These carnivores might have a reputation as uncouth scavengers, but their modern and fossil history is full of a diverse array of specialized hunters. In this episode, we discuss the surprising modern diversity and the rich fossil record of Hyenas.
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Hyenas belong to the mammalian order Carnivora, alongside cats, dogs, pinnipeds, and more. Though they have a lot in common with dogs, especially in their skulls, they’re more closely related to viverrids (civets, linsangs, and genets) and cats. And though they have a pretty one-note reputation as uncouth scavengers, hyenas past and present are surprisingly diverse.
Perhaps the most famous feature of hyenas – especially if you ask paleontologists – are their teeth and jaws. Aside from aardwolves, hyenas are excellent bone-crushers. They have powerful jaws and huge back teeth that allow them to crack through bone to reach the nutritious marrow inside. This is, of course, great for scavenging, but it also allows skilled hunters like spotted hyenas to make the most use of a kill. In fact, some hyenas have a bit of a reputation for eating basically anything, flesh or bone, fresh or rotten.
Hyenas also have fascinating social lives. While most living species aren’t particularly social, spotted hyenas live in groups that can include several dozen individuals. This species lives in female-dominated societies (the females famously develop pseudo-penises, which might help them maintain better control over mating) and their famous giggling noises are a form of communication. These hyenas are also remarkably intelligent; some have even compared them to primates.
A Diverse History
Hyenas originated in the Oligocene, over 20 million years ago, and since then they have been widespread across Africa, Europe, and Asia. The earliest hyenas were probably small animals similar to civets, but in the Miocene the hyena family tree split into two major lineages: the dog-like hyenas, and the bone-crushing hyenas.
The dog-like hyenas were … well, dog-like. They had wolf-like bodies and skulls, and many were probably skilled pursuit hunters, chasing down prey like canines do today. This group was extremely successful during the Miocene and Pliocene Epochs, including some well-known examples like the jackal-sized Ictitherium and the North American “running hyenas” Chasmaporthetes, which is the only hyena known to have made it to the New World. The dog-like hyenas began to decline near the beginning of the Pliocene, and disappeared during the Pleistocene, possibly due to competition with true dogs once they finally moved into the Old World.
The bone-crushing hyenas were slower to success, but by the end of the Miocene, they had become a dominant group in Eurasia. These included the large and powerful Pachycrocuta, one of the best bone-crunchers of all time, as well as cave hyenas, a subspecies of spotted hyenas that lived in Europe during the Ice Age. Ultimately, the bone-crushing branch of the hyena family tree gave rise to today’s spotted, striped, and brown hyenas, while aardwolves are the sole living member of the dog-like hyenas.
Not Quite Hyenas
The fossil record is full of animals that have been compared to hyenas despite not quite being hyenas. The borophagine dogs were canids specialized for bone-crushing, and their success in the Americas might be one reason why hyenas never moved into the New World. Dinocrocuta was a tiger-sized bone-crusher, part of a family of hyena-cousins called Percrocutidae, which declined around the same time bone-crushing hyenas were on the rise in the Miocene.
Hyaenodonta, a group named for their “hyena teeth,” were a widespread group of carnivoran-like mammals throughout much of the Cenozoic, though they don’t appear to have been bone-crushers despite some dental similarity. And then there are the Borhyaenids, a South American group of marsupial-cousins with powerful bites. Hyenas haven’t been the only mammals to look – and sometimes act – like hyenas.
More Info to Sink Your Teeth Into
The Hyaenidae: taxonomy, systematics, and evolution by Lars Werdelin (Technical)
Skull Shape Evolution In Durophagous Carnivorans, a study of convergent evolution of bone-crushers (technical)
Prehistoric Hyena’s Teeth Show Bone-Crushing Carnivore Roamed the Arctic (non-technical)
Well Spotted: A New Look at the Cave Hyena (non-technical)
The giant hyena Pachycrocuta brevirostris: Modelling the bone-cracking behavior of an extinct carnivore (technical)
More about hyena social behavior:
Inside the Brains of the Bonecrushers (non-technical)
Convergent Evolution: Hyenas Offer Clues To The Human Past (non-technical)
Hyena societies (semi-technical)
The Spotted Hyena (Crocuta crocuta) as a Model System for Study of the Evolution of Intelligence (technical)
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