A nocturnal species (1) (5), the cotton deermouse is known to take refuge in ground holes and hollow tree cavities during the day (1), even taking advantage of gopher tortoise (Gopherus polyphemus) burrows in south-central Florida (1). As well as being an agile climber (2) (3) (4) (5) (7), the cotton deermouse swims and dives well (2) (3) (7).
The cotton deermouse is one of the most numerous rodents in the south-eastern United States, with its high reproductive rate ensuring a substantial population size (5). This nocturnal species (1) (5) is known to breed throughout the year in many parts of its range (1) (4) (5) (7), but reproduction appears to decline during the hottest (3) (4) (5) (7) and coldest months (5) (7). In the more southern parts of its range, the cotton deermouse breeds mostly from autumn through to the spring (3), whereas in the more northerly parts of its range, breeding occurs between March and October (1).
The cotton deermouse appears to prefer elevated nest sites (1), often in logs, stumps, moss, in old buildings or under loose bark (1) (5), where it builds a spherical nest of leaves and other plant material (5). The gestation period of the cotton deermouse is typically 23 days (1) (2) (3) (4) (5), but may last up to 30 days if the female is nursing a previous litter (1) (4). A female of this species can produce several litters per year (1) (3) (4) (7), usually four or five in total (5), with each containing an average of three or four young (3) (4). However, as few as one and as many as seven young can be born per litter (1) (3) (4) (7).
The young of the cotton deermouse are born pink, naked and blind (4) (5), but grow and mature rapidly (2) (5), reaching about 85 percent of the adult size by just four weeks of age (2). They are weaned at 20 to 25 days old (4) (5), and reach sexual maturity within 1 or 2 months (1) (4). The cotton deermouse has an average lifespan of about four or five months (2), but may live up to a year or more (1) (5).
An omnivorous species (2) (4) (5) (6), the cotton deermouse is opportunistic, eating almost anything that is available (1) (2) (3) including acorns, nuts, seeds, fungi, insects, spiders and snails (5). However, it is thought that this species tends to eat more animal than plant matter (1) (3) (6).