A salt water crocodile jumps for food near Darwin, Australia.
Credit: J. Patrick Fischer
Most of the world's crocodilians, an order of reptiles that includes crocodiles and alligators, are threatened or endangered. Australia's two species of crocodiles, however, have enjoyed consistent population growth since a ban was placed on hunting in the 1970s.
But now these poorly understood animals face new challenges to their survival, including the effects of climate change and invasive species such as cane toads. The most effective way to help their survival may be to understand them – and, in particular, how they eat.
That's the aim of four scientists, from Charles Darwin University, conservation group Wildlife Management International and Crocodylus Park, all based in Darwin in Australia's Northern Territory. The scientists are investigating the digestive physiology of crocodiles with a long-term goal of improving growth rates of captive animals in the crocodile farming industry.
"With Crocodiles you only have something like 50 years of experience of taking these animals from the wild to domestication," says Grahame Webb, from Wildlife Management International. "But with other animals, such as chickens, there are thousands of years of history.
"When it comes to digestive systems, there is something odd going on. In the wild, crocodiles have a high conversion rate," explains Webb, referring to the amount of food that is absorbed and converted into energy. "In captivity the food conversion rate seems to go way down."
This is a problem for the crocodile farming industry, which exports crocodile skin to be made into leather goods, usually in Europe, and also supplies a growing domestic market for meat.
"Quite probably, crocodiles are not designed to have a full stomach everyday like a cow or a pig," says Webb. "Maybe that is what is causing fundamental differences in how they digest food."
Using recently developed techniques that measure the way nutrients pass through the intestines, the researchers have discovered that crocodiles have a surprising ability to absorb nutrients passively across the intestines. Passive absorption (as opposed to active transport) requires no energy to occur.
The extent of passive transport in crocodiles is comparable to that found in birds and bats – animals that have very high energy requirements. This unexpected result may be due to the fact that crocodiles and birds share a common ancestry – but there's a chance the results were skewed, as the measurement were all taken fast-growing juvenile animals.
Crocodiles diet..
I've heard that crocodiles swallow stones, why is that?
crocs eating stones
helps control their buoyancy which helps them be more effective predators.