The Department of Environment, Land, Water and Planning (DELWP) said in summer southern bent-wing bats lived in three caves in Australia to give birth to their young - in Warrnambool and Portland in Victoria and Naracoorte in South Australia.

"The large gathering of bats in these maternity caves increases temperatures in the cave and helps keep the furless pups warm," a DELWP spokesperson said.

The southern bent-wing bat was critically endangered due to significant declines in numbers in recent decades.

The Victorian population is estimated at about 20,000 (18,000 in Warrnambool and 2000 in Portland).

"DELWP scientists undertake monitoring of the Victorian population without lights, using thermal cameras, filming the bats as they fly out of their cave at dusk and use specially designed software to automatically count the number of bats from this footage," a DELWP spokesperson said.

"Pups are counted from infrared images.

"These bats are highly susceptible to disturbance, including from lights and noise when people enter caves, and it is very important that caves where bats roost are not visited by the public."

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During the non-breeding season, the bats are scattered throughout the region in additional caves and rock crevices that have suitable temperature and humidity conditions.

The insect-eating microbat measures 52-58 millimetres long (head and body) and weighs about 15.7 grams, using echolocation to navigate when flying and feeding at night.

Threats to the species suspected of contributing to the decline include loss and modification of roosting caves (particularly maternity sites) and feeding habitats, people entering roost caves, bioaccumulation of pesticides and toxins that could also reduce food availability, disease and introduced predators.

DELWP also predicted climate change, including drought, could also negatively affect food availability, with the risk posed by windfarm development and collision with turbines also being investigated.

In 2019, a National Recovery Team was formed with representatives from Victorian and South Australian government agencies, land managers, researchers and other stakeholders covering a range of knowledge areas including disease management, species ecology and cave management. It led the implementation of a recovery plan.

In 2020, DELWP prepared the plan, which was adopted under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act) as the National Recovery Plan for this species - the first national recovery plan for the species.

The Australian government's Department of Agriculture, Water and the Environment said the long-term recovery objective ensured the breed could survive, flourish and retain its potential for evolutionary development in the wild.

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