Abstract
Captive breeding is vital for primate conservation, with modern zoos serving a crucial role in breeding populations of threatened species and educating the general public. However, captive populations can experience welfare issues that may also undermine their reproductive success. To enhance the wellbeing of endangered zoo primates, we conducted a study to assess the effects of a new scent enrichment program on captive red-ruffed lemurs (Varecia rubra), black howler monkeys (Alouatta caraya), siamangs (Symphalangus syndactylus), lar gibbons (Hylobates lar) and orangutans (Pongo pygmaeus pygmaeus). We combined behavioral observations and fecal endocrinology analyses to evaluate the effects of a series of essential oils (benzoin, lavender, lemongrass) on five captive troops (N = 19) housed at Dudley Zoo & Castle and Twycross Zoo (UK). We recorded observations of natural species-specific and abnormal stress-related behaviors for 480 h using instantaneous scan sampling. We collected 189 fecal samples and measured the fecal cortisol concentrations using radioimmunoassay. We found a significant effect of the scent enrichment on behaviors, with red-ruffed lemurs and black howler monkeys reducing their social interactions, as well as red-ruffed lemurs and lar gibbons decreasing their stress-related behaviors after they were exposed to the series of essential oils. We also found that red-ruffed lemurs displayed a significant increase in fecal glucocorticoids following exposure to essential oils. Our contradictory findings suggest that the effects of this series of essential oils may change depending on the species-specific social lives and olfactory repertoires of primates. In conclusion, we cannot recommend using these essential oils widely with zoo primates without additional evaluation.
Highlights
Almost half of the total primate species recognized today worldwide are classified as endangered or critically endangered in the wild, primarily due to human activities (Estrada et al, 2017)
We studied five captive troops of red‐ruffed lemurs, black howler monkeys, siamangs, lar gibbons, and orangutans housed at Dudley Zoo & Castle and Twycross Zoo in the United Kingdom
The linear mixed model (LMM) analysis examining the effect of scent enrichment on social behavior among howler monkeys, orangutans and siamangs revealed a significant effect of enrichment condition on rates of social behavior among these species (Table 4), with eight out of the 11 subjects studied exhibiting a decrease in social behavior after the introduction of scent enrichment (Figure 1)
Summary
Almost half of the total primate species recognized today worldwide are classified as endangered or critically endangered in the wild, primarily due to human activities (Estrada et al, 2017). Zoos may play a major role (Mellor et al, 2015) as zoo animal populations are usually managed to educate the public regarding wildlife and their habitats and to preserve endangered species through captive breeding and reintroduction programs (Schulte‐Hostedde & Mastromonaco, 2015). Captive populations, potentially serving as buffers against extinction, experience problems that impair them from being viable for reintroduction into the wild. Zoo animal populations face reproductive challenges which have so far inhibited them from serving as viable “reserve populations” (Meier, 2016). R. Hosey, 2005) that may undermine their individual welfare and their breeding success
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