Polar Bears - Data, Pictures and Videos

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Question from Anne-Sophie as well as Aslak & Katja:
I see stories in the media about how climate change and lack of ice won’t be a problem for the polar bears, as they are apparently able to survive on land by eating dolphins, bird eggs, and reindeer – is this really true?

Answer by Dr. Thea Bechshoft:
Good question, all three of you!
Even though (certain sections of) the media like to believe that polar bears would do just fine without sea ice, these stories are unfortunately not true.

Polar bears are curious and opportunistic animals – if something looks new and potentially edible, they will have a closer look and a nibble. This is true for all polar bears, but especially for those that are summering on land (waiting for the ice to re-form) or those that find themselves in areas with few seals: any food is better than no food, even if it contains very little energy. However, none of these food items are a viable option for keeping polar bears alive long-term; only seal fat has a high enough energy content to do this. A round polar bear is a happy polar bear and it requires a lot of energy to keep a polar bear chubby! The alternative food sources may well add a small portion of energy to the bears’ diet, but in the grand scheme we are talking a fairly insignificant amount.

There are two major reasons why the alternative food items cannot work as a full-on substitute for seal:

1) The good alternative food sources are not infinite.
Polar bears are sometimes seen foraging in seabird colonies on the steep bird cliffs in the arctic. The bears are quite the avid climbers as you can clearly see in the impressive pictures here http://dailym.ai/1Ndq2L5 and here http://bit.ly/1j7bPm5. The bears also target the ground-nesting geese in the arctic. As an alternative food source, eggs are actually a reasonably energy rich food. However, bird eggs are very small compared to a seal, meaning that the bears must consume a much higher number of eggs to get the same amount of energy they would from eating a single seal. This means that a single bear visit can be absolutely devastating to a bird colony (see this link for an example re. goose eggs: http://bit.ly/1YZnPGw). In other words, eating eggs may well be a good strategy for a while, but if the majority of the eggs produced by the birds in a specific colony are eaten every year, it won’t take long before that colony simply doesn’t exist anymore. In other words, bird eggs are a nutritionally sound alternative to seals, but they simply aren’t abundant enough to ensure the long-term survival of polar bears. The same is true for caribou as well as dolphins and other whales such as belugas – there simply aren’t enough of them around to sustain the world’s population of polar bears (http://bit.ly/1L5aR4M).

2) Polar bears are not made for hunting on land.
Polar bears are marine mammals and not specialized for hunting by running on land for an extended period of time, e.g. when chasing geese or caribou (the bears severely overheat very quickly, even in cold temperatures). A persistent bear may well get a caribou every now and then, but most healthy adult caribous paying attention to its surroundings should be able to outrun a bear. This means that catching such terrestrial prey is often very energy demanding. Polar bears are curious creatures and opportunistic feeders, so I am by no means suggesting that they won’t try, but it means that feeding on geese or caribou does not constitute a solution for long-term polar bear survival. If the bear is to stay round and healthy, its overall energy intake must be at least equal to its energy expenditure. Otherwise you will ultimately end up with a very skinny bear that doesn’t have the energy to reproduce, to nurse its cubs, to stay warm during the winter months, to hunt successfully on the ice, etc. etc.
In other words: the polar bears are not adapting long-term, they are simply doing their best to survive short-term while waiting for the ice and the seals to come back.

*This image is copyright of its original author

Note: Dr. Thea Bechshoft, is a Polar bear expert and researcher Reply