environments. Zoo Biol. 12, 203-216. Sukumar, R., 1989. The Asian Elephants. Cambridge Univ. Press, Cambridge. Vancuylenberg, B.W.B., 1977. Feeding bchaviour of the Asiatic elephant in southeast Sri Lanka in relation to conservation. Biol. Conserv. 12, 33-54.
ELSEVIER
Applied Animal Behaviour
Science 56 (1998) 77-82
Food hiding and enrichment in captive Asian elephants Christoph Wiedenmayer Abteilung Tiergartenbiologie,
Uniuersitiit Ziirich, Ziirichbergstrasse Accepted
* 221, Ziirich 8044, Switzerland
19 June 1997
Abstract Asian elephants (Elephas maximus) kept in zoos usually spend less time foraging than their wild conspecifics. In order to increase foraging in a group of captive Asian elephants, peanuts were hidden above a distinctive outdoor enclosure structure, the stone border. It was expected that the elephants would learn this association and increase food searching in the outdoor enclosure. After training, the elephants searched more above the stone borders than during baseline, which indicates that they learned the relationship between stone borders and peanuts. But hiding food did not enhance searching behaviour. Therefore, this method of food hiding did not represent an environmental enrichment. 0 1998 Elsevier Science B.V. Keywords:
Learning;
Elephants;
Environmental
enrichment
1. Introduction Although Asian elephants (Elephas maximus) have been kept traditionally by humans for hundreds of years, it is still debated how they should be housed in zoos (see American Association of Zoo Keepers, 1994). Wild Asian elephants spend a high proportion of their active time foraging (McKay, 1973; Vancuylenberg, 1977). Foraging requires elephants to locate potential food sources, manipulate them to get access to food and feed on them (Eltringham, 1982). In contrast, in many zoos, food is delivered to the elephants in large, spatially and temporally concentrated amounts which the elephants
* Corresponding author. Developmental Psychobiology, University, 722 W 168th Street Box 40, New York, + 1-212-543-5467; e-mail: cpw [email protected]
College of Physicians and Surgeons of Columbia NY 10032, USA. Tel.: + l-212-543-5706; fax:
0168.1591/98/$19.00 0 1998 Elsevier Science B.V. All rights reserved. PII SO168-1591(97)00091-9
78
C. Wiedenmayer/Applied
Animal Behmiour
Science 56 (1998) 77-82
can exploit very rapidly. Therefore, feeding procedures such as scattering and hiding small edible items in the enclosure have been proposed to increase foraging and are used in several zoos (e.g., Holst, 1990; Green, 1993). However, experimental data on the effect of such environmental enrichment measures in elephants are rare. The aim of the present study was to measure the influence of hidden food on the location and frequency of inspection of the environment by elephants. Food was presented to the elephants along enclosure structures, stone borders, rather than scattered at random, in order to identify some of the cues that they used to organise their search (Bell, 1991). It was hypothesised that (a) the elephants would learn the relationship between food and the border and would orient their searching accordingly, and that (b) this learning process would result in an overall increase in the frequency of food searching behaviour. It was assumed that increased searching is closer to the behaviour of wild elephants and therefore that hidden food presentation can be regarded as enrichment of housing conditions.
2. Methods 2.1. Animals and housing The group at Zurich Zoo consisted of three unrelated, wild-born female elephants, Druk, Chhukha (both 27 yrs) and Ceyla (19 yrs), and the two daughters of Ceyla, Komali (10 yrs) and Panang (5 yrs), both born at Zurich Zoo. They were housed in an elephant exhibit which consisted of an indoor platform (75 m’) and an outdoor enclosure (860 m2) (for details of the exhibit, see Schmidt, 1973). During the night, the elephants stayed indoors. They were given access to the outdoor enclosure in the morning. In the late afternoon, the animals were brought back into the house. They were fed indoors around 17:00 h. Food items such as hay, straw, bread, vegetables, fruits and pellets were presented on the floor of the platform. In addition, once or twice a day a few fresh tree branches were supplied in the outdoor enclosure. During the food hiding experiments there was no additional food available for the elephants in the outdoor enclosure. 2.2. Procedure 2.2.1. Baseline Baseline data were collected on searching behaviour without hidden food present. Before the elephants entered the outdoor enclosure around 10:00 h, the observer walked around the outdoor enclosure without hiding food to control for potential odour cues. Searching behaviour, defined as holding or moving of the trunk disc pointed toward the ground from a distance of < 10 cm, was recorded for each elephant by instantaneous sampling at intervals of 20 s during 1 h/day. This hour immediately followed the release of the elephants into the outdoor enclosure. One-hour observations were repeated on nine days during six weeks in March and April, 1994.
C. Wiedenmayer/Applied
Animal Behaoiour Science 56 (19981 77-82
79
2.2.2. Training The elephants had to learn the association between food and a particular structure of their environment. Stone borders were chosen as structures, because they occurred in four locations in the outdoor enclosure and because the elephants’ locomotion indicated that they also perceived them as distinct features. The stone borders varied in length between 4 m and 13 m, were 20 cm high and consisted of a continuous slightly curved row of stones. Peanuts were chosen as food items, because they were highly preferred by the elephants at Zurich Zoo. In pilot observations, it was found that the elephants could not locate peanuts on the ground visually; peanuts presented in such a way can thus be regarded as hidden. In contrast, apple halves were immediately detected and additionally elicited searching behaviour in their surround. Therefore, to orient the elephants’ searching during training, half an apple was placed in the middle above each stone border to provide a visible cue. A total of 2.5 peanuts was placed above the stone borders on both sides of the four apple-halves in a row at intervals of 1 m. As in the baseline, searching behaviour was recorded for 1 h/day after the elephants entered the outdoor enclosure. When the elephants searched at the upper edge of the stone borders (width of area 30 cm), searching was defined as ‘searching above’; if they searched at the ground below the stone borders (width 30 cm), searching was defined as ‘searching below’. In addition, the rate of finding food items was determined. Food presentation and data collection were carried out on 14 days during seven weeks in May, June and July, 1994. 2.2.3. Testing Searching behaviour was measured after the training. Again, 25 nuts were presented above the stone borders, but without visible cues, the apple-halves. The nuts were presented in the same specific locations as in the training phase. Data were recorded as in the other phases, on seven days distributed irregularly over seven weeks in August and September, 1994.
3. Results 3.1. Orientation
of searching
behaviour
During testing, searching behaviour above the stone borders was significantly increased (Mann-Whitney U-test, two-tailed, Z = -2.40, P < 0.02), in contrast to searching below the stone borders, which did not change significantly (Mann-Whitney U-test, two-tailed, Z = - 1.57, P > 0.1; Table 1). After entering the outdoor enclosure, the elephants spread, walked to the stone borders, and moved their trunk discs along these structures. When an elephant’s trunk disc came close to or touched a nut, she picked it up and ate it. Few social interactions occurred during this searching phase. The elephants found two thirds of the nuts within 10 min (Fig. l), but they did not always find all 25 nuts within 1 h. The locations of the nuts not found varied across trials.
80 Table 1 Searching
C. Wiedenmayer/AppliedAnimalBehauiourScience 56 (1998) 77-82
of the five elephant cows above the stone borders in % of total searching Above stoneborder
Druk Chhukha Ceyla Komali Panang
during baseline and testing
Below stoneborder
Baseline
Testing
Baseline
Testing
3.0 0.0 5.0 3.0 6.7
12.4 9.1 5.3 15.3 22.6
16.0 0.8 10.8 15.1 15.2
2.5 1.1 8.0 9.5 9.0
Fig. 1. Cumulative SD of 14 trials).
percent of nuts found by a group of five elephants during the 60 min of testing (mean and
3.2. Frequency
of searching
behaviour
The frequency of total searching behaviour across baseline, not differ (Kruskal-Wallis test, H = 0.14, P > 0.9; Table 2).
Table 2 Total searching behaviour training and testing
Druk Chhukha Ceyla Komali Panang
of the five elephant
cows in % of the observation
training
and testing did
time during baseline,
Baseline
Training
Testing
6.0 1.6 18.3 16.2 12.7
5.8 3.8 14.1 18.6 13.1
6.3 3.1 13.9 16.7 13.2
during
C. Wiedenmayer/Applied
Animal Behauiour Science 56 (1998) 77-82
4. Discussion
This experiment shows that elephants searched more above the enclosure structure stone border after they had repeatedly found peanuts there. This increase indicates that the elephants learned the relationship between stone borders and peanuts. They appear to have formed a searching rule about where to find food after entering the outdoor enclosure. Although this searching rule oriented their searching behaviour, they did not find all of the nuts in every trial. They did not pick up all nuts because either they could not remember the precise location of every nut, or because they were not motivated to search longer as peanuts may not be very rewarding food stimuli for elephants. Learning is facilitated if the spatial cue and the food are both part of a particular physical structure (Brown and Gass, 1993). A contiguity such as that between the nuts and the stone border is often characteristic of conditions in the wild. Macaques organise their foraging search in relation to the food’s proximity to specific classes of environmental structures such as river edges or trees (Menzel, 1991, 1996). In contrast to macaques, Asian elephants are mainly nonselective bulk feeders on poor quality food such as grass (Vancuylenberg, 1977; Eltringham, 1982). Nevertheless, they also feed on high-quality foods such as fruits, which are located at distinct habitat structures which require selective foraging (McKay, 1973; Sukumar, 1989). Hiding food is thought to mimic natural conditions and to be a form of environmental enrichment (Hutchins et al., 1984; Carlstead and Shepherdson, 1994). In small cats and wild dogs, hiding small food items in wood piles increased exploration not just prior to finding the food, but for some time after it had been found (Shepherdson et al., 1993; Ings et al., 1997). The rationale of the present study was that if elephants found favorite food distributed according to a specific pattern, they would increase their searching, at least during a certain time. Although the elephants learned to search for food, hiding food did not enhance searching behaviour. Nuts elicited a local increase of searching behaviour, but the elephants did not extend their searching to other structures of the enclosure, not even to the lower parts of the stone borders. Either Asian elephants cannot be motivated to search for peanuts during a large proportion of their time due to their nonselective feeding habits, an interpretation supported by the rapid decrease of the finding rate after 10 min, or the association to be learned was too easy to affect the searching behaviour. Future studies designed to test whether other patterns of food hiding or other types of food are more effective in Asian elephants can help resolve this question.
Acknowledgements This research was supported by the Zurich Zoo and the Department of Zoo Biology of the University of Zurich. I would like to thank Director Dr. Alex Ribel and Prof. Dr. Hans Kummer for their advice and support. Dr. Charles Menzel and Dr. Hans Schmid helped in reviewing this manuscript.
82
C. Wiedenmayer/Applied
Animal Behauiour Science 56 (1998) 77-82
References American Association of Zoo Keepers, 1994. Animal keepers’ forum: special elephant management issue, 21. Bell, W.J., 1991. Searching Behaviour. Chapman & Hall, London. Brown, G.S., Gass, C.L., 1993. Spatial association learning by hummingbirds. Anim. Behav. 46, 487-497. Carlstead, K., Shepherdson, D., 1994. Effects of environmental enrichment on reproduction. Zoo Biol. 13, 447-458. Eltringham, S.K., 1982. Elephants. Blandford Press, Poole. Green, C., 1993. Enriching an elephant’s environment. Shape Enrich. 2, 5-6. Holst, B., 1990. Behavioural enrichment-a catalogue of ideas. Copenhagen Zoo, Denmark. Hutchins, M., Hancocks, D., Crockett, C., 1984. Naturalistic solutions to the behavioural problems of captive animals. Zool. Garten. 54, 28-42. Ings, R., Waran, N.K., Young, R.J., 1997. Effect of wood-pile feeders on the behaviour of captive bush dogs (Speorhos uenaticus). Anim. Welfare 6, 145-152. McKay, G.M., 1973. Behaviour and ecology of the Asiatic elephant in southeastern Ceylon. Smithsonian Contribution to Zoology, 125. Menzel, C.R., 1991. Cognitive aspects of foraging in Japanese monkeys. Anim. Behav. 41, 397-402. Menzel, CR., 1996. Structure-guided foraging in long-tailed macaques. Am. J. Primatol. 38, 117-132. Schmidt, C.R., 1973. New elephant house at Zurich Zoo. Int. Zoo Yearb. 13, 241-243. Shepherdson, D.J., Carlstead, K., Mellen, J.D., Seidensticker, J., 1993. The influence of food presentation on the behaviour of small cats in confined environments. Zoo Biol. 12, 203-216. Sukumar, R., 1989. The Asian Elephants. Cambridge Univ. Press, Cambridge. Vancuylenberg, B.W.B., 1977. Feeding bchaviour of the Asiatic elephant in southeast Sri Lanka in relation to conservation. Biol. Conserv. 12, 33-54.