| Popis: |
Stress provokes an adaptive strategy that mobilizes the body for acute physical challenges. However, chronic stress has detrimental effects that can reduce health and reproductive fitness. Thus, coping mechanisms are valuable in reducing chronic stress. One such mechanism, the “tend-and-befriend” strategy, refers to affiliation between females as an adaptive strategy to deal with stress. This mechanism is proposed to be a widespread strategy throughout the primate order, and one that underlies patterns of female bonding in humans. Although this strategy has been documented in matrilineal primates characterized by female kinship bonds, there has not been documentation of this strategy among unrelated females. Such documentation is necessary to demonstrate that this strategy is unrelated to female philopatry. Since our hominid ancestors are presumed to be male-philopatric, examining if this strategy applies to unrelated females is essential to understanding the evolutionary context of this mechanism. Here, I examine the tend-and-befriend strategy in a species characterized by fission-fusion social organization and female dispersal. I examine the patterns of female-female social relationships, male aggression, and ecological variables on glucocorticoid concentrations, a measure of physiological stress, among female black-handed spider monkeys. Behavioral, hormonal and ecological data were collected in a wild, habituated community. I validated a cortisol assay for black-handed spider monkeys, and determined that cortisol concentrations do not significantly vary between reproductive states. The only activity variable or ecological variable that was significantly associated was time engaged in rest, with rest and cortisol concentrations inversely related. I found that affiliative behavior was significantly correlated with cortisol concentrations. I further found that females engaged in higher rates of affiliative behavior on days when fecal samples with high cortisol concentrations were collected. Most females exhibited a pattern of low cortisol concentrations punctuated by spikes in cortisol that returned to baseline, rather than chronically elevated cortisol concentrations. I found that patterns of association and affiliation were highly variable, and that rates of affiliative behavior were significantly correlated with association indices. I conclude that these patterns indicate that female spider monkeys are engaging in high rates of affiliative behavior when they are experiencing stress, and that engaging in affiliation brings cortisol concentrations back to baseline values. This research has direct implications for understanding the evolution of the stress response, and whether bonding among unrelated females is a result of ancestral tendencies within the primate order or a more derived feature limited to certain taxa. |
