Factors affecting foraging behaviour, as seen in a nocturnal ground lizard, Goniurosaurus kuroiwae kuroiwae

Abstract

In most lizards foraging behaviour is either ‘widely foraging’ or ‘sit and wait’ but in geckos it varies and fluctuates, providing an opportunity to examine potential factors modulating the foraging mode. In an endeavour to identify these, marked individuals of Goniurosaurus kuroiwae kuroiwae (Gekkonomorpha: Eublepharidae) were observed during July to October 1999 on Okinawajima, Japan. The subtropical and nocturnal conditions presumably reduced the number of intervening factors. Statistical analyses, including stepwise regression analysis, attributed relative responsibilities to individual factors. Using reflecting adhesive tape, 66 individuals were individually marked. These yielded 60 observation bouts of 30 min, including 28 individuals observed on more than one night. The foraging behaviour was active, relatively ‘widely foraging’ compared to the ‘sit‐and‐wait’ behaviour of most other geckos, and variable both within and between individuals. Individuals with empty stomachs showed increased activity. Various components of the foraging behaviour and the factors affecting them radically differed between the sexes. The body temperature of females averaged 1°C higher than that of males. Female activity exceeded that of males and increased during July to October, being highest after cessation of oviposition. In both sexes activity correlated negatively with the duration of observation bouts and positively with ambient temperature, receding around midnight. Under a full moon males were more active but fewer females emerged from shelters. The effect of tail regeneration differed sexually. These innovative results dictate caution in the manufacture of foraging behaviour data for comparative purposes.

Present address: H. Takahashi, Department of Biology, Graduate School of Science, Toho University, Miyama, Chiba, Japan

Keywords:

• Foraging mode
• geckos
• lunar phase
• sex
• tail regeneration
• temperature

Acknowledgements

Goniurosaurus kuroiwae kuroiwae is designated as a nature monument by the Okinawan Prefectural Government (OPG), and its handling is strictly regulated by law. This research was carried out under permission from the Division of Culture, OPG. Financially this research was in part supported by grants from the Zoshinkai Fund for Protection of Endangered Animals, and from the Ministry of Education, Science, Sports and Culture, Japan (MESSCJ) (B‐14380277). The Sefa site is a component of The Okinawan Historical Monument, which is now registered as World Heritage of Culture by UNESCO. Our fieldwork therein was carried out under permissions from OPG and the Education Committee of Chinen Village. We thank Isami (Sammy) Ikeuchi for help on some field trips, and Hervé Seligmann for comments on the manuscript. The first author thanks MESSCJ for supporting his stay at the Tropical Biosphere Research Center, University of the Ryukyus, as a visiting professor.

Notes

Present address: H. Takahashi, Department of Biology, Graduate School of Science, Toho University, Miyama, Chiba, Japan