An online resource based on the award-winning nature guide

Mammals

Muskrats Constructing Lodges

10-8-14 muskrat lodge3 012Muskrats, in addition to digging bank dens, also build lodges in which to live. Muskrat lodges resemble beaver lodges, but are usually much smaller (up to eight feet high, and four feet wide) and are made of vegetation, not sticks, like beaver lodges. Most lodge construction occurs in May and early June, and again in October. Typically they are built in no more than two feet of water. A single dry chamber (entrance below, chamber above the water line) houses a pair of muskrats, and often several litters of young (the mother adds a chamber for each litter). Even though the walls of a muskrat lodge are up to a foot thick, mink, foxes and coyotes often dig into them in the winter. Two or three smaller versions of a lodge, called “pushups,” serve as protected feeding platforms.

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Gray Squirrels Caching Nuts

9-26-14 gray squirrel with nuts 015Many species of squirrels, including the red squirrel, are “larder hoarders.” Each individual stores its food in one central area that it defends aggressively against invaders. Eastern gray squirrels, however, are “scatter hoarders,” collecting and burying one nut at a time throughout home ranges up to 7 acres in size. It has been estimated that up to 25 percent of the nuts that gray squirrels cache are stolen by other gray squirrels. Researchers have found that gray squirrels engage in “deceptive caching.” Carrying a nut, a squirrel will repeatedly dig a hole and then fill it in, without depositing the nut. They also will cover a spot with leaves, even though they have not buried anything in this location. Where gray squirrel densities are high, the squirrels often keep a cache in its original location for only about three days before moving it to a new location.

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The Silent Communication of White-tailed Bucks

9-23-14  antler rub IMG_7310Rising levels of testosterone circulating in a buck’s blood toward the end of summer results in the maturation of antlers and the drying up of the velvet that was providing nutrients to them. It used to be thought that bucks engaged in rubbing their antlers against saplings at this time of year in order to remove the velvet, but research has shown there is much more behind this behavior. Rubs are visual and olfactory sign posts that transmit important information to other bucks and does in the area prior to and during rut, such as individual buck identification, breeding readiness, age and hierarchy.

The positioning of the antlers against a tree is not random — a buck generally rubs the base of his antlers and his forehead skin against the tree. The skin between antlers contains a multitude of scent-producing skin glands called apocrine glands (humans have them and utilize them during emotional sweating). These glands typically are inactive during the summer months, but in response to rising testosterone levels, they become increasingly active in the fall. The most active glands are found in mature dominant bucks.

Thanks to recent studies we know that more rubs are made in years of good acorn production than in poor mast years. Young bucks appear to make fewer rubs than mature bucks, and they tend to start rubbing much later in the fall (so rubs you find now were most likely made by mature bucks). Research suggests that older bucks may be making more than 1200 rubs during the roughly 90-day rubbing period, which comes to about 15 rubs per day.

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Moose & Water

moose shaking 472Moose spend a great deal of time in and near bodies of water, feeding, cooling themselves and avoiding insects. They are powerful swimmers, exhibiting great speed and endurance. Moose have been observed swimming distances up to 12 miles, and are known to occasionally swim from one point of land to another when the distance is shorter by water than by land. (Adult moose usually swim with only their head out of water, whereas yearlings have most of their back exposed.) Moose can spread their hooves, and this is ability is thought to enhance their paddling skills.

Much of a moose’s summer diet is semi-aquatic and aquatic vegetation, thus they feed near shore as well as in deeper water. Studies have shown that moose will dive as deep as 18 feet to obtain submerged plants. It is slightly unsettling to see them totally disappear for up to nearly a minute while foraging under water!

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Moose Pheromones Active During Rut

9-11-14 cow moose urinating 436While the mating season, or rut, for moose peaks between late September and early October, mating behavior can already be observed. It is widely known that male, or bull, moose often paw a pit in the ground, urinate in it and then stomp in it in order to splash their underside, slap the urine with their antlers to disperse it, and lay down in the pit and wallow in their urine, soaking their undersides and neck. Their pungent urine serves as an aphrodisiac for female, or cow, moose, which are attracted to the pheromones it contains. A cow will enter a wallow, aggressively displacing the bull at times and even drink his urine.

However, it’s not just bull moose urine that attracts the opposite sex. The urine of a cow in heat (defined as the two days of their estrous cycle when they will allow a bull to mount them) is equally as attractive to bulls. At this time of their reproductive cycle cows frequently will urinate in the water and along the shoreline of lakes and ponds (look closely at photo).

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Cow Moose Bulking Up for Winter

cow moose head 461


Moose Gaining Fat Reserves

9-10-14  moose standing in water 277Being an ardent admirer of moose, I am devoting today’s post as well as the next two posts to the largest member of the deer family. Even if it weren’t seven to ten feet long and didn’t weigh over a thousand pounds, a moose would be an impressive mammal, with its high, humped shoulders, broad, pendulous muzzle and long, coarse hair.

Moose are voracious eaters, consuming roughly 44 pounds of plant material a day. In the winter their diet, mainly the bark of woody plants, provides only about 70% of the energy they need to survive. Thus, during the spring and summer they spend up to 12 hours a day foraging, often for aquatic plants, and acquire more than 200% of the energy they need. Hundreds of pounds are gained, with the excess stored as fat reserves for the coming months. Even so, moose lose up to 20% of their weight over the winter. (Thanks to all who wished me happy recharging!)

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