The Rise and fall of Wildlife Populations

by Dave Hanks

There are only a few wildlife species whose populations fluctuate at regular intervals. The Lemming cycle peaks at four years. Ruffed Grouse increase for four to six years and then decrease at the same rate. The relationship between Lynx and Snowshoe Hare is fairly constant – the cats increase as the hares become more abundant and they in turn reverse the cycle.

However, the fluctuations of most species depend on the weather and food supplies. It is very important to each species that population numbers stay in balance with the available food sources. HIGHLINING is when trees are missing limbs as far up the tree as animals can reach. This is a sure sign of too many individuals utilizing the resources. If this continues, the area may become permanently damaged and unable to support the number that it once did. The Elk population in Yellowstone Park was putting the park’s vegetation in serious straits – hence, the introduction of the wolf. Whether that was a good or bad decision, remains to be seen.

There are more young born each year than the environment can possibly support. Just think of the implications of the following: two rats and their offspring would yield 350 million in 3 years, trout lay hundreds of eggs, and rattlesnakes have 15 to 20 young each year. Even an elephant would raise 6 offspring over a 75 year period, and even that would put undue stress on the available resources.

The cruel fact is that most offspring either die or are food sources for predators. Cottontails lose 80 % of their population each year. If they all lived into the winter, none would survive to greet the new spring. Not only does crowding damage the vegetation, it damages the health of the animals.

Natural predators are a must to increase the vigor of both the habitat and the prey. Where predators are absent, controlled hunting is a necessity.

The adaptable Coyote – A major predator on rodents

The Deer Mouse: Food for Many

by Dave Hanks

You have probably seen a Coyote stalking along in the tall grass, pausing, and then leaping skyward in an exaggerated pounce. The canine is catching rodents and Deer Mice are among the most plentiful. This white-bellied, white-pawed, and white-tailed mouse is eaten by owls, hawks, snakes, and other small meat eaters. The mouse does not hibernate and a Great Horned Owl can hear the mouse running under the snow and correctly gage where to pounce to make the kill.

Because it is preyed upon so heavily, reproduction at a rapid rate is essential.The female mouse will produce up to seven litters or more when feeding conditions are favorable. Her gestation lasts from 21 to 24 days and she comes back into estrus immediately (postpartum) upon giving birth. You could say that she is continually pregnant. The nest is a hollow ball of grass on the ground, and the new born in it are hairless, wrinkled, pink, and with their eyes not opened. The mother will transport the young to new locations, either in her mouth, or by the babies clinging to her nipples.

Deer Mice are poor climbers and so their life is spent on the ground where they dine on seeds and insects. They especially prefer weedy or tall grassy areas and the resulting seeds and cover. There is a danger that can come to humans from contact with this mouse’s droppings. They may contain a deadly virus which causes HPS (Hantavirus Pulmonary Syndrome).

There are over 100 sub-species of this rodent. Their white-colored undersides will differentiate them from the mouse we are most familiar with – the House Mouse. Deer Mice are nocturnal. The one pictured alerted us to its presence – we could hear it chewing away just outside our camper door.

A Deer Mouse gnawing on our birdseed in the middle of the night

A Deer Mouse gnawing on our birdseed in the middle of the night

The Coyote: Nature’s Trickster

This is one of nature’s most cunning and most adaptable creatures. While other species have decreased, since the coming of white man, the Coyote has increased. They are so adaptable that they can actually be found in some cities. There are many Indian legends about them and about their tricky ways. Their scientific name (Canis latrans) means “barking dog”.

This intelligent carnivore has a wide range of vocalizations from barks to yelps, which are most heard at dusk, nighttime, or in the early morning. These calls help keep the group together. The tail is also used as body language. Different positions mean different things and a horizontal, bristled tail is a signal of aggression. Coyotes can be told from wolves by their smaller size, and when running they hold their tail down. Their tracks are also different than dogs – their front paw tracks are larger than their hind paw tracks.

They form loose family groups and will pair for several years or even for life. The den is either a burrow or in a rock crevice and its mouth can be from 5 to 30 feet wide. Mating takes place in February to April and after a 60 day gestation, 1 to 19 pups are born. As tremendous reproducers, it’s no wonder that they are so adaptable. The young leave their parents at 7 to 8 months.

Coyotes are opportunistic and will eat almost any flesh, including carrion. Usually solitary hunters, they will occasionally use others to run relays to tire the prey out or to lay in ambush. Other animals, such as Badgers, may unwittingly become victims, as the Coyote often steals their kill from them.

This canine can run up to 30 miles per hour and is a strong swimmer.

(Resting in the snow and allowing my wife a photograph)