Barrier Island Small Mammals 
133 
df, p<0.005). It feeds on grasses, sedges, insects, crabs, fish, and the eggs 
and young of birds (Golley 1966; Sharp 1967). Although bird eggs and 
nestlings are not available in winter, the probable abundance of other 
food items in the salt marsh could explain why Oryzomys is able to 
exploit this habitat so successfully. Oryzomys was also common in the 
salt marshes of Kiawah Island (Pelton 1975) and was the most widely 
distributed mammal in the Virginia barrier island complex (Dueser et al. 
1979). 
Sigmodon and Oryzomys are sympatric in the salt marsh and old-field 
habitats, indicating some similarity in habitat requirements, i.e. dense 
grass and weed cover. Oryzomys prefers stream edges, freshwater 
marshes, and salt marshes, while Sigmodon prefers drier grass fields and 
thickets (Golley 1966). Although Oryzomys was found in all habitats on 
Bulls Island it was most abundant in the salt marsh (9.4 RAV), salt spray 
forest (2.9 RAV), freshwater marsh (2.7 RAV), and sand dunes (1.6 
RAV), while Sigmodon was common only in the old-field habitat (2.5 
RAV). Significantly more Oryzomys were captured in the salt marsh than 
Sigmodon (p<0.005), while more Sigmodon were captured in the old- 
field habitat than Oryzomys (p<0.05), demonstrating that Sigmodon is 
found mostly in old-fields. 
Of the three species captured in the residential area, Peromyscus was 
most abundant (2.6 RAV), followed by the house mouse, Mus musculus 
(1.9 RAV), and Oryzomys (0.6 RAV). The difference was not significant 
(X^=1.8, 1 df, p>0.1) between Peromyscus and Oryzomys. Pelton (1975) 
found that Peromyscus invaded homes on Kiawah Island, as it has on 
Bulls Island, and also reported that it was the most abundant small 
mammal of Kiawah Island. On Bulls Island Peromyscus is less abundant 
than Oryzomys and Sigmodon. It is interesting to note that Mus (an 
exotic species) was captured only in the residential area of Bulls Island. 
Pelton (1975) found no Mus in or around the residential areas of Kiawah 
Island. He reported, however, capturing Mus in abundance in the sand 
dune habitat. Dueser et al. (1979) captured Mus on four Virginia barrier 
islands and found that its distribution was not limited to the vicinity of 
cabins on three of the islands. 
Representatives of the small mammal fauna of Bulls Island used all 
habitats sampled. Mus was found only in the residential area. Peromys- 
cus inhabited the maritime live oak forest and probably colonized the 
residential area with migrants from that habitat. Oryzomys captured in 
the residential area probably also represented migrants from surrounding 
habitats. In old-fields Sigmodon is numerically dominant to other spe- 
cies. Oryzomys is a habitat generalist on Bulls Island, but it is most 
abundant in the salt marsh. 
