NATURAL HISTORY OBSERVATIONS OF THE FLYING LIZARD, DRACO VOLANS SUMATRANUS (AGAMIDAE, SQUAMATA) FROM SARAWAK, MALAYSIA

A field study of Draco volans sumatranus was conducted in Sarawak, Malaysia. Adult females were significantly larger than adult males in snout-vent length (SVL). Clutch size varied, independent of maternal SVL, from one to five. The lizards were strictly arboreal and diurnally active with two peaks of activity before and after noon. There were no differences in perch height between the sexes. The number of males observed was correlated with air temperature. Lack of thermoregulatory behavior and the relationship between body temperature and air temperature suggest that the flying lizard is thermally passive. Home ranges of resident males consisted of one to three adjacent trees, which wholly overlapped with those of one to three females. In most cases, resident males were larger than intruder males both in SVL and dewlap length. The family Agamidae is the Old World counterpart of New World Iguanidae. Lizards in these two families exhibit remarkable similarities in morphological structure, behavior patterns, and ecological exploitation (Stamps, 1977; Avery, 1982), providing excellent material for the comparative study of evolutionary processes. However, compared to iguanids, there have been few ecological and behavioral studies on agamids. Flying lizards of genus Draco Linnaeus, 1758 are arboreal agarnid lizards, consisting of about sixteen species distributed in South India and South-East Asia (Musters, 1983). The most unusual behavioral character of these lizards is their gliding ability. In fact, Draco is the only extant reptile that is a "true" glider (Oliver, 1951; Klingel, 1965). Draco species have a winglike structure formed from a membrane of skin stretched over greatly elongated ribs (Colbert, 1967; John, 1970a). The wings are usually folded along the body unless the lizards are gliding or performing social displays (Hairston, 1957; Alcala, 1967). Males have a large gular appendage, a dewlap, which is used for social displays (Alcala, 1967; John, 1967a). There are several reports concerning the gliding habit of Draco (e.g., Lederer, 1932; Hairston, 1957; Herre, 1958; Klingel, 1965), but little has been reported about their natural history and ecology since Akira Mori and Tsutomu Hikida Department of Zoology, Faculty of Science, Kyoto University, Sakyo, Kyoto, 606-01 Japan Over two visits to Sarawak, Malaysia, we conducted a field study of the flying lizard, D. volans sumatran us Schlegel, 1844. This subspecies is common in the southern part of Sarawak and inhabits relatively open areas. This paper provides basic ecological and behavioral information on activity, thermal biology and spacing pattern of this subspecies. Field work was carried out in a small park (ca. 80 x 130 m) at Red Bridge, Matang (10 35'N, 110° 13'E), 15 km north-west of Kuching, Sarawak, Malaysia. The park was located near a lowland tropical rain forest. Northern and eastern sides of the park were bordered by a small river from the adjacent forest (Fig. 1). About 40 trees (10-25 m high) and several clumps of bamboo (less than 5 m high) were scattered in the park. There were no dominant trees, except the bamboo, in the park: most of them are different species. The floor of the park was covered with cultivated grass, which was mowed periodically. There were few burrows or stones on the ground. Direct sunlight penetrated to almost the entire floor. Observations were made mainly in the southern half of the park during the first survey from 4 to 29 January 1990. The entire area was surveyed during the second period from 15 December 1990 to 8 January 1991. December and January are months of the wet season in Sarawak. The field study utilized three methods: capture-mark-release, census, and direct behavioral observation. During the first two to three days of each survey, as many lizards as possible were captured, measured, marked for individual recognition by toe clipping and color painting, and released at the base of the trees where they were first seen as soon as possible. Lizards were induced to glide and to land at the bases of trees or on the ground, by knocking them down from above with a pliable tip of a long fishing rod. The following data were recorded for each individual: (1) cloacal body temperature (BT) and ambient air temperature in shade 1 m above the ground at the base of the trees (AT) measured by a thermistor (Takara, Digimulti D611); (2) time; (3) weather condition; (4) snout-vent length (SVL); (5) dewlap length (DL) of males measured from the tip of the snout to the posterior tip of dewlap in folded state; (6) sex determined by the presence or absence of a large yellow dewlap characteristic of males; (7) perch tree; (8) perch height (crude estimation to nearest 0.5 m); (9) light condition ofthe perch site (i.e., full sun, filtered sun, or shade) and (10) posture and behavior performed when the lizards were first sighted. Censuses were carried out in bouts while systematically walking through the study site. Each bout lasted 30 to 50 min, and individuals were located by carefully searching each tree by means of binoculars (x 8). A total of 27 censuses (1000 1200 h 10 times, 1200 1400 h eight times, 1400 1700 h nine times) were made in the southern half of the study site during 11 days of the first survey. In the second survey, the entire area was censused on 11 mornings (090