Setback for Kapiti bat translocation
20 February 2006
Setback for Kapiti bat translocation
A ground breaking plan by the Department of Conservation to establish a colony of short tailed bats on Kapiti Island has suffered a setback with the deaths of more than half the bat pups destined for a second transfer to the island.
Eight of 14 pups born in captivity at the Pukaha Mount Bruce National Wildlife Centre died following their births in early January, most of them in the last fortnight. Four of 17 pregnant females captured from a threatened colony in the Tararua Forest Park in December have also died.
Just three bat pups are now being taken to Kapiti Island today, joining bats successfully transferred to the island a year ago to establish a new population there. The other three will remain in captivity to enable the development of husbandry techniques for bats in captivity, DOC fauna scientist Lynn Adams said.
Autopsies reveal that four of the bat pup deaths were associated with aggression from other bats.
“We are still uncertain why the others have died.” Ms Adams said.
“Some may have died subsequent to their mothers dying.”
Two female adults died shortly after giving birth, from suspected birth complications, and another two died in early February. (Three of the surviving 13 females apparently miscarried.) The adult bats will be returned to the Tararua Forest Park.
The deaths have come as a blow to DOC staff involved in the project after the success of last year which saw 20 of 25 bats born in captivity transferred to Kapiti Island. It was the first time in the world that bats were successfully translocated to another location for conservation purposes. At least nine of the bats are known to still be on Kapiti Island.
“Even if these are the only ones still alive the survival rate of juveniles is still much higher than that of some of the bat species in the wild around the world,” Ms Adams said.
Last year six of the 25 adult bats caught died in captivity at Pukaha Mount Bruce and five pups were lost. This rate was probably similar to survival in the wild.
“We are not entirely sure why there is a higher mortality rate this year but a number of the dead bats had been bitten and it may be that this year we were unlucky enough to have caught a particularly aggressive female.
“We have also been looking at the roost design which currently doesn’t perfectly mimic a natural roost and we’ll look at redesigning the roost in the hope that this may improve things next year.
“We have been learning more about the health risks to bats during a normally stressful time in a bat's lifecycle and autopsies have now given us more clues about the risks associated both with this programme, and this time in the bat’s life cycle.”
It was also discovered that nine of the bats on Kapiti had a condition causing scabs on their sensitive ears.
“The problem was successfully treated and all nine are doing well but we are still uncertain why they developed the scabs. We were hoping to investigate the problem in more depth this year, but now with only three bats to transfer, it will be more difficult to detect problems on Kapiti.”
Like their predecessors, the bats being taken to Kapiti Island today will be held in an enclosure for several weeks while they acclimatise to their new home.
Ms Adams said while these setbacks had slowed progress, DOC was still hopeful of establishing a population on Kapiti.
“There is always a level of risk in projects that are developing new techniques and we knew from the outset that this project would be difficult.
“However the lessons learnt from this project will be of great benefit to bat conservation throughout the world.”
The success of the translocation project will be assessed after three years.
Believed to be the last remaining population of short-tailed bats in the south of the North Island, the Tararua Forest Park colony of around 200 bats had been isolated from other bat populations for about 90,000 years by volcanic activity, and glaciation. As a result the bats are genetically distinct from other short-tailed bat species. They are now thought to be under siege from predators such as ship rats and stoats and at risk of extinction.
When a thriving population is established on Kapiti Island, attempts may be made to transfer bats back to other sites in the lower North Island.
Short-tailed bats aid the pollination of native plants and establish their roosts in tree cavities deep in the island’s older forests. Bats are New Zealand’s only terrestrial mammals.