Temperature is a limiting factor for polar bears because they are adapted to very cold conditions, so when it gets too warm they overheat easily and lose access to the sea ice they need for hunting and survival.

Quick Scoop

1. Built for the cold

Polar bears are highly specialized Arctic animals with thick fur and a large layer of body fat that trap heat very efficiently. These adaptations work brilliantly in freezing temperatures but make it hard for the bears to cool down when the environment warms up, even just to around 10–20 °C.

2. Overheating and stress

Because they hold heat so well, polar bears can overheat during normal activities like walking, hunting, or running when the air is relatively warm. Studies show that higher ambient temperatures are linked to increased stress hormone (cortisol) levels in polar bears, which signals that warmer conditions are pushing them beyond their comfort zone.

3. Temperature and sea ice

Rising temperatures in the Arctic are melting sea ice earlier in spring and forming it later in autumn, shrinking the time polar bears can hunt seals on the ice. With less time on the ice, they have fewer hunting opportunities, so they lose body condition, struggle to reproduce successfully, and face higher chances of starvation.

4. Why this “limits” the population

In ecology, a limiting factor is something that restricts the size or growth of a population. For polar bears, temperature limits them because:

  • If it is too warm, they overheat and experience physiological stress.
  • Warmer temperatures remove the sea ice platform they depend on to catch prey.
  • Less food and more stress mean fewer healthy cubs survive and adults may die earlier.

So, temperature sets the boundaries of where polar bears can live, how well they can hunt, and how large their populations can be.