Action: Impose restrictions on cave visits
- Three studies evaluated the effects of imposing restrictions on cave visits on bat populations. One study was in the USA, one in Canada and one in Turkey.
COMMUNITY RESPONSE (0 STUDIES)
POPULATION RESPONSE (2 STUDIES)
- Abundance (2 studies): Two before-and-after studies in Canada and Turkey found that bat populations within caves increased after restrictions on cave visitors were imposed.
USAGE (1 STUDY)
- Behaviour change (1 study): One study in the USA 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 (bat movements) of a cave myotis colony roosting within the cave.
Cave visits by recreational users may be restricted to reduce disturbance to bat colonies. Examples of such restrictions are seasonal and daily timing of visits to avoid times when bats are vulnerable, closure to parts of caves close to bat colonies, time limits on visits, supervision of visitors by guides or security guards, and restrictions on the use of lights within caves. Often several restrictions will be used in conjunction and the individual effects of each cannot be distinguished. Relevant individual interventions are also discussed separately in this chapter.
Supporting evidence from individual studies
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 infra-red lights.
A before-and-after study in 1983–2009 at one cave in the Rocky Mountains, Canada (Olson et al 2011) found that enforcing restrictions on cave visitors resulted in more bats hibernating within the cave. An average of approximately 450 bats/year hibernated in the cave before restrictions were enforced, and 650 bats/year after. The cave (length 2791 m, depth 220 m) was highly popular with recreational visitors. In 1997, seasonal access restrictions were imposed. In 1998, the area was established as a National Park and signs were erected to inform the public about access restrictions. Active enforcement to restrict recreational visitors in winter months began in 2000. An annual census of visual counts of hibernating bats was carried out in 11 chambers within the cave from 1983 to 2000, followed by a census every other year until 2009.
A before-and-after study in 2002–2008 at a cave system in forested mountains of Turkey (Paksuz & Özkan 2012) found that restrictions put in place to reduce human disturbance resulted in an increase in the number of 15 bat species using two caves in the system. Maximum counts of bats in the two caves were higher after the cave system was opened to tourism and restrictions were put in place (before: 42,800 hibernating and 7,900 breeding bats; after: 54,600 hibernating and 11,000 breeding bats). A third cave in the system, which remained closed to tourism, had similar numbers of bats throughout the study period. Before opening to tourism, recreational users had made frequent uncontrolled visits to the caves. After opening for tourism in 2003, gates were installed on two entrances, daily and seasonal timing of visits were controlled by security guards, tourists were guided along set routes away from colonies with time limits for visits, information signs were erected, and lights were switched off outside of visiting times. The study does not distinguish between the effects of different restrictions carried out at the same time Bat colonies were counted every 40 days with 15 surveys before (2002–2004) and 38 surveys after opening to tourism (2004–2008). Update 2018: The findings of this study have been challenged, see Furman et al. 2012.
Furman A., Çoraman E. & Bilgin R. (2012) Bats and tourism: a response to Paksuz & Özkan. Oryx, 46, 330–330.
- 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
- Olson C.R., Hobson D.P. & Pybus M.J. (2011) Changes in population size of bats at a hibernaculum in Alberta, Canada, in relation to cave disturbance and access restrictions. Northwestern Naturalist, 92, 224-230
- Paksuz S. & Özkan B. (2012) The protection of the bat community in the Dupnisa Cave System, Turkey, following opening for tourism. Oryx, 46, 130-136