New Zealand was once home to a giant, burrowing bat that was three times the size of the average bat today.

The extinct creature, which weighed about 40g, represents the largest burrowing bat known to science, and New Zealand's first new bat genus for more than 150 years.

Teeth and bones of the bat were recovered from sediments dated between 16 and 19 million years old, found near the old Central Otago gold and coal mining town of St Bathans.

Burrowing bats, now found only in New Zealand, are peculiar because they not only fly, but also scurry about on all fours over the forest floor, under leaf litter and along tree branches.

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It has been named Vulcanops jennyworthyae, after Jenny Worthy, who was part of the team that found the fossils, and after Vulcan, the mythological Roman god of fire and volcanoes, in reference to New Zealand's tectonic nature, but also to St Bathans' historic Vulcan Hotel.

Its discovery, by Australian, Kiwi, United States and British scientists, has been revealed in a new study, just published in the international journal Scientific Reports.

"Burrowing bats are more closely related to bats living in South America than to others in the southwest Pacific," explained the study's first author, Professor Sue Hand of the University of New South Wales.

"They are related to vampire bats, ghost-faced bats, fishing and frog-eating bats, and nectar-feeding bats, and belong to a bat superfamily that once spanned the southern landmasses of Australia, New Zealand, South America and possibly Antarctica."

Around 50 million years ago, these landmasses were connected as the last vestiges of the southern supercontinent Gondwana.

Sediments in the Manuherikia River were washed through sieves to collect the fossil bones and teeth. Photo / Vanesa De Pietri
Sediments in the Manuherikia River were washed through sieves to collect the fossil bones and teeth. Photo / Vanesa De Pietri

At that point, global temperatures were up to 12C higher than today and Antarctica wasn't frozen, but forested and frost-free.

With the break-up of Gondwana, cooling climates and the growth of ice-sheets in Antarctica, Australasia's burrowing bats became isolated from their South American relatives.

"New Zealand's burrowing bats are also renowned for their extremely broad diet," said Hand, director of the university's PANGEA Research Centre.

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They eat insects and other invertebrates such as weta and spiders, which they catch on the wing or chase by foot. And they also regularly consume fruit, flowers and nectar.

"However, Vulcanops' specialised teeth and large size suggest it had a different diet, capable of eating even more plant food as well as small vertebrates – a diet more like some of its South American cousins.

"We don't see this in Australasian bats today."

The newly described species is also the latest addition to what scientists call the St Bathans Fauna.

They lived in or around a 5600sq km prehistoric Lake Manuherikia that once covered much of the South Island's Maniototo region.

When they lived, in the early Miocene, temperatures in New Zealand were warmer than today and semitropical to warm temperate forests and ferns edged the vast palaeo-lake.

The fossil dig site at St Bathans where the fossilised remains of an extinct burrowing bat, Vulcanops jennyworthyae, were found. Photo / Trevor Worthy
The fossil dig site at St Bathans where the fossilised remains of an extinct burrowing bat, Vulcanops jennyworthyae, were found. Photo / Trevor Worthy

Vulcanops' lineage became extinct sometime after the early Miocene, as did a number of other lineages present in the "St Bathans Fauna" group, such as crocodiles, terrestrial turtles, flamingo-like palaelodids, swiftlets, and several pigeon, parrot and shorebird lineages.

Most of these were probably warm-adapted species.

The group also included the enigmatic St Bathans mammal, whose existence suggested that terrestrial mammals did in fact once live in Zealandia, the recently recognised "eighth continent" that today lies mostly submerged beneath the ocean.

After the middle Miocene, global climate change brought colder and drier conditions to New Zealand, with significant changes to vegetation and environments.

It was likely that this general cooling and drying trend drove overall loss in bat diversity in New Zealand, where just two bat species today comprise the entire native land mammal fauna.

All other modern land mammals in New Zealand have been introduced by people within the past 800 years.

Study co-author Associate Professor Trevor Worthy, a Kiwi scientist now based at Adelaide's Flinders University, said the fossils showed that the prehistoric aviary that was New Zealand also included a surprising diversity of furry critters alongside the birds.

"These bats, along with land turtles and crocodiles, show that major groups of animals have been lost from New Zealand," added another co-author, Professor Paul Scofield of Canterbury Museum.

"They show that the iconic survivors of this lost fauna – the tuataras, moas, kiwi, acanthisittid wrens, and leiopelmatid frogs – evolved in a far more complex community that hitherto thought."

Auckland Council senior biodiversity adviser Ben Paris, better known as NZ Batman, said the discovery was "extremely exhilarating news" for the bat world in New Zealand.

"I am sure it will be quite the conversation point at the upcoming New Zealand bat conference in Taranaki in February," he said.

"It has always been an oddity of Aotearoa to have so few native land mammals, so to add this bat species to our prehistoric fauna alongside our other unique wildlife is very exciting.

"This also gives us an important reminder to 'live long and prosper' in regard to conservation and protection of our remaining short-tailed and long-tailed bats, as they are the last of the significant bat fauna left that still provide important ecosystem services like pollination and insect control."

The bat wasn't the only hefty New Zealand species to be newly described by scientists, long after they were lost forever.

Last year, researchers revealed our country once had its own black swan species that was heavier and larger than their Australian cousins, as well as a giant penguin that was as big as a grown man.