James E Ayala

Learn More
Long-lived iteroparous species often show aging-related changes in reproduction that may be explained by 2 non-mutually exclusive hypotheses. The terminal investment hypothesis predicts increased female reproductive effort toward the end of the life span, as individuals have little to gain by reserving effort for the future. The senescence hypothesis(More)
Studies of large free-ranging mammals have been revolutionized by non-invasive methods for assessing physiology, which usually involve the measurement of fecal or urinary biomarkers. However, such techniques are limited by numerous factors. To expand the range of physiological variables measurable non-invasively from free-ranging primates, we developed(More)
The hypothalamic-pituitary-adrenal (HPA) axis modulates individuals' physiological responses to social stress, which is an inevitable aspect of the daily lives of group-living animals. Previous nonhuman primate studies have reported that sex, age, rank, and reproductive condition influence cortisol levels under stressful conditions. In this study we(More)
Several primate species show sexual dichromatism with males displaying conspicuous coloration of the pelage or skin. Studies of scrotal coloration in male vervet monkeys (Chlorocebus aethiops) suggest that it is an important intrasexual signal, with relatively dark, colourful males dominating paler males. To date, no studies have examined the influence of(More)
The aim of this study was to determine the metabolic response in giant pandas (Ailuropoda melanoleuca) to the consumption of certain parts of bamboo above ground growth. Giant pandas were provisioned with three species of bamboo: Phyllostachys bissetii, of which they only consume the culm (culm group); Bashania fargesii, of which they only consume the(More)
  • 1