## 3 Results and Discussion  
The dogs encountered many more tortoises than were tethered as part of the research trials because tortoises not involved in our study lived in the pens where our trials were conducted. While we quantified some of the variables that may influence target variants it is not necessary to capture all variants to assess detection distance. As a target, tortoises present greater variability in scent than single molecule target compounds such as cocaine, for example. For the detection distance calculation, whether or not a tortoise was in a trial was irrelevant so long as the find was verified. The total number of tortoises encountered by the dogs, both tethered and wild, was 184. The total number missed from the known placements was 8. Of these 184 encounters, we believe the dogs first detected 21 tortoises visually for a total data set of 163 most likely detected by olfaction. Visual detections were ascertained by the dog GPS track data showing direct movement to a tortoise while upwind. Of the 163 tortoise encounters, 99 were part of our study and were measured and sexed ('known'). The other 64 tortoises were 'wild' and we did not take measurements of these animals. Size of the known tortoises thus located (\(n=99\)) were between 89 mm and 300 mm midline carapace length (MCL; Table 1). Detection distances were evaluated for normality to determine whether parametric or nonparametric statistical tests were appropriate. The data were non-normally distributed and had positive and significant values of skewness (1.7552, p \(<\) 0.0001) and kurtosis (3.4910, p \(<\) 0.0001), respectively. For all tortoise encounters, detection distance ranged between 0.50 m and 62.82 m with a median of 11.13 m (mean of 13.91 m). We found no difference in detection distances between the dogs (Kruskall-Wallis 1-way ANOVA; n = 163, p = 0.7594) for either type of tortoise encounter, wild or \begin{table}
\begin{tabular}{|l|l|l|l|} \hline  & Known (m) & Wild (m) & All (m) \\ \hline _Minimum_ & 0.75 & 0.50 & 0.50 \\ \hline _Maximum_ & 56.01 & 62.82 & 62.82 \\ \hline _Mean_ & 13.31 & 14.84 & 13.91 \\ \hline _Median_ & 11.24 & 10.35 & 11.13 \\ \hline \end{tabular}
\end{table} 
Table 1: Summary statistics of detection distances for surface tortoises located using air scent during trials. ”Known” were tortoises tethered as part of the study (n = 99). ”Wild” tortoises were those that were located by the dogs but not placed as part of the study (n = 64). ”All” summarizes all tortoises located by the dogs during the study (n = 163). known. We found no difference in detection distances by sex of the tortoise (p = 0.2862), by size class (p = 0.5350) or by individual tortoise (p = 0.6859). Tortoise size and age are generally positively related. From a deployment and sampling perspective, it is important to note that there was no sex or size bias in detectability of the tortoises. There did not appear to be any single tortoise that the dogs learned to find or had a particular attraction to over others. There was no significant relationship between the time of day and detection distance (r = 0.03, p = 0.7199) and detection distances in each trial were not significantly different (n = 163, p = 0.0157), although environmental conditions between trials (relative humidity, temperature, wind speed means) were significantly different. Detection times ranged between 0745 and 1753. The dogs were able to detect tortoises from variable distances with a level of equal proficiency [20] despite variable environmental conditions that are thought to affect scent behavior and so affect vapor transport. Temperatures (T) recorded during the trials ranged from 12 C - 27 C. Relative humidity (RH) ranged between 16% and 85%. Wind speed ranged between 0 m/s and 9 m/s.