A line in the sand
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Transcript for YouTube ‘A line in the sand’
Exhausted from a long hunt an Australian
sea lion hurtles towards the shallows, towards the
shore having had her fill of squid,
cryptic fish and small crustaceans she
must haul out rest and feed her pup.
It's a daily routine her pup will rely
on her milk for 18 months before it's
ready to feed on her own. It’s one of the longest off
spring bonds in the animal world.
This is Lilliput Island, part of the
Nuyts archipelago on the west coast of
South Australia one of the handful of
vitally important Australian sea lion
colonies remaining.
In a single trip
sea lions from these shelter waters will
travel about 50 kilometres from home to
find food. For this colony the foraging
ground is relatively nearby and
neighbours at Blefuscu Island only five
kilometres away travel three times
further to the edge of the continental
shelves for a meal and it's not just her fellow
sea lions that are interested in
her return. A small group of dedicated
scientists in partnership with National
Geographics Crittercam technology have
been studying this colony for several
years. They want to know the intimate
details of their lives and why
mysteriously their numbers continue to
decline and what they've discovered is
astonishing.
Armed with this new found knowledge a line
has been drawn in the sand,
race is now on to reverse the legacy of
the seal trade that once decimated
their numbers
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Here in the protected shallows of Seal Bay
about a hundred kilometres west of the
Lilliput colony, Australian sea lions
frolic with eager divers away from
the dangers of the open sea. The sea
Lions natural curiosity towards swimmers
makes this an unforgettable tourist
experience but it wasn't so long ago the
relationship between sea lion and man
was very different.
Records from the era are
scant but we know the arrival of
European sealers in South Australia was
devastating. Although hunting was banned
in the early 1920s and sea lions given
protected species status in the 1970s
their population hasn't recovered with
less than 12,000 sea lions remaining in
the wild. These unique animals have been
listed as endangered by the IUCN. Since
2008 professor Simon Goldsworthy is one
of the foremost experts on Australian
sea lions and regularly leads
expeditions to survey tag and track sea lions
in the wild. South Australia's really
important for Australian sea lions over
80% around 83 to 85 percent of the
species is restricted to South Australia.
We surveyed across 42 known breeding sites
and what we found essentially is
that there is far fewer Australian sea
lions here than we thought and that
we've had almost a 25% decline in the
last ten years. He and his team have been
working to fast-track research into why
the Australian sea lion population hasn't
recovered including microchipping pups
at the Seal Bay breeding colony and this
enables us to to monitor the survival
and reproductive success of these
individuals throughout their entire
lifetime typically just by walking up
with a long scanner and waving over the
the rear end of the animal and being
able to read that microchip and so we've
been able to learn a lot of very
important information. Like, you
know how long do animals live, when did
they begin to reproduce, so adult females,
how often do they do they give birth and
how successful are they at raising pups through to weaning?.
What age the male's start holding
breeding territories or start guarding
females and how long they live so we're
finding a lot of key information about
the population demography of the species
that is just impossible
elsewhere.
Australian sea lions are
experts in making the most of limited
resources allowing many small
independent colonies to exist across
their range. The key to this strategy is
individual specialisation, each animal
doing something slightly different to
another a slightly different foraging
strategy in a different habitat
targeting different prey. The end result
reduces competition between individual
sea lions and makes limited resources go
further
This individual specialisation is so
profound that it leads to unprecedented
genetic separation between neighbouring
colonies including differences in the
timing of breeding seasons even though
separated by just a few kilometres.
Female sea lions live their entire lives
in the same place despite being capable
of swimming great distances their
intricate knowledge and familiarity with
their foraging habitat and how to find
suitable prey within it is key to their
survival. Australian sea lions are slow
to reproduce investing up to 18 months
of maternal care in a single pup. This
scientists believe is an adaptation to
the relatively resource-poor environment
they call home and go some way to
explaining why their bond to their home
territory is so strong. They can't just get
up and move their breeding site
somewhere else it has to be just right
for them in terms of enabling them to
access food throughout that entire
lactation period which could last 18 months or more.
What we realized now is
that that at a very very young age
these animals pretty much adopt a
foraging strategy and then they stick,
with a female, that is particularly
females will do this and that will serve
them pretty much for the rest of their
life. When we look at a range of colonies
within say oh somewhere like the Nuyts
archipelago near Ceduna where we've got 8
breeding sites within a 40 kilometre
radius of each other so we've got many
colonies that are only
kilometres apart really and we've found profound
differences in the feeding behaviour of
individuals from one Island relative to
the adjacent Island. So for example
Lilliput and Blefucsu islands off the
Franklin's are only 5 kilometres apart yet yet
most of the females breeding at Lilliput
Island all feed most of them feed in
inshore shallow waters averaging only
eleven meters in depth and they're
feeding around the coastal areas and
being very shallow waters in among
seagrass beds and in shallow rocky reefs.
Whereas most of the females on Blefusco Island are heading to the mid to
outer shelf waters they're heading 70 - 80
kilometres away feeding in 70 to 80 to
90 metres of water down to 100 metres of
water and so they're traveling more than
more than two or three times the
distance and diving you know four or
five times six seven fold the depths of
the in shore females. This highly
specialized habitual feeding behaviour
and its close connection with the sea
lions own territory is thought to
stretch back for many generations. For
Professor Goldsworthy it's a sign of a
highly complex and evolved inter
relationship between these animals and
the places they call home it's having a
map in your head. that's what these
animals have when we've when we've
deployed the crew cams on the sea lions, they
know exactly where they are, know
every Rock every crevice every patch of
sea grass every little patch of rocky
reef every patch of sand they know where
they are
all the time and we've got
you know hours of critter cam footage
where you see an animal traveling across
the seabed across this barren sandy
bottom that's fairly featureless and
they're travelling in a straight line
and after after minutes and minutes and
minutes and minutes you'll see out of
the gloom one rock appear
you know and they've just been heading
all to that rock the entire time. They know
exactly where it is and then they'll
spend some time checking out there to
see whether there's anything that they
can eat and then they're off to the next
feature you know so it's a bit like us
going you know walking out of a house
going to the post office and then on to
the supermarket and then on to the
bottle shop or whatever you know they
know exactly where all the key points
and features that are important in their
lives, in this marine environment. You
put them in a completely alien
environment and they probably will
struggle. Although these specialisations
have allowed Australian sea lions to
survive in challenging resource-poor
conditions they also reduce the capacity
of colonies to recover from human
impacts. Across the state a range of
management measures have been
implemented that will hopefully enable
sea lion populations to recover to
reduce the impact of accidental capture
in fishing nets, gill net fishing
closures have been introduced all around
Australian sea lion colonies. Off South
Australia all gill net fishing vessels
are now fitted with video cameras to
monitor sea lion interactions and
bycatch trigger limits have been introduced
across seven zones that limit the number
of sea lions permitted to be killed each
year. If these limits are reached that
zone is closed to further fishing for an
18-month period the time it takes for a
new pup to be raised. State and
Commonwealth governments are working
together too, through Marine Parks to
protect both coastal waters and the open
Ocean. Together these networks of
reserves protect a range of animals and
wildlife but for the Australian sea lion
no reserve is more important than Seal Bay.
When visitors come to Seal Bay they are
essentially you're you're walking into
the sea lions bedroom really.
They return ashore from foraging trips
and they’re there essentially to rest and
to sleep and and also all their social
interactions occur there that that main
beach at seal bays is not a lot of
breeding beaches as such. The breeding
tends to happen just to the sides of
that beach and into the adjacent bays at
the side so the animals that are
actually present on that beach where
visitors can undertake a guided tour. The animals
are there on their own accord and so
it's fantastic that you know essentially
despite I guess the presence and of
people there almost every day of the
year
these animals are quite happy to to to
share it with people. Here access to this
important breeding colony is controlled
within Seal Bay Conservation Park and
southern Kangaroo Island Marine Park. Not
even scuba divers or swimmers are
allowed to enter the Marine Park
restricted access zone. Further out to sea
the adjoining Murray Commonwealth Marine
Reserve provides some additional
protection to the ocean environment and
the animals that call it home.
While conservation of the breeding
colony is the highest priority for seal
Bay the carefully managed tourist areas
of the park allow for an unforgettable
meeting with these remarkable animals in
their natural habitat. So we can actually
walk right up to where a sea lion is and
observe them because they feel quite
safe with that barrier and we've just
got you know certain practices of how we
approach and the guides can read
their behaviour very well, so we know when
they are getting frightened and if they
do then we step back and everything like
that. Also when we're on the beach -
if a pup comes up to us you know we keep
our feet still and sometimes they get
really curious they'll come up and smell our shoes.
It's one of the state's most
important conservation initiatives in
action it's also one of the few places
Where tourists can walk amongst the sea lions
on the beach and see them basking after
a long day's hunt or feeding their pups.
With this suite of protections now in
place researchers hope to see an
increase in the number of sea lion pups
over the next decade. Until then places
like Seal Bay are the best way to see
Australian sea lions in the wild.
Protected in their
natural habitat
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