Bombardier Beetles Trapped In A Toad’s Stomach Can Escape

Toads that swallow bombardier beetles without previously killing them could easily regret it. Bombardier beetles trapped in a toad’s stomach are capable of releasing a hot mixture of chemicals which cause their captors to vomit and release the swallowed beetle, even after up to two hours later.

Bombardier Beetles
By L. Shyamal (Own work) [Public domain], via Wikimedia Commons
This story is confirmed by a study released in a paper published in the journal Biology Letters. Researchers used bombardier beetles to test their defense system against two different species of toad. The study is pretty straightforward. Researchers got a number of beetles and a number of toads which they paired up and waited to see what would happen.

It was commonplace for the toads to catch the beetles and swallow them. However, to their surprise, one out of every two or three bombardier beetles trapped in a toad’s stomach would find a way to escape. Their escape would come after an audible burst which could be heard from the stomach of the toad about 15 minutes later. The bombardier beetles would emit a burst of steam and hot chemicals, and the toad would vomit up the beetle.

In order to ensure that the steamy spray of bombardier beetles was what was responsible for this explosion, researchers gathered a second batch of beetles and tricked them into using their defense mechanism. According to Newsweek, they can make more of the mixture, although it takes more time, up to several days. They poked them with tweezers which resulted in the expected response. The beetles instinctively released the boiling chemical. When these beetles were captured by the toads, they would usually meet their grim fate though, as nearly all of the beetles remained trapped in the stomachs of the toads.

Researchers also gave the toads beetles that are incapable of creating the burst of steam and hot chemicals, to completely ensure that the toads were not creating those bursts. As they expected, nothing happened, and the beetles were digested by the toads just fine.

“In our experiments, toads ate non-toxic prey just after vomiting bombardier beetles, suggesting that bombardier beetles did not seriously harm toads,” co-author Shinji Sugiura, an entomologist at Kobe University in Japan, said in an email to Newsweek. “However, toads should be unhappy to swallow the beetles. Therefore, we provided each toad with only one beetle to minimize the negative impacts of the beetles on toads.”

The toads were all released after they completed their part of the experiment in a lab.

Still, their ability to get out of the stomachs of the toads definitely turns out to be useful for bombardier beetles trying to escape being digested by their toad captors.