Fig 1.
A. A costum-made metal cone with a wide opening and space for a wide-mouth vial containing the sample. B. Example of the experimental setup for training and testing environment, with the positive sample positioned on the 4th cone.
Fig 2.
Experimental design of training and testing sessions.
A. Training session: Dogs were trained during 1–4 days with three lines of motivation of followed by a simple blinded lines with the tested concentration. When the dog successfully passes the level of concentration during testing (success in more than 75% of the lines), he was tested in a double-blind situation (B). B. Testing session: The testing session consists of three lines of motivation, two or three lines of simple blind tests, then four lines of double-blind tests. In the preliminary single-blinded phase, we required dogs to correctly complete two trials before advancing to the double-blinded phase. If a dog succeeded in only one out of the first two trials, a third trial was conducted to provide an additional opportunity for qualification.
Fig 3.
Performance of two dogs relative to concentration levels.
On the y-axis are the performances of the dogs in %, by concentration. The concentrations are indicated on the x-axis The success threshold is set at 75%.
Table 1.
Coding scheme for behaviours associated with marking.
Table 2.
General overview of the results, including the total number of trials and double-blinded conditions. Results are presented as absolute values, with square brackets indicating the range (minimum to maximum) and percentages shown in parentheses.
Table 3.
Dogs’ behaviour and performance linked to sample age during double-blinded tests. Percentages are shown in parenthesis.
Table 4.
Description of position of negative marked samples in urine, in double-blinded settings. Percentages are shown in parenthesis.