The neophobia-optimality explanation of contrafreeloading rats: a reassessment

Environmental enrichment for a mixed-species nocturnal mammal exhibit

Environmental enrichment (EE) is an integral aspect of modern zoo animal management but, empirical evaluation of it is biased toward species housed in single-species groups. Nocturnal houses, where several nocturnal species are housed together, are particularly overlooked. This study investigated whether three species (nine-banded armadillos, Dasypus novemcinctus; Senegal bush babies, Galago senegalensis; two-toed sloths, Choloepus didactylus) in the nocturnal house at Paignton Zoo Environmental Park, UK could be enriched using food-based and sensory EE. Subjects were an adult male and female of each species. EE was deemed effective if it promoted target species-typical behaviors, behavioral diversity, and increased use of enriched exhibit zones. Results from generalized linear mixed models demonstrated that food-based EE elicited the most positive behavioral effects across species. One set of food-based EEs (Kong®, termite mound and hanging food) presented together was associated with a significant increase in species-typical behaviors, increased behavioral diversity, and increased use of enriched exhibit zones in armadillos and bush babies. Although one type of sensory EE (scented pine cones) increased overall exhibit use in all species, the other (rainforest sounds) was linked to a significant decrease in species-typical behavior in bush babies and sloths. There were no intra or interspecies conflicts over EE, and commensalism occurred between armadillos and bush babies. Our data demonstrate that simple food-based and sensory EE can promote positive behavioral changes in a mixed-species nocturnal mammal exhibit. We suggest that both food and sensory EE presented concurrently will maximize opportunities for naturalistic activity in all species.

REGULAR ARTICLES / ARTICLES RÉGULIERSThe effects of refuse-feeding on home-range use, group size, and intergroup encounters in the banded mongoose

The effects of food availability and distribution on population dynamics have been the subject of numerous experimental studies, but no study has quantified the effects of a concentrated supplementary food supply on groups of a social carnivore. We investigated the effects of refuse-feeding at garbage dumps on banded mongoose (Mungos mungo) groups. Garbage dumps represent a reliable, concentrated source of food. Data were collected from three refuse and seven nonrefuse-feeding groups in Queen Elizabeth National Park, Uganda. Groups were located using radiotelemetry, and home-range size and use, group size and population density, and intergroup encounter rate were analysed. Although refuse-feeding groups had home ranges similar in size to those of nonrefuse-feeding groups, their home-range use was more concentrated and their core areas always included the available predictable garbage dumps. Two of the three refuse-feeding groups were larger and denser than other groups. The two groups that shared the same garbage dump had significantly higher intergroup encounter rates than all other groups and their encounters occurred at the shared dump.

Free food or earned food? A review and fuzzy model of contrafreeloading

Animals will work (e.g. lever press) for 'earned' food even though identical 'free' food can easily be obtained from a nearby dish. This phenomenon, called contrafreeloading, appears to contradict a basic tenet of most learning, motivation and optimal foraging theories; namely that animals strive to maximize the ratio of reward, or benefit, to effort, or cost. This paper reviews the factors that have been found to affect the level of contrafreeloading, to try to explain the behaviour. In experiments involving intensive training, contrafreeloading may be explained on the basis of secondary reinforcement and/or differential exposure to the alternative food sources. However, contrafreeloading also occurs without prior training. Contrafreeloading declines with increasing hunger and with increases in the effort required to obtain the earned food: it also has an inverted-U relationship with the degree of stimulus change associated with the earned food. A fuzzy logic model is developed to predict the outcome of interactions between these factors. The model successfully simulates previous empirical findings and provides novel, testable predictions. It is argued that contrafreeloading does not contradict reinforcement theory, provided that the sensory reinforcement obtained from stimuli associated with the earned food is also taken into account. A functional explanation of why such stimuli are reinforcing, and of contrafreeloading itself, is based upon the advantage of gathering information for animals living in changing environments (i.e. an information primacy model). Animals work for earned food in order to update their estimate of a currently sub-optimal food source because, in the longer term, it may unpredictably become the optimal place to feed. Contrafreeloading is therefore a behaviour that, under natural conditions, is adaptive.

[Not Available]

Since Jensen (1963), the phenomenon of "contrafreeloading" corresponds to the fact that animals which have been conditioned to perform a task (by skinnerian conditioning for instance) continue to behave as they have been taught to even when a more simple and effortless solution is made available to them (for instance free access to abundant food in skinnerian situation). This behaviour has been considered as an exception to the "law of the least effort" (Tolman, 1955). To explain it, two types of theories have been put forward. The first one assumes the existence of positive reinforcers connected with the acquired activity, the other one of aversive stimulus connected with the most effortless solution (such as neophobia in the case of cup of abundant food). A reconsideration of the analysis of operant behaviour has led us to take into account the localisation of reinforcing agents and to integrate it in our experiments. The results that have been obtained cannot be accounted for by the theories mentioned above.