SHORTER COMMUNICATIONS Journal of Herpetology, Vol. 44, No. 2, pp. 314–320, 2010 Copyright 2010 Society for the Study of Amphibians and Reptiles Body Size, Population Size, and Age Structure of Adult Palmate Newts (Lissotriton helveticus) in Pyrenean Lakes FE ` LIX AMAT, 1,2 NEUS OROMI ´ , 3,4 AND DELFI ´ SANUY 2 1 A ` rea d’Herpetologia, Museu de Granollers–Cie `ncies Naturals, Francesc Macia ` 51, 08400, Granollers, Catalonia, Spain; E-mail: amatevi@worldonline.es 3 Escola Superior d’Enginyeria Agra `ria, Departament de Produccio ´ Animal (Fauna Silvestre), Universitat de Lleida, Av. Rovira Roure 191, 25198, Lleida, Catalonia, Spain ABSTRACT.—We used capture-recapture techniques and skeletochronological analysis to investigate body size, population size, and age structure of a population of Palmate Newts (Lissotriton helveticus) living in two adjacent lakes at 2,300 m in Andorra (Eastern Pyrenees). ; Females were larger (minimum–maximum, 31.0– 47.0 mm vs. 32.0–42.0 mm) and heavier (0.8–2.1 g vs. 0.5–1.8 g) than males. The total adult population of the two lakes is estimated at 338–245 individuals. Both sexes mature in three years; males live for nine years and females up to eight years. Interpopulational differences in demographic traits between this population and low-altitude populations of L. helveticus do not include the predicted pattern of delayed sexual maturity and larger longevity that would be expected to exist in higher altitude populations. Amphibians are increasingly being used by field- workers as models in biological research. A large body of literature on the demography of small newts belonging to the family Salamandridae (Lissotriton, Mesotriton, Cynops, and Nothopthalmus) has built up over the past 50 years (e.g., Miaud, 1990; Caetano and Leclair, 1996; Marunouchi et al., 2000). These newts have a biphasic life style consisting of an aquatic phase in lentic habitats during their breeding period and a cryptic terrestrial phase in the area immediately around these habitats (Arntzen, 2002a, Griffiths, 1996). Advances in salamandrid phylogenetics clearly indi- cate that this lifestyle evolved in several independent lineages within this family (Steinfartz et al., 2007; Zhang et al., 2008). Thus, comparative data from small newt populations offer the possibility of discovering whether or not species or populations living under differing climatic conditions exhibit demographic differences. In some cases, species or populations inhabiting higher altitudes may grow more slowly, mature and die at later ages, and reach larger minimum and maximum body sizes (Caetano and Castanet, 1993; Marunouchi et al., 2000; Kutrup et al., 2005). However, this may be an oversimplification of a more complex reality. In addition to climatic constraints on the activity of ectotherms such as aquatic newts, other factors may shape the demography of such species. In fish, for example, food availability, competition and nonran- dom predation have all been shown to affect demographic characteristics (Reznick et al., 1990; Rowe and Thorpe, 1990). Unfortunately, little research has been done on the putative causes of intraspecific demographic variability in amphibians. Indeed, it is very difficult to prove whether historical factors operating via genetic or physiological constraints determine population demographics. In this study, we provide data on the basic demographic attributes (range of body sizes, mini- mum age at sexual maturity, and longevity) and population size of a Palmate Newt (Lissotriton helveticus) population. To maximize the contrast with other populations of this species, we chose a popula- tion occupying a pair of geographically close Pyr- enean lakes at an unusually high altitude for this species. We discuss their demographic particularities and evaluate whether our high mountain population shows late sexual maturation at larger body size and has longer life expectancy in comparison to mid- and low-altitude populations. MATERIALS AND METHODS The Palmate Newt (L. helveticus) is a small, semiaquatic newt found in western Europe. It carries out its biological cycle in a wide variety of lentic habitats from sea-level to altitudes up to 2,400 m a.s.l. Our study was performed in two adjacent lakes in Soldeu (northeast Andorra) at 2,300 m. Both lakes have a similar surface area (2,150 and 2,300 m 2 ) and are only 20 m apart. Around the lakes, boulders, rocky outcrops, and pastures form a landscape without tree cover. Because of the high altitude, low temperatures, and snow accumulation, activity in this population is restricted to mid-May to October. Fieldwork was carried out in early June 2005. To estimate population size, we performed capture- recapture sampling on five consecutive warm sunny days. We sampled each lake five times a day by walking along the perimeter and carefully examining the waters of the shoreline, the part of the lake that the newts use almost exclusively for their aquatic activity. Although dip-netting is generally useful for sampling newts living in pools (Arntzen, 2002b), the physical characteristics of our lakes (clear, still water and an absence of aquatic vegetation) made it obvious that newts only use the shoreline and hence could be visually located and captured by hand. Sampling was always performed by the same person (FA), who spent a maximum of an hour at each lake during each sampling session. To minimize habitat disturbance, the two lakes were sampled alternately. Newts were sexed on the basis of external dimorphic sexual characters. Because of logistical limitations, we only Journal of Herpetology hpet-44-02-17.3d 25/3/10 12:19:04 314 Cust # 08-278R4 2 Corresponding Author. 4 E-mail: neusoromı ´@gmail.com