2004

Asiatic Herpetological ResearchVol. 10, pp. 295-297

Anomalous (?) Nocturnal Feeding by the Agamid Lizard Calotes emma in
Northeastern Thailand
WILLIAM H. SCHAEDLA
Department of Biology, Arizona State University, P.O. Box 871501 Tempe, Arizona 85287-1501, U.S.A.
E-mail: schaedla@asu.edu
Abstract. - I observed feeding by the Agamid lizard Calotes emma during the early part of the Thai monsoon season.
During this period, one individual took advantage of swarming termite reproductives and fed nocturnally. Nocturnal
activity has not been reported for this genus. The lizard's behavior may have resulted from conditions created by artificial lighting. Alternately, it may constitute a normal response to a rich annually-available food resource.
Key words. - Calotes emma, feeding, termites, nocturnal, atypical behavior.

Introduction
Agamid lizards belonging to the genus Calotes arewidely distributed throughout South and Southeast Asia.
They are characterized by semi-arboreal or arboreal
behavior, strongly diurnal activity patterns, and insectivorous diets (Erdelen, 1988; Günther, 1864; Subba Rao
1970, 1975; and Subba Rao and Rajabai, 1972).
Calotes emma is a typical member of the genus.
The species occurs from Assam through Yunnan in thenorth, and Peninsular Thailand in the south. It prefers
moist forested habitat and is arboreal to semi-arboreal it
its habits (Günther, 1864). Here I report observations ofC. emma feeding at night in a manner apparently contrary to norms for the genus.

Methods
This study took place at the Sakaerat Environmental
Research Station. Sakaerat is a scientific and educational facility located in Northeastern Thailand at 14° 30.46'
N Latitude by 101° 55.92' E Longitude. The station
grounds cover approximately 80 km2.
Small and medium-sized wildlife is plentiful in thearea. As of this writing, 70 species of mammals, 50
species of birds, and 25 species of amphibians have beenrecorded from Sakaerat. Reptile fauna is also abundant~82 species are known to occur (Lawanyawatna andSchaedla, 2000). Of the reptiles, C. emma is among themost common because of the station's abundant forest
cover.
Seasonal (monsoonal) and perennial dipterocarp
forests comprise the bulk of Sakaerat's habitats. I
worked specifically in an area of Dry Evergreen Forest,
which is a Dipterocarp mosaic containing other floral
components. It is a four storied forest. The upper story
extends from 21 to 40 m in height and consists mostly ofHopea ferrea, H. odorata, Shorea sericeiflora, and© 2004 by Asiatic Herpetological Research

Irvingia malayana. The middle story ranges from 15 to20 m in height and contains Hydrocarpus ilicifolius,
Memocylon ovatum, and Walsura trichostemnon. Thelower story is between 4 and 24 m in height and is characterized by Baccaurea sapida, Apodytes dimidiate, andOlea salicifolia. Undergrowth is less than 4 m from theground, leafy, and composed mainly of Ardisia,Canthium, and Clausena.
Average humidity at Sakaerat runs about 76% overthe course of the year. Average annual precipitation is1,222 millimeters, and average annual temperature is26°C. March is the hottest month with a maximum
recorded high of 37°C. January is the coolest with aminimum recorded low of 8°C. Sakaerat generally
experiences a 3.5 month long rainy season that lasts
from early June through mid September. Conversely,
rainfall is rare from December through February(Tongyai, 1980).
I made behavioral observations of Sakaerat's
Calotes emma on the evenings of 7, 10, and 12 June,
2001. These dates followed the onset of the local monsoon season, but were not monsoon days themselves.
Weather conditions were overcast, but there was noheavy or sustained precipitation. Rainfall was light andintermittent, accompanied by occasional lightning.
Ambient temperature was moderate, ranging from 27° to30°C.
My observations took place from approximately
6:00 PM (dusk) to 9:00 PM. I watched from an area ina semi-secluded part of the research station. My vantage
was the front porch of a bungalow near Sakaerat's station headquarters, but offset in the forest and away fromthe main complex of office, visitor's center, cafeteria,
and general housing. This area is dimly lit by two overhead fluorescent lights attached to the sides of buildings.
These lights attract large numbers of insects, especiallyduring seasonal monsoon periods. In particular, termite
alates (winged reproductives) were present in high num-Vol. 10, p. 296

Asiatic Herpetological Researchbers on the evenings I observed. Large swarms of
Odontotermes sp. and Macrotermes sp. clouded thelocal area and eventually dropped to the ground.
When termites fell to the ground, I observed a single C. emma feeding them. The lizard was present all
three rainless nights, and seemed unperturbed by mypresence. It was there from dusk, or before, to nearly
9:00 PM on all three evenings. It was active, and its
behavior was restricted to the terrestrial environment. It
did not climb nearby trees or the sides of wooden buildings. All of its movements were directed; it displayedno signs of disorientation in the relative darkness of its
surroundings. On the contrary, it focused on the termite
alates and fed vigorously on them as they landed.
On June 10, I captured the lizard to verify its identity as C. emma. It had been correctly identified and wasa mature female. Her stomach was distended from termite consumption, but she was not visibly gravid witheggs.
In addition to the lizard, other predators feeding on
the termite alates included toads (Bufo melanostictus),
geckoes (Cyrtodactylus spp.), and centipedes(Scolopendramorpha).

Discussion
Little is known about the exact feeding preferences of C.
emma. However, some indication of its diet might beinferred from studies of a closely related arboreal
species. Subba Rao (1972) found that C. nemoricola inIndia fed mostly on ants, while Sitana ponticeriana, anunrelated ground-dwelling lizard, fed on termites. In
another study he found that C. nemoricola consumed awide variety of invertebrates ranging from beetles, togastropods, to earthworms. Analysis of gut contents
showed a predominance of ants but no termites. He also
noted a distinct absence of flying insects in the lizards'
stomachs (Subba Rao, 1975). Hence, feeding on winged
termites by C. emma may represent a departure from its
normal dietary habits.
Likewise, nocturnal feeding has not been reported
in the literature surrounding Calotes. In fact, membersof the genus are usually active only during the day(Erdelen, 1988; Günther, 1864; Subba Rao 1970, 1975;
and Subba Rao and Rajabai, 1972). C. emma at Sakaerat
is decidedly diurnal in its habits. At night they tend tosleep on the ends of low-hanging tree branches.
Spotlighting does not wake them and they can be captured easily by anyone walking through the forest with aheadlamp. I have worked at Sakaerat for three years,
and, with the exception of the observations reported
herein, I have never seen them active at night.
Calotes is apparently physiologically predisposed
towards diurnal activity. Light has a positive affect on

2004both the pituitary and the hypothalmamo-neuro secretory systems of C. versicolor (Banerjee, 1972). However,Kar (1987) found that day length (photoperiod) played aless important role than ambient temperature in scale
regeneration by C. versicolor. He speculated this happens because the lizards' thyroid activity is elevated byheat, rather than light.
Evening temperatures were warm on the nights I
made my observations. The lizard I observed may havebeen able to extend her activity because of this. It is also
possible that the lack of sunlight was mitigated by thepresence of overhead florescent lights (albeit dim). Mysubject may simply have been disrupted from its normal
circadian routine by the local environment. Some support for this possibility comes for another observational
study. Subba Rao et al. (1984) noted that abrupt changes
in light intensity, temperature, and relative humidity during a total solar eclipse actually stimulated activity in C.
versicolor.
Of course, the feeding I observed may have beenpart of C. emma's normal behavioral regime. Termite
alates constitute a rich, but seasonally discrete foodsource, induced by the onset of the monsoons. They areavailable in great numbers at specific times of the year,
and they attract a wide variety of predators, including
retiles. It is therefore possible that C. emma takes advantage of the bonanza via seasonal changes in behavior.
Whatever the case, nocturnal feeding by C. emma isunusual and unreported. Even if not anomalous it
deserves future attention.

Literature Cited
Banerjee, S. K. 1973. Effect of light and darkness on thehypothaamo-neurohypophyseal system of the garden lizard, Calotes versicolor. Experientia
29(6):713-714.
Erdelen, W. 1988. Population dynamics and dispersal inthree species of Agamid lizards in Sri lanka: Calotes
calotes, C. versicolor, and C. nigrilabris. Journal of
Herpetology 22(1):42-52.
Günther, A. C. L. 1864. The reptiles of British India.
Robert Hardwick, London.
Kar, A. 1987. Relative importance of temperature andphotoperiod on the physiology of Indian garden
lizard, Calotes versicolor. Current Science56(10):497-499.
Lawantayana K. and W. H. Schaedla. 2000. A Brief
Overview of the Sakaerat Environmental Research
Station in Thailand. Tigerpaper 27(2):29-32.

2004

Asiatic Herpetological Research

Pornprasertchai, K. and D. Disbanjong 1998. Changes inthe forest area at Sakaerat Environmental Research
Station (In Thai). Thai government publication.
Subba Rao, M. V. 1975. Studies on the food and feeding
behaviour of the Agamid garden lizard Calotes versicolor. British Journal of Herpetology 5(4):467470.
Subba Rao, M. V. 1970. Studies on the biology of two
selected lizards of Tirupati. British Journal ofHerpetology 4:151-154.
Subba Rao, M.V. and B. S. Rajabai, 1972. Ecologicalaspects of the Agamid lizards Sitana ponticeriana
and Calotes nemoricola in India. Herpetologica
28:285-289.
Subba Rao, M. V., A Eswar, and K. Kameswara Rao,
1984. Effect of pre, during, and post total solar
eclipse on the activity pattern of an Agamid garden
lizard, Calotes versicolor, Daudin. Journal ofEnvironmental Biology 5(3):197-201.
Tongyai, M. L. P. 1980. The Sakaerat Environmental
Research Station, Its role as a knowledge base forthe determination of forest lands conservation policies for establishing maximum sustained yields onforest resources. Thai government publication.

Vol. 10, p. 297