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Adaptations

How Beavers Digest Cellulose

12-26-14 beaver sign 125Some beavers are still managing to find openings in their ponds which give them access to fresh cambium, the soft layer of wood just under the bark of a tree. Cambium contains a lot of cellulose, in addition to starches and sugars. Like all herbivores, beavers do not possess enzymes that are capable of breaking down the large cellulose molecules (cellulases). In their place, beavers employ micro-organisms, such as bacteria, that can break down cellulose.

These bacteria are located in a pouch called a cecum, located at the beginning of the large intestine. (Ruminants such as moose and deer have rumens in place of ceca.) Colonies of these microorganisms in a beaver’s intestines digest up to 30% of the cellulose from the woody material that it eats. Further nutrients are recovered in the form of fecal pellets that the beaver re-ingests.

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Ruffed Grouse Nostril Feathers

12-16-14 ruffed grouse nostrils IMG_2376Ruffed Grouse have adapted to cold winter months in a number of ways, from growing “snowshoe” pectinations on their toes to having their legs covered with fine feathers. Equally effective are the feathers covering a grouse’s nostrils, which are thought to heat cold air as the bird breathes in. (Thanks to Sara and Warren Demont for photo op.)


Black Bears Still Active

12-15-14  bear track in snow 049A7902While some, perhaps most, black bears have entered hibernation in northern New England by now, there are still some active individuals, probably males, who are finding enough food to delay denning. Typically a scarcity of food and cold weather trigger the reduction in the metabolism of a black bear, which signals the onset of hibernation. If the weather remains relatively warm and/or there is a large supply of beechnuts and/or acorns, signs of bears can occasionally be found even this late in the year. While there have been a few years when black bears have been sighted throughout the winter, most wildlife biologists say that it is safe to put up bird feeders in December, as sunflower seed-loving bears have usually retreated to their den sites by now. The pictured tracks and scat discovered in the past few days in central Vermont challenges that assumption (as does the stolen bird feeder). (Thanks to Erin Donahue and Charlie Berger for photo op – sensitive fern fertile frond for size comparison)

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Why Cardinals Are Red

12-12-14 cardinal DA8A9669The diet of a Northern Cardinal consists mainly of seeds, fruits and insects (average annual consumption is 29% animal and 71% vegetable matter). As fall progresses, the proportion of vegetable matter in its diet increases until it reaches a high of 88% during winter. The red plumage color of both males and females (females have some red feathers in wings and tail) results from the ingestion of carotenoid pigments obtained from their diet during the fall molt (September/October). Fruits and insects are high in carotenoids, while most seeds are poor sources. According to Cornell Lab of Ornithology, new research has shown that brighter males have higher reproductive success and territories with greater vegetation density, and that plumage brightness in both the male (breast color) and female (color of underwing-coverts) is positively correlated with parental care (feeding nestlings).

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Woodpeckers Bark Sloughing

woodpecker bark peeling IMG_0567Several species of woodpeckers search for wood-boring beetle larvae by removing the bark from a tree (in addition to drilling holes). This is referred to as bark sloughing. Some birds, such as nuthatches, remove only scales of bark, not the whole layer like woodpeckers, and this is referred to as scaling. After finding or creating an opening, a woodpecker repeatedly slips its pointed beak under loose bark, prying it off of the tree. It then uses its long, barb-tipped tongue to capture the exposed insects. Different woodpecker species tend to feed on either trunks or branches, and at different heights. Initially sloughing can resemble the work of porcupines, but close examination can reveal the marks of a beak, which are perpendicular to the trunk or limb, rather than the grooves left by a beaver’s incisors.

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Canada Geese Switch Diet to Berries & Grains

12-4-14  Canada geese2 IMG_5615During migration and throughout the winter, Canada Geese are highly gregarious, often gathering and feeding in flocks that consist of over a thousand geese. Almost exclusively herbivorous, they are efficient grazers, having serrations on their stout, flat bills. During summer they feed primarily on grasses and sedges. Considered a nuisance by many people with large lawns Canada Geese are attracted to these lawns not only because they can digest grass, but also because they have an unobstructed view that allows them to detect approaching predators. During and following migration, berries (especially blueberries) and agricultural grains including sorghum, corn and winter wheat make up most of their diet. When you see them in cornfields, they are feeding on fallen kernels as well as corn still on dry cobs — they are very good at removing the kernels.

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Woolly Oak Leaf Gall

11-28-14  woolly oak leaf gall IMG_3574Of the 2,000 kinds of galls found on North American plants, 800 different kinds form on oaks. One of these is the woolly oak leaf gall, produced by a tiny Cynipid wasp, Callirhytis lanata. This gall is usually attached to the mid-vein on the underside of an oak leaf, and looks like a ball of wool. It may be as large as three-fourths of an inch and is often bright pink or yellow in color, fading to light brown in the fall. Oak trees have lots of tannic acid in them (a defense which makes the tree unpalatable to herbivores), with the highest concentration found in oak galls. (The bitter taste is where the name “gall” originated.) It’s possible, since tannins are somewhat anti-microbial, high-tannin galls such as the woolly oak leaf gall may protect the larva against fungi and bacteria.

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