Koalas are iconic Australian marsupials. They are often called bears, even though they belong to a different family. Nevertheless, because of their nickname, many people believe that koalas hibernate in winter. But do they?
Do Koalas Hibernate?
Koalas do not hibernate. These arboreal marsupials spend most of their lives in trees and don’t have burrows or dens. They sleep in the forks or on the branches of eucalyptus trees during the day and become active at dusk. In the colder months, koalas adopt a hunched sleeping position that protects them from rain, snow, and cold winds.
Koalas live in eastern Australia, their range stretching from northern Queensland to southwestern Victoria.
This area has a mild climate all year round. Summertime temperatures average around 80°F in Queensland and are slightly lower in Victoria. In winter, the temperatures drop to around 60°F in Queensland and 50°F in Victoria. However, they rarely drop below freezing level, and snowfall in these areas is rare.
Not only is the weather mild all year round, but koalas seem to prefer cooler temperatures.
These marsupials spend most of their time in trees, eating or sleeping. Regardless of the season, koalas sleep for about 18 to 20 hours per day. The remaining hours are dedicated to foraging, except for the breeding season when they also spend time mating.
Koalas’ breeding season starts in late winter (August) and peaks in spring. Gestation lasts for about 34 to 36 days, with most koala offspring (joeys) being born in summer, generally between November and December.
Young koalas stay with their mothers for up to 36 months. When they are old enough, juvenile koalas disperse in late fall or early winter, before the start of the breeding season.
Do Koalas Migrate?
Koalas do not migrate. The climate in areas where koalas live is mild. Moreover, they are territorial animals that only leave their home ranges as juveniles during dispersion.
Koalas are solitary animals that are only seen together during the breeding season or if they are in a parental relationship (mother and joey). Male and female koalas establish overlapping home ranges consisting of home and food trees.
The home range size varies depending on food availability and individual dominance, including gender and age. In the wild, most females have home ranges of about 2.5 acres. Male koalas’ home ranges are larger, up to 3.7 acres or more, and overlap with the territories of several females.
Sometimes, a dominant male’s territory may also overlap with the territory of juvenile, non-breeding males.
By overlapping their home ranges, koalas can breed without either of them getting too far away from their preferred home trees.
Koalas are polygamous, and a single male will breed with several females throughout the breeding season. Copulation is very quick and after impregnating one female, the dominant male moves to the next. However, the pair don’t spend time together except for copulation.
An exception is koalas living in urban environments. Due to a loss of habitat, koalas living in urban areas may live in loose-knit groups. However, even if they share a territory, it is rare to see two koalas in the same tree, unless they are mother and joey.
Koala Dispersion Patterns
Joeys are born underdeveloped and live in their mothers’ pouches for about six months after birth. When they become too big for the pouch, they will crawl onto their mothers’ backs, where they will spend another six months.
At about 12 months, koala joeys start to become independent. However, they will still stay with their mothers for another few months.
Juvenile koalas disperse when they are about two years old, although some may leave their natal home range earlier or stay longer with their mothers.
Young female koalas generally establish their own home ranges close to their mothers’ territories. Young males travel farther away, establishing new home ranges as far as six miles from their natal home range.
Some young males can’t find a suitable territory and they remain nomadic. In this case, they will keep traveling, sometimes crossing the territories of other koalas. Nomadic koalas may or may not find willing mates during the breeding season. If they find a suitable territory, nomadic koalas will eventually establish their own home ranges.
Where Do Koalas Go In The Winter?
Koalas don’t go anywhere in winter. Once a koala establishes a home range, they travel very little and only to move from one tree to another or for breeding purposes.
These marsupials spend most of their time on trees. They do not nest and are anatomically adapted to an arboreal lifestyle. When they are not eating or breeding, koalas spend their time sleeping. There are various theories as to why koalas sleep 18 or more hours a day, but this behavior is most likely linked to their nutrient-poor diet.
In fact, koalas only eat eucalyptus tree leaves. Not all eucalyptus species constitute a food source for these picky marsupials. Koalas will only feed on about 50 of over 700 eucalyptus species, and they generally only eat the leaves near the top of the tree, which contain more water.
The other trees in a koala’s home range represent the home trees the koala uses for sleeping.
As nocturnal animals, koalas are often spotted snoozing on a branch or tree fork during the day. They are most active at dusk or dawn but also throughout the night.
How Do Koalas Survive In The Winter?
Koalas live in mild climate areas and have no real need to hibernate or migrate in winter. However, the temperatures vary wildly from summer to winter. So, how do they stay warm in colder weather?
Koalas have bodies that are perfectly engineered to withstand all kinds of extreme weather. Their fur is incredibly thick and impermeable. During cold winters, this thick coat keeps koalas warm and cozy on their home tree branches. In summer, the thick coat helps deflect heat and regulate the body temperature.
Koalas don’t slow down their metabolism in winter and don’t build up fat deposits in fall – this would be challenging, considering the limited and nutrient-deprived diet these marsupials have.
However, their coat has three layers on the back and two on the front. This extra-thick fur compensates for the lack of fat and already slow metabolism.
A difference in size between koalas living in southern parts of Australia compared to those in the north is also linked to the animal’s ability to survive winter. Southern koalas are larger and have thicker fur so that they can survive the harsher southern winters.
Changed Sleeping Patterns
Koalas spend most of their time sleeping regardless of the temperature. However, their sleeping posture changes with the season.
In summer, koalas are often seen sleeping either on their backs with their bellies exposed or hugged to a branch. Branch hugging is a mechanism koalas use to cool down their own temperature on extremely hot days.
In winter, they adopt a hunched sleeping position with their head bent towards the chest. Often, koalas will sleep with their fronts facing the tree trunk. This leaves their back exposed.
As explained above, koalas have three layers of fur on their backs. By leaving only the backs exposed and curling up, they manage to minimize heat loss and stay dry when it’s raining. Snow is rare in koalas’ habitat, but if it happens, the thick coats and hunched sleeping position enables them to survive the cold temperatures.
Koalas are adorable marsupials that spend the majority of their lives sleeping and munching on eucalyptus leaves. They live in mild climate areas and rarely have to bother about too cold weather. In fact, it is more likely that they will suffer extreme heat in summer rather than too cold winters. Nevertheless, the thick fur and winter sleeping posture enable koalas to survive even the coldest Australian winters.