Category: Mammals

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Blackbears

Black Bear Sitting
Photo Courtesy US FWS
Mike Bender, Photographer

Hi, this is Mark Larese-Casanova from the Utah Master Naturalist Program at Utah State University Extension.

I have to admit that it didn’t make much sense to me that yesterday was the start of summer. While sitting in the warm sun, feeling like winter forgot to give spring a turn in the seasonal cycle, I though of the American black bear, another mammal that also probably wondered when the warm weather would finally arrive.

Black bears are native to most of North America, even into northern Mexico. In Utah, black bears are common throughout many of the state’s forests. Contrary to its name, black bears tend to be medium to dark brown in the western US, although its color can range all the way from blonde or cinnamon to black.

As black bears emerge from their winter slumber, they are particularly hungry from several months of living mostly off of fat reserves. This is an even greater challenge for females because cubs are born in January or February and survive on the mother’s milk until spring. So, when spring arrives, they are more than happy to feed on a wide variety of foods, including fruits, nuts, grubs and other insects, small vertebrates, and carrion. Bears are most actively feeding around dawn or dusk, but may feed at other times of day if they become habituated to human food sources.

Young Male Blackbear Climbing Tree
Photo Courtesy US FWS
Steve Maslowski, Photographer

Black bears have been known to attack humans, although usually very infrequently. Attacks most often happen when a black bear is defending cubs or food, or as a result of becoming accustomed to obtaining food from people.

Will the black bears be as hungry for summer as we are? It might be best to not take any chances while out exploring the mountains this summer. When not eating, be sure to carry all food, garbage, and scented items, such as toothpaste and chapstick, in an airtight plastic bag or securely store them in a vehicle or bear-proof container. I’d even recommend carrying bear spray just to be safe. And, don’t forget to hold on tight to those pic-a-nic baskets!

For Wild About Utah, I’m Mark Larese-Casanova.

Credits:

Images: Courtesy US FWS: https://Images.fws.gov
Text:     Mark Larese-Casanova, Utah Master Naturalist Program at Utah State University Extension.
Additional Reading:

Burt, W. H. and R. P. Grossenheider. 1980. A field guide to the mammals. Houghton Mifflin Company, Boston. 289 pp.

Safety in Bear Country https://wildlife.utah.gov/dwr/learn-more/bear-safety.html

Utah Division of Wildlife Resources Utah Conservation Data Center https://dwrcdc.nr.utah.gov/rsgis2/Search/Display.asp?FlNm=ursuamer

 

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Sage Grouse, Pronghorn Antelope and Fences

Sage Grouse, Pronghorn Antelope and Fences: Greater Sage Grouse, Courtesy US FWS, images.fws.gov, Stephen Ting, Photographer
Greater Sage Grouse
Courtesy US FWS
Stephen Ting, Photographer

As Robert Frost famously wrote in his poem, Mending Wall, “Good fences make good neighbors”.

Fences keep livestock from crops, children from traffic and delineate boundaries. In the intermountain West, fences are important to keep livestock where we want them and away from where we don’t. But wildlife of open sagebrush habitat did not evolve with fences. Sage Grouse and Pronghorn Antelope have had a particularly difficult time adapting.

Sage Grouse are stout, chicken-like birds found only in sagebrush, whose foliage features prominently in their diet. Sage Grouse were once abundant, but their numbers have plummeted due to habitat loss. Today they are candidates for listing as an endangered species. In flight, these large bodied birds like to skim over the sagebrush canopy and so doing, careen right into fences. One Utah study attributed 1/5 of Sage Grouse deaths to fence collisions.

[Kevin Colver recording: https://wildstore.wildsanctuary.com/collections/special-collections]

Pronghorn
Courtesy US FWS
James C. Leupold, Photographer

At dawn during the spring, male Sage Grouse congregate on ancestral dancing grounds to attract mates. The birds fly to these lek areas before sunrise so may not be able to see a fence before they collide. Other areas of special concern include the crest of low hills and the midst of wide open flats. Where grouse are common, flagging a fence or otherwise making it more visible can help considerably to reduce airborne fence collisions.

For Pronghorn Antelope, however, the top of the fence is not the issue. They are the swiftest game animal in North America. As with bison, market hunting in the 19th century decimated their populations. This trend has reversed, but here also, fences are a problem. Pronghorn are sprinters, not hurdlers and rarely jump a barrier over 3 feet tall. They choose to go under or through fencelines. A simple solution for barbed wire fences is to string smooth wire for the bottom strand at least 18 inches above the ground. This simple fence fix enables pronghorns to scoot below the fence unscathed as they migrate between winter and summer grounds

The perspective of Pronghorn Antelope and Sage Grouse could be summed up in the lyrics from a Cole Porter song: Don’t fence me in.

This is Linda Kervin for Bridgerland Audubon Society.

 

Credits:

Photos: Courtesy US FWS: Images.fws.gov
Audio: Kevin Colver, https://wildstore.wildsanctuary.com/collections/special-collections
Text: Linda Kervin, Bridgerland Audubon Society
Additional Reading:

Resources:

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

Don’t Fence Me In: If sage-grouse had a song it would be “Don’t Fence Me In”, USDA Natural Resource Conservation Service, https://www.mt.nrcs.usda.gov/technical/ecs/biology/sagegrouse/dontfence.html

Safer Fencing Can Help Save Western Birds, Environmental Defense Fund, https://www.edf.org/article.cfm?contentID=9126

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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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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)