Short Notes Activity Temperatures in Oplurus Cyclurus, Oplurus Cuvieri
Total Page：16
File Type：pdf, Size：1020Kb
Short Notes Activity temperatures in Oplurus cyclurus, Oplurus cuvieri and Zonosaurus laticaudatus and resting metabolic rates in the latter two species Herilala Jean Aimé Rodolph Randriamahazo Laboratoryof Ethology,Department of Zoology,Faculty of Science,Kyoto University, Kitashirakawa-Oiwakecho,Sakyo-ku, Kyoto 606-01, Japan email: [email protected] During activity, lizards usually maintain body temperatures within a relatively narrow range which encompasses their optimal body temperature, in spite of ambient tempera- tures that may fluctuate considerably (Avery, 1982). Huey (1982) defines microhabitat use by the complex interactions between abiotic and biotic factors. Simplifying this com- plexity, an important abiotic factor influencing ectotherm life histories and growth rate is temperature (Sinervo and Adolph, 1989, 1994; Sinervo, 1990). Moreover, microhabi- tat differences between some sympatric lizards reflect differing temperature preferences (Roughgarden et al., 1981; Hertz, 1992; Grover, 1996). In this paper, I report observa- tions on activity temperatures and distribution patterns in three Malagasy diurnal lizards species. Their distribution ranges overlap in Ampijoroa forest (Preston-Mafham, 1991; Glaw and Vences, 1994). Resting metabolic rates were also compared between the two medium-sized species, Zonosaurus laticaudatus (Gerrhosauridae) a ground burrowing lizard, and Oplurus cuvieri (Opluridae), an arboreal species. Oplurus cyclurus, the third species, is a rather small arboreal lizard that appears allotopic but also uses commonly the ground to catch large prey (Brillet, 1982; Meier, 1988). The climate in Ampijoroa is relatively dry, sub-arid with a low and seasonal pre- cipitation (Nicoll and Langrand, 1989). The physiognomy of the vegetation is rather interesting. Even on a very small scale, large trees with wide canopy are abundant in lower altitudes whereas shrub-like irregularly distributed trees constitute the vegetation of higher places with west-facing slope (Razafy, 1987). Time, ambient temperature (Ta), 216 and cloacal temperature (Tb) were recorded for each captured animal in October 1990. Sex of the study subjects is not readily evident and was not taken in consideration. From nine 0. cuvieri and eleven Z. laticaudatus transferred into captivity in Antananarivo's zoological park, oxygen consumption was measured with an Applied Electrochemistry S3A-1 oxygen analyzer in an open flow system as described in Stephenson and Racey (1993). Resting metabolic rate (RMR) was measured between November 1990 and December 1991 on adult individuals at rest during the inactive period (18h00-07h00). Experiment temperatures ranged from 4°C to 38°C. For cold temperatures (4°C to 26°C) experiments were done in winter months. Temperature was kept constant during one mea- surement. At the end of the oxygen consumption measurement, following the removal of the animal from the respirometry chamber, Tb, body weight, duration of experiment and relative appearance were recorded. Four days to one week rest was respected between experiments on any individual. RMR was calculated according to Mc Nab (1978). Stat View J-45 was used to perform statistical analyses. Activity temperatures. For 84 captured lizards, no Tb was recorded when Ta was below 26°C (table 1). At this temperature, observed activity was restricted to tentative basking behavior near shelter. Lizards retreated back to refuge as soon as they perceived any danger approaching. They were captured more or less during the same time of the day. Starting time and end of daily activity were similar for the three species. There was a significant correlation between Ta and Tb in the three species (fig. la, b, c). However, lizards did not follow passively the ambient temperature (r = 0.599, P < 0.0009 for O. cuvieri; r = 0.533, P < 0.0095 for Z. laticaudatus and r = 0.353, P < 0.0315 for O. cyclurus). These three heliophilic sympatric lizard species varied not only in the thermal microhabitats but also in the actual body temperatures [for Ta: F2,82 = 37.373, P < 0.0001, for Tb: F2,82 = 67.169, P < 0.0001]. Activity temperature differences in these lizards and the equal availability of temperature gradient for all species suggest that the observed selective range of temperature is partially attributed to the thermal preference. Despite the fact that the measured parameters Ta and Tb were not enough to determine the microhabitat and thermal preferences, the results allow some general conclusions. Imposed by the changing vegetation type, a horizontal gradient of tempera- tures in the area is discernible. A species would select a microhabitat that favor optimal Table 1. Activitytemperatures of free livinglizards of threespecies: Z. laticaudatus,O. cuvieriand O. cyclurus. Data collectedduring non-reproductiveperiod (Mean f I standarderror). .