Lemmings: Never too small to make an impact

Refuge Notebook
Mercedes Bartkovich, a Career Discovery Intern at the Kenai National Wildlife Refuge, surveys lemmings near Barrow.

I was lucky enough to have the opportunity to travel up to Barrow and work as a wildlife tech on the Lemming Project. As an aspiring wildlife student from Georgia, this was an opportunity of a lifetime. Full of excitement, I immediately started doing research on lemmings. Through both my research and my actual experience up there, I discovered that lemmings play a big role in the ecosystem.


There are 22 species of lemmings, three of which are found in Alaska: the northern bog lemming (Lemmus trimucronatus), the North American brown lemming (Synaptomys borealis), and the northern collared lemming (Dicrostonyx groenlandicus). Our most abundant species in Barrow was the brown lemming. This lemming is found in the tundra areas of northern Alaska, and may possibly occur on the Kenai Peninsula. Not surprisingly, the brown lemming has a brown body with a reddish brown back and rump. Females and males weigh an average of 58g and 68g, respectively. Their diet consists of tundra grass, moss, lichens and roots.

The brown lemming, like most other lemmings, goes through 3- to 5-year population highs and lows. It is theorized that the survival of other wildlife may rely heavily on lemming populations, and for the threatened Steller's eider (Polysticta steller) this is vital information. The Steller's eider population that nests on the North Slope is one of only three breeding populations recognized worldwide; the other two are found in Arctic Russia. After breeding, Steller's eiders migrate further south to the waters along the southwest Alaskan coast to undergo a flightless molt. While most winter in the area they molted, others venture out and have been known to come to our very own Cook Inlet.

When the lemming population is booming, the survival rate of eggs that make it to adulthood rises significantly. This is because the Steller's normal predators that would be eating the eggs and destroying the nests get distracted by the abundance of lemmings. The lemmings substitute as a food source for the Steller's predators. The study in Barrow aims to learn more about this complicated predator-prey relationship before it is too late for the Steller's eider.

For two weeks, we surveyed six plots three times a day for five days per week. At each plot, we used 40 folding Sherman traps baited with a peanut butter-sunflower mix. As one can imagine, having to check 240 traps three times a day can be very time consuming and exhausting. The work resulted in us sleeping anywhere from 1 to 4 hours 3 times a day just to stay rested. Very soon this kind of sleeping schedule made me lose my sense of time; the constantly shining sun didn't do much to reduce this confusion either.

We lived in a small house with a group that was working with the Steller's eider project. All together there were 12 people in a 1 bathroom, 3 bedroom house living off of a tank of water a day. To say the least, it was an unforgettable experience.

At the end of our two weeks of surveying, we had a total of 144 brown lemming captures, representing 61 individuals. These results are similar to those of the previous year which resulted in 199 captures, representing 62 individuals. Since this is only the second year the study has been conducted, it will take at least a few more years to show how lemming abundance influences the productivity of Stellar's eiders.

It is interesting to see that such a small animal can play such a big role in another species survival. Here on the Kenai National Wildlife Refuge where I am working the rest of the summer, we also have the northern bog lemming. The bog lemming has grey brown fur with a light gray underside. It also has a patch of rusty colored hair by the ears. Although they are very close to the brown lemming in length, they actually weigh almost 30g less, averaging only 30g. Their diet is similar to that of the brown lemming with the addition of snails and slugs, and their main predators are owls, hawks and weasels. They are found in the wet forests, bogs, and the timberline areas in Alaska, and are known to be very covert. In previous studies they have been difficult to capture. The bog lemming also goes through a 3- to 4-year population cycle.

The bog lemming is only one of a several small mammals found on the Kenai Peninsula. A 1974 study by Todd Fuller found five species in addition to the bog lemming: the vagrant shrew (Sorex vagrans), masked shrew (S. cinereus), singing vole (Microtus miurus), tundra vole (M. oeconomus), and northern red-backed vole (Clethrionomys rutilus, newly revised as Myodes rutilus). A meadow vole (Microtus pennsylvanicus) was also seen during the survey but never caught. More recently, Thomas McDonough at the Alaska Department of Fish and Game found a few more species of small mammals: the montane shrew (Sorex monticolus), American pygmy shrew (Sorex hoyi) and nearctic shrew (Sorex sp.). These lemmings and voles and shrews play a vital role in keeping the ecosystem in balance, and without them we would be in trouble. I guess this just underscores that saying -- you can never be too small to make an impact.
Mercedes Bartkovich is a Career Discovery Intern this summer at Kenai National Wildlife Refuge. During the rest of the year, she's an undergraduate in the Warnell School of Forestry and Natural Resources at the University of Georgia. For more detailed information about the Refuge, you can check the refuge website at http://kenai.fws.gov or visit Facebook at http://www.facebook.com/kenainationalwildliferefuge.