Home Animal Hippos’ oversize entrance enamel make it laborious for them to chew

Hippos’ oversize entrance enamel make it laborious for them to chew

Hippos’ oversize entrance enamel make it laborious for them to chew


Hippos are horrible at chewing, and their large tusks and entrance enamel are guilty.

These intimidating dental options are utilized by hippos, partially, to guard themselves and their territory. However a few of the gnarly enamel interlock or hinder jaw actions, stopping hippos from effectively chewing with the side-to-side grinding approach that different herbivores use, researchers report October 4 in PLOS ONE

Plant-eating mammals sometimes use the broad enamel close to the edges of their mouths to grind and shred fibrous vegetation earlier than swallowing it. Since their digestion course of barely reduces meals particle measurement, you possibly can gauge chewing effectivity by taking a look at their feces.

In 2009, veterinarian Marcus Clauss of the College of Zurich and his colleagues in contrast the sizes of fecal particles throughout practically 200 mammal species. They discovered that hippos have been the least efficient chewers amongst herbivores. Years later, he and his colleague Annika Avedik puzzled whether or not hippos’ monumental entrance enamel have been the reason for their meager munching. 

Some herbivores, similar to deer and cattle, have misplaced a few of their entrance incisors throughout evolution, presumably as a result of they impeded chewing. African rhinos have misplaced theirs solely. “Hippos are a case instance of a taxon that didn’t lose them,” Clauss says.

The researchers analyzed movies of frequent (Hippopotamus amphibius) and pygmy hippopotamuses (Choeropsis liberiensis) consuming, intently monitoring how the enamel interacted because the jaws moved. The workforce additionally measured bodily options of 86 frequent hippo and 21 pygmy hippo skulls in museum collections, together with the spacing and association of the enamel, and examined the side-to-side jaw vary of those skulls and measured locations the place the enamel wore on one another. 

Clauss had initially thought that frequent hippos’ enormous tusks, that are modified canine enamel, can be what stopped the animals from correct side-to-side chewing. “Boy, was I unsuitable,” he says.

As an alternative, the workforce discovered that frequent hippos’ higher and decrease units of lengthy, spearlike incisors cross and interlock because the decrease jaw closes, proscribing the again enamel to up-and-down mashing. The herbivores nonetheless attempt some side-to-side motion of the jaw, Clauss says, evidenced by put on marks on the edges of the incisors.

A photo of a hippo skull on a black background.
Skulls of frequent hippos (Hippopotamus amphibius) like this one confirmed researchers that the highest and backside incisors interlocked throughout chewing, holding the jaw from transferring facet to facet.Michelle Aimée Oesch (CC-BY 4.0)

Pygmy hippos’ incisors don’t interlock, however their tusks bump up in opposition to the snout, permitting solely a restricted quantity of facet sliding. Put on patterns present that the incisors glide previous one another when chewing.

As a result of pygmy hippos present some side-to-side jaw motion when chewing, it hints that “lateral grinding chewing is one thing [hippos] as soon as did, and that it obtained misplaced alongside the way in which,” Clauss says.

Hippos now use their inflexible jaws, vast gapes and sharp, sturdy tusks and incisors, partially, to fight different hippos over territory and entry to mates, and to defend in opposition to predators. However the potential shift to much less environment friendly chewing may have include penalties. As a result of hippos can’t mulch meals into very small items, it takes longer for it to be digested, Clauss says.

“If meals has to remain longer within the intestine, it means one can not eat extra, rapidly. Therefore hippos are, amongst mammalian herbivores, characterised by comparatively low meals intakes,” he explains. 

Their comparatively low meals consumption could put hippos at a aggressive drawback in opposition to different, extra effectively chewing ruminant herbivores similar to antelope. An lack of ability to compete with totally land-dwelling species for ample meals could preserve hippos wedded to the African waterways the semiaquatic animals name house.

The research is “a extremely good reminder of the complexity of organisms, and that when anatomical elements, similar to enamel, are considered in isolation, they might not clarify the entire image,” says comparative biomechanist Susan Williams of Ohio College in Athens.

Learning fossil hippo ancestors may reveal if, and when, hippos’ side-to-side movement throughout chewing stopped, rounding out understanding of the animals’ evolutionary story. Juvenile hippos additionally don’t but have incisors massive sufficient to interlock, so Clauss is curious to see if these kids quickly use side-to-side chewing.



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