Starving Snakes Conserve Energy
Superb Energy Reduction Enables Reptiles’ Survival Without Food
Nov 8, 2007
Scientists have long known that snakes can survive periods of up to two years without food, but it was not clear how they did it. Now a biologist from the University of Arkansas says it’s because snakes can lower their standard metabolic rates, by up to an amazing 72 percent.
What is even more surprising is that they can continue to grow even while they are starving.
“These animals take energy reduction to a whole new level,” said Marshall McCue, a graduate student in biological sciences in the J. William Fulbright College of Arts and Sciences.
He reported his findings in the journal Zoology.
McCue discussed his research in an email interview. Until now, he said, no studies have examined the physiological changes that a snake undergoes when living for prolonged periods without food. McCue examined 62 individuals from three snake species – the ball python, the rat snake and the western diamondback rattlesnake – to study their responses to prolonged periods without food.
Lowering Their Metabolic Rates
The reptiles went for about six months without eating – a situation which could be quite likely in the wild, where food supplies can be scarce. McCue then looked at changes to the snakes’ physiology, morphology, and composition.
The results showed that the snakes could lower their standard metabolic rates, some by up to 72 percent.
“Snakes already had low energy demands. We didn’t know they could go lower,” McCue said.
He was even more surprised to discover that the reptiles were growing, despite the lack of food. McCue said this fact does not appear in previous research literature.
Efficient Use of Available Resources
“To me, this suggests that there must be a strong selective advantage to growing longer,” he said. “It also means the snakes have become extremely efficient in their ability to use available resources.”
He explained that snakes were extremely efficient at managing their metabolic supply and demand.
“When you’re cut off from resources, you are an organism that still needs to expend energy,” he said. “The ‘demand’ end is met by decreasing their metabolic rate. The ‘supply’ end must be met by frugal use of resources they have at hand for energy, which comes from within.”
Fat and Protein: Energy Sources from Their Bodies
Compositional analysis shows that snakes’ bodies include water, ash, protein, fats and carbohydrates. McCue found the snakes used up selected fat stores first during the starvation period. However, different species used up their fat stores at different rates, before breaking down their body proteins for energy.
Rat snakes, which eat rats and small rodents, and typically have a more abundant food supply in their natural environment, began to break down proteins faster than the pythons or rattlesnakes.
“The protein use was higher in the snakes less well adapted to starvation,” McCue said.
Evolutionarily Successful
Although snakes are evolutionarily the new kids on the block of the reptiles, having only been around for about 100 million years, they comprise about half of all reptile species. McCue attributes this to their success in surviving harsh environments.
“Snakes are very evolutionarily successful,” he said. “Understanding the physiology that allows them to succeed in low-energy environments will help scientists further their understanding of the snakes’ evolution and their adaptation to their current ecosystems.”
Meanwhile, he said, his findings could be used in conservation strategies to determine the health of snake populations.
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