How Ambient Environment Influences Olfactory Orientation in Search and Rescue Dogs

Under natural conditions, an animal orienting to an air-borne odor plume must contend with the shifting influence of meteorological variables, such as air temperature, humidity, and wind speed, on the location and the detectability of the plume. Despite their importance, the natural statistics of such variables are difficult to reproduce in the laboratory and hence few studies have investigated strategies of olfactory orientation by mobile animals under different meteorological conditions. Using trained search and rescue dogs, we quantified the olfactory orientation behaviors of dogs searching for a trail (aged 1-3 h) of a hidden human subject in a natural landscape, under a range of meteorological conditions. Dogs were highly successful in locating the human target hidden 800 m from the start location (93% success). Humidity and air temperature had a significant effect on search strategy: as air conditions became cooler and more humid, dogs searched significantly closer to the experimental trail. Dogs also modified their speed and head position according to their search location distance from the experimental trail. When close to the trail, dogs searched with their head up and ran quickly but when their search took them farther from the trail, they were more likely to search with their nose to the ground, moving more slowly. This study of a mammalian species responding to localized shifts in ambient conditions lays the foundation for future studies of olfactory orientation, and the development of a highly tractable mammalian species for such research.