Unable to gather support from Maine's congressional delegation, supporters of a North Woods national park are now setting their sights on a new goal: getting President Obama to designate the North Woods as a national monument. We asked John Pastor, an ecologist with 40 years of experience studying the North Woods and author of What Should a Clever Moose Eat?, to weigh in on the debate. 

The North Woods is a magnificent band of forest, stretching from northern Minnesota to Nova Scotia, and is home to moose, wolves, beaver, bobcat, lynx, loons, and many other iconic northern animals. The North Woods is where the range of sugar maple to the south overlaps the range of balsam fir and spruce to the north. This is the land of fall colors, Christmas trees, and maple syrup.

The beauty of the North Woods has been preserved in many parks, recreation areas, and wilderness areas throughout much of its range. These parks have been kingpins of the economy of the surrounding region. But, as Aldo Leopold said, natural preserves are also “land laboratories” where we can learn how nature works to help us better manage the natural resources outside them. These land laboratories need to be large to encompass the scales of ecological processes such as fires, watersheds, and animal movements, among many others. Many of our ideas in ecology have been shaped by research in the large preserves of the North Woods. How fire controls the dynamics of forests was first documented in the million-acre Boundary Waters Wilderness of northern Minnesota. The long-term research on wolf-moose and moose-vegetation relationships in the 575,000 acre Isle Royale National Park in Lake Superior are classic studies in population and ecosystem dynamics. The concept of a watershed to protect the headwaters of the Hudson River was the basis for the preservation of the six million-acre Adirondack Park in New York.


Photo credit: John Pastor

But east of the Adirondacks, there are few nature preserves of the size needed to understand how this part of the North Woods works. The largest is the 209,000 acre Baxter State Park in Maine, home to Mt. Katahdin at the end of the Appalachian Trail. But now, due to the generosity of the Quimby Family Foundation, an additional 100,000 acres is available for preservation adjacent to Baxter State Park. This is the area Thoreau wrote about in “The Maine Woods.” Together, Baxter State Park and Katahdin Woods will be the largest preserve of North Woods east of the Adirondacks. Discussions are underway for this tract of land to be awarded federal protection as a national monument, recreation area, or perhaps park.

Katahdin Woods and Baxter together will make a valuable land laboratory for learning about the North Woods. This area of Maine differs from the rest of the North Woods in several important respects that will determine how it will respond to climate change, the largest ecological problem facing this biome. There is a strong gradient from wet maritime climate in Maine to a dry continental climate in Minnesota, and it is unlikely that the North Woods will respond to climate change in the same way at both ends of its range. Maine is the center of the range of red spruce, which does not extend much farther west than the Adirondacks, and how red spruce will respond to a warmer climate is currently unknown.

Three hundred thousand acres of natural preserve in the center of Maine’s North Woods would greatly enhance our ability to address these and other questions in ecology. As is the case with almost every national park or monument, federal designation for Katahdin Woods is bathed in controversy at the moment. But if we take the long view Aldo Leopold had, the preservation of Katahdin Woods will eventually be hailed as a vision with great foresight.

How long should a leaf live? When should blueberries ripen? What should a clever moose eat?

Ecologist John Pastor answers these questions and more as he explores the natural history of the North Woods in his new collection of essays, What Should a Clever Moose Eat? Beginning with the geological history of the region and moving through the arrival of plants, herbivores, predators, and finally humans, Pastor is a joyful observer of nature who makes the North Woods come alive for scientists and non-scientists alike. Take a walk in John Pastor’s North Woods—you’ll come away with a new appreciation for the game trails, beaver ponds, and patterns of growth around you, and you won’t look at the natural world in the same way again.

Check out an excerpt of the book below. 

Island Press caught up with John Pastor, author of What Should a Clever Moose Eat? to learn more about natural history, ecology, and the North Woods. Check out the Q&A below, then order your copy of the book to see why Discover magazine said, "Even if you've never been to the North Woods...you will come to appreciate it through ecologist Pastor. With an eye for fine detail and the gentle explication of a born teacher, Pastor crafts a rich biography of one of North America's most beautiful and diverse ecosystems, from the geology of its foundations to the birds in its skies." 

You have studied the North Woods for the past 30 years. What first sparked your interest in this area? What has continued to captivate you since then? 

Northern regions, the fur trade (which happened largely in the North Woods), and the early exploration of the northern half of the continent have fascinated me ever since I was a young boy. When I was in graduate school at the University of Wisconsin, I decided to do my Ph.D. thesis in the North Woods, and I have been thinking about and/or working in the North Woods ever since. The combination of maple, pine, birch, aspen, spruce, fir, and other species not only makes the North Woods an extremely beautiful place to do field work, but the strong contrasts in how different plant and animal species affect the North Woods ecosystem offer us an almost endless array of interesting scientific problems. 

Some activists have called for the designation of the North Woods as a National Park or National Monument. What would such a designation mean for the future of the North Woods? 

I think this could help with local and regional conservation problems, but it will not help with the largest challenge facing the North Woods, which is global warming. The North Woods only came into existence 6,000 years ago when warming temperatures after the Ice Age allowed maple, birch, pine, spruce, fir, and other species to migrate from different directions into the region from Minnesota to Nova Scotia. With further warming, the unique combination of species which is the North Woods could disassemble and largely disappear. 

The difference between the past and future responses of this ecosystem to climate change is that the assembly of the North Woods 6,000 years ago was a natural process, whereas the disassembly of the North Woods in the near future will be a result of our moral failure to take responsibility for changing the way the planet’s climate works. 

What role does connecting ecology and observation of the natural world play in tackling the myriad of environmental challenges facing the world? 

Ecology, natural history, and observations of the natural world provide the foundation of knowledge we need to face and solve environmental problems. Without this science, we are blind not only to how to solve the problems, but even to the existence of these problems. Even more so, a fascination with how the natural world works is an important part of what it means to be a human being. As Robert Michael Pyle has said, “What we know we may choose to care for. What we fail to recognize, we certainly won’t.” I firmly believe that if people could know, really know, what beautiful, living, working systems lakes, rivers, prairies, wetlands, beaches, and forests are, they would do everything they could to preserve them. Causing the extinction of a species or the demise of an ecosystem would then seem a crime equal to the defacing of the Mona Lisa or the Pietà. 

What role can natural history play in helping us understand the effects of climate change on the North Woods? What responsibility do humans have to try and mitigate damaging effects? 

The most important aspect of the natural history of an organism is how it interacts with other species and the environment throughout its life cycle. We know precious little about that for most species: most of what we know about the natural history and life cycles of most species is the paragraph on them in a field guide, and not much more. The life cycles of two species that depend on each other or control each other may become decoupled as they respond in different ways to climate change. This may already be happening with warblers and an insect they prey upon, spruce budworms. Spruce budworm caterpillars are emerging earlier in the spring with warming temperatures, and warblers are no longer able to control their population and prevent them from defoliating spruce and fir. To understand if and how interacting species’ life cycles become decoupled with climate change, we need to know much, much more about their natural history. 

You write that “natural history questions often arise from simple, serendipitous observations that anyone can make on a walk through the woods.” What opportunities are there for citizen-scientists to get involved in natural history observation or research? 

The most useful thing people can do to learn about or contribute to the scientific study of natural history is to begin keeping notebooks and records on the seasonal and annual changes in things like timing of leaf out, bud burst, flowering, emergence of mammals, turtles, and other animals from winter hibernation, emergence of insects throughout the summer, and arrival and departures of migrating birds, and anything else wherever they live. Such records will be valuable not only in understanding the range of life cycles of different species but also how they will change with global warming. For example, naturalists and ecologists are now going back to Thoreau’s notebooks to see how plant and animal species might be responding to global warming during the past two centuries. There are a number of good books on how to keep a field journal, including guidance for drawing illustrations – Keeping a Nature Journal by Clare Walker Leslie and Charles Roth is one of my favorites. Citizen scientists can share these observations with scientists and other observers by uploading their notes to the USA National Phenology Network. Citizen scientists can also assist natural history museums transcribe museum records on specimens into databases for scientists to study by going to Notes from Nature. Finally, find a local natural history organization such as a chapter of Audubon (birds), the Xerces Society (butterflies and insects), Wild Ones (wildflower gardeners), or other similar organizations and become involved with and learn from like-minded people. 

You illustrated the book and teach a biological illustration class at the University of Minnesota. What role can art play in how scientists study the natural world? 

Biology departments used to require that students learn how make drawings of observations, but in the past several decades this has gone by the wayside. This has been a big mistake. Drawing a specimen or landscape forces you to notice things that you would never notice even by taking carefully written notes. Many of these observations could be the grist for future research. More importantly, drawing or painting an organism engaged in different activities or from different viewpoints or with different techniques helps keep my mind open to new possibilities and ways of thinking about the world. 

Was there anything you found in the course of researching and writing this book that surprised you? 

After over 30 years of living in and researching the North Woods, I thought I had a pretty good understanding of things, but I was surprised by something while writing every chapter. The most important surprise is how much we still have to learn about the North Woods. A number of years ago I mentioned to a friend we were on the verge of a relatively complete understanding of how the North Woods works. Boy, was I wrong. 

What do you hope readers will take away from this book? 

Naturalists and ecologists often ask questions that most people consider, well, peculiar. Such as “What should a clever moose eat?” The purpose of this book is to explain why people should care about the questions naturalists and ecologists ask. As we become more urban, many people, especially children, are becoming increasingly estranged from nature. Yet natural history underlies many of today’s policy and legislative issues, including global warming, the sustainable harvesting of resources, the control of predators and insects, and the preservation of species. Natural history is the underpinning to conservation, to natural resource management, and to human health and food supply. We need to help people re-engage a sense of delight and wonder in the natural world to address these practical problems. 

If the reader lives in the North Woods, I hope this book encourages them to go into the woods and observe things for themselves. If the reader does not live in the North Woods, then the natural history of where they live is the best place to start. When I was in college, there was a popular poster that proclaimed: “The real world is outside. Get into it!” I hope this book gets people outside into whatever biome they live in. 

Want more from John Pastor? Check out the #ForewordFriday: North Woods Edition to read an excerpt of the book or read his blog on the movement to designate the North Woods as a national monument. 

We asked our authors: In today's age of slacktivism, has Earth Day become meaningless as a way to make impactful environmental change? Check out what they had to say below.

Travis Beck, author of Principles of Ecological Landscape Design
April 22^nd, Earth Day, is also National Jelly Bean Day. How should one celebrate National Jelly Bean Day? The internet suggests guessing the number of jelly beans in a jar, making jelly bean jewelry, or, simply, eating lots of jelly beans. The internet also suggests a number of ways to celebrate Earth Day in my immediate area. They include an Earth Day Celebration, an Earth concert, an Earth Day cleanup, a film screening, a moonlight hike, a 5k run/walk, an Earth Day festival, and an Earth Day fair. Or, if you’ve been invited to United Nations headquarters on that day, you could sign a global climate agreement.

All of this—the jelly beans, the festivals, and the signing ceremony—falls under the heading of marketing. The Earth needs good marketing. It’s too easy to ignore the pervasive, perplexing, and long term environmental issues we face in the rush of everyday life. Those recent video spots from Conservation International with Julia Roberts as the voice of Mother Nature, etc. are impactful, but a bit grim. Why not go on a moonlight hike instead, take in a film, wander a fair, or think about your nation’s CO2 emissions? And while you’re at it, enjoy a few jelly beans. Green ones.

John Pastor, author of What Should a Clever Moose Eat?
We have holidays to celebrate the planting of trees, the harvest, the four key points that define the Earth’s orbit (the solstices and the equinoxes), so why not a holiday to celebrate the whole Earth? And so we do, Earth Day, April 22. When Senator Gaylord Nelson founded Earth Day in 1970, he hoped to promote environmental activism and demonstrations, especially on campuses. Today, some campuses still have demonstrations against environmental degradation, but these are not as large as they once were. But I am encouraged by the growth of many environmental and nature organizations since the first Earth Day, such as the Xerces Society for the conservation of rare insects, WildOnes for the establishment of native plant gardens, and many others.  Demonstrations on Earth Day may not be as common, but people seem to be putting their energy into actively doing something for and learning about nature and the environment. Nonetheless, the idea of Earth Day as a day to celebrate the wonder of life on our planet home is still worthwhile. So celebrate Earth Day: if it makes you feel good, find and join a local environmental or nature organization in your area.

Yoram Bauman, author of Cartoon Introduction to Climate Change
Earth Day is a way of connecting like-minded people who care about sustainability, and hopefully (as with the Yes on 732 carbon tax campaign I’m part of in Washington State) those connections lead to more and deeper types of involvement!

Rob McDonald, author of Conservation for Cities
“A journey of a thousand miles begins with a single step”- a hackneyed quotation, but a true one. Yes, the kinds of minimal individual actions sometimes promoted for Earth Day don’t add up to much themselves. Given the magnitude of the challenge of climate change, for instance, biking to work one day a week is a pretty minor step toward reducing my carbon footprint. Similarly, avoiding food waste in my home is only a teeny step toward reducing global agricultural production. These kind of good first steps have some value on their own, but their real value is getting people to be educated and committed to an issue. For a small subset of people, these kind of first steps lead to bigger, more significant steps. Or they may lead to political support for broader legal or policy changes that do have a meaningful environmental impact. So, instead of criticizing the “slacktivists”, tell them what other steps they should take next, if they want to prove greater dedication to the environmental cause.

This holiday season, give the gift of an Island Press book. With a catalog of more than 1,000 books, we guarantee there's something for everyone on your shopping list. Check out our list of staff selections, and share your own ideas in the comments below. 

For the OUTDOORSPERSON in your life:

Water is for Fighting Over...and Other Myths about Water in the West by John Fleck
Anyone who has ever rafted down the Colorado, spent a starlit night on its banks, or even drank from a faucet in the western US needs Water is for Fighting Over. Longtime journalist John Fleck will give the outdoors lover in your life a new appreciation for this amazing river and the people who work to conserve it. This book is a gift of hope for the New Year.

Satellites in the High Country: Searching for the Wild in the Age of Man by Jason Mark
Do you constantly find your friend waxing poetic about their camping tales and their intimate connection to the peaceful, yet mysterious powers of nature? Sounds like they will relate to Jason Mark’s tales of his expeditions across a multitude of American landscapes, as told in Satellites in the High Country. More than a collection of stories, this narrative demonstrates the power of nature’s wildness and explores what the concept of wild has come to mean in this Human Age.

What Should a Clever Moose Eat?: Natural History, Ecology, and the North Woods by John Pastor
Is the outdoorsperson in your life all dressed up in boots, parka, and backpack with nowhere to go? Looking for meaning in another titanium French press coffeemaker for the camp stove? What Should a Clever Moose Eat leaves the technogadgets behind and reminds us that all we really need to bring to the woods when we venture out is a curious mind and the ability to ask a good question about the natural world around us. Such as, why do leaves die? What do pine cones have to do with the shape of a bird’s beak? And, how are blowflies important to skunk cabbage? A few quality hours among its pages will equip your outdoor enthusiast to venture forth and view nature with new appreciation, whether in the North Woods with ecologist John Pastor or a natural ecosystem closer to home.

Also consider: River Notes by Wade Davis, Naturalist by E.O. Wilson

For the CLIMATE DENIER in your life:

Cartoon Introduction to Climate Change by Yoram Bauman
This holiday season, give your favorite climate-denier a passive aggressive “wink-wink, nudge-nudge” with The Cartoon Introduction to Climate Change featuring self –described Stand-up Economist Yoram Bauman and award-winning illustrator Grady Klein. Give the gift of fun, entertaining basic understanding of what is, undeniably and not up for subjective debate, scientific fact!

Also consider: Heatstroke by Anthony Barnosky, Straight Up by Joseph Romm

For the HEALTH NUT in your life:

Unnatural Selection: How We Are Changing Life, Gene by Gene by Emily Monosson
Give the health nut in your life the gift of understanding with Unnatural Selection. Your friends and family will discover how chemicals are changing life on earth and how we can protect it. Plus, they’ll read fascinating stories about the search for a universal vaccine, the attack of relentless bedbugs, and a miracle cancer drug that saved a young father’s life.

Also consider: Toms River by Dan Fagin, Roads Were Not Built for Cars by Carlton Reid, 

For the ADVOCATE in your life:

Prospects for Resilience: Insights from New York City's Jamaica Bay by Sanderson, et. al
Need an antidote to the doom and gloom? Stressed-out environmental advocates will appreciate Prospects for Resilience: Insights from New York City's Jamaica Bay. It’s a deep dive into one of the most important questions of our time: how can we create cities where people and nature  thrive together? Prospects for Resilience showcases successful efforts to restore New York’s much abused Jamaica Bay, but its lessons apply to any communities seeking to become more resilient in a turbulent world.

Ecological Economics by Josh Farley and Herman Daly
Blow the mind of the advocate in your life with a copy of Ecological Economics by the godfather of ecological economics, Herman Daly, and Josh Farley. In plain, and sometimes humorous English, they’ll come to understand how our current economic system does not play by the same laws that govern nearly every other system known to humankind—that is, the laws of thermodynamics. Given recent financial and political events, there’s a message of hope within the book as it lays out specific policy and social change frameworks.

Also consider: Tactical Urbanism by Mike Lydon, Cooler Smarter by The Union of Concerned Scientists

For the CRAZY CAT PERSON in your life:

An Indomitable Beast: The Remarkable Journey of the Jaguar by Alan Rabinowitz
The cat lovers in your life will lose themselves in An Indomitable Beast, an illuminating story about the journey of the jaguar. This is the perfect book for any of your feline loving friends, whether they want to pursue adventure with the big cats of the wild, or stay home with a book and cup of tea.

Also consider: The Carnivore Way by Cristina Eisenberg, Jaguar by Alan Rabinowitz 

For the GARDENER in your life:

Wild by Design: Strategies for Creating Life-Enhancing Landscapes by Margie Ruddick
Give your favorite gardener an antidote to the winter blues. The lush photographs of Wild by Design, and inspirational advice on cultivating landscapes in tune with nature, transport readers to spectacular parks, gardens, and far-flung forests. This book is guaranteed to be well-thumbed and underlined by the time spring planting season arrives!

Also consider: Brilliant Green by Stefano Mancuso, Principles of Ecological Landscape Design, Travis Beck

For the STUBBORN RELATIVE in your life:

Common Ground on Hostile Turf: Stories from an Environmental Mediator by Lucy Moore
For the person keeping the peace in your family this holiday season, the perfect gift is Common Ground on Hostile Turf, an inspiring how to guide demonstrating it is possible to bring vastly different views together. This book gives lessons learned on setting down at the table with the most diverse set of players and the journey they take to find common grounds and results. If your holiday dinner needs some mediation, look to the advice of author Lucy Moore.

Also consider: Communication Skills for Conservation Professionals by Susan Jacobson, Communicating Nature by Julia Corbett

For the HISTORY BUFF in your life: 

The Past and Future City: How Historic Preservation is Reviving America's Communities by Stephanie Meeks with Kevin C. Murphy
When it comes to the the future of our cities, the secret to urban revival lies in our past. Tickle the fancy of your favorite history buff by sharing The Past and Future City, which takes readers on a journey through our country's historic spaces to explain why preservation is important for all communities. With passion and expert insight, this book shows how historic spaces explain our past and serve as the foundation of our future.

Also consider: The Forgotten Founders by Stewart Udall, Aldo Leopold's Odyssey, Tenth Anniversary Edition by Julianne Lutz Warren

For the BUSINESS PERSON in your life:

Nature's Fortune: How Business and Society Thrive by Investing in Nature by Mark Tercek
For the aspiring CEO in your life who drools at phrases like "rates of return" and "investment," share the gift of Nature's Fortune, an essential guide to the world's economic (and environmental) well-being.

Also consider: Corporation 2020 by Pavan Sukhdev, Resilient by Design by Joseph Fiksel

Red, ripe berries and fruits, such as those of mountain ash, cranberries, hawthorns, and apples, are a sure sign of a bountiful harvest at the end of summer, but after a few freezes in autumn these fruits can become deadly to wildlife. The cells of the fruits are broken open as ice crystals form, then melt, then form and melt again during cycles of freezing and thawing. The glucose and other sugars they contain are then released to natural populations of yeasts on the fruit surfaces, which ferment the sugars to ethanol, much like what happens to grapes when they are first crushed to make wine.

Quite often in late September or October, after the first hard frost, I’ve seen flocks of cedar waxwings and robins become inebriated after eating mountain ash berries. Recently, there have been several reports of moose that apparently became drunk after eating too many fermented crabapples in Alaska and piles of fermenting apples in Sweden. Birds weigh only a few ounces, so it shouldn’t take much ethanol to make them drunk. Moose, on the other hand, weigh between 500 and 1200 pounds, so it would take a lot of hard cider to get them inebriated. Petter Kjellander, Professor at the Swedish University of Agricultural Sciences, thinks that it is not possible for a moose to eat enough fermented fruit in one sitting to make it drunk. The moose’s rumen can hold only so much fermented apple mash before it must stop eating and chew its cud. This load of fermented apples probably does not contain enough alcohol to induce inebriation in a large moose, and the three hours it takes to empty a moose’s rumen should be sufficient to cleanse its system of the ingested alcohol. On the other hand, perhaps some moose, like some people, are genetically disposed to an intolerance of alcohol, and so only a small amount might get them intoxicated. The answer to this problem will likely tell us something new about the physiology of moose.

We have peculiar tastes in foods when we sit at a bar too long – witness the varieties of pickled things in typical bar food. Might a drunken moose also have the same tastes? After the yeasts create the ethanol, bacteria turn some of it into acetic acid, otherwise known as vinegar, so apples, crabapples, and berries become pickled while they ferment. Perhaps the combination of fermented and pickled apples stimulates the moose to keep eating far beyond what is good for it.

Salted nuts, chips, and popcorn are ubiquitous wherever alcohol is served, whether in bars or at a Super Bowl party. Do moose have a craving for salt when eating fermented fruit and if so, where can a moose get it? Gary Belovsky and Peter Jordan found that aquatic plants are a major source of salt for many moose in summer and perhaps in early fall when fruits in the uplands are starting to ferment. But once the ponds freeze in late fall, aquatic plants are no longer available. Then, moose are often seen licking the gravel on the sides of roads, presumably for the salt put down by transportation departments to melt the ice. A drunken moose on the side of the road is potentially a great danger to motorists, so beware if you are driving in moose country during late autumn!

And what should a moose do about the hangover the morning after a fermented fruit binge? We can go to the drugstore and pick up some aspirin, but a moose can go to the original source of this universal painkiller. Aspirin is salicylic acid and was originally isolated from the bark of willow in the genus Salix, from which salicylic acid takes its name. Willow twigs are highly preferred foods of moose from fall to spring. By the end of winter, many willows along streams and in bogs look like someone went at them with a machete, but the many moose tracks in the snow tell us the real culprit. I’ve often thought that moose eat the willow bark to stave off the pain of cold weather or crusty snow slashing their shins raw. Perhaps some of these tracks were also made by moose who became drunk by eating berries of mountain ash along the streambank or fermented cranberries in the bog. If so, then the tracks of a drunken moose should wander erratically, like a drunk stumbling home after the bars close. If I snowshoe through a willow bog this winter, I’ll keep an eye out for tracks that may have been made by a stumbling moose. If there are browsed mountain ash berries nearby, then I may be on the track of a drunken moose coping with a hangover.

In fall, about 21 mammal and bird species worldwide, mostly in northern regions, change their coat or plumage colors from brown to white. White provides camouflage against predators as snow covers the landscape in winter. In spring, these same animals shed their white colors and return to brown, which provides similar camouflage when next to the brown leaf litter on the ground. Some animals can turn white and some remain brown year round.

Only one or at most a few genes control the ability to change color seasonally. Natural selection is a powerful force determining the abundance of these genes in different environments. In a paper in the March 2 issue of Science, Scott Mills and colleagues show that the probability of turning white in winter increases with longer durations of winter snow cover for Japanese hare, white-tailed jackrabbits, and least and long-tailed weasels. With fewer than 40 days of snow cover, only 20% of the individuals of each species have the genes for turning white. But with more than 160 days of snow cover, over 80% of the populations of each of these species have the genes for turning white. In the broad range of snow cover between 40 and 160 days, the populations contain a roughly even split of winter-white and winter-brown individuals. During periods of snowy winters, white individuals have greater survival and there are more children born the following spring possessing these genes. During stretches of snow-free winters, brown individuals have greater survival and more children. Under these conditions, natural selection preserves both color forms. In order to maintain these species in a warming climate with gradually decreasing snow cover, Mills and colleagues suggest that we must conserve these particular populations with both sets of genes, thereby hedging our bets.

But there could be further complications. When the environment goes through large changes, there is a period of instability when it rapidly switches back and forth between two states (snowy and snow-free winter landscapes following one another, for example). One year there is strong selection against one trait (brown) with selection against the other (white) the following year. This instability in the environment creates corresponding instability in the organism's gene pool. It is important that the population density not drop too low during periods of environmental instability because low survival of the animals with the wrong color, one year after another, could drop the population below the minimum size needed to be viable. Hares and weasels are famous for going through boom and bust cycles every four years or so (see Chapter 14 in my book What Should a Clever Moose Eat?). During their population lows, the fate of these species may depend upon whether snow conditions align by chance with the abundance of the coat color that provides the best camouflage.

As with any good research, answering one question opens up newer and even more interesting ones. Incorporating animal population cycles into the interesting findings of Mills and colleagues seems to be a next step in designing strategies to conserve these species in northern environments.