Physiological and behavioral effects of guthion on pine voles, Microtus pinetorum.

Abstract

0 0-dimethyl S-[(4-oxo-l,2,3benzotriazin -3(4H)-yl) methyl] phosphordithioate) is an organophosphate (OP) insecticide used extensively on apple trees in North Carolina and on numerous crops nationwide. Goodman et.al. (1983) estimated that 25~ or more of Guthion loss from tree leaves occurs as movement to the soil and ground vegetation causing Guthion exposure to grounddwelling mammals. Guthion inhibits brain acetylcholinesterase (AChE) in rodents (Short et.al. 1980) and affects locomotion, reproductive physiology and learning, yet little is known of the effects intermittent and acute exposures have on the physiological and behavioral ecology of wild small mammals. Pine voles (Hicrotus pJnetor~m), semifossorial residents of orchards throughout eastern United States, present a conflict for growers and conservationists because their semifossorial habits often result in root damage and girdling of trees. Because of this, toxic effects in pine voles following Guthion spraying might be welcomed by growers, yet these effects may suggest toxicity to mammals and birds that interact in complex, ecologically beneficial ways. Further, survivors of Guthion exposure often exhibit abnormal behaviors that could increase rather than decrease pine vole population growth. We conducted 3 experiments on pine voles: (I) to measure Guthion's inhibition of brain AChE activity in field-exposed voles; (2) to evaluate dose-related reductions of AChE in the laboratory; and (3) to measure Guthion-induced behavioral changes.