Estimating density of mountain hares using Distance sampling: a comparison of daylight visual surveys, night-time thermal imaging and camera traps

Carlos Bedson*, Ed Harris, Phillip Wheeler, Neil Reid, David Mallon, Huw Lloyd, Richard Preziosi

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Survey of cryptic, nocturnal animals is logistically challenging. Consequently, density estimates may be imprecise and uncertain. Survey innovations mitigate ecological and observational difficulties contributing to estimation variance. Thus, comparison of survey techniques are critical to evaluate estimates of abundance. We simultaneously compared three methods for observing mountain hare (Lepus timidus) using Distance sampling to estimate abundance. Daylight visual surveys achieved 41 detections, estimating density at 14.3 hares km-2 (95%CI 6.3–32.5), resulting in the lowest estimate and widest confidence interval. Night-time thermal imaging achieved 206 detections, estimating density at 12.1 hares km-2 (95%CI 7.6–19.4). Thermal imaging captured more observations at furthest distances, and detected larger group sizes. Camera traps achieved 3,506 night-time detections, estimating density at 22.6 hares km-2 (95%CI 17.1–29.9). Between methods detections were spatially correlated although the estimates of density varied. Our results suggest that daylight visual surveys tend to underestimate density, failing to reflect nocturnal activity. Thermal imaging captured nocturnal activity, providing a better detection rate, but required fine weather. Camera traps captured nocturnal activity and can operating 24/7 throughout harsh weather, but require careful consideration of empirical assumptions. We discuss the merits and limitations of each method with respect to the estimation of population density in the field.
Original languageEnglish
JournalWildlife Biology
Publication statusAccepted - 27 Apr 2021

Keywords

  • Cryptic animals
  • Uplands
  • Survey methods
  • Population monitoring
  • Distance Sampling
  • camera trap
  • Thermal imager

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