What Do Squirrels Do In The Winter?

As cold weather sets in and we complain about the freezing temperatures during our morning drive to work, it's easy to forget that wild animals have to deal with the winter weather without the benefit of heated homes and cars. Squirrels, like all other animals that live in cooler climates, have evolved a variety of strategies to deal with the winter cold. Of course, the specific strategies depend on the kind of squirrel, and the area where the squirrel lives, so it's not surprising that squirrels have a variety of behaviors to help them survive the winter months.

One of the most widespread misconceptions about squirrel behavior is that all squirrels hibernate during the winter. The truth is that while many ground squirrels do hibernate, tree squirrels and flying squirrels do not. This detail was apparently missed by the producers of Sponge Bob Square Pants, who depicted Sandy Cheeks, the seafaring eastern gray squirrel from Texas, sound asleep for the winter.

Of course, everything else about this show
makes perfect sense.

For real-life tree squirrels, the most familiar behavior for coping with winter is caching food. The eastern gray squirrel of North America is famous for its habit of burying acorns and other nuts. Facing competition for scarce food supplies from nearby squirrels and other animals, the gray squirrel caches nuts over a wide area during the fall, a technique known as "scatter hoarding." It bites and licks each nut, leaving its scent before burying it. The squirrel retrieves the buried nuts throughout the winter using both memory and its keen sense of smell. It is said that a gray squirrel can locate a nut by scent even through a foot of snow.




Squirrels have refined their caching techniques to reduce the number of nuts stolen by other animals. They have been observed pretending to bury nuts when they detect another squirrel or other animal nearby, attempting to throw off any potential nut thieves.

Other tree squirrels have different strategies for winter food caching. The American red squirrel inhabits coniferous forests of the north, where it feeds largely on seeds from spruce cones throughout the winter. Rather than scatter hoarding like its gray cousins, the more fiercely territorial red squirrel gathers cones into a central location, or "midden," in its territory. The pile of discarded leaves from the spruce cones can sometimes measure a meter or more across.

American red squirrel

Although they do not hibernate, tree squirrels and flying squirrels will reduce their activity and spend more time in their nests during the winter months. In colder climates, squirrels will often alter the timing of their daily routines. Instead of going out to find food in the early morning and near dust, they will leave the nest in the mid-afternoon to retrieve buried nuts, and stay curled up in their nests the rest of the time. A small supply of nuts may be stored in the nest so that during a particularly cold stretch, a squirrel may be able to stay in the nest without leaving at all for a day or two.

Tree squirrels and flying squirrels are territorial, and adults normally nest alone. But when cold weather sets in, often several squirrels living near each other will gather in one nest, temporarily, to share their body warmth. When warmer weather returns, the squirrels will part ways and return to their own individual nests.

Unlike tree squirrels and flying squirrels, many ground squirrels (which includes chipmunks, prairie dogs, and marmots) do hibernate during the winter. Not surprisingly, the ground squirrels of colder climates are the most likely to hibernate, and the length and timing of hibernation varies by climate. Squirrels of higher elevations, such as the Alpine marmot of Europe or the Belding's ground squirrel of western North America, may have extended hibernation periods lasting as much as eight or nine months.

Squirrels inhabiting similar territories may employ sharply different hibernation behaviors. For example, the thirteen-lined ground squirrel, a very small species whose territory extends from southern Canada south to central Texas, may enter hibernation anywhere from late July to October, and emerge between March and May, depending on the local conditions. By contrast, the black-tailed prairie dog, a larger ground squirrel which has a similar range to the thirteen-lined ground squirrel, does not hibernate at all, but may go into a light hibernation-like torpor in its burrows for short periods during particularly cold weather.

Thirteen-lined ground squirrel in Lubbock, TX

The champion of hibernation among the ground squirrels may be the Arctic ground squirrel. Found in Alaska and northern Canada, these squirrels live in colonies that may number in the hundreds. They spend the short spring and summer eating and gathering food to store in their underground tunnels. They hibernate from September until April in burrows that are lined with lichen, leaves and muskox hair. During hibernation, the Arctic ground squirrel's body temperature drops to 27 degrees F (-3 C), the lowest naturally occuring body temperature recorded for any mammal. When they awaken in April, the squirrels feed on the stored leaves, seeds, and grasses that they stored in the burrows until spring plants start to grow outside.

An Arctic ground squirrel hibernating in a
laboratory at the University of Alaska

Squirrels are an amazingly adaptable and varied family of animals. They can be found in some of the harshest climates on earth. I have touched here on just a few of the strategies that squirrels employ to survive the winter months. Of course, our familiar city gray squirrels are always willing to accept a little help from their friends.

Why Did The Flying Squirrel Cross The Road?

In 2002, concerned scientists noticed that northern flying squirrels were unable to cross a stretch of scenic highway in the Unicoi Mountains of western North Carolina. This was a problem because the flying squirrels, which are declining in numbers, were unable to access foraging sites and get to others of their species for mating.

The Carolina northern flying squirrel is an endangered species that inhabits mountain forests of North Carolina, Tennessee, and Virginia. The nocturnal squirrels glide by launching themselves from a tall tree, and can typically cover distances of up to about 80 feet. But the highway, along with an adjacent treeless area on both shoulders, created a space 125 feet wide, too much distance for the squirrels to cover.

Northern Flying Squirrel Gliding

Fortunately, biologists from the North Carolina Wildlife Resource Commission and North Carolina State University came up with a creative solution to this problem, and it seems to be working. The scientists have installed three pairs of wooden poles about 46 feet high, with launching platforms at the top of each pole. The poles in each pair are situated about 49 feet apart, on each side of the road. This gives the squirrels the means to launch themselves across the highway to find food, den sites, and mates.

A Northern Flying Squirrel at a Bird Feeder

To test whether the flying squirrels were using the platforms, the research team set up cameras at the poles for a 15 month period in 2009 and 2010. During this time, they captured 14 instances of the squirrels using the poles. Here is a video showing one of these instances:





It would be nice if the success of this project could lead to similar efforts in other locations. I have written about the squirrel bridges in the town of Longview, Washington, a very successful example of helping squirrels to avoid the dangers of road crossings. Unfortunately, not every effort has been so successful. In 2010, a proposal to erect rope bridges across two highways in Arizona to help the endangered Mount Graham red squirrel was defeated by that state's legislature, due to protests from right-wing politicians who objected to the cost. Hopefully Arizona's politicians will have a change of heart before it's too late for that threatened species.

Is Climate Change Creating A New Squirrel Species?

Is it possible that global warming could be causing the creation of new species of squirrels and other animals? According to a story on the Mother Nature Network website, climate change may be the cause for increasing numbers of hybrid flying squirrels being found in Canada.

These squirrels are hybrids of two species, the northern flying squirrel and the southern flying squirrel. As the names suggest, the northern flying squirrel is native to northern regions of the United States into Canada, while the southern flying squirrel is found further south in the United States. The northern flying squirrel is larger, and has a gray and white belly, while the smaller southern flying squirrel has an all-white belly. Hybrids between the two are the size of the southern flying squirrel, with mottled gray and white belly fur.

A northern flying squirrel visiting a
bird feeder

Recently, scientists in Ontario, Canada have discovered an increasing number of hybrids of the two species. Ontario is within the range of the northern flying squirrel, but is well to the north of the usual range for the southern flying squirrel. Researchers including Jeff Bowman theorize that warming temperatures are driving some species, including the southern flying squirrel, farther to the north, so that the ranges of these two species now overlap more than they did in the past. A recent survey found that around four percent of flying squirrels in Ontario are now hybrids.

A southern flying squirrel

This is certainly not the first example of hybridization between species. The story cites the example of cross-breeding between grizzly bears and polar bears, which may also increase with the effects of global warming. But Bowman and other scientists believe that the flying squirrels are the first documented case of a hybrid species specifically caused by human-generated climate change. It is not clear what the long-term impact of hybridization might be for the flying squirrels or other species. Might a new flying squirrel species created by cross-breeding be better adapted to deal with a warmer climate? It's too soon to tell.

Help For the Mount Graham Red Squirrel?

The Mount Graham red squirrel has been listed as an endangered species since 1987, after having previously been thought extinct. It lives a precarious existence in a small area of Arizona, where it numbers only slightly above 200 individuals. Now it appears that a long-planned captive breeding program at the Phoenix Zoo may finally be nearing approval from the US Fish and Wildlife Service.

This small subspecies of the North American red squirrel lives in high-elevations conifer forests in the Pinaleno Mountains of Arizona, where it has been isolated from other red squirrels for over ten thousand years. Its numbers have declined due to habitat loss, drought and forest fires. In the 1990s this squirrel became controversial when conservation groups objected to the construction of a University of Arizona observatory in its territory, and since the construction the numbers of squirrels have been closely monitored.

The Phoenix Zoo captured four of the squirrels, two males and two females, in 2011 when it feared that wildfires that summer might devastate the remaining population. The two females died, but the males remain in captivity at the zoo. Zoo researchers have been learning everything that they can about these squirrels in the hopes of starting a captive breeding program to replenish the numbers, which are currently so low that the species could be exterminated by a single ecological disaster such as a forest fire or severe drought.

One of the captive male Mount Graham red squirrels

There are difficulties with any effort to breed Mount Graham red squirrels in captivity. The squirrels are extremely territorial, and will not tolerate the presence of other squirrels in their vicinity except for mating. The females of the species go into heat for only one day a year, so the timing has to be perfect. The zoo researchers are developing a guide for keeping the squirrels in captivity, which is being updated as they learn more.

The proposed pilot program calls for capturing a maximum of sixteen Mount Graham red squirrels over a period of ten years for captive breeding. After that ten years, a decision would be made based on results, on whether to launch a full breeding program. The Fish and Wildlife Service may approve the pilot program as early as this spring, although further delays are also possible.

The real question, of course, is whether the species can survive long enough to see the implementation of the program.

Squirrel Facts: The Golden-Mantled Ground Squirrel

The golden-mantled ground squirrel is a small ground squirrel of western Canada and the United States. It is found in southeastern British Columbia and Alberta, southward to New Mexico, Arizona, and southern California. Its primary habitat is hardwood forests, meadows, and sagebrush areas of the mountainous regions of the great basin, usually from above 4500 feet up to the timberline.

This is certainly one of the cutest of the squirrels. The golden-mantled ground squirrel resembles a chipmunk, with the two white stripes bordered by black stripes running down its sides. It is also chipmunk-like in size, just slightly larger, measuring only around ten inches long and weighing 6-7 ounces. Unlike chipmunks, this squirrel does not have stripes on its face.

Like other ground squirrels, golden-mantled ground squirrels hibernate through the winter, usually from October to May. They dig burrows deep under a protective object, such as a large rock or a log, and the burrow may stretch up to 100 feet long. These squirrels are not very social. Females and males appear together only during mating in the spring, after which they go their separate ways and the females raise their young alone.

The diet of the golden-mantled ground squirrel is varied, and includes seeds, nuts, fruits, and insects. The main food that they enjoy is pinon nuts. They also eat large amounts of underground fungi, which they locate by smell and dig out. When a golden-mantled ground squirrel locates food, it will eat some on the spot, then use its cheek pouches to carry the rest to the den, where it will be stored to eat in the spring when it wakes from hibernation. During the winter, these squirrels will sometimes awaken briefly to eat some of the stored food, then go back to sleep.

During the 1950s, a golden-mantled ground squirrel named Squeak was featured in a nature documentary. The short film shows Squeak, who lived at Crater Lake National Park, being put through a series of experiments to demonstrate the squirrel's intelligence and inventiveness at solving problems to obtain food that is hidden or out of reach.





I would like to thank Delilah the Squirrel on Facebook for bringing my attention to the above video.

Olney White Squirrel Population Dips

The town of Olney, Illinois has for decades been noted for its large population of white squirrels. There are competing stories of the origin of the squirrels, but the community has adopted them as a source of pride and a local tourist attraction. The city has set up squirrel crossing signs and has even  passed laws to protect the rodents by prohibiting cat owners from allowing their pets to roam free, and forbidding anyone from taking a white squirrel out of the city.

Unfortunately, over the years the white squirrel population has dropped steadily from a high of over 800 in 1941. And it seems that this decline may now be accelerating. Every year a local college conducts a white squirrel count, and this year's count, in October, found only 80 white squirrels in the town, a drop of about 25 percent from the previous year. While it is not clear that any single cause is entirely to blame, a city official has suggested that the extreme hot and dry weather of the past year could be a major factor.

Residents of the city are being encouraged to put out food and water for the squirrels, plant fruit and nut trees, put up squirrel houses, and to avoid cutting down existing trees during the season when baby squirrels are in their nests. Residents are also asked to obey squirrel crossing zones and laws prohibiting free-roaming cats and dogs.

Please help us!

Olney is one of a few places in North America that has a population of white squirrels. The News For Squirrels hopes that the residents of the town will do whatever it takes to protect this treasure.

(Just a note: both of the articles linked in this post mistakenly identify these squirrels as albino. These white squirrels are not true albinos, as you can see from the dark eyes in the photo above)

Ground Squirrels Give a Hand to Burrowing Owls

The San Diego Zoo is reporting on the initial success of a project to help restore populations of burrowing owls in San Diego county by introducing California ground squirrels to their territory.

Welcome to the neighborhood!

The small owls, along with other species, have declined in number largely due to the introduction of non-native grasses by ranchers. These grasses provide a thicker ground cover than the owls are adapted to. According to researcher Ron Swaisgood of the San Diego Zoo, it would be impossible to restore this habitat to its previous state. However, introducing California ground squirrels might help to recreate a similar habitat as the squirrels dig their burrows and open up the vegetation.

Hey, where am I?

This project is, of course, not without its challenges and setbacks. Many of the ground squirrels apparently don't like their new home and take off for surroundings more to their liking. Others become prey for hawks and coyotes. But the researchers do what they can to ease the squirrels into their new hood. They move groups of squirrels that already know each other together (the squirrels are taken from private land where they are not wanted); the squirrels spend the first week in an "acclimation chamber" getting used to the new area; then they are fed tasty treats for several months as incentive to stick around.

So far the program has had some success. At least some of the squirrels are digging burrows and setting up households. And the owls seem to be benefiting, as some have already moved into abandoned squirrel burrows. The research team is closely monitoring the squirrels after release, and hoping to learn how to better insure greater success in the future!

Squirrel Facts: Squirrels of the Desert

When most Americans think of squirrels, we think of the eastern gray, the familiar bushy-tailed tree squirrel of parks and suburban yards. But there are many different kinds of squirrels--over 300 species worldwide, and they live in almost every different kind of environment that we can imagine, from the tropics to the arctic. There are even squirrels that live in some of the harshest, most hot and arid deserts in the world.

Mohave Ground Squirrel, Mohave Desert, Southwestern US

Ground squirrels can be found living and thriving in two of the hottest, driest deserts of the world: the Mohave Desert of southwestern North America; and the Kalahari Desert of southern Africa. In both of these regions, daytime summer air temperatures can reach up to 114 degrees F, with surface soil temperatures as high as a blistering 140 degrees. Needless to say, animals that live in these places must evolve strategies to cope with such extreme conditions. The squirrels of these deserts have indeed developed some ingenious ways to survive.

Cape Ground Squirrels, Kalahari Desert, Southern Africa

One way that desert squirrels survive the heat is through a sort of reverse hibernation called aestivation. Just as ground squirrels and other mammals of cold arctic regions go into hibernation, some ground squirrels of the deserts will put on body fat, go into a burrow, and lower their heart, respiration, and metabolic rate, basically sleeping through some of the hottest months of the year. The Mohave ground squirrel, a rarely-seen ground squirrel of California, will aestivate from mid-summer through the fall, emerging in January or February. During the spring following a drought season, these ground squirrels might even skip mating and reproducing that year, and begin their aestivation as early as April.

Young Mohave Ground Squirrels

Squirrels of the desert also cope with the extreme heat by adjusting the times that they spend looking for food. Cape ground squirrels of the Kalahari desert will usually forage for food during the daytime during the cooler winter months. But in the summer, they will stay underground in their burrows during the hottest parts of the day, emerging to search for food only in the early morning and the late evening. These squirrels also store food in their burrows, so that they will have something to eat during those hottest periods.

When desert squirrels must forage for food in the heat of the midday sun, they can find ways to minimize their discomfort. Round-tailed ground squirrels, another species of the southwestern US, climb into bushes to forage, taking advantage of the shade and minimizing their contact with the hot sand. And the Cape ground squirrels, when they must go out into the daytime sun, use their bushy tails as "umbrellas" to give themselves some shade.

Round-Tailed Ground Squirrel, Southwestern US

It is not surprising that most or all of the squirrels of the deserts are ground squirrels, which live in burrows under the ground surface. Burrows are an extremely important part of the desert squirrels' survival strategy. For example, when measured over a period of a week, the daytime temperature outside reached over 100 degrees F and nighttime temperatures dropped as low as 23 F, but the temperature inside the burrow of the round-tailed ground squirrel stayed between 68-77 degrees F. Often when returning to the burrow after foraging in the hot sun, a squirrel will lie flat on its belly on the cool earth, or like the Mohave ground squirrel, will even dig into the ground, pushing its body through the cool soil, to help dissipate body heat and cool off.

Antelope Squirrel, Southwestern US

Desert ground squirrels have evolved several physical adaptations to cope with the hot and dry conditions in which they live. Some, like the antelope squirrel, are able to withstand higher body temperatures than most animals, even up to 110 degrees F; or, like the Townsend's ground squirrel, have a lower base body temperature, so that it can remain outside in the heat for a longer time before reaching a dangerously high temperature. Many desert ground squirrels have light-colored fur, reflecting the sun's rays, but dark skin pigmentation, which protects them from absorbing excess ultraviolet radiation.

Cape Ground Squirrel

Finally, desert-dwelling squirrels have evolved physical strategies to reduce their need for water. These adaptations include extremely efficient kidneys, reducing water loss through urination; and fewer mucus-producing cells in their lungs, reducing the amount of water lost through respiration. Because of these adaptations, many desert ground squirrels, like the antelope squirrel, can obtain most of the water that they need not through drinking but through the food that they eat.

Round-Tailed Ground Squirrel

Much of the information for this post came from the book Squirrels: The Animal Answer Guide, by Richard W. Thorington Jr. and Katie Ferrell. This book is an excellent source of information and a highly entertaining read for anyone interested in squirrels. If you are interested in this book, you can get a copy by clicking the link below.

Climate Change and the North American Red Squirrel

The American red squirrel, also known as the pine squirrel and the chickaree, is a medium-sized tree squirrel that inhabits much of the northern and eastern regions of North America, including most of Canada and the northeastern United States. Its diet consists largely of the seeds of conifer cones, although they also enjoy many other foods including conifer buds and needles, mushrooms, flowers, berries, and sometimes birds' eggs. Unlike the scatter-hoarding gray squirrel, the red squirrel stores food, primarily conifer cones, in a central location to provide food for the winter. The accumulated uneaten scraps from these food stores left behind by a red squirrel create a "midden" or trash pile that can measure as much as a meter in diameter.

Compared to the eastern gray squirrel, the American red squirrel is smaller but more aggressive in defending its territory. It is less likely to be seen in suburban yards and city parks, preferring wilderness areas more isolated from human activity. Also in contrast to the gray squirrel, the red squirrel will sometimes nest underground during the winter, although like other tree squirrels the red squirrel does not hibernate.

A recent study has examined the effects of global climate change on the feeding and mating habits of red squirrels over a period of several generations.

The authors of the study tagged and monitored the females of a population of approximately 325 red squirrels in the Yukon territory of Canada, from 1989-2001. During that period, the researchers kept track of the weather in the area, and monitored the feeding and reproductive habits of the squirrels. During the time of the study the mean spring temperature increased by 2 degrees Celsius. The production of the spruce cones that provide the squirrels' most important food source increased by 35 percent during the same period. And at the same time, the squirrels' breeding took place 18 days earlier by the end of the study period, advancing by about 6 days each generation.

The findings of this study seem on the surface to suggest that global warming has been beneficial to this population of squirrels. However, it is impossible to know what the long-term effects could be, both to the red squirrels and to other plant and animal species, and to the ecosystem as a whole. What seems to me most important about this research is the demonstration that climate change is having very real and demonstrable effects on the environment that has repercussions for the behavior of species. Much more long-term research is needed in this area.

Squirrel Facts: The Black Tailed Prairie Dog Needs Help

I have written about the black-tailed prairie dog before on this blog. Yesterday I created a petition on the Care2.com website to try to help this species by banning the use of two horrible poisons. Although I understand that the chances of success are slim, I want to do my part to raise awareness of the cruelties that are being inflicted on these animals. I am asking that you sign the petition and help spread the word.

This large ground squirrel of the grassy prairie and plains regions of North America lives in large colonies that can number in the hundreds or even thousands. Within their "towns" prairie dogs live in extended family groups or "coteries" consisting of several related females, their first-year young, and one or two males. Members of the coterie engage in mutual grooming, greet each other with "kisses" and hugs, and cooperate in activities such as caring for young and watching for and alerting others of potential danger.

Black-tailed prairie dogs live in burrows which can be amazingly complex. Each burrow may have multiple entrances, increasing the chance for escape from predators. The tunnels, marked by entrances ringed with a mound of dirt to help keep out water, may be up to five meters deep and 30 meters long. A burrow will usually be used by several generations of prairie dogs, and when abandoned may be taken over by other animals.

Unfortunately, the black-tailed prairie dog has been unfairly demonized by cattle ranchers and land developers. Ranchers believed, incorrectly, that the prairie dogs were taking food that was needed by their herds of cattle. This belief, which persists to this day, has let to the mass extermination of prairie dogs from their range. Today, after more than a century of slaughter by shooting and poisoning, the black-tailed prairie dog occupies less than two percent of its former range. Now, in addition to ranchers, new enemies including suburban land developers and even many city and town governments are carrying out a war of extermination against this sociable, intelligent ground squirrel.

The ranchers' war against the black-tailed prairie dog is based on a myth. The fact is, prairie dogs coexisted on the plains and prairies with massive herds of bison for thousands of years before cattle ranching took over the region. Bison and cattle require a very similar diet, and the prairie dog actually provides a benefit to the growth of the grasses that they eat. Their tunneling activity churns and mixes the soil and organic matter, and helps with water retention in the soil. Overgrazing by cattle does considerably more damage to the land than the presence of prairie dogs, and the activity of the prairie dogs may actually help to repair some of the damage done by the cattle.

Prairie dogs are also a vital component of the natural plains and prairie ecosystems. Ecologists refer to the black-tailed prairie dog as a "keystone" species. This is because a large number of other species are dependent on the prairie dog. They provide food for many predators including the American badger, bobcat, coyote, snakes, weasels, bald and golden eagles, hawks, and the critically endangered black-footed ferret, which has been driven to the brink of extinction by the extermination of the black-tailed prairie dog from its range. Many other animals, including snakes and burrowing owls, use abandoned prairie dog burrows for their homes. In all, at least 140 other species benefit from the presence of prairie dogs in their ranges.

Among the most lethal weapons in the arsenal of the enemies of the prairie dog are two poisons, Rozol (chlorophacinone) and Kaput-D (diphacinone). These two products have been approved by the EPA for use in ten states, in spite of the utter cruelty that they inflict on their victims and the widespread harm that they do to the environment.

These chemicals are blood thinners. When a prairie dog or other animal eats the poison, it experiences a slow, painful decline and death by internal bleeding that may take several weeks. During that time the prairie dog becomes weak and disoriented, making it easier prey for carnivores. After death the poison will remain in the carcass. Any animals that eats the meat will also consume the poison.

Several years ago the Environmental Protection Agency considered and rejected listing the black-tailed prairie dog as a threatened species under the Endangered Species Act. It has also given approval to the use of these two cruel, dangerous poisons. I believe that the EPA is negligent in carrying out its intended mission. I hope that you will help by signing the petition and take a stand for the prairie dogs.

If you would like more information on black-tailed prairie dogs and the threats that they are facing, you can read more here for general black-tailed prairie dog info, and here for more on the effects of Rozol and Kaput-D.

Senator Coburn Scapegoats Robo-Squirrel

Last spring I introduced readers to Robo-Squirrel, a biorobotic squirrel designed and built by researches at the University of California San Diego to study interactions between California ground squirrels and their biggest predator, the rattlesnake. Robo-Squirrel has helped research scientists and students at the university gain valuable insights into how the squirrels ward off attacks by the snakes using tail flagging and thermoregulation, or heating of the tail by adjusting blood flow.

Robo-Squirrel

Now Robo-Squirrel is under attack! US Senator Tom Coburn (R-Oklahomo) is using the robotic squirrel as an example of wasted federal tax money. The project that Robo-Squirrel was a part of was funded with a grand of $325,000 from the National Science Foundation, which is a federally funded agency. Apparently Senator Coburn thinks of any federal money spent on scientific research for anything other than new weapons for the military as being a waste.

Of course, I'm sure that the Senator was aware that the words "robotic squirrel" would get the attention of the press when he was looking for a project to scapegoat. I'm sure that nowhere in his press release did he mention the benefits of what this research has added to our knowledge of predator-prey interactions, of how species evolve adaptations to help them avoid becoming another species' dinner (but of course I'm sure the Senator, being a Republican, doesn't believe in evolution anyway).

And I'm also sure that Senator Coburn didn't mention that most of the grant money didn't go directly to the building of the robotic squirrel, but was instead used to fund the inclusion of both undergraduate and graduate students in the project. But then again, developing future scientists isn't something that the anti-science Republican party would be concerned with.

Some Random Squirrel Trivia For Squirrel Awareness Month

Since we're in the middle of Squirrel Awareness Month, and since I've been having a hard time coming up with new lines for the SAM carol (see my previous posts), I thought I'd offer up some interesting squirrel facts.

There are 278 species of squirrels in the world. They are native to every continent except Australia and Antarctica.

Squirrel species are grouped into three broad categories: ground squirrels (including chipmunks, marmots, and groundhogs); tree squirrels; and flying squirrels.

Gray squirrels have a bite force of around 7,000 pounds per square inch (psi). For comparison, most humans have a bite force around 500 psi.

Like other rodents, squirrels' incisors grow constantly throughout their lives. They must keep them worn down by gnawing to avoid having the teeth become impacted.

Squirrels cannot vomit.

Flying squirrels are able to glide between trees for distances of 150 yards or more. They do so using a flap of skin, called the patagium, that extends on each side of the body between the forearm and leg.

The word "squirrel" comes from two Greek words: skia meaning shade or shadow, and oura meaning tail.

The earliest squirrel known from the fossil record was protosciurus, which lived in North America around 37 million years ago.

Many ground squirrels hibernate during the cold winter months. However, tree squirrels do not hibernate. This is a common misconception.

Most adult tree squirrels, including the eastern gray squirrel, nest alone. However, in cold weather several squirrels will temporarily nest together to share body heat.

Squirrels can control the flow of blood to their tails. This helps the squirrel to regulate its body heat by altering the blood flow. It also helps ground squirrels defend against predators such as snakes that hunt by detecting heat, by allowing the squirrel to make itself look bigger and more threatening.

Squirrels' sweat glands are in the pads of their feet. On a hot day a squirrel may leave tiny wet footprints on a sidewalk.

Squirrels are diurnal, or awake and active during the day. Tree squirrels are most active early in the morning and late in the evening.

Gray squirrels often build more than one nest, or drey, especially when raising young. This way, if one nest is damaged or threatened by a predator, they will have a backup nest to move to.

Squirrels love pumpkins, and are adept at carving jack-o-lanterns.

Phew, that was hard work!

Before burying a nut, a gray squirrel will lick the nut to apply its scent to it. This helps the squirrel locate the nut later.

A gray squirrel weighing about a pound needs to eat its weight in nuts, seeds, and other food every week.

During hibernation, the body temperature of the arctic ground squirrel can drop to below freezing, as low as 27 degrees F. This is the lowest naturally occurring body temperature of any mammal.

Eastern gray squirrels, which are about 15 inches long, can jump up to six feet vertically and eight feet horizontally.

Prairie dogs live in "towns" that may contain dozens of family groups, and can cover hundreds of acres.

Rabies is virtually unknown in squirrels. There is no record of a human ever being infected with rabies through a squirrel bite.

Tree squirrels can rotate their hind feet 180 degrees at the ankles. This helps them to quickly and easily descend tree trunks head first.

A Brilliant Disguise: The Seventh Day of Squirrel Awareness Month

On the seventh day of Squirrel Awareness Month my squirrel love gave to me

Seven smelly snakeskins,

Six comfy dreys,

Five giant sweet peanut patties shaped like Texas,

Four cups of nuts,

Three Baby Ruth bars,

Two ice cream cones,

And an acorn in an oak tree!

California ground squirrels have an ingenious trick to fool one of their predators, the rattlesnake. When a ground squirrel comes across a shed snakeskin, it will rub the skin over its fur, coating itself with the snake's scent. This confuses any rattlesnake that threatens the squirrel and its young.

If a rattlesnake wanders into the area of a California ground squirrel colony, the squirrels will not wait for it to attack. They will go on the offensive against the snake, confronting it, kicking dirt at it, and waving their tails. These squirrels are even able to shunt extra blood to the veins in the tail, heating it up. Since the snake detects heat more effectively than it sees, this makes the squirrels appear larger and more threatening to the rattler.

Here is a video that demonstrates how effectively these little ground squirrels deal with a threatening rattlesnake:

The Drey: The Sixth Day of Squirrel Awareness Month

On the sixth day of Squirrel Awareness Month my squirrel love gave to me

Six comfy dreys,

Five giant sweet peanut patties shaped like Texas,

Four cups of nuts,

Three Baby Ruth bars,

Two ice cream cones,

And an acorn in an oak tree!

The drey, the familiar tree squirrel nest made of sticks and leaves, may look like a precariously constructed home. But squirrels are master builders, and the typical drey is not only secure but quite comfortable as well. A gray squirrel in her drey will be dry during rainy weather and well protected from the wind and cold. Here is what it looks like inside a typical drey:

Most squirrels, especially females with young, build multiple dreys within their territories. This way, if one drey is damaged, becomes infested with insects, or is threatened by a nearby predator, there is always at least one backup. A mother squirrel can move an entire litter of young from one drey to another within a few minutes. This is why you will often see more dreys than squirrels in a given area.

Fox Squirrel Caching Behavior

An interesting article from the UC Berkeley News Center discusses the strategies that fox squirrels use when caching nuts.

A group of students at the University of California, under the direction of psychology graduate student Mikel Delgado, have been tracking 70 campus fox squirrels, mapping their territories, and studying the strategies that the squirrels use to find, hide, and retrieve different kinds of nuts. The students hope to determine how the squirrels determine the quality of each nut, and decide what amount of investment to put into that nut, whether to discard, eat immediately, or to cache the nut.

Like the video in my previous post, this article confirms that tree squirrels rely on much more than just their sense of smell to locate hidden nuts. According to Delgado, the squirrels use a combination of landmarks and spatial memory to narrow down the location to a specific area, while probably relying on smell only for the "final bit of searching."

The article includes a cute video of some of the UC campus fox squirrels hiding nuts:

This looks like some extremely interesting research that promises to shed some light on the intelligence of our squirrely friends!

The Fourth Day of Squirrel Awareness Month

On the fourth day of Squirrel Awareness Month my squirrel love gave to me

Four cups of nuts,

Three Baby Ruth bars,

Two ice cream cones,

and an acorn in an oak tree!

Today's squirrel video demonstrates how tree squirrels use spatial memory to locate hidden nuts. The poster of the YouTube video experimented with three different squirrels, hiding nuts under one of four cups in a squirrely shell game. The squirrels always returned to the cup in the same position where they had previously found the nuts, even when the nuts were moved to a different cup, and even after a different colored cup had been substituted for the original.

The poster of the video makes one error in the description, saying that squirrels do not smell nuts but only locate them based on memory. Squirrels have an excellent sense of smell and most certainly can smell nuts. However, this video may demonstrate that squirrels rely more heavily on spatial memory when searching for recently-cached nuts or for food that they have recently found in a specific location.

I hope that after the experiment was ended, the squirrels were rewarded with all four cups filled with nuts!

Climate Change and The Belding's Ground Squirrel

Continuing on the topic of squirrels and global warming, a study just released by the University of California-Berkeley looks at how climate change is affecting the Belding's ground squirrel (note that this article discusses two studies; the study concerning the ground squirrels is covered in the second half of the article).

Hey, I think someone's talking about us!

The Belding's ground squirrel lives in mountainous areas of western North America. Its range covers parts of northern California, Oregon, Washington, Idaho and Nevada. This medium-sized squirrel prefers high meadows and brushy areas with an ample supply of vegetation and water. Related female squirrels live and interact together in colonies, while the adult males are nomadic.

Like most ground squirrels, Belding's ground squirrels hibernate through the cold winter months. The timing of the hibernation depends both on the altitude of the colony and the sex of the individual. As one might expect, squirrels living at higher elevations enter hibernation sooner than those at lower elevations. Also, males usually enter hibernation earlier than females. Related females often hibernate together, while males hibernate alone.

The study that I linked to at the beginning of this post looked at the movements of populations of the Belding's ground squirrel in response to global climate change. The authors of the study found that the squirrels had disappeared from more than forty percent of the areas that they had been recorded in the early part of the twentieth century. The disappearances were most common in higher-elevation areas that have experienced pronounced increases in temperature and rainfall in the past century. This finding was a surprise to the researchers, as the species has not been considered to be threatened and was in fact thought to be quite common. On the other hand, the Belding's ground squirrel has increased in some areas that have been modified by humans.

Although the Belding's ground squirrel is still not considered to be under serious thread, the unexpected declines demonstrate clearly how serious and complex an issue climate change is.

Climate Change and the Columbian Ground Squirrel

The Columbian ground squirrel is found in high meadows and grasslands of eastern British Columbia and western Alberta in Canada, and parts of Oregon, Washington, Idaho, and Montana in the United States. These ground squirrels live in colonies, spending four to five months of the year eating grasses, leaves, bulbs, fruits and seeds, and raising their litters of three to five young.

The other seven or eight months they spend hibernating. Each squirrel's burrow has a hibernation chamber. Columbian ground squirrels may begin hibernation in some areas as early as July. During the warm months, each squirrel puts on sufficient fat to survive the winter, and gathers seeds and bulbs in its burrow to eat when it wakes up. When hibernation begins the squirrel will seal the chamber with a plug of dirt. It will not emerge until the following spring.

Is it spring yet?

Now research is suggesting that global climate change is altering the hibernation patterns of the Columbian ground squirrel, with troubling implications. A team of scientists followed a group of female squirrels in Alberta over a period of twenty years. They have found that by 2011, the squirrels were emerging from hibernation an average of ten days later than at the beginning of the study.

The researches believe that the reason for the later emergence is a trend toward wetter, snowier winters in the region. They believe that the squirrels can detect the presence of snow cover from inside their hibernation chambers. Global warming is creating favorable conditions for later snowfall, and as a result the squirrels hibernate longer and emerge later.

The troubling aspect of this research is that with the longer hibernation, fewer of the ground squirrels are surviving the winter sleep. At the beginning of the project, twenty years ago, 87 percent of the female squirrels survived the winter hibernation. By 2011, only 67 percent of the females that entered hibernation emerged the following spring. The scientists aren't sure of the reason, but speculate that the shorter period above ground means that there is less time for the squirrels to put on the body fat required to survive the winter.

Whatever the reason, the fact is that fewer of these ground squirrels are surviving their winter hibernation, and this trend is not likely to reverse any time soon. It is one more piece of evidence of the damage that human-created climate change is doing to our planet.

Addition: Here is another, more detailed article about the Columbian ground squirrel study. It gives more information on the relationship between emerging later from hibernation and the increased failure of the squirrels to survive. It also gives a more complete explanation of the relationship between climate change (global warming) and increased late-winter and early-spring snowfall.