Mammoth Cave After Dark: Bat research in the Margaret River Region

As dusk settles around Mammoth Cave, a small team of researchers, Capes Foundation conservation staff and volunteers move through the surrounding forest.

Together, they are gathering evidence about which bat species are present at the site, and how they use the cave and surrounding habitat after dark.

Acoustic recorders are set out around the site, and specialised bat traps are carefully positioned nearby. The survey continues into the night, tracking bat activity until the early morning.

Clues in the cave

The research was prompted by early observations inside Mammoth Cave. Guides had occasionally seen microbats roosting in the cave, while guano, or bat droppings, in some areas suggested bats were using the site over time.
Capes Foundation Conservation Manager Alysha Johnson approached the Conservation Council of Western Australia (CCWA) to investigate further.

Initially we set up an acoustic monitor at Mammoth Cave and the memory card was filled within three days

~ Alysha Johnson

Setting up a harp trap at Mammoth Cave as part of bat survey work — The team setting up harp traps in the forest before sunset.

Since 2024, the research has developed into a bat monitoring program coordinated by the CCWA in partnership with Capes Foundation.

Bat researcher and CCWA Citizen Science Program Manager Kelly Sheldrick conducts the surveys, which combine acoustic monitoring, harp trapping and field observation with the site knowledge of Capes Foundation staff and guides.

The South West is home to several bat species that occur nowhere else in the world, but we still know surprisingly little about these unique animals and how they’re responding to environmental change

~ Kelly Sheldrick

Listening beyond human hearing

The microbats recorded around Mammoth Cave can be difficult to identify in the field. They are small, fast-moving and active after dark, and many use echolocation calls above the range of human hearing.

Ultrasonic detectors record these calls, helping researchers identify which species are likely to be present and when they are active.

Harp trapping provides information that acoustic recordings alone cannot always give. On survey nights, traps are positioned across likely flyways, the routes bats use while foraging or travelling. Each trap uses fine vertical lines above a soft holding bag. When a bat flies into the lines, it slides gently into the bag below, where it can be collected, identified, measured and released.

Each bat is identified, weighed and its age class is assessed. Researchers check for signs of breeding, look for ectoparasites and record features such as forearm length, ears, muzzle, nose, teeth and tail. These details help distinguish one species from another.

After release, researchers can also record the bat’s call as it flies away. These reference calls help link a confirmed species to its echolocation call, improving the accuracy of future acoustic surveys across the south-west.

Conducting surveys allows us to determine whether breeding populations are present in an area, which is critical for assessing population viability.

~ Kelly Sheldrick

Bats recorded at Mammoth Cave

Seven bat species have been recorded or confirmed at Mammoth Cave and its surrounds:

Gould’s wattled bat (Chalinolobus gouldii)
chocolate wattled bat (Chalinolobus morio)
lesser long-eared bat (Nyctophilus geoffroyi)
Western long-eared bat (Nyctophilus major major)
Holt’s long-eared bat (Nyctophilus holtorum)
southern forest bat (Vespadelus regulus)
white-striped freetail bat (Austronomus australis)

Early findings point to the chocolate wattled bat as the most frequently species recorded around the cave.

Interestingly, in Western Australia, chocolate wattled bats roost in caves, whereas the same species in eastern Australia primarily roosts in trees. We know this species once had maternity colonies in caves around Perth, however these colonies no longer exist.

~ Kelly Sheldrick

The surveys are also recording seasonal patterns in bat activity around caves. Early observations of autumn activity are prompting new research questions about the role caves may play at different times of year.

While more research is needed to understand this behaviour, the observations suggest caves may support more than roosting or foraging, potentially playing a role in seasonal social behaviour and other parts of bat life that are still being studied in Australia.

A little-known local

Among the most significant findings was the Western long-eared bat, a south-western endemic species. During trapping, the team confirmed Western long-eared bats near Mammoth Cave, including lactating females.

During our 2024 surveys, we didn’t realise just how uncommon this species would prove to be across our other 27 southwest trapping sites, making their use of the area around the caves particularly significant.

~ Kelly Sheldrick

The Western long-eared bat is restricted to the forests and woodlands of the Warren, Jarrah Forest and Swan Coastal Plain bioregions.

The presence of lactating females suggests the area may be important during the breeding season. It also points to the value of nearby habitat, including mature trees with hollows and lifting bark, insects moving through the forest, sheltered roosts and access to water during hot, dry months.

Small bats, big role

Microbats play an important role in south-west ecosystems, including forests, woodlands and coastal habitats. The species recorded around Mammoth Cave are insectivores, feeding on moths, crickets, grasshoppers, midges and mosquitoes, and contributing to nutrient cycling through their guano.

“Bats down here in the South West, they’re really important for pest control,” Kelly says. “They really help to keep those insect populations in check.”

The research is adding to what is known about the bats using Mammoth Cave and nearby habitat, informing how these areas are monitored and managed over time.

It is important to increase our understanding of what is in our bushland,” Alysha says. “As stewards of these caves, we are welcoming people to site, on to Country, and it’s great to be able to inform the public and spread this knowledge, especially about species that are very under-represented.

~ Alysha Johnson

How you can help

Community observations can help researchers identify where bats are roosting and the habitats they are using. Sightings around properties, buildings and other local places can all contribute to this research.

For practical advice about bats in buildings, refer to the Australasian Bat Society’s Bats in Buildings FAQ. You can also learn more about the region’s bats in CCWA’s Bats of the Southwest booklet. If you find a bat that may need help, avoid handling it and contact a licensed wildlife carer for advice.

Capes Foundation thanks Kelly Sheldrick, the Conservation Council of Western Australia, volunteers and supporting researchers for their time, expertise and field support.

Visitors stand on a viewing platform inside Mammoth Cave, surrounded by tall stalactites and stalagmites in a large, softly lit limestone chamber.

Mammoth Cave After Dark