Assessing the impacts of habitat fragmentation and subsequent anthropogenic expansion on the behavioural, nesting and population ecology of the estuarine crocodile, Crocodylus porosus

The project sought to examine the effects of habitat loss and fragmentation on the ecology and population genetics of the estuarine crocodile (Crocodylus porosus). Additionally, the role played by humans in this anthropogenically-altered landscape was examined. Through the utilisation of a host of technologies, some previously established, some completely novel in crocodilian research, a new insight into how the landscape is utilised by these cryptic predators was developed. This project represents a first detailed look at Sabah’s crocodilian population, as well as being the first active crocodile research carried out in Sabah’s longest river. Male crocodiles were found to adhere to one of two behavioural strategies, territorial and nomadic, mirroring findings of Campbell et al. (2013). Territory sizes were, however, found to be smaller than those described in Australia, this was attributed to increased prey availability and ecosystem productivity. Only two females were tagged and appeared to also display differences in behavioural strategy. However, due to the small sample size, further work is required to confirm this. Both males and females were found to avoid barriers and were unwilling to pass beyond the barrier, despite no physical obstruction. Nests were detectable aerially through the use of drones and medium-large scale surveys shown to be feasible. Nests were found to all display a number of similarities in terms of habitat characteristics, allowing for refined modelling of survey locations. This allows for a larger survey area to be completed given a limited number of flights, highlighting its cost effectiveness versus traditional methods of nest surveying. Genetic analysis suggested that there was no evidence of a genetic bottleneck following the population recovery that has occurred over the last 30 years. Geographically indistinct haplogroups were discovered, as well as limited levels of inbreeding. The project also indicated that the population studied had undergone a population expansion that seems to have coincided with the onset of the last ice age and is likely attributable to changes in climate