HOW RODENTS SMELL BURIED SEEDS: A MODEL BASED ON THE BEHAVIOR OF PESTICIDES IN SOIL

Abstract

Olfaction is important in mammals and other animals for foraging, predator avoidance, and communication. However, very little is known about how the physical environment influences the activity of odorants. Many pesticides are organic molecules that appear to behave similarly to odorants of interest to rodent foragers. In this article, the literature on pesticide residues is used to construct a conceptual model of how odorants might behave under different environmental conditions. The primary focus of the model concerns how the environment might affect detection of buried seeds by rodents. The most important environmental variable influencing volatilizing of pesticides from soil is water content of soil. In dry soil, pesticides are adsorbed onto soil particles. However, when soil moisture increases above a monomolecular layer, pesticides desorb and vapor densities increase dramatically. These observations on changes in vapor density of pesticides as soil moisture changes are consistent with experimental data on olfaction in rodents. Other factors that influence pesticide volatilization include relative humidity, temperature, wind, soil characteristics (particle size, organic matter, and bulk density), and burial depth. Limited data suggest that these factors also influence the vapor density of odorants and, therefore, olfaction. The literature on pesticides allows us to make predictions about how animals detect odorants and then test those predictions experimentally.