In the spring of 2005 during their mating season, toads in Germany and Denmark began exploding. Spewing guts, blood and skin for nearly a yard in every direction; the disturbing phenomenon at first baffled concerned scientists, although they eventually discovered the cause of the fatal condition.

Pools of Death

Observed near two ponds during that spring, one in the Altona district of Hamburg, Germany, and the other near Laasby in Jutland, Denmark, some of the explosions were actually witnessed by environmental scientists.

First, they began with “several minutes” of “agonizing and twitching” followed by the toads blowing up like a balloon, and then culminating in an explosion. As the environmental workers noted, after “the toads burst, the entrails slid out. But the animals [weren’t] immediately dead – they keep struggling for several minutes.”

With no explanation at hand, scientists with Hamburg’s Institute for Hygiene and the Environment tested the pond’s water quality, searched for a fungus or virus (the latter of which was hypothesized to have been transmitted from horses at a nearby race track), and even considered the somewhat fantastical notion that the toads may have been purposely killing themselves to prevent overpopulation.

(Aside: Ants sometimes do something like this, for the good of the colony.  Specifically, certain species of ants have suicide bomber ants.  When these suicide bomber ants encounter enemies, such as ants from another colony, they will literally explode, causing a chemical to cover the enemies around them.  This chemical is extremely sticky and when it dries will immobilize any enemy ants, eventually resulting in them dying.

The Forelius pusillus ant also has worker ants that will sacrifice themselves for the good of the colony, but this time in a slightly different manner than the exploding ants.  Every night, the nest of a colony needs sealed off in such a way that the nest will be undetectable from the outside, in order to protect it from predators.  As such, sick ants or ones who are older will apparently volunteer to perform the task of staying outside the nest at night.  Once all the rest of the ants are inside, the sacrificial ants will seal up the entrance and usually will end up dying from being left outside.  Even when researchers have collected these sacrificial ants and taken care of them, they usually die soon anyways, which is why it is thought that generally older or sick ants are chosen for this task.)

In any event, each of these theories on the exploding frog front were rejected, and authorities were forced to warn residents away from the pools until an answer was found.

Eureka! 

An eminent amphibian expert from Berlin, Dr. Frank Mutschmann, carefully examined live and dead specimens and noticed several interesting facts:

• Each had a small circular incision on its back
• Each was missing its liver
• None had any other bite or scratch marks

This last was especially significant, since it proved that neither rats nor raccoons were attacking the toads. Of particular note, however, was the size of the circular incision, which matched the size of a bird’s beak. Knowing how clever crows are, Dr. Mutschmann theorized the birds were aware that the toad’s skin was poisonous, but that the nutritious liver could easily be popped out with little toxic exposure.

His theory also explained how the toads’ exploding reaction appeared to come well after they lost their livers. Since it was mating season, the toads would have been so distracted by their biological imperative that they wouldn’t have paid heed to a few quick pecks:

Only once the liver is gone does the toad realize it’s been attacked. It puffs itself up as a natural defence mechanism. But since it doesn’t have a diaphragm or ribs, without the liver there is nothing to hold the rest of its organs in. The lungs stretch out of all proportion and rip; the rest of the organs simply expel themselves.

After Dr. Mutschmann’s explanation came to light, besides being confirmed, it was soon discovered that exploding toad epidemics have happened before in Germany and Denmark as well as in Belgium and the U.S.

If you liked this article, you might also enjoy our new popular podcast, The BrainFood Show (iTunes, Spotify, Google Play Music, Feed), as well as:

• Seagulls Will Not Blow Up if They Eat Alka-Seltzer (Or Rice for That Matter)
• The Curious Case of Exploding Head Syndrome
• Why Do Mentos and Diet Coke React?
• Honey Bees Know the World is Round and Can Calculate Angles
• The Exploding Anti-Tank Dogs of World War II

Bonus Facts:

• A group of crows is called a murder, while a group of toads is called a knot.
• Crows are among the smartest birds, and scientists have learned they can remember a person’s face, have complex communications (and maybe even a language), engage in problem solving and even use tools. (Incidentally, contrary to popular belief, Goldfish are also quite intelligent and can recognize their masters.)
• The common toad is one of the most prevalent amphibians in Europe. Toxin glands abound on its skin, and two notable parotoid glands (the two bulges just behind the toad’s eyes on the back of its head) secrete bufotoxin, a neurotoxin, when attacked. Toad poisoning can cause gastrointestinal, cardiac and neurological symptoms.
• Liver is an amazingly nutritious food. Beef liver supplies vitamins A, B6, B12, D and E, folic acid, biotin, thiamin, riboflavin, niacin, pantothenic acid, calcium, phosphorus, magnesium, potassium and zinc. In addition, it has twice the iron of other red meat, vastly more copper and even three times the vitamin C of an apple.  The extreme level of Vitamin A, however, makes it a poor choice for a food for pregnant women.
• Many are concerned that liver from commercially processed animals may contain more toxins than other meats because the liver “is a filter.” Experts, however, note that the liver is more complex than a filter and can actually convert toxins into other substances and expel them from the body. They agree that the liver will accumulate toxins, but say in no greater amounts than the rest of the animal’s meat. As one concluded, “if you avoid liver because of toxins, you should probably avoid the rest of the animal, too.“