Characterization of the Ashepoo-Combahee-Edisto (ACE) Basin, South Carolina
Forty-seven species of mammals, in nine orders, are estimated to occur in the ACE Basin study, representing nine orders: bats, rabbits, rodents, marsupials, insectivores, carnivores, manatees, dolphins, and hooved mammals. A number of mammalian species (e.g., dolphins, whales, and manatees) have adapted to an exclusively aquatic life. Several species of dolphins and whales can be found in waters offshore of the ACE Basin study area. These include the saddleback, Risso, Atlantic spotted, and striped dolphins, as well as the short-finned pilot, killer, goose-beaked, sperm, dwarf sperm, and pygmy whales. These species are almost exclusively oceanic species and are encountered only very rarely in the nearshore coastal regions. Two species of marine mammals are residents in the coastal waters of the ACE Basin study area, the bottlenose dolphin and the West Indian manatee. Most of the species in the ACE Basin are widely distributed, and they utilize a variety of habitats.
The dune and maritime shrub thicket communities on the ACE Basin's barrier islands (e.g., Edisto Beach and Otter Island) are extremely harsh environments, and few mammalian species are adapted to subsist here (Sandifer et al. 1980). In general, only those species which can adapt to survive in any habitat are found in the dune communities. Several of these species, such as the house mouse and raccoon, are generalist feeders that consume a wide variety of plant and animal matter. White-tailed deer, opossums, and raccoons are probably the only large mammals found on sand dunes. These mammals come out onto the dunes to graze (deer) or to hunt (raccoons and opossums). The maritime forests that lie inland of the dune and maritime shrub thicket communities contain a more diverse mammalian assemblage. All five insectivore (insect eater) species such as the short-tailed shrew, least shrew, and eastern moles, of the ACE Basin study area probably occur in maritime forests. Bats are another group of insect eaters that feed in the maritime forest, and the dominant species include Seminole bats, red bats, big-brown bats, and evening bats. Of the larger omnivorous or carnivorous mammals, the raccoon, opossum, and bobcat are probably the most abundant in the maritime forests (Pelton 1975).
Like the dune community, the salt marsh habitats of the ACE Basin study area have a low diversity of mammals, and contain a similar assemblage of mammals (e.g., rats, mice, and shrews). The ubiquitous white-tailed deer and raccoon regularly forage in the salt marsh. River otters are a dominant carnivore in the salt marsh habitat where they feed on a variety of aquatic animals including fish, crustaceans, turtles, and waterfowl (Baker and Carmichael 1996); however, the species also frequents the deep freshwater habitat of the maritime and palustrine ecosystem. Several species of mammals are specifically adapted to estuarine habitat. For example, the marsh rabbit, which is often abundant in the brackish marshes of coastal zones, feeds upon a variety of brackish marsh plants including marsh pennywort and cattails. The marsh rice rat is also adapted to the salt marsh habitat (Webster et al. 1985).
The palustrine ecosystem is the most diverse habitat in the ACE Basin study area. The ecosystem contains freshwater rivers, marshes, meadows, swamps, hardwood forests, mixed forests, and pine forests. Because it is so diverse, the palustrine ecosystem is likely to provide suitable habitat for every mammal found in the ACE Basin study area. Some species, such as the opossum, eastern mole, golden mouse, house mouse, cottontail rabbit, raccoon, long-tailed weasel, and white-tailed deer are ubiquitous and are found in many different palustrine habitats. Other species exhibit specific habitat preferences.
The upland ecosystem in the ACE Basin study area contains fewer unique habitats than palustrine ecosystems and, therefore, a less diverse mammalian community. Upland habitat where cleared fields are interspersed with woodlands provides sites for foraging as well as sufficient cover for protection against predators for a number of small herbivorous mammals such as cottontail rabbits, rats, and mice (Webster et al. 1985). Coyotes and red foxes utilize the agricultural fields to hunt the small mammals which forage there. Both species feed on rabbits, mice, birds, insects, carrion, and even some fruits and berries. Pine forests, a common upland community in the ACE Basin, contain a mammalian community that is similar to that found in palustrine forests. A few species such as the fox squirrel and Seminole bats are probably more abundant in pine forest than in the palustrine forests because of their preference for feeding on or roosting in pine trees.
Similar to bird species, mammals typically utilize several habitat types during their lifetime. Thus, loss of habitat diversity is probably the most significant threat to mammals. For example, the conversion of forested lands to agricultural fields or pine plantations produces monoculture upland habitats that support substantially fewer species (Meffe and Carroll 1994). Consequently, to preserve the mammalian fauna in the ACE Basin study area, managers must continue to protect large tracts of undisturbed land that include an interspersion of many different habitat types such as wetlands, meadows, and forests.