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.

Biosecurity screening in Australia includes detector dogs that search for potential biological hazards arriving in luggage and mail. To further improve biosecurity screening, we propose that these detector dogs could be used to screen for high-risk invasive insects; in particular, the brown marmorated stink bug Halyomorpha halys (BMSB) (Hemiptera: Pentatomidae). This research project investigated the feasibility of the use of training aids as odour proxies when conditioning dogs to detect live, exotic insects that are inaccessible for training purposes. Chemical odour comparisons using headspace gas chromatography-mass spectrometry (GC-MS) in combination with canine scent detection testing were used to assess two potential training aids – a novel scent extract and dead specimens - for their efficacy in training for live insect detection.

A locally abundant pentatomid species, the bronze orange bug Musgraveia sulciventris (BOB) (Hemiptera: Tessaratomidae), was used as an experimental model to test these training aids and provide a proof-of-concept for future application of these training aids in BMSB detection training. Headspace GC-MS analyses identified considerable similarities in volatile organic compounds (VOCs) between live BOB specimens and both BOB training aids. Following this, canine scent detection testing demonstrated that among biosecurity detector dogs (n = 4), most were able to generalize from scent extract (2/2) or dead specimens (1/2) to live specimens of that species (p = 0.008). A follow-up experiment further assessed the use of scent extract and investigated how dogs might generalize between different insect species for insect detection training. This experiment revealed that, after being trained with only BOB scent extract, all biosecurity detector dogs (n = 4) generalized to dead BOB specimens (p < 0.05), and only one dog generalized to dead BMSB specimens with sufficient accuracy (p < 0.05). However, contrary to expectations, the dogs also all falsely responded to several unrelated insect species in the following trials.

Subsequent experiments compared chemical odour profiles of BMSB training aids and live BMSB specimens using headspace GC-MS and revealed substantial VOC similarities, supporting their use for canine BMSB detection. In particular, BMSB scent extract appeared to have a very similar composition to live specimens.

Finally, using a novel method - a habituation-dishabituation paradigm – we tested dogs’ (n = 13) detection threshold of the BMSB scent extract, revealing dogs’ apparent ability to perceive the scent extract at very low concentrations - between the lowest concentration tested, a 1:1000 extract-pentane dilution, and 1:500 dilution. The novel application of this paradigm for determining canine odour thresholds had not been tested previously.

Overall, the findings of this research suggest that scent extract and dead specimens may be effective and practical training aids for training biosecurity detector dogs for live BMSB detection, and these training aids are now being used to train biosecurity detector dogs to screen for BMSB in Australia. Following future research, this method may also be applicable for other species of high-risk insect pests.

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.