Giant Poisonous African Crested Rat Uses Plant Toxins for Defense

The African Crested Rat has been found by scientists to utilize plant toxins for defense. The African Crested Rat (scientific name: Lophiomys imhausi) is a gray rodent that is the size of a rabbit and looks like a puffy skunk.

The fascinating feature of this animal is its poison-laced fur that can kill even an elephant. Just a few milligrams of the poison is lethal to humans.

Unique mammal

Researchers from the National Museums of Kenya, the University of Utah, and the Smithsonian Conservation Biology Institute reported that it is the only recognized mammal that sequesters plant toxins to be used for defense. When it encounters threats, the rat raises the hairs on its back to warn enemies.

It also has an unusual social life, where it is apparently monogamous which also possibly forms family units.

The research article can be found in the Journal of Mammalogy.

Elusive and mysterious

According to lead study author, University of Utah postdoctoral researcher, and Smithsonian-Mpala post-doctoral fellow Sara Weinstein, they first set out to confirm the rat's sequestration of the toxin.

As they proceeded in their research, they also discovered an unusual social behavior in the animal.

Poison arrow tree cardenolides

In the region of East Africa, people have long thought that the rat was indeed poisonous. The poison of the poison arrow tree (scientific name: Acokanthera schimperi) has been traditionally used in arrows, whose active ingredients are cardenolides.

These compounds are similar to the poisons of monarch butterflies and cane toads, as well as some heart medications in humans. Cardenolides, especially the ones in the tree, are very toxic to the majority of animal species.

According to the University of Utah's Denise Dearing, study co-author, one major goal of their research was to determine how unusual their behavior is.

Social behavior

According to Museums of Kenya Mammals curator and study co-author Bernard Agwanda, everyone used to think that the animal was solitary.

When Weinstein and a co-researcher put two rats in an enclosure, they began to purr and groom one another. The scientists then studied their behavior and found that they appeared to be monogamous. They appeared to spend extensive time with offspring, and touched one another over half the time, and followed one another frequently.

They also employed a wide repertoire of sounds, including special purrs, squeaks, and other verbalizations. These would need further studies on behavior to flesh out the details of their family and reproductive life.

Immune to the Acokanthera

As part of the study, the researchers offered poison arrow tree branches to the rats. Those who sequestered it chewed the plant and mixed spit with it. They then licked it on their hairs.

The rats seem to be impervious to the Acokanthera toxin and milkweed exposure. It seems that the rats are also selective in the cardenolides they used.

Conserving the rats

The particular species of rat in question is of least concern as far as the IUCN Red List is concerned. According to Agwanda, they may be in trouble, particularly due to apparently decreasing numbers. They used to be common roadkill victims.

Agwanda says that they now have a hard time encountering and trapping them, which means their population may be dwindling. Studies in the future may shed more light on their behavior, physiology, and conservation status.

Agwanda is currently constructing an African Crested Rat exhibit in the Museums of Kenya for increased public awareness on this unique and poisonous mammal which unusually uses plant toxins.

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