Wasserdrachen / Water Dragons

The escape response of the agamid lizard Lophognathus temporalis in an urban population was examined during the dry season. Two measurements of escape response were made: the distance an observer can approach before the lizard flees (approach distance) and the distance the lizard flees to refuge (flight distance). The relationship between approach distance and flight distance was examined, as was the relationship between air temperature and both approach distance and flight distance. The influence of time of day, the lizard’s perch (in a tree or on the ground), and year (1996 or 1998) on the escape response was determined. Approach distance and flight distance had no relationship with each other. Air temperature had a positive relationship with approach distance, so variations in temperature between the two years might explain variations in approach distance between them. The lizard’s perch had the greatest influence on flight distance. Lizards in trees fled shorter distances, usually to the opposite side of the tree trunk or branch to the observer. Lizards on the ground always fled to the nearest refuge.

BLAMIRES, S.J. & K.A. CHRISTIAN (1999): Seasonal water loss of the lizard Lophognathus temporalis in the wet-dry tropics of northern Australia. - Amphibia-Reptilia 20 (2): 211-215.

CHRISTIAN, K., BEDFORD, G., GREEN, B., GRIFFITHS, A., NEWGRAIN, K. & T. SCHULTZ (1999): Physiological ecology of a tropical dragon, Lophognathus temporalis. – Aust. J. Ecol., 24 (2): 171-181.

Lophognathus temporalis is an arboreal lizard from the wet–dry tropics of Australia. During the wet season the field metabolic rate (FMR) of the lizards was 209 kJ kg21 d21, but during the dry season FMR was only 62 kJ kg21 d21. Similarly, water flux decreased from 73.6 mL kg21 d21 in the wet season to 18.5 mL kg21 d21 in the dry season. Body temperatures (Tb) were significantly lower in the dry season, and operative temperatures, calculated by incorporating microclimatic data with characteristics of the lizards, indicated that the seasonal shift was due to changes in thermoregulatory behaviour rather than limitations of the thermal environment. By combining field measurements of Tb and FMR with laboratory measurements of standard metabolic rate over a range of Tb, we were able to subdivide the FMR into its components and to determine which factors contributed to the seasonal reduction in energy expenditure. During the dry season, lizards used 147 kJ kg21 d21 less energy than during the wet season, and 24% of this decrease was estimated to be due to the passive effects of lower nighttime Tb, 14% was due to the active selection of lower daytime Tb, 27% was due to the physiological shift to lower standard metabolic rates, and 35% was due to reduced activity in the dry season. Although the population size remained relatively constant (107 lizards ha21 during the wet season and 125 lizards ha21 during the dry season), the population structure changed, reflecting the seasonal patterns of recruitment and mortality. The number of lizards active at any one time was much lower in the dry season, reflecting the lower levels of activity in this season. The energy expenditure of the population of L. temporalis was 612 kJ ha21 d21 during the wet season and 113 kJ ha21 d21 during the dry season.

GÜNTHER, A. (1867): Additions to the knowledge of Australian reptiles and fishes. - Ann. Mag. nat. Hist., (3) 20: 45-57.

GÜNTHER, R. & M. KAPISA (2003): Allochtone Populationen der Kragenechse, Chlamydosaurus kingii GRAY, 1825, und des Papua-Wasserdrachens, Lophognathus temporalis (GÜNTHER, 1867), auf der Insel Biak. – Sauria, Berlin, 25 (2): 31-35. (03.085)

Abstract:
Based on captive specimens released in the early 1990s, successfully reproducing populations of the Frilled Lizard, Chlamydosaurus kingii, and of the Papua Water Dragon, Lophognathus temporalis, have established themselves within and near Biak Town and are still present there today. Biak Island is situated in the Pacific Ocean, about 120 km north-west off the north-west coast of New Guinea, at a distance of about 800 km from the northern range limits of both species.

VOGEL, Z. (0000): Die Mini-Saurier. Wasseragamen aus Indien und Australien. – Aquarien Magazin. S. 406-408.

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