The Crested Rat (Lophiomys imhausi)
The Crested Rat or Maned rat. A rodent that appears to purposefully acquire a deadly toxin in order to poison its unwary victims.
Article Written by Michael Tomlinson, Edited by, Reginald Finley Sr.
The Crested rat, or Maned rat of Ethiopia/Somalia, is the only animal (besides humans) known to purposefully use extremely toxic substances for defense. Hedgehogs appear to use a similar method but these toxins are much milder and usually considered irritants. It has been suspected that Lophiomys was using poison when dogs who caught them became sick, paralyzed, or died, but they weren’t sure where the rat was getting its poison from. Researchers presented the rat with bark and roots of the Acokanthera plant which is known to have a poison similar to (Ouabain) which is so potent that human hunters in the rat’s habitat, use it to coat their arrows. Ouabain is so potent that it can stop an elephant’s heart!
The Crested Rat is about the size of a house cat. They have warning hair-patterns similar to a skunk and display them when provoked. Special hairs along its flanks absorb poison like a sponge from the Acokanthera plant. It is applied after the rat chews up the bark and transfers the poisoned saliva to the hairs. No one knows exactly why the poison is potent enough to kill a predator, but does not kill the rat. It may have something to do with disproportionately large saliva glands or some adaptation in the digestive tract.
Cresteds have extremely thick skin and a skull and can withstand attacks and abuse. It almost seems to invite being bitten, knowing it has a surprise up its…. hair. It is also unknown whether the behavior is passed on from parent to offspring or is instinctual. It certainly can’t be discovered independently by each individual.
One would think that discovering the plant kills if ingested would warn others not to eat it, more less figuring out if they chew it and rub it into specialized hairs that it will kill predators (if only it didn’t kill them in the process). We may discover in time how it came about, just like the bombardier beetle was thought to be designed because it didn’t blow itself up while evolving. It has been worked out by evolutionary biologists how their defense came about in incremental steps.
There are many protein and sugar-based toxins that can be digested safely in the stomach.. many cannot. When these substances enter the bloodstream, bypassing enzymatic breakdown, these toxins do their most vile work. I wonder if those tiny hairs are projecting into the soft and vulnerable parts of his unwary victims mouths. Sort of like the thin needles of some Jellyfish and siphonophore species. If the hairs or chemicals aren’t penetrating the skin, then the delivery is ingestion alone. So this begs the question, why is the rat okay, but not their victims? Great article! More to discover. – Reginald Finley
Update: 2/2/2018 1:25pm ET – Edited to correct “injects’ position. Editors error. Corrected.