Acceptance of bats to gates at abandoned mines

Published source details Tobin A., Corbett R.J.M., Walker F.M. & Chambers C.L. (2018) Acceptance of bats to gates at abandoned mines. Journal of Wildlife Management, 82, 1345-1358.
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This study is summarised as evidence for the following.

	Action	Category
	Install and maintain gates at mine entrances to restrict public access Action Link
	Install and maintain gates at mine entrances to restrict public access Action Link
	Install and maintain gates at mine entrances to restrict public access Action Link

Install and maintain gates at mine entrances to restrict public access

A replicated, controlled, before-and-after study in 2014–2015 at 11 abandoned mines in southern Arizona and New Mexico, USA (Tobin et al. 2018) found that after gates were installed bat activity levels remained stable or increased at five of seven gated mines and three of four ungated control mines. After gating, bat activity levels decreased at two of seven gated mines and one of four ungated control mines (data reported as bat logger voltage measures). Seven bat species were recorded within the mines (data not reported for individual species). Eleven mines (4–200 m long) with similar characteristics (bat use, mine features, number of entrances) were surveyed. Seven mines had gates (standard square-tube bar gates or corrugated metal culverts with rectangle-tube bar gates, both with 14.6 cm horizontal spacing) installed in winter 2014 or spring 2015. Four control mines were left ungated. Visual observations and bat logger surveys were carried out in June–September 2014 (before gating) and 2015 (after gating).

(Summarised by: Anna Berthinussen)
Install and maintain gates at mine entrances to restrict public access

A replicated, before-and-after study in 2015 at two abandoned mines in Arizona, USA (Tobin et al. 2018) found that bats performed more flight manoeuvres at mine entrances after mock gates were installed than before, but gate material and height had no effect on bat behaviour. Bats performed more energetically demanding flight manoeuvres at mine entrances after mock gates were installed (data not reported). There was no significant difference in bat behaviour between two types of gate material (corrugated metal and non-corrugated high-density polyethylene) or two gate heights (0.15 m and 1.15 m above the ground). Both mines (60–80 m long) had single ungated entrances and were occupied by winter colonies (>100 individuals) of California leaf-nosed bats Macrotus californicus. Round bar gates (14.6 cm horizontal bar spacing) were installed within culverts (76 cm diameter, 1.2 m length) at each of two mine entrances. In March–April 2015, bats were filmed with infrared cameras for three nights before gates were installed, followed by three nights with one randomly chosen gate material/height installed and three nights with the other.

(Summarised by: Anna Berthinussen)
Install and maintain gates at mine entrances to restrict public access

A replicated study in 2015 at 41 abandoned gated mines in Arizona, Colorado, Nevada, New Mexico and Utah, USA (Tobin et al. 2018) found that gate age and design had varied effects on the presence of four bat species, but mine features were more important than gates for predicting presence. Townsend’s big-eared bats Corynorhinus townsendii were found more often in mines with narrower horizontal bar spacing (12–15 cm) than wider spacing (18 cm; data reported as statistical model results). California myotis Myotis californicus and western small-footed myotis Myotis ciliolabrum were found more often in mines with older gates (>10 years old) and less often in mines with angle-iron bar gates than mines with four other gate designs. Cave myotis Myotis velifer were found more often in mines with newer gates (<9 years old) and less often in mines with culvert gates than mines with four other gate designs. Fringed myotis Myotis thysanodes were found more often in mines with gates closer to the entrance (<2 m) with smaller gate areas (<2.5 m²) and wider vertical bar spacing (>0.9 m). Mine features (e.g. elevation, number of levels or entrances) were more important than gate age, location, or design for predicting the presence of all four bat species. Each of 41 mines had one of five gate designs installed: standard round bar (8 mines); standard angle-iron bar (15 mines); standard square-tube bar (7 mines); corrugated metal culvert with square-tube bar (7 mines); ladder gate (4 mines). Fresh guano samples were collected from the mines in June–December 2015 for DNA analysis, and mine features were recorded.

(Summarised by: Anna Berthinussen)