Just as humans have historically gathered during winter, many animals do the same. Animals may not be exchanging presents or decorating their nests and dens but a lot of species become more social in winter – even ones that are normally solitary. Animals have more to worry about this time of year than bickering relatives or the last date for Christmas post. Winter poses severe challenges for wildlife, from freezing temperatures to a scarcity of food. One of the main reasons animals aggregate during the winter is to keep warm. Some species avoid these harsh conditions by migrating to warmer areas, such as cuckoos in the UK overwintering in central Africa. Others grow insulating coats (like mountain hares in the Scottish highlands), or develop a thick layer of blubber (grey seals and harbour porpoises for example) to keep the cold at bay. But some animals come together instead. Brandt’s voles inhabit the grasslands and steppe of inner Mongolian, where winter temperatures drop as low as -30 °C and strong winds and blizzards are frequent. Brandt’s vole is surprisingly tough. Danita Delimont/Shutterstock During the summer months, the voles are largely solitary. However, throughout thelong, harsh winters, they form small huddling groups of around four in the nesting chambers of their underground burrows to share body heat. Huddling conserves energy by reducing resting metabolic rate by up to 37% and limits heat loss.Safety in numbersArctic hares live in one of the harshest environments on Earth in northern Canadawhere the long winters last up to nine months and temperatures can drop to -40°C.During this time, they abandon their solitary summer habits and form large aggregations of up to a hundred hares. The purpose of this behaviour is not for thermoregulation, since they do not come into close contact. Rather, it is for safety against predators. When Arctic hares form winter groups, they are increasing vigilance against predators including Arctic foxes and wolves. Arctic hares have to stay alert for foxes and wolves. Nick Dale Photo/Shutterstock A major advantage for prey species living in a group is that each animal can spend less time on the lookout for predators (and more time feeding). This is crucial for Arctic hares in winter when food is scarce and they need more energy to keep warm.Larger groups also cause predator confusion, making it harder for predators to target individual animals. The group dilution effect means that in the event of an attack each hare’s chance of being caught is reduced. Information networkRooks are highly social birds living in small flocks of typically ten or fewer unrelated birds all year round. During the winter months many small flocks will join up to form huge colonies of hundreds or thousands of birds from the surrounding area. Buckenham Carrs woodland in Norfolk has the largest rookery in Britain where an estimated 50,000 rooks have been gathering every winter for centuries. Each evening birds travel to the roost from across the Norfolk Broads, sometimes up to 20 miles, when the bare trees become foliated with rooks.During the day, the rooks go off in smaller foraging groups and then return to the roosts each evening. Roosting closely together not only helps reduce heat-loss but also makes it easier to find food. These large communal roosts also function as information exchange centres about where the best places to forage are. When rooks leave their roosts in the morning, they pay close attention to inadvertent cues given by other rooks such as their body condition (as an indicator of recent foraging success) and the direction in which they fly. Less successful rooks copy their more prosperous roost mates. Group foraging is more efficient and therefore reduces exposure to danger.Water conservationAnother example of the benefits of winter groups is water conservation. Ladybirdsenter a physiological dormancy, called diapause, which allows them to survive thewinter months without feeding. During this period, they form clusters of hundreds or even thousands of ladybirds, which helps conserve energy, as clustered individuals have lower metabolic rates. Moreover, these aggregations create a microclimate with more stable temperatures and higher humidity, which helps reduce the risk of desiccation, as ladybirds do not consume water during overwintering. Ladybirds tough out winter together. A. Saunders/Shutterstock In addition, ladybirds gain extra protection when they form large clusters because their warning colouration, advertising their toxicity, is more obvious to predators. In the UK, native seven-spot ladybirds aggregate under tree bark or leaf litter, whereas the non-native harlequin ladybird prefers houses and pack together in huge numbers around windows and in lofts during the winter. Record warm temperatures for both spring and summer in the UK during 2025 may have led to a surge in insect populations. This may explain why many people have noticed large clusters of ladybirds around windows in their homes.If you find a cluster of ladybirds in your home, it is best just to leave them alone as they pose no risk to people or wooden surfaces. Plus, long term data indicates insect populations are dwindling.Reproductive advantageIn the cold prairies of Manitoba (Canada), red sided garter snakes congregate incommunal, overwintering dens, sometimes by the thousand. Snakes rely on existing underground structures such as the abandoned burrows of chipmunks, disused wells or limestone sink holes to overwinter. These snakes detect and follow the pheromone trails left by other snakes, which leads them directly to the communal dens.This seasonal assembly not only increases survival rate during the winter months but also facilitates mating success come the spring. The close proximity of males and females after emergence reduces the time spent searching for a mate during theshort northern breeding season. Courtship begins immediately upon emergence from the dens. Multiple males coil around single females in a “mating ball” ensuring the chances of mating before the females disperse. Red sided garter snakes form mating balls in the spring. Mark F Lotterhand/Shutterstock This seasonal social behaviour are adaptations for survival in harsh conditions. Similar to many animal species, early humans likely congregated during severe winters to share warmth and resources, illustrating a shared strategy for survival in challenging environments. Understanding this behaviour is vital as climate change alters winter severity and availability of food and shelter.Anna Champneys does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.