The rare native bat populations of the Eglinton Valley have joined the list of native animals affected by bad weather in Fiordland.
A wet spring and heavy rain in the January roosting season appear to have held up the development of young bats - while blue duck and brown teal have also been hit by the weather.
Department of Conservation biodiversity ranger Hannah Edmonds said that, in a normal year, young bats would be emerging from their roost by now.
"It's been an interesting year this year," she said. "It seems to be the young aren't leaving the roost yet . . . maybe the wet spring has something to do with it."
The valley is one of a handful of places where long-tailed and short-tailed bats - New Zealand's only native land mammals - can still be found on the mainland.
DOC has monitored the bats during three weeks each January since 2005.
The short-tailed bats were discovered in the valley in 1997. There is only one other population on mainland South Island.
This year, four rangers were monitoring the short-tailed bat colony and three were studying the long-tailed bats in the area, Ms Edmonds said.
The population of critically endangered short-tailed bats - known for their habit of hunting insects on the forest floor, like their flightless ancestors - appeared to be stable, but it had been harder than usual to get a firm count, she said.
This was partly because of bad weather, because flooding made it impossible to get across the Eglinton River from Knobs Flat, the team's base, to the bat colonies.
It took more than a week to catch and tag a lactating female to lead the team to a roosting site.
"That usually happens in the first couple of nights," Ms Edmonds said.
The lack of young bats flying has also made it harder to tag new bats for monitoring. Each year the team aims to catch at least 200 bats and give them a microchip tag.
This year, most of the bats caught had already been tagged, she said.
The bats are just one of several native species to be affected by the wet southern spring.
Biodiversity ranger Andrew Smart, who specialises in duck conservation in Fiordland, said the spring and early summer had been as bad as he had seen.
Whio (blue duck) nests in mountain rivers were washed away by flooding in September and October.
Mr Smart said the birds had re-nested in the rivers, but further floods in January had once more caused damage. The pateke (brown teal) population had also been affected, Fiordland, he said.
The river gauge in the Arthur Valley had recorded two floods, on January 2 and 10, four metres above normal levels.
He said this was almost unprecedented - DOC considered it a bad year if there was one flood as big.
- The Southland Times
Subscribe to a digital replica of The Southland Times.
Southland Times subscriber news and information.
Click here for information about advertising with The Southland Times.