Physiological stress levels in wild koala sub-populations facing anthropogenic induced environmental trauma and disease

Abstract

Australian small mammals such as koalas must cope with immense pressure from anthropogenic induced stressors or trauma such as bushfires, vehicle collision impacts and habitat disturbance and land clearance. In addition, they must cope with diseases such as chlamydia. To date, there is no published literature on physiological stress levels in wild koala populations compared with identified environmental stressors. This study investigated physiological stress levels within sub-populations of wild koalas encountering environmental trauma and disease from New South Wales (NSW), Queensland (QLD) and South Australia (SA). Physiological stress was determined using a faecal glucocorticoid (or cortisol) metabolites (FGMs) enzyme-immunoassay (EIA) from 291 fresh faecal samples collected from wild koalas at the point of rescue. A healthy breeding sub-population from a forest reserve in QLD acted as a control group. Clearance of prime Eucalyptus habitat had the largest impact on FGMs, followed by bushfire related factors (e.g. flat demeanour, dehydration and burns injury). Koalas with other sources of physical injury (dog-attacks and vehicle collisions) and disease (chlamydia) also had higher FGMs compared to healthy wild koalas. Healthy wild koalas expressed the lowest median levels of FGMs. Overall, the results highlight that anthropogenic-induced stressors tend to increase physiological stress in wild koalas. Thus, the ultimate stressors such as habitat clearance and bush fire events could increase the incidences of proximate stressors such as dog attacks and vehicle collisions, and increase risks of foliage shortage, diseases and mortality. Therefore, there is need for ecological monitoring, conservation management actions and policy changes to curb the koala population crisis, especially within on-going and future land and road development programs.

Seasonal Variations of Faecal Cortisol Metabolites in Koalas in South East Queensland

“…The concept of baseline, when referring to glucocorticoid values, has been given different meaning depending on the type of research and the intent of the researchers [41,56,57], and in many cases refers to a point-in-time value [39][40][41] using a limited number of animals. Admittedly, the main intent of most of these studies was to physiologically validate EIAs before and after an ACTH challenge; however, some authors compare obtained FCM values to those of 'stressed' animals [41,58,59] without taking into consideration the physiological changes due to period of day, sex and season. Other year-long studies on marsupials were carried out on numbats and wombats also in captivity [38,60].…”

The impact and implications of vehicle collisions on the endangered and endemic Zanzibar red colobus (Piliocolobus kirkii)

“…Unlike natural predators, which are more successful in killing animals in poorer condition, vehicles remove individuals from a population without regard to their condition or health (Bujoczek et al, 2011). Even non-lethal collisions can have a negative impact on animals via increases in glucocorticoid production (Narayan, 2019). Taken together, the direct and indirect effects of colobus-vehicle collisions could lead to suboptimal population health that would 275 contribute to reduced persistence of roadside groups.…”

Animal Harms and Food Production: Informing Ethical Choices

“…Contemporary examples of indirect harms that culminate in wild bird mortalities include the impact of wind turbines (“wind farms”), communication towers and solar arrays [ 22 ]. Beyond harms that cause mortalities, there have also been vast improvements in understanding how wild animals are affected by non-lethal interactions with anthropogenic stressors like artificial light and sound (e.g., non-lethal stress in peri-urban wildlife [ 23 ]). These non-lethal effects also constitute harms.…”