Accuracy and Reliability of Dogs in Surveying for Desert Tortoise (Gopherus Agassizii)

Abstract

The desert tortoise (Gopherus agassizii) is federally listed as "threatened" and is afforded protection in several U.S. states including California, Nevada, Utah, and Arizona. Numerous factors ranging from habitat destruction to disease are thought to contribute to the species' decline throughout its range. Data collection on desert tortoises in the wild is challenging because tortoises are secretive, and many age and size classes are virtually undetectable in the wild. Detection dogs have been used for decades to assist humans, and the use of dogs for wildlife surveys is of increasing interest to scientists and wildlife managers. To address the basic question of whether dogs could be used to survey for the desert tortoise, we quantified the reliability and efficacy of dogs trained for this purpose. Efficacy is the number of tortoises that dogs find out of a known population. Reliability is a measure of how many times a dog performs its trained alert when it has found a tortoise. A series of experimental trials were designed to statistically quantify these metrics in the field setting where dogs trained to locate live desert tortoises were tested on their ability to find them on the surface, in burrows, and in mark-recapture surveys. Results indicated that dogs are effective at and can safely locate desert tortoises with reliability on the surface and are capable of detecting tortoises in burrows under a range of environmental conditions. Dogs found tortoises at the same statistical rate at temperatures between 12 degrees and 27 degrees C, relative humidity from 16% to 87%, and wind speeds up to 8 m/s. In both surface and burrow trials, dogs found >90% of the experimental animals. In comparative studies with humans, dogs found tortoises as small as 30 mm, whereas the smallest tortoise located by human survey teams was 110 mm. Although not all dogs or dog teams meet the requirements to conduct wildlife surveys, results from this study show the promise in using dogs to increase our knowledge of rare, threatened, and endangered species through improved data collection methods.

Identifying suitable detection dogs

“…Motivators which are important during detection dog selection are play-, prey-, and huntdrives (Maejima et al, 2007;Hurt and Smith, 2009;Reed et al, 2011;Beebe et al, 2016;Minhinnick et al, 2016). A dog's play-drive is the desire to be entertained, which ensures the dog values a toy or play reward in exchange for performing a particular behaviour (Cablk and Heaton, 2006;Hurt and Smith, 2009;Duggan et al, 2011). A detection dog will ideally be highly play motivated, to the point of obsession (Rebmann et al, 2000;Hurt and Smith, 2009;Beebe et al, 2016;Minhinnick et al, 2016).…”

“…This will ensure the dog is willing to perform hundreds of repetitions to receive their toy, which is crucial for training and work (Hurt and Smith, 2009). A dog's desire to search is referred to as their hunt-drive and is important for sustaining motivation (Cablk and Heaton, 2006;Hurt and Smith, 2009). This motivation to search is crucial for dogs during surveys where the work is fatiguing and target odours are minimal (Cablk and Heaton, 2006;Hurt and Smith, 2009;McGarrity et al, 2016).…”

“…A dog's desire to search is referred to as their hunt-drive and is important for sustaining motivation (Cablk and Heaton, 2006;Hurt and Smith, 2009). This motivation to search is crucial for dogs during surveys where the work is fatiguing and target odours are minimal (Cablk and Heaton, 2006;Hurt and Smith, 2009;McGarrity et al, 2016). A dog's prey-drive is their desire to chase and kill (Hurt and Smith, 2009;Minhinnick et al, 2016).…”

“…A dog's prey-drive is their desire to chase and kill (Hurt and Smith, 2009;Minhinnick et al, 2016). Whilst this may not be problematic for a drug detection dog which only works indoors, a wildlife detection dog with an uncontrolled high prey-drive can be catastrophic (Cablk and Heaton, 2006;Hurt and Smith, 2009;Beebe et al, 2016;Minhinnick et al, 2016). Ideally a detection dog would not be motivated to chase or kill another animal, which would minimise the risk to both wildlife and the dog (Cablk and Heaton, 2006;Hurt and Smith, 2009;Beebe et al, 2016;Minhinnick et al, 2016).…”

Rescue and relocation programme of turtles and tortoises and elongated tortoise monitoring programme in the Nam Theun 2 Reservoir (Laos)

“…Therefore, dogs were chosen for their ability to sniff out concealed turtles and tortoises. This method has been used worldwide by many researchers (Som et al, 2005;Cablk & Heaton, 2006). Surveys were conducted in the forest around each aquatic turtle trapping site.…”