Behavioural and physiological traits of the endangered marsupial, the northern quoll (Dasyurus hallucatus)

Abstract

Selection favours organisms that survive to produce offspring. To achieve this, animals have evolved a variety of life history strategies, with variation in lifespan, number of reproductive events and number of offspring among species. In recent years, the pace-of-life syndrome (POLS) theory has been used to integrate physiology and behaviour with life history to help explain the differences in reproductive strategies among species. For example, species with a ‘fast’ pace-of-life are generally small in size, reproduce early, and have a short lifespan, and predicted to have associated high metabolism and performance. To fuel such a ‘fast’ pace-of-life, individuals may also make corresponding foraging decisions that balance increased needs for energy against predation risk. Animals can modify their predation risks when foraging using changes in vigilance and activity. Thus, physiological traits and foraging decisions are predicted to covary to influence an individual’s survival and reproductive success. In species where the sexes have different reproductive strategies, POLS predicts corresponding differences in physiological and behavioural traits.Using the endangered northern quoll (Dasyurus hallucatus), we explored if there were differences in foraging behaviour and physiology. Males of this species are approximately double the mass of females at maturity, and have a 100% mortality rate shortly after their single breeding season while females can breed for multiple years (facultatively semelparous). As such, the sexes differ greatly in their energetic demands due to both their sexual dimorphism and life history strategies.Groote Eylandt, an Indigenous Protected Area, in the Northern Territory has the highest naturally occurring northern quoll population in Australia and was the location for this study. Across 2.5 years, I collected data on 381 northern quolls, predominantly using mark-recapture, remote video, and experimental manipulations to assess relationships between sex, mass, metabolism, locomotor performance and foraging behaviour.In Chapter 2, I investigated if the foraging behaviour of the northern quoll was affected by sex or developmental period. Using trays filled with sand and a finite number of food bait items, I conducted a giving-up density (GUD) foraging experiment over an 8-month period in 2017, measuring total time spent on the tray, proportion of time vigilant and number of baits eaten for individual quolls. I found that male northern quolls had lower proportions of vigilance than females, but the sexes did not differ in how long they foraged on the trays nor bait pieces consumed. Quolls foraged for longest in the period leading up to the breeding season. As males showed riskierforaging decisions and females displaying less risk-prone foraging behaviour, my results suggest the life history traits of northern quolls are associated with their foraging behaviour.Personality traits like boldness can also affect foraging behaviour. For a short-lived species, an individual’s foraging personality may ultimately affect their reproductive success. For semelparous individuals who have one reproductive bout, it may be beneficial to be bolder and gain more food to fuel energetic demands. However, individuals that have multiple attempts at breeding may be shyer, trading a higher fecundity for less risky foraging decisions. In Chapter 3, I assessed whether northern quolls varied in their foraging behaviour, and if behaviours were repeatable within individuals across time. I found that individual quolls had short and long-term repeatability of GUD (our proxy for foraging boldness). This suggests that some quolls are bolder than others in regard to their foraging behaviour.In Chapter 4, I investigated if resting metabolic rate (RMR) and sprint speed differed between the sexes. Sprint speed and RMR were not associated, and there were no differences between the sexes in either of these traits. However, sprint speed and RMR were significantly higher in 2018 than 2017. While this study only spanned two years, there is some evidence that the amount of rainfall, and by extension invertebrate food abundance, may affect the survival of individuals with differing RMR rates.Previous research on northern quolls report this species as asocial and solitary on mainland Australia. Chapter 5 describes the first records of affiliative interactions between female northern quolls. The extensive home-range overlap and high population densities of northern quolls on Groote Eylandt may be driving these affiliative encounters between both kin and unrelated females. The reported asocial and solitary nature of northern quolls may be a consequence of the low population densities found on the mainland.In summary, I found that male northern quolls took more risks while foraging. An individual’s GUD was the most repeatable foraging behaviour. Our findings did not support the POLS theory that RMR and sprint speed are associated, nor that sex would affect either of these traits. Finally, we report the novel finding of sociality among female northern quolls, behaviour that may be absent from mainland populations because of low population densities.