First insights on habitat use by the endemic Selvagens gecko (Tarentola boettgeri bischoffi)

First insights on habitat use by the endemic Selvagens gecko (Tarentola boettgeri bischoffi) Andreia Penado1§, Marta Sampaio1§, Ricardo Rocha1, Vanessa Gil1, Bruno Carreira1 and Rui Rebelo1* 1 * Correspondence Centro de Biologia Ambiental, Departamento de Biologia Animal, Faculdade de Ciências da Universidade de Lisboa, Bloco C2, Campo Grande, 1749-016 Lisboa, Portugal author: mrebelo@fc.ul.pt Introduction Tarentola boettgeri bischoffi Joger, 1984 is a medium sized nocturnal gecko endemic to the Selvagens archipelago, Madeira, Portugal. This species occurs in 3 isolated sub-populations in the three main islands of the archipelago: Selvagem Grande, Selvagem Pequena and Ilhéu de Fora1. Due to its small area and simplified biota, these islands are an ideal system to analyse habitat use. Despite the recent increase on studies concerning the selection of habitat and retreat sites in reptiles, only a few studies concern geckos. Here we assess habitat use by the endemic Selvagens gecko T. b. bischoffi in the arid central plateau of Selvagem Grande, Portugal. © Ricardo Rocha Methods During 2010 and 2011, we collected data on habitat characteristics (bush height, rock area, distance to the nearest rock, distance to the nearest bush, canopy diameter, presence of brook beds) surrounding 168 rocks used as a retreat site by the geckos, as well 77 randomly selected rocks. We also recorded body measurements of the individuals caught under each rock: SVL (cm), body mass (g), sex and age class (adults/juveniles). We used the residuals of the linear regression of body mass against SVL as an index of body condition. a) Results and discussion 40 1. WHICH HABITAT CHARACTERISTICS INFLUENCE GECKOS CHOICE? During the day, Selvagens geckos were found mainly under LARGE ROCKS that probably offer adequate thermoregulation conditions or protection against predators (Fig. 1a). During spring, BROOK BEDS (formed only after strong rains) can provide a cooler environment with high humidity. Geckos chose to retreat under rocks close to these sites possibly to avoid dehydration and overheating (Fig. 1b). In the dryer autumn season, they continued to use large rocks, but near HIGH BUSHES instead possible associated to a higher food availability (Fig. 1.c). a) R2=0.04476 b) c) b) R2=0.07143 R2=0.04812 Fig. 2: Generalized linear regression showing the relationship between a) √r rock area and SVL (P<0.05, n=128); b) √rock area and 3√body mass (P<0.05, n=128); c) √rock area and body condition of adult males (P<0.05, n=48). 35 33.2 31.9 30 25.2 23.6 c) 40 60 35 58 30 56 28.1 25 52 20 20 50 15 15 10 10 5 5 42 0 0 40 (P<0.001, n=205) Autumn (P<0.001, n=105) 51.3 54 25 Spring 54.3 14.9 48 46 44 Spring Autumn (P<0.05, n=205) (P=0.05, n=105) Fig. 1: a) mean ± SE √rock area; b) percentage of nearby brood beds; c) mean ± SE bush height. Occupied, random. 2. WHICH INDIVIDUALS OCCUPIED LARGER ROCKS? During spring: Individuals with a LONGER SVL and HEAVIER MASS (Fig. 2a and 2b).  Intraspecific competition may be an ecological factor prevalent in this species whereby larger and older individuals occupy larger rocks. ADULT MALES IN BETTER BODY CONDITION (Fig. 2c).  As the breeding season corresponds to the spring months, we suggest that our results might indicate the existence of spring territoriality in Selvagens gecko males. Territorial behaviour in geckos seems to be a promising research area, however, it has been overlooked when compared to studies on the remaining squamata. Acknowledgments: We are grateful to xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx References: 1. (2008) Tarentola bischoffi. In: Atlas dos Anfíbios e Répteis de Portugal, p. 188-189. Loureiro, A., Ferrand de Almeida, N., Carretero, M.A., Paulo, O.S. Eds., Lisboa, Instituto de Conservação da Natureza e da Biodiversidade. 2. López-Ortiz, R. and Lewis, A. R. (2004) Habitat selection by Sphaerodactylus nicholsi (Squamata: Gekkonidae) in Cabo Rojo, Puerto Rico. Herpetologica. 60:438–444.