The demography of the lizard Tropidurus torquatus (Squamata, Tropiduridae) in a highly seasonal Neotropical savanna

Abstract

The demography of the lizard Tropidurus torquatus (Squamata, Tropiduridae) in a highly seasonal Neotropical savanna. The demography of a population of Tropidurus torquatus was studied from March 1996 until December 1998, in the Cerrado biome of central Brazil, using the method of capture and recapture. Population size, number of incoming individuals in the population, and age structure varied seasonally, reflecting the reproductive cycle of the species. The instantaneous rate of population increase did not differ from zero throughout the study. In general, the permanence rates of juveniles and adults were low, indicating a large turnover of individuals in the population, with a maximum life expectancy of three years. The sex-ratio among adults was biased toward females. Since no bias was observed among juveniles and there was no difference in adult permanence between sexes, we suggest that the biased adult sex-ratio resulted from a lower permanence of males during a short ontogenetic period, when secondary sexual characteristics develop. When compared to T. itambere, the studied population of T. torquatus attained a higher density and a greater female bias in the sex-ratio. In general, the studied population presented characteristics that, according to life history theory, should be associated with early age at maturity and polygyny: short life expectancy, high population turn over, and female biased sex-ratios.

Population Dynamics ofTropidurus torquatus(Wied, 1820) (Squamata, Tropiduridae) in Southern Brazil

“…The population of Tropidurus torquatus studied at Alegrete presented a marked cyclic variation in population structure, possibly associated to the reproductive cycle of the species (Wiederhecker et al, 2003). an increase in number of individuals in the population was observed during the reproductive season (from September to December) and after the recruitment which becomes expressive in February and March, followed by a strong decrease after these months.…”

“…According to Verrastro (1991), in theory, the loss of individuals from the population may occur due to two main reasons: 1) before reproduction -from October to the beginning of summer -high juvenile mortality or escape of the adults from the residency area may occur; 2) at the end of the summer -the decrease of adults would be related to mortality right after the reproductive period. According to Wiederhecker et al (2003) most individuals of T. torquatus disappear after the first reproductive season. In addition, Van-Sluys (2000) states that the decrease in density and biomass may also reflect the inactivity of the species.…”

“…Studies with this species generally focus on ecological aspects including sexual dimorphism (Pinto et al, 2005), reproduction (Gomides et al, 2006;Wiederhecker et al, 2002), demography (Wiederhecker et al, 2003), activity patterns (Hatano et al, 2001), thermal ecology (Kiefer et al, 2005;Kiefer et al, 2007;Nunes et al, 2007;Ribeiro et al, 2007), and feeding behavior (Fialho et al, 2000;Carvalho et al, 2007). However, all these studies have been carried out in the Central-East and Southeast regions of Brazil.…”

Demography of Xenosaurus platyceps (Squamata: Xenosauridae): a comparison between tropical and temperate populations

“…In spite of extensive research on lizard life histories (see Clobert, Garland and Barbault [1998] and references therein), most studies have been focused on short-lived species that live in temperate environments. Thus, current conclusions about demographic and life history patterns of lizards species are biased and generalizations are still limited (Widerhecker, 2003;Du et al, 2005;Iverson et al, 2006).…”

First records of Tropidurus callathelys and T. chromatops (Reptilia: Squamata: Tropiduridae) in Brazil

“…Recent works revealed undescribed species and a still unknown diversity within Tropidurus (Passos et al 2011;Kunz and BorgesMartins 2013). These lizards are diurnal and heliophilous (Rocha and Bergallo 1990;Vitt 1993;Vitt et al 1996;Gandolfi and Rocha 1998;Kiefer et al 2005Kiefer et al , 2007Ribeiro et al 2008), sit-and-wait foragers that feed predominantly on ants (Colli et al 1992;Bergallo and Rocha 1994;Faria and Araujo 2004;Van Sluys et al 2004;Carvalho et al 2007;Ribeiro and Freire 2011), and reproduce primarily during the wet season (Vitt and Goldberg 1983;Van Sluys 1993, 1998, 2000Van Sluys et al 2002;Wiederhecker et al 2002;Wiederhecker et al 2003).…”