Sunday 1 November 2015

Teeth of the Giant Honey Badger

Skeleton of a modern honey badger
Honey badgers (Mellivora capensis) have something of a reputation as particularly fierce animals. As is often the case, the reputation is somewhat exaggerated, but it isn't entirely false, either, and they are rather more purely carnivorous than the European badgers of Hufflepuff fame. They are, of course, members of the weasel family, on which I have posted at some length before, and, these days, are usually considered distinct enough to warrant their own subfamily within that group.

According to one study of the evolutionary relationships between mustelids, honey badgers represent one of the earliest branches of the weasel family tree. Assuming a relatively constant rate of genetic change between species after they diverge, and calibrating with the ages of some known fossils, the same study estimated that they should have first appeared about 11 million years ago, during the mid Miocene epoch, and probably in Asia. Naturally, for most of that time, they would not have been the same species that they are today, something that likely arrived much later - it's just that none of their closer relatives survived until the present day.

Back in 1924, palaeontologist Otto Zdansky believed that he had found a fossil of one of those early relatives in China, and named it Eomellivora - the "dawn honey badger". More specimens surfaced over the following decades, but most of them were rather incomplete, and one of the few things we could definitely say about the animal was that it certainly seemed to be rather large - not monstrously huge, or anything, but noticeably larger than the living species, so that the name "giant honey badger" seems quite appropriate.. The fossils, such as they were, also seemed to be somewhat varied, and it wasn't clear exactly whether or not they really belonged to one species (that is, Zdansky's 1924 original, E. wimani) or to as many as eight different, but closely related, ones.

A few years back some unusually complete fossils of this animal were uncovered in Batallones, a hill about 15 miles south of Madrid. This is a well-known fossil-bearing site, and has been particularly useful as a source of the remains of sabre-tooth cats and other large carnivores, although it has also supplied fossils of deer, and of smaller animals, such as mice and amphibians. In this case, the partial remains of at least five giant honey badgers were recovered, including, most importantly, two skulls that were largely intact.

An analysis of these skulls, and some associated lower jaws, has recently been published, trying to put these animals into context, and see what we can learn about them. They had previously been assigned to the species E. piveteaui, first described in 1965 from Turkey, on the basis of half a mandible and a few scraps. The skulls had been dated to around 9 million years ago - not long after the estimated origin of the honey badgers as a group, according to molecular data.

However, the molecular date of 11 million years for the total age of the group is based on educated guesswork, and could easily be overruled if we ever found older fossils. And, in fact we have: one specimen of Eomellivora from Kenya has been dated to around 12 million years ago. Having said which, that belonged to a notably primitive form, one that, among other things, while still larger than a living honey badger, was likely smaller than, say, a wolverine. A not-so-giant badger, then, although probably quite dangerous enough.

This does, however, raise some questions of its own. To start with, are we really sure that this creature was really related to honey badgers? Mustelids have, after all, been around for much, much, longer than this, so isn't it possible that some of those early forms happened to look like badgers without being close relatives? American and European badgers, for instance, represent two entirely separate instances of "weasels" becoming heavy-set and good at digging. Given how much time there has been, the same thing could easily have happened more than once.

To test this possibility, the researchers compared their new skulls with those of two other Eomellivora species, honey badgers, and a number of other possible relatives - pine martens, fishers, tayras, and wolverines. They found clear resemblances, mostly in the shape and relative length of premolar teeth, that linked the fossils to the honey badgers, and not to the other living species - too many resembalcnes to be a coincidence, according to their analysis of the statistics.

They also, by comparing a range of other fossils, identified a total of five species of giant honey badgers. For the most part, they did not live at the same time, although we can't say that each evolved from its predecessor in sequence, not least because there seems to be good evidence that other species did exist, but have left remains too fragmentary to be meaningfully given a scientific name. Most of these species lived in Asia or Europe, aside from that very oldest one in Africa, and one late-dwelling species that seems to have been found in both China and California around 7 million years ago.

So, giant honey badgers were apparently a real thing. And they lived for several million years across a fairly wide chunk of the globe. But what can these skulls tell us about what they were really like?

Let's deal with the obvious bit first: just how big was a giant honey badger, anyway? This can be a bit hard to tell from the skull alone, but if we make the reasonable assumption that the rest of the animal was broadly in proportion to it, and much the same shape as a honey badger is today, they would, on average, have been a little larger than the very biggest living wolverines. Which is to say, about three-and-a-half feet (110 cm) long, and maybe 70 lbs (30 kg) or so in weight. And these, it should be noted, were not the largest species of giant honey badger - those that lived later would easily have dwarfed any mere wolverine.

Possibly not something you'd really want to tangle with.

However, the Spanish fossils, belonging as they did, to five different individuals, also show that there was quite some difference in size between them. This may well indicate that giant honey badgers, like the living species, had males that were notably larger than females. It could be that this why we previously thought there were more species than there appear to be - although, to my mind, the undoubted desire of palaeontologists to be the first to name a "new" species may not be irrelevant, either.

And then, there's the teeth. These form a straight line, and have large, sharp points ideally suited for slicing through fresh meat like a cleaver. This animal was not an omnivore, and it didn't mostly feed on earthworms as European badgers do. Living honey badgers, much as they love honey when they can get it, mostly eat burrowing rodents, but there's a couple of reasons to suggest that giant honey badgers probably didn't.

For one, they are a bit big to bother with rodents, although its likely that they would have eaten some of the larger ones, as well as rabbits, birds, and so forth. But secondly, what we do know of their skeletons suggests that they had quite long legs, rather than the shorter ones of living badgers. So, instead of being burrowing animals, they may well have had at least some ability to chase their prey, pulling them down to the ground to devour them.

What animals? It surely depends on when and where they lived, but in mid Miocene Spain, young deer, piglets, and small antelope would all have made perfectly viable targets.

But it isn't just in their size that the teeth of giant honey badgers differed from those of the living sort. Some of those towards the back of the mouth are wider, stronger, and with blunt edges that differ from the sharper ones elsewhere in the mouth. Those do not suggest slicing meat, although the animal surely could, but instead breaking apart something much more solid. This feature is even more developed in the later (and larger) species, found in central Europe, China, and California. These animals, it appears, could eat bone.

True, they weren't like hyenas, but it seems they had bone-cracking abilities that were at least a match for those of living wolverines. Which means that, like wolverines, they probably gulped down entire carcasses, bones and all, stuffing themselves with everything they could.

Honey badgers are pretty fierce creatures. But giant honey badgers may have been worse.

[Photo by Mario Massone, from Wikimedia Commons.]

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