Radio telemetry was selected as a tool to implement a two-year study (1964-66) of porcupine (Erethizon dorsatum) on a 4-square mile area in northeastern California. During the period of September 1964 through September 1966, 58 porcupine were ear-tagged, of which 12 males and 8 females were transmitter-tagged. One to seven porcupine with transmitters were afield at once, and were usually monitored 1-4 times per week for a total of 958 animal-days. Twenty-five to 30 percent of the population was immature, about 60 percent was adult, and the balance subadult. No drastic alteration in age class was observed during the 2-year period (Table I). A definite use pattern of habitat-types was displayed from May to December each year. Alfalfa was the primary food from June to September, and some pine trees near the fields also girdled. The maximum known distance traveled from a timber day-roost to alfalfa during one night was less than one mile. Quills and normal body buoyancy permit a porcupine to swim easily, and tagged animals frequently swam the creek on the area. After the first alfalfa freeze in September, the diet altered to inner bark and needles of pine. A gregariousness was first observed in October, and 2-3 were observed in a single tree through December. Single porcupine were observed during the balance of the year. The scrotal testes position was first observed during August 2-10, 1966, and as late as mid-December on four transmitter-tagged adult males. It appeared that lactation occurred in this population from May through August. Juniper "wolf" trees and much-girdled pine were frequented most during colder, stormy periods. The definition of home range, as commonly used, cannot be applied to the porcupine movement patterns observed on the research area, because no den or focal point activity was identified. High porcupine-use trees near springs, reservoirs, creeks and areas of succulent ground greenery (wet weather drainages) are choice sites for toxicant placement.
|
