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.

The aim of our research was to broaden our knowledge of one of the most phenomenal “living dinosaurs” we know

today.

You can volunteer too• The long term

objective of the research program is to gain a better understanding of the ecology and physiology of the crocodile so that a conservation strategy can be put in place.

• Volunteers in the study capture crocodiles of all size classes.

You can volunteer too• They assist with

measuring, weighing, sexing, stomach pumping and tagging of crocodiles.

• They also assist in the attachment of radio-telemetry devices that will be used to monitor movements and to determine home range sizes of the animals

radio- telemetry device

You can volunteer too•During the breeding season, volunteers participate in nesting surveys carried out by boat and on foot.

•They help collect eggs and monitor egg incubation for the temperature-dependent sex determination study.

You can volunteer too• They raise hatchlings in

order to determine growth rates.

By providing scientific expertise and detailed biological information we can effectively manage threats to crocodile populations

Economic and environmental 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 ecological value.

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

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

Argyle is the largest man made 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

• Predators such as varanid lizards, pigs and dingoes who remove and eat crocodile eggs from nests.

The Problem cont…AND 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).

My goodness they are everywhere and mum warned me not

to eat them!!!!Did I listen?

The research aims and objectives

Ruchira’s hopes his study will fill information gaps on crocodilesHe is looking at their:

1. Demography• Growth• Recruitment• Age• Structure

2. Biology• Diet• Movements• Habitat.

Ruchira’s study will look at:•the diversity of their habitats

•their feeding and nesting behaviour

•How they care for their young.

What we were interested in

What did I do to help?• I was part of a team that helped

Ruchira collect information on the population status, distribution and abundance of these animals in their aquatic system.

• We collected last year’s hatchlings and marked them so could monitor their growth, dispersal and observe their behaviours.

• We went on foot surveys, daytime boat surveys, night-time spotlight surveys.

• We helped capture, measure, weigh, stomach flush and tag crocodiles of various size classes.

What did I do to help cont..?• We set up baited remote

cameras to study abundance and diversity of the land predators on the shoreline.

• We looked for and found crocodile nesting sites and examined crocodiles at close quarters in search of ectoparasites and learnt about data capture and analysis.

What is an ectoparasite you ask?

• Insect ectoparasites are those insects that live on the outside of other animals (ecto = outside).

• Most of these insects survive off the blood of their hosts, although some also eat skin, hair and other secretions.

• To qualify as a true ectoparasite you must have an intimate relationship with your host. For example, mosquitoes are not ectoparasites; they do not live on humans, but only visit for a blood meal.

• Insect ectoparasites are often highly adapted to their specialised host environments.

• Typical adaptations include loss of functional wings, flattening of the body, strong legs and claws for clinging onto the host, and biting or sucking mouthparts for taking blood meals."

So can you think of some?

• Leeches?• Lice?• Mmh not nice but sometimes it works for

both species. For example the tiny blackbird plover acts as a toothpick for the fierce crocodile and helps by removing tiny morsels of food that is stuck between the crocodile's teeth. Surely there must be a less risky way to get food than this?

• Read more here http://australianmuseum.net.au/Insects

Why we doing this research?•Understanding these key elements will help predict how cane toads, predators and fishing will affect Lake Argyle crocodile populations.

•This information will help to develop effective management and conservation techniques for freshwater crocs.

RISKY WORK!!! • We found out CROCS BITE!!!

• We suffered from dehydration and heatstroke and insect bites.

• We got caught in storms on the river.

How did we minimise the risk?

• We were supplied with safety gear on the boat (satellite phone, EPIRB, flares, life jackets)

• The Volunteer Workers Policy of Uni of Sydney provides liability cover and personal accident.

OMG does my insurance cover

this ?

What did we find out? • Crocs have no resistance

to bufotoxins in cane toads.

• FYI. Bufotoxins are a family of toxic substances found in the parotoid glands, skin and venom of many toads(genus Bufo); other amphibians; and some plants and mushrooms.

http://en.wikipedia.org/wiki/Bufotoxin

What did we find out?

• There was a 77% reduction in the crocs population after cane toads invaded the Victoria River in Northern Territory

• It will take differing management techniques to remedy mortality as a result of serious injury of croc captures in nets and resolve problematic food chain pathways as a result of croc-fishery interactions.

Future direction• The intensity of toad impact relates to cane toad densities,

availability of alternative prey, the prey-preference of crocodiles, genetic resistance and the innate ability to learn in crocodiles.

• These factors are being investigated through field and laboratory studies and may give insight to the level of impact and how soon populations may recover after the invasion.

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