The Trap Line as a Measure of Small Mammal Populations

Abstract

The value of a line of live traps as a measure of relative abundance was studied by field trials on Peromyscus leucopus at the Patuxent Research Refuge, Maryland. Lines tested were 600 ft. long and consisted of 40 traps. 8.4-acre plots enclosing these lines were censused by quadrat trapping. Plots were in upland and bottomland woods. There were nearly 8 times as many mice in the bottomlands as in the uplands, but the trap lines showed only 2.5 to 4 times as many in the bottomlands. The reason for the different results from the 2 methods was that mice had much larger ranges in the uplands. The trap lines in the uplands thus took mice from larger areas, giving deceptively high population estimates. Because of the distortion of results caused by variations in the range sizes of small mammals, it is believed that line trapping is not a fully satisfactory method of measuring relative abundance.