I'm Dr Tasmin Rymer, an animal behaviourist at James Cook University, and I'm looking to identify those characteristics that make some individuals more resilient to environmental change than others.

Background and Purpose

Although environmental change is a natural phenomenon, the current rate of human-induced environmental change is unprecedented in Earth's history, both in terms of the speed of change, as well as the unpredictability of change. When environments experience human-induced change, such as deforestation, this often exposes the native species living there to additional stressors such as new diseases, predators and competitors in the form of invasive species.

Because people have had, and are having, significant negative effects on native animals, my mission is to identify what characteristics of individuals will help them cope with changes in their environment. It is important to focus on the individual, rather than the ecosystem, because animals, like people, are all different, and some will naturally cope better with change than others.

For this project, I will test an evaluative flow chart that I have designed to predict resilience, and I will use a native Australian rodent, the fawn-footed mosaic-tailed rat Melomys cervinipes, as a model. Fawn-footed mosaic-tailed rats are endemic to Australia and occur along the eastern seaboard from northern New South Wales to northern Queensland. Importantly, they occupy forests, which are complex environments. They are an important part of the food chain, being primary prey for numerous predators (e.g. dingoes, snakes and owls) and they are also important seed dispersers of forest plants. Like many Australian rodents, we know very little about their behaviour in general.

Process

The first step of the process is to assess each individual's behaviour, specifically behaviours related to an individual's personality. Personality in animals is defined as consistent individual differences in behaviours shown across contexts (e.g. mating, foraging) and over time. Personality is measured along different behavioural axes, including bold/shy, aggressive/docile and proactive/reactive. Bold animals are more willing to explore, and take more risks, than shy ones. Aggressive animals can dominate resources and are more competitive than docile ones. Finally, reactive animals are more flexible, able to adjust behaviours rapidly, than proactive ones. To assess personality, I will use standard laboratory tests (open field, novel object, light-dark box), measuring behaviours such as neophobia (how long it takes to approach something new), exploration and activity. Each individual has to experience each test twice, at least one month apart to assess the repeatability of behaviour (i.e. the individual shows the same behaviour over time), which is indicative of personality.

The second step of the process is to assess an individual's cognition, specifically, its ability to solve problems and learn. Some individuals may be able to innovate (solve a problem they have never experienced before). Some individuals may have to experience the same problem multiple times before they can solve the problem. Some individuals will learn to solve problems faster than others. To assess innovation, problem-solving and learning, I will use standard laboratory tests (associative learning task, obstruction task, puzzle boxes), measuring whether or not individuals can solve the problem, how long it takes them and what behaviours they use.

Behaviour and cognition are influenced by an animal’s internal physiology, specifically its hormones, and there is also growing recognition that microbial diversity in the gut also has the capacity to impact behaviour and cognition. When animals are stressed, they release hormones called glucocorticoids, such as corticosterone, that mobilise sugar (glucose) to provide the energy they need to either fight or flee from the stress. Reactive individuals show high-stress reactivity, meaning they have higher concentrations of stress hormones, whereas proactive individuals show low-stress reactivity. Individuals with lower gut bacterial diversity are considered to be less healthy than individuals with higher gut bacterial diversity. In addition, individuals with lower gut bacteria are often more anxious and stressed, and are less bold. To assess hormone concentrations, I will collect faeces, and use enzyme-linked immunosorbent assay (ELISA), which is a standard procedure. To assess gut microbial diversity, I will again collect faeces, and then bacterial DNA is extracted and analysed using 16s amplicon sequencing.

Significance

To my knowledge, all these interactions have not been studied at an individual level in any species to date. This native rat is also significant because one of its sister species, the Bramble Cay mosaic-tailed rat, was declared extinct this year – the first mammal extinction caused by human-induced climate change. Using this flow chart, I’ll be able to predict the relative resilience of each individual. By testing the efficacy of this flow chart in the lab, I hope that scientists will then take it into the field and use it to assess the relative resilience of individuals of their study species. This will better enable targeted conservation goals in areas where resilience is predicted to be low, and provide information on management options for particular species that may be less resilient in general than others

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JCU Research Portfolio: Dr Tasmin Rymer JCU Research Portfolio

Budget Justification

The behavioural and cognitive components of the data collection are already complete.

Total Requested $4975.00

I will use the enzyme-linked immunosorbent assay (ELISA) to assess corticosterone concentrations. These are commercial kits that provide all the necessary chemicals to run the assay. Each kit is sufficient to run 36 samples comfortably in duplicate. As my sample size is 40 individuals, I require a second kit. This will also allow me to run some of the same individuals on both kits, allowing me to assess both inter-assay and intra-assay reliability, increasing the accuracy of the results, and making them more robust.

It will cost $19.38 per individual to run these assays. Total: $19.38 x 40 = $775.00

Assessing the gut microbial diversity requires DNA extraction and 16s amplicon sequencing. Samples are sent away to the Australian Centre for Ecogenomics for processing. The samples are assessed multiple times, ensuring their accuracy and robustness.

It will cost $25.00 per individual for bacterial DNA to be extracted from faecal samples. Thereafter, it will cost $80.00 per individual for bacterial communities to be profiled at all taxonomic levels (from Domain to Genus). Total: ($25.00 + $80.00) x 40 = $4200.00