Unlike the reindeer on Norway's Svalbard archipelago, Svalbard reindeer conserve their energy by moving as little as possible. And since they have no predators chasing them, they tend to stay in an area throughout a year, nibbling on the herbs, tiny grasses, and sledges they can find.
During the time of snow, it is typical of them to keep nibbling on their food after pawing away the snow. For thousands of years, Svalbard reindeer have survived with this lifestyle, evolving into a different subspecies and giving them the concession of adapting physiologically.
However, there has been less snow in some winters and more rain due to the warming climate. This situation is an event of rain-on-snow (ROS) which causes the ice to form on the ground. This case is a severe catastrophe for reindeer since the ice coats on their favored food, leading to starvation.
Researcher Brage Bremset and his colleagues from Centre for Biodiversity Dynamics (CBD), Norwegian University of Science and Technology published a study in Nature Communication, modeling the effects on the population dynamics of reindeer if the icing becomes an extreme event and not the norm.
The researchers claimed that some unusual events of icing had revealed the cause of population crashes. They further posited that more population crashes would be an intuitive expectation if the warming continues.
Bremset and his colleagues relied on the data collected every year on reindeer since 1994 by the Norwegian University of Life Science, the Norwegian Institute for Nature Research, and also James Hutton Institute.
Exploring this information along with the IPM, Integrated Population Model, a biological model, they came up with a detailed picture of the population of Svalbard reindeer, their annual population rates, reproduction, and survival levels for six female age classes.
To get to the result of what they termed "winter harshness" or an icing proxy, they used historical data on the yearly amount of ROS since 1962. They were also able to detect how ROS affects population dynamics.
And given different future scenarios of ROS, and with the tools they used, the researchers concluded on their projection of how the population of reindeer they studied would change.
After running their models, the researchers discovered that the population of reindeer has a counterintuitive behavior under a harsher future condition, that is when the ROS frequently increased.
They also affirmed that without the novel population models that reveal the nuances of the likely consequences of continuing climate change, their future prediction of population dynamics of this charismatic animal would be very likely wrong.
