Australasian Regional Association of Zoological Parks and Aquaria

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ARAZPA Organisation: Crocodylus Park.

Experience Title: Impact of Cane Toads on Freshwater Crocodiles and other wildlife in the McKinlay River, Northern Territory.

Experience Synopsis: The endemic Australian Freshwater Crocodile (Crocodylus johnstoni) is widely distributed across Northern Australia, inhabiting freshwater rivers, creeks and pools, mainly upstream of tidal influence. Research by Professor Grahame Webb and his team in the late 1970s and early 1980s took the "freshie" from one of the least known crocodilians to one of the best-known. The cornerstone of this program was the capture and marking of a large proportion of the McKinlay River population of Freshwater Crocodiles (about 2000 individuals).

With the spread of the Cane Toad (Bufo marinus) into the Northern Territory, this population is now threatened. Toads are poisonous, and if eaten can cause death. Freshwater Crocodiles in other rivers colonised by toads are known to have been affected.

By catching crocodiles before and after Cane Toad colonisation, the project aims to quantify natural survival rates, and to measure the impact of Cane Toads. Quantifying survival rates will greatly improve our understanding of the population dynamics of Freshwater Crocodiles.

Catching begins in late August, after the nesting season is finished. Crocodiles are caught using fine mesh fishing nets, which are strung across the billabongs in which the animals congregate during the dry season. All crocodiles caught are sexed, measured, and if unmarked, are scute-clipped for future identification.

The impact of Cane Toads on other wildlife, specifically varanid lizards and fish, is also being measured.

To date over 1,200 Freshwater Crocodiles have been captured in 2001 and 2002. Analysis of the data has now begun. Further catches to assess the impact of Cane Toads are planned for 2003 and beyond.

Audience: Participation is on a formal (ie. through an educational organisation) and informal (ie. individual) basis.

Duration: August to October (2001 - 2003 and possibly later).

Cost per Participant: Free, and food is provided during fieldwork. Participants are expected to support themselves at all other times.

Set-up Costs: Establishment of the original database is the result of a decade of work by a number of researchers and it is difficult to place a value on it. The current project's costs are based on staff time, vehicles, equipment and the difficult to assess value of staff expertise.

How the Experience is Marketed: Internet and word of mouth.

Staffing: One full-time staff member, with additional staff support when required.

Links & Partners: Northern Territory University, Green Corps, Australian Army.


Evaluation: The project is still underway. The first two years of field work have been very successful with almost 1,300 crocodiles captured. A significant number were recaptures of crocodiles originally marked between 1978 and 1989.

Contact Person: Chief Scientist, Charlie Manolis

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