An online resource based on the award-winning nature guide

Mice

American Crow Bills Used As Tools

1-13-16  American crow tracks 147American crows obtain most of their food on the ground as they walk along in search of seeds, insects, frogs, snakes, bird nests and small mammals. Their hunting techniques are varied and most involve the use of their bill. In search of invertebrates, crows will probe the soil with their bill, flick aside leaves, dig in the soil and even lift cow paddies. They fish for tadpoles and dig nearly an inch deep with their bill for clams. In winter, their foraging continues and as these tracks indicate, when the snow is only a few inches deep they will walk around and around in a given area, probing tufts of grass for hibernating insects, mice, voles, or any other form of life these opportunists find.

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Rodent Incisors

12-3 woodchuck skull IMG_7187Rodents have two pairs of incisors that oppose each other; two in the front of the upper jaw and two in the front of the lower jaw. These four teeth never stop growing, and thus have to be constantly filed down. (Squirrel incisors grow about one-half inch a month.) While nipping herbaceous plants and cutting into bark help do this, it isn’t enough to significantly wear down the teeth. When mice, beavers, woodchucks and other rodents nip or gnaw food, they move their jaws in such a way that these two pairs of teeth grind against each other. Most rodents have hard orange enamel on the outer side of their incisors (woodchucks are our only rodent with white enamel), and softer dentine in the back. When the incisors grind against each other, the dentine wears away faster than the enamel, creating a sharp, chisel-shaped edge to the incisors. This, more than anything else, keeps the growth of rodent incisors under control, just as a nail file keeps our nails from getting too long.

If a rodent breaks an incisor, there is nothing to wear down the opposing incisor. The tooth opposite the missing incisor will continue to grow unchecked in a circle until it causes the death of the rodent, either by piercing its skull or by preventing the animal from being able to eat. In the pictured woodchuck skull, the lower left incisor has broken off, allowing the upper left incisor to grow through the woodchuck’s palate and into its brain.

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Deer Mice And The Rigors of Winter

2-5-15  deer mouse 022Even though Deer Mice are active year round, we don’t often see them, as they are active from dusk until dawn. During the winter, when it’s very cold, they commonly resort to short periods of torpor (4 to 9 hours) during the day to conserve energy. While torpid, their body temperature may fall to 55° F. from a normal temperature of 98°F.

When active, Deer Mice travel both under and on top of the snow. When travelling under the snow, they tunnel through it or use tunnels created by other small mammals. When travelling on top of the snow, their tracks, and often the drag mark from their tail, are evident. The pictured Deer Mouse was found curled up, frozen, at the end of a very lengthy trail of tracks and tunnels that ran over and through woods. Where the tracks began there was a slight depression in the snow (no tunnel, no tracks), indicating that the mouse might have fallen from the air after escaping from the talons of a bird of prey.

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The Effects of An Icy Crust on Wildlife

1-19-15  ruffed grouse snow cave IMG_8590This winter has brought us several storms that have ended in rain and were followed by plummeting temperatures. Just a few inches down into the powdery snow on top of the ground there is a ¼”-thick crust, and if you dig down several more inches, there is a second layer of ice, roughly 1/8”-thick. When a thick, icy layer of crust forms, it can have a dramatic effect on the lives of wildlife both above and below it.

Some animals are relatively unaffected by the presence of a crust but many predators and prey are significantly helped or hindered by it. Ruffed grouse cannot seek overnight shelter from the bitter cold and/or predators by diving into a foot of soft snow and creating a snow cave (see photo). On the other hand, small rodents have a distinct advantage — mice and voles have several layers of ice between themselves and hungry coyotes, foxes and owls. Snowshoe hares lose the advantage they usually have on deep, soft snow — “snowshoes” that keep them on top of the snow when the bobcat or fisher chasing them has to flounder through it. Turkeys don’t have the strength to dig down through one thick crust, much less two or more, in order to reach hidden acorns. If a deer is being chased, its pointed hooves will break through the crust, slowing the deer down, whereas the crust may well support a lighter predator, allowing it to outrun the deer. Red squirrels have to work much harder to reach their cached winter cones and to create tunnels.

What is a mere inconvenience to us humans literally is costing as well as saving the lives of wildlife this winter.

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Coyotes Feeding on Deer Carcasses

12-22-14 deer carcass 394Ninety percent of a coyote’s diet is animal matter, including creatures as varied as meadow voles, mice, muskrats, raccoons, beetles and grasshoppers — basically, anything it can outrun. Coyotes have the reputation as major predators of deer. While research confirms that deer (and rabbits) comprise a good portion of a coyote’s diet in the Northeast, the majority of the deer that coyotes consume is scavenged as carrion (see photo). Because they cannot move as fast as adult deer, fawns are more vulnerable to coyote predation.

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Barred Owl Story in the Snow

2-17-14  barred owl prints 013These beautiful impressions in the snow tell the story of a Barred Owl diving feet first after prey, most likely a vole or mouse. The fact that there are no rodent tracks on the surface of the snow tells you that the mouse or vole was well hidden in its tunnel under the snow at the time. Apparently the owl’s talons did not reach their target (at least, no blood or rodent remnants), and the owl continued to plow through the snow in repeated attempts to capture its prey before taking flight.

The presence of facial discs (feathers in the shape of a funnel around each eye that direct sound waves towards the owl’s ear) plus the differing size and asymmetrical placement of an owl’s ear openings allow the owl to discern the direction a sound is coming from, how far away it is and its height relative to the owl – even in the dark or under the snow! The exceptional hearing ability of owls, particularly those in the genus Strix (which includes Barred and Great Gray Owls), enables them to plunge into the snow and often successfully capture prey, sight unseen. (Species of owl was determined by wing length. Thanks to Rob Anderegg and Jennifer Grant for photo op.)

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Hide & Seek: Voles & Foxes

1-9-14  hide and seek-fox & vole IMG_2735Unlike wolves, which hunt in packs and often take down prey larger than themselves, red foxes are solitary hunters and as a result often catch prey much smaller than themselves, such as mice and voles. During the winter, mice and voles become more active during daylight hours because much of their time is spent under the snow, where they remain hidden from view. Consequently, in winter you’re more likely to see a fox hunting during the day than in the summer. Whenever it’s hunting, night or day, a fox depends heavily on its acute sense of hearing. It is most sensitive to lower noises such as the rustling and gnawing sounds that small animals make as they move through vegetation or feed on seeds, buds and twigs. Foxes can locate these sounds several feet away, to within inches of their true location, under three feet of snow. Recent research suggests that they may also use the magnetic field to help them locate prey. (photo: red fox & meadow vole tracks)

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