2017-09-09 / Columnists

Nature Notes

Beavers Enjoy Making Island Home
By Patricia Martin

For the last six or seven years, many people who live on the Island or visit Mackinac have been following the exploits of the family of beavers that built a lodge just off the shore near the east point of the harbor in what is locally referred to as “The Cove.” Through the years, the size of the lodge has grown and the number of beavers has gone up and down, but the fascination for people has not waned. So I thought I would share with you some of the wonderful photographs taken by Nancy May, who is an avid beaver watcher, and give you an update on our furry friends, along with a few interesting facts.

The scientific family of the beaver, the Castoridae, is very small, with only one single living genus and two species worldwide. The American beaver (Castor canadensis) is our familiar beaver and its Eurasian counterpart is Castor fiber. These are the two largest rodents in temperate climates and they are second only to the South American Capybara in size. Adult American beavers have a length of 35 to 47 inches, with flat, leathery tails of 12 to 16 inches. They have large heads, about five inches long. They weigh 26 to 60 pounds. They have two types of fur: silky guard hairs on the outside, which they oil to waterproof; and downy fur underneath, which keeps them warm in the cold water. They are noted for their large, strong incisors, whose front surface is covered with tough, dark-orange enamel; and the backs of those same incisors are white or ivory. It is funny that in all the cartoons picturing beaver, they are shown as rather bucktoothed, their front teeth always showing and often portrayed as being white, when it actually is uncommon to see much of their teeth at all.

A beaver is shown here on a lodge just off the shore near the east point of the harbor on Mackinac Island. (Photographs by Nancy May) A beaver is shown here on a lodge just off the shore near the east point of the harbor on Mackinac Island. (Photographs by Nancy May) The pelts of these animals were the backbone of the fur trade at Mackinac for several centuries and, because of trapping and land clearing, their numbers were greatly depleted until the early 1900s, when the regulation of the fur trade allowed beaver populations to recover. Beavers are now common in the northern Great Lakes Basin, but less so in the southern areas that are heavily urbanized or farmed.

An adult and juvenile beaver swim near the Island. An adult and juvenile beaver swim near the Island. Most people think of beaver building dams across streams and rivers. This construction is only done if the water is too shallow. It allows them to make a permanently flooded area or pond, which to them is more hospitable. They also will live in burrows under the banks of faster-moving rivers, or in muddy pond banks, or they will build lodges (not dams) in lakes bordered by young forests that contain aspen, willow, and/or alder, which is why the area near Mission Point is a good spot for them. The beaver on Mackinac built their lodge in a part of the shore where, more than 40 years ago, the bottom was dredged and riprap was installed in preparation for a marina (during the Moral Re-Armament and Mackinac College days). The marina never got built, but the protected area remains. Adjacent to the cove, there is an area owned by the Michigan Waterways Commission. It was full of young quaking aspen, balsam poplars, willows, and canoe birch. A couple of years ago, the young saplings were all cut to a height of about two feet and only a few large trees remained. Because of the cutting, the beavers have had to take down the larger trees that were left or go further afield to find food, which has caused some problems.

Last fall, the lodge at the cove was home to eight beavers, made up of several generations. Early this spring, only five were spotted. Some may have not made it through the winter and others may have found other places to live on the adjacent islands or on other parts of Mackinac. There has been beaver activity and beaver have been spotted in the west side of Haldimand Bay and in various places around the Island. As far as I have been able to ascertain, however, no other lodges have been seen. The five beaver spotted by the cove lodge this spring appeared to include “Mom and Dad,” one two-year-old beaver and two one-year-old beavers. A bit later in the spring, three kits were seen, although someone thought they might have seen four young ones. At one point this summer, it appeared that the mom had left and one tiny beaver, about six to eight weeks old, seemed to be on his or her own. Several Island residents began to bring willow branches down to the kit, which they nicknamed “Willow,” and she began taking branches from them and eating. After a while, it was noted that one of the yearlings was around and appeared to be bringing branches to the kit, or kits, in the lodge.

One evening, the mom suddenly reappeared on the scene in a rather dramatic fashion. Some people were feeding Willow on the shore near the lodge. A couple was walking their dog and they let him go swimming in the cove. The dog headed for the kit, which quickly headed for the lodge. Out of nowhere, a large adult beaver (Mom) appeared. People along the shore were trying to get the dog’s owner to call the dog back, but to no avail. The dog and the beaver began to go at each other. One observer shouted something like, “You’d better get your dog or the beaver will chew him up.” The dog’s owner finally jumped into the cove and grabbed the dog and pulled him to shore. The mom beaver circled the lodge four times and then stood on the shore on its hind legs scratching its belly, sort of like a gorilla pounding its chest. If you walk your dog along the lake, it would probably be a good idea not to let it go swimming by the cove.

Recently, it has been reported that there are at least two adults and two kits living in the lodge and people are still supplying them with branches, some from as far away as Bois Blanc Island.

One question people have been asking about the lodge is the way beavers deal with the changing water levels. If you remember, a few years ago, the water was quite a few feet lower than it is now. When beavers build a lodge, they have an underwater entrance leading to an area where they can dry off and then go into an upper chamber to hang out. If they need to “raise” the lodge, they add more building material to the outside and then clear out more of the inner material. Of course, if they build a dam on a stream and the water gets too high, they merely remove part of the dam and let the water flow out.

I hope you have a chance to get down to the cove in an evening to observe these furry Island residents. Remember not to get too close to the lodge or the beaver: we’ve had reports of kids throwing rocks at the beaver and even going out to the lodge to cause trouble.

Trish Martin is a year-around resident of Mackinac Island, has earned a master’s degree in botany from Central Michigan University, and owns Bogan Lane Inn

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