Swans and other waterfowl can stand on ice and swim in freezing water because their feet are designed to withstand the cold through heat exchange.
Last week I was caring for my son’s new German Shorthair puppy, Moose. As we walked on the snowy streets of Herriman, Utah, it didn’t take long before Moose began showing signs of having cold feet despite his excitement about being on a walk. He would arch his back, lift one paw at a time and whimper, then charge on, only to repeat it a bit later. He seemed happy to go back inside at the end of his exercise.
Inside, I immediately exchanged my boots for slippers, intent on keeping my own toes from suffering like Moose’s did and wondering if he needed boots too. That experience led me to think of wildlife and how they keep their feet and other extremities warm in the winter. They have no warm house, no slippers, no heating pads, yet their feet don’t freeze off. There must be a secret or two.
For hoofed animals, one strategy is that they have hooves. Hooves are basically toenails and do not require a good blood supply. This gives them an insulating layer between them and contact with frozen ground, snow or ice.
At rest, many animals curl their legs beneath them to take advantage of the body’s mass and heat. Animals with long tails, foxes, squirrels, coyotes and wolves, for instance, can also use their furred tail to protect feet, ears and noses.
Animals that live in extreme cold, such as the Arctic fox, may also have shorter ears and legs for less exposure. This follows Allen's Rule, which states that certain extremities of animals are relatively shorter in the cooler parts of a species' range than in the warmer parts.
For most animals in the cold though, blood flow seems to be their primary defense. Logic would dictate that in cold weather, more warm blood should flow to the extremities. After all, a common complaint from people with poor circulation is cold hands and feet. However, with animals that must live outdoors, sending warm blood gushing to their feet, ears and tail could be deadly if it causes them to burn through too much energy or cools the rest of their body below a threshold.
The strategy then, is really to maintain the extremities, especially feet, closer to the temperature outside (ambient temperature). Part one of this strategy is that, as a rule, the lower portion of an animal’s leg is largely tendon, ligament and bone, requiring less blood than muscle to function.
Part two of the equation for, if not warmer feet then feet that don’t freeze, is called countercurrent exchange. In this, animals have veins with cold returning blood lying next to arteries with warm blood from the heart. Heat passes down the gradient, so the warmth of the arterial blood is shunted to the colder venous blood. When the arterial blood reaches the extremity, it is cool and thus loses less heat to the environment and maintains just enough heat to keep things from freezing.
The other advantage of this system is that the warmed venous blood that re-enters the heart doesn’t cool the body’s core. This trade-off, cold feet for a warm heart, is critical to the overall survival of the animal.
In waterfowl, this system of heat exchange is highly developed. In what is called, rete mirable, or miracle net (Latin), veins and arteries are interwoven together in a fine net that allows for even better heat exchange.
Puppy Moose, it turns out, really doesn’t need boots. He is built to tolerate the cold feet, but since this was his first winter, learning about snow was just a bit of a surprise.
Help Idaho Wildlife
When we traveled across the state in October, most of the vehicles we saw using the wildlife management areas did not have wildlife plates.
C'mon folks, let's help Idaho's wildlife by proudly buying and displaying a wildlife license plate on each of our vehicles!
See below for information on Idaho plates. Most states have wildlife plates so if you live outside Idaho, check with your state's wildlife department or vehicle licensing division for availability of state wildlife plates where you live.
Wildlife License Plates
Idaho Wildlife license plates provide essential funding that benefits the great diversity of native plants and wildlife that are not hunted, fished or trapped—over 10,000 species or 98% of Idaho’s species diversity. Game species that share the same habitats (such as elk, deer, antelope, sage-grouse, salmon, trout) also benefit from these specialty plates.
No state tax dollars are provided for wildlife diversity, conservation education and recreation programs. Neither are any revenues from the sale of hunting or fishing licenses spent on nongame species. Instead, these species depend on direct donations, federal grants, fundraising initiatives—and the Idaho Wildlife license plates.
Both my vehicles have Bluebird Plates. I prefer the bluebird because the nongame program gets 70 percent of the money from bluebird plates, but only 60 percent of the money from elk and trout plates - 10 percent of the money from elk plates supports wildlife disease monitoring and testing programs (to benefit the livestock industry) and 10 percent from cutthroat plates supports non-motorized boat access.
Incidentally, in 2014, the Idaho Legislature denied the Department of Fish and Game the ability to add new plates or even to change the name of the elk and cutthroat plates (very specific) to wildlife and fish plates, a move that would have allowed for changing images occasionally and generating more revenue. It would seem that they believe that we Idahoans don't want a well funded wildlife program. Go figure.
Donate part of your tax return to support wildlife in Idaho!
On the second page of the Idaho Individual Tax form 40 you have the opportunity to donate to the “Nongame Wildlife Conservation Fund”.
Check-off this box on your next return or ask your tax preparer to mark the Nongame check-off on your behalf.
If you are not from Idaho, check with your own state wildlife agency about how you can help. Many states have a similar program.
"WOW. What a phenomenal piece you wrote. You are amazing." Jennifer Jackson
That is embarrassing but actually a fairly typical response to my nature essays. Since The Best of Nature is created from the very best of 16 years of these nature essays published weekly in the Idaho Falls Post Register (online readership 70,000), it is a fine read. It covers a wide variety of topics including humorous glimpses of nature, philosophy, natural history, and conservation. Readers praise the style, breadth of subject matter and my ability to communicate complex and emotional topics in a relaxed and understandable manner.
Everyone can find something to love in this book. From teenagers to octogenarians, from the coffee shop to the school room, these nature essays are widely read and enjoyed.
Some of the essays here are my personal favorites, others seemed to strike a chord with readers. Most have an important message or lesson that will resonate with you. They are written with a goal to simultaneously entertain and educate about the wonderful workings of nature. Some will make you laugh out loud and others will bring a tear to the eye and warm your heart.
"You hit a home run with your article on, Big Questions in Nature. It should be required reading for everyone who has lost touch with nature...great job!" Joe Chapman
"We enjoyed your column, Bloom Where Planted. Some of the best writing yet. The Post Register is fortunate to have your weekly columns." Lou Griffin.
To read more and to order a copy, click here or get the Kindle version
Copies are also available at:
Barnes and Noble in Idaho Falls
Perfect Light Photo Supply
Museum of Idaho
Valley Books, Jackson Wyoming
Avocet Corner Bookstore, Bear River National Wildlife Refuge, Brigham City, Utah
Craters of the Moon National Monument Bookstore, Arco, Idaho