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 From
the Field-
Steller
Watch, July 2005
New Arrivals
A
small but intrepid group of scientists have spent most of the last year
observing Steller sea lions on a small remote Island in Alaska. We have
been following their research in "Steller Watch". This July
update on their study and experiences is just in.
The
sun is shining, the skies are blue, and the sea lions are currently hauled
out on South West Brothers Island. We are in the early stages of the sea
lion breeding season, and while most mating and births occur on special
sites called rookeries, it is not uncommon to see them on other haulouts.
We have not observed any mating yet on our local haulout, but we have
noticed an increased presence of large bulls and sub-adult males (SAMs)
over the past month and a corresponding increase in aggressiveness between
each other and toward the females.
Michelle
observed the island's first pup of the year – a round mound of dark
brown fur – on June 4 (ironically, this was the very same day we chose
to begin classifying last year's pups as juveniles, the term for 1-4 year-olds).
Newborn pups and their mothers usually stay on the rookery for several weeks
or longer after birth, in order to build up their strength before attempting
to journey to haulouts. This led us to believe the pup Michelle spotted
was born here.
Now
that the sea lions have returned after their lengthy spring absence, we
have resumed observing the relationship between them and the local bald
eagles. I recently observed an adult bald eagle returning from the open
water with a fish in its talons. It actually landed in an unoccupied area
of the haulout and began feeding on the fish. While this might have caused
a commotion several months ago, neither the sea lions nor the eagle seemed
too concerned with each other on this occasion. If I were to speculate,
I would say that the combination of readily available food sources and the
decreased probability of female sea lions aborting on the haulout might
have something to do with it; many pregnant females are either at or en
route to rookeries to give birth. Whatever the case, it seems that the sea
lions have been granted a temporary reprieve from the eagles' aerial assaults.
Boat
Traffic
With
summer just around the corner, the number of tour operations and private
boats coming to view the sea lions has risen considerably. Most boats are
conscious of the fact they are around wild animals and keep a reasonable
distance.  We've
even had a cruise ship pass by the haulout, which provided a surreal contrast
between the nearby sea lions lazing on the rocks and the huge, white floating
city behind them. Not all the boats navigating the waters around
the island are out on tourist excursions. In fact, many are either recreational
or commercial fishing vessels. It is unfortunate that Steller sea lions
find baited hooks and other fishing paraphernalia so irresistible: we have
suddenly seen an increased number of animals with 'flashers' hanging from
their mouths, indicating they have swallowed a hook and line, while the
mouths of others are pierced with halibut hooks. One of the most unpleasant
sights is finding all types of sea lions – from pups to adult males
– with nylon packing straps looped around their necks. These straps
are typically used to hold the lids on bait boxes or to tie together several
boxes, and they often find their way into the water. Once looped around
an animal's neck, the unforgiving nylon slowly cuts into the flesh as the
animal grows, until it can eventually no longer eat or breathe. The ensuing
death is anything but quick, and to helplessly watch a subdued and emaciated
animal in this obviously painful condition is heart wrenching.
I am happy to report that the Steller Watch project
has been extended a couple of months beyond its original end date of mid-July.
Staying on the island until late August or early September will allow
us to determine whether the movement of the sea lions we observed last
August from the main haulout to the island's northern and western reaches
was a chance occurrence. If the animals remain at the main haulout this
August, then we will have reached our goal of collecting a year's worth
of continuous data from one location. But if they move, we will have collected
further evidence that supports the idea that this mid-summer, trans-island
movement occurs annually. Either scenario will provide us with valuable
new information.
Until next time,
Morgan
19 July 2005
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