Small mammals

 

When people speak of their interest in wildlife, they are nearly always referring to species (or groups of species) which are of special interest to them. Typical examples are songbirds, birds of prey, big game, small game, waterfowl, and predators. It is refreshing that occasionally someone will express an interest in snakes. It is extremely rare that small mammals are mentioned, perhaps because most people consider them to be undesirable vermin. Many of them are reservoirs of disease agents.

The term “small mammal” is quite broad. It includes mice, voles (most people include them as mice), shrews, chipmunks, red squirrels, flying squirrels, pocket gophers, moles, lemmings, etc. The only time I hear reference to small mammals is when snowy owls show up here. Then there is mention that there probably has been a crash of mice or lemmings in the arctic. However, the small mammal populations here are an important prey base for the hawks, owls, fox, pine marten, weasels, snakes, etc. that live here.

 

Although the public may not have concern for small mammal populations, many wildlife biologists do, even if their jobs are not directly related to either small mammals or their predators. I was primarily involved with big game, but I also set out lines of snap traps in both spring and fall for a number of years. I wanted to have at least some idea of what were the major species and to monitor major fluctuations of the populations.

One year I met an ecologist who was a small mammal expert with the Science Museum of Minnesota (at that time). He was very involved with monitoring small mammal populations on Superior National Forest lands in Cook County. He began his study here in 1983 and has continued through 2021. Few people realize that longterm studies like this are the only way to properly assess both short-term population fluctuations and long-term population trends. Even this study is not long on an ecologic time scale.

His study has yielded some very interesting information. The red-backed vole has about a 3-to-5-year population cycle, but the highs and lows of the cycles have been getting lower since about 2007. They are the most important prey species for furbearers and raptors in this area. During most of this study, rock voles had the most stable population level of any vole in the world. Yes, some biologists do keep track of research in their special field world-wide. None have been caught since 2011.

This study found the first smoky shrews in Minnesota and their numbers and range in Cook County have been increasing. However, restrictions imposed on his research by Minnesota D.N.R. have limited his being able to determine if their increases could eventually result in them being taken off the list of species needing special protection. Populations of several other species of shrews have declined.

Of special interest, he is also documenting the occurrence and spread of the white-footed mouse in Cook County. This mouse can be a major reservoir for the agent of Lyme disease, so he is having his specimens of this species assayed to determine if it is in them.

In 2021, Minnesota D.N.R. limited how many small mammals he could trap, how many nights a trap could be set, and in how many sites he could set traps. All of these can make the 2021 data more difficult (and in some cases impossible) to make confident comparisons with decades of data.

Worse yet, the person in D.N.R. who handles such permit applications declared that last year would be the last year of his study unless he uses live traps. Biologists who are familiar with small mammals in live traps are well aware that many individuals of some species die just from the stress of being in a live trap and/or being handled. Many species are not likely to enter live traps. On top of all that, some small mammals can only be identified as to species by examining their cheek teeth. They do not open wide and say “aaaah”. There are even some species which can only be identified by characteristics seen only on prepared skulls. So-called “live trapping” does not provide specimens (other than those that die because of it) that can be used in later specimen-based research or for epidemiological research. It is important to have specimens available for examination when a disease suddenly becomes a matter of concern.

My take on all this is that some in the portion of D.N.R. that handles permit applications have little knowledge of how to conduct scientific studies; or is it that they know little about small mammals. Which is worse? Neither is good. Severe limiting of how many can be taken eliminates being able to obtain meaningful information on such demographic statistics of populations such as population size, density, age structure, sex ratio, birth rate, and mortality rate. These are essential in assessing the health and status of a population.

This is the best small mammal study in this area (and perhaps the state) and has provided much biological information to the USDA Forest Service and to science. The importance of such information is not limited to just Cook County; much of it may pertain to most of northeast Minnesota. Now, D.N.R. can be blamed for likely ending it. I mentioned earlier that a number of species were declining; I feel it is important to find out if these declines are permanent or if (and when) these species might recover. Apparently, some in D.N.R. do not care about what the future holds for these species, or the predators that depend on them. The entire small mammal community is an excellent measure of the status of the environment. If the D.N.R. really cares, they would be encouraging more research, not hindering it.

I am very glad I did my studies when I did as most of them could not be done now because of the many D.N.R. policy changes that have been made.