Attributes of Rock Crevices Selected by Allegheny and Eastern Woodrats in the Zone of Contact in the Appalachian Mountains of North Carolina
Rossell, C. Reed, Roach, Stacey H., Rossell, Irene M., The American Midland Naturalist
We investigated the attributes of rock crevices selected by Allegheny (Neotoma magister) and eastern woodrats (N. floridana haematoreia) in their zone of contact in the Appalachian Mountains of North Carolina. In North Carolina, N. magister and N. f. haematoreia both occur in rocky habitats above 300 m, and are listed as species of special concern. We studied 14 active sites (N. magister. n = 9; N. f. haematoreia: n = 5) where woodrats had been captured 1 y prior to our study and identified to species using the mitochondrial DNA D-loop analysis. At each site, we measured the attributes of 10 crevices used by woodrats and 10 corresponding random crevices located < 15 m from each used crevice. Neotoma magister and N. f. haematoreia selected crevices with larger dimensions (height, width and depth) and more internal fissures (openings >5 cm in diameter) than those available in the surrounding environments. All crevices used by N. magister (n = 90) and N. f. haematoreia (n = 50) were dry. Neotoma magister were more specialized than N. f. haematoreia, as they selected crevices that were south-facing. These results suggest that both N. magister and N. f. haematoreia are habitat specialists in the southern Appalachians, preferring crevices with larger dimensions and more internal fissures to enhance their protection against severe weather and predators. The preference for south-facing crevices by N. magister suggests that they may be better adapted at surviving colder climatic conditions, thus enabling them to inhabit higher elevations in the mountains. Based on these specialized habitat preferences, we suggest that suitable rock crevices may be a limiting factor to both species in the southern Appalachians. In addition, the similarity in attributes of rock crevices selected by these species suggests that habitat is not a factor that will prevent hybridization between these species where they co-occur in the mountains of North Carolina.
Two species of woodrats inhabit die eastern United States. The Allegheny woodrat (Neotoma magister) is generally associated with rocky habitats and ranges throughout the Appalachian Mountains to Pennsylvania, the Cumberland Plateau and the Ohio River Valley (Castleberry et al, 2006). The eastern woodrat (N. floridana), which is comprised of eight subspecies, occupies a variety of habitats and occurs throughout much of the south-central and southeastern United States (Monty and Emerson, 2003). Neotoma magister share distributional boundaries with two subspecies of N. floridana: N. f. haematoreia in North Carolina and Tennessee, and N. f illinoensis in Alabama, Tennessee, Kentucky and Illinois (Ray et al, 2002). Both N. magister and N. f haematoreia are listed as federal species of concern (LeGrand et al, 2006), because of declining populations throughout their ranges (Monty et al., 2003; Monty and Emerson, 2003; LoGiudice, 2006). Although reasons for their decline are unknown, LoGiudice (2006) suggests a suite of factors including habitat fragmentation, changes in forest composition, fatal exposure as a secondary host to a parasite and proliferation of human-adapted predators.
In the Appalachian Mountains of western North Carolina and eastern Tennessee, where both Neotoma magister and M floridana haematoreia are found (Ray et al, 2002) , there is a lack of information on the habitats diese species use. Recent surveys in North Carolina indicate diat both N. magister and N. f. haematoreia are sporadically distributed and found in rocky habitats above 300 m, although N. f. haematoreia occasionally occur in old barns and abandoned buildings (Ray, 2000).
All members of die genus Neotoma use dens for protection from predators and adverse weather conditions, and as places to rest, store food, nest and rear young (Cameron and Rainey, 1972; Nowak and Paradiso, 1983). Neotoma dens are elaborate (Nowak and Paradiso, 1983), contain multiple entrances and exits, are large enough to accommodate nests and food cache sites and have peripheral areas for latrine sites (Rainey, 1956; Cameron and Rainey, 1972; Monty and Emerson, 2003). …