A 12-year-old male New Zealand sea lion rests at Cannibal Bay, near Owaka. His branded tag has helped scientists keep track of his movements so they know he travels from the Auckland Islands to Otago's coast every year. Photo by Stephen Jaquiery.
The practice of hot-iron branding New Zealand sea lions ended
in controversy 13 years ago, but research has found it has
not affected their survival.
The branding was part of an experiment by Department of
Conservation staff, who anaesthetised the animals for the
procedure, but it was stopped in 2000 by then Conservation
Minister Sandra Lee, who said she was horrified by the
While it had been approved by Doc's animal ethics committee,
some questioned the animal health and welfare effects.
Thirteen years on, Doc scientists, while acknowledging people
had a problem with the practice, say it provided a wealth of
information on the critically endangered sea lions.
In 2000, Doc branded 300 sea lion pups, aged between 5 and 10
weeks, and 134 adult females.
Doc marine scientist Dr Louise Chilvers said all of the sea
lions' movements had been followed in the years since and the
branding had not affected their survival or their
''For a nationally critical species, we need to understand
what is happening to them.''
Ten years on, a study of the branded females showed all of
the animals were still alive and could be identified by their
brands, even if they had been scarred by shark bites or bites
from other sea lions.
Compared with female sea lions which had only been tagged,
data suggested their survival rates were similar, if not
better, she said.
The study found hot-iron branding could be an effective
method of permanently identifying sea lions, providing robust
parameter estimates and low disturbance in the resighting
process and did not compromise survival.
''We can collect so much better information from them, which
is why it was done in the first place.''
The number on the mature male sea lion photographed by the
Otago Daily Times at the weekend meant it could be
identified as one which travelled to and from Otago's coast
to the Auckland Islands to breed every year.
Two years ago, he had a ''harem'' in the Auckland Islands,
indicating he bred, she said.
The reason for trying different forms of identification was
that plastic flipper tags had a high loss rate, especially
for adult males, which outgrew the tags, she said.
Doc Catlins partnership ranger Cheryl Pullar said seeing
about 30 sea lions at Cannibal Bay was normal at this time of
year, when many of the males came back to Otago after