Observations on the behaviour of a pod of killer whales Orcinus orca L. that visited Cork Harbour in 2001

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Observations on the Behaviour of a Pod of Killer Whales Orcinus orca L. That Visited Cork
Harbour in 2001
Author(s): Conor Ryan and Peter Wilson
Source:
The Irish Naturalists' Journal,
Vol. 27, No. 5 (2003), pp. 187-191
Published by: Irish Naturalists' Journal Ltd
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Ir.
Nat. J.
Volume 27
No
5
2003
Observations
on
the
behaviour of
a
pod
of
killer
whales
Orcinus
orca
L.
that visited
Cork
Harbour in
2001
Conor
Ryan
Whitepoint
Drive,
Cobh,
Co Cork
Peter
Wilson
"Blanan", Rushbrooke,
Cobh,
Co
Cork
On 5 June 2001 the
crew
of the Irish
Navy
Patrol
Vessel L.
E.
Rdisin
saw a
pod
of
three
killer whales about
1km off Roches
Point,
Cork
Harbour
(N51?W8?).
The
pod
consisted
of
an
adult
male,
an
immature
male and
an
adult female. Over
the
next
few
days
the whales
were
frequently
seen
around
the
mouth of
the harbour.
On 10
June
they
entered the harbour and
were seen
off the
town
of
Cobh. This
event
was
widely
reported
on
the national
media.
During
their
stay
they generally
kept
to
the
deeper
waters
of
the commercial
shipping
routes
between Cobh and
Whitegate jetty.
However,
they
also
swam
past
Cobh
and
entered
Lough
Mahon,
and
on
one
occasion
they
went
all the
way
to
Cork
City
(15-16
June).
On
the
morning
of
8
July
a
dead
whale
was
found
floating
at
the mouth
of
the harbour. This
was
later confirmed
to
be the adult female
of the
Cork Harbour
pod.
It
was
towed
into Crosshaven
where scientists carried
out
a
post-mortem.
The
remaining
two
whales
were
last
seen
in the harbour
on
24
July
hunting
near
Whitegate.
Over the
following
two
months
they
were seen on
a
number
of occasions within 3km
of
Roches Point.
During
the six weeks of their
stay
in
the harbour
we
made
over
75
hours of
observation
on
their behaviour.
These
observations
are
reported
here.
There
are
several records of killer
whales Orcinus
orca
entering
estuaries
in
Ireland since
the
18th
century.
In
1962
four
female
killer
whales
travelled
into
Portaferry,
Co
Down
(Fairley
1981).
In
August
1974
a
male and
two
females
came
into
Cork
harbour for the first
time
recorded
and
left the
same
day
(Jim
Wilson
pers.
comm.).
In
1977
a
single
male
killer whale
entered
Lough Foyle
for
a
week
(Wilson
and Pitcher
1979).
Killer whales
are
most
frequently
sighted
in
the south of
Ireland
from June
to
September
(IWDG
Cetacean
Sighting
Review
1991-2001).
Methods
Most of
our
observations
were
carried
out from
high
ground
on
the
shore
at
Cobh,
Whitegate
and
Whitepoint,
using
binoculars
and
a
telescope.
We
also
observed them
on
several
occasions
from
a
boat,
following
recommendations for
watching
cetacea from boats
issued
by
the
Irish
Whale and
Dolphin Group.
Diving
times
(from
the
moment
of total
submergence
to
the
resurfacing
of the
tip
of the
dorsal
fin)
were
recorded
using
a
digital
stopwatch.
Photographs
and
extensive
video
footage
were
also taken
and
examined.
187

Ir.
Nat
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Volume 27
No 5
2003
Results
Diving
The
diving
patterns
of the
adult
male
and
adult
female
were
recorded.
Each
whale
was
timed
on
separate
occasions. The
differences between
dives
when
apparently
feeding
and
when
travelling
are
distinctive.
The
travelling
male dived
in
a
pattern
of
sequential
long
(approximately
six
minutes),
medium
(approximately
one
minute)
and short
dives
(approximately
30
seconds).
When
they appeared
to
be
feeding they
used
a
series
of
short
dives,
each
lasting
roughly
ten seconds.
On
a
few
occasions
we
observed
the
male
banking
at
about
45?
as
he
submerged.
This
was
most
noticeable due to
the
size of
it's dorsal fin.
The
young
male
was
recorded
twice
doing
almost
vertical dives
exposing
the
whole tail
fluke.
Cooperative
Hunting
On at
least five
occasions,
the
whales
were
observed
flicking
fish into
the
air
with their
tail
and
the fish
then
being caught by
them
or
another member of
the
pod
on
hitting
the
water.
The
immature male
was seen
flicking
a
salmon Salmo
salar
with
his tail
1.5m into the air.
The adult
male rushed
to
where
the salmon hit the
water
and
caught
it. On
one
occasion both
the
adult male and
the immature
male
were
observed
attempting
to
tail
flick fish
simultaneously
with
the tails of both
animals
visible
above
the
surface
on
video
footage.
On
a
number
of occasions
the
adult
male and
young
male
were
seen
swimming
parallel
to
each
other
on
the surface
about
300m
apart.
As
the
whales
would swim
at
a
high
speed
for
between 100
and
200m
the
gap
between
the
two
whales would
gradually
narrow
until
they
were
within 30m
of each
other.
We believe
this
was
cooperative
hunting
because
at this
point,
they
entered
the
same
behavioural
pattern
as
when
feeding.
We
believe that
during
this movement
the
whales
were
herding
fish into
a
tighter
shoal
to
make
an
easier
catch.
Feeding
The
diving
patterns
during
what
we
believe
is
feeding
behaviour
are
substantially
shorter
than
when
travelling.
It
was
quite
easy
to
identify
what
we
considered
to
be
feeding
behaviour. The
whales would rush
along
the
surface and
disturb the
water around
them.
They
become
more
active
on
the surface and
expose
more
of
their
body.
On
a
number
of
occasions
we
observed individual
whales
circling.
We believe
they
did this
to
herd fish into
tight
shoals. We observed
this
in
detail
on one
occasion.
Similar behaviour has been
observed
amongst
killer
whales
in
Norwegian fjords
(Weir 2002).
The
scene
was
recorded
on
video
camera
and
studied later. It
was
followed
by
a
brief
period
of
tail
flicking
and
rushing
on
the
surface.
The
circles
were
roughly
35m in
diameter. The adult male surfaced
four
times
and took 47
seconds to
complete
one
circle.
During
feeding
the whales sometimes 'rocked'
on
the
surface.
We believe
this
was
when the
whale
was
chewing.
The dorsal
fin
was
above the
surface and
the
body
rocked
from
the head
to
the lower back
area.
We
witnessed all
three
animals
188

Ir.
Nat
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Volume 27
No
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2003
doing
this
during
and
after
feeding.
This
rocking
lasts for
periods
of
about
10
seconds.
Once
the
immature
male
was
observed
resting
on
the surface
with
a
salmon
hanging
out
of
his
mouth for
about 3 seconds
before it dived
slowly.
Fish
known to
be
present
in
the harbour at
the
time
included:
salmon
Salmo
salar
L,
thick-lipped
mullet Chelon
labrosus
(Risso),
sand eel
Hyperoplus
lanceolatus
(Lesauvage),
mackerel
Scomber
scombrus
L,
bass
Dicentrarchus labrax
(L),
cod
Gadus
morhua
L.
and
pollack
Pollachius
pollachius (L).
Inquisitive
Behaviour
On
a
few occasions
the adult male
and
the
immature
male
clearly
changed
direction
and
approached
boats. On
7
July
the adult
male
approached
and
surfaced
less than 2m
from
a
drifting
boat. On
19
July
a
dog
swimming
out
after
a
ball
clearly
caused the male to
alter
course
and
turn
towards
it,
approaching
within
15m of
the
shore.
Spy
Hopping
Spy
hopping
is
a
term
to
describe
a
whale
raising
its head
vertically
out
of the
water.
Four
spy
hops
were
recorded
during
their
stay,
all of
which
happened
around
dusk.
Once,
two
thirds of
the male's
body
was
clear
of the
water.
Three
of
the
spy
hops
were
observed
in
quick
succession
on
one
evening
at
22.45h. On
that
occasion the male
rotated
45?
after each
spy
hop.
Breaching
Only
one
full
breach
was
recorded
during
the
visit. It
was
by
the
adult male.
Tail
Slapping
The
killer whales
were
frequently
observed
'tail-slapping'
during
which
they
brought
their
whole tail
out
of the
water
and
slapped
it
down
on
the of
the
water.
We
believe this
was
to
stun
fish,
making
them
easier
to catch
as
it
happened
during
what
we
believed
were
normal
feeding
patterns
though
it is
generally
unknown
as
to
why
this is done. Other
possible explanations
were
that
it
might
have
been
a
way
of
signalling
under
water,
courtship display,
a
show
of
strength,
for
dislodging parasites
or
possibly
just
a
form of
playing
(Carwardine
2001).
The
immature
male
was
once
seen
tail
slapping
while
upside
down.
Resting
The whales
were
observed
resting
motionless
on
the
surface for
periods
of
up
to
30 seconds. This
resting
was
commonly
seen
after
feeding
and
was
mainly
observed in the
immature
male.
On
one
occasion the
immature male
was
floating
motionless
and
was
approached
very
slowly
by
the
adult male
who seemed
to
189

Ir. Nat.
J.
Volume
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No
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2003
Cork
City-^=_>r
V>
CorkHarbour
Passage
West)
^
((_^
j
I
Cobh^~~^
N
-^^s^o ?<^~^
* *
/
Vv-J
Whitegate
Crosshaven7/
i?^S^^S^X
/
SO
3Km
f
6
v-/
1
t
^^
Figure
1.
Movements
of the killer whales
in
Cork
Harbour,
June-July
2001.
Key:
1:
Roches
Point,
where
the
whales
were seen
first
on
5
June.
2:
Buoy
13,
on
the
main
shipping
channel. The whales
spent
the
majority
of
their
time
here.
3: "The
Holy
Ground",
the
best
place
to observe
the
whales
especially
on
the
full tide. 4:
Marino
Point,
River
Lee,
the whales
were
chased
persistently
around the
harbour
and
up
into the river
Lee
by pleasure
boats
on
the
night
of
12
June. 5:
The
whales
swam
up
to
Cork
City
center
and
remained
there for
the
night
of
15-16 June.
6:
The
mouth
of
Cork
Harbour,
fishermen
found the dead
body
of
the
adult female
on
8
July.
7:
Crosshaven,
the
post
mortem of the female took
place
on
the
slipway
on
8
July.
nudge
it after which
the immature male dived
slowly.
Similar behaviour
was
observed between the
female and the immature
male.
Group
Behaviour
The adult
male would often float
on
the surface for
up
to
10 seconds
at
which
time either
or
both
of the other
two
whales would surface
alongside
at
which
point
the
male
would
move
forward with them
and dive.
They
often
synchronized
surfacing
and
diving.
We
also saw
them
hunting together regularly
as
described
in
the
section
on
feeding.
While the female
was
alive,
when
travelling together
the
immature male
was
almost
always
at
her
side with the
adult male
rarely
seen
between
the
two.
190

Ir
Nat. J. Volume
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No
5
2003
Movements
within
the Harbour
After
spending
five
days
at
the
mouth of Cork
Harbour,
the
killer
whales
entered
the
Harbour
and followed
the
shipping
channel
past
Cobh
Town and
beyond
Haulbowline
Island.
They
travelled
east
to
French's
Bay,
which
proved
to
be the
place
where
they
were
most
frequently
observed
and
where
they
spent
their
first
night.
Over the
next
two
days
pleasure
boats
up
the
River Lee
persistently
followed
the whales
extremely
closely.
The whales
stayed
near
Marino
Point
for
five
days.
The
pod
travelled
upriver
as
far
as
City
Hall
in Cork
City
from
the
15
to
16
June.
On
this occasion
the whales
travelled
4.5km
in 27
minutes,
this
means
they
were
travelling
at
an
average
speed
of
10km
per
hour.
Discussion
This
was
the
longest
recorded
stay
of killer
whales
in
Irish
waters. The
last
time
a
killer
whale
was
seen in
an
Irish river
was
in 1977
in
Lough
Foyle (Wilson
and
Pitcher
1979).
The
only
other
confirmed
sighting
of
a killer whale
in
Cork
Harbour
was
in
August
1974,
when
a
bull
and
two
females
went
nearly
unnoticed
into
the
inner-harbour.
To
the
best
of
our
knowledge
ours
is the first
detailed
study
of
killer
whales
in
Ireland. Weir
(2001)
reports sighting
of
killer
whales
from around
the
Irish
coasts but
acknowledges
that
nothing
is
known about
the
movements
of
the
animals.
It is clear
from this
reported
visit
that
they
did
not
disrupt
harbour
shipping
as
long
as
they
were
not
provoked.
The
local
authorities,
Duchas,
the Gardal
and
the
Naval
Service,
also
put
much
effort
into
the
well
being
of
the
animals
by
keeping
pleasure
boats
at
bay.
Their
two-month
stay
also
proves
that
they
are
well
capable
of
staying
in
an
enclosed
estuary
without
getting
stranded.
Acknowledgements
The
authors
would
like
to
thank:
Padraig
Whooley,
Jim
and
Ann
Wilson,
Pat
Smiddy,
Michael
McCarthy,
Richie
Ryan,
John
Ryan,
John
Crone,
Felix
Meehan,
Jeff
Higgins,
Ross
Frenett,
Snowy
and
everyone
else
who
helped
us
with this
paper.
References
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D., WHOOLEY,
P
&
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S.
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review
(1991-2001).
Irish
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M
(2001)
Killer
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Irish
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R
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