What happens in the parks when the temperatures drop?
Author: Bob Lange, Natural Areas Steward
Over the last few weeks, winter has made it clear to us that it is here. We all have ways of enjoying, and sometimes even simply coping with the season. But for the world outside, our local plants and animals have some interesting ways of surviving the cold season.
Nearly all the deciduous trees in Portage County have finally shed their leaves, with some of our oaks still clinging onto a few. While the evergreens in the landscape stay just that, save for the ones that will dry out and shed their needles in someone’s living room in January, the deciduous trees have gone into a state of winter dormancy. However, it is not all that simple, let’s back up a bit. As daylight and temperatures decreased in the fall, trees began to slow and ultimately cease producing chlorophyll. With this came an end to photosynthesis, and greatly reduced respiration. It doesn’t end there, as many trees take advantage, at this point, to pull remaining nutrients such as nitrogen and carbon from the leaves. These nutrients are carried and stored away in roots and bark for new leaf and flower growth in the spring. Deciduous trees require a certain length of time exposed to low temperatures before the interactions of certain proteins trigger new growth. So, although we occasionally experience some fairly warm periods during winter, these plants are not fooled into starting spring too soon.
As for some of our local mammals, there are several ways these critters survive and thrive through the winter season. By the end of November, raccoons have developed a winter coat, as thin hairs have been replaced with heavier underfur. They have also built up a heavy fat layer as reserve. Raccoons are not hibernators, yet they are not exactly fully active in winter. They do continue searching for and consuming food as weather allows. But, when severe cold spells set in, Raccoons will climb into dens and sleep for several days until weather breaks. Oftentimes, metabolism slows and insulin production increases, helping the animal to conserve energy until the weather is suitable to resume foraging. When spring finally arrives, most raccoons seen in the wild will appear quite thin, as much of the reserved fat has been used up.
Ground hogs are a different story, as they are considered one of the true hibernators in Ohio. Individuals spend the summer and fall eating heavily. By the start of November, activity is greatly reduced, and many begin to den up in burrows for hibernation. During this dormant state, the animal is in a deep sleep as body temperature, heart rate and metabolism are drastically reduced. For ground hogs, this means a drop in body temperature from 90F to nearly 40F, and a heart rate plunge from over 100 beats per minute to only 4! Hibernation for ground hogs typically lasts until February or March.
Lastly, we have the river otter, an animal once extirpated from the state of Ohio that is now again present in over two-thirds of our 88 counties. Winter is no time of rest for these animals, as they remain active and on the go year-round. Although river otters are generally nocturnal during other times of the year, winter finds them active more often during the daylight hours. River otters develop a much thicker coat for winter to guard against exposure to extremely cold conditions. This includes diving into frigid water beneath the ice of ponds, rivers and wetlands foraging for food. Crayfish are a favorite of river otters, with mussels, snails and fish also part of their diet. With food occasionally in short supply during winter, an individual may cover miles of stream through the season to survive.