Animals orienting to air-borne odor plumes must do so in constantly changing meteorological conditions, with humidity and temperature shaping plume characteristics. Because most studies of olfactory orientation are conducted on small species (e.g., insects and laboratory rodents) in captivity, there is of a dearth of field studies. Thus, how animals adapt to the changing physical properties of the plume in the field is poorly understood (Vickers 2000; Baker et al. 2018). The olfactory landscapes faced by long-distance olfactory navigating vertebrates, such as homing and migrating birds or polar bears, have instead been estimated by proxy (e.g., pollutant particle movement, Wallraff 2013) or with models (Safi et al. 2016; Togunov et al. 2017).
How such conditions should affect air-borne odor characteristics is a complex question. Odors typically consist of multiple chemical constituents, most of which are low-molecular weight, volatile organic compounds (Auffarth 2013). Further, such complicated mixtures exist in multiple phases simultaneously: vapor, aerosol, and liquid, when deposited on a surface. Each potential reservoir may have a different chemical composition. Three important parameters determining this composition are air temperature, relative humidity, and wind speed. Thus, the odor stimuli available to a navigating animal is highly dynamic in space and time, due to both local atmospheric thermodynamic conditions (i.e., temperature and relative humidity) as well as local atmospheric flow conditions (i.e., velocity and variability). Finally, natural environments are best characterized as turbulent flow conditions; the chaotic velocity field is highly variable in time and space (Csanady 1973).
Search and hunting dogs are known to locate targets accurately over a range of meteorological conditions (reviewed in Rosell 2018). Yet it has been difficult to show exactly how weather influences a dog’s search, since dogs are equally successful in finding the target under different weather conditions (Greatbatch et al. 2015). The question of how dogs adapt their search strategy to compensate for weather changes has not yet been addressed, despite a number of studies on search strategies (Thesen et al. 1993; Gazit et al. 2005; Hepper and Wells 2005). Our goal therefore was to test the hypothesis that dogs change their search strategy to adapt to changing meteorological conditions, by simultaneously measuring meteorological variables and dog behavior in open rangeland. We predicted that with higher temperature, lower humidity, and higher wind speed search dogs would be less accurate in following the experimental trail and would shift their sampling from airborne to the more stable substrate odors.