Cascadia Wildlife Blog
News from the Wolverine Tracking Project and more
Hibernation and Torpor explained!
There's no denying that winter can be rough- even for us! Colder temperatures, limited daylight and less food availability combine to make winter a challenging season for many of our animal friends. There are a lot of different strategies that have evolved for overcoming these winter woes! The PNW has a temperate climate, which means we have relatively mild winters but temperatures can still get pretty cold, especially on the mountain! Food is generally more scarce in the winter in this region and less daylight hours means less time spent foraging for most animals.
Animals evolved different strategies for dealing with winter based on a few different factors, notably, thermoregulation strategies and body size. Endothermic animals are animals that maintain their own internal body heat, as opposed to exothermic animals which rely on external conditions to regulate their body temperature. These two thermoregulation strategies are often colloquially referred to as warm-blooded and cold-blooded. Endothermic animals (mammals, birds and some fish!), have higher energy needs than do exothermic animals because of the energy demands of maintaining their body temperature. In the winter, when temperatures drop and food can be scarce, some endotherms are not able to obtain the amount of energy needed to maintain their internal body temperature and will use hibernation or torpor to conserve energy. Exotherms may also enter a period of reduced physiological activity, called brumation, at cold temperatures. Similar to hibernation, during brumation an exotherm's body temperature, heart rate, respiratory rate are significantly lowered.
Body size is also a factor in determining how an animal deals with winter weather. An animal's surface area to volume ratio determines how fast they lose heat; really small animals (like a squirrel or a hummingbird) have high surface area to volume ratios, which means they lose heat more rapidly than a larger animal (say a deer or bear) would. This means that smaller animals end up using more energy to maintain their body heat than larger animals that are able to retain more of their body heat. Which explains why lots of small mammals in cold climates resort to hibernation or periods of torpor during the winter!
How much body fat an animal is able to hold will also play a role in determining an animals winter survival plan! Animals that are able to hold a lot of fat on their body (like marmots) are able to hibernate for much longer than animals with limited fat stores.
In this post we are going to discuss who is hibernating right now in the PNW, explore the difference between hibernation and torpor, and try to unpack what the *heck* bears are doing in those dens all winter long!
Some endothermic animals hibernate over winter in response to cold temperatures and a lack of available food. Hibernation allows animals to conserve energy by lowering their body temperatures and metabolism. During this period, animals breath rate and heart rate slow down and they appear to be in a deep sleep. True hibernators are the animals that are unable to be woken up during this period, regardless of outside stimulus. True hibernators in the Pacific Northwest include yellow-bellied marmots, ground squirrels, bees, and some bats!
A yellow-bellied marmot soaking up some summer sun.
Marmots are extreme hibernators- they spend over half the year in hibernation! In Eastern Oregon, yellow-bellied marmots enter hibernation towards the end of July and emerge from hibernation in late February/ early March. If July seems a little early for a hibernation to begin, keep in mind that in this region, all the plants die back midsummer, so a lack of food availability spurs their early retreat! Those little bodies actually store a lot of fat, which is how they are able to hibernate for such long periods!
A golden-mantled ground squirrel running across a rocky landscape.
Golden-mantled ground squirrels are active from early spring to mid August, after which they hibernate for a period of 5-8 months. Unlike marmots, who subsist off of stored body fat, these ground squirrels have brief periods of activity during their long winter hibernation during which they will gorge on cached seeds.
A California ground squirrel caught in action!
California ground squirrels are facultative hibernators, meaning that they will hibernate if they experience cold or food stress but in warmer parts of their ranges are active year-round.
A bat darting through the night.
There are 15 bat species in Oregon! Some of these species migrate to escape the colder winter months, while others, such as the little brown myotis, hibernate in caves through the winter.
Torpor is another physiological mechanism for conserving energy which similarly involves a reduced body temperature and metabolic rate. The main differences between torpor and hibernation is that torpor is short term (hours, days or weeks), compared to months of hibernation, and animals can be easily roused from torpor, which is not the case for hibernating animals.
Animals that utilize torpor to help survive the winter months in the PNW include hummingbirds, chipmunks, skunks, badgers, deer mice! Hummingbirds often enter a state of torpor nightly, especially in colder climates. Since their surface area to volume ratio is so high, hummingbirds lose heat quickly and must eat almost constantly throughout the day to keep up with the demands of maintaining their body temperature, as well as the energy demands of flight. At night they enter a torpid state, lowering their body temperature, metabolism, heartbeat and respiration rate to conserve energy.
A striped skunk sniffing around!
Skunks will go into torpor when temperatures are particularly low, and food supplies are scarce, as a way to conserve energy. Since they are nocturnal, they go into torpor during the day!
An American badger moseying around in the woods.
Similarly, badgers will go into a state of torpor if temperatures are low. They are rarely seen above ground when temperatures are below freezing- preferring to stay in their dens in this dormant state.
A chipmunk perfectly perched in view of the trail camera.
Chipmunks typically spend the winter snuggled up in their burrows in a state of prolonged torpor- rising occasionally to snack on food they cached in the fall.
A little mouse making their way across a fallen branch.
Deer mice utilize a variety of strategies to keep their tiny bodies warm in the winter: huddling, nesting, and torpor. While huddling together or building a deep nest is likely enough for most deer mice to withstand Oregon's winter temperatures, if temperatures become too cold then they will resort to torpor.
So, What are Bears doing?
There has been a lot of debate over the years as to what the *heck* bears are doing all winter long! Many scientists have argued that bears are not true hibernators because their body temperatures do not lower to the same extremes as other true hibernators (marmots, ground squirrels) do. This means that they are more responsive during the denning period than a true hibernator would be. Some scientists now distinguish what bears do as super hibernation, because they do not eat, drink, defecate or urinate during the hibernation period. Other people take issue with that classification and believe that bears are actually in a long-term torpid state because they remain semi-alert and responsive throughout the season.
A bear taking a break!
Many black bears in Oregon don't retreat to their dens for periods of dormancy, anyways! Our temperate climate means that bears at lower elevations can find enough food throughout the winter to remain active.
Thank you for helping us exceed our fundraising goal!
The start of the new year also brings an end to our December fundraising campaign! We want to thank all of our members, and everyone who donated for making last months fundraising effort such a success! As a volunteer based, community centered non-profit, we are dependent on the support of all of you to keep Cascadia Wild running strong. Thank you for showing up for Cascadia Wild last month, and all year long! 2021 was another challenging year in many respects, and we remain forever grateful for this community and all that we are capable of together!
With your help, and the help of our generous board members and local businesses who donated, we raised $3,900. That accounts for over 10% of our annual budget! Your donations help us to keep teaching naturalist classes, hosting nature-based clubs, and running the Wolverine Tracking Project!
Brrrr, the PNW ended 2021 with chilling temperatures, icy roads and lots of snow! These conditions have kept our Wolverine Tracking Project volunteers on their toes, as they bundle up and head to the mountain to maintain cameras and survey tracking transects, facing all sorts of unexpected challenges along the way. After the massive amount of snow Mt.Hood has received in the past few weeks, snow shovels are a must for many camera sites, as volunteers have been digging out buried cameras and replacing them above the snow line. Tree branches (and even trees sometimes!) can be brought down by the weight of the snow, and sometimes end up obscuring camera views. Our capable volunteers have been moving cameras and removing branches to make sure that the WTP cameras don't miss a thing!
Lots of winter snow can certainly add some difficulty to volunteers jobs, but it also makes for excellent tracking conditions and beautiful scenery! The mountain is truly a majestic and awe-inspiring place to be this time of year, just look at this stunning picture taken by one of our volunteers on a camera check recently!
One of the coolest things about monitoring wildlife on Mount Hood is that you never know what you are going to find! We had some predictable detections on our cameras over the last month- our regular forest friends ( bobcats, coyotes, deer, squirrel, etc), as well as some mystery detections that we are still working on identifying! The same can be true for tracking- by now most of our volunteers are familiar with the sight of a Douglas squirrel track bounding through the snow, but some tracks can be tricky! It's all part of the fun!
Below are some of the highlights of our WTP findings over the last month! Keep scrolling to the bottom of this post if you want to see some of the photos that we have been puzzling over.
Camera And Tracking Surveys
One of the most intense wildlife interactions ever documented on our trail cameras was this scene capturing both a buck and a coyote running through the forest!
An intense scene unfolds in the forest!
The buck is seen running through the clearing, pausing and staring at the camera for a second, and then taking off again. This made us wonder if perhaps the sound or the flash of the camera startled the buck, and caused it to pause. A coyote charges through the scene right after the buck and then doubles back to sniff at the bait log at the camera site. Was the coyote chasing the buck? Were they both running from something that startled them? Was this just a strange coincidence? We can't know for sure but it sure is fun to speculate!
Below are more coyote detections from the past month! Coyotes are a common sight at our camera sites- we often capture footage of them sniffing around and marking near the bait box.
From top to bottom: A coyote strolls up to a bait box to give it a whiff-if you look closely you will see their companion in the top left corner; A excited coyote runs up to the bait box and circles it, showing us a little upward dog stretch in the process; A beautiful coyote sniffing around a frequently marked spot at a camera site.
Our next detection is extra exciting because its a first for this season! This elusive feline goes by many names- cougar, mountain lion, puma, panther, and a personal favorite: mountain screamer! Cougars are a rare sight, not because they aren't around, but because they are very shy.
A mountain lion passing through, pauses to check out the bait tree before moving on.
The other feline found in our region are cougars slightly smaller relative- bobcats! We capture bobcats pretty frequently on our trail cameras, and their tracks can be a common sight in the snow at some of our camera locations!
From the top: A bobcat crosses over a log; a bobcat strolls through a camera site; two bobcats traveling together are seen walking towards the camera.
There were not very many black bear sightings this month, which is no surprise since many of the bears at higher elevations will have settled into their dens by now. We expect to continue to see some black bear activity throughout the winter, particularly at lower elevation camera sites.
A black bear strolls through a camera site, and then circles back to sniff around some more.
Carnivores come in all shapes and sizes! One of the smaller carnivores in our region is the weasel. There are both short-tailed and long-tailed weasels in Oregon. These species can be hard to distinguish, typically long-tailed weasels are the bigger of the two, however both species are sexually dimorphic, so there is some overlap in size of a small female long-tailed weasel and a large male short-tailed weasel. Both species turn white in the winter!
A weasel scampers around the base of a bait log tree.
Deer are another common species detected on our wildlife cameras. Deer social groupings can shift throughout the seasons, although females are usually found traveling with their young year-round. They may travel with other females and juveniles to form small herds. Males are often solitary through the winter but may travel together in small bachelor herds in the spring and summer.
From the top: a deer crosses through a dusting of snow; two male deer are detected traveling together; a deer walks through the snow.
In the second photo two male deer were spotted traveling together! While it may be less common for two male deer to pair up in the winter, it's clearly not out of the question!
Deer scat photographed by one of our volunteers.
Now on to some of our smaller forest friends. Below you can just make out a snowshoe hare bounding through the snow- look for the flash of their eyes on the right hand side. More visible are the tracks left behind! Snowshoe hare tracks in the snow often leave a distinct trail pattern that resembles a T.
From the top: A rabbit seen hoping through the snow, as more snow falls; a clearly defined rabbit track from a recent tracking survey.
Squirrels are another of our smaller mammalian forest friends that remain relatively abundant throughout the winter. While the ground squirrels are staying cozy hibernating, Douglas squirrels and Western gray squirrels remain hard at work throughout the winter.
From the top: A Douglas squirrel perches in a tree; a Western gray squirrel scampers across a log; a Douglas squirrel bounds through the snow; squirrel tracks in the snow photographed on a recent group tracking survey.
Our smallest visitor this month was another adorable rodent- a little mouse! If you look closely at the picture below, you can see their little eyes shinning inside the bait box!
A mouse hanging out in the bait box.
Who goes there?! Below are some of the recent wildlife findings that we have not been able to identify. Ah, the thrill of a good mystery! There may not be enough information in these photos to properly identify these creatures, but boy do we love to speculate! Be sure to comment or send us a message at email@example.com if you get a hunch about who we are looking at here!
From the top: A mystery mammal hops across a log before sitting and staring towards the camera; an unknown shadowy creature crosses a clearly; tracks in the snow in front of a trail camera- but there's no animal to be seen.
P.S. A trusted informant proposed that the tracks in the bottom photo may belong to a grouse, based on how short the stride is relative to the size of the track. Let us know if you agree!
Winter is coming!
The winter Solstice is right around the corner, but with the storms and snow of the last week it certainly feels as though winter has already arrived here in the Pacific Northwest. Our winter wildlife surveys are in full swing, volunteers on our tracking and camera crews are busting out their snow shoes and puffy jackets and braving the elements to bring us some amazing wildlife findings!
This winter Cascadia Wild is partnering with ODFW to take part in the Western States Wolverine Occupancy Survey! This multi-state, multi-agency survey effort aims to determine the current distribution of wolverines in the western United States. Cascadia Wild is honored to be participating in this survey, the results of which will undoubtably have important implications for the future management and conservation of wolverines. Who knows, this could even be the year wolverines return to Oregon!
With the coming of winter, we expect to see some behavioral changes in many of the wildlife species found on Mount Hood. For example, deer tend to move to lower elevations in search of better foraging opportunities. Often times this results in the movement of larger predators that prey upon deer, such as coyotes and mountain lions, to lower elevations as well. In addition to the movement of deer and some predators, we also typically see less bears at our higher elevation sites, as they hunker down for a deep sleep over the winter. At lower elevations where the winter is not as extreme, bears can be active all winter.
We are excited to share the best of our winter camera and tracking surveys so far! Without further ado, let's get into it!
Perhaps our most unusual finding over the last month was this owl and deer interaction captured on one of our trail cameras!
An owl crouched on the forest floor is disturbed by a passing buck.
We don't often get trail camera footage of owls, and certainly not ones that are this clear. Trail cameras give us this amazing opportunity to peak into the lives of wildlife living in the forests nearby- we feel extra lucky to have witnessed this interspecies interaction!
We had a lot of other deer detections this month- at sites across the elevation gradient on Mount Hood. This will likely change as snow begins to accumulate at higher elevations! In addition to the changes in deer distribution during the winter months, deers diet will also change. In the summer deer mainly subsist on grasses and forbs (herbaceous flowering plants) but in the winter will begin to rely more heavily on woody plants.
From the top: A young deer with small budding antlers looks into the camera;Three deer are seen foraging in an open meadow; a buck with a large rack pauses in the middle of the camera site.
We also had a few detections of elk this month. Elk cows and calves move together in large herds through the winter, while bulls are more likely to strike out on their own after the breeding season.
An elk herd comes barreling through a camera site!
Elk belong to the same family as deer (Cervidae), they are both hoofed, ruminant mammals. Ruminants are hoofed herbivores that have four compartments in their stomachs! In one of these compartments -the rumen- plant material is fermented by symbiotic microbes. Plant cell walls are made up of cellulose, which can't be digested without the assistance of these little gut microbes! After being processed in the rumen and reticulum, food is regurgitated as cud and then re-digested. This time it will pass through all 4 compartments and be excreted as poop! Speaking of elk poop *ahem* scat, as those of us in the tracking field like to call it- check out this picture of elk scat our trackers found on a recent survey!
Scat found on a recent tracking survey, likely from an elk.
A recent tracking survey also found what is likely coyote scat!
Coyotes are opportunistic omnivores- they will eat berries, fungi, insects, fish, small mammals and fawns, depending on what is available. Our trackers weren't able to find the plant that produced these berries in the field but did some serious sleuthing back at home and determined that they likely belonged to the Arctostaphylos genus.
We also had several coyote detections on our trail cameras over the past month!
From the top: Two curious coyotes sniff around a baited log at night; a coyote checks out a camera site; a coyote gives a bait box on a tree a quick sniff.
Coyotes weren't the only large carnivores we spotted in the forest this month. We also had bobcat and bear detections at several sites.
Bobcats consume mostly small mammals such a snowshoe hare, rabbits and squirrels. Their diet remains fairly consistent throughout the year.
A bobcat on the prowl!
Black bears, the only bear found in Oregon, are considered to be the "least carnivorous" of the large carnivores. Black bears eat berries, fruit, herbaceous vegetation, insects and occasionally fawns or carrion. Black bears typically gorge themselves during the fall (eating up to 20,000 calories a day!) and then live off their fat reserves during their winter dormancy.
From the top: A black bear gets groovy rubbing up against a tree; A black bear stares into the camera; Two bears, a mama and her cub, come padding through the forest.
The smallest of the carnivores we spotted this month was this little weasel!
A weasel bounds through a camera site.
We have both short tailed and long tailed weasels in Oregon. Both are carnivorous, but short-tailed weasels dine primarily on mouse-sized prey, while long tailed weasels hunt slightly larger prey, such as ground squirrels or mountain beavers.
Speaking of squirrels! We saw lots of squirrels at our camera sites this past month. Ground squirrels are most likely snuggled up enjoying a cozy hibernation by now. However we saw plenty of Western gray squirrels, Douglas squirrels and even some Northern flying squirrels, all of which will remain active throughout the winter.
From the top: A Western gray squirrel sniffing at a bait log; A Douglas squirrel carrying a big cone; A Northern flying squirrel scampering across the forest floor.
One of our camera crews also spotted some beautiful squirrel tracks in the snow!
Squirrel tracks in the snow.
That's all we have to share with you this month but we will be back in the new year with more wildlife findings! We wish all of you a joyous holiday season and a happy New Year!