Two Rare Mammals Going Unstudied
Spring 2015
By: Dr Pat Rusz, Director of Wildlife Programs
Two species of Michigan’s small mammals--the least shrew (Cryptotis parva) and the prairie vole (Microtus ochrogaster)—have been on the state’s threatened or endangered species lists for more than 25 years. Yet, they have gone largely unstudied.
Michigan is at the northern edge of the range of the threatened least shrew, but it was found throughout Southern Michigan until it mysteriously disappeared in the 1950s. The least shrew doesn’t seem to have specific habitat needs as it was historically found in the lower three tiers of Michigan counties in upland grasslands, abandoned fields, wet meadows, orchards, and a variety of forested areas. Cold weather, genetic isolation, and intensive agriculture may have all taken a toll.
The least shrew is one of the smallest of Michigan’s seven shrew species with a body length of around 3 inches and a tail of just over one-half inch. Our state’s other shrews are larger or have longer tails. Normally solitary, the least shrew will share communal nests with several dozen of its kind in winter. It is fairly prolific, capable of having 3 to 4 litters of 3 to 6 young each year. It feeds mostly on invertebrates, but will kill any small animal it thinks it can.
The last least shrew found in Michigan was in 1960 in Clinton County, but there have been only a few brief attempts to trap them where they have been found historically. Some biologists believe the tiny mammals are still around and could show up in studies of owl pellets or detected by intensive trapping in grasslands.
The prairie vole is on the state endangered species list and was historically found in the southeastern Lower Peninsula. As its name implies, this species favors grasslands and was once found in hay fields as well as native prairies. It is about 4-1/2 inches long with a tail of about 1-1/2 inches and makes narrow surface runways. Michigan also has meadow voles and woodland voles that are similar in appearance.
Unlike forest mice and shrews, prairie voles eat mostly seeds and the leaves and stems of grasses and other vegetation. One curious aspect of prairie vole behavior is its complex social system. Many prairie voles form mated pairs for life. That’s unusual for animals that live just one to two years. The pairs raise the pups together, groom each other, and even cuddle. Incredibly, if one dies the partner stays alone for the rest of its life.
Prairie voles that don’t pair up live in communal groups in which usually the oldest female is the only one to bear young. This dominant female will emit pheromones that inhibit the other females’ ability to mate. The communal groups and the mated pairs will often come together in winter, then separate during the breeding season in spring through fall.
The prairie vole had not been documented since 1962 (then in Berrien County), but was recently found in 2006 in Kalamazoo County. As in the case of the least shrew, there hasn’t been much effort to determine whether it still exists in our state.
By: Dr Pat Rusz, Director of Wildlife Programs
Two species of Michigan’s small mammals--the least shrew (Cryptotis parva) and the prairie vole (Microtus ochrogaster)—have been on the state’s threatened or endangered species lists for more than 25 years. Yet, they have gone largely unstudied.
Michigan is at the northern edge of the range of the threatened least shrew, but it was found throughout Southern Michigan until it mysteriously disappeared in the 1950s. The least shrew doesn’t seem to have specific habitat needs as it was historically found in the lower three tiers of Michigan counties in upland grasslands, abandoned fields, wet meadows, orchards, and a variety of forested areas. Cold weather, genetic isolation, and intensive agriculture may have all taken a toll.
The least shrew is one of the smallest of Michigan’s seven shrew species with a body length of around 3 inches and a tail of just over one-half inch. Our state’s other shrews are larger or have longer tails. Normally solitary, the least shrew will share communal nests with several dozen of its kind in winter. It is fairly prolific, capable of having 3 to 4 litters of 3 to 6 young each year. It feeds mostly on invertebrates, but will kill any small animal it thinks it can.
The last least shrew found in Michigan was in 1960 in Clinton County, but there have been only a few brief attempts to trap them where they have been found historically. Some biologists believe the tiny mammals are still around and could show up in studies of owl pellets or detected by intensive trapping in grasslands.
The prairie vole is on the state endangered species list and was historically found in the southeastern Lower Peninsula. As its name implies, this species favors grasslands and was once found in hay fields as well as native prairies. It is about 4-1/2 inches long with a tail of about 1-1/2 inches and makes narrow surface runways. Michigan also has meadow voles and woodland voles that are similar in appearance.
Unlike forest mice and shrews, prairie voles eat mostly seeds and the leaves and stems of grasses and other vegetation. One curious aspect of prairie vole behavior is its complex social system. Many prairie voles form mated pairs for life. That’s unusual for animals that live just one to two years. The pairs raise the pups together, groom each other, and even cuddle. Incredibly, if one dies the partner stays alone for the rest of its life.
Prairie voles that don’t pair up live in communal groups in which usually the oldest female is the only one to bear young. This dominant female will emit pheromones that inhibit the other females’ ability to mate. The communal groups and the mated pairs will often come together in winter, then separate during the breeding season in spring through fall.
The prairie vole had not been documented since 1962 (then in Berrien County), but was recently found in 2006 in Kalamazoo County. As in the case of the least shrew, there hasn’t been much effort to determine whether it still exists in our state.
Prairie Vole
|
Least Shrew
|