Christopher P Johnstone

Monash University (Australia) · School of Biological Sciences, Clayton

Stress responses, which are mediated by the neurogenic system (NS) and hypothalamic-pituitary-adrenal (HPA) axis help vertebrates maintain physiological homeostasis. Fight-or-flight responses are activated by the NS, which releases norepinephrine/noradrenaline and epinephrine/adrenaline in response to immediate stressors, whilst the HPA axis releas...

Although many pharmaceutical compounds (and their metabolites) can induce harmful impacts at the molecular, physiological and behavioural levels, their underlying mechanistic associations have remained largely unexplored. Here, we utilized RNA-Seq to build a whole brain transcriptome profile to examine the impact of a common endocrine disrupting ph...

The capacity of pharmaceutical pollution to alter behaviour in wildlife is of increasing environmental concern. A major pathway of these pollutants into the environment is the treatment of livestock with hormonal growth promotants (HGPs), which are highly potent veterinary pharmaceuticals that enter aquatic ecosystems via effluent runoff. Hormonal...

Unprecedented increases in air temperature and erratic precipitation patterns are predicted throughout the twenty-first century as a result of climate change. A recent global analysis of leatherback turtle hatchling output predicts that the nesting site at Sandy Point National Wildlife Refuge (SPNWR) will experience the most significant regional cl...

We review evidence for and against the use of erythrocyte indicators of health status and condition, parasite infection level and physiological stress in free-living vertebrates. The use of indicators that are measured directly from the blood, such as haemoglobin concentration, haematocrit and erythrocyte sedimentation rate, and parameters that are...

Chemical pollution is a pervasive and insidious agent of environmental change. One class of chemical pollutant threatening ecosystems globally are the endocrine disrupting chemicals (EDCs). The capacity of EDCs to disrupt development and reproduction is well established, but their effects on behaviour have received far less attention. Here, we inve...

Abstract Life-history theory predicts that a trade-off in the allocation of resources between different physiological systems exists because resources are finite. As a result, females investing heavily in reproduction may compromise their future health. We used hematology, serum biochemistry, mass, and morphometric measurements as indicators of phy...

Successful urban colonisation by birds requires tolerance of many disturbances and avoidance of chronic stress and major disruption to critical activities. Habituation may be involved in acquiring tolerance of human proximity, in which case tolerance should vary with the degree of opportunity to learn that most humans do not present a threat and sh...

Body condition influences activities and processes affecting fitness. Erythrocyte variables, particularly haemoglobin concentration and haematocrit, are increasingly being used as avian condition indicators. However, some potentially confounding factors should be considered when adopting this approach and there are some conflicting findings concern...

Parent birds often have substantial fat reserves that are critical in successful breeding. Erythrocyte variables, particularly haematocrit and haemoglobin concentration in peripheral blood, are increasingly being used as avian body-condition indices (BCIs) but problems can arise if such variables are used and interpreted uncritically. We investigat...

When vertebrate physiological ecologists use the terms 'stress' or 'physiological stress', they typically mean the level of hypothalamus-pituitary-adrenal (HPA-) axis activation. Measurements of stress hormone concentrations (e.g. glucocorticoids in blood, urine or faeces), leukocytes (e.g. the neutrophil-lymphocyte ratio or heterophil equivalent),...

Habitat fragmentation and degradation seriously threaten native animal communities. We studied the response of a small marsupial, the agile antechinus Antechinus agilis, to several environmental variables in anthropogenically fragmented Eucalyptus forest in south-east Australia. Agile antechinus were captured more in microhabitats dominated by wood...

Although the vertebrate stress response is essential for survival, frequent or prolonged stress responses can result in chronic physiological stress, which is associated with a suite of conditions that can impair survivorship and reproductive output. Anthropogenic habitat fragmentation and degradation are potential stressors of free-living vertebra...

Habitat fragmentation is a major cause of population reduction and loss, and increasing evidence suggests that effects of fragmentation on populations vary as a function of the life history and autecology of species. We investigated the effect of anthropogenic habitat fragmentation on several indicators of population health in the agile antechinus...

Cities are potentially stressful environments for birds for numerous reasons, including their high volumes of pedestrian and vehicular traffic. Native birds inhabiting cities tolerate such human disturbance, but may still potentially incur some cost that is reflected in body condition and the level of chronic stress experienced, unless they are inh...