Non-invasive evaluation of physiological stress hormone responses in a captive population of the greater bilby Macrotis lagotis

Abstract

Captive breeding programs are increasingly being used as a management option for threatened mammals. The greater bilby Macrotis lagotis, for example, is a vulnerable species which is maintained in captivity at several facilities in Australia. Non-invasive evaluation of stress hormones (cortisol in mammals) via excretory metabolites can be used to monitor physiological stress responses of captive individuals. In this study, we validated an enzyme-immunoassay (EIA) to measure cortisol metabolites in fresh faecal samples of adult male and female bilbies (n = 7) held in captivity at the Dreamworld Theme Park, Queensland, Australia. The faecal cortisol EIA was validated via parallelism and the recovery of exogenous cortisol added to pooled faecal extracts (> 99% recovery). Female bilbies had higher average faecal cortisol metabolite concentrations and higher day-today variation than male bilbies; however, there was no relationship with bilby age. Cortisol metabolites for most individuals varied widely through time, with numerous peaks and troughs in response to long-term stressors (illnesses, injury and reproductive issues) and short-term stressors, such as use in shows at Dreamworld or public displays in local schools, manual restraint and short-term veterinary procedures (e.g. general anaesthesia). Overall, the higher mean cortisol metabolite concentrations of individuals suffering long-term stress was related to a greater response to short-term stressors. This suggests an interaction between responses to short-term and long-term stressors which is perhaps due to habituation and/or facilitation of long-term stressors. Non-invasive faecal monitoring of stress hormones could provide further information on the implications of captive breeding programs and the release of animals reared in captivity.

Sight of a Predator Induces a Corticosterone Stress Response and Generates Fear in an Amphibian

“…This short-term increase in corticosterone promotes key changes in behaviour and physiology that enable individuals to cope with stress [6–10]. Some of the key behaviours affected by corticosterone in amphibians and also in other vertebrates (small mammals and lizards) include initiation of hiding and defensive behaviours [11–13], increased locomotor activity [14,15], and increased thermoregulatory behaviour [16,17]. The sight of a predator can induce a corticosterone response in birds [18] and exposure to predator odour can induce corticosterone responses in male Sprague–Dawley rats [19].…”

The relationship between physiological stress and wildlife disease: consequences for health and conservation

“…It is crucial that we characterise how wildlife respond to research and conservation interventions such as capture and handling (de Villiers et al 1995;Narayan et al 2012) and translocation (Kahn et al 2007) to assess risk, minimise harm and increase the efficacy of these activities. For example, it has been suggested that the stress of translocation is associated with increased risk of infectious disease in translocated wildlife (Teixeira et al 2007;Dickens et al 2010;Sainsbury and Vaughan-Higgins 2012), including recrudescence of latent and normally innocuous pathogens as well as increased vulnerability to diseases at the release site to which the translocated animals may not have been previously exposed (Mihok et al 1992).…”

Monitoring physiological stress in semi-free ranging populations of an endangered Australian marsupial, the Greater Bilby (Macrotis lagotis)

“…We analysed bilby fecal extracts for concentrations of FCM using enzyme immunoassay (EIA) previously described for other mammals (Wielebnowski et al 2002;Millspaugh and Washburn 2004), and recently used for a captive subpopulation of the greater bilby (Narayan et al 2012;Evans et al 2013). Laboratory validation was done using accuracyrecovery checks and parallelism.…”

“…This major contraction in range is primarily attributed to predation from introduced species (e.g., red fox [Vulpes vulpes] and feral cats [Felis catus]), habitat destruction through agriculture and competition with introduced herbivores (Moseby et al 2009). Whilst information on the bilby's reproductive biology, anatomy and behaviour are available, literature on its stress physiology is only from single captive population (Narayan et al 2012). There is no information available on FCM levels in semi-wild populations of this marsupial.…”