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Huddling for Warmth

Beaver in snow, Courtesy US FWS
Beaver in snow
Image Courtesy US FWS

When temperatures dip below freezing and wind hurries on its way, we often find ourselves looking for another warm body to huddle near and share heat. Children snuggle into laps and dogs lean close.

Many animals huddle to stave off the cold. Species that are strong individualists in balmy seasons seek warmth from a group when temperatures drop. Many non-colonial rodents will share a den come winter.

[Kevin Colver recording: Songbirds of the Southwest Canyon Country]

Pygmy nuthatches jam themselves tightly together into tree cavities as do flying squirrels. Through the winter, worker honeybees huddle tightly around a central patch of wax comb where developing larvae are growing. The larvae die if temperatures drop below 83 degrees, so a living blanket of worker bees shivers to generate the heat equivalent to a 40 watt incandescent bulb.

An animal loses heat in direct proportion to its surface area. By huddling together, each animal reduces its exposed surface area. This in turn allows them to reduce their metabolic rate and so conserve energy at a time when food can be scarce or inaccessible.

Nests or dens occupied by numerous individuals can be much warmer than ambient. A snow covered lodge with at least 2 beaver occupants can be as much as 35 degrees warmer than the outside air temperature. A study of taiga voles showed that underground nests containing 5 to 10 residents remained 7 to 12 degrees warmer than the surrounding soil and up to 25 degrees warmer than the air above. Individuals take turns going out to forage so their nest remains toasty.

Living in close proximity does have its problems. Disease and parasites are readily transmitted in tight quarters. Local food competition could potentially lead to hunger or starvation. Predators may more easily discover prey in groups. But for many animals, the advantages of huddling for warmth far outweigh the risks during our chilly winter months.

This is Linda Kervin for Bridgerland Audubon Society.
Credits:

Photos: Courtesy US FWS

Audio: Courtesy Kevin Colver, https://wildstore.wildsanctuary.com/collections/special-collections, https://wildstore.wildsanctuary.com/collections/special-collections

Text: Linda Kervin, Bridgerland Audubon Society
Additional Reading:

Life in the Cold: An Introduction to Winter Ecology. Peter Marchand. 1991, University Press of New England. https://www.amazon.com/Life-Cold-Introduction-Winter-Ecology/dp/0874517850

Lives of North American Birds. Kenn Kaufman. 1996, Houghton Mifflin Company. https://www.amazon.com/American-Peterson-Natural-History-Companions/dp/0395770173

The Birder’s Handbook. Paul R. Ehrlich, David S. Dobkin and Darryl Wheye. 1988, Simon & Schuster, Inc. https://www.amazon.com/Birders-Handbook-American-including-Regularly/dp/1435277589

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Utah, the Red State

Utah, the Red State
Chinese Wall at Bryce Canyon National Park
Courtesy National Parks Service
Hi, I’m Holly Strand for Wild About Utah

Straddling the four corners region is a massive geologic province known as the Colorado Plateau. Varying from 5 to 10,000 feet in elevation the region covers an area even larger than Utah, and is composed of thick horizontal layers of sedimentary rock. Wind and water have whittled Plateau rock into dramatic cliffs and steps as well as fanciful domes, towers, turrets, and arches. A predominance of red bed deposits in the central area of the Plateau has prompted the nickname “red rock country.”

So what’s behind these spectacular red hues? The color of rock is primarily influenced by trace minerals. The red, brown, and yellow colors so prevalent here result from the presence of oxidized iron–that is iron that has undergone a chemical reaction upon exposure to air or oxygenated water. The iron oxides released from this process form a coating on the surface of the rock or rock grains containing the iron.

Utah, the Red State: Entrada sandstone is responsible for some of the reddish rock found in Arches National Park. Photo Courtesy USGS
Entrada sandstone is responsible
for some of the reddish rock found
in Arches National Park.
Courtesy USGS

Just think of what happens to a nail when you leave it outside. Upon prolonged exposure, the iron in the nail oxidizes and rust is formed as a coating on the surface of the nail. So basically what we have in red rock country is a lot of rusting sandstones and shales. Hematite is an especially common mineral form of iron oxide in Utah, the name coming from the Greek word “heama” or red blood. It only takes a tiny bit of hematite make a lot of red rock.

Certain rock formations in Utah are particularly well-known for their beautiful reddish colors. The Permian Period gave us Organ Rock shale which caps the buttes and pinnacles of Monument Valley. The deep ruddy browns of the Moenkopi formation were formed in the Triassic. In the early Jurassic, eastern Utah was a vast sea of sand with wind-blown dunes. These dunes became the red bed deposits of the Wingate Formation which today forms massive vertical cliffs. Entrada sandstone, from the late Jurassic, forms the spectacular red, slickrock around Moab.

Reddish brown Moenkopi Formation in Capitol Reef National Park, Photo Courtesy USGS
Reddish brown Moenkopi Formation
in Capitol Reef National Park.
Courtesy USGS

So now you know what I’m thinking of when I hear Utah referred to as a Red State. I’m picturing the extraordinary splendor of the red, orange and rust- brown rocks that help to form the massive geologic layer cake in the south and east of our state.

For Wild About Utah I’m Holly Strand.

Utah, the Red State-Credits:

Photos: Courtesy National Park Service, https://www.nps.gov/brca/ and

United States Geological Survey (USGS), https://www.usgs.gov/

Text & Voice: Holly Strand

Utah, the Red State-Additional Reading:

Discover additional Wild About Utah pieces authored and voiced by Holly Strand, https://wildaboututah.org/author/holly-strand/

Chan,Marjorie A. and William T. Parry Rainbow of Rocks . Public Information Series 77. Utah Geological Survey. https://ugspub.nr.utah.gov/publications/public_information/pi-77.pdf [Accessed August 2025]

Geology Underfoot in Southern Utah by Richard L. Orndorff, Robert W. Wieder, and David G. Futey, Missoula, MT Mountain Press Publishing Company, 2006, https://mountain-press.com/products/geology-underfoot-in-southern-utah

Chronic, Halka. Roadside Geology of Utah. Missoula, MT Mountain Press Publishing Company, 1990 https://mountain-press.com/products/roadside-geology-utah

Fillmore, Robert, The Geology of the Parks, Monuments and Wildlands of Southern Utah, University of Utah Press, 2000, https://uofupress.com/books/geology-of-parks-monuments-and-wildlands-of-southern-utah/

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Sleeping Winter Away

Yellow-bellied marmots,
one of Utah’s true hibernators
Photo courtesy Utah Division of Wildlife Resources,
Copyright Lynn Chamberlain

As Utah’s blanket of snow grows thicker and cold temperatures set in, some of our furred friends quietly retire for the winter. Gone are the marmots that basked on sunny slopes, the bears that browsed in the forests, and the bats that winged silently overhead.

Animals have a number of different strategies to help them survive in winter. Some, such as hummingbirds, migrate to a more temperate climate. Some have special adaptations that allow them to withstand cold temperatures such as mink, which grow wonderfully thick winter coats. And some, such as marmots, bears, and bats, simply find a cozy place to sleep away the winter.

The general term for this period of inactivity is “dormancy,” which includes more specific terms such as “hibernation” and “torpor.” During this time, an animal’s heart rate, breathing rate and metabolism slows down considerably. Contrary to popular belief, most of the mammals that hole up for the winter do not actually hibernate. The term hibernation applies to only a small portion of our Utah mammals – a few species of bats and some rodents like the marmot. True hibernation means that an animal’s metabolism turns off to the point that its body temperature nearly matches that of the environment around it. And in winter, this means that body temperatures can drop to nearly freezing. Hibernating animals become unresponsive to environmental stimuli such as loud noises and being touched, and it takes hours and lots of energy for them to finally awaken.

A black bear,
which survives winter
in a state called torpor
Photo courtesy Utah Division of Wildlife Resources,
Copyright Lynn Chamberlain

In contrast, consider the bear, which does not technically hibernate, but instead enters a state called torpor or ‘winter lethargy’. A bear’s body temperature does decrease during this time but never approaches freezing. Bears also remain semi-active occasionally moving about in their dens, or even giving birth and tending to their newborns. Other animals that become largely inactive in winter but do not fully hibernate include skunks, raccoons, and opossums. These animals can respond very well to environmental stimuli and can resume their full abilities in less than a minute if disturbed – something to keep in mind in case you stumble across a bear’s den this winter.

Thanks to the Rocky Mountain Power Foundation for supporting research and development of this Wild About Utah topic. For the Stokes Nature Center and Wild About Utah, this is Andrea Liberatore.

Credits:

Photos: Courtesy Utah Division of Wildlife Resources and Copyright Lynn Chamberlain, photographer

Text: Andrea Liberatore, Stokes Nature Center

Additional Reading:

Encyclopædia Britannica. 2010. “Dormancy.” Encyclopædia Britannica Online. https://www.britannica.com/EBchecked/topic/169514/dormancy (Accessed Nov. 20, 2010)

New Jersey Division of Fish and Wildlife. 2010. Black Bear Biology and Behavior. https://www.state.nj.us/dep/fgw/bearfacts_biology.htm (Accessed Nov. 20, 2010)

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Gall Insects

Rabbit Brush Galls
made by a tephritid fly Aciurina trixa
Image courtesy and Copyright Jim Cane
Fly identification courtesy Gary Dodson

Does Utah have more Gauls than Caesar conquered? Certainly not Gaulish peoples of the ancient Roman Empire, but yes, galls of the vegetal kind we have aplenty. Galls are small protuberant growths on plants that are induced hormonally by insects, nematodes, and microbes. For its resident juvenile insect, the gall is a sort of edible fortress.

Some plant galls made by insects persist into winter, when they are more apparent to the naturalist’s eye. Looking at just rabbitbrush, you can find a menagerie of galls shaped like peas, pineapples and spindles that were formed from leaves, buds and stems. No growing tissue is immune to galling. The morphology of a gall is often diagnostic for the species of juvenile insect within. Gall-making insects are all tiny and include gall midges and tephritid flies, cynipid gall wasps, various nondescript moths, and any number of aphids and their kin.

One aphid causes the unsightly brown galls on branch tips of blue spruce, a bane to homeowners. Another aphid forms the pea-shaped galls that swell leaf petioles of aspens and cottonwoods. On sagebrush can be found a leaf gall whose soft surface surpasses that of a puppy’s ear. Oaks and willows host a remarkable diversity of galls. One oak gall was formerly used for tanning leather and making inks because it is rich in tannic acids. The Hessian fly is of grave agricultural importance today because its stem galls weaken wheat stems, causing them to lodge over.

Tephritid fly Aciurina bigeloviae
galls on Rabbitbrush
Image courtesy and Copyright Jim Cane
Fly identification courtesy Gary Dodson

But these are exceptions; most galls are of little or no ecological or economic importance. For that reason, most galling insects remain understudied by all but a handful of passionate specialists. Finding plant galls is easy, and once you begin to notice them, you will find it hard to stop. There is no guide to Utah’s plant galls, but we list several starting references for you on our web site.

This is Linda Kervin for Bridgerland Audubon Society.

Credits:

Theme: Courtesy & Copyright Don Anderson as performed by Leaping Lulu
Photos: Courtesy and Copyright Jim Cane
Text: Jim Cane, Bridgerland Audubon Society
Voice: Linda Kervin, Bridgerland Audubon Society

Additional Reading:

Sagebrush Gall made by the fly Rhopalomyia pomum, https://bugguide.net/node/view/200946
Robert P. Wawrzynski, Jeffrey D. Hahn, and Mark E. Ascerno, Insect and Mite Galls, WW-01009 2005,
University of Minnesota Extension, https://www.extension.umn.edu/distribution/horticulture/dg1009.html

Willow Cone Gall Midge
Image Courtesy and Copyright Jim Cane

Field Guide to Plant Galls of California and Other Western States by Ron Russo
ISBN: 978-0-520-24886-1 https://www.amazon.com/California-Western-States-Natural-History/dp/0520248864
Gall, Wikipedia, Wikimedia Foundation, Inc., https://en.wikipedia.org/wiki/Gall (Accessed Dec 2010)
Gagné R (1989) The plant-feeding gall midges of North America. Cornell University Press, Ithaca
https://www.amazon.com/Plant-Feeding-Midges-North-America-Comstock/dp/0801419182