What the longest woolly rhino horn tells us about the beasts’ biology
Like tree rings, bands in the horn show the extinct herbivores could live to at least 40 years
The woolly rhino (depicted in this 3-D animation) has long been extinct, but preserved remains, including the recent discovery of the longest horn yet, are providing new clues to their lives.
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The longest woolly rhino horn ever found is providing new insights into the lives of these now extinct animals.
The horn — found preserved in Siberian permafrost — stretched over 1.6 meters, nearly the size of a small adult human and a full 30 centimeters longer than the previous record holder, researchers report September 12 in the Journal of Zoology.
A local hunter and fisherman found the horn and complete skull along a small tributary of Russia’s Kolyma River. He sent the remains to the Mammoth Museum in Yakutsk for examination by researchers. Frozen lemmings found near the rhino remains were sent to Novosibirsk for carbon dating and showed the remains are about 19,600 years old.
Woolly rhinos (Coelodonta antiquitatis) were related to modern rhino species, last sharing a common ancestor with the Sumatran rhino about 9 million years ago. The ancient horn is longer than those of any modern rhino species, say Ruslan Belyaev, a vertebrate zoologist at the A.N. Severtsov Institute of Ecology and Evolution in Moscow, and his colleagues.
But the giant horn didn’t belong to a particularly giant individual. The skull bearing the horn was proportionally small for an adult woolly rhino. The researchers think it belonged to a female, because among modern rhino species, males are usually larger than females. Male woolly rhinos appear to have had thicker horns. But the longest horns may have belonged to females, as is the case in modern rhinos from Africa. It’s unclear if the longer horns in female woolly rhinos are due to faster growth or slower wear, Belyaev says.
The rhino was also quite old when she died. Rhino horns grow from their base, depositing layers of keratin that alternate between light and dark bands in accordance with seasonal fluctuations, similarly to tree rings. The team counted these layers and determined the rhino lived at least 40 years, the oldest woolly rhino yet found. This is a few years older than the maximum age of modern wild rhinos, and comparable to the oldest captive rhinos.
“For the first time, we were able to show that in the harsh conditions of the Ice Age, woolly rhinos could live as long as modern species,” Belyaev says.
The length of the horn may have been particularly important for woolly rhinos’ survival. Unlike modern rhinos, they’re thought to have used the unusually flattened, saberlike horn to brush away snow when feeding. Wear on the front of the woolly rhinos’ horns examined in the study extended nearly half the breadth of the base, says Gennady Boeskorov, a paleontologist at the Diamond and Precious Metals Geology Institute in Yakutsk.
Luca Pandolfi, a paleontologist at the University of Pisa in Italy not involved with this research, wonders if woolly rhino horns could provide any insights to ancient climate changes. It would be interesting to know, he says, if climate could influence horn characteristics, and if colder winters left behind detectable signals in the horns’ growth banding.
