The American mink is usually nocturnal, although it may sometimes also be active during the day (2) (5). Although it is an excellent swimmer and can dive to depths of five to six metres (2) (5), this species is thought to be only partially adapted to an aquatic lifestyle and does not have the underwater endurance needed to pursue prey in open water (5). The American mink is a skilled tree climber and can jump from tree to tree as well as being able to descend from trees head first (5).
A voracious and opportunistic predator, the American mink takes a variety of prey, including small mammals, fish, amphibians, birds, crayfish, crabs, insects and worms (2) (3) (4) (5). The exact composition of the diet depends on the location and season, and the American mink may also opportunistically hunt rabbits, squirrels, reptiles, bats and snails, as well as sometimes eating carrion. This species can be a significant predator of waterfowl and their eggs (5). The American mink often kills more prey than it can eat, storing the surplus to feed on later (3) (5).
The American mink is usually solitary and marks its territory with pungent secretions from anal scent glands (2) (5). It is also able to empty the contents of these glands under stress, possibly as a form of defence (5). This species sometimes digs its own burrows in which to shelter, but it more commonly uses abandoned muskrat or beaver houses, the burrows of other small mammals, or builds a den among tree roots, stones or brush piles (2) (3) (5). Its dens often have more than one entrance and are typically located close to water (2) (5).
Mating in this species occurs in the spring, usually between February and April, with births taking place in April, May and June (2) (4) (5). The female American mink shows delayed implantation, with the fertilised eggs not implanting in the uterus or developing straight away. Therefore, although the actual development of the embryo only takes 30 to 32 days (2) (5), the overall gestation period may last for 39 to 78 days (2), becoming shorter with increased temperatures (4) (5).
The female American mink gives birth to a single litter of two to ten young each year (2), although four or five young is more typical (2) (5). The young are born in a nest lined with fur, feathers and dry plant material (2), and are blind, naked and helpless at birth (2) (5). Their eyes open at four to five weeks old and they are weaned at five to six weeks. Young American mink begin to hunt at about eight weeks old, but remain with the adult female until the autumn (2) (5).
Female American mink reach sexual maturity at about 12 months old, but males are not mature until they are around 18 months old (2) (3). This species can potentially live for eight to ten years in captivity (2) (4) (5), but three to four years is more typical in the wild (2) (4) (5) (7). Potential predators of the American mink include birds of prey, owls, foxes, coyotes, lynx and otters (5) (7).