A captive population in crisis: Testing hypotheses for reproductive failure in captive-born southern white rhinoceros females

The captive southern white rhinoceros (Ceratotherium simum simum) population is not self-sustaining. Many founders reproduced, but reproduction among captive-born (F-1) females has been extremely sluggish. Thus the conservation breeding program for this species faces a looming crisis. Using behavioral observations of a large captive population and a questionnaire survey circulated to facilities worldwide, several hypotheses for F-1 female reproductive failure were evaluated. Counter to predictions regarding behavioral deficiency in sociosexual behaviors, F-1 females were at least as proficient as F-0 females for all behavioral measures. Males also showed no sociosexual preferences for F-0 over F-1 females. Results indicate that most reproductive failure occurs post-copulation. The reigning root-cause hypothesis for F-1 female reproductive failure postulates that F-0 females are behaviorally dominant and suppress reproduction in F-1 females. However, no evidence for behavioral dominance was found and F-1 females housed with F-0 females were more likely to reproduce than those housed without F-0 females. Such social facilitation of reproduction is beneficial to F-1 female reproduction, but does not explain differential reproduction between F-1 and F-0 females. Because the design controlled for current conditions, these results point to development in captivity as the root cause of postcopulatory reproductive failure in F-1 females. (c) 2005 Elsevier Ltd. All rights reserved.