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Posts tagged “Ursus americanus

Black Bears Emerging From Hibernation

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A year ago, in April 2017, while following Black Bear tracks in New Hampshire, I had the good fortune to encounter the bears themselves. Because Black Bears have started coming out of hibernation (April is when most do so) I felt it was timely to share some of my photographs and observations of that encounter. (I did not do so a year ago for fear of bringing attention to and thereby disturbing these bears.)  As I followed the bear tracks, I eventually came upon a refuge, or “babysitter,” tree – where bears rest and cubs/yearlings take refuge when their mother goes off foraging or when she senses danger. I had read about such trees, but never discovered one myself. It was very recognizable — a very large White Pine surrounded on the ground by bear scat and gnawed saplings – fresh signs that bears frequented this area. At the base of the tree were several large “bowls” or indentations in the pine needles that looked as if large animals might have bedded down repeatedly in them, forming nests.

I continued tracking, eventually turning around to head back to where I entered the woods. On my return I passed by the babysitter tree again. To my utter delight I discovered a mother bear with her three yearlings fast asleep in the beds at the base of the tree. It was snowing lightly, and I surmised that this family had recently emerged from their deep winter’s sleep and was still a bit groggy. (Adult males are the first to emerge; females with cubs are the last.) While the yearlings slept on, the mother opened her eyes and decided to tolerate my presence for the next couple of hours. In Naturally Curious posts this week and next, I will share this once-in-a-lifetime experience with you as well as the behavioral observations I made.

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Beechnuts & Black Bears

11-22-17 black bear scat and beechnuts 049A7821One need look no further than this Black Bear scat to know that American Beech (Fagus grandifolia) nuts (hard mast) are a preferred food for Black Bears, both in the fall and spring. They are an important food source for other wildlife as well, including White-tailed Deer, Fishers, Wild Turkeys, Ruffed Grouse and many small mammals and birds.

There are very good reasons why beechnuts are a preferred food for so many creatures. They have about the same protein content as corn but five times the fat content. Compared to acorns, beechnuts have nearly twice as much crude protein, twice the fat of white oak acorns and about the same fat content as red oak acorns. Research on the importance of beech mast for Black Bear reproduction shows that in northern Maine, 22% of the female black bears that were reproductively available reproduced following falls when beechnut production was poor. The proportion of reproducing females increased to 80% following falls when beechnut production was high. (Photo:  Black Bear beechnut husk-filled scat, 1 1/2″ diameter)


Black Bears Raiding Brood

11-1-17 bear binging 049A7147Previously this fall I posted about Black Bears foraging ferociously in the fall in order to store fat (sometimes doubling their weight) before hibernating. That post showed an ant-infested tree that had been ripped apart. As winter approaches, signs of bears’ frenetic gorging (hyperphagia) increase dramatically. Protein-rich sources such as Bald-faced Hornet nests (suspended from branches) and Yellow Jacket nests (in cavities in the ground) are highly sought after.

If you look closely, you’ll see that the claws of the bear that attempted to raid the hornet nest (suspended ten feet above the ground) were able to reach just the bottom portion of the nest, tearing the outer multi-layered, paper envelope but not reaching the brood-containing cells within. The Yellow Jacket cells containing brood (eggs, larvae and pupae), on the other hand, were all removed from the ground nest and consumed. All that remains is a portion of the outer envelope and a few adults.

 


Black Bears Foraging

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This is the time of year when Black Bears are looking for every available source of food in order to bulk up before entering hibernation. During this period of gorging (hyperphagia) Black Bears consume large quantities of fruits, berries, nuts, grasses, roots and insects.

In particular, they favor the brood (larvae and pupae) of ants, due to their relatively high content of fat and protein. Black Bears find brood by detecting the pheromones and other chemicals such as formic acid that ants use for communication and defense. Research has confirmed that Black Bears will dig up as many as 200 ant colonies a day, flipping rocks, moss and leaf litter over and tearing apart logs, stumps and snags (such as the one pictured), using their canine teeth and claws to gain access to the ants. Once they have torn apart the stump or snag, they use their long, sticky tongues to gather brood. Anthills are avoided except for when Black Bears are extremely hungry, due to the fact that bears prefer not to get a lot of soil or sand mixed in with the brood they’re eating. (Thanks to Virginia Barlow for photo op.)


This Year’s Black Bear Cubs Growing Up Fast

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It’s hard to believe that four months ago when it was born this Black Bear cub weighed less than a pound and measured about eight inches in length! Most Black Bears mate in June, but because of delayed implantation their fertilized eggs don’t implant in the uterine wall and the embryos don’t begin developing until the fall (if the mother has had a sufficiently nutritional diet), just as the mother is entering hibernation.

The cubs are born in January, after only a few months inside their mother. They are just a fraction of one percent of the mother bear’s weight, compared to an average human baby that is about seven percent of its mother’s weight. The cubs nurse constantly for the next four months (during which time their mother is not eating or drinking).  The fat content of Black Bear milk can be as high as 20-25 percent. Human milk is comparable to cows’ milk, generally ranging between three and five percent fat. (A biologist who had the opportunity to sample Black Bear milk reported that it was similar in taste to sweetened condensed milk.)

In April, when the cubs emerge from their den, they weigh about six pounds.  Milk production and intake now increases four-fold. Peak lactation (45 ounces of milk per day per cub) occurs in June and July. As a result, the cubs have a huge growth spurt their first summer and will weigh between 40 and 60 pounds by the end of it.

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Woodland Recycler

4-7-17 chickadee on scat 116The ability to find food is crucial for all creatures.  It involves looking in every potential location, including the waste material of other animals.  Nothing goes to waste in the natural world, and I was fortunate to observe an example of this recycling phenomenon recently in bear-inhabited woodlands.

Even though feeding birds is discouraged at this time of year due to the seeds’ appeal to hungry, emerging Black Bears, many find it a hard habit to stop. Inevitably Black Bears will smell the seeds in feeders and help themselves to them.  If this continues long enough, the bears will become habituated and eventually this can lead to their being considered a nuisance, which can lead to their demise. Thus, it’s best to stop feeding birds now that Black Bears have emerged from hibernation.

That said, those who continue to fill feeders in the spring and have had them raided by bears need not fear that their birds are without recourse should they find the feeders empty or missing. Much of what goes in comes out, and bears deposit their seed-laden scat throughout the woods, creating ground “feeders” for all kinds of creatures. In this instance, a Black-capped Chickadee repeatedly helped itself to uncracked sunflower seeds amongst a great deal of millet and sunflower seed husks in the scat of a Black Bear.

This post is dedicated to Sadie Brown, Solid Waste & Recycling Coordinator for the town of Melrose, MA.

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Black Bears Emerging From Hibernation

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Time to take in bird feeders, at least at night. Black Bear sightings are being reported throughout northern New England, a bit earlier than usual probably due to the erratic weather we’ve been having. Adult males emerge from their dens first, females with cubs  last – the opposite order in which they entered in the fall.

Having survived the winter by living off the fat they accumulated last fall, Black Bears weigh considerably less upon waking. Males will typically drop between 15 and 30 percent of their body weight, while lactating mothers can lose up to 40 percent. Even so, for the first two or three weeks following hibernation, bears eat and drink less than they normally do, while their metabolism adjusts to the changes. This is referred to as “walking hibernation” by some biologists. Once normal activity resumes, and until herbaceous green shoots appear in wetlands, bird feeders  are a main attraction.

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