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Rakali
Watch 1999 Results
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By
Michelle Smith
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The population of the Rakali (water rats) inhabiting
the St.Kilda Breakwater between the kiosk and the second set of steps
has been observed by volunteers from Earthcare since October 1997.
The population is highly visible, and volunteers are able to study
the feeding and social behaviour of the animals. Identification of
distinctive marks on individual Rakali is awkward due to inadequate
light, the presence of rocks and waves, and their swimming style (mostly
submerged). It has therefore been difficult
to estimate the size of the population, although we believe there
are about 20 animals that call the breakwater "home". Trapping and
ear tagging has been carried out periodically, with three individual
Rakali captured. Certain measurements are taken to determine the age
of captured Rakali, including the lengths of the body, tail, hind
foot, ear and the white tip of the tail. The condition of both the
coat and the animal is also assessed
The table below illustrates the animals that have
been captured and tagged. Rakali are generally trap shy, and we have
had many instances where an individual has encountered a trap and
run off with fright. To combat this "trap avoidance", it is common
to leave traps for a few days prior to setting them, to enable the
animals to become accustomed to the sight and smell of them. Unfortunately,
we are unable to leave traps unattended at St. Kilda due to the potential
for theft or vandalism, and so we are hoping that persistence will
eventually pay off!
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SEX
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WEIGHT
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BODY
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TAIL
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HIND
FOOT
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EAR
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TAILTIP
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NOTES
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F
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742
GRAMS
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244
MM
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278
MM
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64.4mm
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13.6mm
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-
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Ran
into rocks under bollard 4
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F
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734
grams
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245mm
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284mm
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61.5mm
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5.8mm
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95.3mm
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Good condition.
Rocks b/w bollards 1&2
Tag #
3426
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F
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AS Above
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-
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-
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-
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-
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Recaptured
after 5 minutes
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M
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835
grams
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300mm
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250mm
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67mm
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-
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115mm
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Good condition,
docile. Trapped well under boardwalk
Tag #3427
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As can be seen in this table, three Rakali
have been captured, although the study team has approximately 15 – 20 sightings
per night. We have tried trapping at full tide, half tide and low tide,
and have decided to concentrate our efforts during periods of half tides.
We have also found that rough, choppy conditions hamper the sighting of
Rakali in the water, and they are less active on very windy nights. |
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To
join the Rakali Study Group or get more information |
ST. KILDA BREAKWATER
between the kiosk and the second set of steps.
The monitoring of the Rakali has enabled us to determine some
patterns of behaviour. They emerge at around dusk, and are living amongst
the rocks underneath the entire boardwalk. They tend to swim out to one
of the pylons (where we presume they are prying off mussels or tube worms
to eat), or to the pier, where we generally lose sight of them. They may
also be obtaining mussels and tube worms from the pylons that hold up
the pier. On their return to the boardwalk, they often get out of the
water at the seagrass beds and browse around. They then walk along the
beach, or swim along the beach in the shallow water. It is during this
time that we can observe them running back and forth along the beach,
and in some instances they are only a metre or two away.
We have observed them eating mussels, fish and tube worms (and
a nice diet of seafood-flavoured catfood when in the traps), and they
tend to either eat on the "Feeding rock" or on the beach, although the
Totally Wild crew shot footage of one swimming on its back like an otter,
while eating a tube worm at the same time. Analysis of prey remains in
the feeding tables they leave behind indicate that they also eat a proportion
of crabs and other shellfish. They have also been observed climbing the
chains and ropes of boats that are moored at the marina. They are usually
solitary, but we sometimes see them interacting, and at this time of year
the young should be starting to get out and about.
So if you want to see one of Australia’s most attractive rodents
in their natural environment, please come along and give us a hand. Rakali
Watch takes place approximately twice a month (depending on tides and
weather), so keep an eye out in the next issue of Earthcare News for the
dates, and come and discover the exciting world of the Rakali at the St.
Kilda breakwater
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Contact
Earthcare PO Box 287 Elwood, 3184
copyright
Earthcare St Kilda 2006
Email
earthcarestkilda@gmail.com
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