Fade to white

TIP: To pinpoint animals that change color with the seasons, look for tiny giveaway clues.

Posted: Friday, February 04, 2011

As I glided along on cross-country skis, I thought I was quietly scanning for animals. A flash of movement in my peripheral vision, however, told me some creature had turned the tables. A blur of indistinct white moved against the snow. It stopped. After several minutes, I finally spotted the black eye of a snowshoe hare against the frozen backdrop. The hare sat absolutely still.

Several animals in Southeast Alaska change color with the season to remain nearly invisible against the shifting winter background: snowshoe hares, short-tailed weasels (aka ermine) and ptarmigan. Although each is a master of camouflage, you can decipher their disguises with close observation and patience. Each has telltale signs they can’t hide.

In snowshoe hares, for example, the change to winter white isn’t absolute. Their dark eyes don’t change and their ears remain black-tipped year round (if the ears are laid back, this may be hard to see). Although their white fur blends with the snow, the change from summer brown to winter white doesn’t have much to do with the weather. It’s the change in the amount of daylight that triggers the wardrobe swap. Which, given how fickle the snow cover can be in early winter in Juneau, is much more practical.

It takes snowshoe hares about ten weeks to completely shift color. The changing amount of light initiates hormone changes that cause the hare to grow new fur. Higher levels of the hormones generate brown coloration, while lower amounts generate white coloration. If their fur color doesn’t match the landscape when they’ve finished, the hares may tend to be more secretive until the scenery cooperates.

For hares, holding still is one of their first defenses against predators. Often they freeze in place until the last possible moment, hoping their camouflage will keep them safe. Finally, they sprint away, but often not very far. If you keep them in sight as they move, then patiently scan the last known location for a dark eye or hint of an ear tip, you may be rewarded with a glimpse of your suspect. Keep in mind, however, winter is a dangerous time for animals and they need every drop of energy for survival. It’s important to be respectful and keep from deliberately flushing winter birds and animals.

No matter how cryptic a hare’s color may be, it still makes tracks. Snowshoe hares are aptly named: their hind feet can be nearly twice as big as their front feet. The hind feet leave parallel, slightly tear-drop shaped depressions that can be almost six inches long. The front feet will register as rounder and much smaller depressions behind the back feet, usually in a single file. If you come across a hare trail, watch for movement under brush and in protected places.

Short-tailed weasels also rely on their white winter coat for protection from predators. Although a voracious predator itself, this pint-sized terror has to watch out for larger carnivores such as wolves, wolverines and birds of prey. The tip of the tail remains black whatever the season. In winter, that black patch may help save the weasel’s life as it provides for a distracting target for predators, diverting them from the weasel’s head and body.

In the summer, short-tailed weasels are dark brown on top and cream-colored underneath, including the feet and insides of the legs. In some places they are called a stoat or sable in this phase; the white phase is called ermine.

Unlike hares that keep still to hide, short-tailed weasels are constantly on the prowl. They hunt for mice and voles (a type of short-tailed mouse) in the rodents’ snow tunnels. Size is one of the characteristics that make the weasel a fearsome predator for small rodents. With its short legs and long, lean body, the weasels can follow their prey through tunnels and into burrows. Weasels have an extremely fast metabolism, and must eat between five and ten rodents per day in winter — roughly 40 percent of their body weight. That would be like a 150-pound human eating 60 one-pound steaks every day!

Tracks can also betray a short-tailed weasel to a sharp-eyed wildlife spy. Usually weasels travel in a bounding lope that moves their feet in pairs. Scan the snow for dainty tracks, usually less than an inch long, with the back feet landing close to or partly covering tracks from the front feet. If you see short-tailed weasel tracks, keep a sharp eye out for movement nearby, especially that black-tipped tail. Or, look for a pair of small black eyes keeping an keen watch on your movements.

Ptarmigan also use the subterfuge of changing their appearance with the season. For two species, the Willow and Rock Ptarmigans, their seasonal changes are more complex then their mammal counterparts — the timing is different for males and females.

Willow Ptarmigan are the only grouse species in which the male sticks around to help raise chicks, so you’ll see both parents shepherding the little fluff-balls. Mostly likely, you’ll spot the male first. Male Willows start changing into summer brown in early spring, but stop halfway through. The chestnut brown covers the head, neck, chest, and upper back, but the rest of the bird remains white. It’s like waving an “I’m here” flag for predators. Why take the risk? To get the ladies, of course! Partially white males are more visible during the time when they are defending their boundaries against other males and when females are choosing their mates.

Female Willow Ptarmigan start molting a little later than males, but make the full transformation to brown earlier, before nesting. This way they can hide while sitting on the nest, waiting for the eggs to hatch.

Rock ptarmigan take the timing difference to the extreme. Females finish changing to their speckled brown colors a month earlier than males. The males remain a brilliant white, even though it hugely increases their chance of being nabbed by a predator as the snow disappears. This seems to be because females are more attracted to the bright white males. Once the female lays her eggs, the male does something odd — he gets his feathers dirty. By dulling the white color, he has a better chance of surviving until the rest of his brown feathers grow

All ptarmigan, like hares, rely on cryptic coloration as their main defense from predators. The birds become completely still if they think a predator is near, and won’t move until the intruder is very close. This may make them seem unafraid or foolish, but they know movement will surely attract attention from their foes. Who knows how many ptarmigan you walked within just a few feet of that you never saw?

As a wildlife spy, you can use this trait to your advantage. Scan for dark eyes and beaks (and in the case of male Rock Ptarmigan, a black line between the eye and beak) against white snow. If they fly, sometimes they don’t go very far. Watch where they land, and you may have the opportunity for another visual of the ghostly shapes drawn in white on white.

• Beth Peluso is a freelance writer and illustrator and avid birder. She enjoys spying on wildlife across Alaska.



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