Sources of variation in fecal cortisol levels in howler monkeys in belize

Abstract

High cortisol levels are known to cause low fecundity and increased mortality; thus, the prospect of using cortisol as a measure of population health is an exciting one. However, because so many factors can interact to influence cortisol release, it can be difficult to interpret what exactly is creating changes to cortisol levels. This study investigates variation in fecal cortisol levels in a population of black howlers (Alouatta pigra) from 350 fecal samples collected from 33 individuals in more than 4 years. A general linear mixed model revealed that cortisol varied significantly with fruit availability and contact with tourists. When fruit availability was low, cortisol increased, likely because when fruit availability is low monkeys eat less fruit, thus obtaining less sugar. This result may simply reflect cortisol's metabolic function of mobilizing glucose. It also indicates that these monkeys may be experiencing periods of food stress throughout the year, which was earlier thought to be minimal for a primarily folivorous species. Presence of tourists was the only other factor found to lead to high cortisol; with exposure to tourists increasing stress levels. These results highlight the importance of understanding how physiological factors can influence cortisol, making it easier to interpret results and determine the external social or ecological stressors that may increase cortisol.

Variation of glucocorticoid metabolite levels is associated with survival demands in immature and reproductive demands in adult wild black capuchins (Sapajus nigritus)

“…If the energy required by the organisms to deal with their routine or with unpredictable events (allostatic load) exceeds the energy they can acquire from the environment, the levels of hormones associated with energy mobilization, such as glucocorticoids (GCs), usually raise to initiate physiological and behavioral changes that promote survival (Sapolsky, Romero, & Munck, 2000;McEwen & Wingfield, 2007;Wingfield & Ramenofsky, 1999). That is why energy intake shortages have been associated with high levels of GCs in several primate species (Alouatta pigra: Behie, Pavelka, & Chapman, 2010;Lemur catta: Cavigelli, 1999;Pan troglodytes: Muller & Wrangham, 2004;Papio anubis: Sapolsky, 1986;Papio ursinus: Weingrill, Gray, Barrett, & Henzi, 2004) and correlated with travel distance (Di Fiore & Suarez, 2007;Girard & Garland, 2002).…”

Behavioural Responses of Yunnan Snub-Nosed Monkeys (Rhinopithecus bieti) to Tourists in a Provisioned Monkey Group in Baimaxueshan Nature Reserve

“…R. bieti responded at different rates to 5 tourist actions (shout, photograph, offer food, clap, and wave). Habituated individuals have greater self-inhibition responses than non-habituated individuals [Fan and Xiang, 2013] as observed in Alouatta pigra , M. sylvanus , P. pygmaeus morio and G. g. gorilla [Behie et al, 2010;Maréchal et al, 2011;Muehlenbein et al, 2012;Shutt, 2014]. Habituated non-human primates change their behaviour to deal with tourist interference in order to protect McKinney, 2014;Maréchal et al, 2016a].…”

Influencia del cautiverio en el comportamiento y en los niveles de cortisol del mono titi gris (Saguinus leucopus)

“…Concentraciones de cortisol (hormona del estrés) en el encierro de Santacruz y de Piscilago y comparación con niveles de cortisol en especies cercanas y primates del viejo mundo como referencia de valores esperados en el género. En conclusión el cortisol puede tener cierto grado de asociación con los comportamientos y esto conduce a pensar, que al no tener las condiciones adecuadas en el encierro los individuos llegan a verse afectados tanto a nivel comportamental como fisiológico como sucedió en el zoológico de Piscilago, donde los monos aunque no eran de exhibición se encontraban ubicados en un sitio de confluencia constante de turistas, a diferencia del encierro de Santacruz, siendo posible afirmar que la presencia de los turistas tiene un efecto significativo en el aumento del cortisol, y que ni el sexo, ni el máximo mensual de la temperatura, influye significativamente en los niveles de esta hormona (Behie et al, 2010).…”