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

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 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 primat

Fecal glucocorticoid measurements and their relation to rearing, behaviour and environmental factors in the European pileated gibbon population (Hylobates pileatus)

Die vorliegende Studie validierte die Glucocorticoid (GC) Messung im Kot von Kappengibbons (Hylobates pileatus) und vergleicht die gemessenen Werte der Europäischen Zuchtpopulation mit spezifischen individuellen Variablen und Umweltfaktoren. Durch einen ACTH Stimulationstest und einen induzierten Transportstress erwies sich ein Enzymimmunoassay für die Bestimmung des 5-reduktase 3α,11β-dihydroxy-Cortisolmetaboliten als zuverlässigste Methode für die Messung von GC Werten in Kappengibbons. Für die Vergleichsanalysen wurden über mehrere Tage der Kot von allen 36 (22.14) adulten europäischen Kappengibbons aus 11 verschiedenen Institutionen gesammelt, die GC Werte bestimmt und mit den gesammelten Tier- und Haltungsdaten statistisch verglichen. Handaufgezogene Tiere hatten höhere GC Werte und zeigten mehr Verhaltensabnormalitäten als von den Eltern aufgezogene Tiere. Nicht-reproduzierende Gibbons, die in einem Paar ohne Nachwuchs lebten, hatten höhere GC Konzentrationen als Gibbons, die in einer Familie, als Junggesellen-Gruppe oder als Einzeltiere lebten. Bei den Umweltfaktoren war ein grosses Innengehege und Gehege mit Sichtschutz gegenüber von Besuchern mit tieferen GC Werten assoziiert. Diese Daten zeigen, dass Aufzucht- und Haltungsbedingungen mit den GC Werten von Kappengibbons in Menschenhand korrelieren. Dieses Wissen sollte das zukünftige Management der Spezies in Menschenhand unterstützen und zu einer erfolgreicheren Nachzucht dieser bedrohten Primatenart führen. Quantifying effects of husbandry conditions on the physiology of zoo animals is an important part of assessing husbandry success. This study investigates fecal glucocorticoid (GC) levels of pileated gibbons (Hylobates pileatus) and its relationship to specific life-history variables and environmental factors. Following the validation of an enzyme immunoassay for the measurement of 5-reduced 3α,11ß-dihydroxy cortisol metabolites to reliably assess GC output in the pileated gibbon, we collected fecal samples over several days from all 36 (22.14) European adult pileated gibbons located in 11 institutions and compared GC levels with respect to intrinsic individual parameters, husbandry, behavior and breeding history. Hand-reared animals had higher GC hormone levels and showed more behavioral abnormalities than parent-reared animals. Furthermore, non-reproducing gibbons living in a pair without infants had higher GC concentrations than gibbons living in a family, bachelor group or as singleton. 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 be correlated to GC levels in pileated gibbons housed under captive conditions. This knowledge will hopefully support the future management of the species in captivity and thus lead to a more successful breeding of this endangered primate