Hispid Cotton Rat - Habitat

Habitat

Hispid cotton rats occupy a wide variety of habitats within their range but are not randomly distributed among microhabitats. They are strongly associated with grassy patches that have some shrub overstory and they have little or no affinity for dicot-dominated patches. Habitat use and preference by hispid cotton rats usually appears to depend on the density of monocots. However, some studies are equivocal on the importance of other vegetation. For example, hispid cotton rats may respond favorably to a high percentage of dicots in a stand if cover remains optimal. In Kansas, hispid cotton rats increased on root-plowed prairie that experienced an increase in the diversity and biomass of early-successional forbs.

Male hispid cotton rats exhibit a lower degree of habitat selectivity than females. In Texas males were found on different habitat types (grassy, shrubby, and mixed) approximately in proportion to availability; female hispid cotton rats tended to choose mixed habitats more often than expected based on availability.

Habitat use varies with season and breeding status. In Texas grassy areas with some shrubs were preferred in spring and areas with more shrubby cover were preferred in fall.

In Kansas remnant prairie the preferred habitat of hispid cotton rats has dense undergrowth and an upper layer of protective vegetation such as big bluestem (Andropogon gerardii)/kochia (Kochia scoparia)/annual sunflower (Helianthus annuus). Hispid cotton rats prefer grassy clearings, croplands, overgrown fields, and overgrown roadsides and right-of-ways. In Kansas prairies hispid cotton rats occur at relatively high abundance in ungrazed uplands and sandy mixed-grass native prairie, but also prefer disturbed areas. Kaufman and others suggested that the use of disturbed areas was probably important in the recent invasion of hispid cotton rats into north-central Kansas from the northern presettlement limit of their range in Oklahoma. On Texas rangelands, hispid cotton rats appeared to respond to increased biomass of standing crop and increases in the proportion of the standing crop in potential food plants such as bristlegrasses (Setaria spp.). Hispid cotton rat density was four times greater on areas planted to exotic grasses including King Range bluestem (Bothriochloa ischaemum) and buffel grass (Enchrus ciliaris) than on native range dominated by windmill grass (Chloris spp.) and Texas wintergrass (Stipa leucotricha).

In northeastern Kansas, hispid cotton rats occurred at high population densities in tallgrass prairie (dominated by perennial grasses); population density declined to levels too low to accurately estimate over 28 years of succession to brush and trees. They are occasionally found in habitats dominated by early successional grassland species (i.e., annual grasses and forbs).

Hispid cotton rats occur in grassy areas or early-successional habitats within open woods. In the Southeast hispid cotton rat population density increases with the density of broomsedge (Andropogon virginicus) and other low growing plants, but declines with succession to brush and trees. In Texas pine-hardwood forests, hispid cotton rats were captured most often in narrow streamside management zones which have more light and thus more ground cover, and slightly less often in wider zones. In longleaf pine-slash pine stands of central Louisiana hispid cotton rats were captured in sawtimber, sapling, and regeneration stands but not in pole-sized timber; stands with surface cover were more likely to support hispid cotton rats. Pole-sized timber is dense, little light reaches the ground, and surface cover is minimal. In Louisiana and Mississippi, hispid cotton rats were more numerous in cut than in uncut bottomland hardwoods. They were also more numerous in cottonwood (Populus spp.) plantations than in uncut cottonwood stands. In northern Georgia intensive site preparation following clearcutting of pine-hardwood mixtures increases forage production and increased numbers of small mammals (presumably including hispid cotton rats).

In Colorado, hispid cotton rats occupy semimoist areas with abundant grasses and weeds and appear to be restricted to relatively warm areas. In New Mexico, hispid cotton rats do not occur regularly in areas with a mean annual temperature lower than 55 degrees Fahrenheit (13 °C) and a growing season shorter than 180 days. In Trans-Pecos, Texas, hispid cotton rats occur at the warmer, low elevations in areas of moderate to dense grassy cover.

When water and wastewater are added to baldcypress (Taxodium distichum var. distichum) domes, small mammals including hispid cotton rat move to peripheral areas that are drier. The rising water tables favor marsh rice rats (Oryzomys palustris) over hispid cotton rats.

Cameron and McClure compiled reports of hispid cotton rat population densities. The mean hispid cotton rat population density range for all studies was 5.3 to 31.1 rats per hectare. Population density ranges in Texas include 1 to 14 rats per hectare in coastal prairie, 17 to 84 rats per hectare in unmowed right-of-ways, 9 to 29 rats per hectare in old fields, 6 to 54 rats per hectare in abandoned fields, and 0.7 to 5 rats per hectare in grass-prickly-pear (Opuntia spp.). In Florida population density ranges include 0 to 24 rats per hectare in sand pine scrub, 2 to 47 rats per hectare in pine flatwoods, and 27 to 94 rats per hectare in tropical hammock. In Kansas hispid cotton rat density ranges were 0.2 to 21 rats per hectare in grassland; the highest estimated density was 65.4 hispid cotton rats per hectare in favored habitat.

In a study of the effects of habitat patchiness on movement, hispid cotton rats preferred only the largest patches which were 165 feet (50 m) by 330 feet (50×100 m). Patches were established by mowing strips between blocks of grasses. Hispid cotton rats were present in intermediate numbers on medium sized patches which were 39.6 feet by 79.2 feet (12×24 m), but were so scarce on the smallest patches that their movement pattern could not be analyzed.

In Kansas remnant prairie, the average annual home range of adult male hispid cotton rat was estimated as 0.969 acre (0.39 ha) and that of adult females as 0.543 acre (0.21 ha). The greatest distance traveled by an adult male was 330 feet (100 m) and by an adult female was 250.9 feet (76.4 m). In Texas male hispid cotton rats also had larger home ranges than females. Home ranges were larger in summer and winter than in spring and fall. Home range size was positively correlated with body mass and negatively correlated with population density. There was a relatively high degree of exclusivity (41%), indicating intolerance of conspecifics, particularly of the same sex . In Texas hispid cotton rats found their original home ranges (homed) from displacements of up to 5,000 feet (1,500 m). Returns were relatively high from displacements of up to 990 feet (300 m), suggesting that hispid cotton rats are familiar with the area within that distance. Hispid cotton rats released in areas with no cover homed better than hispid cotton rats released in typical hispid cotton rat habitat. Spencer and others used site fidelity as a measure of an individual's actual home range and concluded that hispid cotton rats have both single-day and multiday site fidelity and therefore establish true home ranges.