Incidence of Mink, Mustela vison, and River Otter, Lutra canadensis, in a Highly Urbanized Area

Abstract: Mink (Mustela vison) frequently inhabited or traversed a residential, business, and industrial part of the Twin Cities, Minnesota, with little water or natural vegetation. At least one River Otter (Lutra canadensis) also resided on a small pond on a golf course in the area for several winter months.

Key words: Mink, Mustela vison, River Otter, Lutra canadensis, urban wildlife, Minnesota

Urban wildlife, including carnivores and raptors, is common. Where large marshes or other extensive waterways exist in cities and suburbs, Muskrats (Ondatra zibethicus), Mink (Mustela vison), and even Beavers (Lutra canadensis) can be expected. Such areas are really islands of suitable habitat in seas of urbanization. However, this note documents Mink and an otter inhabiting an urban area without such natural habitat.

The study area is a region 3 km² located in Lauderdale, Minnesota (Ramsey County), along the border between the cities of St. Paul and Minneapolis. It has long been a heavily populated residential, industrial, and business area interlaced with paved streets, highways, and parking lots, and a golf course. The only nearby natural vegetation is an embankment up to 15 m wide along each side of a railroad track. The only water is a pond of 1.1 ha (Walsh Lake) surrounded by a golf course and residential yards. A storm sewer feeds the pond. The nearest natural Mink habitat is 3.3-5.7 km away, with houses, yards, businesses, and six to eight lanes of interstate highway intervening. The nearest extensive waterways where otters might be expected are 3.5-6.0 km away, also separated from the area by the same type of surroundings.

Over a period of 4 years, I found three road-killed Mink in this area and tracks in the snow of a Mink frequenting the golf course pond (Table 1). The dead Mink were 0.25, 1.00, and 1.50 km from the pond. The otter used the pond from at least 26 December 2002 through 11 April 2003 based on extensive tracks, slides, and feeding holes through thin ice. There was neither natural vegetation nor waterway between the pond and the dead Mink. Wherever the Mink and otter came from, they had to have passed through yards, lawns, streets, highways, and parking lots, ditches, or possibly sewers.

The pond, which has a shoreline of about 375 m, was much smaller than areas usually reported to be inhabited by Mink or otters. In North America, reported mean linear home ranges for Mink varied from 5,250 to 7,519 m (Whitman 1981; Stevens et al. 1997). Average home range sizes ranged from 282 to 1,141 hectares (Arnold and Fritzell 1987; Eagle 1989). Thus the pond probably constituted only a small part of one Mink's home range, despite the fact that there was no vegetation or waterway connecting it with any other natural Mink habitat. Otters roam over areas 8-78 km in extent (Melquist and Hornocker 1983).

These findings document the ubiquity and great adaptability of Mink and otters.