Annual physiological changes in individually housed squirrel monkeys (Saimiri sciureus)

Abstract

This study investigated whether annual changes in physiology occur in individually housed squirrel monkeys (Saimiri sciureus). Physiological measures were monitored for 20 months. Over the course of the study, all individually housed males and females exhibited clear annual changes in gonadal and adrenal hormone levels, and males exhibited species‐typical changes in body weight. Females exhibited a typical pattern of hormonal changes, with elevations in gonadal steroids occurring during the same months as elevations in cortisol. Males, however, exhibited an atypical pattern, as elevations in hormone levels were not synchronized with each other; rather, elevations in testosterone occurred out of phase with changes in cortisol and body weight. The timing of annual events in individually housed subjects was compared to that in nearby social groups, in which the timing of the breeding season from year to year was determined by social group formations and was outside the naturally occurring breeding season. Elevations of ovarian and adrenocortical hormones in individually housed females were synchronized with indices of breeding in heterosexual social groups. Similarly, weight gain in males was associated with elevations in cortisol and, as with socially housed males, tended to precede seasonal breeding in the social groups. In contrast, annual testosterone elevations for individually housed males were not synchronized with breeding in nearby social groups. We conclude that direct physical interaction is not required for the annual expression of breeding readiness. Synchrony of seasonality among squirrel monkeys may be accomplished by distant social cues in females, but males may require physical interaction for complete synchrony of annual physiological changes. Am. J. Primatol. 47:93–103, 1999. © 1999 Wiley‐Liss, Inc.

Habitat Degradation and Seasonality Affect Physiological Stress Levels of Eulemur collaris in Littoral Forest Fragments

“…This is in accordance with findings on other primates (e.g. South-american squirrel monkeys, Saimiri sciureus , [93], [94]) and mammals (e.g. giant pandas, Ailuropoda melanoleuca , [95], [96]) where the GC elevation has been attributed to the effects of ovarian cycling and general anxiousness.…”

Rearing environment and hypothalamic-pituitary-adrenal regulation in young rhesus monkeys (Macaca mulatta)

“…Often, it is considered a proxy measure of stress and/or animal well-being. The results from the present study, however, along with previous studies in our laboratory (Bentson, Capitanio, & Mendoza, 2003;Capitanio et al, 1998a,b;Capitanio et al, 2004;Mendoza et al, 2000;Mendoza, Lyons, & Saltzman, 1991;Ruys, Mendoza, & Capitanio, 2004) indicate that cortisol concentrations are affected by a number of factors that can exert both main effects and interactions with each other: current social situation, rearing history, sex, age, personality, prior experience with both the blood collection process and other stressful manipulations, as well as with circadian and circannual (Schiml, Mendoza, Saltzman, Lyons, & Mason, 1999) factors. In addition, cortisol concentrations can reflect the animal's perception of the stressful event, a factor that is likely to be related to some of the aforementioned factors (such as personality, age, rearing history).…”

Cognitive Correlates of White Matter Growth and Stress Hormones in Female Squirrel Monkey Adults

“…Three months after the cognitive tests, plasma cortisol and adrenocorticotropic hormone (ACTH) responses evoked by a standardized test were measured in the squirrel monkey nonbreeding season. At this point, circannual rhythms in adrenal and gonadal steroid hormones in squirrel monkeys are at their nadir (Schiml et al, 1999). Cage mates were restrained adjacent to one another for 30 min in separate primate chairs, like those first described by Carmichael and MacLean (1961).…”