A systematic scanning method to locate cryptic terrestrial species

Abstract

When studying wild animals, consideration must be given to potential detrimental effects of the study technique, particularly if techniques may affect behaviour or energy expenditure. Many small terrestrial species occupy cryptic habitats, the characteristics and locations of which may be poorly understood. To study these habitats, researchers must be able to locate them, but must also consider the potential for disturbance of the organisms and the impacts this may have. Here, we developed and tested a novel, non-invasive method of locating the cryptic hibernation nests of passive integrated transponder (PIT) tagged hazel dormice Muscardinus avellanarius. The use of a powerful PIT tag scanner combined with a systematic search technique resulted in the location of nine wild hibernating dormice. Camera trap recordings indicated no external dormouse activity following detections, indicating minimal disturbance. In addition, eleven PIT tags no longer inside a dormouse were detected on the forest floor during searches. This study demonstrates a non-invasive alternative to techniques such as radio-collaring for small mammals, and highlights potential uses of PIT tags in research beyond identification of individuals, particularly in understanding fine-scale habitat selection.•A systematic search method enabled location of cryptic terrestrial species•The use of PIT tags allows detection with minimal disturbance.

Keywords: A systematic search protocol for locating cryptic, ground-dwelling PIT-tagged animals; Crypsis; Hibernation; PIT tag.

Graphical abstract

Fig. 1

Schematic of search area layout used in blind trials and a study to locate PIT-tagged hibernating dormice using a PIT tag scanning array. A 5000m² search area was delimited and divided into smaller sections approximately 71 m x 7–10m. These smaller sections were walked as repeated transects, each approximately 1–1.5 m from the previous.

Fig. 2

Distances at which a HPR Plus reader with a BP Plus Portable Antenna (Biomark Inc. Idaho, USA) was able to detect a Peddymark Mini ISO microchip (Peddymark Ltd., Bishops Stortford, UK) with dimensions 1.4 mm x 8mm. (a) shows horizontal detection distances, i.e. where the antenna is flat on the floor with the microchip horizontal to the antenna, and (b) shows vertical detection distances, i.e. where the antenna is above the microchip.

Fig. 3

Time taken to find PIT tags in three different habitat types during blind search trials. Where PIT tags were successfully located, there were no significant differences in the time taken dependent on habitat type. The mean time taken to find a microchip in successful trials was 168 ± 73 min. N (mature) = 3, n (mid) = 4, n (young) = 4 trials. Horizontal lines within boxes indicate the median. Lower and upper box edges indicate 25th and 75th percentiles, whilst whiskers indicate the overall spread of the data.