White Rabbits Imperiled by Climate Change! — Well, maybe not.

Guest Essay by Kip Hansen



L. Scott Mills, of the Wildlife Biology Program, Department of Ecosystem and Conservation Sciences, University of Montana, has been working on the seasonal dimorphism of the snowshoe hare (seasonal coat color polyphenism) for many years now. In 2013 he produced a much publicized study that purported to show that snowshoe hares (Lepus americanus) were imperiled by climate change — being unable to keep their coats properly lined up with the seasons so as to be white when the ground was snow covered and brown when there was no snow.  [ Original study link, in pdf here ]

Mills et al. captured and radio-collared about 150 hares over a three year period and then tracked them down at spring and fall molt times, photographed them against the ambient background and evaluated if there was a color mismatch (white on brown or brown on white).  Then Mills and his team, using CMIP5 climate models to project probable snow-cover season length (and dates) for mid-century and end-of-century, found that “the reduced snow duration will increase the number of days that white hares will be mismatched on a snowless background by four- to eightfold by the end of the century.”  Since predation is the major factor determining snowshoe hare population, increased exposure through visibility would mean increased predation and plummeting populations.

“We took advantage of a serendipitous triplet of consecutive winters (2010–2012) at our US Northern.  Rockies study site in western Montana that spanned among the shortest and longest snow years in the recent past. We monitored 148 different snowshoe hares over the study period (43 different hares in 2010, 63 in 2011, and 58 in 2012), using radiotelemetry to locate hares weekly to quantify coat color phenology and the snow around each hare..”.

“The hares couldn’t adjust the date that they started to change color very much, Mills and his colleagues report online today in the Proceedings of the National Academy of Sciences. Each year, the animals started to molt around the same time—10 October in fall and 10 April in spring. “That happened regardless of whether there was a ton of snow on the ground or not,” Mills says. In the fall, switching to white took 40 days. In the spring, the changeover to brown took between 30 and 50 days and lasted longer in the colder years, Mills says. “They do have some ability to speed up or put on the brakes [on color change].”” 

The onset of the fall molt — brown to white — is driven by photoperiodism (day length) and is apparently independent of temperature or presence or absence of snow.  The duration of the fall molt — start to finish — was the same in the three studied years, even though the three winters were vastly different.  Spring molt — white to brown — also started around the same date each year, but duration varied taking longer in the colder of the three years.  (NB:  Three years is a very small sample, so we should not make too much out of small differences between years.)

Mills’ assertion that “They do have some ability to speed up or put on the brakes [on color change]” is merely anecdotal given the small sample size and may be coincidental — or the spring molt duration could depend not on snow cover or temperature at all, but on availability of food by quantity or type, for instance, which would also change in step with length of winter.  I can think of many factors that would affect the Spring molt in particular — body condition of each individual after a long winter might slow the molt, health of each animal and amount of “spare” energy available to it for the molt.

An interesting note,  that will be important later on in this essay, is that none of the hares radio-collared in the first year survived to the third year:

Wild snowshoe hares generally have low annual survival rates, limiting the expression of individual plasticity across >1 y. Of our 148 different animals monitored, only 7 survived for >1 fall or spring molt and only one survived for >1.5 y after collaring; because of incomplete detection and temporary emigration of radiocollared animals, we were not able to document consecutive spring or fall molts for any of these 7 hares.”

In effect, nearly all of their test subjects died after being observed for 1 Fall or 1 Spring molt.  They were not testing/observing the same hares multiple times, but different hares at different times.   This also implies a fantastic reproductive recruitment rate necessary to maintain the population size with individual lifespans similar to that of many insects or rodents — 1 to 2 years (or two winters – the lifespan of a hamster).

Almost nothing need be said here of the pretense that winter length and extent of snow cover can be predicted 50 to 100 years into the future on a regional level by existing CMIP5 climate runs.    However,  the paper claims just that for this small area.  The time period of the study itself illustrates the silliness of this — they did the study over three back-to-back years which had a snow-cover seasons that varied from 160 to 190 days.  Their projected mid-century seasons, for both RCP4.5 and 8.5 have overlapping confidence intervals with the entire span of the three years studied:



As we see in their Figure 5 above, the posited “color mismatch” grows as they allow the models to predict shorter winters with less snow cover. [Green lines added to illustrate that all of the future mismatch derives from shortening the projected winter snow cover.]

The concluding paragraph of the paper is an interesting study itself:

“As a threshold trait with distinct initiation and rate components that determine crypsis [the ability of an animal to avoid observation or detection by other animals], coat color mismatch is a more direct climate change-induced phenological stressor than the trophic-level asynchronies usually discussed. The compelling image of a white animal on a brown snowless background can be a poster child for both educational outreach and for profound scientific inquiry into fitness consequences, mechanisms of seasonal coat color change, and the potential for rapid local adaptation.”

The authors actually recommend using the following image as a “poster child” for climate change propaganda (which they call “educational outreach”).


That was then — 2013.  And now, in June 2018, to be fair, L. Scott Mills, lead author of the 2013 paper just discussed, appears as a co-author of a new paper.  [The Author Contributions section of the new paper shows that Mills (along with five others) “designed the study” and supplied input to those actually writing the paper, as well as approving the final manuscript as part of the team.]  The new paper  is a study of the genetics of this color-changing ability of the snowshoe hare using “whole-genome sequences for a winter-white hare” is titled “Adaptive introgression underlies
polymorphic seasonal camouflage in snowshoe hares”.  This new paper is a follow-up called for by  Mills’ (2013); a “profound scientific inquiry into …. mechanisms of seasonal coat color change, and the potential for rapid local adaptation.”

Those who have studied gene-driven evolution in the last twenty years, or who actually understood the differences between gene-driven evolution and strict-Darwinistic “survival-of-the-fitness evolution”, might wonder about Mills’ 2013 work.  I certainly did — wonder, that is.   Did he and his team really think that the hares would change color depending on the background of the 60 foot circle of land on which they were photographed at some random times? Did it not occur to them that in the Spring, hares would be most often found where there was a food source, meaning ground not snow-covered?  —  thus appearing in early spring to be a color-mismatch (judged by 10-meter circle).   Did they think that they were chameleons who change color based on background?  Were they surprised to find that the hare’s molts were keyed by day-length (photoperiodism)?

The truth is that hares all over the northwestern United States undergo various degrees-of and variously-timed polymorphism. The featured image of this essay shows a partially-molted hare in the Spring or Fall. The 2018 paper includes this illustration:


[ Link to new 2018 paper.  Pdf is at DOI: 10.1126/science.aar5273 ]

This is all detailed in the new paper. L. Scott Mills deserves kudos for his dedication to scientific rigor — as we shall see — the findings of the new paper eliminate climate change as a direct cause and move the driver back where it belongs — to breeding patterns and survival rates.  More specifically:

“We have shown that introgression has shaped locally adaptive seasonal camouflage in snowshoe hares. Recurrent introgression of coat color variants could facilitate evolutionary responses to environmental change within populations as well as the long-term maintenance of adaptive variation among species….. The evolution of winter-brown coats in snowshoe hares may have enabled their persistence in environments with more ephemeral seasonal snow after the end of the last glacial maximum. Temperate snow-cover duration is predicted to dramatically decrease over the next century under most models of climate change, which may further intensify directional selection for winter-brown camouflage. Thus, the establishment of this dynamic color polymorphism through introgression is likely to be a critical component of ongoing adaptation to rapidly changing seasonal environments in this iconic ecological model.”

Translating into Plain Language, snowshoes hares have been through periods of longer and shorter winters, and more and less snowpack and cover, and polymorphism has been retained in the much of the species — at the same time, other segments of the species have less polymorphism, either in degree of color change or length of change.   The interbreeding of these populations, which co-exist in area, at least at the edges, drives rapid allele frequency shifts manifesting differing color-shifting schemes — that is introgressive hybridization (which generally results in a complex mixture of parental genes).

The authors supply charts of the “Exome SNP associations” but for the rest of us, this little chart segment, ala Gregor Johann Mendel, should be explanation enough.


All of this means that the snowshoe hare is not going to be wiped out by climate change — but rather, as a species, it easily adapts, rolling with the punches of Nature, as it has always done in the past through the mechanism of introgressive hybridization allowing the best, pro-survival mix of polymorphism alleles to manifest in the wider population for current regional conditions over fairly short periods of time, especially effective given its short lifespan, heavy predation and rapid reproductive recruitment cycle.

Self-correcting science, advancing one step at a time:  L. Scott Mills called for, and eventually got,  a more profound investigation of the seasonal polymorphic color change of the snowshoe hare  — and signed on as an author, helping to design the genetic sequencing experiment despite the fact that the new findings would contradict his earlier paper’s prediction that “Without evolution in coat color phenology, the reduced snow duration will increase the number of days that white hares will be mismatched on a snowless background by four- to eightfold by the end of the century.” Maybe the new paper could be looked at as confirming his earlier prediction.  But it doesn’t require more or future “evolution” — the necessary traits already exist in the genetic makeup of the snowshoe hare population which allow it to adjust to shorter-than climate-scale (30 years) changes in conditions, guaranteeing their long-term survival as a species.

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 Sample Press Coverage:

Science Magazine (2013):  Color-Changing Hare Can’t Keep Up With Climate Change

NPR (2013):  Climate Change Leaves Hares Wearing The Wrong Colors

NatGeo (2014):  Can Snowshoe Hares Evolve to Cope With Climate Change?

Peninsula Clarion — Alaska (2016):  Refuge Notebook: Climate change does not bode well for snowshoe hares

Science Magazine (2018):  How the snowshoe hare is losing its white winter coat

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Authors Comment Policy:

 Evolution is always a tricky subject to discuss with the general public — there are a lot of opinions and as many flavors of evolutionary theory as there are of ice cream — discussions can become heated. Let’s try to avoid that here.  In this case, the controversial aspects don’t present themselves as the problem and its solution, already enacted by Nature,  turn out to be based on fairly simple dominate/recessive genes (alleles) that regulate seasonal coat color in snowshoe hares.

I will point out that the science press did not seem to understand that the second, most recent, paper eliminates the threat to the snowshoe hares…they all link back to the 2013 paper as if its conclusions were still valid.

I am always happy to see when some bit of science gets set pretty well straight.  What do you think?

Lead with my first name, Kip,  if you are speaking to me in your comment.

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Martin Rettig

Thank God it wasn’t Black Rabbits, well maybe Black Rabbits 24/7 on the news instead of separated kids, separated kids pushed Russia aside, the MSM is a joke.


Did you hear about the separated kid that the smugglers abandoned out in the desert all by himself?


Nope, White rabbits.
Remember, what the door mouse said….


This was a great article by Kip Hansen, with equally great comments.
So I couldn’t resist…


Yirgach : Thanks for that ! I haven’t heard it in years !


You’re very welcome.
There was some great music at that time.



And if you go chasing rabbits, and you know you’re going to fall
Tell ’em a hookah-smoking caterpillar has given you the call
And call Alice, when she was just small


“using CMIP5 climate models “…..would someone please point out to these “scientists” those models have never predicted anything right

….follow up story….predator population rebounds….film at 11


Could not a more controlled study be conducted that actually looks for color change based upon controlled lighting? Is breeding really a concern as these things breed like…..

Joe Civis

I am sure that will be the conclusion of their next tax payer funded “study”… “rabbits have been found to breed like rabbits”



Steve O

Scientists generally believe in the transformational power of evolution, even between kinds. But not when it comes to the ability to adjust to an extra degree or so of warming per century.


Let us never forget this: virtually every animal and plant species in the World has lived through repeated glacial/interglacial cydles. They are either able to adapt to drastic climate changes or able to move to new areas as climate changes. If they couldn’t they wouldn’t be around today.

Exception: a small number of species (mostly plants) that have originated during the current interglacial.

Gary Pearse

Tty ..and even the arrival of new plants is an adaptation that was a capability of the parent plants

Tom Halla

All that might happen is the shift of populations northward, as there is already a range of color shifting tendencies in the existing population.


It is a wonder how these rabbits survived all those climate changes in the past. Maybe it is because they breed like — well ere, maybe,perhaps: rabbits! (sarc.

Sad that Scott Mills felt he had to bring in the CAGW comment. Totally irrelevant; but I suppose necessary to ensure publication.

I suspect that those rabbits which died were relying on their inbuilt genetic algorithms rather than facing reality. We humans could learn a thing or two about that.

But this is about a particular species in a small region of the World that experiences far wider changes up and down than the much smaller global average changes and longer time scales. A local regional American thing, in human lifetimes. Not of global relevance, but it got a grant. What is the difference between climate science related anthropological research and anthropological research that isn’t? A: One gets a grant..

Rick C PE

This study raises a number of questions in my mind.
1. What killed the bunnies? Predation, starvation, freezing, heat stroke, old age?
2. What proportion of those killed by predators were color mismatched at the time?
3. Might wearing radio collars affect the hares’ ability to evade predators?
4. In many areas of their range, snow cover is not normally continuous from Nov. thru April. Wouldn’t white hares take a hit during winter thaws?


#3 + What kind of human scent did they leave on them? The other bunnies might run from them.

Steve Lohr

If only these “researchers” would quit strapping on their climate predictions to every inquiry they might be able to get out of each other’s way. They need to start with “Nothing is going wrong here” and try to find out what is really happening.


The rabbits will have no problem, even assuming the worst case climate prediction were true.

This is a classic example of how evolution is supposed to work. We have a short-lived animal which breeds prodigiously to offset high losses from predators. Over time rabbits whose color is better matched to the environmental conditions will show a higher survival rate, and thus become more common.

We’ve seen this happen before with moths in the UK. Heavy coal use changed the environmental colors so that soot colored moths began to dominate as they were less visible to predators.


Thomas Homer

“none of the hares radio-collared in the first year survived to the third year”

What color are the radio collars? Do the radio-collars change color at the same time as the hares? Did they just prove that affixing radio-collars to snow-shoe hares leads to a shorter life span?


I’m going on memory, but ‘unexpected’ effects of experimental designs aren’t uncommon. I remember a study on a ground nesting bird where the researchers marked the nests with flags so they could keep track of them. The local crows soon figured out that the flags meant food and the study had to be redesigned. I think WUWT reported on the Nature paper a couple of years ago that demonstrated that King Penguins with metal tracking bands had much higher mortality and much lower reproductive success than unbanded penguins. Predation on Snowshoe Hares is undoubtedly high, but I think 100% mortality is pretty extreme and either the capture and/or collaring likely contributed to the high death rate.

J Mac

I suspect a few generations of predation-driven removal of seasonal color mismatched rabbits will resolve any ‘climate change’ related coloration gene concerns. Rabbits, being prolific breeders, allows for relatively ‘fast’ gene optimization based on predation-driven color selection.


Modern research…

[1] Find a case to study — can be anything. Snow hares, Arctic foxes, Baby seals, skinny Polar Bears, Puffin chicks, Walrus migrations, Mosquito air densities in July, arrival of first snows, Melting of a river, Stories from old Inuits. Whatever.

[2] Collect a sampling of data — and build up a constellation of statistical hoo-hah about it. R-squared correlations, multivariate diddly, nonlinear regression, kurtosis and third order derivatives.

[3] Find correlations that are but-nekkid obvious — and blithely present them with rich possible causation … related to (drumroll…) natural causes and then slip in the Future Looks Bleak™ by way of catastrophic climate change patterns.

[4] Leak the preprint study to the press — which isn’t hard, since they’re hugely bored with most everything, and quite willing to take suggestive language and mould it with first-grade journalist interns into something barely passable as English.

[5] Apply for grants — to further the studies.
[6] Get them, spend them — and earn an adjunct professorship.

Keep doing № 1 thru 6 as often as possible. Attend endlessly available symposia and conferences; apply to chair committees; visit a few congress clowns, and let them know your team is available to further identify good-for-reelection studies.

Another career is coined.


Gary Pearse

Kip, you are a treasure as a tranlator and educator across the spectrum of the sciences for the interested layperson. I didnt think that the subject of research into seasonal color change of the hare was going to be so interesting and novel with a bonefied scientific discovery that gives further insight into the wonders of nature.

I bought a farm in eastern Ontario, Canada in the 1970s to raise a family of three girls and three boys to keep them busy, keep them dependent on a school bus to give me a little more control of their free time in a society that was worrying with the availability of drugs and other iffy ‘distractions’. It was a mixed farm which included a truck garden, dairy cow, flock of sheep, ducks, geese, Rhode Island Red egg layers, and New Zealand rabbits, which are white all season long.

Rabbit has a prime market in sufferes of stomach ulcers and the meat price was excellent. Regarding reproductive power, I once calculated that from a pair of rabbits, one could produce as much meat as one beef cow, given the gestation period and two year rearing needed to produce beef. They ate alphalpha hay and a small amount of oats much like the beef.

Smart Rock

Never underestimate the power of natural selection.


Darwin awards?


Don’t they get tired of being wrong?



No one ever gets tired of being wrong.

It’s convincing them you’re right that’s tiresome.


So these bunnies didn’t quite live (litterally) up to expectations? What are the chances that a collar, radio transmitter, and battery slowed them down that half step from escaping a preditor?


I really can’t find the point of this study. The poor rabbits only lasted a year or less, so is global warming going to cut this down to the point where they die before they can reproduce?

I doubt they reproduce during the winter and if a rabbit is born in the Spring, according to their sample group they probably aren’t going to make it to next Spring in our current climate, let alone 30 to 50 years from now.


Needs more fluffy bunny pics

Matthew R Epp

Perhaps Mr. Mills knew his audience for the initial study would be Pro-AGW faculty and thus his study had to have the right conclusion in order to be accepted and published.

Now that he has received his Doctorate, perhaps he is trying to do real, or at least better science?

Mike L.

Was this paper peer-reviewed? If so, by whom? Even I could pick holes in the logic, and I know very little about hares, or even rabbits. When we were kids in England many years ago, we were taught that the first thing we should say when waking up on Easter Sunday morning was “White Rabbit”. Don’t ask me why! But now, I will try really hard to remember to say “dimorphism snowshoe hare” instead!
I suspect I will forget.

Ben Vorlich

This came into my head, something from decades ago.



How many different ways can a bunny die?

But it’s climate change.

Of course it is.


Excellent article.

What is missing from your detailed deconstruction are some additional major problems with L. Scott Mills’ gross assumptions.

You nailed several of the assumptions Mills was operating under; e.g. snowshoe hares relate to food sources, versus Mills’ opinion of a place to photograph hares.

Other Snowshoe hare basics that Mills overlooks is the predator prey relationship.
Mills bases his findings about the hares from a human perspective ignoring the diurnal periods when hares and snowshoe hare predators are active and how they visualize and spot their prey.

i.e. none of the predators hunt based on simple humanistic white on brown or brown on white perspectives. A snowshoe hare predators hunt based on movement and/or scent. A common hare tactic si to freeze until danger leaves or discovery is imminent.
Snowshoe hare field running give hares excellent chances to escape. i.e. if the hares are weighed down with bulky balance ruining battery packs and radios.
Many snowshoe hares predators have excellent night vision, minimizing color in favor of shades of grey/light.

Then there is Mills’ gross assumption that snowshoe hares blend into snow or brown. At the altitudes snowshoe hares are found, frosts, night freezes, hoarfrost, pockets of snow, etc. give partially molted hares excellent cover.

Hares and rabbits pluck their fur. Giving Lepus additional options.

That snowshoe hares live short fecund lives in no surprise to any decent biologist, naturalists, hunters, etc.

Every one of those knowledgeable people will expect radio collared hares to live much shorter lives; where even a few ounces hinders and hampers long eared rodentia dependent upon speed.

What poor critter is next on Mills bad research lists? Ptarmington? Arctic fox? Polar bear? (hint hint)

One of the surprises my son brought home from college was a rabbit, he named her Nini.
Now, I’ve raised rabbits several times for food and fiber (angora).
All of which were kept caged outside, or in a barn.

Nini was my first indoor rabbit raised to be a house bunny. Which gave me ample opportunity to learn about rabbits, their moods and their territories. Let’s face it, she owned me, not the the way around.

Any change to her territory, i.e. our house, e.g. a shoebox or even a shoe placed on the floor, was carefully investigated and tasted by the rabbit.
Larger boxes/bags were rabbit investigated inside and out. (N.B. Shoes accessible to the rabbit quickly lost laces. It is possibly the closest my wife ever got to housebreaking her husband, as Nini quickly taught me to put shoes, coats, gloves, hats, umbrellas, etc. in the closet)

That careful investigation process allows rabbits to build run/escape routes and maps. Which allowed mischievous bunny to bite and run for her entertainment.

Once at a conference two scientists from the University of Montana were presenting a graph in which they had plotted the log of the log of the log of the response variable against the log of the log of the log of the explanatory variable. In the question period I asked why they had taken so many logarithms. The lead author said “We found that the more logs we took the straighter the line got”

True story


Of course WHAT THEY SHOULD have done is obvious !
They SHOULD HAVE contacted DISNEY LAND and arranged for a CARTOONIST
beginning to lose the plot too ?????????????????

Andy Pattullo

Utter nonsense. They treat the seasonal color change as a fixed trait rather than a suite of genetic traits shared by a species which will clearly allow those most in sync with seasonal changes to flourishh and spread their genes and those most at disadvantage to have their genes culled from the genetic pool. They also use specualitve and, to date, wrong-on-nearly-all-predictions climate models as useful indicators of what the climate will be decades from now.

Michael Moon

Snowshoe hares – BioKIDS – University of Michigan

In the wild as much as 85% of snowshoe hares do not live longer than one year. Individuals may live up to 5 years in the wild. ( Carey and Judge, 2002; Kurta, 1995) Range lifespan.