Ireland's Ancient Hyenas
Over the last few months we have seen how today’s elephants once had ancient relatives roaming through the Irish landscape. However, other exotic mammals inhabiting warm climates in our modern world can also claim ancient relations which braved the bitter cold of Ice Age Ireland. If we could hop back in time to around 40,000 years ago and stand at the foot of the Ballyhoura Hills in Co. Cork, or many other locations in southern Ireland, our ears would be greeted by the sounds of a rich mammalian chorus. The blasting trumpets of woolly mammoths and bellowing brays of giant Irish deer would mingle in the air with the stuttering yelp of arctic foxes and the deep, throaty roars of brown bears. But cutting through this ancient soundscape would be a strange yet unmistakeable howl – the eerie laugh of the spotted hyena.
Of all of Ireland’s Ice Age mammals, the spotted hyena (Crocuta crocuta), also known as the laughing hyena, is surely the one we would least expect to have been present. Whereas other mammals like the woolly mammoth, giant Irish deer, brown bear, arctic fox, reindeer, etc., all fit the picture of the type of life you would expect to see in an ancient, freezing Ireland, the spotted hyena is a mammal we are more used to seeing in modern nature documentaries bounding across the sun-drenched African savannahs, taking down exotic herbivores like gazelles, zebras, and wildebeest, or scavenging on bloody carcasses. But though today spotted hyenas are only found in Africa, during the Ice Age their deadly presence could be felt across far greater swathes of the Earth, as they also ranged widely across Europe and Asia.
However, the emergence of spotted hyenas was one of the latest events in the evolution of the hyena family, and to truly understand the origins of this species, and how they ended up in Ireland, we must go back to the very beginning and trace the hyenas’ story from their first appearance on Earth.
It is not known on which continent the hyena family first appeared. Although today three of the four living species are confined to Africa (the spotted hyena, brown hyena, and aardwolf, with only the striped hyena found farther afield) it is quite possible that hyenas first evolved elsewhere. In fact, the earliest fossils of hyenas have been found much closer to Ireland, in southern France, and date from around 17–16 million years ago.
However, whether the hyenas actually evolved in western Europe is unknown, and it must be noted that fossils from China are only slightly younger, while the earliest fossils from Africa, dating from around 14 million years ago, may not indicate their first presence there as Africa lacks appropriate fossils from the early days of hyena evolution. Yet, we can at least say that western Europe is one of the possible locations for the origin of the hyenas, and that the earliest fossil hyenas lived in southern France at a time when Ireland is thought to have been joined to this land through Britain.
But what were these earliest hyenas like? What was the ancestral form from which the spotted hyenas of Ice Age Ireland and modern Africa would ultimately evolve?
Well, before we delve into the nature of these ancient hyenas, it might be useful to first explore our conception of what a hyena is. When we think of a ‘hyena’ today, most of us probably picture the spotted hyena, which, at an average of 50–60 kilograms, is relatively large and has a short, robust skull perfectly adapted for crushing bones. And this form is also seen in two of the other hyena species, the brown hyena and the striped hyena, which are a little smaller, weighing roughly 40 kilograms and 30 kilograms, respectively. However, the fourth hyena, the little aardwolf of eastern and southern Africa, is far different.
At around 10 kilograms in weight, the aardwolf is much smaller than the other hyena species and it also has a much more slender skull and peg-like cheek teeth not adapted for bone-crushing but for crunching the termites it specialises in feeding on, which it snaffles up by licking the soil. Indeed, this is where its name comes from, ‘aardwolf’ meaning ‘earth wolf’ in Afrikaans. The aardwolf, then, with its more primitive general form allied with its more recently-evolved specialised teeth, shows us that there is more than one way to be a hyena in the modern world, but in the past the diversity of hyenas was far greater.
Although only four species of hyena have survived to the present day, over 80 hyena species are known from the fossil record, and the hyenas were once one of the most successful and diverse carnivore families on Earth. Indeed, the oldest fossil hyenas, those which lived in southern France around 17–16 million years ago, were, like the modern aardwolf, far different to the spotted hyenas inhabiting Africa today.
Modern spotted hyenas, despite their almost comical countenance, with a sloped back and high-pitched ‘laugh’, are highly efficient killers which operate in co-operative clans and are capable of capturing prey much larger than themselves. Their earliest fossil relatives, however, were not powerful terrestrial hunters and bone-crushing carnivores, but likely lived partly in the trees where they existed on a diet of birds and insects and small mammals.
These ancient hyenas were far smaller creatures than their deadly modern spotted hyena relatives, with some resembling mongooses (which are themselves quite weasel-like), while others looked like civets, which are mostly small, long-bodied, short-legged, cat-like creatures that live in the tropics of the Old World today. And while hyenas of this form would persist for over 10 million years, they were soon joined by larger hyenas, although these were also quite different to our spotted hyenas in form, being more like jackals or foxes.
But though these larger hyenas were less adapted to running than the modern canids (i.e., members of the dog family) they resembled, forms that were more suited for running did eventually appear, and some may have hunted in packs like wolves. One of these, Thalassictis, has been found in east/southeast-central France, dating to around 13–11 million years ago, so was conceivably present in Ireland too, and seems to have been well suited to the open woodlands of this time.
The early hyenas, then, did not display what we would think of as the ‘typical’ hyena form seen in spotted hyenas today, but were far more like other members of the Carnivora order, such as civets, mongooses, and canids like foxes, jackals, and wolves. However, by around 12 million years ago, it is clear that two groups of hyenas were evolving in different directions and the typical hyena form of today was emerging.
Although some hyenas became ever more dog-like and suited to running, and the teeth became better adapted for shearing flesh than for cracking bones, others began to evolve the more familiar form we see in the three larger hyena species today, displaying, like the running forms, an increase in size over time, but unlike them most evolving teeth which were far better for cracking bones than for slicing flesh.
Adcrocuta, which first entered western Europe around 10 million years ago, was quite like modern spotted hyenas, being quite large (around 70 kilograms in weight) and having a very similar form, including the fully-adapted bone-cracking skull. Although the canid-like and ‘running’ hyenas were also able to consume bone, Adcrocuta was the first to be a true specialist, and although it is not thought to be ancestral to the spotted hyena genus Crocuta, it is thought to be its closest known relative, even when the living forms are included.
The extinct Adcrocuta, then, diverged from the line leading to the living spotted hyena only after the spotted hyena's line had already diverged from those leading to the rest of the modern species in the hyena family. The three typical modern hyenas – that is, the spotted hyena, brown hyena, and striped hyena – are thought to have last shared a common ancestor just over 11 million years ago. The ancestor of the aardwolf is thought to have diverged earlier, with some arguing it split from the rest of the hyenas very early in their evolution, around 20 million years ago, and possibly evolved from one of the early civet-like forms, while others think it diverged just before the others and evolved from a meat-and-bone-eating member of the more dog-like running hyena lineage.
In any case, though the lineage leading to the genus of the spotted hyena, Crocuta, is thought to have diverged from the line leading to the other large modern hyenas by around 11 million years ago, the first fossils which can be ascribed to the genus itself only appear far later, just under four million years ago in East Africa. By this time, there had been a great switch of power in the hyena family, and although some canid-like and running forms were still plying their trade, it was now the more modern bone-cracking hyenas that were ascendant.
It was in Africa, then, that the genus Crocuta, to which Ireland's ancient spotted hyenas and their modern African relatives belong, seems to have originated, and from here they dispersed to invade Europe and Asia. However, while the deeper origins of the spotted hyenas which would come to inhabit Ireland can be traced to Africa, where the oldest fossils of the Crocuta genus are found, it is now thought that the spotted hyena species itself, Crocuta crocuta, may actually have emerged in Eurasia.
Although earlier models of the spotted hyena’s evolution envisaged an origin over three million years ago in Africa followed by possibly three dispersal events into Eurasia, this does not seem to fit with the current view of early Crocuta fossils, which are ascribed to extinct species rather than the modern one.
A 2014 study noted that the earliest forms of spotted hyena appeared in China as recently as 400,000–230,000 years ago, while the earliest European forms appeared only sometime after 300,000 years ago. This study has proposed a model whereby an ancestral population of spotted hyenas on the vast grassland steppes of Eurasia began to fragment, possibly due to environmental change, leading to the divergences of the spotted hyenas into a number of groups beginning around 430,000 years ago.
This divergence led to the extinct lineages, whose members include those which would eventually invade Ireland, and to the living lineages which are only thought to have invaded Africa from Eurasia towards the end of the Ice Age. Thus, Africa became the new homeland of the spotted hyena, where they have become one of the most characteristic members of its mammal fauna.
So, it seems the spotted hyenas which gambol and grimace under a fierce sun in Africa today hail from ancestors which emerged on the frigid grasslands of Ice Age Eurasia, and may have retreated to the vast African continent as their grassland habitats receded from their northern ancestral lands as the Age of Ice ended.
Far from being the odd-one-out in Ice Age Ireland’s mammalian fauna, then – a heat-adapted mammal miserably enduring the Arctic temperatures of the ancient Irish landscape – the spotted hyenas prowling around the Ballyhoura Hills 40,000 years ago were inhabiting an environment they were perfectly at home in. And this simple fact seems to lay bare the true nature of the spotted hyenas: that long before they cackled in the heat, they were laughing at the cold.