Emily Wiesendanger, The Late Pleistocene Reindeer (Rangifer tarandus) of Britain and Western Europe: Past Migrations, Seasonality and Palaeodiet, supervised by Prof. Danielle Schreve (RHUL) and Prof. Ian Candy (RHUL)
‘Let me see. (takes the skull) Alas, poor Rudolph, I knew him.’
Oh dear, she’s talking to the skulls again.
No wonder. I was in a shed full of skulls just inside the Arctic Circle. This was like an IKEA for the Palaeontologist, with the skulls and skeletons of Swedish reindeer from the 1950s neatly stacked in boxes and hung on racks. The reason for travelling to Swedish Lapland and this amazing collection, part of the Ájtte Museum in Jokkmokk, was not to eat delicious meatballs (although I did), but to provide comparisons for measurements of fossil reindeer.
Today, the only British reindeer herd was introduced to the Cairngorms in the eastern Highlands of Scotland during the 1950s. However, throughout the Late Pleistocene (126,000-11,700 years ago), reindeer roamed freely in large herds across Britain and most of western Europe. This means that where reindeer are found in the fossil record, we can tell that the climate and environment were once much more similar to the Arctic and Subarctic habitats of reindeer today.
Working hard in the collections of the Ájtte Museum, Jokkmokk, Sweden.
But rather than simply recording this presence or absence in the fossil record, my PhD looks more closely at the evidence provided by the individual bones, teeth and antlers of reindeer. These can be used to reconstruct patterns of seasonal movement. Now reindeer are bi-annual migrators, meaning they generally move between summer grazing pastures in the north and winter grazing pastures in the south. Reconstructions of past migrations can therefore be used to learn more about the impacts of climatic, environmental and human derived changes on reindeer ecology.
This is particularly important given the current threats to this species. As Arctic winters become warmer and wetter, the formation of thick ice layers over short growing vegetation have been linked to recent mass starvations in reindeer populations, as well as a reduction in body size to near critical levels. What’s more, the continual expansion of roads, railways and industry in the Arctic are not only limiting the migration routes of reindeer, but are directly responsible for their deaths. Looking at how past populations have responded to especially climatic changes, will help with the planning of future conservation efforts to protect this vulnerable species.
So, my research mainly compares the seasonal movements of Late Pleistocene reindeer from fossil sites in Britain and western Europe. This is possible due to the fact that reindeer only come together in large herds at certain times of year. Each herd, or aggregation, is composed of different ages and sexes depending on whether it is the summer or winter grazing, spring calving or autumn breeding season. Calving, which always occurs in May, acts as a tie-point, so that the ageing and sexing of reindeer fossils can tell us what time of year reindeer were present at each fossil site.
For me, this means scouring the drawers and cupboards, basements and attics, of museums large and small, in search of the bones, teeth and antlers of fossil reindeer to study.
One of the most precise ways to age reindeer combines the timing of permanent tooth eruption with patterns of attritional wear. As reindeer age, the lighter enamel covering of a tooth’s biting surface is worn away in distinct patterns, to reveal the darker dentine below. In calves, this can age individuals to an exact month, informing us of not only the ages present in the aggregation, but using a May birth date, the season.
Season can also be determined directly from reindeer antlers. Reindeer are the only deer species in which both males and females have antlers. These are grown and shed during different months of the year depending on the sex. If you can identify whether a fossil antler is male or female, shed or unshed, you can also tell the season of death. This antler cycle is how we know that Rudolph and his antlered friends are actually all females. By the 24th December, males have already shed their antlers, but females will keep them until the spring.
Being able to tell males and females apart in the fossil record is also useful because the ratio of sexes present in an aggregation varies with season. Looking at the size of male antlers, it is unsurprising that they aren’t the only element where sexual dimorphism is visible. Measurements of the breadth and depth of bones from the forelimb and hindlimb can be used to calculate estimates of body mass, distinguishing between the larger/heavier males and smaller/lighter females.
This is also why collections from Scandinavia and North America, like those at the Ájtte Museum, are so important. Studying historical reindeer provides a comparison for past populations. However, given the changing vulnerability of reindeer, recognising more recent changes in body size and diet over the last 100 years are just as vital.
And so, that’s how I found myself in a shed, in the Arctic Circle, talking to yet another skull.