The International Journal of Comparative Psychology is sponsored by the International Society for Comparative Psychology. It is a peer-reviewed open-access digital journal that publishes studies on the evolution and development of behavior in all animal species. It accepts research articles and reviews, letters and audiovisual submissions.
Volume 16, Issue 2, 2003
Over the past several years we have developed a research program to increase knowledge of giant panda behavioral biology to facilitate efforts to reproduce giant pandas in captivity, particularly at the Wolong Breeding Center in Sichuan, China. Studies of estrus and reproductive behavior have enabled us to better pinpoint the timing of the fertile period and evaluate problems when a pair's behavior diverges from the norm. Experiments with chemosignals demonstrate that pandas possess a sophisticated chemical communication system, extracting information about the signaler’s sex, reproductive status, age, social status, and individual identity, as well as the age of the chemosignal. The effects of scent on sexual motivation have important applications for captive breeding. Given the proper behavioral environment, most pandas now mate naturally at Wolong. Following observations documenting several behavioral problems, we developed an environmental enrichment program to reduce abnormal behaviors, encourage behavioral diversity, and promote well being. Females are monitored closely for signs of pregnancy and we are evaluating behavioral and morphological indices to distinguish pregnancy from pseudopregnancy. Identification of pregnant females is important because they are managed differently than nonpregnant females. In cases of maternal abandonment of cubs, we have developed a method to train the mother to accept her cubs. The result of such behavioral research, coupled with efforts by other disciplines and basic husbandry changes, is a dramatic increase in the number of natural matings, pregnancies, births and cub survivorship.
Effects of Captivity on Response to a Novel Environment in the Oldfield Mouse (Peromyscus polionotus subgriseus)
Long-term maintenance of captive populations and release of these animals into the wild is one approach to endangered species conservation. In this study, I used a traditional ethological technique, the open-field test, to assess captivity's effects on exploratory behavior, level of activity, and enclosure use in oldfield mice (Peromyscus polionotus subgriseus) upon introduction to a novel environment. The animals tested were from four populations collected from Ocala National Forest, Florida, and were held in captivity for varying numbers of generations: 35, 14, 2, and 0 (wild caught). The population 35 generations removed from the wild was behaviorally distinct from the other three populations. The mechanisms behind the differences are unclear. This study, however, is an example of how traditional behavioral methods can be applied to conservation problems. Whether captive populations are raised for lab studies or for captive breeding of endangered species, this study suggests that if they have been removed from the wild for more than 14 generations, they are likely to be significantly different from the wild counterparts of interest.
Releasing captive-bred Attwater’s prairie chickens (APC) into an endangered wild population has successfully maintained but has not increased a small extant population. The limited success of the captive-release APC program has been largely attributed to heavy predation on the newly released birds. The poor survival rate of released birds suggests that breeding and rearing in captivity may have a detrimental effect on the expression of predator avoidance behaviors. In Experiment 1, 1- 2 week-old chicks were assessed for fear responses. Tendency to hide, as measured by the hole-in-thewall test, correlated with postrelease survival. In Experiment 2, fear responses, including those identified as important to survival in Experiment 1, were stronger in chicks reared in a seminatural environment relative to chicks reared in an artificial environment. Implications for conservation of this endangered species are discussed.
Training Tammar Wallabies (Macropus eugenii) to Respond to Predators: A Review Linking Experimental Psychology to Conservation
Animals bred in captivity often suffer high levels of predation after release into the wild. Prerelease predator avoidance training has been undertaken to try to improve antipredator skills. Applied research on predator avoidance learning in birds and mammals has not benefited from the empirical findings of extensive basic research, as it has been the case for fish. Consequently, this field has progressed slowly and the utility of prerelease antipredator training as a conservation strategy remains controversial. Here, I report one experiment and review two others that illustrate the way in which principles and experimental designs borrowed from classic studies of animal learning can be used to develop predator avoidance training techniques and to establish the content of learning. Results show that tammar wallabies (Macropus eugenii), an Australian macropodid marsupial, can acquire a fear response that is specific to predators, but that the likelihood of learning is dependent upon subtle details of the training protocol. Differential reinforcement of predator and non-predator stimuli has the potential to enhance the specificity of learning, if necessary. I discuss the implications of these results for the field of predator avoidance training and suggest that a controlled experimental approach, which enables the content of learning to be described, will be the most fruitful for this research area in the long term.
In Experiment 1 underwater visual acuity was assessed in two Florida manatees, Trichechus manatus Latirostris, using grating stimuli in three conditions: Vertical gratings presented in freshwater, vertical gratings in saltwater, and horizontal gratings in saltwater. All stimuli were tested in a free-swimming format from a minimum distance of one meter. Substantial differences were found between the two subjects. One subject’s minimum angles of resolution (MAR) were 56 min for vertical stimuli in freshwater, 38 min for vertical stimuli in saltwater, and 24 min for horizontal grating stimuli in saltwater. When only trials under brightest light conditions were analyzed, MARs improved for vertical stimuli to 24 min in freshwater and 21 min in saltwater. No improvement was found for horizontal stimuli with brighter light conditions. The MARs of the second subject measured over a degree for all test conditions. In Experiment 2 only the first subject was tested from a closer viewing distance. He showed no improvement when allowed to approach targets to within 30 cm. The limited resolution of both subjects and absence of increased acuity at closer distances in one suggests that manatees use vision for intermediate or longer distance inspection of large objects. The disparity in visual resolution between subjects has possible implications for variability in acuity within the species.
Studies focusing on the visual cues sea turtles use to orient between the nesting site and the sea indicate that sea turtles use diffuse images for orientation and are highly myopic on land. The visual environment encountered by sea turtles, however, is very different in water than on land. In this study, operant conditioning techniques were used to explore the visual acuity of juvenile loggerhead sea turtles (Caretta caretta) in the marine environment. Turtles were trained, in a tank setting, to distinguish between a 45 mm striped panel and 50% gray panel by using squid as a food reward. Though the pace of training was limited by our guidelines for holding these animals in captivity and the amount of food we could give each animal in a week, all turtles were trained in under a month. Once training was achieved, the stripes were reduced in size (stripe width ranging from 45.0 – 0.035 mm) until the turtle chose the striped panel over the 50% gray panel based on chance; this level of choice was designated as threshold. Mean acuity threshold level for all turtles tested was found to be 0.078 (visual angle of 12.89 minutes of arc). These results are similar to those of other marine species and indicate that loggerhead sea turtles use distinct visual cues in the aquatic environment.
According to the “lost year” theory of sea turtle development, hatchlings swim offshore in a frenzy until they reach floating weed beds where they live in relative safety for the first few years of life. Direct observations of post hatchlings in nature have been rare, so we utilized very young captive hatchlings presented with open water or artificial weed bed habitats (Experiments 1 and 2). Loggerhead (Caretta caretta) and hawksbill (Eretmochelys imbricate) hatchlings congregated in the weed bed, but green (Chelonia mydas) hatchlings did not. Green hatchlings that were slightly older and presented with sargassum continuously did show more tendency to gather in the weeds, particularly at night (Experiment 3). The young green turtles oriented towards the open ocean and congregated in the end of the tank closest to the ocean and actively avoided weeds (Experiments 4 and 5). When hatchlings were given simulated predation experience the loggerheads and hawksbills remained immobile following prediction, but the greens actively swam away (Experiment 6 and 7). These results suggest that the lost year theory of sea turtle development must be refined to take into account species differences and that different species of post hatchlings in nature may be found in different microhabitats, and reacting differently to potential and actual threat of predation.
Anthropogenic Noise and its Effect on Animal Communication: An Interface Between Comparative Psychology and Conservation Biology
Conservation biology and comparative psychology rarely intersect, in part because conservation biology typically emphasizes populations whereas comparative psychology concentrates on individual organisms. However, both fields could benefit from their integration. Conservation biology can profit from an enhanced understanding of individual-level impacts of habitat alteration and the resulting implications for conservation mitigation strategies. Comparative psychology can gain from increased attention to the mechanisms of adjustment used by organisms to “in vivo experiments” created by anthropogenic change. In this paper, we describe a conceptual framework useful for applying our understanding of animal communication to conservation biology. We then review studies of animal communication with conservation implications, and report our own preliminary work that demonstrates our framework in action.