Study

Behavioral responses to barriers by desert tortoises: implications for wildlife management

  • Published source details Ruby D.E., Spotila J.R., Margin S.K. & Kemp S.J. (1994) Behavioral responses to barriers by desert tortoises: implications for wildlife management. Herpetological Monographs, 8, 144-160.

Actions

This study is summarised as evidence for the following.

Action Category

Install barriers along roads/railways

Action Link
Reptile Conservation

Install tunnels/culverts/underpasses under roads/railways

Action Link
Reptile Conservation
  1. Install barriers along roads/railways

    A replicated study in 1991–1992 in an outdoor facility and along a highway in Nevada, USA (Ruby et al. 1994) found that desert tortoises Gopherus agassizii interacted less with solid than non-solid barriers and that a concrete barrier was effective in keeping tortoises from a road. In daytime, desert tortoises spent less time close to and touched or pushed solid barriers less often (4–19 minutes, 0.4–4 touches/trial, 0.1 pushes/trial) than non-solid mesh barriers (5–23 minutes, 2–12 touches/trial, 5 pushes/trial) and in shorter trials made less attempts to climb over solid than non-solid fences (30 minute trial: 1 attempts/trial vs. 2 attempt/trial, 2 h trial: 0.1 vs. 0.1, night time: 1 vs. 0.1). The authors reported tortoises frequently attempted to walk through fences they could fit their head through. In a separate maze experiment, tortoises showed no preference for solid or mesh fencing (see paper for details). In a trial by a highway, nine of 10 tortoises approached a concrete barrier and walked along it for an average of 13 m before seven walked away from the highway (the remaining two tortoises settled in place). Tortoises were placed individually in pens with solid (e.g. cabin timber, aluminium flashing, cement blocks, telephone poles) or non-solid walls (e.g. chain link, chicken wire, mesh cloth) for 30 minute (solid: 41 trials, non-solid: 22), 2 hour (160, 100 trials) or overnight trials (40, 80 trials) and behaviours monitored. Tortoises participated in one trial/wall material and three trials maximum each. In separate trials, 16 tortoises were placed in a T-shaped maze with a choice between navigating towards solid or mesh fencing (40 total trials) and 10 tortoises were placed by a concrete barrier next to a highway and observed. All trials took place in 1991–1992.

    (Summarised by: Maggie Watson, Katie Sainsbury)

  2. Install tunnels/culverts/underpasses under roads/railways

    A replicated study in 1992 in an outdoor facility in Nevada, USA (Ruby et al. 1994) found that over half of desert tortoises Gopherus agassizii entered tunnels of a suitable size during trials, of which around half went all the way through tunnels. After 30 minutes, 12 of 16 tortoises had entered tunnels of a suitable width for their size and seven of the 12 tortoises escaped through or moved to the end of the tunnel. Two tortoises stopped in the tunnel and three tortoises entered the tunnel and returned to the pen. Four tortoises investigated tunnel openings but did not enter. In September 1992, sixteen tortoises were placed individually in the middle of a walled pen (4.6 x 4.6 m) with five tunnels of varying diameters and lengths located around the pen edge providing a choice of exit points (narrow: 10 cm wide x 150 cm long and 10 cm wide x 90 cm long; medium: 19 cm wide x 120 cm long; wide: 29 cm wide x 280 cm long and 29 cm wide x 136 cm long). Tortoise behaviour was observed for 30 minutes and recorded.

    (Summarised by: Maggie Watson, Katie Sainsbury)

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