Southern Resident Orcas Observed Grooming Each Other With Seaweed in First Documented Tool-Making by a Marine Mammal

Two
whales
“allokelping”
with
a
small
length
of
kelp
stem
visible
between
them.
Center
for
Whale
Research,
NMFS
NOAA
Permit
27038

Orca
whales
have
been
observed
biting
off
lengths
of

kelp
and
using
the
strands
to
massage
each
other
—
the
first
known
evidence
of

marine
mammals
making

tools.

A
group
of
killer
whales
off
the
coast
of
the
United
States
and
Canada
were
seen
removing
the
ends
of
seaweed
stalks,
putting
them
between
their
bodies
and
rolling
them
for
long
periods,
likely
for
play
and
to
strengthen
social
bonds,
and
possibly
to
remove
parasites
or
dead
skill
cells.

“We
were
amazed
when
we
first
noticed
this
behaviour,”
said

Dr.
Michael
Weiss,
research
director
at
the
Center
for
Whale
Research
(CWR),
in
a
press
release
from
the
University
of
Exeter.

Big
news!
Our
latest
paper,
“Manufacture
and
use
of
allogrooming
tools
by
wild
killer
whales”
has
been
published
in
“Current
Biology”.
This
is
the
first
known
evidence
of
a
marine
mammal
making
tools
out
of
objects
in
their
environment.
Explore
more
here:
www.sciencedirect.com/science/arti…

[image
or
embed]

—
Center
for
Whale
Research
(@whaleresearch.bsky.social)

June
23,
2025
at
1:06
PM

Scientists
spotted
the
unique
behavior
by

southern
resident
killer
whales
of
all
ages
in
Washington
State’s
Salish
Sea
captured
on
drone
footage.

The

study
was
led
by
CWR
in
collaboration
with
researchers
from
the
University
of
Exeter
and
Boston’s
Northeastern
University.

Several
species
of
whales
have
been
known
to
engage
in
“kelping,”
which
involves
moving
seaweed
with
their
bodies,
fins
and
head.

The
new
discovery
—
termed
“allokelping,”
or
kelping
with
another
whale
—
is
unique
since
the
kelp
is
chosen
and
trimmed
to
be
used
as
a
“tool”
in
the
future
and
manipulated
by
a
pair
of
whales
working
together.

“Bull
kelp
stalk
is
firm
but
flexible,
like
a
filled
garden
hose,
with
a
slippery
outer
surface.
I
suspect
these
features
make
it
an
ideal
grooming
tool,”
Weiss
said.
“What
I
find
remarkable
about
this
behaviour
is
just
how
widespread
it
is
in
the
population.
Males
and
females
of
all
life
stages
and
from
all
three
southern
resident
pods
were
seen
using
kelp
in
this
way.
All
evidence
points
to
it
being
an
important
part
of
their
social
lives.”

The
research
team
observed
the
whales
allokelping
on
eight
of
12
days
of
the
study.
Based
on
the
encounters,
they
suspect
the
behavior
could
be
universal
in
the
population.

Whales
most
often
paired
up
to
engage
in
allokelping
with
those
of
similar
age,
and
close
maternal
relatives.

“This
population
of
whales
has
been
formally
studied
for
50
years
–
the
best-studied
orcas
on
the
planet
–
and
yet
major
new
discoveries
can
still
be
made,”
said
Rachel
John,
a
University
of
Exeter
masters
student
of
animal
behavior,
in
the
press
release.
“We
hadn’t
noticed
‘allokelping’
before
because
the
videos
being
collected
from
our
previous
aircraft
weren’t
of
high
enough
quality,
but
the
footage
we’re
getting
now
shows
this
behaviour
in
great
detail.”

Darren
Croft,
executive
director
of
CWR
and
a
professor
of
animal
behavior
at
the
University
of
Exeter,
said
touch
is
known
to
be
important.

“In
primates
–
including
humans
–
touch
moderates
stress
and
helps
to
build
relationships,”
Croft
explained.
“We
know
killer
whales
often
make
contact
with
other
members
of
their
group
–
touching
with
their
bodies
and
fins
–
but
using
kelp
like
this
might
enhance
this
experience.
It
might
also
be
important
for
skin
health.
Whales
and
dolphins
have
a
variety
of
strategies
to
help
them
slough
dead
skin,
and
this
may
be
yet
another
adaptation
for
this
purpose.”

Croft
said
bull
kelp
and
other
types
of
brown
algae
also
have
anti-inflammatory
and
antibacterial
properties
that
could
benefit
the
whales.

“We’re
now
working
on
more
research
to
confirm
these
initial
findings
and
investigate
the
social
and
skin
health
benefits
of
this
behaviour,”
Croft
added.

Other
species
of
killer
whale
have
been
known
to
rub
against
smooth
stone
beaches,
but
the
southern
residents
had
not
been
observed
doing
that.

“The
Canadian
government
protects
beaches
where
northern
resident
killer
whales
beach
rub,
and
–
with
bull
kelp
declining
due
to
warming
water
temperatures
–
similar
protection
might
be
needed
for
the
southern
residents,”
the
press
release
said.

As
of
July
2024,
only
73
southern
resident
orcas
remain
—
a
critically
low
number,
as
the
subspecies
doesn’t
interbreed
with
other
populations
of
killer
whales.

The
southern
resident
orcas
feed
mostly
on

Chinook
salmon,
which
have
declined
drastically
because
of
overfishing,
the
destruction
of
spawning
habitat
—
including

dam
building
—
and

climate
change.
The
whales
have
also
been
adversely
impacted
by
pollution
and

noise
produced
by
humans.

Weiss
said
the
outlook
for
the
whales
is
“very
bleak”
unless
major
changes
happen
fast.

“We’re
not
seeing
the
birth
rate
that’s
required
to
sustain
the
population.
Under
the
status
quo,
all
of
our
projections
indicate
the
population
will
continue
to
decline,”
Weiss
said.
“They
are
struggling
to
find
enough
of
the
large,
fatty
Chinook
salmon
that
they
need
to
survive
and
successfully
rear
their
young.
We
often
think
about

biodiversity
in
terms
of
protecting
the
phenotypic
variation
we
see
in
animal
populations
–
such
as
differences
in
size,
shape,
and
colour.
However,
conserving
cultural
and
behavioural
variation
may
be
just
as
important.
Allokelping
is
yet
another
piece
of
evidence
of
the
southern
residents’
uniqueness.
If
we
lose
them,
we
lose
so
much
more
than
73
individual
animals
or
a
genetic
lineage.
We
lose
a
complex
society
and
a
deep,
unique
set
of
cultural
traditions.”

Croft
said
the
results
highlight
another
potential
threat
to
the
southern
resident
orcas’
survival.

“[T]he
kelp
forests
where
they
select
their
grooming
tools
are
in
decline
due
to

rising
ocean
temperatures
associated
with
global
warming,”
Croft
said.
“Protecting
the
future
of
these
kelp
forests,
where
the
killer
whales
make
their
tools,
may
be
important
in
preserving
this
unique
culture
and
ensuring
the
southern
resident
killer
whale
population
continues
for
generations
to
come.”

The
findings
of
the
study,
“Manufacture
and
use
of
allogrooming
tools
by
wild
killer
whales,”
were
published
in
the
journal

Current
Biology.