Living in a Caatinga-Rocky Field Transitional Habitat: Ecological Aspects of the Whiptail Lizard Cnemidophorus Ocellifer (Teiidae) in Northeastern Brazil
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ZOOLOGIA 28 (1): 8–16, February, 2011 doi: 10.1590/S1984-46702011000100002 Living in a caatinga-rocky field transitional habitat: ecological aspects of the whiptail lizard Cnemidophorus ocellifer (Teiidae) in northeastern Brazil Vanderlaine A. Menezes1, 2; Monique Van Sluys1; Angélica F. Fontes1 & Carlos F. D. Rocha1 1 Laboratório de Vertebrados, Departamento de Ecologia, Universidade do Estado do Rio de Janeiro. Rua São Francisco Xavier 524, Maracanã, 20550-013 Rio de Janeiro, RJ, Brazil. 2 Correspondig author. E-mail: [email protected] ABSTRACT. The ecology of the active forager lizard Cnemidophorus ocellifer (Spix, 1825) was studied to analyze food habits, thermal ecology and habitat use, in the Morro do Chapéu municipality (11º29’S, 41º07’W), state of Bahia, Brazil. Lizards (N = 34) were collected with rubber bands or with an air rifle and, for each individual, we recorded cloacal temperature (Tc), air temperature (Ta) (1 cm above the substrate) and substrate temperature (Ts) (to nearest 0.2°C). We registered the microhabitat used by each animal at the moment of first sight and measured its morphological variables (nearest 0.1 mm). In the laboratory, we registered the number of items of each prey category to the taxonomic level of Order, its dimensions and frequencies. Data showed that, numerically, the category most consumed was Isoptera (84.4%). Volumetrically, the diet was composed predominantly by Orthoptera (27.5%) and Isoptera (21.5%). Prey items that occur aggregated in the environment (termites) were important in the diet of C. ocellifer, a characteristic of active foragers. Males and females did not differ in the types of prey consumed. Cnemidophorus ocellifer had a mean Tc in activity of 37.6 + 1.6°C and the relationship between Tc and ambient temperatures (Ts and Ta) was positive and signifi- 2 cant (F2,28 = 4.814; R = 0.256; p < 0.05). Most lizards were first sighted on leaf litter inside shrubs (45.5%) and on leaf litter at shrub edge (42.4%). Cnemidophorus ocellifer had a relatively high mean Tc during activity, with Ts explaining most of the variation in lizard Tc. KEY WORDS. Bahia; Cnemidophorus; diet; microhabitat; thermal ecology. Cnemidophorus Wagler, 1830 (Teiidae) is composed of (VITT 1983a, 1995), Cerrado (ANDERSON & VITT 1990, VITT 1991, active foraging lizard species distributed throughout much of VITT & CARVALHO 1995, MESQUITA & COLLI 2003a,b) and Atlantic cisandean South America (REEDER et al. 2002). These lizards gen- Rainforest (coastal Restinga habitats) (DIAS & ROCHA 2004, 2007) erally occur in open habitats with sandy soil and high tem- biomes. However, no information regarding populations liv- peratures, such as cerrados, Amazonian savannas, caatingas and ing in transitional habitats has yet been published. In this study restingas (SCHALL & RESSEL 1991, MENEZES et al. 2000, DIAS & ROCHA we investigate the diet, thermal ecology and habitat use of a 2007). Like other wide foraging species, these lizards need to population of C. ocellifer at a transitional area between caatinga maintain high body temperatures during activity (ROCHA et al. and “campos rupestres” (rocky fields) habitats in northeastern 2009). Cnemidophorus behaviorally regulate their activity tem- Brazil. perature at 37-40º C (BERGALLO & ROCHA 1993, MAGNUSSON 1993, TEIXEIRA-FILHO et al. 1995, MENEZES et al. 2000, MESQUITA & COLLI MATERIAL AND METHODS 2003a,b) and usually have a diversified diet, although frequently with predominance of insect larvae and termites (PARKER & The study was carried out in an area at about 1000 m PIANKA 1975, PIANKA 1977, 1986, MAGNUSSON et al. 1985, BERGALLO elevation in the Morro do Chapéu municipality (11º29’S, & ROCHA 1994, DIAS & ROCHA 2007, MENEZES et al. 2008, MESQUITA 41º07’W), state of Bahia, northeastern Brazil. The area is at the & COLLI 2003 a,b, TEIXEIRA-FILHO et al. 2003). transition between Caatinga and “campos rupestres” (rocky Cnemidophorus ocellifer (Spix, 1825) is a bisexual species fields – see EITEN 1992) habitats. The vegetation is predomi- and is the most widely distributed species in the ocellifer group, nantly herbaceous and shrubby on rocky and sandy substrates. occurring in the Cerrado of central Brazil, in the Caatinga of The climate of the region is warm and dry. During the study northeastern Brazil, and in restingas along the northeastern period (November-December 2000), mean air temperature was Brazilian coast, from Salvador (Bahia) northwards (VANZOLINI et 29.3°C and relative air humidity was 48.9% (values obtained al. 1980, DIAS & ROCHA 2007). Some aspects of the ecology of C. with a thermohygrometer, measured every hour between 7:00 ocellifer have been described for populations from the Caatinga and 17:00 h, under vegetation in the shade, at a height of 1 m © 2011 Sociedade Brasileira de Zoologia | www.sbzoologia.org.br | All rights reserved. Ecological aspects of the whiptail lizard Cnemidophorus ocellifer in northeastern Brazil 9 above ground). In this area, five other lizard species occur in proportions of prey categories consumed by males and females sympatry with C. ocellifer, the tropidurids Tropidurus hispidus was tested with a Paired t-Test (ZAR 1999). (Spix, 1825), T. erythrocephalus Rodrigues, 1987, T. semitaeniatus For females we recorded the number of vitellogenic fol- (Spix, 1825) and T. cocorobensis Rodrigues, 1987, and the teiid licles in each ovary, the size and color of the largest follicle Ameiva ameiva (Linnaeus, 1758). (yellow follicles were considered vitellogenic), the presence and Lizards were collected from 27 November to 3 December, size of corpora lutea, and the number and size of oviductal 2000, with rubber bands and an air rifle, during their period of eggs. We measured the length and width of each egg and esti- activity. The collected individuals were euthanized with ether, mated its volume using the formula for the elipsoid (DUNHAM fixed in formalin (dilution of 1:9) for 48 hours and stored in 1983). Females were considered reproductive if they had 70% ethanol. The microhabitat where each lizard was first seen vitellogenic ovarian follicles or oviductal eggs. Mean clutch was recorded according to the following categories: a) leaf litter size was estimated by averaging the number of oviductal eggs inside shrubs; b) leaf litter at shrub edges; c) open sand; d) un- and vitellogenic follicles (when eggs were absent). We consid- covered rocks; e) rocks covered by shrubs; and f) leaf litter out- ered the simultaneous occurrence of vitellogenic follicles, ovi- side shrubs. The difference between males and females in the ductal eggs or corpora lutea as an evidence of multiple clutches frequency of microhabitats used was tested using a chi-square per year in the studied population. test (ZAR 1999). For each lizard, we recorded its body tempera- Variations throughout the day in mean body tempera- ture (Tc), together with air (Ta) (1 cm above ground) and sub- tures of lizards in activity and in mean substrate and air tem- strate temperatures (Ts), with a quick-reading Schultheis (near peratures were tested by analysis of variance (ANOVA) (includ- 0.2°C) cloacal thermometer. For each individual (prior to fixa- ing only samples with N у 2) (ZAR 1999). We analyzed the ef- tion), we measured snout-vent length (SVL), head length (HL, fect of environmental temperatures (Ta e Ts) on lizard body tem- measured from posterior margin of tympanum to snout) and perature using a multiple regression analysis (ZAR 1999). The head width (HW, taken at the angle of the jaw) using a Vernier effect of lizard SVL and mass on body temperature was also caliper (to the nearest 0.1 mm), and body mass (to the nearest tested by multiple regression analysis (ZAR 1999) and differ- 0.001g) with an electronic balance. Morphological differences ences in mean body temperature between males and females in SVL between males and females were tested using analyses of were tested by analysis of variance (ZAR 1999). Additionally, variance for one factor (ANOVA). The differences in HL and HW the tails of all individuals were examined for evidence of previ- between sexes were tested by analysis of covariance (ANCOVA), ous autotomy and differences between sexes in the frequency using SVL as covariate (ZAR 1999). To estimate the activity of C. of regenerated tails were tested using the Z-test for proportions ocellifer at the Morro do Chapéu, we performed hourly transects (lizards with broken tails or that lost their tails when captured from 07:00 to 18:00 h during one day, looking for lizards. or handled were ignored). In the laboratory, stomach contents were identified and Results of descriptive statistics are presented throughout arthropods found were categorized to the taxonomic level of the text as mean ±1 standard deviation, except for volume and Order. Unidentified arthropod remains were grouped in a sepa- length mean values of the five largest preys, which are pre- rate category “unidentified parts of arthropods” and used only sented as mean ±1 standard error of mean. in volumetric analyses. Diet composition was estimated based Lizards used for this study were deposited in the herpe- on relative number, volume, and frequency of each prey type in tological collection of the Museu Nacional, Rio de Janeiro, Bra- stomachs. We measured the length and width of each prey with zil (MNRJ 13816-13849). Vernier calipers (to the nearest 0.1 mm) and estimated its vol- All data were tested for homocedasticity of variances and ume (mm3) using the elipsoid formula: 4/3(prey length/2)(prey for normality of distributions before performing statistical width/2)2. The number of items was counted and the mean length analyses. (mm) and mean volume (mm3) of the five largest items were estimated for each lizard and related to lizard morphology (head RESULTS width and head length) by simple regression analyses (ZAR 1999). Due to the wide variation, all these values were log-transformed Cnemidophorus ocellifer at the Morro do Chapéu had a prior to analysis.