Prehistoric teeth unlock clues to mammoth diets

A team examined the teeth of proboscideans, the group of mammals that consists of elephants and their extinct relatives, including mammoths and mastodons. The animals studied lived in Britain during the Pleistocene Epoch, 2.6 million to 11,700 years ago.

In a new study, published in the Journal of Quaternary Science, the researchers found that many of these prehistoric animals were able to vary their diets to avoid competing for the same food sources.

Ancient mammals

The researchers looked at fossils from the mastodon, gomphothere, early mammoth, southern mammoth, straight-tusked elephant, steppe mammoth and woolly mammoth.

These species were the largest land mammals living in Europe during the Pleistocene.

In Britain they lived in a variety of habitats, from open woods to grasslands, and often co-existed.

Prof Adrian Lister, a Museum palaeobiologist and co-author of the study, was part of the team that investigated how much of the grasses and shrubs the different herbivores ate. Fossilised teeth were examined from the Museum collections and from Norwich Castle Museum.

Grazers and browsers

It is possible to see how much rough-textured plant material each animal ate by looking at how their molar teeth got worn down.

The animals were either grazers (eating mostly grass), mixed feeders, or browsers (eating mostly shrubs and trees). Grasses cause more abrasion than trees because they contain high levels of fibre.

Juha Saarinen, a Museum PhD student and co-author of the paper, says, 'We used an angle-meter to measure the depth of the worn ridges in the teeth.

'Soft plants - such as leaves of trees, shrubs and herbs - don't affect the tooth's hard enamel, but they do wear down the softer structure between the enamel more quickly.

'This results in deep valleys in the teeth and sharp angles on the meter.

'Grass wears down the entire tooth, leading to shallower valleys and blunter wear angles.'

Getting enough to eat

The team also used existing pollen data to analyse the plants that would have been growing at each site where the teeth were found.

This allowed the researchers to examine how different species of mammoth or elephant could co-exist and get enough to eat.

Lister explains, 'If the vegetation was mixed trees and grass, like a savannah, and one species was eating mostly grass and the other mostly trees, we can see that they were dividing that environment between them.

'Sometimes we see that a species was eating something quite rare in the environment, so its diet became specialised.'

It's not just fibre in grass that wears down teeth. Wear also happens when animals feed in an open environment or close to the ground, because they tend to pick up more grit with their food.

Lister says, 'There was some question as to whether shallower valleys in the teeth were really due to grass, or just to feeding close to the ground in the open - an environment that could include other low-growing flowering plants or ferns.

'After comparing the tooth wear data with the pollen data, we are pretty confident that the flat teeth do indicate a diet high in grasses, whatever environment the animals were feeding in.'

Splitting meals

The results show that the diets of the herbivores were flexible. The animals that were usually browsers were able to eat and digest more grass when it became available.

Lister's team also found there was a lot of variation between individuals in each species, pointing to a range of dietary choices, or seasonal variations in their diet. 

For example, the teeth of straight-tusked elephants were on average still sharp, suggesting they ate more shrubs than grasses. But teeth from this species found in Ilford show different types of wear, meaning specific populations of straight-tusked elephants could have had a more varied diet.

When several different species lived alongside each other, the differences in the teeth were very large, suggesting the animals created separate diets for themselves, avoiding competition for the same grasses.