By Matt Walker
Editor, Earth News
Giant hyenas were true scavengers
Scientists have established how the largest bone-cracking carnivore to have ever lived went about its business.
The giant hyena, Pachycrocuta brevirostris, roamed Africa more than 2.5 million years ago.
Using new evidence uncovered from recently unearthed fossils, and a biomechanical analysis of the hyena's jaws, scientists have worked out what it ate and how.
The study also helps reveal how much the giant hyena hunted or scavenged.
Fossils of the giant hyena were first discovered several decades ago, at a range of sites.
"However, very little was known about its behaviour prior to our studies," Professor Paul Palmqvist told the BBC.
That was until his team unearthed a huge assemblage of Pleistocene fossils at Venta Micena in southeastern Spain.
These mammal remains rest in what is thought to be a den belonging to giant hyenas.
So far, 5,800 identifiable skeletal remains have been found, belonging to 225 animals from 21 types of mammal.
All the remains are thought to have been originally brought to the site by giant hyenas.
Professor Palmqvist's team have used a range of techniques to interpret this assemblage.
These include working out the frequency at which each species was scavenged by the giant hyenas, and which bones the carnivore preferred.
Horse, bison and deer species were a particular favourite of the hyena.
The hyena may have followed other predators, such as sabretoothed cats
Results published in the journal Quaternary International showed that hyenas preferred to crack open bones high in marrow content, breaking into femur and tibia bones from the rear legs, and humerus bones from the front legs of prey.
Other bones were left relatively unscathed.
This preference helps show the giant hyena almost exclusively scavenged rather than preyed on live animals.
Pachycrocuta brevirostris is known as the giant short-faced scavenging hyena.
Fossil remains found at Venta Micena suggest it weighed approximately 110kg, making it significantly larger than modern hyenas and similar in size to a modern lioness.
It is the largest bone-crushing carnivore yet discovered, and had massive limbs, including short, powerful front legs that helped the hyena pick up and drag heavy carcasses.
It also had a heavy powerfully built jaw with robust, well developed teeth.
Analyses of the hyena's jaw also show it must have contained hugely strong muscles to crack large bones with, and was capable of resisting the great stresses that breaking such bones would create.
Thick and strong molar teeth did much of the crushing and cracking of bones.
"Our study has revealed that the force that this hyena was able to exert with its huge premolar teeth for fracturing bones was an order of magnitude higher than in living bone-crackers," says Professor Palmqvist, of the University of Teatinos, Malaga, Spain.
Hyenas and early humans may have competed for food
However, there was a downside to the hyena's immense bone-cracking capability.
The structure of the creature's jaw meant it was not capable of using its longer, sharper canine teeth to bite down with much force.
That means the animal was actually a less effective predator than modern hyenas.
Instead it offset this loss of ability by being a more effective scavenger.
Hyena versus human
One mystery remains, however.
The giant short-faced hyena was a specialised scavenger, but its short, thick front legs, would not have made it a good runner.
That means it was unlikely to have roamed large distances on the look out for carrion.
Instead, the researchers believe it followed other large predators which lived at the same time, such as sabretoothed cats, and stole their kills, or used carrion-eating birds such as vultures to home in on carcasses.
In doing so, it may have jostled with early humans for its meals.
"We have studied this giant hyena using quite different approaches, and all point to an emerging picture of a colossal scavenger that may have represented a serious competitor with hominids for accessing carrion," Professor Palmqvist told the BBC.
The giant hyena in Europe died out around 800,000 years ago, when it was replaced by the spotted hyena, which today weighs just half as much as it giant forebear.
The decline of the giant hyena was probably linked to the decline and subsequent extinction of the sabretoothed cat.