Denning

Wet, cold and dark induce dreamy illusions as a storm envelopes Long Ridge.

Denning - a personal definition - reluctance to leave the lair; the time of year when wet, dark and cold conditions cause a shift towards low metabolic activities:  reading, writing, searching for thermal underwear and down comforter, mending, walnut-cracking while watching movies, sleeping, thinking about but not actually waterproofing boots, dreaming of a functional woodstove, baking, and more reading this time with a cat sitting in lap.


The season of glorious clouds has been superseded by the wet season with increasing periods of cold and darkness.  Morningside, I argue with myself in the hot shower, "See you are waterproof.  Get going!"  Instead, I find lion faces in the fake marble patterns of the cheap shower walls and the daylight just gets shorter.

Planting wetland plants along the edge of a future red-legged frog pond.
We don't usually pen in our volunteers - the orange construction fence is to temporarily keep the cattle out.

We finished 8 hectic weeks of planting over 1000 forest and pond plants.  Many of those days were wet which didn't bother me at the time because we had a mission with a looming deadline and the clouds were grand.  Looking down -  recently softened and plantable soil.  Looking up - raindrops polishing bright green leaves.  Looking inside - tired from walking up slopes and being in charge.  Looking out - exuberant plants exhaling reawakened energy into our airstream.

Little plants to start a forest.

In coastal California, many native plants follow annual wet/dry cycles.  Native perennial plants undertake a growing spurt in the fall even before the rains start.  My guess is that at some critical point, the shorter fall days result in less transpiration and therefore greater availability of moisture in the soil that stimulates the perennial natives to sprout new growth especially underground.  We try to mimic that pattern by installing our restoration plants in the fall months of September, October and November with the expectation that for a few weeks their roots will grow into the surrounding native soil before becoming dormant for the winter.  Then they are better situated to quickly take advantage of the moist and warm growing conditions in spring before the rains stop in May or June.

Lupine cotyledons are kidney-shaped and reticulated.

On October 30th, as we were planting another stand of young madrone trees, toyon, coffeeberry, California rose, monkeyflower shrubs and acorns, the rain was soaking the coats of seeds we had spread and covered with straw in September.  The soaking stimulated germination and by that October afternoon, we could see lupine, poppy and bunchgrass seedlings popping out of the ground besides our caked elbows and knees.

Freshly hatched California poppy plants.

Torpor - sluggishness or inactivity with body temperature usually below body temperature when same organism is active.  Winter-induced torpor is commonly referred to as hibernation.  Some animals become torpid during extremely hot temperatures and this is called estivation.

Usually when I'm outside in the fall and winter months, I'm working and/or hiking and expend enough energy to stay warm.  Sometimes, I end up with a thin layer of mud smeared on my clothes from knees to toes and elbows to fingertips.  Body heat dries the layer of mud and it forms an insulating layer (and later a laundry headache).  If you get too soaked, however, your fingers swell up and skin gets soft, your hands slip on tools, and it is hard to walk on steep slopes without sliding.  Your body can lose a lot of heat if your skin and clinging clothes are constantly wet.  You are a two-legged version of a water-logged earthworm.

Mud - a badge of honor.

Proper clothing makes it feasible to work in the rain on cool days.  I put most of my field faith in a good hat with a wide enough brim to keep the raindrops off my glasses and from dripping down my neck.  And SmartWool socks that keep my feet cozy warm even if they are wet.  When it comes to raingear, the right compromise between water repellency and venting is paramount for a winter biologist.  I have six raincoats for the ranges between warm-wet and cold-wet, and dripping and pouring-windy (and because I just can't throw an old raincoat away).

Still, as it gets colder and darker and wetter, pit zips aren't enough to get me outside every day.

Hibernate - to pass the winter in a dormant state usually accompanied by lower body temperature, slower breathing and heart rate, and a lower metabolic rate.

Dark cold sunset on November 21.

Generally, mammals hibernate to survive a cold period when the food supply is limited. Their "long sleep" in a sheltered location requires less energy than active foraging or hunting and compensating for the cold temperatures.  They survive on a cellular level by digesting body fat, or the groggy organism may awaken for brief periods during the winter to eat from a previously stashed larder, urinate and refluff the nest.  They ease into hibernation by slowing down their activities gradually, and likewise, they can be slow to rewake.

Are there mammals that hibernate in the mild winter climate of the Santa Cruz Mountains?  With an annual average of only 10 days that fall below freezing, the winter is not as challenging here.  The coastal hills green up with grasses in the pelter of California's winter rains, and this becomes food for grazing animals of all sizes from cattle to mice.

Sneaking around on a drippy December day, coyotes are still active in the winter.
Most carnivores do not hibernate.

I know the following mammals don't hibernate in the Santa Cruz Mountain winters, because I see them foraging or traveling in the winter months:  black-tailed deer, coyote, bobcat, mountain lion, raccoon, brush rabbit, long-tailed weasel, deer mouse, and western grey squirrel.  But what about mammals we don't regular see, especially those that are nocturnal?  I was not able to find any published information specific to the local area, but after consulting with a statewide guide and some local wildlife biologists, here are a few educated guesses.

Most bats that remain in the Santa Cruz Mountains for the winter probably hibernate. Merriam's chipmunks are listed as hibernating throughout the state.  Spotted and striped skunks may remain in their dens during periods of inclement winter weather.  California and San Joaquin pocket mice show reduced activity above ground during winter cold spells.  California ground squirrels may become torpid during cold temperatures at high elevations and during late summer in hot areas, especially when food is scarce, but I couldn't find any specific information about our area.  Not many animals actually hibernate here.  Maybe they have other strategies for dealing with the wet, modest cold and dark.

Last week between rainstorms, I hustled outside to move everything off the porch.  The porch is slowly falling downhill and dragging the house with it, so we are tearing it off.  Another rainy season construction project, go figure.  I folded up the chairs, table and kitty toys on the porch and carted them to the barn for storage.  As I walked in and out of the vacant barn, the wind was slapping the heavy hanging doors, rain was falling on the vacuous roof, and the walnut branches were scratching the eaves. Among all that noise and my labored breathing, I kept hearing voices, "I know it's in here somewhere."  And, "Never throw anything away."  The ghosts of the former Dipper Ranch residents tend to visit me when I'm struggling to get something done inside of one of the creaky buildings.

On December 12, four bucks in a line ran past the maple trees I was reading under.
The lead 2 x 2 buck had his tongue hanging out.
I couldn't see anything that was chasing them or that they were pursuing,
but they were definitely not winter lethargic.
Even-toed hoofed animals (Order Artiodactyla - deer, pronghorn, elk, moose,
sheep, goats, pigs, bison) do not hibernate.

What surprised me most that day, however, was the voice I heard in the yard under the persimmon tree as I paused to watch another band of dark clouds roll in over Long Ridge. "Even an old broad like you should wear proper undergarments when working around the menfolk."  Someone's got some opinions, and those opinions did not stop upon their "long sleep".  When I'm fixing things around the place - holding up my obligation to the old-fashioned rural work ethic - I figure I've got the right to mostly ignore those old-timey voices, at least until I fall asleep and they come back to me for crepuscular contemplation.

Brumation - reptiles in a winter state of inactivity usually spent in a protected den or other type of hibernaculum.  During brumation, reptiles usually do not eat, may drink, are not in a deep unconscious sleep as are mammals, and their body temperature is similar to their surroundings (but that is what reptiles do year round anyway).  Some scientists dispute the need for another term to describe winter sheltering by reptiles.

I'm fairly certain snakes spend the winter under the barn floor boards because I see them lingering about the barn on those warm days between the first cool fall days, and on the first consecutive hot days in early summer.  When the barn speaks, I wonder how much of the voice is tempered by those slow reptilian brains underfoot.

Winter lethargy - Walking hibernation - Carnivorean lethargy - more hibernation terms to describe the different winter metabolic processes undertaken by bears but since bears no longer live in the Santa Cruz Mountains, you'll have to go to the link.

With the winter solstice and a lunar eclipse tonight, look around you at the slowed pace of life.  How do you see your human companions responding?  Where might they stand on the spectrum of strategies to deal with the wet, dark and cold conditions of wintertime?  Humans have a greater ability to deal with these limitations, but still, I bet you will find some that are hibernating, brumating, torpid, winter lethargic or germinating.  I'm giving myself until mid-January to test the limits of denning behavior.

My hobbit neighbors in Devil's Canyon
bedding down for a cold, wet night.

See also:

Wild Mammals of North America:  Biology, Management, and Conservation.  George A. Feldhamer, Bruce C. Thompson, Joseph A. Chapman, editors.  2nd edition.  John Hopkins University Press.

California's Wildlife. Vol. I-III. D.C. Zeiner, W.F.Laudenslayer, Jr., K.E. Mayer, and M. White, eds. 1988-1990. California Department of Fish and Game, Sacramento, California.  [Bookmark the link on this one folks, it is very handy.]

Climate data from Western Regional Climate Center, Skyline Ridge Open Space Preserve, 1995-2010.

Thanks also to W.D. Padley, S. Abbors and G. Basson for their personal field observations in the San Francisco Bay region.