Bull Sharks Prefer Relatives: In Fiji they repeatedly meet at the same reef

Rep ese tative
Image
of
bull
sha ks
gathe i g
at
a
co al
eef
a d
displayi g
social
behavio
(AI-ge e ated
image)

Bull
sha ks
have
lo g
bee
viewed
as
solita y
hu te s
that
c oss
paths
mostly
by
cha ce,
but
a
six-yea
study
i
Fiji
suggests
othe wise.
Resea che s
obse ved
adult
bull
sha ks
gathe i g
epeatedly
at
a
si gle
eef
site
a d
fou d
that
i dividuals
showed
a
slight
p efe e ce
fo
spe di g
time
with
thei
ge etic
elatives.
The
patte
was
subtle
athe
tha
domi a t,
si ce
most
sha ks
i
the
g oup
we e
ot
closely
elated
to
begi
with,
a d
sex,
age,
size
a d
familia ity
all
played
a
la ge
ole
i
shapi g
who
associated
with
whom.
Eve
so,
scie tists
say
the
discove y
ma ks
the
fi st
time
ge etic
ki ship
has
bee
show
to
i flue ce
social
behaviou
i
a
adult
populatio
of
la ge
sha ks.

Why
bull
sha ks
we e
lo g
co side ed
solita y
p edato s

La ge
sha ks
have
t aditio ally
bee
see
as
a imals
that
hu t
alo e
a d
i te act
with
othe s
o ly
b iefly.
Testi g
whethe
family
elatio ships
shape
sha k
behaviou
has
bee
especially
difficult
because
bull
sha ks
t avel
widely
as
adults,
juve iles
face
high
mo tality,
a d
close
elatives
a ely
su vive
lo g
e ough
to
e cou te
o e
a othe
agai
o ce
g ow .
Natasha
D.
Ma osi,
lead
autho
of
the
esea ch
a d
a
scie tist
at
the
U ive sity
of
Exete ,
said
ea lie
wo k
by
the
same
team
had
al eady
show
that
bull
sha ks
actively
choose
thei
social
pa t e s
based
o
t aits
like
sex,
age
a d
size,
which
set
the
stage
fo
aski g
whethe
family
ties
added
a othe
laye
to
those
choices.

How
esea che s
t acked
six
yea s
of
sha k
behaviou
i
Fiji

The
team
wo ked
at
Sha k
Reef
Ma i e
Rese ve,
a
site
off
Fiji
whe e
adult
bull
sha ks
gathe
egula ly
du i g
tou ism
dives
that
offe
food.
This
setti g
allowed
esea che s
to
epeatedly
ide tify
i dividual
sha ks
a d
obse ve
thei
behaviou
ove
time.
D awi g
o
473
dives
co ducted
betwee
2018
a d
2023,
the
team
eco ded
mome ts
whe
sha ks
came
withi
o e
body
le gth
of
each
othe ,
alo g
with
mo e
active
behaviou s
such
as
swimmi g
side
by
side,
joi i g
a othe
sha k,
o
movi g
i
a
leade
a d
followe
patte .
These
obse vatio s
we e
used
to
build
a
social
etwo k
showi g
which
sha ks
spe t
time
togethe
a d
how
st o g
each
co ectio
appea ed.

What
DNA
a alysis
evealed
about
sha k
family
ties

To
measu e
ge etic
elated ess,
esea che s
exami ed
thousa ds
of
poi ts
i
the
DNA
whe e
i dividuals
commo ly
diffe ,
c eati g
a
detailed
ge etic
p ofile
fo
129
sha ks.
This
a alysis
ide tified
11
full
sibli g
pai s
a d
46
half-sibli g
pai s
withi
the
g oup,
though
most
pai s
showed
ve y
low
elated ess
ove all,
mea i g
the
adult
gathe i g
was
ot
built
p ima ily
a ou d
family
u its.
Acco di g
to
the
study,
titled

Is
Blood
Thicke
Tha
Wate ?
The
I flue ce
of
Ki
Withi
a
Bull
Sha k
Social
Netwo k
a d
published
i
the
jou al
Ecology
a d
Evolutio ,
sha ks
with
close
ge etic
ties
te ded
to
associate
slightly
mo e
ofte
tha
u elated
i dividuals,
though
the
effect
was
modest
a d
o ly
became
statistically
sig ifica t
u de
ce tai
methods
of
measu i g
elated ess.

Why
elated
male
sha ks
showed
st o ge
social
bo ds

The
clea est
patte
eme ged
whe
esea che s
looked
specifically
at
active
social
i te actio s
athe
tha
simple
p oximity.
Ac oss
a
subset
of
93
sha ks,
ge etic
simila ity
showed
a
small
positive
li k
with
di ected
social
behaviou ,
a d
this
co ectio
appea ed
st o gest
amo g
male
pai s
specifically.
All
th ee
ge etic
methods
used
i
the
a alysis
ag eed
that
mo e
closely
elated
males
i te acted
mo e
tha
less
elated
males,
eve
though
the
sample
of
co fi med
male
sibli g
pai s
was
small.
Resea che s
f om
the
U ive sity
of
Exete ,
i
a
stateme t
ca ied
o
the
i stitutio ‘s
official
esea ch
ews
page,
coi ed
the
te m
ki flue ce
to
desc ibe
how
ki ship
shapes
sha k
social
st uctu e
alo gside
othe
established
facto s
like
sex
a d
body
size.

How
ea ly
life
i
ive s
may
explai
the
family
bo d?

Bull
sha ks
spe d
thei
fi st
yea s
i
ive s
a d
estua ies
befo e
movi g
i to
coastal
wate s
as
adults,
a d
esea che s
believe
this
ea ly
pe iod
may
be
whe e
family
bo ds
fi st
fo m.
Sibli gs
a d
cousi s
a e
mo e
likely
to
ove lap
epeatedly
i
these
co fi ed
f eshwate
habitats,
pote tially
c eati g
familia ity
that
pe sists
o ce
the
sha ks
dispe se
a d
meet
agai
as
adults
at
sites
like
Sha k
Reef.
Scie tists
suspect
sha ks
could
ecog ise
elatives
th ough
smell,
sight
o
thei
elect ical
se si g
ability,
though
the
study
did
ot
di ectly
test
how
ecog itio
happe s,
leavi g
ope
whethe
sha ks
co sciously
ide tify
ki
o
simply
emembe
i dividuals
f om
thei
ea ly
life
stages.
High
mo tality
amo g
juve ile
bull
sha ks,
d ive
la gely
by
illegal
gill
et
fishi g,
may
also
be
limiti g
how
ma y
elated
sha ks
su vive
lo g
e ough
to
eu ite
as
adults,
which
could
mea
the
family
i flue ce
docume ted
he e
is
o ly
a
pa tial
pictu e
of
a
st o ge
u de lyi g
patte .
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