Researchers in a new study say visitor activities in caves in Cambodia pose challenges for bat conservation, noting that human disturbance is often detrimental to populations, which in turn take substantial time to recover from declines.
Researchers carried out their fieldwork in Phnom Chhngok, a limestone karst outcropping popular with tourists in Kampot province. The study was published on Monday in the peer-reviewed PLOS Neglected Tropical Disease journal.
Researchers assessed the reproductive cycles of two species of bats over 23 months while also evaluating the rate of human visitation. Birth peaks, they found, coincided with the most cave visits during the Khmer New Year holiday.
“While the impact of visitor disturbance on population recruitment cannot be empirically assessed due to the absence of historical data for cave bat populations in Cambodia, it is nonetheless likely to have been considerable and raises a conservation concern,” the researchers write. “Uncontrolled human disturbance often leads to decrease in numbers of bats roosting in caves and numerous studies have demonstrated the detrimental effects of cave tourism in particular.”
Neil Furey, one of the study authors, said research worldwide, including in Southeast Asia, has demonstrated that uncontrolled human access and disturbance to caves is detrimental to cave-roosting bats.
For example, a 2016 study found that disturbance during critical periods, such as during reproduction, can lead to the death of young bats after they lose their roost-hold and fall, and it can also lead to females abandoning their roost for less ideal sites where reproduction success is lower.
Ken Sereyrotha, country director for Wildlife Conservation Society, said it is indeed believed that direct human disturbance leads to a decline in bat populations, but that there are other issues involved.
“Human disturbance is just one factor,” he said. “There should be other factors as well, such as climate change.”
The WCS hasn’t conducted any comprehensive research, but there is concern over a decrease in the bat population as they are linked to the health of the agriculture process in the country because they prey on insects.
“[A population decrease] then . . . leads to an increase of pesticides and chemicals to kill all the insects,” he said.
The study’s researchers say they are advocating for sustainable cave management practices in Cambodia, particularly given that many are the site of rituals and are popular among tourists.
Those responsible for the management of cave sites in the country should try to minimise disturbance for the bat colonies during critical reproductive periods, such as during pregnancy, lactation and weaning, which each tend to take place at specific times of year.
“For instance, this could be persuaded through practices, such as: prohibiting visitors to roost locations during maternity periods; ensuring visits by small groups; accompanied by a guide; timed visits; limiting disturbance; and avoiding or reducing lightening, noise, trash, and other anthropogenic disturbances as much as possible,” the study says.
Furey said surveys of 98 caves in three karst regions in Cambodia found that only 10 percent are undisturbed by humans, while caves used for religious and tourism purposes accounted for roughly half of the total, or 45 total.
“On use of caves for religious purposes (Buddhist shrines in this case), we advocate engagement with the Buddhist movement to address disturbance posed by cave visitors in Cambodia and elsewhere,” Furey wrote in an email. “Conservation organisations like Fauna & Flora International are already doing this in Myanmar.”
Sereyrotha said recommendations to minimise human disturbance are useful, but more discussion is needed to find a way to implement them, and to incorporate local communities.
Officials at the Ministry of Tourism and the Ministry of Environment could not be reached for comment.