A census of little penguins on South Australia's Kangaroo Island
has revealed the number of breeding adult birds has fallen by about a
quarter in the past year. Debate is raging about what's behind the
population drop, with some locals blaming the growing number of New
Zealand fur seals.
EMILY BOURKE: A census of little penguins on South
Australia's Kangaroo Island has revealed some disturbing figures: the
number of breeding adult birds has fallen by about a quarter in the past
Debate is raging about what's behind the population drop, with some locals blaming the growing number of New Zealand fur seals.
Clare Hesketh reports.
HESKETH: The latest count shows that in the past 12 months, penguin
numbers have plunged from just over 1,300 last year to about 960 this
In Penneshaw, the colony has almost halved.
have been done at Kingscote since 2006 and numbers there are estimated
to have dropped by more than a third in the six year period.
Danny Brock is a marine scientist with the South Australian Environment Department.
He says the figures are concerning, but not surprising.
BROCK: We have been losing mainland penguin colonies over the last 20
to 30 years across southern Australia, and now also some of the offshore
islands have been experiencing decline.
CLARE HESKETH: Mr Brock says commercial fishing, coastal development and climate change have put pressure on the penguins.
It's thought predators such as cats and New Zealand fur seals are also hitting numbers.
Tomo from the South Australian Museum has been studying dead penguins
found onshore on Kangaroo Island for the past two and a half years.
She's received about 100 specimens in that time.
TOMO: Primary cause of the death is trauma but some animals have got
some infected bug parasite. But most of the animals more look like
possibly predation, but some of them are killed by the traffic accident.
HESKETH: The Kingscote Penguin Centre has been vocal in blaming rising
New Zealand fur seal numbers for much of the penguin decline.
At last count, there were just over 36,000 of the seals on the island.
Brock says that's expected to increase by about 10 per cent a year for
the next decade, partly due to the species' recovery from the end of
commercial sealing in the late 1800s.
But he rejects the Penguin Centre's claims.
BROCK: They are a pressure on penguin populations, but can we say how
much they're doing it and are they solely responsible for the declines,
no we're not in a position to say that yet.
CLARE HESKETH: The
local Liberal MP, Michael Pengilly says it would be a major blow to the
industry if the attraction was no longer there.
The numbers of penguins at Penneshaw have virtually disappeared and at
Kingscote, the numbers are declining. So clearly international visitors
in particular who like to look at the penguins and their activities are
struggling to find them.
CLARE HESKETH: But Danny Brock is hopeful that little penguin numbers on the island will eventually bounce back.
BROCK: I mean if we implement some of the management issues we need to,
then definitely. I mean Phillip Island is the classic example of
penguin numbers recovering when a number of coastal issues have been
dealt with. So I guess it will be watch this space.
Any future island-wide counts are dependent on more community funding
or financial help from the State Government.
Cannell notes that one of the most important findings of the study was
of the correlation between higher sea surface temperatures around April
and reduced breeding performance. Image: WhatsallthisthenA RECENT study has found links between environmental conditions and breeding performance in a colony of Little Penguins (Eudyptula minor) near Rockingham.
Researchers have correlated the strength of the Leeuwin Current and
timing of breeding of the colony on Penguin Island, as well as a link
between sea surface temperature and breeding success.
The correlation is linked to a decrease in many species of fish that Little Penguins feed on.
Murdoch University Research Associate Dr Belinda Cannell says, “When
there’s a strong Leeuwin Current in the summer prior to breeding, the
[penguin’s] laying will end up finishing later.”
Delayed laying is dangerous for the health of the colony.
“The later they lay in the season, the less likely they are to
successfully raise those chicks because it’s moving into the times they
have to moult,” Dr Cannell explains.
Little Penguins are unable to hunt for food during moulting as they are without waterproof feathers.
Later laying times also make for increased mortality rates due to higher temperatures.
“It also means they’re raising chicks when the terrestrial
temperatures are getting very hot, so there’s an increased chance of
chicks dying,” she says.
Dr Cannell notes that one of the most important findings of the study
was of the correlation between higher sea surface temperatures around
April and reduced breeding performance.
“The chicks were lighter when they fledged; there were fewer chicks
per pair, fewer eggs actually hatched and fewer eggs resulting in
successful fledglings”, she says.
A correlation was also found between breeding success and environmental conditions in the winter months of the previous year.
“When the sea surface temperature and the Leeuwin Current were
stronger in the year prior to breeding, the laying of the eggs will be
earlier in the year.
“The earlier they lay, the more likely they are to lay two clutches,
the healthier the chicks are and the more likely they are to survive.”
The analysis uses data from between 1986 and 2008, with various
measures of breeding performance being compared to oceanographic data to
develop statistical models. These models are then tested against new
data from 2009 to 2011.
Dr Cannell says the study is valuable as one of few long-term data
sets nationwide for marine fauna, describing the penguins as “ideal
sentinels of climate change.”
She says the colony of Little Penguins is an excellent way of evaluating changes to the environmental system as a whole.