THE EFFECTS OF FORAGING DEVICES AS ENRICHMENT IN CAPTIVE WALRUSES ( ODOBENUS ROSMARUS ).

1. THE EFFECTS OF FORAGING DEVICES AS ENRICHMENT IN CAPTIVE WALRUSES (ODOBENUS ROSMARUS). Sarah R. Pickens, M. Faye Parmer, Mike A. Tamborski, Eduardo J. Fernandez, and William Timberlake Department of Psychology, Indiana University and the Indianapolis Zoo INTRODUCTION Stereotypies have been defined as repetitive, invariant behavior patterns with no obvious goal or function (Mason, 1991). They typically occur in captive settings such as zoos and aquariums, and have various forms, such as circle swimming or land pacing bouts, regurgitation and reingestion, and repetitive grooming (Forthman & Ogden, 1992; Shepherdson, Carlstead, Mellen, & Seidensticker, 1993). While there is debate over the cause of stereotypic activity, natural foraging strategies appear to be directly involved. In captivity, many species of animals spend considerably less time searching for food, since processed diets are often delivered at predictable times of the day (Carlstead, Seidensticker, and Baldwin, 1991). The use of enrichment provides additional ways for animals to forage, and has led to significant reductions in stereotypic activity and other aberrant behaviors (Mellen & MacPhee, 2001). In the wild, walruses swim along the sea floor, searching for molluscs (Nelson & Johnson, 1987). Once a mollusc is found, strong suction is used to remove it from the shell (Kastelein & Mosterd, 1989). Therefore, we hypothesized that mats filled with food would emulate a natural foraging context, and therefore reduce stereotypies and increase general activity. CONCLUSIONS Few differences were observed between the morning baseline and afternoon sessions. This suggests that walrus activity was relatively stable over the course of the day, even during experimental conditions. Nereus, the adolescent male, engaged in significantly less stereotypies and more active and other behaviors compared to the 2 adult walruses. All 3 walruses showed a significant increase in mat contact during the MF condition compared to the M condition. Brutus engaged in significantly less stereotypies and more active behaviors during the MF condition in the 1st ½ hour, while Aurora showed a similar trend, except in the F condition and during the full hour of morning observations. The fact that the two conditions enriched differently is likely due to the form and function of each walrus’ stereotypic activity. Brutus spent most of his stereotypies flipper sucking (71%), while Aurora engaged more in circle swimming (92%). Overall, the study provided significant but short-lived reductions in stereotypic activity for the 2 adult walruses. It also demonstrated the need for individualized strategies of enrichment, based on the function of stereotypic and general activity of the exhibited animals. Figure 1 (left) shows the mean percentage of occurrence for each class of behavior between the morning and afternoon sessions for all three walruses. Figure 2 (right) displays the the mean percentage of mat contact for all three walruses during the two conditions in which the mat was present (M and MF). The top graph shows the first ½ hour after the mat was introduced, while the bottom graph shows the second ½ hour after the mat was introduced. Brutus Aurora Nereus METHODS The subjects were three walruses, Brutus (adult male, 2,371 lbs, 18-years-old), Aurora (adult female, 1,418 lbs, 10-years-old), and Nereus (adolescent male, 520 lbs, 2-years-old). Fifteen behaviors across 5 different classes of behavior were measured. Instantaneous time samples were taken every 15 s for 1 hour during the morning (between 10:30 am and noon) or the afternoon (between 1:45 – 3:15 pm). Observation sessions occurred twice a week, on Saturdays and Sundays. A within-subject reversal design was used for the four following conditions: Baseline (BL) – No introduction of mat or food. Mat alone (M) – Two 1.5 m x 1 m x 10 cm mats were introduced at the beginning of the morning observation. Mat w/ food (MF) – Both mats introduced with 30 capelin, 10 herring, and 10 clams stuffed in the mats. Food alone (F) – Same amount of food, but with the food being dumped alone at the beginning of the morning session. REFERENCES Carlstead, K., Seidensticker, J., & Baldwin, R. (1991). Environmental enrichment for zoo bears. Zoo Biology, 10, 3 – 16. Forthman, D. L., & Ogden, J. J. (1992). The role of applied behavior analysis in zoo management: today and tomorrow. Journal of Applied Behavior Analysis, 25, 647 – 652. Kastelein, R. A., & Mosterd, P. (1989). The excavation technique for molluscs of Pacific walruses (Odobenus rosmarus divergens) under controlled conditions. Aquatic Mammals, 15, 3 – 5. Mason, G. J. (1991). Stereotypies: a critical review. Animal Behavior, 41, 1015 – 1037. Mellen, J., & MacPhee, M. S. (2001). Philosophy of environmental enrichment: past, present, and future. Zoo Biology, 20, 211-226. Nelson, C. H., & Johnson, K. R. (1987). Whales and walruses as tillers of the sea floor. Scientific American, 256, 112 – 117. Shepherdson, D. J., Carlstead, K., Mellen, J. D., & Seidensticker, J. (1993). The influence of food presentation on the behavior of small cats in confined environments. Zoo Biology, 12, 203 – 216. Figure 3 (left) shows the mean percentage of occurrence for each class of behavior across all four conditions (BL, M, MF, and F) for all three walruses. This is for the first ½ hour after each condition was implemented. Figure 4 (right) displays the same information as figure 3, except that this is for the second ½ hour after each condition was implemented. For all four graphs, solid lines and stars represent statistically significant results (p < .05), while dotted lines and stars represent results that approached significance (p < .10).