Diet and foraging of the endemic lizard Cnemidophorus littoralis (Squamata, Teiidae) in the restinga de Jurubatiba, Macaé, RJ

Dieta e forrageamento do lagarto endêmico Cnemidophorus littoralis (Squamata, Teiidae) da restinga de Jurubatiba, Macaé - RJ

ECOLOGY

Diet and foraging of the endemic lizard Cnemidophorus littoralis (Squamata, Teiidae) in the restinga de Jurubatiba, Macaé, RJ

Dieta e forrageamento do lagarto endêmico Cnemidophorus littoralis (Squamata, Teiidae) da restinga de Jurubatiba, Macaé - RJ

Menezes, V. A.; Amaral, V. C.; Sluys, M. V.; Rocha, C. F. D.

Departamento de Ecologia, Universidade do Estado do Rio de Janeiro, Rua São Francisco Xavier, 524, Maracanã, CEP 20550-011, Rio de Janeiro, RJ, Brazil

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ABSTRACT

We investigated the diet and foraging of the endemic teiid lizard Cnemidophorus littoralis in a restinga habitat in Jurubatiba, Macaé - RJ. The stomach contents were removed, analyzed and identified to the Order level. There was no relationship between C. littoralis morphological variables and number, length or volume of preys. Termites (48.7%) and larvae (35.5%) were the most important prey items which occurred in the examined lizards´ stomachs. The diet did not differ between males and females. Cnemidophorus littoralis is an active forager and predominantly consumes relatively sedentary prey or prey that is aggregated in the environment. We also found an intact and undigested hatchling of the crepuscular/nocturnal gekkonid lizard Hemidactylus mabouia in the stomach of an adult male of C. littoralis, which indicates that C. littoralis is a potential source of mortality for individuals of H. mabouia in the restinga de Jurubatiba.

Keywords:Cnemidophorus littoralis, Teiidae, Squamata, diet, restinga.

RESUMO

Investigou-se a dieta e o forrageamento do lagarto endêmico Cnemidophorus littoralis na restinga de Jurubatiba, Macaé - RJ. Os conteúdos estomacais foram removidos, analisados e identificados no nível de Ordem. Não houve relação entre as variáveis morfológicas de C. littoralis e o número, tamanho e volume das presas. Cupins (48,7%) e larvas (35,5%) foram os itens de presas mais importantes nos estômagos dos lagartos examinados. A dieta não diferiu entre os machos e as fêmeas. Cnemidophorus. littoralis é um lagarto forrageador ativo e consome, predominantemente, presas relativamente sedentárias ou que ocorrem agregadas no ambiente. Foi encontrado também no estômago de um macho adulto de C. littoralis um jovem lagarto gekkonídeo crepuscular/noturno Hemidactylus mabouia intacto e não digerido, o que indica C. littoralis como uma fonte de mortalidade para indivíduos de H. mabouia na restinga de Jurubatiba.

Palavras-chave:Cnemidophorus littoralis, Teiidae, Squamata, dieta, restinga.

Different factors may affect the diet of lizards, including an ontogenetic shift in prey preferences, body size, sex and foraging tactic (Huey & Pianka, 1981; Pianka, 1986; Zaluar & Rocha, 2000). Moreover, the size of feeding structures can influence or at least, limit the type and size of prey that may be ingested. As a result, mouth size may affect diet composition which may result in differences between males and females and/or between the young and adults (Preest, 1994; Teixeira-Filho et al., 2003).

Active foraging lizards tend to consume relatively sedentary prey or prey aggregated in the environment (Huey & Pianka, 1981; Magnusson et al., 1985; Bergallo & Rocha, 1994). Teiid lizards, including the genus Cnemidophorus, are generally considered as typical active foragers (Pianka, 1970; Anderson & Karasov, 1981; Etheridge & Wit, 1993) and in general predominantly consume termites and larvae (Vitt, 1991; Teixeira-Filho et al., 2003).

Cnemidophorus littoralis is a tropical bisexual lizard that is endemic to coastal sand dune habitats ("restingas") in Rio de Janeiro State, Brazil (Rocha et al., 2000). It can be found in the restinga of Barra de Maricá northwards to the restinga of Grussaí in the north of Rio de Janeiro State (about 200 km of coast). Dietary data available for this species stems from the population of the restinga in Barra de Maricá, RJ (Teixeira-Filho et al., 2003).

Cnemidophorus littoralis was recently described (Rocha et al., 2000) and was recently included in the Official Threatened Checklist of Brazilian Fauna (IBAMA/ MMA/Fundação Biodiversitas/Conservation International Brazil, 2003), due to the intense degradation and loss of the habitats of this species.

One factor restricting development and implementation of conservation and managing plans for threatened species is the lack of information on many aspects of the biology/ecology of most of them.

As a result of the Restinga Expedition Project carried out in 1999-2000 along the Brazilian coast by the Departamento de Ecologia of the Universidade do Estado do Rio de Janeiro, a sample of C. littoralis was collected (at that time the species was still not described). We provide additional dietary data about the C. littoralis from the restinga in Jurubatiba, Macaé Municipality, RJ to broaden our understanding of the feeding ecology of this species.

MATERIAL AND METHODS

Study area

The study was carried out in March, 1999 and January, 2000 at the restinga de Jurubatiba (22° 17' S, 41° 41' W), Macaé, Rio de Janeiro State, Brazil. Restingas are coastal sand dune habitats covered by herbaceous and shrubby vegetation (Suguio & Tessler, 1984). The climate of the study area is seasonal with a mean annual temperature of 22.6 °C and a mean annual rainfall of 1,164 mm (Pereira & Araújo, 2000). The most represented plant families in Restinga de Jurubatiba are: Leguminosae, Myrtaceae, Orchidaceae, Bromeliaceae, Rubiaceae and Asteraceae (Pereira & Araújo, 2000).

Data analysis

Lizards (N = 31) were collected with rubber bands and air rifles. Each lizard had its snout-vent length (mm) and jaw width (mm) measured with a Vernier caliper (to the nearest 0.1 mm) and was immediately fixed in 10% formalin. In the laboratory, the contents of the stomach were analyzed and each prey item was identified to Order under a stereomicroscope. All prey were measured for width and length using a Vernier caliper (to the nearest 0.1 mm) and their volume (in mm³) was calculated using the elipsoid formula: 4/3p (length/2) (width/2)² (Vitt, 1991). To estimate the index of relative importance (I_x) of each prey category we calculated their numeric, volumetric and frequency percentages, summed these values and divided by three (Howard et al.,1999). We related the lizard´s jaw width (JW) and snout-vent length (SVL) to the number of prey and to mean length (mm) and volume (mm³) of the five largest prey using regression analyses (Zar, 1999). Because number, length and volume of food items were heavily skewed towards small values, these variables were log transformed prior to analysis so that distributions approached normality. Differences in the mean number and volume of prey consumed between adult males and females were tested by t-test (Zar, 1999).

To estimate the relative movement rate of C. littoralis during activity at the study site, we recorded time (in seconds) moving and time motionless for each lizard using a stopwatch. We observed ten different individuals following each for the maximum observation time of 10 min (totalling 5,493 s of observation).

RESULTS AND DISCUSSION

The mean SVL of lizards collected was 61.0 ± 8.7 mm (range 37.4 – 76.1, N = 31). Adult females measured 60.7 ± 3.7 mm (range 52.0 – 66.0, N = 11), adult males measured 64.4 ± 7.1 mm (range 49.4 – 76.1, N = 17) and juveniles measured 42.3 ± 5.3 mm (range 37.4 – 48.0, N = 3).

Cnemidophorus littoralis consumed 18 dif-ferent prey types consisting of 562 items (as shown in Table 1). Out of the 31 lizards examined, one female and one male had empty stomachs (9.1% among females; 5.9% among males and 6.4% of all lizards). Termites (68.0%), larvae (61.0%) and cockroaches (22.6%) were the most frequent items found in the stomachs (Table 1). The most important prey (by number) were termites (67.3%), followed by larvae (13.3%) (Table 1). Volumetrically, the most important prey were larvae (32.1%), cockroaches (11.2%) and termites (10.9%) (Table 1). One juvenile of the Gekkonid lizard Hemidactylus mabouia (SVL = 24.7 mm) was found in the stomach of an adult male (SVL = 60.1 mm). The Importance index showed that termites and larvae were the most important prey (Table 1).

Morphological variables of C. littoralis did not affect the number (JW: F_1,23 = 0.122, P = 0.730; SVL: F_1,26 = 1.952, P = 0.174), mean length (JW: F_1,18 = 0.020, P = 0.890; SVL: F_1,21 = 0.434, P = 0.517) or mean volume (F_1,18 = 0.146, P = 0.706; SVL: F_1,21 = 1.231, P = 0.280) of prey consumed by C. littoralis in Jurubatiba. Diets of adult males and females did not differ either in number (t = 1.205, df = 25, P = 0.239) or in volume (t = 0.390, df = 20, P = 0.700) of prey consumed.

Cnemidophorus littoralis moved most of the time (moving: 80%, = 439.0 ± 98.7 sec, N = 10; motionless: 20%, = 110.3 ± 61.1 sec, N = 10), similar to other active foraging lizards and ate prey that are relatively sedentary or that occur aggregated in the environment (Vitt, 1991; Zaluar & Rocha, 2000; Dias, 2002; Teixeira-Filho et al., 2003). Larvae and termites were predominant in the diet. Termites were the most important prey in terms of number, contributing to 67.3% of the items consumed. Termites and larvae are frequent items in the diet of other Brazilian active foraging lizards (Magnusson et al., 1985; Zaluar & Rocha, 2000; Teixeira-Filho et al., 2003).

The lack of relationship between the number, length or volume of prey and morphological variables of C. littoralis may result from the predominance of termites in its diet. These prey are characterized by their small sizes and small size variation. A similar trend was found by Teixeira-Filho et al. (2003) for C. littoralis in the restinga de Maricá. The diet of C. littoralis in the restinga de Jurubatiba was similar to that usually found in other Cnemidophorus species in Brazil (e.g. Vitt, 1995; Teixeira-Filho et al., 2003). Teiids, as actively foraging lizards, constantly tongue-flick while foraging to chemically detect and recognize prey before attacking (Cooper, 1990). This behaviour makes it easy to locate the prey with low mobility that is hidden inside the litter and under the surface of the ground.

We also found an intact and undigested hatchling of the crepuscular/nocturnal gekkonid lizard Hemidactylus mabouia in the stomach of an adult male of C. littoralis. In Brazil, other active foraging lizards species are known to prey on vertebrates (Cnemidophorus lemniscatus - Magnusson & Silva, 1993; Kentropyx striatus-Vitt & Carvalho, 1992; Ameiva ameiva Zaluar & Rocha, 2000). However, in the genus Cnemidophorus in Brazil, only C. lemniscatus was previously reported eating hatchlings of sympatric lizards (Magnusson & Silva, 1993). In restinga habitats, H. mabouia was previously found in the diet of the tropidurid lizard Tropidurus torquatus (Araújo, 1991) and of the colubrid snakes Oxyrhopus guibei (Colubridae) and Thamnodynastes cf. strigilis (Colubridae) (Vrcibradic & Rocha, 1998). This is the first record of H. mabouia in the diet of Cnemidophorus littoralis and shows that the gekkonid may be an occasional component of the C. littoralis diet. It also indicates this teiid lizard as a potential source of mortality of individuals of the sympatric H. mabouia in the restinga in Jurubatiba.

We conclude that Cnemidophorus littoralis in the restinga de Jurubatiba is an active foraging lizard and predominantly consumes larvae and termites and that small lizards may also be eaten.

Acknowledgments — This study is a part of the results of the "Programa de Pesquisas Ecológicas de Longa Duaração - PELD/CNPq of SITE # 05" developed in the Restinga in Jurubatiba and supported by CNPq and part of the "Programa de Ecologia, Conservação e Manejo de Ecossistemas do Sudeste Brasileiro" and of the Southeastern Brazilian Vertebrate Ecology Project (Laboratory of Vertebrate Ecology), of the Departamento de Ecologia, Instituto de Biologia, Universidade do Estado do Rio de Janeiro. Permission to collect the lizards was conceded by the Instituto Brasileiro do Meio Ambiente e Recursos Naturais Renováveis - IBAMA (Permit # 096/99-DIFAS). This study was partially supported by research grants from the Conselho Nacional do Desenvolvimento Científico e Tecnológico (CNPq) to CFDR (processes # 307653/03-0 and 477715/06-0), MVS (302405/02-0) and a graduate grant to VAM.

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Received December 12, 2004

Accepted April 28, 2005

Distributed August 31, 2006

Publication Dates

• Publication in this collection
  27 Sept 2006
• Date of issue
  Aug 2006

History

• Accepted
  28 Apr 2005
• Received
  12 Dec 2004