It’s a common fact about polar bears that they live for a relatively long time by animal standards, although still far shorter than humans. So, what is the average lifespan of a polar bear?
Polar bears can live up to 30 years in the wild, however, few make it past age 15 due to high pup mortality, malnourishment, drowning, disease, and human impacts. They live for much longer in captivity where the oldest known polar bear reached an age of 41 years old at a Canadian zoo.
In the rest of this article, we’ll take a look at the lifespan of polar bears and common causes of death among pups and adults.
How Long Do Polar Bears Live?
The oldest polar bear ever known was Debby, she was born in the Arctic islands of Russia but spent most of her life at a Canadian Zoo. Debby lived to be 41 years old and holds a place in the Guinness World Records4 (source: CBS News).
Common Causes of Death Among Polar Bears
The main causes of death among polar bears are malnourishment, drowning, disease, and being killed by humans. Climate change is not a specific cause of death but contributes to all of these and is having a long-term impact on polar bear populations.
Here is a breakdown of each cause:
A National Geographic video of a starving polar bear has bought the issue of polar bear malnourishment into the limelight.
Polar bears are carnivorous and rely largely on a diet of seals and other marine mammals which they catch from the sea ice5 (source: Polar Biology, M.P. Galicia, et al, Vol. 38, Iss. 12, 2015). They will often wait by breathing holes for seals to appear or catch them in the water.
Polar bears must build up large fatty reserves during winter to prepare for the summer months when the sea ice melts and they can no longer catch their main prey.
However, due to global warming, the sea ice is melting earlier each year which gives polar bears less time to build up their fat stores. This can cause them to become malnourished and starve towards the end of summer.
Malnourished polar bears may be nutritionally stressed which can impact both their reproductive success and survival6 (source: Science of The Total Environment, K.A. Patykm et al, Vol 514, 2015).
Malnourishment is most likely to impact polar bears at the adolescent (sub-adult) stage of their lifecycle. They have just left their mothers but still haven’t perfected their hunting skills. This is why the majority of attacks on human settlements are malnourished adolescents in search of food7 (source: Wildlife Society Bulletin, J.M. Wilder, Vol 41, Issue 3, 2017), although polar bear attacks on humans are still very rare in any case.
Malnourishment only affects certain sub-populations of polar bear, those that have the largest reliance on the sea ice and limited access to food during the summer months.
Polar bears migrate from the seasonal sea ice to islands or the mainland during summer when the sea ice melts. These journeys can often require several thousand-kilometer stretches of water that must be navigated.
The longest recorded swim by a polar bear was a female who traveled 687km which took more than 9 days8 (source: Canadian Journal of Zoology, A.M. Pagano, et al., Vol 90, No. 5, 2012).
Although polar bears are strong swimmers, fatigue and rough seas can result in drowning. For example, researchers witnessed polar bear carcasses floating 54km offshore, they estimate that up to 27 polar bears drowned during a single storm9 (source: Polar Biology, C. Monnett & J. S. Gleason, Vol 29, 2006).
As with all life, there are many diseases and viruses that cause mortality among polar bears. In some cases, the disease itself will not kill them but will impact their ability to survive.
Some viruses and diseases that have been known to occur in polar bears are:
- Trichinella Parasites – The microscopic parasite Trichinella is very common in polar bears. In humans, Trichinella parasites cause Trichinellosis which can cause facial swelling, heart and breathing problems, and even death.
- Coxiella – This is a bacteria found in polar bears and animals that causes Q-fever, a disease that can cause death among animals. Humans can also catch this although they usually suffer mild flu-like symptoms.
- Morbillivirus – Polar bears have also been reported to have various types of Morbillivirus, which is from the same family of viruses that causes measles and fevers in humans. Examples of Morbilliviruses found in polar bears include Phocine Distemper and Canine Distemper.
- Rabies – There has been a confirmed case of a polar bear with Rabies in Northwest Territories, Canada.
Polar bears have also been reported with Alopecia, Toxoplasma Gondii, and Brucella, although neither of these are likely to cause death.
Scientists predict that as the climate in the Arctic warms and more species move north, they will bring more pathogens with them that could impact polar bears.
4. Killed by Humans
Although most countries have made it illegal to hunt polar bears, there are exceptions for indigenous people in Alaska, Canada, and Greenland who have relied on them for food and income for many centuries. In these countries, around 800 polar bears are killed each year10 (source: Science Progress, Ø. Wiig, et al, Vol 91, No. 2, 2008).
Polar bears may also be shot in other countries when they have attacked humans.
Humans may also indirectly kill polar bears, for example, oil spills can contaminate polar bear food sources and toxic chemicals from industrial activity may have long-term impacts on their health and ultimately their survival11 (source: Sea World).
Pup Mortality Among Polar Bears
Pup mortality varies among different sub-population of polar bear. For example, in Svalbard, Norway it has been reported that only a third survived weaning whereas in Alaska and Canada.
Common causes of death among polar bear pups include starvation, hypothermia, drowning, or cannibalism12 (source: Science Progress, Ø. Wiig, et al, Vol 91, No. 2, 2008).
Adult male polar bears are known to hunt and eat polar bear cubs in late summer and autumn when food is scarce. Typically, female polar bears will not hunt other polar bears13 (source: National Geographic).
Survival rates of cubs decreased as the mother gets older. This is due to declining health and a reduced ability to keep their cubs safe from cannibalism.
The Lifecycle of Polar Bears
Polar bears have 4 main life stages; birth, cubs, subadults, and adults. The earlier years are treacherous with many threats such as those mentioned here.
However, once they make it to adult life (defined as past age 4 here), survival rates are much higher at around 95% per year14 (source: Science Progress, Ø. Wiig, et al, Vol 91, No. 2, 2008).
The age at which polar bears reach sexual maturity varies between regions and even within the same region. Most studies suggest that males reach maturity sometime between ages 5-10 and females between ages 4-6.
See our guide to the lifecycle of polar bears for more information about each stage.
Do Polar Bears Have Predators?
No, adult polar bears do not have any natural predators because they are at the top of the arctic food chain. However, polar bear cubs are at risk of being cannibalism by larger male polar bears and other predators such as arctic wolves.
Although hunting polar bears is largely illegal in most arctic countries, there are some exceptions for Inuits who hunt and eat polar bears within government quotas.