Social roles influence cortisol levels in captive Livingstone's fruit bats (Pteropus livingstonii)

Morgan J Edwards; Christina R Stanley; Charlotte A Hosie; Sarah Richdon; Eluned Price; Dominic Wormell; Tessa E Smith

doi:10.1016/j.yhbeh.2022.105228

Social roles influence cortisol levels in captive Livingstone's fruit bats (Pteropus livingstonii)

Horm Behav. 2022 Aug:144:105228. doi: 10.1016/j.yhbeh.2022.105228. Epub 2022 Jun 27.

Authors

Morgan J Edwards¹, Christina R Stanley², Charlotte A Hosie³, Sarah Richdon⁴, Eluned Price⁵, Dominic Wormell⁶, Tessa E Smith⁷

Affiliations

¹ Animal Behaviour and Welfare Research Group, Department of Biological Sciences, University of Chester, Chester CH1 4BJ, UK. Electronic address: 1821362@chester.ac.uk.
² Animal Behaviour and Welfare Research Group, Department of Biological Sciences, University of Chester, Chester CH1 4BJ, UK. Electronic address: christina.stanley@chester.ac.uk.
³ Animal Behaviour and Welfare Research Group, Department of Biological Sciences, University of Chester, Chester CH1 4BJ, UK. Electronic address: l.hosie@chester.ac.uk.
⁴ Institute of Conservation Science & Learning, Bristol Zoological Society, Clifton, Bristol BS8 3HA, UK. Electronic address: SRichdon@bristolzoo.org.uk.
⁵ Durrell Wildlife Conservation Trust, Trinity, Jersey JE3 6AP, UK. Electronic address: eluned.price@durrell.org.
⁶ Durrell Wildlife Conservation Trust, Trinity, Jersey JE3 6AP, UK. Electronic address: Dominic.Wormell@durrell.org.
⁷ Animal Behaviour and Welfare Research Group, Department of Biological Sciences, University of Chester, Chester CH1 4BJ, UK. Electronic address: tessa.smith@chester.ac.uk.

PMID: 35772196
DOI: 10.1016/j.yhbeh.2022.105228

Abstract

A critical component of conserving and housing species ex situ is an explicit scientific understanding of the physiological underpinnings of their welfare. Cortisol has been repeatedly linked to stress, and therefore used as an indicator of welfare for many species. In order to measure cortisol in the Livingstone's fruit bat (Pteropus livingstonii; a critically endangered keystone species) without disturbing the captive population, we have developed and validated a non-invasive, novel hormone extraction procedure and faecal glucocorticoid assay. A total of 92 faecal samples, 73 from the P. livingstonii breeding colony at Jersey Zoo, Channel Islands and 19 samples from P. livingstonii housed at Bristol Zoological Gardens, UK, have been collected and analyzed. Mixed-effect modelling of the influence of physiological state variables on cortisol concentration revealed that lactating females had higher cortisol levels than non-lactating females, indicating that our assay is measuring biologically relevant hormone concentrations. Males and older bats also had higher cortisol than non-lactating females and younger individuals. Further analysis applied social network methodology to compare the cortisol levels of bats with different social roles. We found that individuals that linked social groups possessed higher than average cortisol levels and conversely, individuals with high-quality, positive relationships had lower cortisol levels. These results demonstrate, for the first time in a bat species, social mediation of stress hormones. Lastly, the frequency of vocalisation was found to positively correlate with cortisol concentration in males, suggesting that this behaviour may be used by animal management as a visual indicator of a bat's hormonal status. Hence, this research has provided unique insights and empirical scientific knowledge regarding the relationship between the physiology and social behaviour of P. livingstonii, therefore allowing for recommendations to be made to optimise bat welfare at the individual level.

Keywords: Conservation; Cortisol; Enzyme-immunoassay; Fruit bats; Non-invasive; Social buffering; Welfare.

MeSH terms

Animals
Animals, Zoo / physiology
Chiroptera* / physiology
Feces
Female
Glucocorticoids
Hydrocortisone
Male

Substances

Glucocorticoids
Hydrocortisone