How Ambient Environment Influences Olfactory Orientation in Search and Rescue Dogs

Abstract

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 hours) 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 original trail. Dogs also modified their speed and head position according to their search location distance from the original 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. To our knowledge, this is the first study of a mammalian species responding to localized shifts in ambient conditions and it lays the foundation for future studies of olfactory orientation, and the development of a highly tractable mammalian species for such research

Canine Olfaction: Physiology, Behavior, and Possibilities for Practical Applications

“…The second was air sniffing with the nose up, where the olfactory molecules move with the movement of the air, to detect airborne scents in large-area searches where there is no scent trail to follow [ 82 ]. Dogs can use either or both of these methods, depending on the weather conditions [ 83 ], the environment in which they are working [ 62 ], the scent they are looking for [ 82 ], and training [ 41 ].…”

“…Some of the main limiting factors of detection and tracking performance are weather conditions, such as temperature, wind, and humidity [ 83 , 89 ], and breed type, as breeds that had been originally selected for scent work demonstrate a higher olfactory acuity than those not selected for such work [ 41 ]. Although breeds with a high number of odor receptor cells and elongated noses with a large nasal cavity, for example Bloodhounds [ 90 ], might be expected to perform better than brachycephalic dogs, which have a smaller olfactory bulb [ 91 ] and disturbed nasal air passage [ 92 ] that lowers their ability to track a scent [ 41 ], Hall et al [ 93 ] suggest that differences connected with the breed specificity do not exist at all.…”

Spatial information from the odour environment in mammalian olfaction

“…Interestingly, a recent study in dogs has found that environmental changes such as humidity and air temperature influence the animal's sampling behaviour. The dogs moved more slowly and sampled odours closer to the ground under hot and dry conditions, while lower temperatures and higher humidity allowed for more rapid movement while sampling air-borne odours (Jinn et al 2020). While behaviour and psychophysics along trail tracking in mammals has thus seen encouraging advances over the last years, dissection of neural representation of odour trails and the neural mechanisms behind trail following are only just about to become the target of investigation.…”

“…Localising the source of an odour plume is thus a different and possibly more complex challenge for the olfactory system. Tracking such airborne plumes, however, is a frequently observed behaviour in many species, including mammals such as dogs (Jinn et al 2020;Hepper and Wells 2005;Jacobs 2012); it is less well studied in natural ethological behaviours for rodents (Howard et al 1968;Jacobs 2012).…”

“…Task design was one challenge behind studies of plume-tracking navigation, due to animals primarily choosing the fastest strategy to get the rewardwhich in laboratory environments with limited complexity is not necessarily following odour concentration gradients or plumes (Bhattacharyya and Singh Bhalla 2015;Gire et al 2016). Moreover, the type of strategy and sensory information used by the animal may depend on the type of environment it lives in and in which it performs such searches, as well as environmental conditions at the time of the search (Jinn et al 2020). With this in mind, one has to consider that experiments performed in a simplified laboratory arena are a great tool to study what an animal can do and chooses to do when faced with a particular task and environment, but also need to be interpreted as simplified versions of a natural environment (Fig.…”