. The Canadian field-naturalist. 1998 Perkins, Hodgman, Owen, and Dimond: DDT in Shrews 397 2 -. ^ 1 - YEAR Figure 3. Decline of mean total DDT levels among insecti- vores from Aroostook County, Maine. DDT in this area likely resulted from drift during aerial spraying or from movement of forest biota. Shrews forage by preying on various insects (including Spruce Budworm), worms, and slugs, as well as by scavenging (Whitaker and Mumford 1972; Jennings et al. 1991). Slugs and earthworms can accumulate high levels of DDT (Forsyth et al. 1982; Beyer and Krynitsky 1989), and DDT Residues have been
. The Canadian field-naturalist. 1998 Perkins, Hodgman, Owen, and Dimond: DDT in Shrews 397 2 -. ^ 1 - YEAR Figure 3. Decline of mean total DDT levels among insecti- vores from Aroostook County, Maine. DDT in this area likely resulted from drift during aerial spraying or from movement of forest biota. Shrews forage by preying on various insects (including Spruce Budworm), worms, and slugs, as well as by scavenging (Whitaker and Mumford 1972; Jennings et al. 1991). Slugs and earthworms can accumulate high levels of DDT (Forsyth et al. 1982; Beyer and Krynitsky 1989), and DDT Residues have been found in earthworms 20 years after treatment (Beyer and Krynitsky 1989). Further, bioaccumulation of DDT through shrews eating con- taminated earthworms has been demonstrated (Forsyth et al. 1982). Effects of bioaccumulation are clearly shown in the comparisons of insectivores and herbivores by Dimond and Sherburne (1969). Insectivores, including Masked Shrews, experi- enced a decline in DDT levels over time on both sprayed and control sites (Table 3). Levels from 1994 were approximately 20 X lower than levels in 1973 for insectivores and separately for Masked Shrews. Soil samples from northern Maine have shown an increase in DDE and DDD, with a decrease in DDT over time (Dimond and Owen 1996). When DDT decreases, while DDE and DDD increase, it indi- cates the weathering of DDT (Schmitt et al. 1990; Wade et al. 1994). The metabolism of DDT to DDE in animals is usually accomplished by dehy- drodechlorination (Schmitt et al. 1990). Further reductive dechlorination to DDD occurs in some species, but to a lesser extent (Edwards and Millbum 1985). In our study, DDE increased while DDT and DDD decreased over time (Figure 2); DDD was the least represented metabolite in our samples. Hebert et al. (1994) found that high DDE concen- trations indicated a historic source of DDT. Furthermore, the shrews in our study area are short- lived, nonmigratory, have dispersal distances of under 5 km
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