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

Abstract

Rapid and reliable physiological evaluation of stress is necessary for understanding the potential impacts of environmental changes on managed populations of threatened mammals. In situ populations of Australia's iconic marsupial, the greater bilby (Macrotis lagotis), are nearing extinction due to the impacts of competition and predation by feral animals and unpredictable climatic events (summer heat waves). In this study, we focussed our aim to identify a non-invasive method to measure adrenal activity in the species and also to identify potential factors that should be considered when comparing physiological stress in semi-free ranging populations of the species. We validated an enzyme immunoassay (EIA) for detecting fecal cortisol metabolites (FCM) from fresh fecal pellets taken from bilbies within four captive sites and two semi-free ranging populations around Queensland and New South Wales, Australia. Our FCM EIA successfully detected the 'raise and fall' pattern of FCM levels within 3 days of exogenous adrenocorticotropic hormone (ACTH) challenge. Mean FCM levels differed significantly between the captive sites and between sexes. All male bilbies grouped outdoor in captivity expressed the highest mean FCM level in comparison to all captive males that were housed individually or as groups indoors. Also, semi-free ranging bilbies expressed higher mean FCM levels than the captive bilbies. Overall, our study successfully validated a non-invasive tool for monitoring physiological stress in the greater bilby. In the future, it will be worthwhile to consider factors such as housing conditions, sex and location when comparing the adrenal sensitivity to environmental changes, to help evaluate the success of management interventions (such as predator free enclosures) and support the survival of the species.

The effect of pre‐release captivity on the stress physiology of a reintroduced population of wild eastern bettongs

“…This trend was primarily driven by changes within the delayed‐release group which suggests that this group was experiencing a stronger physiological response to the translocation. The difference at release suggests that FGM concentrations were higher in captivity than in Tasmania, which contrasts with the indication that captive‐bred populations of greater bilbies ( Macrotis lagotis ) have lower GCs, compared to ‘semi‐wild’ populations within fenced reserves similar to MFWS (Narayan, Evans & Hero, ). These results suggest that origin (wild‐bred vs captive‐bred), and environmental familiarity can have a strong influence on stress physiology, reinforcing the need to tailor reintroduction processes to specific projects (Parker et al ., ; Moseby, Hill & Lavery, ).…”

Non-invasive monitoring of adrenocortical physiology in a threatened Australian marsupial, the western quoll (Dasyurus geoffroii)

“…, 2017), the southern brown bandicoot ( Isoodon obesulus ) (Dowle et al. , 2013), and the greater bilby ( Macrotis lagotis ) (Narayan , et al. , 2014), as well as in a range of eutherian mammals including the common marmoset ( Callithrix jacchus ) (Ferreira Raminelli , et al.…”

“…, 2017; Hogan et al. , 2011; Narayan et al. , 2014), we considered any peaks within the first 4 days post-capture to be a biologically relevant indication of capture-related stress.…”

Different Sex Allocations in Two Related Species: The Case of the Extant Hippopotamus

“…In addition, captivity may impact stress, which could be lower or higher depending on the species (Dickens & Bentley ; Narayan et al. ; Sparkman et al. ).…”

“…Animals are kept at high density, which makes the captive environment well suited for testing the local resource competition hypothesis. In addition, captivity may impact stress, which could be lower or higher depending on the species (Dickens & Bentley 2014;Narayan et al 2014;Sparkman et al 2014). On the other hand, it should be mentioned that studbook data have some drawbacks as, for example, absence of detailed group compositions within individual zoos or absence of data about diet or veterinary treatment.…”