ScienceDaily (June 8, 2010) — The mystery of how the world's largest living reptile -- the estuarine crocodile -- has come to occupy so many South Pacific islands separated by huge stretches of ocean despite being a poor swimmer has at last been solved by a group of Australian ecologists.
A 4.8-meter male estuarine crocodile ready for release with satellite transmitter. This crocodile traveled over 590 km by sea. (Credit: Australia Zoo)
The estuarine crocodile (Crocodylus porosus) is a semi-aquatic reptile, living mainly in rivers, mangroves and estuaries. Its geographical range extends over 10,000 km2 of the South-East Pacific, from East India to Fiji and from southern China to North Australia. Although it spends most of its life in salt-water, it cannot be considered a marine reptile in the same way as a turtle is, for example, because it relies on land for food and water.
Many anecdotal accounts exist of large crocodiles being sighted far out to sea, but this is the first study to show -- using underwater acoustic tags and satellite tracking -- that estuarine crocodiles ride surface currents during long-distance travel, which would enable them to voyage from one oceanic island and another.
The results explain why, despite occupying such a large range, species diversification of the estuarine crocodile has not occurred.
Working in the remote Kennedy River in North Queensland, Australia, Dr Hamish Campbell from University of Queensland and colleagues from Queensland Parks and Wildlife Service and Australia Zoo tagged 27 adult estuarine crocodiles with sonar transmitters and used underwater receivers to track their every move over 12 months.
...
Read more here/Leia mais aqui: Science Daily
+++++
Published Online: 7 Jun 2010
Journal compilation © 2010 British Ecological Society
Hamish A. Campbell 1,*, Matthew E. Watts 1 , Scott Sullivan 2 , Mark A. Read 2 , Severine Choukroun 3 , Steve R. Irwin 4 and Craig E. Franklin 1
1 School of Biological Sciences, The University of Queensland, Brisbane, Qld 4072, Australia ; 2 Queensland Parks and Wildlife Service, Marlow Street, Townsville, Qld 4810, Australia ; 3 James Cook University, Townsville, QLD. 4811, Australia; and 4 Australia Zoo, Steve Irwin Way, Beerwah, QLD 4519, Australia (deceased)
*Correspondence author. E-mail: dr.hamish.campbell@gmail.com, c.franklin@uq.edu.au
KEYWORDS
behaviour • Crocodylus porosus • migration • telemetry • zoogeography
ABSTRACT
1. The estuarine crocodile (Crocodylus porosus) is the world's largest living reptile. It predominately inhabits freshwater and estuarine habitats, but widespread geographic distribution throughout oceanic islands of the South-east Pacific suggests that individuals undertake sizeable ocean voyages.
2. Here we show that adult C. porosus adopt behavioural strategies to utilise surface water currents during long-distance travel, enabling them to move quickly and efficiently over considerable distances.
3. We used acoustic telemetry to monitor crocodile movement throughout 63 km of river, and found that when individuals engaged in a long-distance, constant direction journey (>10 km day−1), they would only travel when current flow direction was favourable. Depth and temperature measurements from implanted transmitters showed that they remained at the water surface during travel but would dive to the river substratum or climb out on the river bank if current flow direction became unfavourable.
4. Satellite positional fixes from tagged crocodiles engaged in ocean travel were overlaid with residual surface current (RSC) estimates. The data showed a strong correlation existed between the bearing of the RSC and that of the travelling crocodile (r2 = 0·92, P < 0·0001).
5. The study demonstrates that C. porosus dramatically increase their travel potential by riding surface currents, providing an effective dispersal strategy for this species.
Received 2 February 2010; accepted 20 April 2010 Handling Editor : Tim Coulson
DIGITAL OBJECT IDENTIFIER (DOI)10.1111/j.1365-2656.2010.01709.x
+++++
Professores, pesquisadores e alunos de universidades públicas e privadas com acesso ao site CAPES/Periódicos podem ler gratuitamente este artigo do Journal of Animal Ecology e de mais 22.440 publicações científicas.
+++++
