to save dolphins
March 02, 2004
By Kim Griggs
In Wellington, New Zealand
New Zealand is aiming to use satellite tagging
to try to save Maui's dolphins, the world's
most endangered marine mammal.
New Zealand's public conservation agency, the
Department of Conservation, (DOC), is testing
the system by tagging three Hector's dolphins.
These animals are also endangered, but are more
populous at around 7,000 than Maui's dolphins,
which number less than 150.
If the trial of the satellite tags proves successful
on the Hector's dolphins, then the critically
endangered Maui's may also be tagged.
This, the DOC argues, would give it sorely needed
information about where these small cetaceans
of dolphin with
"Our efforts to save New Zealand's rarest
dolphin are being hampered by what we don't
know about them," said Rob McCallum, from
the Department of Conservation.
Local conservation groups are vehemently opposed
to the trial.
Maui's dolphins are now protected through a
ban on the use of commercial set nets within
four nautical miles of the west coast of New
Zealand's North Island, where the dolphins are
known to live.
In the past three and a half years, eight Maui's
dolphins have washed up dead.
But since the netting ban came into force late
in 2002, only one has been found dead.
The worry for the DOC is that the dolphins
have been spotted well outside the protected
area, as far as 15 nautical miles from shore
and up to 100 kilometres south of the closed
set netting area.
"We need to find out if Maui's dolphins
move outside the current set netting closed
area," said Mr McCallum.
"If so, we need solid evidence to show
this and to determine how much of their time
they spend in different areas."
Internationally, scientists have tagged other
marine mammals, often with startling results.
Heaviside's dolphins, a close relative of Hector's
dolphin in southwest Africa, were thought to
be an inshore dolphin species.
Satellite tagging has shown that this dolphin
species moves out to and back from the edge
of the continental shelf, about 25 nautical
To test the efficacy of satellite tracking
on the South Island-based Hector's dolphins,
the DOC plans to attach tiny satellite tags
- two matchboxes in length and 50 grams in weight
-to the dorsal fins of three dolphins.
The transmitters are attached with nylon-coated
pins, with fasteners that are designed to eventually
corrode and release the tag from the animal.
For the transmitter to work, it needs to be
above water, so the trial aims to find out if
the swimming style of New Zealand's small dolphins,
which do not dive very deep but do not surface
for long, will allow enough useful data to be
Ban on use of commercial set nets
led to fall in dolphin deaths
Ann Rupley, technical sales manager at the
tags' manufacturers Wildlife Computers, said
dolphins were the ideal animals for the tags.
"They are a good platform for these tags
because they do come up above the surface so
"They are exactly the kind of thing that
this tag was designed for," she said.
But Dr Liz Slooten, a zoologist at the University
of Otago who has studied New Zealand's dolphins
for 20 years, has real doubts that the tags
will provide the right information.
Other non-invasive research methods, such as
acoustic, boat-based and aerial surveys, can
give the same data without the potential for
trauma and damage to the dolphins, she argued.
"All of these methods are absolutely standard
methods used for doing whale and dolphin surveys
not only in New Zealand but around the world.
So there is no convincing argument for this
work," she said.
"If there was a really strong argument
... I'd be out there doing it myself. I certainly
wouldn't be objecting to it."
The tags, Dr Slooten and other opponents argue,
will not give enough fine-scale detail to be
able to pinpoint just where these endangered
But Wildlife Computers' Ms Rupley disputes
that, and says the average fix is plus or minus
350 metres or better.
"They may be as good as plus or minus 150
metres which is certainly close enough to get
a pretty good fix on the animal."
For the local Maori tribe, Ngai Tahu, the plan
makes good sense and they have given it their
"We spent a lot of time thinking about
and talking about this as anybody would,"
said spokesperson Robin Mautai Wybrow.
"We support the department 150 per cent
in terms of what they are attempting to do,
which at the end of the day, for us, is to look
at how they can help our cousins in the North
Island with the Maui's dolphin."
The trial is expected to start soon.
"With less than 150 Maui's dolphins left,
we need to consider all means available to find
out what we need to know to save this dolphin,"
said McCallum. "We can't afford to wait."
Reproduced from BBC Online