Fecal Glucocorticoid Measurements and Their Relation to Rearing, Behavior, and Environmental Factors in the Population of Pileated Gibbons (Hylobates pileatus) Held in European Zoos

Abstract

Pileated gibbons (Hylobates pileatus) are rated as endangered according to the International Union of Conservation of Nature (IUCN) Red List. The captive population suffers from poor breeding success and is threatened to become overaged. Although several factors are likely to contribute to the poor breeding success, one in particular may be chronic stress associated with prolonged periods of high glucocorticoid (GC) output. We investigated fecal GC levels of pileated gibbons (Hylobates pileatus) and their relationship to specific life-history variables and environmental factors. After validation of an enzyme immunoassay for the measurement of 5-reduced 3α,11β-dihydroxy cortisol metabolites to assess GC output reliably in pileated gibbons, we collected fecal samples over several days from all 36 European adult pileated gibbons located in 11 institutions and compared Int GC levels to intrinsic individual parameters, husbandry, behavior, and breeding history. Age, sex, and origin (wild vs. captive born) had no effect on GC levels. However, unnaturally reared gibbons had higher GC levels and showed more behavioral abnormalities than parent-reared individuals. Further, nonreproducing gibbons living in a pair without infants had higher GC concentrations than gibbons living in a family, bachelor group, or as singletons. With respect to environmental factors, a large size of the inside enclosure and the existence of visual protection from visitors was associated with lower fecal GC output. The data indicate that rearing and housing conditions appear to correlate to GC levels in pileated gibbons housed under captive conditions. It is hoped this knowledge will support the future management of the species in captivity and thus lead to a more successful breeding of this endangered primate.

The Effect of Fission–Fusion Zoo Housing on Hormonal and Behavioral Indicators of Stress in Bornean Orangutans (Pongo pygmaeus)

“…We measured glucocorticoid concentrations in fecal samples using a group-specific enzyme immunoassay (EIA) for 11ß-hydroxyetiocholanolone designed to measure 3α,11β-dihydroxylated cortisol metabolites (Ganswindt et al 2003;Heistermann et al 2006). Previous studies have used this assay successfully to monitor adrenocortical activity in several primate species of all major taxa, including great apes (Fichtel et al 2007;Girard-Buttoz et al 2009;Heistermann et al 2006;Ostner et al 2008;Pirovino et al 2011). The assay has also been validated for use in orangutans (Weingrill et al 2011).…”

“…It is, therefore, important that management should strive to reduce interactions between visitors and orangutans, as this may lead to a state of chronic stress, which can have marked negative effects on an animal's health and reproduction (Cyr and Romero 2009;Sheriff et al 2011;Wingfield and Romero 2001). Several studies have shown that visitor presence is a stressor for captive primates, from which these individuals try to retreat if possible (Pirovino et al 2011;Smith and Kuhar 2010). Colored glass elements in the windows prevent the orangutans from seeing people standing in the visitor room to some extent in Apenheul.…”

“…Moreover, the floor level of the public area is elevated in comparison with the ground level of the orangutan enclosures, allowing visitors to observe the orangutans at the same height. This might be problematic, as arboreal primates seem to be particularly sensitive to unrestricted visual contact with humans at eye level (Davis et al 2005;Pirovino et al 2011;Smith and Kuhar 2010). Orangutans may interpret gazing by visitors as threatening because it is uncommon for orangutans to look directly at another individual.…”

“…This dilemma could be reduced by lowering the height of viewing areas or increasing the height of cages to reduce the stressful effect of visitors (Pirovino et al 2011). This may not be feasible in Apenheul.…”

“…Various methods exist for improving housing conditions of zoo animals to minimize potential stress. Environmental enrichment, such as adding soil and vegetation or providing animals with special feeding devices, toys, and other novel objects, have become common practice in most zoos (Swaisgood and Sheperdson 2005;Vasconcellos et al 2009) and have been shown to reduce stress hormone (glucocorticoid) output (Boinski et al 1999;Buijs et al 2011;Moreira et al 2007;Pirovino et al 2011). Moreover, many modern keeping facilities provide hiding places that allow animals to withdraw from the sight of conspecifics, visitors, or keepers.…”