Once again winter is upon us. For some of us it is a time for outdoor fun, frolicking in the snow and participating in, or watching, winter sports. For others it is the season of blah. And for a few, winter is just a challenge to survive. They are not alone. When it comes to survival, animals have developed some surprising skills and habits to avoid the cold and being eaten by predators. Here are some examples:
The caterpillars of Monarch butterflies taste terrible to keep birds away. To survive the long Canadian winters, beavers move beneath the snow among the lodges they have built and stocked with food. If food runs out, beavers take quick trips above ground, usually preferring the safety of overcast days, lest predators lurk nearby, says Michael Runtz, a naturalist in Ottawa.
Nature lover Allan Britnell cites some more curious survival techniques in the winter issue of ONnature magazine: female giant water bugs don’t bother with building a nest for their offspring. They simply lay their eggs on the wings of the male, who carries them around until they hatch. Thus, the eggs become a moving target, assuring a greater survival rate. We know that ants work collectively for the greater good of their colony. But the Formica and Lasius species – both common in Ontario – carry this to a whole other level. Both feed on sticky, sweet fluids exuded by aphids, but rather than wandering around for aphids to milk, these ants herd groups of aphids. “Lasius ants move aphids around like we move cows, keeping them in the nest in winter and moving them out onto plant roots in the summer,” says Bob Anderson, an entomologist at the Canadian Museum of Nature. In return, the “domesticated” aphids are protected from predators.
The Mayfly is another species that seeks safety in numbers as a survival technique. A rather clumsy flyer, this insect is easy prey for a wide range of birds and amphibians. But as adult Mayflies emerge almost simultaneously by the millions, their predators simply cannot eat them all.
Sometimes, just acting tough is enough to ward off predators. Throughout their four stages of development, Swallowtail butterflies employ a range of camouflaging techniques. To avoid being eaten, the caterpillars of immature Canadian Tiger Swallowtail butterflies resemble bird feces. As the caterpillars mature, they turn dark green and sprout two yellow and black spots that look like eyes. They even rear up when threatened, enhancing their snake-like appearance. The creature’s real secret weapon is the osmeterium, an appendage that resembles the forked tongue of a snake and emerges from the thorax of the insect when it detects a predator. If the potential predator still is not frightened off, the osmeterium releases a stinky chemical concoction.
Another excellent faker is the Eastern Hog-nosed snake, a harmless species that is at risk in Canada. When threatened, this snake rears up and flattens its head in a manner similar to a cobra. If that survival technique does not scare off the attacker, the snake plays possum, curling up into a circle, belly up, with its tongue dangling out of its mouth.
And then there are the salamanders. They can regrow missing body parts. They have cells, called fibroblasts, which cluster around the injured area and help recreate muscle, bone and skin tissue lost due to an injury. Some species, like the Northern Two-lined salamander, will even shed their tails to escape a predator’s clutch – and then regrow them.
Opossums are not well-suited for freezing temperatures. So the ones that have recently moved into Ontario from the south stay tucked away in protected spots for weeks to keep their paper-thin ears and naked tails from frostbite. They don’t hibernate. Neither do Polar Bears and spiders. Female Polar Bears put on over 200 pounds to prepare for the four- to five-month long food hiatus while they birth and care for their cubs in the den. When Spring makes an appearance around March, she and her cubs will emerge from the den. Over the next 2½ years, cubs will stick close to their mothers to learn all the survival tips and tricks before they take off on their own. Most spiders lay their eggs in a web and take off, letting the eggs fend for themselves. But the Wolf Spiders care more for the survival of their eggs. They strap the eggs to themselves and carry them around. Once the little ones hatch, female Wolf Spiders continue to care for their brood, even letting the newborns hitch a free ride on their backs until they are old enough to care and fend for themselves.
A curious case is the survival technique of the Wood Frog. Most amphibian species spend their winter in water or burrowed deep into the soil to insulate themselves from extremely cold temperatures. The Wood Frog, however, hibernates in the ground’s shallow organic layer, leaving itself vulnerable to freezing. This would spell death for most amphibians, but the Wood Frog can survive the freezing of 60 – 70% of the water in its body. Shallow hibernation serves this species well – and it offers another advantage: hibernating close to the soil’s surface gives Wood Frogs a head start on breeding when Spring arrives. They feel warmer temperatures before deeper-buried amphibians and get down to business right away. Consequently, the species is often the first frog to be heard, seen and recorded in early Spring.
Birds also have specific survival techniques. One in particular might be a surprise. We have noticed that more and more American Robins stay here in the winter, instead of migrating to the south. To survive they flock together in groups of up to 100 birds and search for food. When they find a resource-rich area, they stay and switch to eating mostly fruit, like crab apples, juniper berries and rose hips. Pigeons and other birds manage the cold by alternating feet and tucking one leg up under their belly.
For this edition of the Nature Notes, I have drawn heavily on field notes and on articles about animal survival techniques in ONnature, Canadian Wildlife magazine, Bird Studies Canada, and publications by the Toronto Wildlife Centre.
Winter is more than survival. In this part of the world, we are all creatures of winter. Instead of complaining about the dark and cold of the season, we should celebrate snow and ice. By reflecting 80 – 90% of incoming sunlight back into the atmosphere, snow cover cools the Earth. Snow also insulates parts of the Earth’s surface, holding heat in and keeping moisture from evaporating. When soil freezes, it prevents greenhouse gases, like carbon and methane, from escaping into the atmosphere. When snow melts, it fills rivers and lakes. Make the most of winter and unwind. Happy New Year to all. I hope you enjoyed the holiday season and took advantage of the break to spend some time outdoors, exploring our wonderful natural winter world.