Amphibia-Reptilia 32 (2011): 550-556 Age structure and growth in a population of Pelobates varaldii (Anura, Pelobatidae) from northwestern Morocco Fabio Maria Guarino 1,* , Philip de Pous 2,3 , Angelica Crottini 4 , Marcello Mezzasalma 1 , Franco Andreone 5 Abstract. Age structure and growth in the Moroccan spadefoot toad, Pelobates varaldii were estimated by skeletochronology and reported for the first time for a population living in NW Morocco. Snout vent length and body mass did not significantly differ between the sexes, although females appeared larger and heavier than males. Age ranged 2-7 years in males (mean age ± SD: 4.5 ± 1.2, n = 66) and 2-10 years in females (4.7 ± 2.4, n = 20). The difference in age was not significant between the sexes. The modal age was 5 years for males and 3 years for females. The age distributions significantly differed between the sexes. Von Bertalanffy growth curves showed a similar profile between the sexes although growth coefficient was higher in males than in females. Longevity and growth rates of P. varaldii were compared with those of other species of the genus Pelobates. Keywords: Amphibia, demographic traits, longevity, Moroccan spadefoot toad, skeletochronology. The Moroccan spadefoot toad (Pelobates varal- dii) belongs to the family Pelobatidae which in- cludes only three other species (P. cultripes, P. fuscus, and P. syriacus) with a wide distribution from Europe to Central Asia and Morocco (Bu- sack, Maxson and Wilson, 1985). Pelobates varaldii is known only from a few fragmented areas on the coastal plains of NW Morocco and it has been assessed as En- dangered (EN) according to IUCN Red List of Threatened Species (IUCN, 2010). Further- more, the Evolutionary Distinctive and Glob- ally Endangered (EDGE) program of the Zo- ological Society of London recently listed P. varaldii on place 36 of their EDGE global am- 1 - Dipartimento di Biologia Strutturale e Funzionale, Uni- versità di Napoli Federico II, Via Cinthia, I-80126 Napoli, Italy 2 - School of Biological Sciences, University of East An- glia, Norwich Research Park, Norwich NR4 7TJ, UK 3 - Society for the Preservation of Herpetological Diversity, Oude Molstraat 2E, 2513 BB, Den Haag, The Nether- lands 4 - CIBIO, Centro de Investigação em Biodiversidade e Re- cursos Genéticos, Campus Agrário de Vairão, R. Padre Armando Quintas, 4485-661 Vairão, Portugal 5 - Museo Regionale di Scienze Naturali, Via G. Giolitti, 36, I-10123 Torino, Italy * Corresponding author; e-mail: fabio.guarino@unina.it phibian top 100 based on the species Evolu- tionary Distinctiveness and Global Endanger- ment scores (Isaac et al., 2007). Similarly to the other spadefoot species, Pelobates varaldii is fossorial and largely nocturnal for most of the activity period that occurs in autumn-winter (Schleich, Kästle and Kabisch, 1996). Although ecology and habitat preference of this anuran begun to be recently investigated (de Pous et al., submitted), its demographic characteristics still remains largely unknown. On the other hand, the knowledge of individual life span and population age structure represents a priority to develop appropriate management strategies of threatened species. In this study, we aimed to: (1) determine individual age and growth, and age structure of P. varaldii using phalangeal skeletochronol- ogy from a population in the Mamora For- est (northwestern Morocco), (2) compare the demographic traits of P. varaldii with those obtained from skeletochronological studies on related pelobatid species. Skeletochronology proved to be one of the most reliable methods for assessing individual age and growth rates of many vertebrates, including amphibians (Cas- tanet et al., 1993). In addition, performing skele- tochronology on phalanges is relevant in con- © Koninklijke Brill NV, Leiden, 2011. DOI:10.1163/017353711X605678