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Why Are Polar Bears Green in Zoos?

Why are polar bears green in zoos?

Have you ever visited a zoo and seen a green polar bear? It’s a strange sight since polar bears are normally white. In this post, we’ll explore why some polar bears turn green in captivity, if there are green bears in the wild, whether they can turn white again, and what colour polar bears should be.

Why Are Polar Bears Green in Zoos?

When you go to the zoo and see a green polar bear, it’s likely staining from algae in the bear’s water or habitat. Here’s why this green colouring happens:

Algae Growth in Water

Polar bears spend lots of time in water. In the wild, the ocean or ice water they swim in is cold and fast-moving, which prevents much algae growth. But in zoo habitats, the water is warmer and stagnant, allowing algae to thrive. The algae isn’t harmful but can turn the bears’ white fur green.

Algae in Concrete Habitats

Concrete surfaces in zoo enclosures also provide the perfect place for algae to grow. As bears walk or lay on algae-covered rocks and walls, the green colour transfers to their fur. Their swimming then spreads it around their bodies.

Lack of Camouflage Need

In the wild, polar bears need white fur to blend into the snow and ice. But in zoos, they don’t need camouflage, so the algae discolouration doesn’t impact their survival. Keepers don’t rush to clean it off, so some bears stay green.

Dietary Changes

A zoo bear’s diet likely contains less fat and more fruits, veggies, and grains than wild polar diets. This can affect the oils in their fur, making it more prone to algal staining.

Are There Green Polar Bears in the Wild?

Given the right conditions, seeing a green polar bear in the Arctic wild is possible but extremely rare. Here’s why:

Cold, Flowing Waters

The cold oceans and waters of the Arctic prevent much algae growth, so there is minimal green discolouration for wild polar bears swimming. Flowing currents also limit algae accumulation.

Snowy, Changing Habitats

The snowy arctic terrain provides no concrete for algae to grow on. Polar bears also always move across the vast landscape, not staying in one algae-prone place.

Need for Camouflage

Wild polar bears must stay white and hidden to hunt seals successfully. Green colour could negatively impact their survival, so the bears keep their fur clean of discolouration.

High-fat Diets

Wild bears eat a diet high in seal blubber and fatty fish, which provides oils that likely protect their fur from staining.

While possible, these factors make it extremely unlikely you’d see a green bear naturally in the Arctic wild. But in zoo habitats, the conditions are very different, allowing algae to create the strange green bears we sometimes see.

Can Green Polar Bears Turn White Again?

Many wonder if a green polar bear can return to its normal white colour once stained by algae. The good news is, yes, they can turn white again with a bit of help! Here’s how:

Bathing and Grooming

Zookeepers use baths, hoses, brushes, and scrubbing to remove the algal stains from green bears’ fur manually. This returns the polar bear’s coat to its typical white appearance.

New Fur Growth

During warm months, bears shed their undercoat. The new fur grows clean and white, helping remove any green discolouration. Eating a natural diet also assists new fur growth.

So, while green polar bears might look strange to us, they can regain their bright white coats through bathing, grooming and new growth!

What Colour Should a Polar Bear Be?

We’re used to seeing pictures of polar bears as bright white, so what is their natural colour really supposed to be?

Bright White fur

A healthy polar bear should have fur that appears “optic white” – a very clean, bright white with no yellowish or brownish tones. This provides the best camouflage in snow and ice.

Dark skin and nose

While fur is white, a polar bear’s skin underneath is black. This absorbs heat from the sun. Their noses are also black. The black skin and nose show through the translucent hollow fur strands.

No true “black” bears

There are no truly “black” polar bears. Cubs are born a more ivory white, and some look darker yellow-white when dirty or wet. But the blackish colour means the bear is unhealthy.

White stays year-round

Polar bears stay white all year, even during summer when snow melts. The white coat helps reflect heat during warmer months.

So remember, a healthy polar bear should always appear bright white, with black skin peeking through the hollow fur. Any other colour likely indicates dirtiness, algal growth, or health issues.

What Colours Can a Polar Bear Be?

While white is standard, polar bears can display other temporary colourations:


Bears appear more yellow-white when shedding fur or dirty from mud. Normal white is restored after the annual moult or cleaning.


Algal staining leads to green fur in zoo bears, who return to white with cleaning. Very rarely, a wild bear might get some green if swimming in an algae-full pond.


Wild bears can look brown if splashing in mud. But full brown would be very unnatural and unhealthy.


Eating foods like carrots in captivity can temporarily tint fur oranges. This goes away as food digests.

So, while polar bears are meant to be bright white, you may see slight variations in zoos or the wild. But a strong colour means an unhealthy or stained bear needs care. Proper diet and grooming maintain the species’ iconic white camouflage.