The bundle of nerve fibers that control the elephant’s trunk contains 400,000 neurons, more than we were previously led to believe. This suggests the trunk is remarkably sensitive.
Elephant trunks are likely some of the most sensitive body parts in the animal kingdom.
Michael Brecht at the Bernstein Center for Computational Neuroscience, in Berlin, and her crew dissected the heads of the three Asian elephants (Elephas Maximus) and five African bush elephants (Loxodonta africana).
It’s been documented that many of the animals had lived in zoos and d.i.ed of natural causes, or they had been euthanized because of severe health problems.
Researchers wanted to look at a trigeminal ganglion, a small fluid-filled sac connected to nearby nerves in an elephant’s trunk and face. Each elephant has two of them. “We found that it weighs about 50 grams,” Brecht says. “The human retina weighs about 0.3 grams – so this is really huge.”
Researchers counted around 400,000 neurons in the main nerve coming out of the trigeminal ganglion.
The number of neurons in the optic nerve was more numerous than what was anticipated and only slightly fewer than the number found in an elephant’s brain. Visual nerves typically have many more neurons than nerves related to touch because the optical system is usually much more complicated.
Brecht’s team also concluded that the trunk nerve relating to touch is three times thicker than the optic nerve that goes to the elephant’s eyes. This results in how much information can be carried by neurons and their precision.
“Elephants constantly touch things with their trunk,” Brecht says. “They manipulate things with the trunk, they grasp things – a trunk for an elephant is like having a hand.”
He says this study suggests that elephant trunks might be one of the most sensitive body parts in the entire animal kingdom.
“But, of course, we can’t say this for certain based on just one experiment,” says Brecht.
“The tactile nature of the elephant trunk has been largely overlooked compared to other tactile systems – such as primate fingertips and rodent whiskers,” says Robyn Grant at Manchester Metropolitan University, UK. “It makes sense that the trunk is truly tactile.”
“While we often think about the trunk being moveable and for manipulation, all movement and manipulation are guided by sensation,” says Grant.
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