FRESHWATER CROCODILES AT LAKE ARGYLE

SAVING OUR NOT SO FURRY FRIENDS

Toto, I don’t think we’re in Kansas anymore…

• Hi there, my name is Antonia Quinlivan.

• I’m a 3rd year Animal & Veterinary Science student at the University of Sydney.

• This is my story of how I found myself in the middle of nowhere wrestling crocs on a study with PhD student Ruchira Somaweera.

• An experience that left me with more than an award winning thong tan on arrival back home to a little town called Sydney.

Where is Lake Argyle?• With an area of 880km2 at normal water level, Lake

Argyle is the largest manmade lake in Australia.• It contains the highest density of Freshwater

Crocodiles (Crocodylus johnstoni) in Australia. • In 1989, a boat spotlight survey estimated croc

populations of 25,000 (G Webb Pty Ltd, 1989).

•http://www.lakeargyle.com.au/images/lake-argyle-aus-map02.gif

Magnificent part of Aus-BREATHTAKING!

The ProblemCurrent threats to

our crocs in Lake Argyle include:

• entanglement in fishing nets

• Nest predation by varanid lizards, pigs and dingoes.

The Problem cont…CANE TOADS!!!

It is predicted they will soon colonise the shoreline of the lake.

• AND CANE TOADS KILL CROCS THAT INGEST THEM!!! (Letnic et al. 2008).

• Currently, there is a lack of basic knowledge on crocs needed for effective management.

The research aims and objectives

Ruchira’s doctoral study aims to fill croc information gaps on:

1. Demography• Growth• Recruitment• Age• Structure

2. Biology• Diet• Movements• Habitat.

•Understanding these key elements will help predict how cane toads and fishing will affect Lake Argyle croc populations.•This info will help develop

effective management and conservation techniques for freshwater crocs. Ruchira’s study will look at:

• the spatial heterogeneity of crocs

• their feeding and nesting behaviour

• parental care.

The research aims and objectives cont..

Field work and what I did to help

• Collected last year’s hatchlings and marked them so their growth, dispersal and observed behaviours can be studied.

• Spotlighting, used as index of relative abundance in monitoring crocs. Done by flashlight at night on boats.

• Catching and stomach flushing.• Analysing stomach contents.• Sweep netting floating mats to

study prey availability.• Set up baited remote cameras

to study abundance and diversity of land predatorson the shoreline.

RISKY WORK!!! • CROCS BITING!!!• Dehydration and heatstroke, insect bites.• Caught in storms on the river.• We were supplied with safety gear on boat (satellite phone,

EPIRB, flares, life jackets)• The Volunteer Workers Policy of Uni of Syd provides liability

cover and personal accident.

Results of study so far• Crocs have no physiological

resistance to bufotoxins in cane toads.

• Substantial mortality of populations occurred after invasion in the Victoria River in NT (77% population decline of crocs!!), which changes the population structure.

• Differing management techniques will remedy damage/mortality as a resulutof serious injury of croc captures in nets and resolve problematic trophic pathways as a result of croc-fishery interactions.

Economic benefits of this study

• Crocs are an iconic tropical animal in Australia.

• Lake Argyle has the highest population of freshwater crocs and plays a big role in the tourism industry- direct benefit.

• Freshwater crocs are the top predators in the ecosystem, therefore the study holds great ecology value.

• Conservation of this species in this habitat has benefits for conservation, tourism and animal health.

Future direction• Publication of findings in journals and results discussed in

international conferences.• Studies into genetic resistance of cane toads through

lab/field work.

Potential of Conditioned Taste Aversion Learning!

• Previous studies on northern quolls (Webb et al. 2008) were successful in training quolls to avoid cane toads before they invade.

• The method involves deploying baits containing a non-detectable nausea-inducing chemical ahead of invasion.

• Predators consume bait, become ill, subsequently avoid consuming live toads on arrival.

• A future project will examine whether crocs will consume non-

toxic chicken baits.

Spotted Quoll

How this study was made possible

• Ruchira is based in the “Shine Lab” at the University of Sydney.

• The Shine Lab is named after Professor Rick Shine who conducts research on the interface between evolution and ecology, particularly in reptiles (snakes and lizards).

• In recent years he has shifted his focus to major issues in conservation -especially the biology, impact and control of invasive species such as the cane toad.

Who funds the study? The project is funded under 3 grants:

1. Australian Research Council grant to Rick Shine.

2. Crocodile Specialist Group Research Grant.

3. University of Sydney Post Graduate Research Grant.

Some funding support was provided through a grant obtained by Jonathan Webb from a Caring for our Country Grant Government groups like Dept of Environment and Conservation (DEC) and Dept of Fisheries also work with Ruchira to find appropriate fishing grounds for locals and tourists.

Challenges of the study• Working in such a remote area creates

some logistic problems such as:– Safety issues of working alone.– Getting assistance from community

groups and research organisations to support the study

– The need for ongoing support from volunteers to allow Ruchira to complete his study on time.

Conclusion• We now know that our

freshwater crocodiles face a potentially life threatening future from the predicted cane toad invasion of Lake Argyle.

• It is studies like Ruchira’s that find solutions to conserve Australia’s wildlife.

• Without volunteers, these studies would not be possible!

Personal Reflection• My time at Lake Argyle in the

summer of 2009 was the single most life changing and eye opening experience I have had up to date.

• I was fortunate enough to see a part of our beautiful country that I wouldn’t have experienced without being exposed to such studies through Uni.

• I made invaluable connections and lifelong friends.

• Everyday was a challenge-and it got better each day. I’d be back in the 40+ degree heat jumping on crocs in a heartbeat!

What you can doSIGN UP AND VOLUNTEER FOR THE STUDY!!

• Drop Ruchira an email: ruchira.somaweera@gmail.com• or check out his website at

www.bio.usyd.edu.au/sites/Shinelab/students/ruchira/ruchira.html

What you can do• Get on board with a toad collection campaign and help out with the

annual muster.Join:

– Stop the Toad Foundation.– Kimberley Toad Busters.

References• G. Webb Pty Ltd 1989. The results of

crocodile surveys in Lake Kununurra and Lake Argyle (Western Australia), February-March 1989. Report to CALM, 1989.

• Letnic, M., J.K. Webb, & R. Shine. 2008. Invasive cane toads (Bufo marinus) cause mass mortality of freshwater crocodiles (Crocodylus johnstoni) in tropical Australia. Biological Conservation 141:1773-1782.

• Webb, J.K., G.P. Brown, T. Child, M.J. Greenles, B.L. Phillips, & R.Shine. 2008. A native dasyurid predator (common planigale, Planigale maculata) rapidly learns to avoid toxic cane toads. Austral Ecology 33:821-829.

THANKS!!!

GOLD SILVERPLATINUM

BRONZE

WOULD LIKE TO THANK THE SPONSORS OF THE 2010 CREAM OF THE CROP COMPETITION