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Pheromonal Discrimination of Sex by Male and Female Leopard Geckos (Eublepharis macularius)

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Abstract and Figures

The ability of male and female Eublepharis macularius to discriminate among pheromones of males and females and a blank control was investigated. Stimuli were presented on ceramic tiles in the animal''s home cages. Males tongue-flicked at significantly lower rates in response to male stimuli than to female and control stimuli. Males also performed aggressive behaviors toward male, but not female or control, stimuli, and tail vibrations toward female, but not male or control, stimuli. Mean tongue-flick rates by females did not differ significantly among conditions. Discrimination of male pheromones by females was demonstrated by greater performance of labial-licking and chin-rubbing in response to male stimuli than to either female or control stimuli.
Content may be subject to copyright.
Journal
of
Chemical Ecology, Vol.
23, No. 12,
1997
PHEROMONAL
DISCRIMINATION
OF SEX BY
MALE
AND
FEMALE LEOPARD GECKOS
(Eublepharis
macularius)
WILLIAM
E.
COOPER, JR.*
and
LAURA
J.
STEELE
Department
of
Biology
Indiana University-Purdue University Fort
Wayne
Fort Wayne, Indiana 46805-1499
(Received
October
28,
1996; accepted August
14,
1997)
Abstract—The
ability
of
male
and
female Eublepharis macularius
to
discrim-
inate
among pheromones
of
males
and
females
and a
blank control
was
inves-
tigated. Stimuli were presented
on
ceramic tiles
in the
animal’s home
cages.
Males tongue-flicked
at
significantly lower
rates
in
response
to
male stimuli
than
to
female
and
control stimuli. Males also performed aggressive behaviors
toward
male,
but not
female
or
control, stimuli,
and
tail vibrations toward
female,
but not
male
or
control, stimuli. Mean tongue-flick rates
by
females
did
not
differ
significantly among conditions. Discrimination
of
male phero-
mones
by
females
was
demonstrated
by
greater performance
of
labial-licking
and
chin-rubbing
in
response
to
male stimuli than
to
either female
or
control
stimuli.
Key
Words—Pheromone,
tongue-flicking,
sex
recognition, Squamata, Euble-
pharidae, Eublepharis macularius
INTRODUCTION
Pheromonally
based
sex
discrimination
has
been demonstrated
in
several species
of
squamate reptiles (Duvall, 1979; Cooper
and
Vitt, 1984a; Mason, 1992;
Cooper
and
Trauth, 1992; Cooper
et
al., 1994). Male Eumeces laticeps exhibit
differential
tongue-flicking rates
to
male
and
female conspecific pheromones
(Cooper
and
Vitt, 1984a)
and are
able
to
track females
by
following pheromone
trails (Cooper
and
Vitt, 1986a). Male Gerrhosaurus nigrolineatus also tongue-
flick
at
a
higher rate
to
female pheromones than
to
either male pheromones
or
distilled water controls (Cooper
and
Trauth, 1992),
as do
male Blanus cinerus
*To
whom
correspondence
should
be
addressed.
2967
0098-0331/97/1200-2967$12.50/0
©
1997 Plenum Publishing Corporation
(Cooper
et
al., 1994). Fewer studies address
the
ability
of
female lizards
to
discriminate
sex
from
pheromonal cues. Female Eumeces laticeps show
no
dis-
crimination
of sex
based
on
tongue-flick
rate (Cooper
and
Vitt,
1984b), although
they
do
detect conspecific pheromones
of
both sexes. Female
Cordylus
cordylus
tongue-flick
at
higher rates
in
response
to
female,
but not
male, pheromones
than
control stimuli (Cooper
et
al.,
1996).
Evidence
from
several behavioral studies suggests
that
pheromonal cues
are
important
in sex
recognition
in
Eublepharis macularius (Greenberg, 1943;
Brillet, 1990, 1993; Mason
and
Gutzke,
1990).
Following surgical exchange
of
the
tails
of
male
and
female Coleonyx variegatus (close relatives
of
Euble-
pharis), experimental males courted males
with
female tails
and
avoided
the
male tails
of
experimental females (Greenberg,
1943),
leading
to the
conclusion
that some
cue
present
on the
skin relayed information about
the sex of the
individual.
This
was an
important
finding,
but
possible tactile
sex
differences
between tails were
not
ruled
out
(Cooper
and
Trauth, 1992).
Male
E.
macularius react aggressively
to
other males
at any
time
and
court
females
except when they
are
preparing
to
shed their skins. While females
are
shedding, however, males react agonistically
to
them (Mason
and
Gutzke, 1990).
This suggests that
the
separated skin prior
to
shedding acts
as a
barrier, making
female
sex
pheromones unavailable
for
detection (Mason
and
Gutzke, 1990).
Examination
of
chemical constituents
of the
dorsal epidermis
of
male
and
female
leopard geckos
by gas
chromatography revealed distinct
sex
differences
in
lipid
fractions
of
high molecular weight (Mason
and
Gutzke, 1990). Some
of the
lipids that differ between male
and
female
profiles
have been shown
to
serve
as
sex
pheromones
in
Thamnophis sirtalis parietalis (Mason
et
al., 1989).
Male
E.
macularius perform
tail-vibrating
behaviors when courting females
(Brillet, 1991),
but not in
other contexts.
In
empty cages that
had
previously
housed conspecific females, males vibrate their tails, indicating recognition
of
female
pheromones (Brillet,
1990).
Experimental males reacted agonistically
toward anesthetized males,
but
courted anesthetized females (Brillet,
1993).
Males
often
attempted
to
copulate with females, implying that these geckos
are
not
only
able
to
determine
the sex of
conspecifics
in the
absence
of any
behav-
ioral
cues,
but
behave
as
though they were encountering unanesthetized lizards.
Chemical cues
may
have contributed
to sex
recognition
in
Brillet’s (1991) study,
but
were confounded with other cues provided
by the
lizards.
Brillet
(1990)
examined
lingual
responses
and
other behavioral responses
by
males
and
females
to
both male
and
female pheromones.
He
reported that
the
number
of
tongue-flicks
by
males
in
clean cages
did not
differ
significantly
from
those
in
cages
previously occupied
by
males
or
females. Numbers
of
tongue-flicks
by
females
did not
differ
in
clean
cages
and
cages previously
occupied
by
females,
but
Brillet reported that females tongue-flicked
at a
sig-
nificantly
higher rate
in
cages
that
had
been occupied
by
males than
in
clean
2968
COOPER,
AND
STEELE
cages.
However, Brillet (1990) accepted
P =
0.06
as
significant without making
any
downward adjustment
of a to
compensate
for the
number
of
significance
tests conducted.
In
addition,
the
sample sizes were
so
small
(N = 6 in all
cases)
that
statistical power
was too low to
assure detection
of
real
differences.
Here
we
report
further
studies
of the
ability
of
male
and
female
leopard
geckos
to
detect conspecific chemical stimuli derived
from
both sexes
and to
respond
differentially
to
male
and
female stimuli based solely
on
chemical cues
deposited
on a
substrate.
These
abilities were studied experimentally
by
record-
ing
lingual
and
other
behavioral
responses
to
chemical stimuli presented
on
ceramic
tiles.
METHODS
AND
MATERIALS
Subjects
and
Maintenance.
Adult
male
(N = 15) and
female
(N = 28)
leopard
geckos were obtained
from
captive-bred
research
colonies
and
kept
in
an
AALAC-accredited animal care
facility.
They were housed
in
translucent
plastic
containers
(45 x 25 x 30
cm), each having
a
plastic shelter site
and
water
bowl. Water
was
available
ad
libitum,
and
animals were
fed
crickets
two
times
weekly.
Any
crickets
not
immediately eaten were
left
in the
cage. Room
temperature
was
maintained
at
27°C, with
a
12L:
12D
photoperiod.
All
exper-
iments
were performed between 19:00
hr and
24:00
hr
under
red
light
to
minimize
potential disturbance
to
these nocturnal lizards
due to the
investigator’s
presence
and to
observe responses during
the
normal feeding period.
Experimental
Design
and
Analysis. Experiments were conducted
to
deter-
mine
whether
or not
male
and
female
E.
macularius detect conspecific phero-
mones
and
discriminate between pheromones
of
males
and
females presented
on
tiles. Pheromonal stimuli were obtained
by
placing
an
unglazed ceramic tile
(15 x 15 cm) at the
center
of one end of
each animal’s
cage
for a
minimum
of
two
weeks
to
allow thorough marking. Just before
the
beginning
of a
trial,
the
tile,
shelter,
and
water bowl were removed
from
the
cage
of the
animal
to be
tested
and
placed
on the
cage lid.
After
being lightly brushed
to
remove exces-
sive soiling,
an
experimental tile
was
placed
in the
test animal’s home cage
in
the
same position
as the one
removed.
In the
control condition
for responses to
tiles,
the
tile
was a
clean, unmarked tile.
For the
trials requiring marked tiles,
the
tile
was
taken
from
the
cage
of one of the
other individuals
in the
laboratory
population.
In
two
similar experiments testing tongue-flicking
and
other behavioral
responses of
adult males
and
females, male pheromones
or
female pheromones
on
ceramic tiles
and
clean ceramic tiles were presented
to
lizards sequentially
in
randomized blocks designs
in
which each individual
was
tested
in all
three
conditions. Order
of
stimulus presentation
was
completely counterbalanced
for
DISCRIMINATION
OF SEX BY
GECKOS
2969
the
15
males
to
prevent sequential
bias.
In the
experiment
on
female responses,
trial
sequences were completely counterbalanced
for 24
females.
For the
remain-
ing
four
females,
the
sequences were randomized with
the
constraint that
all
three stimuli occurred
at
least once
in the first,
second,
and
third trials.
After
placing
a
tile
in the
animal’s
cage,
the
investigator moved
to a
seat
1 m
away. Tongue-flicks were recorded
for 5
min, beginning with
the first
tongue-flick
directed
to the
tile.
The
occurrence
of
other behaviors
was
recorded
beginning
as
soon
as the
tile
was
placed
in the
cage until
the end of the
trial.
If
the
animal failed
to
tongue-flick
the
tile
in 10
min,
the
tile
was
removed
and
the
animal
was
tested
at a
later date. Animals were tested only once
per
day.
At
the
conclusion
of a
trial,
the
experimental animal’s tile, shelter,
and
water
bowl were replaced
in its
cage.
If the
animal’s tile
was
used
as the
stimulus
in
a
trial with another gecko,
it was
replaced
by a
clean, blank tile that
was
left
to be
marked
for two
weeks
for use in
future
trials. This method allowed tiles
to be
continuously present
in the
cages, except during brief intervals before
the
animals
were tested. Each tile
was
used once, then washed
by
hand with Alconox
and
dried.
In
the
experiment
on
male response
to
pheromones, several behaviors were
recorded:
(1)
tongue-flicking;
(2)
cloacal rubbing—a substrate-marking behavior
in
which
the
animal presses
the
cloacal region
to the
substrate while moving
(Brillet,
1990; Mason
and
Gutzke,
1990);
(3)
stilting—behavior whereby
the
animal
lifts
its
entire body
off the
substrate
by
extending
all
four
legs, arches
its
back,
and
often
waves
and
coils
its
tail (Mason
and
Gutzke,
1990);
(4)
tail
vibration—rapid
vibration
of the
distal
third
to
half
of the
tail performed only
in
response
to
female stimuli while
the
body
and
head
are
held
rigidly
still
(Brillet,
1990);
and (5)
biting—biting
or
attempting
to
bite
the
experimenter
immediately
after
the
trial while
the
experimental tile
was
being retrieved
and
objects were being returned
to the
cage.
Behaviors
recorded
in the
experiment
on
female responses
to
pheromones
were tongue-flicks, labial-licks,
and
chin-rubs. Labial-licks
are
lingual protru-
sions
in
which
the
tongue wipes
the
labial scales about
the
mouth rather than
being directed
to the air or
substrate. Although labial-licks were included
in the
total tongue-flick count, their occurrence
was
recorded because their function
may
differ
from
tongue-flicks directed
to
substrates (DePerno
and
Cooper, 1996).
Chin-rubbing
is
pronounced rubbing
of the
chin
and
throat area along
the
sub-
strate,
in
this case
the
cage
floor or
tile. Only
its
presence
or
absence
was
recorded.
Nonparametric ANOVAs were conducted
due to
significant
heterogeneity
of
variance (Hartley’s
F
max
tests) (Winer,
1962).
Friedman two-way analysis
of
variance
was
used
to
determine whether differences between
the
three conditions
were significant. When main
effects
were significant, multiple comparison pro-
cedures (Zar, 1984) were used
to
determine whether tongue-flick rates
differed
2970
COOPER,
AND
STEELE
between
pairs
of
conditions. Differences
in
frequency
of the
other behaviors
were
analyzed using sign tests
and
binomial
tests
(Siegel, 1956).
All
statistics
were
assessed
at a =
0.05,
and
probability values
are
two-tailed unless other-
wise
stated.
RESULTS
Male
Responses. Mean tongue-flick rates
of
males were highest toward
control stimuli
and
lowest toward male stimuli (Table
1).
Variances
of
numbers
of
tongue-flicks
differed
significantly among conditions
(Fmax
=
12.34;
df
= 3,
14;
P <
0.01).
Mean tongue-flick rates
by
male
E.
macularius
differed
signif-
icantly
among conditions
(x2r
=
12.4;
df
= 2; P <
0.006,
Table
1).
Tongue-
flick
rates were significantly lower
to
male stimuli than
to
both female stimuli
(P
<
0.005)
and
blank control stimuli
(P <
0.025).
Tongue-flick rates elicited
by
female
and
control stimuli
did not
differ
significantly
(P >
0.05).
Only
a few
males stilted,
and
only during trials with male stimuli (Table
1).
In
addition,
a few
males
bit the
investigator when
the
tile
was removed at
the end of the
trial involving male stimuli,
but
none
bit
after
trials
in the
other
conditions (Table
1).
Differences
between male
and
other stimulus conditions
were
not
significant
for
either
of
these behaviors alone
(P =
0.06, stilt;
and P
=
0.125,
bite; one-tailed sign tests). However, aggressive behavior, either stilt-
ing, biting,
or
both,
was
performed
by five
males,
all in
trials involving male-
labeled tiles,
but by no
male
in
other trials. Thus, males were
significantly
more
likely
to
perform
aggressive behaviors
in response to
male stimuli than
to
either
female
or
control stimuli
(P =
0.03; one-tailed sign test). This
difference
is at
best only marginally
significant.
However, assuming that aggression
was
equally
DISCRIMINATION
OF SEX BY
GECKOS2971
TABLE
1.
RESPONSES
BY 15
MALE
Eublepharis macularius
TO
CONSPECIFIC CHEMICALS
AND
CONTROL STIMULI
Tongue-flicks/5
min
Mean
SE
Range
Stilting
(N)
Biting
(N)
Tail-vibrating
(N)
Cloacal-rubbing
(N)
Male
29.6
4.6
5-64
4
3
0
14
Female
57.0
3.7
38-78
0
0
12
10
Control
66.8
12.9
18-194
0
0
0
14
2972
COOPER,
AND
STEELE
likely
in
each
of the
three conditions,
the
binomial probability that
all five
instances
of
aggression occurred
in
male trials rather than
in the
combined other
trials
is <
0.004.
Eighty percent
of
males performed tail vibrations
in
response
to
female
stimuli,
whereas none vibrated their tails
in
response
to
male
or
control stimuli.
Thus,
significantly more males performed tail vibrations
in
response
to
female
stimuli
than
to
either
of the
other
two
stimuli
(P <
0.0003
each, one-tailed sign
tests).
Males rubbed their cloacal regions over
the
tile
and
cage bottom
in
nearly
all
trials.
There were only seven trials
in the
entire experiment
in
which this
rubbing
behavior
did not
occur. Five males
did not rub
during trials with female
stimuli,
and one
each
did not rub in the
male stimulus
and
control conditions.
No
individual
failed
to
perform cloacal rubbing
in
more than
one
trial.
Differ-
ences between pairs
of
conditions were
not
significant
(P >
0.10, sign tests),
but
the
data hint that males
may be
less
likely
to
perform cloacal rubbing
in
response
to
female chemical stimuli than
to
male
or
control stimuli.
Female
Responses. Females tongue-flicked
at
substantial rates
in all
con-
ditions, with slightly higher rates
in
response
to
female stimuli than
to the
other
two
stimuli (Table
2).
Variances
of
female tongue-flick rates
differed
signifi-
cantly
among conditions
(F
max
=
3.98;
df
= 3, 27; P <
0.01).
Mean tongue-
flick
rates
by
female
E.
macularius
did not
differ
significantly among conditions
(X?
=
5.24;
df= 2;
0.05
< P <
0.10, one-tailed).
Twenty-four
of 28
females performed labial-licking (Table
2), but
only
two
individuals
did so in all
three conditions. Thirteen females labial-licked only
in
response
to
male stimuli, three only
to
female stimuli,
and
none only
to
control
stimuli.
Numbers
of
females labial-licking varied
significantly
among condi-
tions: more females labial-licked
in
response
to
male stimuli than
to
either female
stimuli
(sign test,
P <
0.001)
or
controls (sign test,
P «
0.001).
There
was
TABLE
2.
RESPONSES
BY 28
FEMALE
Eublepharis macularius
TO
CONSPECIFIC
CHEMICALS
AND
CONTROL
STIMULI
Tongue-flicks/5
min
Mean
SE
Range
Labial-licking
(N)
Chin-rubbing
(N)
Male
46.4
3.7
23-106
21
10
Female
53.2
7.4
15-211
7
1
Control
39.1
4.4
1-109
7
0
no
significant
difference
in
numbers
of
females labial-licking between
the
female
and
control
conditions
(P >
0.10).
Slightly over
one
third
of
females rubbed their chins
and
throats along
the
tiles
in
response
to
male-labeled tiles.
One
female chin-rubbed
on
both male-
labeled
and
female-labeled tiles,
but
none chin-rubbed
a
control tile (Table
2).
Thus,
significantly
more females chin rubbed
in
response
to
male stimuli
in
each
case
(female:
P =
0.002;
control:
P <
0.001;
sign tests).
DISCUSSION
Male
Responses. Male Eublepharis macularius clearly
detected
and
differ-
entiated between male
and
female stimuli
in
tests using marked tiles. Detection
is
implied
by the
difference
in
tongue-flick rates between
the
male stimulus
and
control conditions. Discrimination
of
male
from
female chemical stimuli
is
indi-
cated
by the
significantly lower tongue-flick rate
in
response
to
male-labeled
than
female-labeled tiles. Detection
and
identification
of
male chemical stimuli
by
male
E.
macularius
is
confirmed
by the
aggressive
responses—stilting and
biting—limited
to the
male stimulus
condition.
Elicitation
of
male
aggressive
behaviors
by
conspecific male pheromones
has
also
been documented
in
Sce-
loporus
occidentalis (Duvall, 1979)
and
Blanus cinerus (Cooper
et
al., 1994).
The
lower tongue-flick rate
to
male stimuli than
to
female
and
control
stimuli
confirms
a report
that male
E.
macularius tongue-flick
at a
lower rate
in
cages previously occupied
by
males than
in
clean cages (Brillet,
1990).
Because tongue-flick rates
are reduced
rather than increased
in
male
E.
macu-
larius
by
contact with conspecific male pheromones, identification must occur
within
the first few
tongue-flicks, with
further
tongue-flicks serving perhaps
for
confirmation
and
reinforcement
of the
original assessment.
In
other lizard
species,
tongue-flick rates
are
elevated
in response to
male
pheromones
(Cooper
and
Vitt,
1986b;
Cooper
and
Trauth, 1992; Cooper
et
al.,
1994; Dussault
and
Krekorian, 1991; Duvall, 1979). Reasons
for the
difference
in
effect
on
tongue-flick rate
by
male pheromones
from
other species
are
obscure.
Although little
is
known about
the
ecology
of
E.
macularius, males
of the related
Coleonyx
variegatus
may
occupy
the
same sites
for
some time (Cooper
et
al.,
1985a,b)
and are
aggressive
to
conspecific males (Greenberg, 1943). Triggering
by
pheromones
of
species-typical aggressive displays
and readiness for
aggres-
sive biting
in the
nocturnal leopard gecko might
be an
evolutionary
response to
the
difficulty
of
detecting intruding males visually. Readiness
for
aggression,
possibly
with improved
detection
of
nonresident
males,
while
in the
elevated
stilting
posture, interferes
with
further tongue-flicking
of the
substrate. Such
stilting
(and presumably vigilance)
often
persisted
for
much
of the
trial
in the
male stimulus condition. Biting
in
response
to
male stimuli also suggests that
DISCRIMINATION
OF SEX BY
GECKOS
2973
males
are
prepared
to respond
aggressively
to a
male whose pheromones have
been detected. Diurnal
species,
readily able
to
detect
other males visually,
are
free
to
continue lingual investigation
of
pheromones.
The
frequent marking
in all
conditions
may
indicate that leopard geckos
mark
novel substrates
in
their home ranges. Although
differences
among con-
ditions
were
not
significant,
the
fact
that
five of the
seven instances
in
which
a
male
did not
perform marking behaviors occurred
in response to
female chemical
stimuli
hints that there
may be a
somewhat stronger tendency
to
overmark pher-
omonal
deposits
of
other
males
and to
mark unmarked surfaces than
to
mark
female
pheromone deposits.
By
marking
the
area,
a
male
may
signal
his
occu-
pancy
status
to
intruders
of
both
sexes,
allowing nonresident males
to
avoid
interaction,
and
nonresident females
to
detect
a
potential mate.
Males discriminated female chemical stimuli
from
male chemical stimuli
and
control stimuli,
but
this
was
demonstrated
by
species-typical sexual behavior
rather than
by
lingual responses. Mean tongue-flicking rates
did not
demonstrate
even detection
of
female pheromones. Identification
of
female pheromones
by
males
is
confirmed
by the
significantly
greater number
of
males that vibrated
their tails
to
female stimuli than
to
other stimuli. These results agree with
Brillet’s (1990)
finding
that males performed tail vibrations almost exclusively
in
cages previously
occupied
by
females,
but did not
tongue-flick
differentially
in
clean cages
and
those previously occupied
by
females.
Performance
of
social
behaviors including stilting, severe biting,
and
tail
vibrations
appropriate only
for
stimuli derived
from
only
one sex
(Mason
and
Gutzke, 1990; Brillet, 1991, 1993) shows that males detect
and respond
differ-
entially
to
male
and
female chemical stimuli even when tongue-flick rates
do
not
differ.
Preliminary investigation
of
conspecifics before performance
of
these
behaviors
is
brief,
often
limited
to
single tongue-flicks, which supports
the
hypothesis based
on the
current data that chemosensory identification
by
males
occurs rapidly. Following identification, performance
of
social behaviors
may
suppress
or reduce
further
tongue-flicking.
Female
Responses. Tongue-flick rates yielded
no
evidence that females
detect conspecific pheromones. Brillet (1990)
found
no
difference
in
tongue-
flick
rates
in response to
female stimuli
and
clean cages,
but he
reported that
females
tongue-flicked
significantly
more
in
cages
previously occupied
by
males
than
in
clean cages. However,
he did not
test
for
differences
among
all
condi-
tions, accepted
P =
0.06
as
significant,
and
conducted many individual com-
parisons without
adjusting
the
level
of
significance. Appropriate procedures
would
reveal
no
significant
difference.
The
significantly greater numbers
of
individuals that labial-licked
and
chin-
rubbed
when
responding to
male stimuli than
to
female
or
control stimuli shows
that
females detected male pheromones. There
was no
indication that females
detected female chemical stimuli.
These
findings
differ
from
those
for
Eumeces
2974
COOPER,
AND
STEELE
laticeps,
in
which females clearly detected female chemical stimuli
but did not
respond
differentially
to
male
and
female chemical stimuli (Cooper
and
Vitt,
1984b).
Differential
labial-licking indicates that females
detected
male pheromones
and
suggests that vomerolfaction
or
gustation
may be
involved. Labial-licking
might
allow
an
individual
to
glean more information
from
a
sampled stimulus
through
redistribution on the
tongue,
resulting in
contact with taste buds
or
enhancing
the
transfer
to the
vomeronasal organs (DePerno
and
Cooper,
1996).
In
addition,
any
molecules that adhere
to the
anterior labial
scales
during tongue-
flicking
might
be
sampled
by
labial-licking. Eublepharis macularius
also
per-
forms
labial-licks
in response to
prey chemicals (DePerno
and
Cooper, 1996),
suggesting that labial-licking
may
function
generally
in the
sampling
of
chem-
icals that carry information
useful
to the
animal.
The
function
of
chin-rubbing
is
uncertain,
but two
possibilities seem worthy
of
investigation.
First,
females
may
deposit
pheromones indicating their pres-
ence
in response to
male pheromones. Chin-rubbing behavior
has
been
found
in
Sauromalus
o.
obesus (Berry, 1974)
and
Sceloporus jarrovi (Simon
et
al.,
1981). Both sexes
of 5. o.
obesus chin-rub
the
substrate,
and
chin-rubbed sites
elicit species-typical behavioral displays when encountered
by
conspecifics. Sec-
ond, because physical manipulation
of
animal chemical deposits
releases
more
substance (Alberts, 1992), chin-rubbing
ma