Starving snakes devour own hearts
Some snakes can survive without food for two years at a time by digesting their own hearts, a new study shows.
Other snakes survive by growing bigger heads to broaden prey options during periods of famine.
The US study, published in the latest issue of the journal Zoology, is the first to examine starvation physiology in snakes.
Author Marshall McCue, a researcher in the Department of Biological Sciences at the University of Arkansas, thinks intense snake hunger may even explain some of the more outrageous snake stories from recent years.
"Severe hunger might make snakes take greater risks than otherwise," says McCue, referring to stories of pythons eating alligators and "popping open", or stories of escaped pet snakes eating unusual objects, like unused light bulbs.
For his study, McCue put 20 ball pythons, 22 ratsnakes and 20 western diamondback rattlesnakes through 168 days of starvation. He then weighed and measured them at regular intervals.
McCue then chemically euthanised each snake and pureed it in a blender to better conduct chemical analysis.
At the 168th day, the snakes lost about 9-24% of their initial body mass. They also reduced their energy expenditures by an average 80% over the test period.
McCue says the snakes were usually sedentary, wrapped up in provided "hide boxes", and only explored their environments when they thought a potential food source was around.
Measurements revealed the snakes actually grew longer during the fast. He especially noticed that their heads had grown.
"Larger head bones mean that they can choose from a wider range of potential prey items," he says, noting that snakes cannot chew and therefore must swallow whole animals.
Breaking down fats
The chemical analysis determined the snakes break down saturated fatty acids into polyunsaturated fats by "picking off bits of hydrogen for energy".
Intestinal fat, which he likened to "belly fat" in humans, as well as fatty liver tissues were among the first to be targeted.
As a by-product, water formed in the snakes' bodies, causing them to bloat by around 7%.
Then the snakes would digest their own heart muscle.
The heart breakdown initially surprised McCue, but he says it is reasonable given that "the lower energy expenditure allows lower circulatory demands, and therefore permits the heart organ to shrink".
Immediately following a nutritious meal, snake hearts can quickly rebuild themselves.
Dr Aaron Rundus, a University of Nebraska researcher who has also studied snakes, says he is surprised to learn snakes can survive without eating for up to two years.
"[But] I completely believe it, and the physiological mechanisms make sense given how successful these reptiles are at surviving under the worst of conditions."
Rundus says that snakes are ambush hunters, as opposed to strategists, so they must wait for incredibly long periods before an unsuspecting victim crosses their paths.
McCue hopes future studies on snake starvation will lead to treatments that can increase food deprivation tolerance in other animals, including humans.