DOI: 10.5061/dryad.sf7m0cg9t
title: Data for: An experimental assessment of detection dog ability to locate great crested newts (Triturus cristatus) at a channeled distance and through soil

description: Detection dogs are increasingly used to locate cryptic wildlife species,
 but their use for amphibians is still rather underexplored. In the present
 paper we focus on the great crested newts (Triturus cristatus), a European
 species which is experiencing high conservation concerns across its range,
 and assess the ability of a trained detection dog to locate individuals
 during their terrestrial phase. More specifically, we used a series of
 randomised, double-blinded experiments to document whether a range of
 distances between target newts and the detection dog affects the ability
 of localisation, and to assess the ability and efficiency of target newt
 detection in simulated subterranean refugia through 20 cm of two common
 soil types (clay and sandy soil, both with and without air vents to mimic
 mammal burrows, a common refuge used by T. cristatus). The detection dog
 accurately located all individual T. cristatus across the entire range of
 tested distances (25 cm - 2 m). The substrate trials revealed that the
 detection dog could locate individuals also through soil. As expected, the
 detection time during the soil discrimination trials was significantly
 reduced for treatments with vents. Contrary to existing studies with
 detection dogs in human forensic contexts, however, detection was
 generally faster for T. cristatus under clay soil compared to sandy soil.
 Our study provides a general baseline for the use of detection dogs in
 locating T. cristatus and similar amphibian species during their
 terrestrial phase.   
description: <strong>Soil interference trials</strong>
 Thirty <em>T. cristatus</em> (16 males and 14
 females) were retrieved from a quarry in south Gloucestershire between
 July and September 2021.  All <em>T. cristatus</em> used for
 the experiments were individually weighed to the nearest 0.1 g and
 measured from the tip of the snout to the end of the cloaca to the nearest
 mm. Two soil types were used: sandy soil collected from Calne Without,
 Bowden Hill, Wiltshire, Southwest England (OS grid reference ST954684),
 and clay soil collected from Broad Lane, Westerleigh Road, Westerleigh,
 South Gloucestershire, Southwest England (OS grid reference: ST695795).
 For soil characterisation, three reference samples were obtained from each
 site using a 20 cm long core, and merged into one sealed plastic bag for
 analysis at the University of Salford. In order to measure the pH, 20 ml
 of fresh soil was placed into a clean 50ml beaker. Distilled water was
 added to the 40 ml mark, and the mixture was left on an automatic stirrer
 for 15 minutes. The probe of a calibrated pH meter was then placed into
 the sample and left for 30 seconds for the reading to settle. This was
 repeated three times for each soil type with the probe cleaned with
 distilled water between each reading.  To gauge moisture content for each
 soil type, the soil was weighed, oven dried overnight at 105°C and
 re-weighed. The moisture content was obtained by subtracting the dry
 weight from the wet weight, divided by the dry weight and multiplied by
 100. Soil texture was analysed using an LA-960 Slurry Sampler, which uses
 laser diffraction to measure light scattered from the soil particles as it
 passes through the measurement cell. The percentage of silt, clay and sand
 was determined using a soil texture chart. The soil
 interference trials were carried out in the same field as the channelled
 distance perception trials. Four plots measuring 10 m x 4 m were erected 2
 m apart and demarcated using barrier tape. Each plot had eight holes dug
 to 250 mm depth and spaced evenly 2 m apart in a 2 x 4 setup (Figure 2a).
 Compartments to house individual <em>T. cristatus</em> were
 made from a guttering pipe socket (50 mm high, 61 mm in diameter), which
 was considered to supply enough air to the target newts during the trial.
 A plastic bung was placed at the base of the compartment to keep the newt
 in place and to reduce the chance of residual scent being left in the hole
 following the trial. A fibreglass 2 mm mesh was placed at the top of the
 compartment, a 200 mm plastic guttering pipe with 68 mm diameter (Figure
 2b) was then slotted over the top of the pipe socket, holding the netting
 in place. The pipe was weighed prior to the newt entering the compartment,
 and assigned to one of four treatments: Sandy Soil Full, Sandy Soil
 Vented, Clay Soil Full and Clay Soil Vented. The vented treatments
 comprised a plastic-coated wire mesh with 4 x 4 mm gaps. The mesh was cut
 to 200 mm length to sit within the 200 mm long pipe. The mesh was rolled
 up and secured with cable ties with diameter of approximately 25 mm to
 represent small mammal burrows (a common subterraneous refuge of
 <em>T. cristatus</em> ([11], see also [39] for the closely
 related <em>Triturus carnifex</em>). The soil was placed into
 the pipes using a trowel with soil placed around the wire mesh vents to
 ensure they stayed open. The pipes containing soil and newts were weighed
 to provide the weight of the soil by subtracting the pipe weight and the
 individual weight of the T. cristatus. Locations of each pipe within the
 plots was allocated using a random number generated in Microsoft Excel.
 Pipes with all treatment types and blank compartments served as controls.
 Two pipes of every treatment type was present in each plot with one soil
 type (e.g clay) located to the left of the plot and the other soil type
 (e.g. sandy) was positioned to the right. The location of each soil type
 changed between each run. Vented and full treatments were positioned
 alternatively within each plot.  Three out of the four plots contained a
 single T. cristatus with one plot serving as a control (Figure 2c). All
 pipes were placed out 30 minutes prior to the start of the trial to allow
 the scent to penetrate through the tubes. This was considered enough time
 to allow the scent to flow through 20cm of soil whilst also maintaining
 the welfare of the target newts. The experiments
 involved one or two assessors and the dog/handler team. Unlike the
 channelled distance perception trials, the experiments were undertaken
 blind as opposed to double blind due to limited numbers of assessors
 available. The assessor therefore performed the role of the observer and
 the tester and was present during the test runs. The dog/handler team was
 not aware of the location of the <em>T. cristatus</em> in each
 plot. During each trial, the assessor measured weather conditions (using
 same apparatus and methodology as described for the channelled distance
 perception trials), air temperature, air humidity, wind speed, wind
 direction and cloud coverage. Soil temperature and moisture content was
 measured by placing the probe 5 cm into the soil before trial runs took
 place using a Soil Condition Meter DSMM600, with moisture levels displayed
 as &lt;5% (Dry+), 5 to 10% (Dry), 10 to 20% (Normal), 20 to 30% (Wet)
 and &gt;30% (Wet+). Soil condition measurements were taken immediately
 before each 4-plot trial but not for single plot trial runs as a 4-plot
 trial would only take a maximum of 10 minutes, therefore conditions were
 unlikely to change within this timeframe. As measures of performance by
 the dog/handler team, numbers and locations of false negative, false
 positive, true negative and true positive indications were
 noted. The handler positioned the dog at the entrance
 of the plot. The assistant held the detection dog in place as the handler
 performed a ‘dummy drop’, where the handler moves between the tube
 locations and pretends to drop the odour, moving in numerical order to
 focus the dog.  The handler then returned to the dog, unclipped the lead
 and ask them to search. The handler  monitored the detection dog’s
 behaviour during the search, and when the dog indicated, the handler
 confirmed the location with the assessor and if correct the dog was
 rewarded, followed by a two-minute play session. If the dog/handler team
 was incorrect, then the search in each plot continued, noting down the
 number and locations of false indications until the correct indication was
 given. The trial was terminated if the dog/handler team could not locate
 the correct pipe within 180 seconds and the handler could not determine if
 the plot was blank. This length of time was considered sufficient given
 the size of the plot and the time taken to locate correct pipes during the
 practice sessions. The handler would call blank before the 180 seconds if
 she believed the plot did not have a <em>T. cristatus</em>
 individual present due to lack of interest by the detection dog.  A
 45-minute break was given between each 4-plot trial. New pipes were used
 during each trial. Fresh gloves were worn by the assessor when placing
 newts into the compartments to avoid transferring newt scent onto the
 outside of pipes. All pipes were moved to new positions between each
 trial. Each 4-plot trial was repeated four times within one day, and
 trials were carried out over two consecutive days in four successive weeks
 (19<sup>th</sup> August 2021 and 17<sup>th</sup>
 September 2021), resulting in a total of 128 single-plot trial runs. To
 minimise stress, twelve individual <em>T. cristatus</em> were
 selected at random to be used for the trial day, placed in a labelled
 container to prevent re-use. Twelve additional individuals were used for
 the consecutive day, taken from the tanks at random. The dog/handler team
 trained for three weeks in advance of the soil trial assessment, receiving
 consultation from Conservation K9 Consultancy.
description: Data can be accessed using Microsoft Excel.