Analysis of crocodile population and behavioural datasets

Analysis of crocodile population and behavioural datasets

There are several opportunities to answer some very interesting questions about crocodile population ecology, behaviour and physiology by applying a variety of statistical methods to existing datasets. Some of these may provide the opportunity for additional data collection in the field and/or through liaison with relevant agencies.

  1. Freshwater crocodile population survey data, Kakadu National Park. This will involve analysis of all the population survey data for freshwater crocodiles (Crocodylus johnstoni) conducted in Kakadu National Park. There is quite a bit of variability in the methodology and data quality, including time of day/night, survey method (most on foot, some by boat or aerial spotting), make-up of the survey team, location and distance, interval between surveys etc. Not only will this teach the student the importance of consistent methodology when collecting data, there are a number of useful questions about population trends and structure that can be teased from the data.

  2. Behavioural data, saltwater crocodiles feeding on marine turtles on nesting beaches. This will involve analysis of many hours of footage both day and night (using a highly sensitive "Starlight" camera system) of saltwater crocodiles (Crocodylus porosus) feeding on marine turtles (primarily flatback turles, Natator depressus) on nesting beaches in Far North Queensland. Crocodiles can be identified from unique scalation and pigmentation patterns on the tail, body and head. Feeding behaviour can be logged, including rate of prey capture, prey detection distance, social proximity to other crocodiles, feeding groups, social interactions, average prey size and intake per night (approximate) and more. It’s potentially very information rich, the majority of the work will involve logging data from the video. This includes unique behaviour never before documented.

  3. Saltwater crocodile (Crocodylus porosus) distribution patterns within a river system, and changes in those patterns over time during a period of population recovery. There are nearly 40 years of data from C. porosus population surveys in the NT, and while population recovery has been analysed in quite a bit of detail, this analysis has concentrated on density and size class changes. This project will look instead at distribution changes along a river course. Although individual crocodiles cannot be tracked, overall groupings can be identified, which may provide clues as to where key feeding, nesting and social areas on the river system are, and how those areas may have changed over time as population density and size class structure has changed. It may offer important clues on crocodile behavioural change during recovery for management purposes.

  4. Satellite telemetry data from saltwater crocodiles (Crocodylus porosus) tracked by GPS in Kakadu National Park. We have a database of short-term (typically 20-35 days) post-release data on saltwater crocodiles tracked by GPS. Data accuracy are very high, data interval is very short, but duration of tracking per crocodile is short (due to battery limitations). The premise of the release was to determine whether crocodile behaviour, including its preferred residence in the river, could be affected through capture and release. This is used as a management strategy by Kakadu National Park to dissuade crocodiles from becoming too interested in the activities of local fishermen. This is an ongoing project that will require additional crocodile capture and transmitter deployment in association with KNP rangers, as the existing dataset is from a pilot study into the feasibility of low-cost GPS transmitters. There is good potential to answer relevant questions about crocodile behaviour and its impact on human crocodile conflict resolution.

  5. Analysis of chemical restraint data used by NT and Federal Government for crocodile capture and relocation. This involves analysis of a relatively large database covering several thousand animals. Data include variables such as size of crocodile, induction time, dose relative to size (that was effective in a real-world situation), success or failure, efficacy of different drug combinations. The purpose of the analysis would be to examine whether the immobilizing agent is effective and safe across a wide range of crocodiles. This would have management implications and provide a reliable dosage table for these agents.

  6. Analysis of capture data for “problem” itinerant crocodiles removed from Darwin Harbour to determine what patterns and trends exist, whether certain useful traits can be identified from morphological, marking, genetic etc data. This is a very large database and there is a wide scope for analysis with strong implications for human crocodile conflict resolution.

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