Are Snowshoe Hares Evolutionary Tortoises?

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Snowshoe hares have been in the news because a new study has shown they can’t turn brown as fast as the snowy ground where they live, now that winters are being shortened by global warming. Which begs the question: Are snowshoe hares able to adapt to climate change? One answer is that they must if being camouflaged has any evolutionary benefit and they are to survive. But will they?

PHOTOS: Evolution Before Your Eyes

The authors of a paper in Proceedings of the National Academy of Science watched 148 wild hares at a site in Western Montana over three years, which included the shortest and longest snow seasons in more than 40 years. They found that, for the most part, the hares were unable to adjust to the timing or duration of the color change to keep up with earlier snow melts, which suggests they use other cues, like daylight length, to determine when they molt and change colors.

Then the researchers used climate projections to predict future changes in snow cover and found that hares, and at least eight other Arctic mammals that change colors seasonally, will soon be facing three to eight times more days on brown ground each year.

The evolutionary benefit of being snowy colored is to avoid being and eaten by predators (some of which are also camouflaged white, incidentally, and may be easier to see and escape if they, too, don’t adapt rapidly to the changing climate). So what will happen if the snowshoe hares, as a species, can’t adapt?

In very simple terms they must, to use a popular phrase, “adapt or die.” But what most people forget when using that phrase is that adapting means a lot of dying has to happen. That’s the only way beneficial adaptations can be selected for and preserved, while harmful traits selected against: Death and little or no begetting of offspring. That’s the tyranny of evolution.

The next question is, can the hares adapt quickly enough? Traditionally the answer has been no, not in the face of a rapid rate of climate change we are now seeing versus the slow rate that animals evolve. But there are already examples of birds, amphibians and other kinds of animals that are bucking that trend and adapting very quickly. So in the evolutionary race will hares prove to be hares or tortoises? Only time will tell and a follow-up snowshoe hare study in 10, 20, 30 years would be very interesting.

Images: Wikicommons