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Maryland's Mustelids

Written by Robert Colona
Furbearer Project Leader

Maryland's largest family of furbearers is also one of it’s least understood. Mustelids are a group of mammals that possess two anal glands, which exude or forcefully project a volatile noxious substance that is used as a territorial marker or as a defensive response. Virtually everyone is familiar with striped skunk (Mephitis mephitis) and their extremely offensive odor. However, few people probably realize that long-tailed weasel (Mustela frenata), mink (Mustela vison), fisher (Martes pennanti), and otter (Lutra canadensis) are closely related to skunks.

Although fairly elusive and rarely seen, mustelids are widely distributed and fulfill extremely important roles in local ecosystems. With the exception of skunks, all are predators and feed predominantly on animal matter. While skunks are also predatory, they also feed extensively on insects and some plant materials.

In addition to their ecological value, mustelids are also a renewable economic resource for many of Maryland’s citizens. Furbearers can be loosely defined as mammalian species that can be legally harvested for their pelts. These pelts are then normally sold to be fashioned into fur garments or other utilitarian items. Of the seven species of mustelids that currently occur in Maryland, five are legally defined as furbearers and are subject to regulated harvest. The description, status and distribution of these five species is as follows:

Long-Tailed Weasel (Mustela frenata)

Long-tailed weasel are relatively small animals, with slender and elongated bodies. Body sizes range from 11-17in., and 5-16 ounces. Males tend to be significantly larger than females. Overall pelt coloration is brown with a yellowish white neck and underside. In the Northern United States, long-tailed weasel molt in the fall and their pelage becomes totally white and remains that color until they molt again in the spring and it returns to brown. In the mid-Atlantic region (including Maryland) and farther south they remain brown throughout the year.

Weasel feed extensively on mice and other small mammals, but will also utilize birds, rabbits and amphibians when available. Long-tailed weasel can live in a fairly broad range of habitat types. In Maryland marshland, woodlands, intermittent grasslands and rocky outcrops receive utilization and they are sporadically distributed throughout the state.

Mink (Mustela vison)

Mink are small cylinder shaped animals ranging from approximately 19-30 in., and 1.5 - 4 lbs. Males tend to be 1.5 times larger than females. Their fur is short and glossy and can vary from light brown to almost black. They also possess white chin and/or chest patches that vary in size from individual to individual. Mink are semi-aquatic and utilize all types of quality wetlands within their range. They frequent suitable bodies of water ranging from fresh and brackish marshes to farm ponds and fast moving trout streams. Dependent on seasonal availability, mink prey upon birds, small mammals, fish, amphibians, and crustaceans.

Mink are common from Garrett County eastward to the western shore of the Chesapeake Bay and are found infrequently on some of the larger islands in the Bay proper. For unknown reasons, mink are absent from the Eastern shore and many coastal regions in the eastern United States.

Striped Skunk (Mephitis mephitis) 

This ubiquitous animal is almost universally recognized by sight and smell throughout it's range in the United States. They are similar in size to domestic cats, ranging in length from 20-30 in. and 4-10 lbs. in total weight. The base pelt color is typically black, with a white patch on the head and two white stripes extending laterally down the torso and ending with a white stripe on the tail. There is a great deal of natural variation in the pelage of striped skunks and individuals may infrequently be almost totally black or white. They feed extensively on insects, but will also utilize plant material, small mammals, birds and bird eggs when locally or seasonally abundant. Striped skunks are distributed statewide and can be found in virtually all habitat types. Highest densities are normally found in mixed farmland / woodland areas and lowest densities are found in marshland or beach land habitats.

The characteristic odor of skunks results from butylmercaptan, which is a sulfurous compound containing sulfuric acid. This compound is normally released from the anal sacs when the skunk is alarmed or threatened. Animals that are sprayed by skunks often experience temporary loss of vision, respiratory distress, nausea, and burning skin.

Fisher (Martes pennanti)

Fishers have elongated bodies resembling a large weasel with a large bushy tail. They range in size from 29-48 in., and weigh 4-13 lbs.; with some large males approaching 20 lbs. Males are typically at least 20% larger than females. Dependent on the time of the year and sex of the animal, fisher pelts can range from dark reddish brown to a grizzled black. This grizzled appearance results from tricolored guard hairs. Males tend to be more grizzled than females, and females possess longer, silkier fur. Fisher diets include squirrels, rabbits, small mammals, birds, and surprisingly porcupines (Erethizon dorsatum). Fisher are arboreal (spend time in trees), therefore habitat types utilized by them include a large wooded component. They can be found in or in close association to mixed forests and small forest openings and farm fields.

Historically fisher populations in eastern North America extended from Canada through the Northeastern states and followed the Appalachian mountains as far south as Tennessee. By the early 1900's the fisher had been extirpated from Maryland and other central and southern Appalachian states.

During 1969, the West Virginia Division of Wildlife Resources initiated a fisher reintroduction project. 23 fishers were obtained from New Hampshire and released at 2 sites in West Virginia. 15 animals were released on Canaan Mountain in Tucker County, and the remaining 8 animals were released near Cranberry Glades in Pocahontas County. By 1972, West Virginia’s introduced fisher population had expanded sufficiently to support a legal harvest season in West Virginia.

Otter  (Lutra canadensis)

River otter display typical weasel- like features. Their bodies are relatively long, streamlined and include an elongated flattened tail. Legs are short and feet are webbed. Total length varies from 35 to 55 inches and weights range from 12 to 35 lbs. Pelt coloration includes various shades of brown and is characterized by short, dense and glossy fur. River otter feed predominantly on fish, but will also feed on crustaceans, mollusks, amphibians, reptiles and other small animals when locally abundant. River otter are semi-aquatic and utilize most healthy wetland systems. In Maryland they occupy wetlands ranging from trout streams to tidal marshes.

Prior to 1990 otter were distributed at varying densities throughout the state with the exception of Garrett and Allegany and western Washington counties. At that time, otter were absent from this 3 county region. During the early to mid 1990's the Department of Natural Resources initiated a project to reintroduce otter to the mountainous portion of western Maryland. Historically, otter had been extirpated from this region during the 1800's. Otter were trapped from resident donor populations on the eastern shore of Maryland by Departmental personnel and were transported to western release sites. Initial project efforts focused on the Youghiogheny river drainage in Garrett County. Subsequent releases also occurred in smaller drainages within the county. After self-sustaining, viable populations had been restored in this county, efforts were then shifted to Allegany County.

As a result of successful reintroduction efforts, otter are now distributed statewide. Highest population densities occur in the coastal plain adjacent to the Chesapeake Bay. As you proceed westward from the Bay, population densities decrease incrementally until the reach their lowest level in Allegany County. Otter populations in Garrett County have increased dramatically and can now be considered common.