Elevated testosterone levels and social ranks in female rock hyrax

In mammals, males maintain significantly higher testosterone (T, 'the male hormone') levels than females throughout the year and are typically dominant over females. Our study of the cooperatively breeding rock hyrax (Procavia capensis) demonstrated a distinct exception. In most hyrax social groups that we studied, adult females were at the highest social rank within the group and showed higher than or equal T levels to males. To our knowledge, this is the first reported instance of adult female mammals demonstrating higher T levels than adult males. However, although T levels significantly correlated with rank in males, in females such correlations were not detected, suggesting a more complex interplay between behavior and endocrine factors in this species. (C) 2005 Elsevier Inc. All rights reserved.