Simple SummaryDogs are valued for their odor detection capabilities in a vast range of fields. They help to find hidden and elusive targets, such as explosives, narcotics, missing persons, and invasive or endangered species, amongst an extensive list. In all these roles, dogs are required to find real target odors that vary somewhat from those with which they were trained. For example, dogs might be trained with an explosive mixture or certain explosive compounds, and then must be able to find homemade explosives of differing compositions or manufacturing processes. This ability, to respond to similar odors in the same way as they would respond to the originally trained odor, is known as generalization. A failure to generalize can result in dogs missing targets in working scenarios. Although generalization is usually desired to some extent, dogs must also discriminate against related odors that are not targets. Therefore, research that investigates factors that can influence dogs’ tendency to generalize, and conversely to discriminate, can inform training strategies to improve detection outcomes. However, this field requires further research with greater application to practical training.AbstractGeneralizing to target odor variations while retaining specificity against non-targets is crucial to the success of detector dogs under working conditions. As such, the importance of generalization should be considered in the formulation of effective training strategies. Research investigating olfactory generalization from pure singular compounds to more complex odor mixtures helps to elucidate animals’ olfactory generalization tendencies and inform ways to alter the generalization gradient by broadening or narrowing the range of stimuli to which dogs will respond. Olfactory generalization depends upon both intrinsic factors of the odors, such as concentration, as well as behavioral and cognitive factors related to training and previous experience. Based on the current research, some training factors may influence generalization. For example, using multiple target exemplars appears to be the most effective way to promote elemental processing and broaden the generalization gradient, whereas increasing the number of training instances with fewer exemplars can narrow the gradient, thereby increasing discrimination. Overall, this research area requires further attention and study to increase our understanding of olfactory generalization in dogs, particularly detector dogs, to improve training and detection outcomes.

Detector dogs could be trained to find invasive insect pests at borders before they establish in new areas. However, without access to the live insects themselves, odor training aids are needed to condition dogs to their scent. This proof-of-concept study assessed 2 potential training aids for insect detection: a scent extract and dead specimens of the target species. Using Musgraveia sulciventris (Hemiptera: Tessaratomidae) as an experimental model, gas chromatography–mass spectrometry (GC-MS) analyses were carried out to compare the chemical headspaces that make up the odors of live specimens and these 2 training aids. This was then followed by canine scent-detection testing to investigate biosecurity detector dogs’ (n = 4) responses to training in an ecologically valid context. Both the scent extract and the dead specimens shared the majority of their volatile organic compounds (VOCs) with live insects. Of the dogs trained with scent extract (n = 2), both were able to detect the live insects accurately, and of those trained with dead specimens (n = 2), one detected the live insects accurately. These findings lend support for these training aids as odor-proxies for live insects—particularly scent extract, which is a relatively novel product with the potential for broad application to facilitate and improve insect-detection training.

The habituation–dishabituation (H–D) paradigm is an established measure of sensory perception in animals. However, it has rarely been applied to canine olfaction. It proposes that animals will lose interest in, or habituate to, a stimulus after successive exposures but will regain interest in, or dishabituate to, a novel stimulus if they can perceive it. This study assessed an H–D test's practicability to determine dogs' olfactory detection thresholds (ODTs) for a neutral odorant. A random selection of mixed‐breed pet dogs (n = 26) participated in two H–D tests in a repeated‐measures crossover design. They were first habituated to a carrier odor and then presented with either ascending concentrations of n‐amyl acetate in the known ODT range (experimental condition) or repeated carrier odor presentations (control condition). No single odor concentration elicited dishabituation in the majority of the dogs. However, individual dogs dishabituated at differing experimental concentrations significantly more often than in the control condition (p = .012). These findings provide some tentative support for using this method in studying canine olfaction. However, further assessment and refinement are needed before it can be a viable alternative to traditional ODT measurement.

To perform their role effectively, scent detection dogs require certain characteristics. Identifying these characteristics will inform the selection of prospective dogs and preferred approaches to their training. The current study drew upon the perspectives of industry stakeholders to identify the behavioural traits considered relevant for detection dogs in biosecurity screening roles. Dog handlers, trainers, and supervisors (n = 25) in Australian biosecurity operations participated in focus group interviews to determine the perceived characteristics that, in their experience, influence detection performance. Their descriptions were used to create a questionnaire which was then administered to handlers to assess the working behaviours of current biosecurity dogs. Responses were collected for 88% of the operational dogs (n = 36). An exploratory factor analysis revealed seven tentative dimensions: search motivation, emotional stability, search arousal, food motivation, play motivation, search independence, and search focus. Search motivation and search arousal were both positively associated with handler ratings of detection performance (p ≤ 0.006). In general, biosecurity dogs were scored consistently high in ratings of search motivation, emotional stability, and food motivation. Our approach has advanced our understanding of the working behaviours and characteristic profile of biosecurity detector dogs and will be used to inform candidate selection processes.