Summary
Garbage dumps are at present unavoidable and have considerable impact on areas where they are located. Darlington (1969) reviewed some of the potential effects of dumps, including the inhibition of plant growth by altering soil composition and permeability, and by providing centres for destructive rodents. The California State Water Pollution Control Board (1961) and Anderson & Dornbush (1968) reported pollution of local ground water from refuse disposal while Hanks (1967) reviewed the diseases and their vectors associated with dumps. An important ecological effect of dumps is the local impact of introduced animals and plants brought in with garbage (Darlington 1969). There is a lack of data on the inhabitation of dumps by rodents and other small mammals. Darlington (1969) estimated that between 700 and 1000 Mus musculus (see Appendix for common names) as well as Rattus spp. occupied a dump site in Essex, England. Marsh & Howard (1969) found that dumps in California support principally R. norvegicus, occasionally R. rattus and, less frequently, ground squirrels (Citellus spp.) and Mus musculus. The purpose of this study was to investigate the effects of a small, rural dump on local populations of small mammals, principally rodents. The possible interactions between Peromyscus leucopus and Mus musculus in a dump situation were also recorded.
Methodology
Eighty-nine Sherman live-traps baited with peanut butter were deployed on each of two 0*23-ha grids which were 82 m apart. Each grid consisted of two parts: one 0*03-ha area with forty-nine traps set 4-6 m apart, and a surrounding 0-20-ha area with forty traps set at 13-8 m intervals. Peromyscus leucopus captured in traps were toe-clipped and eartagged for future recognition, and their sex, breeding condition, pelage colouration, and point of capture on the grid were recorded. P. leucopus were classed as juveniles if they had an all-grey pelage, as sub-adults if the pelage was both grey and brown, and as adults if the pelage was all brown. Trapping was carried out for three consecutive nights at the beginning of each week for the twelve-week study period.