Marsh Rice Rat - Behavior and Ecology

Behavior and Ecology

Marsh rice rats are active during the night and for this reason are rarely seen, although they may be among the most common small mammals in part of their range. They will build nests of sedge and grass, about 13 cm (5 in) large, which are placed under debris, near shrubs, in short burrows, or high in aquatic vegetation. They may also use old nests of marsh wrens (Cistothorus palustris), red-winged blackbirds (Agelaius phoeniceus), muskrats (Ondatra zibethicus) or round-tailed muskrats (Neofiber alleni). Marsh rice rats sometimes make large runways or dig burrows. They are accomplished and willing swimmers, easily swimming for more than 10 m (30 ft) under water, and will often seek safety in the water when alarmed. Rice rats in the Florida Keys occasionally climb in vegetation, but never higher than 90 cm (3 ft). Marsh rice rats are very cleanly and extensively groom themselves, perhaps to keep their fur water-repellent. They are aggressive towards conspecifics and emit high-pitched squeaks while fighting. In dense vegetation, the perceptual range (the distance from which an animal can detect a patch of suitable habitat) of marsh rice rats is less than 10 m (33 ft). When released outside of their natural wetland habitat, marsh rice rats generally move either upwind or downwind (anemotaxis), perhaps in order to move in a straight line, which is an efficient strategy to find suitable habitat.

Many animals prey on marsh rice rats. The barn owl (Tyto alba) is among the most important; one study found that 97.5% of vertebrate remains in barn owl pellets were marsh rice rats. Other predators include birds (marsh hawks, Circus cyaneus; and barred owls, Strix varia), snakes (cottonmouth moccasins, Agkistrodon piscivorus; and others), alligators, and carnivorans (raccoons, Procyon lotor; red foxes, Vulpes vulpes; minks, Neovison vison; weasels of the genus Mustela; and striped skunks, Mephitis mephitis). Many parasites have been recorded on the marsh rice rat, including various ticks and mites, lice, and fleas among external parasites and many nematodes and digeneans, a pentastomid, and several coccidians among internal parasites (see parasites of the marsh rice rat).

Periodontitis, a bacterial disease affecting the jaws, is particularly virulent in marsh rice rats; the animal has been proposed as a model for research on the disease in humans. The identity of the bacterial agent remains unknown. Vitamin E, fluoride, and iodide protect against bone loss associated with this disease in the rice rat and a high-sucrose diet increases the severity of periodontitis. A case of kyphosis has been observed in a North Carolina marsh rice rat.