An unexpected river horse

In the cool breeze, beneath the shady cover of beech trees in the valley of Kirkdale, North Yorkshire, quarry workers revealed a world long forgotten. It was the summer of 1821, when shrubs and trees were being removed to excavate the cold grey limestone underneath, when they came across bones. Looking like cattle bones, they were thrown into the kilns with the blocks of limestone. Many bones were destroyed in this way, until it was brought to the attention of a certain William Buckland some months later. The site would change the way Buckland viewed ancient fossils, and how the palaeontological community would assess ancient fauna.

Buckland was a strong believer in the literal truth of the bible, and saw fossils as evidence of the Great Flood. Bones and teeth in caves, thought Buckland, were obviously washed there by the Deluge. How else could sites, like Oreston in Devon, hold the remains of elephants and bears that are not around today?

But Kirkdale was different. Buckland was present for the duration of the excavations, and he oversaw everything. There were no rounded pebbles in the cave sediment (as one would expect from water deposited sediments). The bones and teeth showed no sign of being smoothed by water. In fact there were no full skeletons of larger animals; just a lot of teeth and a lot of bone splinters. One species in particular was very abundant; hyenas. It became clear to Buckland that hyenas were using the site as a den, dragging carcasses inside to feast upon.

William Buckland

Witty cartoon of William Buckland poking through a cave to find a hyena den. (Image from here)

The fossils excavated showed what other animals were living around the cave at the time of the hyenas; amongst others, they included rhinoceros, elephants, bear, and hippopotamus. These are pretty exotic creatures that were living in North Yorkshire! In his article about the Kirkdale Caves, Buckland writes (page 185):

“I have information of about 10 elephants’ teeth, but of no tusk…I have seen but six molar teeth of the hippopotamus, and a few fragments of its canine and incisor teeth…Teeth of the rhinoceros are not so rare…”

Buckland correctly suggests that these animals lived a long time ago, but makes no specific comment on the exoticness of the species present. Mammoth fossils were known from other cave sites (although the elephant from Kirkdale was the straight-tusked elephant). Woolly rhinoceros fossils were known as well (the rhinoceros at Kirkdale was a different species, the narrow-nosed rhinoceros). But hippos?! In Yorkshire?!

A big hippo out of the water. (Image from here)

A big hippo out of the water. (Image from here)

At one time during the Pleistocene hippos (Hippopotamus amphibius) were actually very at home in Britain, and across Western Europe (Spain, France, Italy and the Adriatic countries). A surprising number of sites across Britain hold hippopotamus fossils, from the northern site in Kirkdale, Yorkshire, to further south at Yealmpton, Devon.

One of the few large surviving mega-fauna from the Pleistocene, hippos are massive, formidable animals living in Africa, south of the Sahara. Their name, Hippopotamus amphibius, translates from Greek to ‘river-horse’; a rather beautiful poetic name for such a beast. The name comes not from their looks, but from their lifestyle; hippos spend all day living in lakes and rivers in huge pods, mostly submerged beneath the surface. During the evenings, they move onto the land to graze on the grassy banks.

During the Pleistocene, hippos lived happily at much higher latitudes than today. Like the other giants of the Ice Age, they came over from Europe, when the English Channel was little more than a river. Numerous sites across Britain have hippopotamus fossils, including Cambridge, Derby, Leeds, and Trafalgar Square.

Beautiful reconstruction of the fauna of Trafalgar Square, London. (Art by Tabitha Paterson)

Beautiful reconstruction of the fauna of Trafalgar Square, London. (Art by Tabitha Paterson)

As we saw, hyenas today live in hot environments, but in the past they survived during different climates. Was the same true for hippos; were they happy in a cold Britain?

The answer appears to be no. These are big animals, which spend most of their time in water. If the water temperature is too cold, they cant survive. Other fossils found alongside the hippo remains point to a warm climate too. At Trafalgar Square, microscopic fossilised pollen indicates regional temperate environments, including fruit of the water chestnut (Trapa natans), southern European maple (Acer monspessulanum) and fruit of the cocklebur (Xanthium sp.). The ground beetle Oodes gracilis has also been found alongside the great river horse fossils; today these beetles live in the warm climates of central and southern Europe.

Hippopotamus are one of the more special Twilight Beasts. They were able to live in Britain during a short, particularly warm interglacial period. Using Uranium series age determinations on stalagmites in cave sites containing hippo fossils, this interglacial period dates to around 120,000 years ago. This period was hotter than today, allowing warm, lush rivers and lakes, typical of a scene you may see in Africa today.

Hippopotamus only made it to Britain during this particularly warm intergalcial period (known as Stage 5e). The number of sites with fossils (around 90) shows that these large animals were very successful. Towards the end of the interglacial, around 90,000 years ago, the climate cooled, ice caps grew, and an environment with less grasses and colder waters was just too severe for the British hippos. The magnificent river horse still lives on today providing a glimpse into the last warm interglacial of the British Isles.

Written by Jan Freedman (@JanFreedman)

Art by Tabitha Paterson (@TabithaPaterson)

Further reading:

Buckland, W. (1822), ‘Account of an Assemblage of Fossil Teeth and Bones of Elephant, Rhinoceros, Hippopotamus, Bear, Tiger, and Hyaena, and Sixteen other Animals; Discovered in a Cave at Kirkdale, Yorkshire, in the Year 1921: With a Comparative View of Five Similar Caverns in Various Parts of England and Others on the Continent’, Philosophical Transactions of the Royal Society of London. 112. pp. 171-236.

Currant, C. & Jacobi, R. (2001), ‘A formal mammalian biostratgraphy for the Late Pleistocene of Britain’, Quaternary Science Reviews. 20, pp, 1707-16. [Full article]

Franks, J. W. (1959), ‘Interglacial deposits at Trafalgar Square, London’, The New Phytologist. 59 (2). pp 145-152. [Full article]

Kurten, B, (1968), ‘Pleistocene Mammals of Europe‘, The World Naturalist. [Book]

Stuart, A. J. (1982), ‘Pleistocene vertebrates in the British Isles‘, Longman: London and New York. [Book]

Stuart, A. J. (1991), ‘Mammalian extinctions in the Late Pleistocene of Northern Eurasia and North America‘, Biological Review. 66. pp. 453-562. [Abstract only]

Sutcliffe, A. J. (1985), ‘On the track of Ice Age mammals‘, British Museum (Natural History). [Book]

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