Meeting Abstract
Captivity is a potent chronic stressor for many wild animals, although different animal species, and different individuals within a species, display wide variation in their tolerance to captivity stress. We previously observed that wild-caught house sparrows (Passer domesticus) increased the frequency of two repetitive behaviors, beak wiping and feather ruffling, with time in captivity. Because repetitive, stereotyped behavior can also be induced through drug-induced stimulation of the dopamine system, we hypothesized that individual variation in D2 dopamine receptors would predict the frequency of stereotyped behaviors in response to captivity stress. We examined D2 receptor availability in striatum using an in vivo imaging technique, positron emission tomography (PET) with the D2 antagonist 11C-raclopride. We found that D2 receptor availability (binding potential) in striatum 24 h after capture predicted the frequency of several behaviors after 1 month in captivity, with individuals with higher D2 binding potential displaying significantly lower overall activity levels and beak wiping (although not feather ruffling) behavior than those with lower D2 binding potential. Furthermore, in the subset of individuals that were imaged a second time, D2 binding potential decreased with time in captivity. Thus, high concentrations of D2 receptors in striatum may make some individuals resilient to the behavioral effects of captivity stress. To the best of our knowledge, this is the first use of PET imaging to quantify brain receptors in any wild animal species, and demonstrates the usefulness of this technique in elucidating how individual variation in neuroendocrine phenotypes can predict behavior.
