Traditionally, testosterone is thought as a male hormone and estrogens as female hormones. However, estrogens and testosterone are produced by both sexes and appear to have important roles in both males and females.  Measuring hormone concentrations in the wild without disturbing the animals is now feasible using non-invasive methods like fecal determination. These methods, however, need careful validation as the circulating hormone is usually degraded into several metabolites and it is necessary to verify that the antibody used in the immunoassay only recognized metabolites of the original hormone.  Because the metabolites excreted in feces may be different for males and females, it is essential to validate immunoassays in both sexes. In this study, we determined whether the radioimmunoassays we previously used to measure fecal testosterone in male baboons and fecal estrogens in female baboons were suitable to measure these hormones in the opposite sex. Read More

There's a new ABRP paper out on predictors of female dominance rank. Dominance rank influences many fitness-related traits in the Amboseli baboons and in other mammalian populations. Therefore, understanding how and why animals attain a given dominance rank is an important goal in behavioral ecology. For female baboons, dominance rank is maternally inherited and generally follows predictable patterns. Specifically, adult daughters attain a rank immediately below their mother, and in reverse age order (a phenomenon known as ‘youngest ascendency’). This pattern of rank inheritance is assumed to be widespread and generally stable in cercopithecine primates; however, few studies have systematically examined whether the rules of female rank inheritance always hold true, and under what circumstances they are violated. Read More

Although females of many taxa display sexual signals as they become ready to be fertilized, little is known about what other types information, if any, may be contained in those signals. Female baboons display one of the most conspicuous signals of fertility in the animal world; exaggerated estrous swellings. These swellings appear on the animal’s hind end during the follicular phase of the sexual cycle, are largest around the period of ovulation, and quickly disappear during the luteal phase. By characterizing several different sources of variance in swelling size, our new study reveals the potential information content in this charismatic trait. Read More