Bloody bizarre: New Zealand bat is weird to the core

This article is part of a special Cosmos series where our newsroom journalists follow up science from the archive, to find out: What happened next?

New Zealand scientists keep uncovering new information about native short-tailed bats, with new blood analysis revealing the animals are kooky to the core. 

University of Waikato researchers are studying Aotearoa’s only two species of bat, which are also the country’s only two terrestrial mammals: the long-tailed bat (Chalinolobus tuberculatus) and the short-tailed bat (Mystacina tuberculata). 

Cosmos previously reported on analysis of DNA in long-tailed bat scats to understand the endangered animal’s true diet, and an investigation into the impact of light pollution on bat behaviour.

Now, in yet-to-be-published research, Associate Professor Nicholas Ling is undertaking comparative analysis of bat blood from the two species. 

So far the results confirm his observations: the long-tailed bat is fairly normal as far as bats go, while the short-tailed is “strange in almost every respect”.

Ling says “we thought this would be a nice study to compare the blood physiology of the two species because they have quite different ecologies.”

The blood of the long-tailed bat – cherished by the nation as New Zealand’s ‘bird of the year’ in 2021 – “was exactly as you would expect for a small bodied bat species”, he says.

Like other small bats, the long-tailed bat has a high metabolic rate and more red blood cells carrying high amounts of oxygen. Ling says, red blood cells make up about 45% of blood in humans and about 60% in small bodied bats.

A higher share of red cells makes the blood more viscous and requires more muscular vessels to push it through, he says. “To assist bats in moving this really thick, viscous blood around they have unusual blood vessels, they often have a peristaltic blood vessel to help massage the blood through, particularly on the on the venous side.”

The bat’s blood also has a characteristic called low oxygen affinity, enabling it to offload oxygen efficiently to the flight muscles.

Meanwhile the analysis reveals the short-tailed bat’s blood is “very, very different and completely different to any other bat,” Ling says.

Short-tailed bat blood has the highest oxygen affinity – releasing oxygen at a lower rate – than any bat species analysed.

Ling says there’s a couple of possible reasons. 

One, the bats are lazy, he says. They forage on the ground and seldom fly, so they don’t need of use oxygen as efficiently as bats which fly.

Or, possibly it’s the blood characteristics which lead to this strange behaviour. “Maybe they can’t fly very fast and very far,” he says.

The other reasons might be the short-tailed bats unusual roosting behaviours. 

While some bats can be found on their own in tree cavities, “you also get these really massive communal roosts as well, which can have hundreds or even thousands of bats in them. Often these are really sort of confined spaces.” 

He says maybe these almost hypoxic environments – confined spaces, bats crammed into tree cavities – explain their blood’s high oxygen affinity.

Ling says, contrary to New Zealand’s other beloved bat, everything about short-tailed bats is weird, including their blood.

“Their personalities are completely different to long-tailed bats,” he says. 

“Long-tailed bats are just the loveliest little animals to deal with, short-tailed bats are little horrors, they’re really aggressive, they’ll try and bite you.”