December 5, 2013
Crocodilians Use Lures To Catch Nesting Birds
Brett Smith for redOrbit.com - Your Universe Online
Alternately lethargic and viciously violent, crocodilians are not often thought of as cunning, duplicitous predators. However, a new study in the journal Ethology, Ecology and Evolution has found that these massive reptiles sometimes use sticks and twigs to lure in unsuspecting birds, particularly during nest-building season.
"Our research provides a surprising insight into previously unrecognized complexity of extinct reptile behavior," suggested study author Vladimir Dinets, a research assistant professor in the Department of Psychology at the University of Tennessee. "These discoveries are interesting not just because they show how easy it is to underestimate the intelligence of even relatively familiar animals, but also because crocodilians are a sister taxon of dinosaurs and flying reptiles."
The study focused on two crocodilian species—marsh crocodiles, or muggers, and American alligators. The research team said their study is the first to report tool use by any reptiles and the first known case of predators timing their use of lures to the seasonal activities of their prey.
Dinets said he first observed the behavior in 2007 when he saw crocodiles in shallow water near the edge of a pond in India with small twigs laying across their snouts. The sticks fooled nest-building birds into wading into the water. After lying still for hours, the crocodiles would lunge when a bird neared the stick.
Dinets told The Telegraph that the muggers living in the marshes of India were able to fool some larger birds.
“On one occasion, an intermediate egret approached one of the crocodiles and stretched its neck towards the stick,” he said. “The crocodile lunged at the bird.”
To further investigate this behavior, Dinets and his colleagues observed the reptiles for one year at four sites in Louisiana, which included two bird breeding ground sites and two non-breeding sites.
The researchers saw a significant increase in alligators prominently displaying sticks on their snouts from March to May, nest-building season. The team also saw that the reptiles in the breeding, or rookery, sites used the lures during and after the nest-building season. At non-rookery locations, the reptiles used lures only during the nest-building season.
Dinets added that juvenile crocodilians did not exhibit this same behavior. He said the narrowness of their snout could be a limiting factor.
"This study changes the way crocodiles have historically been viewed," said Dinets. "They are typically seen as lethargic, stupid and boring but now they are known to exhibit flexible multimodal signaling, advanced parental care and highly coordinated group hunting tactics."
While American alligators are fairly common, muggers are considered ‘vulnerable’ by the International Union for the Conservation of Nature (IUCN). The muggers’ range stretches from the Middle East to nearly China.
A freshwater species of crocodiles, muggers prefer shallow lakes, marshes or slow-moving rivers. Muggers are considered to be more mobile on land and will travel sizable distances over land in search of a better habitat. They will also chase prey on land for short distances. They have been known to dig burrows for shelters during the dry seasons in Southern Asia.