While squirrels snuggle up to hibernate through frosty winters, some frogs and toads estivate to escape unbearably hot and dry summers. Cocooned underground during the heatwave, they fast for months and emerge to feast when the monsoons start. Curious about the digestive consequences of estivation,Stephen Secor examined whether three estivating anuran species show different responses to fasting and feeding than their non-estivating relatives(p. 2595).
Estivating frogs and toads face the same metabolic challenges as sit-and-wait predatory snakes, which often go without a meal for a long time. These snakes have a simple solution to save energy and survive longer on their limited energy stores; they simply shrivel up their guts while they're fasting and then pump them up again when they get lucky and snare a hapless victim. Do estivating anurans do the same thing?
To find out, Secor compared the digestive action of estivating and non-estivating frogs and toads after they wolfed down a meal following a two-week fast. When the three estivating species devoured newborn rats, he noticed a spectacular doubling of intestine mass and a 6- to 10-fold surge in their guts' nutrient uptake. But the non-estivating species' response was less impressive; Secor saw a modest 50% increase in intestine mass and a 69%increase in nutrient uptake. When he triggered estivation by dehydrating two of the estivating species, he saw that after one month of estivation their gut mass had dropped by 44% and their nutrient uptake by 60%. Secor concludes that estivating anurans have adopted the same strategy as sit-and-wait snakes to save precious energy while they wait for conditions to improve.