The statistics regarding a worldwide climate trend toward global warming and the resultant loss of biodiversity are alarming—and attention getting, to say the least. Most of us have heard the often-quoted statement that the planet’s polar bears could be gone by the year 2050.
But recent wildlife observations and field research indicate that we might not want to count out polar bears quite so soon. We tend to forget that animals are resourceful, especially when they choose to become “adventurous eaters.”
Eggs for breakfast
In the past few years, as the Arctic sea ice has been rapidly melting due to a warming world, polar bears have been learning how to become more adventuresome in their diets. Scientists have been finding evidence that the bears may be turning to snow goose eggs to help them survive.
Typically, a polar bear will hunt seals out at sea, returning to the land when springtime temperatures begin to break up the ice floes that the bear needs to use as hunting platforms and rest stops. Climate change, however, has been causing the sea ice to dissipate earlier each year, forcing the polar bears to come ashore sooner. This brings the bears back to land at just about the time that snow geese are incubating their eggs around Hudson Bay, providing the bears with a valuable backup food source. A snow goose egg is approximately twice the size of a chicken egg, but it is far more nutritious. Eating approximately 88 of them will give a polar bear the caloric equivalent of a seal meal.
While some have worried that the hungry polar bears might now be a serious hazard to the snow goose population—or even wipe them out—studies, such as one recently published in the ecology journal Oikos, indicate that the currently plentiful snow geese are in no danger from the polar bear predators. The report states that although the polar bear-snow goose overlap “may reduce snow goose numbers, [it] will not eliminate this over-abundant species that poses a threat to Arctic landscapes.”
Creosote for dinner
Polar bears aren’t the only wildlife species now being observed exercising a sense of adventure when it comes to eating. Sand tiger sharks (also known as “sand sharks” or “gray nurse sharks”) have one of the lowest shark reproduction rates. They are listed as vulnerable and are protected in much of their range. As with polar bears, however, while it was once thought that sand tiger sharks would be extinct by 2050, there is now new hope that they just might find a way to live in a warmer world.
Warmer waters along the Australian coast are allowing sand tiger sharks to finally move through the Bass Strait, an area formerly off limits to them due to cold temperatures. Their staple is small fish, but they will sometimes eat crustaceans and squid. This new habitat in the Bass Strait will provide plenty of food for them to thrive again.
The ability of wildlife to go beyond usual menus and find ways to make a living in warming times is not just a contemporary development. For thousands of years, woodrats throughout what is now the Great Basin of Utah and Nevada and the Mojave Desert of southwestern Utah, southern Nevada and southeastern California ate juniper to survive. But as the last Ice Age waned between 18,700 and 10,000 years ago, the Southwest grew warmer. Juniper trees disappeared from what is now the Mojave Desert, depriving woodrats of their favorite food. The creosote bush, originally from South America, soon invaded. While juniper is somewhat toxic, it is no match for the highly poisonous creosote.
Although it’s not clear whether woodrats already had genes that allowed them to eat creosote or if there was a mutation in their detoxification genes over time, the Mojave woodrats with those specific genes were more likely to survive on creosote, while those in the Great Basin stuck to juniper.
During periods of planetary warming, such as what we are experiencing now, plants respond to increased carbon dioxide in the atmosphere by making more toxins. In a study published in the journal Molecular Ecology on April 7, 2009, lead author and University of Utah biologist Denise Dearing reported that she and her team captured eight woodrats from two Western areas: the Mojave Desert and the cooler Great Basin. Rats from both areas were fed rabbit chow mixed with either creosote or juniper. The scientists then scanned the rodents’ genetic blueprints to look for “biotransformation genes,” active genes that produce liver enzymes to detoxify the poisons in creosote and in the less-toxic juniper. If we can understand how woodrats are able to change their organismic biology to adapt to changes in their ecosystems, we may be able to predict whether other species will be able to deal with climate change.
By showing us that they are willing to engage in some “adventurous eating,” polar bears, sand tiger sharks and woodrats are proving that the year 2050 may not be so dire after all.
Here’s to your adventures, in whatever corner of the world you find them,