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Mammals

Meadow Vole Tunnels Exposed

3-31-15  meadow vole exposed tunnels IMG_3528If you live where the snow is actually melting, a labyrinth of vole tunnels may be revealing itself to you. These tunnels were excavated in the snow next to the ground in what is referred to as the subnivean layer. They lead from sleeping areas to known sources of food, and are advantageous to both mice and voles that travel in them – they provide thermal insulation by protecting them from the wind and cold, and they keep these rodents hidden from predators. Carbon dioxide, which builds up in the subnivean layer from animal respiration as well as CO₂ released from the ground, escapes through ventilation shafts, or air vents, that lead up to the surface of the snow.

Voles stay in these tunnels as long as the snow is deep enough not to expose them, finding food in the form of plants, seeds and bark from bushes and shrubs as they dig through the snow. This winter has provided voles, mice and shrews with an extended period of protection, as hungry barred owls attest to.

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Porcupines Marking Dens

3-25-15 porcupine den IMG_9681Often, at this time of year, porcupines stake out their den trees (if they’re not inhabiting rocky ledges) by eating patches of inner bark, or cambium, with the exposed fresh inner wood announcing their occupancy. Typically, if a tree den is used year after year, they gnaw off a portion of bark each year, sometimes eating the old, scarred portion which, due to previous chewing, lacks cambium cells, indicating that this behavior is not for the purpose of obtaining nutrients. (photo: porcupine chewing near hollow tree den entrance)

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Eastern Chipmunks Up & Active

3-23-15  eastern chipmunk IMG_2146Eastern chipmunks typically emerge above ground in late March, at a time when most mature females are in breeding condition. It takes little time for nearby males to come courting. During their breeding period, females, for the most part, remain within their territory, whereas males explore within and outside of their territories in search of a receptive female.

Male suitors congregate on the site of a female in estrus and work out the hierarchy within the group. The top chipmunk wins the opportunity to breed with the female. During these dominance battles, the males vocalize, wave their upright tails from side to side, chase each other and fight. The dominant male then breeds with the female. She proceeds to mate anywhere from 10 to 30 times within about a six to seven-hour receptive period, not necessarily with the same male. All of this activity takes place within a week of when chipmunks come above ground, so keep your eyes peeled for those waving tails.

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Time To Take Down Bird Feeders

3-17-15 black bear-eating sunflower seeds  IMG_3607To prevent black bears from visiting backyard bird feeders, Fish & Wildlife Departments in New England recommend taking down birdfeeders from April 1st through December 1st. This year those dates are fairly conservative, as bears were visiting feeders after December 1st, and several have been seen frequenting feeders this month. The idea is to remove anything outdoors that would be of any interest to a bear which has just emerged from hibernation and is desperate for food.

Approximately 85% of a bear’s diet is vegetation. Before green shoots make an appearance in the spring, flower parts of aspen, willow, maple, ash and hazelnut, along with carrion, make up most of a bear’s diet. After losing 23% of its body weight during hibernation, a black bear finds protein-packed sunflower seeds very appealing. Make sure your garbage is secured, barbeques clean and pet food kept indoors, as well as your feeders. Keeping bears away not only prevents property from being damaged, but it also prevents bears from becoming nuisance animals that are habituated to food associated with humans, which often leads to the end of a bear’s life.

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Rodents Recycling

3-13-15  gray squirrel 001Bones, antlers, skulls, turtle shells – all are recycled relatively quickly by rodents seeking a source of minerals, particularly calcium and phosphorus. All rodents possess four incisors, two in the front of the upper jaw and two opposite these, on the bottom jaw. These incisors, unlike other teeth, never stop growing. By gnawing on hard objects such as bones, rodents keep their incisors paired down. If an incisor is broken or lost, the opposing incisor will continue growing in a circle, having nothing to grind against, causing the rodent to die of starvation or from having its brain pierced (through the roof of the rodent’s mouth) by the ever-growing incisor. In this photograph, a gray squirrel is obtaining minerals and sharpening its incisors on a moose skull that a human wedged into the crotch of a tree.

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Red Foxes Locating Prey

OLYMPUS DIGITAL CAMERADeep snow certainly presents challenges to predators – their prey is well hidden for the most part, and if they are to survive, they must compensate for not being able to see what they are hunting. Foxes are an example of how a predator survives in a winter like the Northeast has had. A red fox hunting for food is constantly listening for the sound of rodent feet under the snow, and when it hears them (they can hear a mouse or vole three feet beneath the surface of the snow) they leap up into the air and pounce on or near their prey with their front feet. Most of the time they are not successful, and come up empty-mouthed, but they usually succeed often enough to survive. Biologists are still working on understanding exactly how they do this.

Researchers in Czechoslovakia, watching foxes hunt in the wild, determined that a fox’s success seems to correlate with the direction in which it jumps. If the observed foxes jumped to the northeast they killed on 73 % of their attacks. If they reversed direction and jumped exactly the opposite way, they killed 60 % of the time. But in all other directions — east, south, west, or variations thereof— they were successful only 18% of the time. Jaroslav Cerveny, the Czech researcher, feels that foxes have a “magnetic sense,” and are capable of lining up the rodent sounds that reach their ears with the slope of the Earth’s magnetic field, and when this occurs, dinner is usually caught. (This theory has yet to be confirmed, but the likelihood that it is correct is great.) (Photo by Susan Holland, in the wilds of northwest Ontario)

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White-tailed Deer Scraping Bark

3-3-15  deer scraping2IMG_0490During the winter, white-tailed deer browse on the twigs, buds and bark of trees. Deer have incisors in the front of their bottom jaw, but none in the front of their top jaw, just a hard palate. They grip the bark with their bottom front incisors and scrape their jaw upwards, leaving behind grooves the width of their bottom incisors. Often there are frayed ends of bark at the top end of the groove, due to the deer having to use its hard palate and incisors, rather than two sets of incisors, to separate the bark from the tree. Favorite trees include red and striped maples, oaks, poplar, pines, hemlock, arborvitae and balsam fir.

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