Two species of crocodilians - the mugger of India and the American alligator - have been discovered using twigs and sticks as lures to draw the attention of birds looking for nesting material. Equally impressive: the crocodiles time the behavior to coincide with the seasonal cycles of the birds they prey upon. And to top it all off, it is the very first time that tool-use has been observed in any species of reptile.
Vladimir Dinets, a research assistant professor in the Department of Psychology at the University of Tennessee, Knoxville, made the observations beginning in 2007. His research, which had collaboration with J.C. and J.D. Brueggen of the St. Augustine Alligator Farm Zoological Park in S. Augustine, Florida, is being published in the current issue of the journal Ethology, Ecology and Evolution. Dinet elaborates upon his findings and writes more about crocodile behavior in his book Dragon Songs.
The behavior was first found in India, where Dinets observed crocodiles on the shallow edges of a pond lying in apparent rest. However, the crocodiles had small twigs perched across their snouts. The crocodiles remained perfectly still for hours as birds approached the pond, likely believing that the twigs and sticks floated on the surface. If a bird came within reach, a crocodile would spring in action and lunge for the avian prey.
Upon returning to the United States, Dinets and his associates conducted observations at four locations in Louisiana: two rookeries (bird-breeding grounds) and two that were not rookeries. All four sites produced observations of alligators using twigs to lure birds. However the alligators also knew when to make the most efficient use of the tactic. At the rookery sites, the alligators employed the sticks throughout the nest-building season. At the non-breeding locations which would see the most nest-building activity, the alligators timed the twig-luring behavior to take advantage of the birds looking for nesting fodder.
It is a discovery that could potentially alter the prevailing wisdom about alligators and crocodiles. Tool use among crocodilians indicates a more complex psychology than previously believed, and may even be a trait waiting to be observed across more of the reptile family. "This basically changes the way we have been looking at crocodiles across the years," Dinets said. "They are stereotypically seen as sluggish, stupid and dull but now they are proven to display flexible multimodal signaling, advanced parental care and highly coordinated group hunting tactics."