Is bedding material a more effective thermal insulator than trap cover for small mammal trapping? A field experiment

This dataset is currently part of a manuscript undergoing a review process in the Journal of Thermal Biology. The manuscript compares the thermal insulation provided by a cover, bedding, and a combination of both when applied to small mammal traps. Treatments were tested in two different environmental conditions, one where temperature is more stable (near the sea coast), and another where temperature fluctuations are more severe (in the Pyrenees).

The first sheet contains the data collected from four Sherman traps placed in an outside terrace. One trial lasted four days, and a second trial lasted two days. Temperature (ºC) and relative humidity (%) were recorded every 10 minutes with data loggers (Elitech RC-51) situated inside each trap. Traps were assigned to a treatment as follows: Cover (CV), trap with only the PVC cover; Bedding (BD): Trap with water-proof cotton wool inside; Cover+Bedding (CV+BD): trap with the cover and with water-proof cotton wool inside; Control (CN), a conventional trap; Another logger was placed outside to have measures of air temperature (Air). In the case of BD treatment, data-loggers were placed inside the cotton.

The second sheet contains the data collected from three traps of three different models: Sherman, Longworth, and Heslinga. To avoid ethical concerns related with keeping wild animals trapped for long periods of time, we placed hand-warmer heat pads (Terratherm) – with up to 12 hours of warmth – within traps to simulate endothermic metabolism generated by a trapped small mammal (Kearney et al., 2011; Griffiths et al., 2017). Despite the covers being designed for Sherman traps, in the trials we also included two other commercial traps used in the SEMICE monitoring programme (Torre et al., 2018), Longworth (Longworth Scientific Instrument Co., Oxford, UK), and Heslinga (www.heslingatraps.eu) for thermal insulation capacity comparisons. The experiments were conducted in two contrasting climatic areas in Barcelona province (coastal, 22 m.a.s.l, and Pyrenees, 650 m.a.s.l), to expand the range of temporal and spatial variation in winter temperatures. We performed 63 trials combining three trap models and three treatments. Traps were placed in similar conditions and submitted to the same CN, BD and CV+BD treatments cited above. The CV treatment (trap with only the PVC cover) was excluded from the second experiment due to its poor performance in retaining temperature and humidity, as demonstrated in the first experimental session (see ‘Results’ section). Furthermore, the CV treatment does not represent a common treatment in small mammal trapping studies. Inside each trap we placed a temperature data logger (iButton, Thermochron) protected within an aluminium mesh, an ideal material to house the small temperature loggers (Orrock and Connolly, 2016). In the Bedding treatments, the mesh was placed inside the cotton. Temperature was recorded continuously every five minutes. To avoid direct heat exchange between the heat pad and the data logger, we placed the heat pad at the end of the trap close to the back door, as far away from the data logger as possible. To quantify the heat output of the heat pads through time, we placed a data logger below a hand warmer in six different trials, recording temperatures every five minutes during a 12-hour period. All experiments were conducted during winter 2021.