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Sabre tooths in Spain

Sabre tooths in Spain | Homotherium: a lion among sabre tooths | Resources

Sabre tooths in Spain

'Death mounds' mystery
In the foothills of the Spanish Pyrenees, the Big Monster Dig team was put on the trail of a very unusual puzzle: mounds of mud in a disused limestone quarry that were full of bones. To add to the mystery, most of the bones were from big, sabre tooth cats. What were these mounds and why had the remains of so many predators come to be in the same place?

The team was called in by a local tour guide, who wanted to know more about these so-called 'death mounds'. They joined up with expert palaeontologist Angel Giloberts and colleagues from the University of Barcelona, who had been working on them for several years.

The limestones here are very soft and, in geological terms, very young – a mere two million years old. These limestones are also rather unusual in other respects. The majority of limestones, especially in the UK, were deposited in tropical seas as reefs or in shallow water just behind them. These, however, were deposited in temperate lakes very similar to the modern day Lake Banyoles, just 30 kilometres from our dig site.

High life
Dave Martill and Sarah Gabbott got straight into the search and the diggers turned up a jawbone almost immediately. It was exciting to find something that good so early in the dig, but the rest of the day went less well. Despite some very hard searching, they found only one very small fossil snail shell.

John Howell, meanwhile, had opted for the high life and went for a trip in a hot air balloon. He justified it to the others on the grounds of the importance of getting a good overview of what was going on regionally.

How the mounds formed
In fact, the balloon trip turned out to be even more important than John had imagined. As well as getting his overview of the regional geology (and seeing the high Pyrenees), John also spotted a couple of round ponds of about the same dimensions as the mud mounds. Maybe the answer to the mystery lay with the round ponds?

The ponds were small features about 20 metres in diameter but very steep-sided and deep. They were also extremely smelly with a strong whiff of rotten eggs. A bit of 'bucket chemistry' revealed that the water was fairly acidic (hence no snail shells); and some local information confirmed that the ponds were fed by underground streams and that they had appeared very quickly, often overnight.

With this information, the team was able to propose a model for how the mounds had formed. Water flowing through subterranean rivers had dissolved the limestone, creating caves, collapses and eventually sink holes or 'dolines'. These round holes in the ground flooded to become ponds, which had slowly filled up with sediment. Once the limestone was quarried, the circular piles of mud left behind created the mounds.

Why so many carnivores?
So far so good, but why so many carnivores? A number of theories evolved. One suggestion was that their remains were washed into the holes. Another was that the dolines had been dens occupied by the carnivores. And yet another was that the animals had been trapped within the holes and died, perhaps after being attracted by the smell of rotting meat from other trapped animals.

In an attempt to solve the mystery, the team decided to look at the distribution of the bones that had been found; the presence (or absence) of the remains of young; and any evidence that the bones had been transported by floods.

Dave and John examined the 3D computer maps that had been made by the Spanish researchers as they extracted the bones. These showed that the bones were concentrated around the edge, implying that either the animals were washed in or had made their way to the sides while trying to escape. These detailed maps show the importance of recording the position of all finds. While the data may not seem important at the time, and there is often a desire to get finds out as quickly as possible, it is always worth getting an expert to help document discoveries properly.

Zoo trip
After this, Dave went off to Barcelona Zoo to talk with animal artist Mauricio Anton, who has done some fantastic reconstructions of what the sabre-toothed Homotherium looked like. Dave claimed that he was interested in making comparisons between the bones from the mounds and modern big cats. He said that he was trying to determine whether they lived in packs (like lions) or as solitary animals like tigers. He reckoned it was important to understanding how they may have died. It also made up for him not getting invited on the balloon trip.

Meanwhile, Sarah went to the museum to look at some of the other bones that the Spanish team had found. She quickly determined that there were very few young ones, so it probably wasn't a den. Nor was there much evidence for transportation by floods or trampling. The trap theory was starting to look good.

The explanation
In fact, the explanation for the number of sabre tooth bones is probably a mixture of the different theories. On her way back from the museum, Sarah stopped off at some nearby caves. While these caves were formed in a slightly different way, it was easy to see that the dolines could have been dens when the water table was low, traps when it was higher, and that material could have been washed in at any time. All of the theories were probably correct at different times and with different degrees of frequency.

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