Every Christmas Eve, Santa and his reindeer deliver gifts to children around the world in just one night. At least, that’s according to folklore. If you ask biologists studying the Arctic, they’ll tell you a very different story. Instead of dashing through the snow, reindeer focus on conserving energy and surviving in one of the world’s harshest environments.

Reindeer or caribou (Rangifer tarandus) are a species of deer native to the Arctic and tundra areas of Northern Europe, Siberia, and North America. Unlike most mammals, they undertake some of the longest migrations on Earth, covering up to 5,000 kilometers annually in search of food and favorable conditions. However, not all reindeer are migratory — some are sedentary.

Regardless of whether they’re migratory or not, once winter starts, their activity slows down significantly. Snow, far from creating a winter wonderland, becomes a threatening obstacle. It covers their primary food sources — lichens, mosses, and fungi—making each meal a laborious task.

“They avoid energy-sapping activities, especially when the snow is closed. This is shown by studies collected in the “Arctic Animal Movement Archive” on the Movebank platform at the Max Planck Institute for Behavioral Biology in Konstanz,” writes researchers from the Max Planck Institute of Animal Behavior Konstanz.

Behavioral studies, such as those gathered in the Arctic Animal Movement Archive (AAMA) at the Max Planck Institute for Behavioral Biology, reveal that reindeer avoid energy-intensive activities when snow conditions are unfavorable. This strategy is essential for surviving the cold season, when food is scarce and temperatures plummet.

A very important migration

Reindeer migrations are a spectacular event. Experienced adults lead younger animals along well-established routes, passing down critical survival knowledge and guiding the group. These migrations often occur in massive herds, with individuals traveling in single file to navigate their environment efficiently.

Research from the AAMA shows that reindeer rely on social cues during migration, orienting themselves by observing the movements of key individuals within their group. Their specialized hooves are built for digging through snow to access lichens, mosses, and fungi, while their dense, insulating fur and the ability to slow their metabolism help them conserve energy in freezing temperatures. As long as snow doesn’t blanket everything, they can complete their migration.

This migration is important for the entire ecosystem, not just for the reindeer themselves.

As reindeer travel, their grazing and trampling affect vegetation patterns and nutrient cycles, shaping the Arctic landscape. They act as ecosystem engineers, leaving a changed landscape behind them. Yet climate fluctuations and human interference are altering this delicate process.

Reindeer are in trouble

Rising temperatures and shifting precipitation patterns are changing the timing of seasonal events, such as calving. In northern Canada, studies show that reindeer herds are giving birth earlier in the spring, likely in response to warming trends. Southern herds, in contrast, have not shown the same shifts, highlighting the complex and localized impacts of climate change.

Habitat destruction from resource extraction, such as oil drilling and dam construction, disrupts migration routes and grazing areas. For example, Iceland’s Kárahnjúkar dam has significantly altered local ecosystems, forcing reindeer to adapt to reduced access to pastures.

Overall, the number of reindeer has decreased to less than half their original number over the past 20 years, but the impact is not uniform across different herds.

That’s why it’s so important to track their movement — and this is what the Arctic Animal Movement Archive aims to do. Researchers from over a hundred universities, government agencies, conservation groups, and indiginous groups in 17 countries are involved. “To detect changes in the behavior and habitat of animals in the Arctic, we need to work together to gain insights across decades and populations,” says Sarah Davidson, a data curator at the Max Planck Institute of Animal Behavior who leads the NASA-funded global data archive.

Assisting the Arctic

The archive isn’t only about reindeer. It already contains nearly 300 research projects with movement data of more than 15,000 marine and terrestrial animals from 1991 to the present.

“The Arctic Animal Movement Archive is a prime example of global ecological collaboration: at the moment, researchers at the Max Planck Institute are working on global consortia for animal observations in drylands, southern Africa and the Galapagos,” says Martin Wikelski, director at the Max Planck Institute of Animal Behavior.

So, although reindeer are not busy pulling sleighs in the real world, their very lives during the Christmas season are a testament to resilience and adaptability. Their ability to navigate vast migrations, conserve energy, and survive extreme conditions offers lessons in perseverance. As you celebrate this holiday season, spare a thought for the reindeer that inspire so many traditions. Beyond their mythical role, they play a vital part in the Arctic’s intricate web of life. These beautiful creatures are a reminder of nature’s wonders and the importance of preserving them.