I’m going on vacation next week, and I’m very excited! I’m spending some time at Mackinac Island (pronounced ma-kuh-naw), a little, car-free island between the Upper and Lower Peninsulas of Michigan.
As I looked up what type of wildlife I might find, one surprised me: the white-tailed deer.
I’m familiar with white-tailed deer, as I’m sure those of you who live in the United States are. But how on earth did deer get to an island three miles off the coast of Michigan??
The deer you know and (maybe) love
White-tailed deer (Odocoileus virginianus, also known as the Virginia deer) are the most common deer in North America. You can find them as far north as the Arctic Circle in Canada to below the Equator in Peru and Bolivia.
In part because of their wide-ranging habitats, white-tailed deer can vary considerably in size. The idea is that larger animals have a lower surface-to-volume ratio than smaller animals, meaning that they radiate less heat and can stay warmer. So, white-tailed deer tend to be largest in cold temperate climates and smallest in deserts, the tropics, and small islands. At its largest, a male white-tailed deer can be 42 inches (106 cm) at the shoulder and weigh 400 pounds (180 kg). On the opposite end of the size spectrum, the smallest variety of white-tailed deer, the Key deer of Florida, reaches only 30 inches tall (76 cm) at the shoulder and weighs just 75 pounds (34 kg).
White-tailed deer get their name from the white fur on the underside of their tail. When a white-tailed deer is startled, it raises its tail or ‘flags’ it, showing off this white coloration. This flagging behavior could help fawns follow their mother as they escape from predators through the forest.
In addition to being everywhere in North America, white-tailed deer have been around for a very long time. In fact, they are the oldest living species of deer on the planet. The ancestor of white-tailed deer first crossed the Bering Land Bridge from Asia into Alaska millions of years ago, and the general consensus is that the animal we know as a white-tailed deer evolved around 4 million years ago.
In order to survive for so long, white-tailed deer have become experts at adapting to a changing environment. Think about it: these animals were alive during the last ice age, which ended only 12,000 years ago. At one time, white-tailed deer were living alongside saber-toothed cats and mammoths. And the end of the last ice age wiped out almost all of the ancient mammals of that time. Of the surviving mammal survivors (mountain goats, musk ox, bison, bighorn sheep, pronghorns, black-tailed deer, and white-tailed deer), only the white-tailed deer have adapted to a wide range of habitats across vast swathes of the country.
Even with the rise of humans, white-tailed deer have thrived. They live in our backyards and cross our highways. There are more white-tailed deer in America today than there perhaps ever have been. That’s pretty impressive!
Surprisingly good swimmers
Now that we’ve got the background out of the way, onto the mystery of the Mackinaw Island deer: how did they get there?
It turns out to be pretty simple: they walked over the ice during the winter back in 2014. But in addition to walking, white-tailed deer also sometimes get to the island by swimming.
White-tailed deer are surprisingly good swimmers. With their strong legs and high stamina, white-tailed deer can reach speeds of about 15 miles per hour and swim as far as 10 miles (3 meters) in a single swimming session. They also have a topcoat with long, hollow hairs that make the animal buoyant in water.
In addition to their impressive swimming ability, white-tailed deer are great runners and jumpers. They can sprint as fast as 30 miles per hour and jump 10 feet (3 meters) high! This is how white-tailed deer escape predators: running, jumping, and swimming away.
Surprisingly good eyes
White-tailed deer also have surprisingly good eyesight for an animal hunted by humans wearing bright orange vests.
In some ways, white-tailed deer have better eyesight than humans. They can, for instance, see 15 to 20 times better than we can at night. In addition, white-tailed deer can process visual information much faster than humans, which lets them see and react to movement very quickly.
However, white-tailed deer vision has a weakness that human hunters exploit – they can’t see red. Now, white-tailed deer are not entirely colorblind! They are dichromatic, which means they have two types of cones in their eyes and can see two types of colors (humans are trichromatic and can see three types). More specifically, white-tailed deer can easily see blue and green but don’t have a receptor in their eyes sensitive to reds.
But even though their eyesight is relatively good, white-tailed deer rely on smell to detect danger. White-tailed deer have over 300 million olfactory receptors in their noses, many more than our measly 5 million receptors! So, while a white-tailed deer may not be able to see your orange vest, you can bet that it will smell you if you’re not careful.