Looking inside a black bear den

Carefully I crawled down under the roots of a fallen tree to take a look at a black bear in its den. Resting on a bed of dried ferns, she was only inches away--the closest I’ve ever been to a black bear. Even though she was sedated, I didn’t linger long because I knew two yearlings were wide awake farther back in the den.

Inside the den, the black bear rests with her head away from the entrance. Her two ear tags are visible along with the blue blindfold biologists used when taking off her GPS collar.

I was lucky enough to be accompanying three biologists who were retrieving a GPS collar from this female bear. 

The retrieved collar

The end of January and the beginning of February is the ideal time to retrieve a collar from a black bear. They are the most lethargic at this point and will go back to sleep more readily. 

However, we approached the den as quietly as possible because black bears can easily be awakened since they are not true hibernators. They only drop their body temperature 12 to 14 degrees Fahrenheit in the winter (to around 88 degrees Fahrenheit). Just digging snow away from the entrance caused the female to start shivering, which meant she was preparing to wake up to defend herself.

She fought the drugs for nearly an hour, moving about the den as she did (a tarp over the entrance deterred her from coming out). By this point the two yearlings were awake and one tried to escape over the biologist who was cutting off the female’s collar. 

Biologists preparing the drugs to sedate the bear. They staged away from the den, visible behind the farthest biologist, to minimize noise.

The yearlings will stay with their mother until this spring when she drives them away so she can mate. Black bears have a two year breeding interval. A female will mate in the spring, give birth the beginning of February, raise the cubs over the summer and fall, and den with them that winter. 

This female black bear and her cubs decided to den in a spacious hole under the roots of a fallen tree. Black bears also commonly den in brush piles or hollow trees but they typically won’t reuse a den.

The den isn’t barren; black bears bring in grass and leaves to curl up on. In this den, she was laying on dried fern fronds and shredded bark. The biologists have also seen beds of dried bear grass. 

When the biologists first saw the female bear in the den, she was quite close to the opening, giving the impression the den was small. Her thick layer of fat and thick fur (which doubles in thickness in the winter) was keeping her warm.

From the den entrance, the rear end of the black bear is barely visible

For being curled up in a den from November to mid-April, the den didn’t smell at all, besides the earthy smell of disturbed dirt. Black and grizzly bears don’t defecate or urinate while hibernating. They also don’t eat or drink.

Their bodies are uniquely adapted to process the fat they burn, and break down and reabsorb their urine back into the body so nothing is wasted. 

Biologists covered the entrance to the bear den with snow so the sow wouldn't think it was spring when she woke up from the drugs.

In order to have enough fat reserves for winter, they gorge themselves on berries, especially huckleberries, and other food before they den. If the food supply is low, black bears will den sooner, as early as October. They don’t den to escape the cold, but because of the dwindling food supply.

Come mid-April when they awaken and emerge from the den, the female probably won't remember our encounter but I sure will.

Note: For more information on the black bear research being conducted, see blog post on "Black bear research sends biologists into bear den" posted on Feb. 19, 2013. 

Note: Published in the Bonners Ferry Herald on Jan. 31, 2013.

Several ways fur can keep animals warm

Deer don’t check the thermometer in the morning when they wake up to determine how many layers to put on. Humans are the only mammals that care what temperature it is outside. The rest of the mammals that are active in winter are well-equipped to handle cold temperatures around the clock. 

A deer's coat can keep it warm to minus 30 F

In the fall, many mammals that don’t hibernate or migrate molt into a winter coat. For some animals this means an entirely new coat of fur, such as snowshoe hares, and for others it means growing additional fur, such as porcupines. 

Fur traps dead air next to an animal’s body and creates a blanket of insulation. More fur equals more insulation. 

Animals that increase the density of their fur coat include beavers, red foxes, coyotes, mink, fishers, river otters, marten and weasels. 

Martens increase the density of their fur to stay warm

To stay even warmer, some mammals grow underfur. Porcupines grow a dark, woolly underfur that they shed in the spring.

Snowshoe hares and ermines (short-tailed weasels) molt into a white winter coat, not only for camouflage against predators, but also for insulation. A snowshoe hare’s white winter coat is 27 percent more insulating than its brown summer coat, in part to the density of the hairs but also the color. 

A snowshoe hare's brown summer coat

Snowshoe hare's white winter coat

Oddly enough white hair is more insulating than brown hair. Brown hair is filled with pigments to make the brown color. White hairs lack these pigments, giving them the white color, and nothing replaces the pigment except air. The air trapped within the hair provides additional insulation on top of the air trapped between the hairs. More trapped air means greater warmth, just like a thicker down jacket or sleeping bag. 

Less conspicuous are the ungulates, such as deer and moose, who also change their hair structure from solid to hollow with the winter molt. Even though the pigment remains in deer, the hollow-shafted winter hair keeps them warm to minus 30 degrees Fahrenheit. Polar bears and wolves also have hollow-shafted hair.

The mountain goat combines several of these strategies, including growing a double coat of white fur. Before the first snowfall, a mountain goat will grow a fine, dense undercoat of woolly fur that is more than three inches thick. The undercoat is then covered by a thick layer of hollow, seven-inch-long guard hairs that also partially covers the legs. This extreme winter coat allows the goat to withstand winter temperatures as low as minus 50 degrees Fahrenheit and winds as high as 100 miles per hour. 

Mountain goats are adapted to endure the extreme cold

Thick fur is not always advantageous. Predators like weasels have to compromise between warmth and agility. If ermines had thick fur, they wouldn’t be able to squeeze into crevices and tunnels in the snow after their prey. 

Some small prey, such as mice, don’t grow a thick winter coat. They rely on other winter adaptations to survive, such as living in the subnivean zone (beneath the snow) where the temperature stays just above freezing. 

But for animals exposed to cold temperatures, a winter coat is one of the ways they keep warm, just like us. 

Note: Published in the Bonners Ferry Herald on Jan. 24, 2013.

Nature’s seed dispersal inspiration for Velcro

From the cuffs of coats to children’s shoes, Velcro has made our lives easier but it has existed in nature longer than we can imagine. Anyone who has encountered burs, cockleburs or nutlets (seeds from hound’s-tongue) knows how well they cling to clothing, especially wool or fleece. 

Nutlets of Hound's-tongue are about 1/4" long (7mm)

Burdock burs entangled in his dog’s fur inspired Swiss engineer George de Mestral to develop Velcro, which was first called sticky sticks. The tiny hooks on the end of the burs enabled the seeds to stick to almost anything that brushed against it, including sheep’s fleece, animal fur, bird feathers and clothing. The short, barbed prickles on the nutlets of hound’s-tongue (also referred to as “stick tights”) do the same.

When they cling to our pants, mittens or shoelaces, we pick them off when we notice them, depositing them far from the plant--exactly the plant’s goal. While other plants depend on wind, water or ingestion to disperse their seeds, these plants, along with others, depend on attaching to an animal to be dispersed. 

Hound's-tongue plant with seeds still attached

This dispersal method has allowed both burdock and hound’s-tongue to spread across North America after being introduced from Eurasia and Europe, respectively. Not having any natural enemies allows for uninhibited expansion.

Hound’s-tongue goes as far as being toxic enough to cause irreversible liver damage if a large quantity of fresh or dried plant matter is consumed. Hound’s-tongue in cattle pasture is a problem with nutlets clinging to cattle’s hair and the potential of ingestion.

Inside of a nutlet looks like nutmeat but please don't eat it

The longevity of the seeds also helps in dispersal. Hound’s-tongue nutlets are viable for up to three years on the plant and one year if buried. The nutlets can stay on the plant for many years because the plant is a biennial. The first year a low-growing rosette forms and in the second year the plant grows up to two feet high, produces seed and dies. The rough-textured, tongue-shaped leaves on the plant inspired its name.

Cockleburs seeds can be buried for 16 years and still have a 15 percent germination rate after being recovered to the surface. A unique germination strategy allows for this longevity. Each bur contains two seeds and one of those seeds will germinate under normal conditions. The second seed has a special seed coat that prevents the uptake of oxygen which is needed to break down the germination inhibitor. Only after the seed coat is punctured, removed or decayed, will the second seed germinate. 

Common burdock burs are viable for up to four years. The differences between common burdock and cockleburs is that cockleburs have heart-shaped leaves and smaller, egg-shaped seed heads, whereas common burdock leaves are similar to rhubarb and have rounder seed heads. 

Burdock burs on fleece

Cockleburs, burs and nutlets are hardy seeds that can easily become established in disturbed soil, such as trails and roadsides. To minimize the continued invasion of these plants, don’t pick off the Velcro-inspiring seeds and drop them anywhere. Instead, the best way to dispose of the seeds is to burn them or place them in the garbage destined for the landfill. 

Note: Published in the Bonners Ferry Herald on Jan. 17, 2012. 

Teeth tailored to animal’s diet

Moose nip the young growth from willow trees in the winter while wolves tear meat from a freshly-killed deer. Neither could eat what they do without the specialized teeth in their mouth. 

Carnivores, such as wolves, have carnassial teeth to shear meat

Each species of mammal has different teeth in terms of size, shape, organization and number. Similarities exist between mammals of certain eating habits, which include carnivores (meat eaters), herbivores (plant eaters), omnivores (meat and plant eaters) and insectivores (insect eaters). 

Not all animals have the four main groups of teeth: incisors, canines, premolars and molars (the latter two referred to as cheek teeth). Each group of teeth performs a different function: grasping, killing, chewing, nipping, grinding or crushing. 

Incisors are the small, chisel-shaped teeth at the front of the jaw that are used for cutting, scraping and tearing. Incisors are larger in rodents and lagomorphs (rabbits and hares). 

The canine teeth are prominent on these two skulls

The canines, which are prominent on carnivores, are the conical, pointed teeth used to capture and kill prey. 

Located at the back of the jaw are the premolars and molars which are primarily used for grinding and shearing. 

Herbivores (such as moose and rodents) lack canines because they don’t kill and capture prey. Instead they have very sharp edges on their incisors which make them excellent for cutting vegetation. Since grasses have hard, abrasive silica in the fibers, they are tough on teeth. Herbivores counter this abrasiveness by having cheek teeth with high crowns and hard enamel ridges that last a long time with intense use.

Hippos have high-crowned molars

Rodents, such as mice, squirrels, porcupines and beavers, would wear out their incisor teeth with all the gnawing, nipping and biting of plant material they do. However, they have continuously growing incisors in both the lower and upper jaws to prevent this. Rodents also have a gap between their incisors and molars where the canines are typically located.

Members of the deer family lack incisors on the upper jaw. Instead the upper jaw has a callous pad where the bottom incisors touch. The lack of upper incisors is the reason why they don’t leave a clean ‘snip’ on vegetation, instead they leave a ragged cut. 

Carnivores also have specialized molars called carnassial teeth. Their last upper premolar and first lower molar are jagged and serrated to help shear pieces of flesh off carcasses so that the meat is small enough to swallow. 

The carnivore’s canine teeth are typically larger and longer than their other teeth, mainly because they are used to seize prey. However, a walrus’s tusks are large canine teeth and don’t aid in capturing prey. Instead they are used for fighting, cutting breathing holes in the ice and helping the walrus haul itself onto ice. 

Walrus tusks are elongated canine teeth

The carnivorous river otter’s teeth demonstrate how teeth can be specialized for their diet. The otter’s incisors tear off small pieces of flesh, the canines hold slippery fish, the premolars shear through flesh, and the molars crush fish bones. 

Then there are the animals that can eat both plants and animals, the omnivores. The teeth of an omnivore aren’t specialized for anything but this allows them to eat everything. A raccoon, which is an omnivore, can eat everything from fish to insects and fruits. Grizzly bears can eat carrion, tubers and huckleberries. 

Totally different from other mammals are the insectivores, such as shrews and moles. In order for them to crunch the hard exoskeleton of insects, their cheek teeth are square with sharp cusps and edges. Shrews also have long front teeth that project forward to grasp small insects. 

From tiny shrew teeth to an elephant’s elongated incisor teeth (tusks), the shape, size and position of teeth can provide considerable insight into an animal’s diet and lifestyle. 

Note: Published in the Bonners Ferry Herald on Jan. 10, 2013. 

Outdoor Trivia: What do you remember?

I thought a quiz highlighting trivia from my outdoor columns throughout 2012 would be a fun way to end the year. 

1. The foliage of a yew most closely resembles the foliage of a: 
a. Western hemlock
b. Giant coastal redwood
c. Ponderosa pine

2. What is the only substance naturally found on Earth in a liquid, gas and solid state?

a. Carbon dioxide

b. Ammonia

c. Water

3. What animal is the primary predator of porcupines and whose scat may contain porcupine quills? 

a.Fisher

b. Wolf

c. Cougar

4. What animal significantly alters its environment for food and shelter?

a. Snowshoe hare

b. Pileated woodpecker

c. Beaver

5. What animal has more than one thousand times better sense of smell than humans?

a. Dogs

b. Bears

c. Turkey vultures

6. The mountain goat’s extraordinary climbing ability is attributed to?

a. Specialized hoofs

b. Massive shoulder muscles

c. Keen sense of balance

d. All of the above

7. A hummingbird can beat its wings how fast?

a. 40 to 60 times per second

b. 60 to 80 times per second

c. 80 to 100 times per second  

8. Altricial young are born:

a. With eyes open, able to walk and feed themselves

b. Blind, naked and totally reliable on parents

c. Friendly

9. What creature’s favorite food is aphids?

a. Ladybugs

b. Grasshoppers

c. Juncos

10. Which animal has a gizzard?

a. Grouse

b. Earthworm

c. Neither

d. Both

11. Nimbostratus clouds are indicative of what type of weather?

a. Thunderstorms

b. Fair weather

c. Steady precipitation

12. How long does it take a photon of light to travel the 93 million miles from the surface of the sun to Earth?

a. Eight minutes

b. 24 minutes

c. 49 minutes

13. How many pigments create the diversity of colors on bird eggs?

a. Three

b. Four

c. Five

14. Northern pygmy-owls are considered diurnal because they are active: 

a. During early morning and evening

b. During the day

c. At night

15. The western fairy slipper, native to Idaho, is a:

a. Butterfly

b. Noxious weed

c. Orchid

16. A midden is a:

a. Bear cave

b. Squirrel’s cache of cones

c. Cattail root

17. How many eggs can a female mosquito lay?

a. 10 to 30 eggs

b. 100 to 300 eggs

c. 1000 to 3000 eggs

18. A lichen is a:

a. Plant

b. Fungus

c. Fungus and alga

19. Subnivean refers to:

a. Below the snowpack

b. Below the skin

c. Beneath a rock

20. Which tree has ‘puzzle’ bark?

a. Douglas fir

b. White pine

c. Ponderosa pine

What animal created the holes in this birch tree?

Answers to the Outdoor Column trivia: 

Photo question: Sapsuckers chisel the small rectangular holes to lick up the sweet sap that oozes from them. 

1. (b) The main difference is the redwood’s foliage is whitish underneath whereas the yew’s foliage is yellowish-green underneath. 2. (c) 3. (a) Fishers are the main predators of porcupines. 4. (c) Beavers ‘log’ an area for food and shelter and build dams to access more trees and create a deeper pond for a lodge. 5. (a) Dogs have 44 times more olfactory receptors than humans. 6. (d) 7. (c) Hummingbirds can also fly backwards and sideways. 8. (b) Altricial young include bear cubs, coyote pups, squirrels and all perching birds. 9. (a) A single ladybug can eat nearly 5,000 aphids in its lifetime. 

10. (d) Both the grouse and earthworm have gizzards to grind food so nutrients can be absorbed. 11. (c) 12. (a) But the photon may take up to a million years to travel from the center of the sun to the surface of the sun. 13. (a) Protoporphyrin, biliverdin and zinc chelate. 14. (b) Crepuscular animals are active in the early morning and evening while nocturnal animals are active at night. 15. (c) 16. (b) 17. (b) A mosquito egg can develop into an adult in four to seven days. 18. (c) A lichen is a combination of a fungus and alga. 19. (a) Subnivean refers to below the snowpack and above the ground. 20. (c)

How much did you remember? What was your favorite outdoor column? Post a comment! 

Note: Published in the Bonners Ferry Herald on January 3, 2013.