Copeia, 2001(2), pp. 490–498
Taste Discrimination in a Lizard (Anolis carolinensis, Polychrotidae)
KATHRIN F. STANGER-HALL, DEREK A. ZELMER, CHRISTINE BERGREN,
STEPHANIE A. BURNS
AND
The question of whether lizards possess a sense of taste and are able to use it to
discriminate between prey items has been debated in the literature for several decades. This study provides evidence that some lizards indeed do use gustation to
discriminate between prey items. In laboratory choice experiments, the lizard Anolis
carolinensis discriminated between untreated crickets and crickets treated with either
dextrose/aspartame powder (produces sweet sensation in humans) or quinine hydrochloride (QHCl) solution or powder (bitter sensation in humans). Although some
of the lizards showed a strong preference for crickets treated with dextrose/aspartame powder, all lizards generally avoided prey items treated with QHCl. This avoidance is not affected when access to the vomeronasal organ is blocked. During this
study, lizards readily associated taste with color.
EVERAL authors have suggested that taste
buds are uncommon in lizards (e.g. Porter,
1972; Romer and Parsons, 1977; Simon, 1983)
and have, thus, concluded that the chemical
sense of taste may be unimportant to this
group of animals. However, as early as 1915,
Willard had documented taste buds in Anolis
carolinensis. More recently, Schwenk (1985)
provided ample evidence for the presence, if
not abundance, of taste buds in most lizard
species. Schwenk (1985) concluded that the
presence of taste buds clearly indicated the
use of taste in these animals, but he pointed
out that behavioral experiments are needed
to confirm this assertion. Rensch and Eisentraut (1927) conducted one such behavioral
study. They tested the response of heat
stressed lizards [genera Lacerta (Lacertidae)
and Anguis (Anguidae)] to treated drinking
water. Their results suggested that lizards
avoided water treated with ‘‘salty,’’ ‘‘bitter,’’
or ‘‘sour’’ substances but preferred ‘‘sweet’’
solutions. However, Burghardt (1970) pointed
out several problems with their procedures,
including the unsystematic presentation of
the stimuli, inadequate variation in substance
concentration, and lack of control for potential olfactory stimulation. Since that time Curio and Möbius (1978) have reported that no
odor cues are used during prey attack in Anolis lineatopus (Polychrotidae). Gabe and Saint
Girons (1976) reported a low abundance of
olfactory sensory cells in Anolis, and Armstrong et al. (1953) documented poor development of the main olfactory bulb. The main
olfactory bulb is the first relay and processing
station for sensory input from the olfactory
epithelium, and its size appears to be correlated with the sense of smell (e.g., Northcutt,
S
1979; for an overview, see also Schwenk,
1993). This leaves vomerolfaction and gustation as the two main candidates for chemical
substance discrimination in Anolis.
Armstrong et al. (1953) also documented a
reduced size of the accessory olfactory bulb,
the destination of neurons from the vomeronasal organ (VNO). This suggests that the nasal chemical senses as a whole (olfaction plus
vomerolfaction: Cooper and Burghardt, 1990)
are reduced in anoles (Schwenk, 1993). This
conclusion is supported by behavioral evidence as well. Tongue flicking and prey odor
discrimination via the VNO is usually found
in actively foraging lizards (e.g., scincids, varanids, helodermatids, teiids, and lacertids)
but not in sit-and-wait predators such as most
iguanine and agamid lizards (for a review, see
Cooper, 1990). Tongue flicking is rare in A.
carolinensis, and most tongue movements
seem to be used in an agonistic context
(Schwenk and Mayer, 1991) or during exploratory behavior (Greenberg, 1985), suggesting
traces of some vomeronasal function in these
contexts. However, when tongue flicking did
occur, it was not affected by the presence of
different olfactory stimuli (Cooper, 1989).
Based on this evidence, anoles are probably
unable to use their VNO to discriminate between prey items (Cooper, 1989).
The goals of the present study were (1) to test
whether a polychrotid lizard, A. carolinensis,
could discriminate between different chemical
substances that were applied to its food, and (2)
if discrimination was present, to investigate
whether such a discrimination was mediated by
taste receptors or by the vomeronasal organ. In
addition, a morphological analysis was conduct-
q 2001 by the American Society of Ichthyologists and Herpetologists
STANGER-HALL ET AL.—TASTE DISCRIMINATION IN ANOLIS
Fig. 1. Housing conditions. * Paper cups were used
in experiments 2 and 3 but not in experiment 1.
ed to document the morphology and distribution of taste buds in A. carolinensis.
MATERIALS
AND
METHODS
Animals and housing.—Eight male anoles (A. carolinensis) were used for the discrimination experiments. The lizards were obtained as juveniles from a commercial dealer and housed in
captivity for seven months (September to
March) before the start of the experiments. Two
months prior to the beginning of the experiments, all animals were housed individually in
35-liter tanks with screen tops, visually isolated
from each other. Moistened potting soil and
wood chips covered the tank floor. Sixty-watt
Dayglo heat lamps were mounted above the
tanks to provide light and heat for the lizards.
A 12:12h L:D cycle was maintained, and temperature varied between 26 C (night) and 32 C
(day). All lizards were fed with crickets ad libitum, and water was supplied by spraying it on
the back walls of their tanks several times per
day. To train the lizards to retrieve crickets from
containers (as required by the choice experiments), during the two months preceding the
experiment, individual crickets were placed in
two open glass containers in each tank (rather
than being released directly into the tank).
Discrimination experiments.—Each experiment
consisted of a control trial and an experimental
trial. During all trials, two crickets were offered
simultaneously in two small glass bowls (one
inch tall and one inch in diameter). The bowls
were placed on the short side of the tank facing
the observer (approximately equidistant from
the tank walls and from each other; Fig. 1). In
experiment 1, half of the crickets received a yellow color dot (using nontoxic tempera paint)
on their back before being placed in the glass
491
bowl. This marking procedure was done to ensure that the observers could identify the crickets even if they escaped from their glass bowls.
In experiments 2 and 3, each glass bowl was
placed into a slightly larger white paper cup
whose rim was either left white (unpainted) or
was painted with one of three colors: red, blue,
or green. The crickets that were placed in these
individual bowls also received a color dot on
their back that matched the color of the paper
cup rim. In addition to ensuring the identifiability of the crickets, we hoped that the added
color coding of the bowls would facilitate prey
choice in the lizards (see conditioning section
below). Fleishman et al. (1993) documented
the presence of four classes of cones in the retina of five anoline lizards, and Sexton (1964)
demonstrated the use of color patterns in prey
discrimination in A. carolinensis.
To avoid a side bias (left vs right), the two
bowls (different colors) were switched whenever
a choice had been made. As a result, each color
was offered with equal frequency on the right
and left side of the tank.
Before each experimental trial, a control trial
was run to test for preexisting color preferences
in the absence of a chemical substance. The results from these control trials were used to calculate the expected values for a chi-square test.
The experimental trials provided the observed
values (for the experimental design, see Table
1).
Experiment 1 tested whether lizards could
discriminate between untreated crickets (neutral taste) and those treated with quinine hydrochloride (bitter taste in humans). The quinine
hydrochloride (QHCl; Sigma Biological Supply
Company, St. Louis, MO) was applied as 1
mMolar (mM) solution by briefly submerging
the abdomen of the crickets into the solution
immediately before presentation.
Experiment 2 tested whether the lizards
could discriminate between untreated crickets
(neutral taste) and crickets covered in Equalt
powder (dextrose with maltodextrin and aspartame: sweet taste in humans). Equalt was used
to ensure that a possible preference for the
sweet crickets [as indicated by the observations
of Rensch and Eisentraut (1927)] was the result
of chemical discrimination/taste sensation and
not of other side effects associated with an increased caloric intake.
Experiment 3 again tested whether lizards
could discriminate between untreated crickets
and those treated with quinine hydrochloride
(QHCl). However, in this case the QHCl concentration was increased by applying it in powder form (Sigma, St. Louis, MO). In both ex-
Control
(color preference)
Experiment
(‘‘bitter’’: low concentration)
Control
(color preference)
Conditioning (no choice)
Experiment
(‘‘sweet’’)
Control
(color preference)
Conditioning (no choice)
Experiment
(‘‘bitter’’: high concentration)
Trials
Treatment
none
none
none
1 mM QHCl solution
none
none
dextrose/aspartame powder
none
dextrose/aspartame powder
none
none
QHCl powder
none
QHCl powder
Color of bowl
(color of dot)
glass (none)
glass (yellow)
glass (none)
glass (yellow)
white (none)
red (red)
red (red)
white (none)
red (red)
blue (blue)
green (green)
blue or green (b/g)*
blue or green (b/g)**
blue or green (b/g)*
* The color that was most preferred by a given lizard in control trial 3 received the QHCl treatment in experimental trial 3.
** The cricket color that was least preferred by a given lizard in control trial 3 received no treatment in experimental trial 3.
3
2
1
Experiment
TABLE 1. EXPERIMENTAL DESIGN.
neutral
neutral
neutral
‘‘bitter’’
neutral
neutral
‘‘sweet’’
neutral
‘‘sweet’’
neutral
neutral
‘‘bitter’’
neutral
‘‘bitter’’
‘‘Taste’’
Observed 3
Expected 3
Observed 2
Expected 2
Observed 1
Expected 1
chi2 test
492
COPEIA, 2001, NO. 2
STANGER-HALL ET AL.—TASTE DISCRIMINATION IN ANOLIS
TABLE 2. CONDITIONING PHASE (BETWEEN CONTROL
Conditioning for
Experiment 2 (red 5 ‘‘sweet’’)
Animal
ID
1
2
3
4
5
6
7
8
All lizards
tasted
eaten
2
2
6
*
1
2
1
6
20
2
2
6
*
1
2
1
6
20
AND
493
EXPERIMENTAL TRIALS).
Conditioning for
Experiment 3 (blue or green 5 ‘‘bitter’’)
days
tasted
swallowed &
regurgitated
eaten
days
3
3
3
*
3
3
3
3
2
**
**
2
2
2
2
2
12
0
**
**
1
0
0
1
0
2
0
**
**
0
0
0
0
1
1
4
4
4
2
4
1
4
1
* This animal did not taste or eat any red crickets during the control trial and refused to taste any red (‘‘sweet’’) crickets during the conditioning
phase and was, therefore, removed from Experiment 2.
** These animals ate poorly during the control trial and tasted no (ID2) or only one (ID3) QHCl treated cricket during the conditioning phase
and were, therefore, removed from Experiment 3.
periments using powder (2 and 3), the powder
was added to the bottom of the respective feeding bowl, and it was ensured that the cricket was
covered with powder before adding the respective color dot to the cricket.
Conditioning of lizards.—Experiment 1 taught us
that exposure to added taste stimuli (in this case
a 1mM QHCl solution) could lead to a decreased willingness of our study animals to consume further prey items which greatly reduced
the sample sizes in our experimental trial (44
crickets consumed by 6 lizards) compared to
our control trial (67 crickets consumed). The
statistical power to detect potential preferences
in the prey choice of individual lizards was thus
reduced. As a consequence, we attempted to
condition the lizards to associate a certain color
with a certain sensation/taste between control
and experimental trials in the two subsequent
experiments. Our goal was not to show conditioning in lizards per se, but rather to improve
possible discrimination abilities once a taste difference between the two offered crickets had
been detected (if they indeed could discriminate between the two tastes offered in each trial
and associate them with a certain color/lack of
color). Our reasoning was that this approach
could potentially allow the lizards to make a
choice without having to taste the aversive stimulus itself (which would lead to reduced prey
consumption and reduced sample size). For this
purpose, only treated crickets (e.g., red and
sweet) were offered to the individual lizards for
several days between control and experimental
trials. During this conditioning phase each lizard tasted 1–6 sweet (experiment 2) crickets,
and two bitter (experiment 3) crickets, respectively (Table 2). After the animals had tasted the
treated crickets, they were offered a neutral, untreated cricket. Only after they had consumed
this untreated cricket were the experiments
continued with the experimental trials (choice
between colored/treated and neutral or differently colored/untreated cricket). Those lizards
that did not consume any crickets during the
conditioning phase were not used during the
experimental phase of the experiment.
Taste or vomeronasal stimulation?—Because both
taste buds and vomeronasal organs (VNO) can
be tongue-mediated senses that are potentially
stimulated by nonvolatile chemicals (e.g.,
Graves and Halpern, 1989), we needed to rule
out discrimination by vomerolfaction. We eliminated VNO stimulation by sealing the vomeronasal ducts to prevent chemical access to the
VNO in a group of six subjects (ID 1, 2, 3, 4, 5,
8). This experiment was conducted 10 months
after the choice experiments were completed.
It had been shown previously that the duct
sealing procedure successfully prevented VNO
stimulation in the scincid Chalcides ocellatus
(Graves and Halpern, 1989) and in the iguanid
Dipsosaurus dorsalis (Cooper and Alberts, 1991).
Modifying the procedure used by Graves and
Halpern (1989), we kept the lizards in a refrigerator at 10 C for 20 min to establish a coldinduced anesthesia. The subjects were then
held on their backs with their mouth propped
open with a wooden toothpick positioned horizontally across the jaws. A drop of surgical tissue adhesive (Nexaband of Veterinary Products
Laboratories, Phoenix, AZ) was placed over the
openings of the vomeronasal ducts of all six experimental subjects. Drying of the tissue was accelerated by blowing air across the subjects. Af-
494
COPEIA, 2001, NO. 2
ter the adhesive had dried, subjects were returned to their home cages.
To ensure that this procedure did not interfere with the normal feeding behavior of the
subjects, two untreated crickets were offered in
a small glass bowl several hours later and readily
consumed by all six animals. One day later, a
cricket covered in QHCl powder was offered instead, and the behavior of the lizards was observed. Subsequently all lizards were fed untreated crickets.
Morphology.—To investigate the presence and location of taste buds in A. carolinensis, four specimens in poor health were obtained from a
commercial dealer and decapitated with a guillotine for morphological analysis. The entire
head was fixed in Bouin’s fluid, treated with
20% lactic acid for 48h, dehydrated through an
alcohol series (from 70–100% ethanol) and
cleared in cedar wood oil prior to paraffin embedding. The head was serially sectioned (transverse sections) at 8 microns. Sections were
stained with Meyer hematoxylin and eosin and
examined and photographed with a Zeiss binocular microscope.
RESULTS
Fig. 2. Experiment 1: yellow control trial (A) and
experimental trial (B) using 1 mM QHCl solution on
yellow crickets (animals 1 and 8 were not used for this
experiment). Numbers at top of columns are sample
sizes (total number of crickets consumed) per individual from which percentages were calculated. Significant differences in prey choice were found in animals 2, 5, and 6 (*P , 0.05; **P , 0.01; ***P ,
0.005), preferring neutral over bitter crickets.
1 mM quinine hydrochloride (QHCl) solution.—Six
anoles (2–7) were used for this experiment.
Three of these six animals showed a significant
change in prey choice after the yellow crickets
were treated with a 1mM QHCl solution (P ,
0.05, Fig. 2). In all three cases, the lizards
showed an aversive response to the QHCl treated crickets. The other three lizards chose the
bitter crickets between 20% and 40% of the
time.
animals 2, 3, and 7 chose fewer sweet crickets
than would have been expected from the control trial. However, none of these trends was significant (Fig. 3).
Dextrose with maltodextrin and aspartame powder.—
One of the eight anoles (4) had to be excluded
from this experiment because the animal refused to eat any red crickets during the control
trial and conditioning phase. During the conditioning phase, only red crickets (treated with
Equalt powder) were offered to the remaining
seven lizards for three consecutive days. During
this time, each lizard consumed between one
and six red crickets (Table 2). During the experimental trial, two of the seven anoles (6 and
8) clearly preferred the sweet crickets treated
with Equalt powder over the nontreated, neutral crickets (P , 0.005). Lizard 8 was observed
licking the remaining Equalt-powder residue
off the bowl after he had eaten the Equalt-treated cricket. The other five animals showed conflicting trends: animals 1 and 5 chose more and
Quinine hydrochloride (QHCl) powder.—Originally
six anoles (1, 4–8) were included in this experiment. Lizards 2 and 3 were excluded because
they consumed only one cricket every three to
five days during the control trial and the conditioning phase. The animals that remained in
the experiment had each tasted two QHCl-treated crickets during the conditioning phase (Table 2). When first presented with QHCl-treated
crickets during conditioning all six lizards in the
trial showed an aversive response. The first
QHCl-treated cricket was either immediately
spit out (n 5 5) or swallowed and immediately
regurgitated (n 5 1, lizard 7). The second
QHCl-treated cricket also was immediately spit
out (n 5 4), swallowed and regurgitated after 5
min (lizard 5), or eaten (lizard 8).
During the experimental trial, 52 choices
STANGER-HALL ET AL.—TASTE DISCRIMINATION IN ANOLIS
Fig. 3. Experiment 2: red control trial (A) and experimental trial (B) using Equalt powder on red
crickets (animal 4 was excluded from this experiment
because it did not eat any red crickets during the control and conditioning phase). Numbers at top of columns are sample sizes (total number of crickets consumed) per individual from which percentages were
calculated. Animals 6 and 8 showed a significant
change in prey choice (***P , 0.005; ****P , 0.001),
preferring sweet over neutral crickets.
495
Fig. 4. Experiment 3: blue and green control trial
(A) and experimental trial (B) using QHCl powder
on blue or green crickets [QHCl was applied to the
preferred color of the control trial (most eaten); the
less preferred color (least eaten) remained neutral].
Animals 1–3 were excluded from the experiment (see
text). Highly significant differences in prey choice
were found in all remaining animals (4–8), preferring
neutral over bitter crickets (***P , 0.005; ****P ,
0.001). Numbers at top of columns are sample sizes
(total number of crickets consumed) per individual
from which percentages were calculated.
were made between QHCl-treated and neutral
crickets by six animals. In 94% of all choices (n
5 49), neutral crickets were chosen over QHCltreated crickets. However, only one of the three
chosen QHCl-treated crickets was actually eaten
(2% of all crickets eaten; lizard 5), the other two
were immediately spit out. Those latter occasions occured 13 (lizard 4) and 10 (lizard 8)
days after these lizards had last tasted a QHCltreated cricket during the conditioning phase.
For the statistical analysis of the experiment
(Fig. 4), lizard 1 had to be excluded because he
had only consumed two crickets during the experimental trial after tasting the QHCl-treated
crickets during the conditioning phase.
Without exception, the addition of QHCl
powder resulted in a significantly different prey
choice (P , 0.005) in all five remaining lizards.
In all instances, the addition of QHCl resulted
in avoidance of the prey item (Fig. 4).
crickets was so dramatic, we decided to investigate whether this rejection response was maintained, reduced, or abolished when the stimulation of the vomeronasal organ was prevented.
In the first case, the QHCl aversion would have
to be attributed to oral taste receptors; in the
second case a contribution of the VNO to aversion could be postulated; and finally, in the
third case, the QHCl aversion would likely be
exclusively mediated through the VNO. After
access to their VNO was blocked, all six lizards
in this experiment tasted, and immediately spit
out (combined with mouth wiping behavior),
the QHCl-treated crickets offered during this
experiment. When the rejected QHCl-treated
crickets were removed and replaced by untreated crickets, these were readily consumed by all
six animals. In no case was tongue flicking observed prior to the ingestion of a cricket.
Taste or vomeronasal stimulation?—Because the response of the lizards to QHCl powder-treated
Morphology.—Examination of transverse sections
revealed the presence of taste buds, approxi-
496
COPEIA, 2001, NO. 2
Fig. 5. Cross-section of taste buds on the tongue
of Anolis carolinensis.
mately 25 mm in diameter, on the distal surface
of the filiform lingual papillae (Fig. 5). Density
of the taste buds was greatest at the tip of the
tongue and decreased steadily toward the posterior, glandular portion of the tongue. No taste
buds were found lining the trenches between
papillae, but several were observed on the lateral surface of the tongue, as well as on the gingival epithelium of the lower jaw. No taste buds
were found on the roof of the mouth
DISCUSSION
The results of the present study clearly show
that A. carolinensis uses taste to discriminate between chemical stimuli and that the vomeronasal organ plays no role, or a minor one, in prey
ingestion. Furthermore, A. carolinensis showed a
strong aversion to bitter stimuli in the lab, an
aversion that could help prevent the ingestion
of toxic secondary plant compounds accumulating in potential herbivorous prey items. For
example, Sword (1998) has shown that Anolis
lizards rejected grasshoppers (Schistocerca emarginata) raised on a diet of Ptelea trifolia but not
individuals that were raised on a diet of Rubus
trivialis. The rejected grasshoppers tasted bitter
to humans, whereas the accepted grasshoppers
did not (G. Sword, pers. comm.). The results of
the present study strongly suggest that this aversive response is mediated by taste buds found
in abundance especially on the tip of the
tongue where they can facilitate a fast rejection
of the prey item if necessary. A comparison of
experiments 1 (QHCl solution) and 3 (QHCl
powder) furthermore suggests that the frequency of the aversive response (50% vs 100% of lizards) reflects the concentration of the chemical
stimulus. However, the small sample size and
low statistical power for experiment 1 weaken
this conclusion. To corroborate this finding, it
is necessary to conduct a series of experiments
using different stimulus concentrations and a
larger sample size for each individual lizard.
In many cases, when a QHCl powder-treated
prey item was picked up, a lizard spit out the
cricket and repeatedly wiped the sides of its
head on branches. In no case was tongue flicking observed prior to ingestion, underlining the
importance of taste itself and the minimal role
of vomeronasal organ stimulation during prey
choice in A. carolinensis. This conclusion is
strongly supported by our data from lizards with
sealed VNO ducts. All lizards tasted and rejected the QHCl-treated crickets (and subsequently
accepted untreated crickets) even when their
VNO was blocked and, therefore, could not
contribute to chemical discrimination of prey
items.
The strong preference (94%) for untreated
crickets over bitter crickets in experiment 3
clearly indicates that the lizards were able to associate the bitter taste of the QHCl-treated
crickets with a visual stimulus (the respective
color dot or the powder residue) after tasting
only two QHCl-treated crickets during the conditioning phase. This result is consistent with
the findings of Roper and Redston (1987) that
the conspicuousness (through contrasting color) of distasteful prey increased the strength (as
well as the durability) of one-trial avoidance
learning in domestic chicks. However, in lizards,
visual avoidance learning is not as quick and/
or durable: only three animals (1, 6, 7) completely avoided all QHCl-treated crickets during
the experimental trial.
Interestingly, the presentation of sweet crickets caused mixed results. Although five of the
seven tested animals did not exhibit a marked
response to sweet crickets, two lizards clearly
preferred the sweet crickets over the nontreated
crickets, supporting the earlier findings of
Rensch and Eisentraut (1927) with sugar water
in several European lizards. However, it seems
that Rensch and Eisentraut (1927) established
this preference for sugar water by comparing
the drinking behavior of thirsty lizards when offered sugar water, salt water, or water that was
acidic or bitter. In the text passages where the
authors describe lizards drinking sugar water
(Rensch and Eisentraut, 1927:612) and lizards
drinking untreated water (Rensch and Eisentraut, 1927:610), essentially the identical word
choice was used. Therefore, it is likely that the
stated preference of sugar water in that study
might not have been a true preference (when
compared to untreated water, which would have
been the correct control) but only appeared as
a preference in comparison with salty, acidic, or
STANGER-HALL ET AL.—TASTE DISCRIMINATION IN ANOLIS
bitter tasting water. This interpretation is supported by our finding that the majority of lizards in our study (five of seven) did not show a
clear preference for sweet tasting prey. However,
two animals did, and the treatment of crickets
with Equalt (rather than with sugar) in the present experiment ensured that the documented
sweet preference in those two animals was because of taste itself rather than of an association
of red color with an increase in caloric intake.
Anolis carolinensis has been documented to feed
on nectar (Liner, 1996, and references therein),
and a preference for sweet taste could clearly
aid in this behavior.
Willard (1915) found taste buds on the roof
of the mouth of A. carolinensis but not on the
tongue. In contrast, Schwenk (1985) documented taste buds on the tongue and floor of
the mouth (but did not examine the palate).
Our finding of taste buds on the surface of the
tongue and on the epithelium of the lower jaw,
but not on the roof of the mouth, clearly supports Schwenk’s data, and contradicts Willard’s
(1915). It is possible to underestimate the number of taste buds by using sickly or inactive (e.g.,
in torpor) animals that regenerate their taste
buds at a low rate. This, however, would not explain why the reported locations of the detected
taste buds were so contradictory.
In conclusion, A. carolinensis uses gustation to
discriminate between chemical stimuli during
prey capture and not olfaction or vomerolfaction (Cooper, 1989). Lizards generally rejected
QHCl powder-treated (bitter) prey items, and
most (5/7) did not prefer sweet tasting prey.
The avoidance of QHCl powder-treated, visually
marked, crickets was learned after exposure to
only 2 QHCl crickets, suggesting a rapid association of taste and visual stimuli by these lizards. This study clearly supports Schwenk’s
(1985) assertion that the presence, if not abundance, of taste buds in many lizard species may
reflect their use in chemical discrimination. Given the presence of taste buds in most other lizard taxa (Schwenk, 1985), these findings strongly suggest that the sense of taste might play a
more important role in chemical discrimination
in lizards than has been assumed to date by
many researchers. It will be interesting to determine which lizard taxa actually are using their
sense of taste as their primary means of chemical discrimination and how these taxa differ
(e.g., in diet, prey choice, habitat, and phylogenetic relationships) from those taxa that
mainly use olfaction and/or vomerolfaction to
discriminate among chemical stimuli.
497
ACKNOWLEDGMENTS
This study evolved from a class project in Behavioral Ecology taught by KSH at Wake Forest
University (WFU). We thank K. Schwenk for
helpful comments and suggestions in the early
stages of this project. We thank W. Silver for
logistic support and R. M. Brown for his comments on an earlier version of this manuscript.
This study was conducted in accordance with
the animal care guidelines of the Animal Care
and Use Committee (ACUC protocol A96-116)
at WFU.
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