Content uploaded by Shinji Yabuta
Author content
All content in this area was uploaded by Shinji Yabuta on Jun 03, 2016
Content may be subject to copyright.
doi 10.5358/hsj.30.155Current Herpetology 30(2): 155–158, December 2011
© 2011 by The Herpetological Society of Japan
Function of Body Coloration in Green Anoles (Anolis
carolinensis) at the Beginning of the Breeding Season:
Advertisement Signaling and Thermoregulation
SHINJI YA B U TA 1* AND AKIKO SUZUKI-WATANABE2
1Department of Animal Science, Teikyo University of Science & Technology, Uenohara,
Yamanashi 409–0193, JAPAN
2Department of Biological Science, Nara Women’s University, Kitauoyahigashi-machi,
Nara 630–8506, JAPAN
Abstract: We examined two hypotheses regarding the function of body colora-
tion in green anoles Anolis carolinensis. First, their bright green coloration
serves as a social signal advertising territorial possession or dominance. From
this hypothesis, two predictions derive: 1) most anoles with bright green colora-
tion are adult males; and 2) adult males with bright green coloration tend to
perch at higher positions to send the signal to broad areas. Another hypothesis,
which is not exclusive to the former one, is that the dark coloration functions to
raise their body temperature. From this hypothesis, three predictions derive:
the anoles with dark (brown) coloration are 1) observed more frequently in the
morning than in the daytime, 2) more likely to engage in basking behavior than
in other behaviors, and 3) observed more frequently when air temperature is
low. We tested these predictions in the field at the beginning of their breeding
season. The results supported the advertisement signal hypothesis, but not the
thermoregulation hypothesis. However, since our negative results against the
latter may actually be attributable to relatively low air temperature throughout
our observation period, additional observations are desired to verify rejection
of the thermoregulation hypothesis as resulting from the present study.
Key words: Advertisement signals; Anolis carolinensis; Behavior; Color change;
Thermoregulation
INTRODUCTION
The green anole, Anolis carolinensis, is
known to change its body coloration from
bright green to dark brown, but why does such
a change occur? There are several putative
functions in the lizard’s changing body colora-
tion, such as predation avoidance by making
itself more cryptic, advertisement by demon-
strating its presence to conspecific individuals,
and advantage in thermoregulation. However,
recent relevant studies yielded no evidence that
in A. carolinensis body color changes so as to
match the substrate coloration for crypsis
(Jenssen et al., 1995). Thus, we have tested
two other hypotheses related to functions of
the phenomenon, advertisement signal and
thermoregulation, on the basis of predictions
deriving from them as below.
* Corresponding author. Tel: +81–554–63–4411;
Fax: +81–0554–63–4431;
E-mail address: shinji@ntu.ac.jp
156 Current Herpetol. 30(2) 2011
HYPOTHESES TESTED
Advertisement signal hypothesis
Many animals use visual and auditory signals
to advertise territorial possession. Conspicuous-
ness is significant for such signals. For example,
experimental changes in conspicuousness of
color signals in birds lead to change in territory
size: males with increased conspicuousness
obtain larger territories than those with reduced
conspicuousness and controls (Marchetti, 1993).
Dominant males of the anole defend territories
during the breeding season (Greenberge and
Noble, 1944). For these individuals, the brilliant
green coloration may advertise dominance,
being advantageous in defending and maintain-
ing the territory (advertisement signal hypoth-
esis). If this is the case, two predictions would
be possible. First, most anoles with bright
green coloration should be adult males. Sec-
ondly, bright green males should perch portions
of trees and other objects in their territories
where they can broadcast the signal effectively:
in a higher position that is visible from a broader
area. Actually, in laboratory experiments in
which two males were encountered to determine
the dominant-subdominant relationship, a
dominant male wore brighter green body col-
oration and attained a higher place (Korzan et
al., 2002; Plavicki et al., 2004).
Thermoregulation hypothesis
Reflectance strongly affects the warming
rate of animals exposed to insolation. For this
reason, body coloration might affect heating
rates in lizards during basking (Cooper and
Greenberg, 1992). Green anoles may there-
fore change their body coloration to regulate
body temperature. If this is the case, they
should choose darker (brownish) coloration
when they seek to raise their body tempera-
ture. Three predictions derive from this infer-
ence. First, more anoles would be brownish in
the morning (i.e. before being active) than in
the daytime. Secondly, the lower the air
temperature, the more anoles would be brown-
ish. Finally, anoles would be brownish at higher
frequency in basking than in other behaviors.
MATERIALS AND METHODS
Green anoles have been introduced to
Chichi-jima island (27°N, 142°E) around 1965
(Hasegawa et al., 1988). The breeding season
of anoles on this island ranges from March–
September (Suzuki, 1996). Observations were
carried out between 14 and 19 March 2000
when the breeding season had just started (see
above). We set a route to walk and observe
anoles in the morning (0750–0830 h) and
daytime (early in the afternoon, 1310–1430 h)
everyday. We recorded the body coloration,
approximate body size, behavior, and approxi-
mate height from the ground and substrate col-
oration of perching position for each individual
encountered. The height was estimated to
nearest 10 cm. Substrate coloration was identi-
fied to one of the following six categories: dark
brown, brown, gray, beige, green, and dark
green. Air temperatures were measured at 1 m
height in shade before each observation.
Body coloration was visually assigned to one
of the four classes of brightness: bright green,
green, brown, and dark brown. Body size was
also visually categorized into three classes: large
(snout-vent length [SVL] >180 mm), medium
(120–180 mm), and small (<120 mm). The
large anoles were adult males because they
always had well-developed jaws and dewlaps.
Behaviors in which anoles engaged were
classified into four categories: basking (stayin-
ing motionless in the sun), resting (staying
motionless in the shade), patrolling (moving
around), and displaying.
RESULTS
We made a total of 169 individual observa-
tions. Obviously the anoles’ body coloration
did not match the substrate coloration: in only
17 of these 169 observations their body color-
ation matched the substrate coloration.
Large, medium, and small anoles took bright
green coloration in 29 of 80, one of 54, and six
of 35 observations, respectively. The ratio of
the number of anoles that adopted bright
green coloration was significantly larger in
YABUTA & SUZUKI-WATANABE—BODY COLORATION IN GREEN ANOLE 157
large anoles than in medium (chi-squared test,
χ2=21.95, df=1, P<0.001) and small (chi-
squared test, χ2=9.40, df=1, P<0.005) anoles.
In approximately half cases (85/169), anoles
took dark coloration (brown and dark brown).
The ratio of the number of individuals that
adopted brown coloration was higher in the
morning than in the daytime, but that for dark
brown showed the opposite pattern (Table 1).
Collectively, anoles showed no tendency to
take dark coloration more frequently in the
morning (i.e. before activity) than in the
daytime. In addition, no significant associa-
tion was recognized between the coloration and
behavior (Table 2: chi square test, χ2=4.66,
df=3, P>0.05). Also, there was no tendency
of taking darker coloration when air tempera-
ture was low (Fig. 1).
In anoles of the large body class, the
frequency of individuals adopting each colora-
tion did not differ between the morning and
daytime observations (chi-squared test, χ2=
0.59, df=3, P>0.05). In addition, this fre-
quency did not change between individuals
engaging in basking and the other behaviors
(chi-squared test, χ2=4.66, df=3, P>0.05). In
contrast, anoles of the large body class showed
a significant tendency of taking green colora-
tion at higher perching positions (Fig. 2,
ANOVA, df=1, 78, F=6.73, P=0.011).
DISCUSSION
The results supported the two predictions
from advertisement signal hypothesis. Large
anoles adopted bright green coloration more
frequently than medium-sized and small anoles
TABLE 1. The number of anoles that adopted
each body coloration in the morning and daytime.
Time
Body coloration
Bright green Green Brown Dark brown
Morning 22 26 35 13
Daytime 14 22 14 23
TABLE 2. The number of anoles that adopted
each coloration when engaging in basking or the
other behaviors (resting, patrolling, and displaying).
No significant association was detected between the
coloration and the behavior.
Behavior
Body color
Bright green Green Brown Dark brown
Basking 16 29 26 22
Not Basking 20 19 23 14
FIG. 1. Air temperature and the numerical ratio
of anoles adopting each body coloration. Numeral
above each column equals the sample size for each
air temperature condition.
FIG. 2. The perching height of adult male
anoles observed. These anoles were divided into
four groups based on their body coloration: bright
green (BG), green (G), brown (B), and dark brown
(DB). Upper and lower margins of, and thick hori-
zontal line in each box indicate upper and lower
quartiles, and median, respectively. The upper and
lower lines outside the boxes indicate UQ+1.5·IQD
and LQ-1.5·IQD, respectively, where UQ, LQ, and
IQD represent upper quartile, lower quartile, and
inter-quartile distance, respectively.
158 Current Herpetol. 30(2) 2011
did. Moreover, in the large bodied class (or
among adult males [see above]), the higher the
perching position is, the more frequently an
individual showed bright green coloration.
During the breeding season, adult males need
to advertise their territorial possession or
dominance. A signal by more brilliant body
coloration from a higher perching position
would be more visible from a broader area
than that broadcasted by darker coloration
from a lower position, dissuading other males
from intruding the territory. On the other
hand, it is known that territorial male A.
carolinensis show reduced aggression towards
established territorial neighbors (“dear enemy”
phenomenon) (Qualls and Jaeger, 1991). The
males distinguish familiar and unfamiliar
opponents mainly by vision (Forster et al.,
2005). Advertising in a visually conspicuous
way (wearing brilliant greenish coloration at
higher perch) might help territorial males to
establish and maintain the social relationships
with the neighbors, reducing aggressive inter-
actions with them.
The results did not support the three predic-
tions from thermoregulation hypothesis. How-
ever, this does not necessarily completely negate
the function of body coloration for thermoreg-
ulation. In the present study, approximately
half of the anoles observed were brownish, a
result contrasting to that in the study of Jens-
sen et al. (1995), in which most anoles were
green. In the present study, air temperature,
ranging from 18.3–23.3C, was lower than that
in the study of Jenssen et al. (1995: almost
thoroughly higher than 25C). Therefore,
difference in the pattern of variation in body
coloration between these studies may actually
reflect the difference in range of air tempera-
ture between them, that is, more brownish
when cooler and greenish when hotter.
In conclusion, we suspect that A. carolinensis
takes darker coloration as its base color at the
beginning of the breeding season when it is gen-
erally cooler, and that adult males change their
body coloration to more greenish when they
need to advertise their territorial possession.
This idea needs further verification on the
basis of appropriately designed experiments
and observations.
LITERATURE CITED
COOPER, W. AND GREENBERG, N. 1992. Color and
behavior. p. 298–422. In: C. Gans and D. Crews
(eds.), Biology of Reptilia, Volume 18, Physiology
E: Hormones, Brain, and Behavior. University
of Chicago Press, Chicago.
FORSTER, G. L., WATT, M. J., KORZAN, W. J.,
RENNER, K. J., AND SUMMER, C. H. 2005. Oppo-
nent recognition in male green anoles, Anolis
carolinensis. Animal Behaviour 69: 733–740.
GREENBERG, B. AND NOBLE, G. K. 1944. Social
behavior of the American chameleon (Anolis
carolinensis Vo ig t ) . Physiological Zoology 17:
392–439.
HASEGAWA, M., KUSANO, T., AND MIYASHITA, K.
1988. Range expansion of Anolis c. carolinensis
on Chichi-jima, the Boin Islnds, Japan. Japanese
Journal of Herpetology 12: 115–118.
JENSSEN, T. A., GREENBERG, N., AND HOVDE, K.
A. 1995. Behavioral profile of free-ranging male
lizards, Anolis carolinensis, across breeding and
post-breeding seasons. Herpetological Mono-
graphs 9: 41–62.
KORZAN, W. J., SUMMERS, T. R., AND SUMMERS, C.
H. 2002. Manipulation of visual sympathetic
sign stimulus modifies social status and plasma
catecholamines. General and Comparative Endo-
crinology 128: 153–161.
MARCHETTI, K. 1993. Dark habitats and bright
birds illustrate the role of the environment in
species divergence. Nature 362: 149–152.
PLAVICKI, J., YANG, E., AND WILCZYNSKI, W. 2004.
Dominance status predicts response to nonsocial
forced movement stress in the green anole lizard
(Anolis carolinensis). Physiology and Behavior
80: 547–555.
QUALLS, C. P. AND JAEGER, R. G. 1991. Dear enemy
recognition in Anolis carolinensis. Journal of
Herpetology 25: 361–363.
SUZUKI, A. 1996. Green anole. p. 72. In: S. Sengoku,
T. Hikida, M. Matsui, and K. Nakano (eds.), The
Encyclopaedia of Animals in Japan Volume 5:
Amphibians, Reptiles, Chondrichthyes. Heibon-
sha, Tokyo. (in Japanese)
Accepted: 29 November 2011
