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Providing evidence to improve practice

Individual study: Effects of cave tours on breeding Myotis velifer

Published source details

Mann S.L., Steidl R.J. & Dalton V.M. (2002) Effects of cave tours on breeding Myotis velifer. The Journal of Wildlife Management, 66, 618-624


This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.

Impose restrictions on cave visits Bat Conservation

A study in 1997–1998 in one cave in Arizona, USA (Mann et al. 2002) found that reducing the number of people within cave tour groups did not have a significant effect on the number of take-offs, landings or overall activity of a roosting cave myotis Myotis velifer colony. A similar number of take-offs and landings were observed, and a similar proportion of the colony was active when tour groups had 1–3 people or 6–8 people (data reported as statistical model results). A colony of 1,000 cave myotis bats roosted in a large cluster within one room of the cave. Experimental tours were carried out through the room with five replicates of each of 24 treatment combinations. Treatments included size of tour group (0, 1–3 or 6–8 people), light intensity and colour (no light, low intensity white light, full red light, full white light), and voice intensity (no people talking, all members of group talking). A total of 120 experimental cave tours were carried out between April and September in 1997 and 1998. Bat behaviour was observed with a night-vision video camera and infrared lights.

(Summarised by Anna Berthinussen)

Restrict artificial lighting in caves and around cave entrances Bat Conservation

A controlled study in 1997–1998 in one cave in Arizona, USA (Mann et al. 2002) found that using low intensity white lights or red lights within the cave resulted in fewer flights by roosting cave myotis bats Myotis velifer than when full white lighting was used, but the number of bat movements was similar between all three light treatments. When compared with full intensity white lighting, low intensity white lights or red lights resulted in fewer take-offs (full white: 23; low white: 12; red: 14) and landings (full white: 20; low white: 11; red: 12). However, the overall activity of the colony (all bat movements) did not differ between the three light treatments (full white: 64% of the colony active; low white: 62%; red: 63%). All three measures of bat activity were lowest when no lighting was used (take-offs: 9; landings: 9; proportion active: 54%). A colony of 1,000 cave myotis bats roosted in a large cluster within one room of the cave. Experimental tours were carried out through the room with five replicates of each of 24 treatment combinations. Treatments included light intensity and colour (no light, low intensity white light, full red light, full white light), size of tour group (0, 1–3 or 6–8 people), and voice intensity (no people talking, all members of group talking). A total of 120 experimental cave tours were carried out between April and September in 1997 and 1998. Bat behaviour was observed with a night-vision video camera and infrared lights.

(Summarised by Anna Berthinussen)

Minimize noise levels within caves Bat Conservation

A controlled study in 1997–1998 in one cave in Arizona, USA (Mann et al. 2002) found that experimental cave tours with groups that did not talk resulted in fewer take-offs and landings by a roosting cave myotis Myotis velifer colony than when groups did talk, but talking did not have a significant effect on overall colony activity. Bats had fewer take-offs and landings when groups did not talk (take-offs: average 13; landings: average 12) than when all members of the group talked (take-offs: average 16; landings: average 14). Overall activity of the colony (all bat movements) was similar when groups did not talk (average 59% of colony active) or when all members of the group talked (62%). A colony of 1,000 cave myotis bats roosted in a large cluster within one room of the cave. Experimental tours were carried out through the room with five replicates of each of 24 treatment combinations. Treatments included voice intensity (no people talking, all members of group talking), light intensity and colour (no light, low intensity white light, full red light, full white light), and size of tour group (0, 1–3 or 6–8 people). A total of 120 experimental cave tours were carried out between April and September in 1997 and 1998. Bat behaviour was observed with a night-vision video camera and infrared lights.

(Summarised by Anna Berthinussen)