= Uracentron) Azureus Werneri (Tropiduridae
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Journal of Herpctology, Vol. 35, No. 3, pp. 395402, 2001 Copyright 2001 Society for the Study of Amphibians and Reptiles Habitat Use and Activity Patterns of the Neotropical Arboreal Lizard Tropidurus ( = Uracentron) azureus werneri (Tropiduridae) NORBERTELLINGER,~ GERHARD SCHLATTE, NICOLE JEROME, AND WALTERHÖDL Drpavtment of Evolutionary Biology, Institute of Zoology, Uniwusity of Vienna, Althanstvasse 14, A-1090 Vienna, Austria ABSTRACT.-We studied habitat use, activity patterns, foraging mode, and prey spectrum of Tropidurus azureus werneri using a tower crane located in an Amazonian lowland rain forest in southern Venezuela. The lizards were strictly arboreal with a preference for the branches and twigs of the canopy. The horizontal distribution of lizards within the 1.4-ha study area was clustered and remained remarkably stable during two consecutive years. The lizards favored high and well-structured crowns with tree holes that served as shelters during the night. Activity was highest at air temperatures above 28°C measured at a height of 21 m. Activity patterns were influenced by cloud Cover and insolation. Tvopidums azureus werneri showed notable agility and tended toward more active foraging patterns than found in other tropidurid lizards. The prey spectrum was dominated by ants. Basic ecological data on reptiles living high in during four years of fieldwork in Ecuador (for the trees of tropical rain forests are sparse, pri- the still disputed synonymization of the tropi- marily because of the difficulties of observing durid genera Plica and Umcentron with Tropidu- reptiles more than a few meters above ground rus, See Frost, 1992; Avila-Pires, 1995; Harvey level and the challenges of conducting studies and Gutberlet, 1998). However, by using canoes within the forest canopy (Reagan, 1995). Prior to access the limbs of trees in a flooded lagoon, to the development of safe canopy-access meth- Vitt and Zani (1996a) were able to make more ods and effective traps for use on trunks and in than 100 observations of T flmiceps during a sin- tree crowns, arboreal lizards were mainly col- gle wet season, and by covering known retreats lected by shooting or by searching logged trees. of lizards with minnow traps, they captured 23 These methods, however, did not yield large lizards within one week (Zani and Vitt, 1995). numbers of individuals, nor did they contribute Basic ecological data of lizards found in the much knowledge about ecology and behavior. canopy are of special interest because this hab- For example, Duellman (1978) collected only itat differs in many ways from the forest interior two individuals of the arboreal iguanid lizard near ground level. The canopy consists of a Tropidurus (Uracentron) flmiceps (Tropiduridae) dense three-dimensional matrix of leaves and small branches and is exposed to full sun and great variability in humidity and high midday Corresponding Author. E-mail: norbert.ellinger@ temperatures. In contrast, the forest interior is univie.ac.at typically darker, cooler, more humid, and rela- N. ELLINGER ET AL. tively Open (Reagan, 1995). The majority of eco- twice. Observation from the tower crane was logical studies on tropidurid lizards deals with done from heights ranging from 3-32 m above species of open formations or of forest interior ground level. Gaps were used to get near (cf. Howland et al., 1990; Vitt, 1993; Vitt et al., ground level. We recorded the position (specific 1996; Cruz, 1998). Detailed studies on arboreal tree, approximate height, perch diameter) of Tropiduridae exist for T. (U.) flaviceps (Vitt and each spotted lizard and noted lizard activity for Zani, 1996a), T. (Plica) umbva (Gasnier et al., each sighting (moving or stationary; when mov- 1994; Vitt et al., 1997), and T. (P.) plica (Vitt, ing: foraging, interacting with other individuals, 1991). Scientific reports of 7: azureus (U azuv- other activities). Cloud coverage was estimated eum) are less extensive. Observations by Cott visually in increments of one-eighth of full sky. (1926), and Greene (1977) and the analysis of Data were recorded on microcassette tapes and four stomach contents (Hoogmoed, 1973) sug- transcribed later. Further data concerning height gested that the prey spectrum of I: azuveus is and taxonomic status of trees with diameter at dominated by ants. Hoogmoed (1973) also pub- breast height (dbh) > 10 cm within the study lished some anecdotal data on the reproduction plot were put to our disposal by J. Wesenberg, of T azureus. Two eggs of I: azuveus zuevneui, a D. Sattler, and S. Kirmse (unpubl. data, see Ac- subspecies distributed in northwestern Ama- knowledgments). For all observations exceeding zonia (Avila-Pires, 1995), were found by Mäg- 5 min (N = 59), lizard activity was quantified defrau (1991) between roots at the base of a tree as the percentage of time spent moving to total at Rio Mavaca. Venezuela. We used a tower observation time. For the analysis of foraging crane located in the Amazonian lowland rain behavior, we excluded observations of basking forest of southern Venezuela to investigate this individuals or of specimens involved in social arboreal lizard and focused on habitat use, spa- activities. tial distribution within the canopy, activity pat- In 1998, branches that were frequently used terns, foraging mode, and type of prey. by lizards or located near to holes in which liz- ards were observed previously, were encircled MATER~ALSAND METHODS with nonpoisonous glue-board traps (Catch- Study Site.-The study site is located near the master Maxcatcho Giant Rat Board). Twenty- junction of the river Orinoco and the blackwater eight traps were exposed on 11 days for 170.5 tributary Surumoni, 15 km west of La Esmer- h, yielding 14 captures, two of which were re- alda, Estado Amazonas, Venezuela (3'10'N captures. The lizards were removed from the 65"401W, 105 m above sea level). The plot lies boards with vegetable oil. Body mass was mea- within a primary lowland rain forest that has sured with a spring balance (0.5 g). Snout-vent not been cleared or selectively logged in historic length (SVL) and tail length (TL) were mea- time and contains mostly terra firme forest. The sured with a ruler tail width (TW), head width height of canopy trees ranges from 20 m to 34 (HW), head height (HH), head length (HL), m. They form an irregularly contoured and pre- body width (BW), body height (BH), and length dominantly closed canopy. The average annual of hind limbs (HLL) with a caliper (see Avila- temperature in the study area is approximately Pires, 1995). Number and position of ectopara- 26"C, usually with slight variations between the sites were recorded. Five individuals were coolest month (25°C) and the warmest month killed immediately after capture. Seven individ- (26.5"C), whereas a daily range of 5-10°C fre- uals were given a unique paint code with nail quently occurs. The relative air humidity resch- polish which allowed individual recognition es almost 100% during the night and decreases from a distance until shedding occurred (usu- to 50-60% above the canopy on sunny days. An- ally 1-2 months) and released next to the site of nual precipitation is near 3000 mm with a capture. Two of them were killed after recap- strong peak from May to July and a lower peak ture. Prior to fixation in isopropyl alcohol (7O0lO) in September and October. The tower crane run- lizards were dissected and sexed, and stomach ning on rails offers access to the canopy within conteiit was analyzed. The fixed specimens an area of 1.4 ha (Anhuf et al., 1999). were deposited in the Colecion Herpetologica Observation and Cqtuve.-Haphazard searches del Museo de Ciencias, Caracas, and in the Mu- for lizards on trunks and in tree crowns were seo Historia Natural La Salle, Caracas. conducted with binoculars in 1997 (55 h on 14 Climatic Data.-We used visual estimations of mornings and 11 afternoons from February to cloud coverage and measurements of air tem- May) and 1998 (142.5 h on 19 mornings and 27 perature and of irradiation (PAR = Photosyn- afternoons from April to July). Operational thetically Active Radiation) for correlations of breaks of the crane resulting from change of activity and weather. Climatic data were taken staff prevented observations between 1200 h by a team of climatologists of the University of and 1300 h. During each observation period, the Mannheim, Germany (Anhuf et al., 1999). Air whole plot was crossed and inspected at least temperature ("C) was measured by a thermo- HABITAT USE AND ACTIVITY OF TROPIDURID LIZARDS 397 TABLE1. Morphometric characters of Tropidurus azuieus zuerneri. Snout-vent length (SVL), tail length (TL), tail width (TW), head length (HL), head width (HW), head height (HH), body width (BW), body height (BH), and hind-limb length (HLL) are in millimeters, body mass in grams. Male Unsexed Male (N = 5) (N = 5) subadult Female Character Mean -t SE Range (N = 1) (N = 1) Mean i SE Range SVL 60.1-76.0 31.0 72.0 63.1 ? 10.73 53.4-80.0 Body mass 5.0-12.0 1.0 8.5 6.7 ? 2.79 4.0-11.4 TL 34.341.6 17.0 36.0 35.9 ? 7.55 28.747.0 TW 8.1-11.7 3.5 9.8 8.5 ? 1.02 6.9-9.7 HL 15.8-19.6 8.9 18.1 14.6 i 3.95 8.2-20.0 HW 9.7-15.5 5.7 12.0 10.2 It 1.51 8.2-12.2 HH 7.2-19.7 4.3 8.3 8.5 i 1.24 7.1-10.4 BW 10.0-17.6 5.8 17.3 12.5 t 2.96 9.4-17.6 BH 6.7-11.0 4.0 12.6 10.7 i 3.04 7.0-14.6 HLL 39.648.1 21.7 37.0 36.6 i 5.61 29.944.4 sensor fixed in the canopy of a tree (21 m indicates nonrandom distribution.