Evaluation of an odour-detection dog for non-invasive pregnancy diagnosis in polar bears ursus maritimus: considerations for training sniffer dogs for biomedical investigations in wildlife species

Odour-detection dogs are utilized by law enforcement to identify illegal substances, by conservation groups to locate scat from specific species, and more recently, in biomedical investigations such as cancer detection Because dogs can detect target odours in samples that can be collected non-invasively, such as faeces, they may be useful in diagnostic evaluations of zoo animals;however, reports are scarce describing the application of odour-detection dogs in medical diagnoses of wildlife species The objective of the current study was to investigate the reliability of a trained dog for pregnancy detection of polar bears Ursus maritimus, a species for which there is no means of non-invasive pregnancy diagnosis Using over 300 faecal samples collected from zoo-housed polar bears, a 2-year old beagle was trained to discriminate samples originating from pregnant bears from samples collected from non-pregnant individuals At training evaluation, the dog's sensitivity (true positive rate) and specificity (true negative rate) were 1 00 In two real-time tests performed during consecutive cubbing seasons, the dog evaluated samples collected from 16 female bears in the first year and 17 the subsequent year The dog's sensitivity was 0 00 both years and specificity was 0 97 and 1 00 during the first and second year, respectively The reduced sensitivity in testing versus training may be attributable to several causes, including failure to generalise the target odour to novel pregnancies It is likely that a large number of unique cases of condition are required to sufficiently train an odour-detection dog, which may be prohibitive in wildlife studies when sample sizes are liable to be limited Introduction The natural olfactory capabilities of domestic dogs Canis familiarize have been deployed by humans for diverse tasks, including detecting narcotics, explosives and accelerant, and for tracking human scent (Sommerville et al 1993;Settle et al 1994;Williams and Johnston 2002;Brown et al 2006) In conservation efforts, odour-detection dogs have been trained to locate scat from species of interest and to track individual animals (as reviewed by Beebe et al 2016) More recently, mounting evidence from biomedical research suggests that dogs can detect odours characteristic of various cancer types from numerous tissue sources (Pickel et al 2004;Willis et al 2004;McCulloch et al 2006;Horvath et al 2010;Cornu et al 2011;Sonada et al 2011) and even breath (Ehmann et al 2012) Although the majority of biomedical studies focus on cancer research, several describe the use of odour-detection dogs for other physiological investigations, such as clostridium diagnoses (Bomers et al 2014), hypoglycemia recognition in diabetic patients (Deblinger et al 2013), and even patterns of SARS-CoV-2 from respiratory secretion samples of infected patients (Jendrny et al 2020) Some veterinary studies evaluated giant African pouched rats Cricetomys gambianus in their ability to detect horse faces inoculated with Salmonella spp (Mahoney et al 2014) and dogs trained for estrous detection in dairy cows (Fischer-Tenhagen et al 2011);however, publications describing the application of sniff dogs in veterinary investigations of wildlife species are non-existent