Damage to sand dunes along the Manawatu-Wanganui coastline is
risking the extinction of katipo spiders in some areas,
researchers say.
"Katipo populations at some sites like Wanganui South and
Castlecliff have been more severely affected than at other
sites," said researcher Jess Costall.
"Perhaps these populations are at risk of local extinction."
New katipo spiders may have to be moved into these areas to
bolster the local populations, she said in a paper published
in the New Zealand Journal of Zoology.
These sites had low numbers of juveniles, which could be
because the female spiders were distributed so thinly the
males were having problems finding mates.
Ms Costall said the decline of those populations was not due
to high number of the South African spider Steatoda capensis
-- which is competing for the same ecological niche on
beached driftwood and sand-dune vegetation.
There were much greater numbers of the South African spider
at Himatangi and Foxton, where there were healthy populations
of the katipo, scientifically known as Lactrodectus katipo.
She said there was a need for increased monitoring of the
species, and reduction and reversal of damage being done to
sand dunes by vehicles, dumping, grazing by hares, and the
spread of exotic plants with dense growth.
Ms Costall and her co-author, Russell Death, called for
continued monitoring of the katipo population along the
Manawatu-Wanganui coastline.
She found that artificial retreats could be put down and
checked at intervals for katipo occupation -- an approach
which took less time than the traditional searching for
spiders on driftwood and in dune vegetation.
Ms Costall said katipo -- like many coastal species -- would
be highly vulnerable to future rising sea levels, and the
coastal dunes in which they lived had already been destroyed
for use as farmland or forest plantations. "Rising sea levels
would further reduce the little suitable katipo habitat we
have left," she said . "Katipo have never successfully
established further inland, so it seems they are dependent
upon coastal dunes for their survival."
The katipo is New Zealand's only native poisonous spider.
