Patterns of exploratory behavior in the spiny mouse, Acomys cahirinus

The present paper reports an investigation of patterns of exploratory behavior shown by laboratory-bred Spiny Mice (Acomys cahirinus) when given access to a large, novel arena. The aim was to test hypotheses suggested by our previous work with this species. Previous experiments in which the exploratory behavior of Acomys was compared with that of Mus had suggested that each species had a characteristic pattern of emergence and exploration. The present experiment addressed the question of whether the exploratory patterns of Acomys could be predicted from patterns of emergence as suggested by earlier experiments. Data are presented which indicate that the exploratory behavior of Acomys in a large, novel arena is reasonably predictable. The data presented include measures of the animal's responses to different stimuli within the novel environment, including novel, conspicuous objects, food sources, and the holding cage to which the animal could return. In addition, the patterns of movement through different areas of the environment were recorded in relation to the behavior of the animal when it was first given access to the arena. The data indicate that there are two types of strategy, or patterns, by which Acomys begin to explore a novel environment. The first type consists of a delayed emergence into the arena, followed by brief excursions into the area immediately adjacent to the holding cage, interspersed with longer periods of returns to the holding cage. The second type involves immediate emergence, followed by rapid "dashes" around the periphery of the arena. Which of the two strategies is adopted appears to depend upon the animal's behavior at the time of initial access. Two subsequent experiments considered these strategies further. Experiment 2 indicated that Type I was more characteristic of males and Type II more characteristic of females, although there were no differences related to the female estrous cycle. In Experiment 3, the patterns of exploration over four consecutive tests were investigated. It was found that the strategy adopted by an individual is likely to be consistent across tests.