A Moment of Science

Do Poisonous Rats Exist?

Is there such a thing as poisonous rats? (We think it would make a great horror movie!)

acokanthera flower

Photo: Tim Waters (Flickr)

Flowers from the acokanthera tree.

Everyone’s heard about poisonous mushrooms, venomous snakes, even poisonous frogs. But what about poisonous rats? It appears that African crested rats are poisonous to predators, but their poison doesn’t come without some effort.

All About Crested Rats

Crested rats live in forests and woodlands in eastern Africa where they eat mainly leaves, roots, and other plant materials. They look more like small porcupines than rats with their long, black tipped hairs. Sometimes they’re called maned rats because a ridge of longer hair runs from their heads, along their back to the base of their tail. This mane erects when they are threatened or anxious.

Crested rats do not produce their own poison like the duck billed platypus, which has a poisonous spur on its hind foot, or Solenodon shrews which make poisonous saliva. Instead, it steals its poison from the acokanthera tree.

Poisonous Cardiac Glycoside

The acokanthera is a small, round leaved tree with dark colored berries. Its bark, wood, and roots contain a poisonous cardiac glycoside which will cause death by speeding up the heart until it loses its rhythm. Native Africans have used the tree’s bark to produce poison arrows to kill game for generations. Crested rats make use of the poison in a similar way, only they use it for protection.

The rats gnaw and masticate the bark, avoiding the more potent leaves and fruit, and apply the saliva to their flanks. Interestingly, the spongy, absorbent nature of the rat’s long hairs allows the hair shafts to rapidly absorb the poisonous saliva.

Crested rats rarely grow to more than two pounds in weight, but their long black and white flank hairs send a warning to all who approach. A bite of this rat might be your last one.

  • sue anne zollinger

    There are just a couple small errors in this script, the duck-billed platypus and Solenodons are actually venomous rather than poisonous. They inject their toxins (either by biting (solenodons) or spearing with the spur (platypus)), but aren’t poisonous. This means you could eat either of them safely (assuming you don’t get bitten/speared in the process).

     In contrast the crested rats make themselves poisonous to potential predators by coating themselves with the poison of the acokanthera tree.  The rats themselves are actually not poisonous either, if you remove their poison-coated fur.

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