Rangataua Forest on the slopes of Ruapehu

Image: Herb Christophers | DOC


Jess Scrimgeour monitors bats to make sure they're still doing well in the presence of predator control.

Jess Scrimgeour.
Jess Scrimgeour releases a bat
Image: Ben Goldfarb ©

It's just as well Jess Scrimgeour is based in Taupo. It puts her at the heart of her work from the northern Waikato and as far south as the Tararua Ranges working on a wide variety of species from whio to kiwi and giant Powelliphanta snails.

"I’ve even been working on a few new and interesting projects with black-billed gulls and Mahoenui giant weta recently but bats are especially close to my heart".

Jess works ‘hands-on’ with short-tailed bats at several sites in the North Island (Pureora, Southern Ruapehu and Tararua Ranges). She monitors the bats to ensure they are still doing well in the presence of predator control.

One of only two species of bat left in New Zealand, short-tailed bats are found nowhere else in the world. Short tailed bats forage on the ground, making them even more vulnerable to predators. They are communal roosting bats, restricted to old-growth forest with hollow trees for roosting.

Counting and tagging bats

Jess picks up the story. “We catch bats in mist-nets, attach transmitters and follow them to roosts. Then, we count the rate at which they come and go from the roost. A few years ago we counted about 6,000 bats emerging from one roost tree in Southern Ruapehu. They were flying out at such a rate, that even when we slowed the video footage down, it was difficult to count them!”

“Counting bats gives us more information on the use of historical versus unknown roosts and bat movements within the forest. Just as important, it gives us a population trend over the long-term in the presence of stoat control.”

At Pureora Jess and the team tag the bats at the roost to monitor survival of adults and juveniles where ground-based toxins are used to reduce predator numbers. This also helps us understand the movement patterns of the bats between monitored roosts, including the timing of formation of large, communal roosts.

Bat close-up.
Bat close-up
Image: Tertia Thurley | DOC

Bat mistnetting.
Bats are caught in mist nets as they leave their roost
Image: Korty Wilson ©

Bats are vulnerable

Bats are not in the spotlight like kiwi, kokako or whio. We have to look at the whole ecosystem. Bats, like much of the native wildlife, are vulnerable to rats, stoats, possums and cats.

By controlling these pests, the bugs, birds and plants get a chance to recover. If there is pest control to protect the better known species, bats will benefit from that control too. 

The communal roosting habit makes them extraordinarily vulnerable to predation if a stoat finds the roost.

Bat weighing.
Jess Scrimgeour weighs a bat
Image: Ben Goldfarb ©

Releasing a bat.
Releasing a bat at night
Image: DOC 

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