Feature: Stony Hill Cave

Cave purchase crucial to protect only known maternity roost of Critically Endangered bats

by Kristen Pope

Preserving a Cave to Save the Jamaican Flower Bat

Left: Entrance to Stony Hill Cave | Right: Jamaican flower bat (Phyllonycteris aphylla)

Left Photo: Dr. Melquisedec Gamba-Rios
Right Photo: Sherri and Brock Fenton

n a Jamaican hill overlooking the ocean, new development is transforming the landscape. Gorgeous views and a COVID-era desire to get out of big cities like Kingston led to people snapping up countryside land and building homes. This area, in northeast Jamaica near the town of Port Antonio, is a very sought-after area for home building.

However, it is also the site of Stony Hill Cave, the only known maternity roost for the Critically Endangered Jamaican flower bat (Phyllonycteris aphylla).

Development is very close to the cave, but even though the land surrounding it was already subdivided for residential use, landowner Donald Moore didn’t want human encroachment to alter or cover the cave and harm the bats. Instead of selling to developers, he agreed to sell a 0.1-hectare piece of land, including the cave’s mouth, to Jamaica’s Natural Resources Conservation Authority (NRCA), National Environment and Planning Agency (NEPA), and Bat Conservation International (BCI) to protect the resident bats.

Looking into Stony Hill Cave

Photo: Dr. Winifred Frick

“The cave itself is in a very precarious spot in that the entrance to the cave is about 20 feet from a wall and the wall is about three feet from the actual main road into the community, so it’s right against the main road,” says Damany Calder, Environmental Officer of the Ecosystems Management Branch at NEPA.

However, though the faint whiff of guano (bat excrement) is detectable from time to time, the cave is not obvious to the casual observer. “You could drive along the road and, unless you know it’s there, you would drive right past it,” says Dr. Jon Flanders, BCI’s Director of Endangered Species Interventions.

“From a conservation point of view, building anything on the land parcel we have purchased—even if it doesn’t damage the cave—would be catastrophic to the bats using it and probably signal the demise and the extinction of the Jamaican flower bats,” adds Dr. Flanders.

This land purchase is part of an on ongoing effort among collaborators to study the cave and its bats, and protect it. Several expeditions to the cave have resulted in scientists gathering data about the Jamaican flower bat and the other species of bat using the cave. BCI’s Subterranean team also worked with partners to conduct a full LiDAR scan charting the cave and its passages. They discovered that a public road, which is a main thoroughfare for the village, runs atop part of the cave. This valuable knowledge can help guide roadwork so that it is conducted in a way that is sensitive to the cave and its bats.

Since 2017, BCI and NEPA have worked together to protect bat species in the cave from threats like property development, microhabitat changes impacting the cave’s temperature and humidity, and deforestation, which is a threat because Jamaican flower bats are pollen and nectar feeders that are also believed to eat fruit, and they need a place to search for food.

Researchers have collected data from Stony Hill Cave on several expeditions, including one in December of 2018.

Photo: Dr. Jon Flanders

Jamaican flower bats like it hot

Home to 21 species of bats, the island of Jamaica is incredibly biodiverse. The Jamaican flower bat is endemic, or found only on Jamaica, and was presumed extinct for 20 years until it was rediscovered in Stony Hill Cave in 2010. The cave is the only known maternity roost for the Critically Endangered species.

Stony Hill Cave is a “hot cave” with temperatures that can exceed 100 degrees Fahrenheit in some areas with up to 90% humidity. Jamaican flower bats need the heat and humidity, and changes in microclimate can make the cave unsuitable for them. Stony Hill is one of the few hot caves left in Jamaica, so if the bats are pushed out by changes in temperature or humidity, there may not be anywhere for them to go. Much of the cave’s heat comes from the thick layer of decomposing guano on its floor.

Protecting Bats From Cats

Predator-proof fence planned for St. Clair Cave in Jamaica

In central Jamaica, St. Clair Cave is the last known roost of the Critically Endangered Jamaican funnel-eared bat (Natalus jamaicensis), which may only have 250 or fewer individuals remaining. Up to 2 million bats, including at least 10 different species, live in this cave. High temperatures and humidity levels in some spots make this cave an enticing bat habitat.

Bat Conservation International (BCI) is working with NEPA, the Jamaican Cave Organisation, Pacific Rim Conservation, and other partners to help conserve this very fragile cave. The cave is remote and not currently under development pressure, but scientists are concerned about the impact of feral cats hunting and eating the bats that live there.

This fall, BCI scientists will return to the cave to work with NEPA and the local community to start building a predator-proof fence to keep the bats safe from cats. The partners will also continue their other collaborative efforts, including using camera systems for remote monitoring.

Cameras at Stony Hill Cave help record activity near the cave.

Photo: Damany Calder

Donald Moore stands near the entrance to Stony Hill Cave, which he sold to conservation groups to protect bats.

Photo: Damany Calder

The Critically Endangered Jamaican flower bat was presumed extinct for 20 years until it was rediscovered in Stony Hill Cave in 2010. The cave is the only known maternity roost for the species.

The maternity roost at Stony Hill Cave contains over 500 bats—the largest roost of the species ever observed. It is the only place where Jamaican flower bats are known to reproduce, though some males were spotted in a different cave in northwest Jamaican in 2019.

Complicating detection efforts, the species is especially hard to find because it is difficult to detect with standard acoustic monitoring gear.

Since much of the cave’s heat comes from decomposing bat excrement, scientists are looking to guano harvesters—people who collect guano for agricultural fertilizer—to help preserve the cave’s characteristics.

Avoiding cave disturbances

In Jamaica, bat guano is often used as a fertilizer for agriculture. Calder says, “It is believed to be one of the best fertilizers for marijuana, so it’s used mostly for that crop.” To collect it from Stony Hill Cave, harvesters will sometimes park along the road, hop over the two-foot-tall wall, and enter the cave to collect it. Buckets filled with guano can sometimes be found along the side of the wall waiting to be picked up.

Removing guano also alters the fragile microhabitat. If there isn’t enough decomposing guano in the cave to maintain the high temperature and humidity the bats need, the cave will no longer provide suitable habitat for them.

“When a certain quantity of guano is removed, it changes the average temperature,” Calder says. “The bats aren’t as happy, and it slows down their reproductive success.”

When people enter the cave to collect guano, they also bother the bats. “If the bats are breeding and they have pups, and the pups are disturbed, they’re likely to fall,” Calder says. Once they fall to the cave floor, the pups—which are not yet able to fly—cannot get up and are devoured by cockroaches and other cave-dwelling insects.

A Jamaican flower bat in Stony Hill Cave

Photo: Dr. Winifred Frick

Some methods of harvesting guano—such as using kerosene lamps to light the interior—can cause damage, like leaving toxic soot behind. Other harvesting methods involve trying to “smoke out” the bats, much like one would smoke bees out of a hive. While the bees come back after the smoke clears, the bats often do not. Thankfully, these destructive harvesting methods don’t appear to be in use at Stony Hill Cave, and the project collaborators want to work to inform community members about the bats in order to help protect the cave.

“Protecting Stony Hill cave is a significant step forward in the long-term protection of this Critically Endangered bat. I’m very proud of this success with all our partners.”
—Dr. Jon Flanders

To learn more about the frequency and volume of guano extraction without disturbing the bats, the partners set up infrared camera traps outside the cave. These cameras have photographed everything from people collecting guano to feral cats snatching up bats to eat. Since cats and mongooses have been spotted eating bats at the cave, Dr. Lindsay Young, Pacific Rim Conservation, is leading the effort to explore the possibility of installing a predator-proof fence by the cave.

However, before any fence is built, the partners want to involve the community, and get neighbors engaged with cave protection efforts. As one part of this effort, Moore, who has a home right by the cave, took a look at the images of people harvesting guano, and when he realized he knew some of them, he talked to them and asked them to stop going into the cave.

Dr. Jon Flanders preparing a hand net to catch bats near Stony Hill cave.

Photo: Dr. Melquisedec Gamba-Rios

“We have to get the community to be the eyes and ears in terms of preventing people from going in there,” Calder says.

They are looking at a variety of options, including signage or perhaps raising the wall separating the cave from the road, as long as they can do so without impeding the bats’ flight path. They are also exploring the idea of providing bat boxes or bat condominiums to provide a way for guano collectors to retrieve guano for fertilizer without entering the cave, though no final decisions have been made yet.

Meanwhile, as NEPA and partners work with community members, researchers are also working to learn more about the Jamaican flower bats’ breeding season, foraging habits, and behavior. They have also collected genetic material, like fecal samples, to learn more about the bats that use the cave, including what they’re foraging for and how far they go to feed, so they can focus on protecting those areas.

While there is more work to do, safeguarding the mouth of the cave is a crucial step to protect the Jamaican flower bat.

“Protecting Stony Hill cave is a significant step forward in the long-term protection of this Critically Endangered bat,” Dr. Flanders says. “I’m very proud of this success with all our partners.”

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