Warmer springs may cause animals to become mistimed if advances of spring timing, including available resources and of timing of breeding occur at different speed. We used thermal sums (cumulative sum of degree days) during spring to describe the thermal progression (timing) of spring and investigate its relationship to breeding phenology and demography of a long-distant migrant bird, the north...

This study examines factors affecting androgen and cortisol levels in wild, male golden lion tamarins (Leontopithecus rosalia). Golden lion tamarins are a cooperatively breeding species in which groups often contain two potentially breeding males. Brothers frequently emigrate together and develop a clear dominance hierarchy, but interactions between them are primarily affiliative. Duos in which...

The effects of chronic stressors on glucocorticoid levels are well described in laboratory rodents, but far less is known about the effects of chronic stressors on wild animals or on dehydroepiandrosterone (DHEA) levels. DHEA can be produced by the adrenal cortex and has prominent antiglucocorticoid properties. Here, we examined wild songbirds to elucidate the relationship between chronic preda...

Thewhite-lipped peccaryTayassu pecari is a social ungulate that forms the largest groups documented for any tropical forest ungulate species. Since the 1950s the species has become increasingly rare in Mesoamerica, and the more frequent reporting of smaller groups may be related to increased hunting pressure. Here we address the conservation status of this species in terms of its group size and...

The behavior of territorial males in a polygynous mating species may be influenced by a variety of factors related to site-specific conditions. In this paper, the behavioral dynamics of territorial male California sea lions (Zalophus californianus) are characterized throughout the breeding season and across rookery sites at Los Islotes Island in the Gulf of California, Mexico. Observations focu...