Tail Flashing Cache Faker – Western Gray Squirrel


The Western Gray Squirrel is a tree (arboreal) rodent and is the largest of its kind in the Sierra Nevada Mountains weighing between one-half to two pounds. Tree squirrels like dense cover in which to travel across branches, build several kinds of nests, and seek safety. They live at nearly every elevation in Nevada County. Favorite trees are the black oak.


Like crows and ravens, tree squirrels are keen people watchers. If you live in their territory, chances are they know a lot more about you than you do about them. Active during the day, squirrels understand human activity patterns and they can recognize the people who feed them and the people who thwart them.

In spring they undergo a full body molt and in fall a neck to rump molt.  


As with the North American Beaver, Porcupine, and other rodents, a squirrel’s teeth grow continuously. They must gnaw and chew to keep them from getting too long.

When a Wester Gray Squirrel finds a nut, it will roll it for approximately twenty seconds. Biologists think the animal is evaluating the quality of the nut -if it should be eaten immediately or cached away for winter. 

Twenty-second nut roll. Behavior thought to be nut quality evaluation. Eat now or cache for later.

The cache fake-out happens when a squirrel pretends to bury a nut – with other squirrels watching – then moves to another place to actually burry it. Another impressive aspect of squirrel behavior is their ability to memorize the location of their caches. 

(Eastern Gray Squirrel - identified by brown fur around eyes - shown in video)

Many tail uses;

  • blanket
  • blood coolant
  • climbing counterbalance
  • raincoat
  • communication

If a squirrel holds its tail in an S shape, it’s feeling threatened. It waves it to look larger.

Another special skill is leaping up trees, all four paws raise at the same time, but it happens so quickly it’s difficult to see. When going down a tree, their back feet rotate so claws act as anchors. 

Leaping. Photo Credit: Dan Johnson

When traveling long distances, a squirrel’s preferred travel mode is from branch to branch, high off the ground. When foraging for food, or hurrying between caches, they will scamper on the ground, but at the first sign of danger, back to tree safety they go! 

Native Western Gray Squirrels need a continuous stretch of mature oak trees for survival. 

‘Sleep rough’ is thought to be a method of temperature control. This is when a squirrel lays on its belly, spread out as much as possible. Often they’ll do this on branches but it’s also been observed on the ground, on the picnic tables, or anywhere that is squirrel appealing.

Sleeping rough is thought to be a behavior that helps regulate body temperature.

Defense Behavior

Western Gray Squirrels work cooperatively like many prey animals to sound alarm warnings. 


(Fox Squirrel shown in video)

In the winter, squirrels don’t hibernate but they do slow down. This is when nut caches are consumed.


  • acorns
  • pine nuts
  • new leaf buds
  • fruit
  • bird eggs
  • seeds
  • small birts
  • fungi
  • bark
  • sap
  • insects

Raiding bird feeders is summer fast-food. As winter approaches, they devote more time to scatter-hoarding.

*Forgotten caches help trees grow in new locations. 

Western Gray Squirrels compete for the same food sources as the acorn woodpecker, ground squirrels, and other introduced squirrel species (S carolinensis and S. niger).

Life Span

7-8 years


Breeding happens in late spring starting at about a year old. A female signals readiness with enlarged, pink vulva and a male with a scrotum that turns from pink to black. The act of mating is vigorous and taxing.

Nesting mothers use their own molted hair to line the nest (drey). She’ll also use shredded bark, moss, and lichens.

Gestation is about 43 days. Younger females will have smaller litters compared to more mature breeding females who average between 3 – 5 hairless kits. Babies nurse for about two months but stay in the nest for about six months total. Tails don’t fill out until babies are out of the nest.

The second type of nest build by Wester Gray Squirrels is a sleeping platform, it is not as enclosed as the birthing nest and is for temporary use.  


  • bobcats
  • coyote
  • foxes
  • owls
  • hawks
  • house cats

Habitat Threats

  • urbanization habitat loss
  • roadkill
  • wildfires
  • fire suppression management
  • overgrazing
  • scotch broom invasive species
  • mite diseases
  • competition with introduced squirrel species and wild turkeys

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Agility test

Bay Nature – Are Fox Squirrels Replacing Gray Squirrels in California?

iNaturalist – Western Gray Squirrel

Phys.org – Squirrels have a long memory for problem solving

U.S. Fish & Wildlife Service – Conboy Lake (WA) – Western Gray Squirrel

Wikipedia – Western Gray Squirrel





Porcupine – Pointed Payback for Getting Too Close

If you’re lucky enough to see one of these shy nocturnal rodents, don’t worry. It won’t charge or shoot sharp darts. If your dog sees it, his/her up-close canine curiosity may result in a painful payback.

Deer Creek Porcupine Spotters Needed!

According to the Nevada County Resource Conservation District and Wikipedia’s List of Mammals of California porcupines should live in the Deer Creek watershed. However, recent  iNaturalist observations (2019-2020) only show sightings in the Sutter Buttes and around Truckee. The California Department of Fish and Wildlife is asking the public to log sightings. (See last paragraph below.)

Red dots show 2019-2020 iNaturalist North American Porcupine observations. The aqua strip shows the location of the Deer Creek watershed.

Historic Names

  • Thorn pig
  • Quill pig

These animals are north American’s second-largest rodent after the beaver.

MYTH CORRECTION: Porcupines don’t shoot quills

Hair, Quills, Stink & Antibiotic Skin

Most of the animal is covered guard hair that looks like quills. Quills are located in a structure, called the rosette, on the animal’s back-side. It flares out – like a dog raising hackles – when the rodent feels threatened. In order to become stuck by the quills, the threatening animal must press against the rosette which triggers quill release. Porcupines will also do tail slaps, similar to beavers, as a warning or with direct contact. Smartly, they aim for the face!

Quills are lightweight and hollow. In addition to defense, they also help the porcupine stay warm in cold weather.

Within the rosette is skin that produces a noxious odor – R-Delta-Decalactone- a waxy grease that spreads to nearby quills and hair. It emits a stink cloud announcing the animals’ presence, especially at night.  Folks familiar with the smell say it’s similar to strong body odor or soft cheese.

Photo Credit: Rob Routledge, Sault College, Bugwood.org

Medical researchers are studying quill barb designs for an alternative to surgical staples (see articles in Resources below).

According to Dr. Uldis Roze, who was punctured by a quill that traveled up his arm, porcupines produce antibiotic chemicals that coat their quills. It’s a defense against self-injury., a common occurrence when porcupines fall from trees.

Additional Defenses

In addition to quills and a stink that grows stronger with fear, it’s black and white coloring and teeth clacking are also defense mechanisms.


North American Porcupines are nearsighted, slow-moving, and solitary. During the day they spend most of their time in trees. In winter, they’ll hang out near their den.


The North American Porcupine is an herbivore. Below is a list of food sources.

  • roots
  • twigs
  • stems
  • nuts
  • berries
  • grasses
  • tree bark
  • conifer needles

Porcupines crave salt. Campers, backpackers, forestry and road workers say they can be found along snowy roadsides looking for salt. They’ve also been known to chew sweat-soaked socks, boots, gloves and wooden tool handles. They’ll also chew on plywood for the salty-tasting chemicals added.

Photo Credit: Dave Powell, USDA Forest Service (retired) Bugwood.org
Photo Credit: Photo Credit: Rob Routledge, Sault College, Bugwood.org






Den and Scat


  • coyote
  • wolf
  • black bear
  • mountain lion
  • golden eagle
  • great horned owl


Mating begins in the fall high up in tree branches. To signal receptivity, the female excretes a strong odor – a mixture of urine and mucus. Males arrive and wait. If multiple show up, they fight for dominance.

When the winner approaches the female in the tree, he spritzes her with urine which begins a chemical reaction sending her into full estrus. To complete the process, they move to the ground where female holds her quills flat against her body and lifts her tail so as not to injure the male.

Porcupine Mating in a Zoo

Compared to other rodents, North American Porcupine mothers are pregnant for 202 days.  (A female beaver carries for 128 days.)

They give birth to one soft-quilled procupette at a time. Quills harden after birth. A porcupine mother will nurse her young for up to four months.

Young are full-grown in two years.

Mothers care for youngsters but do not defend them from predation.

Life Span

If they are not hunted by humans, poisoned, killed by cars or die of starvation, a healthy North American Porcupine can live up to 30 years.

Human Uses for Porcupines

Native Americans have traditionally used porcupine quills for decoration and warmth.

Hunters eat them and farmers have exterminated them as pests.

California Department of Fish and Wildlife (and iNaturalist)

“Observations of porcupines in recent years have become relatively uncommon and DFW is soliciting sightings from the public. In California, porcupines are most common in montane conifer and wet meadow habitats, and can be found in the Coast Ranges, Klamath Mountains, southern Cascades, Modoc Plateau, Sierra Nevada, and Transverse Ranges.” – CDFW

Report a North American Porcupine sighting for the California Department of Fish and Wildlife here

Report a North American Porcupine sighting on iNaturalist (California Academy of Sciences & National Geographic)

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Animal planet – Urban Relocation 


Bay Nature – Do Porcupines Life in the Bay Area? 

CBS Sunday Morning (Utah)

Chicago Tribune – Heal Thyself, Oh Fat and Prickly Porcupine

Cleveland Museum of Natural History

CPR News – Porcupine Barbs for Better Wound Healing

Discovery Magazine – Why Porcupine Quills Slide in with Ease but Come Out with Difficulty

Lander the cute baby porcupine (Montana)

Live Science – Porcupine Facts

National Library of Medicine – Antibiotic Properties of Porcupine Quills

North American Porcupine – Desert Museum (Arizona)

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North County Public Radio – Porcupine Quills Like Hairs, Like Feathers












Porcupine Stink

Proceedings of the National Academy of Sciences of the United States of America – Microstructured barbs on the North American porcupine quill enable easy tissue penetration and difficult removal

Removing Porcupine Quills – Quills Can Travel Through the Body

Seeker – Porcupine Quills Inspire Medical Devices





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