My research addresses questions on behavioural and evolutionary ecology. I am particularly interested in the interface between ecology and animal behaviour as well as movement ecology and parasitology. Generally speaking, much of my research focus is on social behaviour and drivers of sociality. My research is underpinned by social network theory and I regularly include social network analyses in my research as a consequence.
My research is question driven. I have mainly worked with lizards and frogs, but recently expanded to mammals. I am investigating disease transmission in bottlenose dolphins with the Bansal Lab and have been awarded a DECRA fellowship by the Australian Research Council to investigate the behaviour and ecology of sheep in the rangelands, including social networks and collective behaviour.
The social structure of a population is a fundamental component of its organisation that drives ecological and evolutionary processes ranging from parasite transmission to sexual selection. I am currently working on these general themes (1) population social structure/social networks, their drivers and their influence on parasite and pathogen transmission, (2) social organisations, and (3) mating systems.
Population social structure/social networks
I am using social networks to investigate what drives social structure in populations, as well as how parasites and pathogens move through populations. For example, I investigated how habitat complexity influences social network structure and movement (Leu et al. in press). I also looked at whether resource use and resource sharing drives the social structure in the Australian sleepy lizard, Tiliqua rugosa (Leu et al. 2011a). I found that synchronous refuge sharing did not lead to increased frequencies of social associations while lizards were active, and we did not find any evidence that refuge sharing was a precursor to sleepy lizard social behaviour. But read more about this species’ fascinating social behaviour and long-term monogamy – below, or (Leu et al. 2015).
Investigating parasite transmission, I found that asynchronous refuge sharing behaviour and the transmission network modelled on this behaviour, predicts the tick load in the sleepy lizard. Ticks are non-infectious in-between two hosts while molting into the next life stage, and are transmitted when different host individuals are using the same refuges at different times.
This study was particularly interesting because it showed the value of alternative networks, based on asynchronous sharing of refuges, in understanding how indirectly transmitted parasites move through a host population (Leu et al. 2010b). We then followed this study with a multiple year, multiple tick project (Wohlfiel et al, 2013).
The social organisation of animal groups describes the size and composition (with respect to sex, age and kinship) of a social unit as well as the distribution of its members in space and over time. This is clearly based on the frequency and distribution of social interactions among individuals, linking it to my social network research theme. I have been working on social attraction in larval green and golden bell frogs, Litoria aurea, and found that they are directly attracted to conspecifics in the absence of environmental cues. This response was body size dependent and I suggested that small tadpoles are more vulnerable to predation and therefore more likely to form aggregations as an anti-predator behaviour (Leu et al. 2013).
I also investigated pair-living behaviour in sleepy lizards, Tiliqua rugosa. Pair-living often evolves when biparental care is selected for because males can increase their reproductive success by staying with one female and caring for one set of offspring instead of associating with different females. Hence, pair-living without any overt biparental care, such as in the sleepy lizard, is an intriguing socio-ecological phenomenon. In a previous study I investigated whether the pair-living social organisation is male or female driven. I described male and female activity and movement patterns, and investigated whether males or females separate and re-unite with their pair partner more frequently than the opposite sex (Leu et al. 2011b).
I am also interested in mating systems. Monogamy when biparental care for the offspring is absent, is a particularly rare and an intriguing mating system. The sleepy lizard is long-term monogamous, and I investigated the effect of mate familiarity on the timing of mating (Leu et al. 2015).