The Cabrera Vole, Microtus Cabrerae, in Spain: a Biological and a Morphometric Approach

Abstract

The reproduction and morphometric characteristics of 148 Cabrera voles (Microtus cabrerae) from several Spanish locations were investigated. Males coming from a vole colony in Madrid show that there is a significant reduction in testis size between February and May, which suggests a decrease in the breeding activity at least at the end of spring, and probably into summer. The median litter size for this population was 4.91 (n = 11, sd = 1.51, range = 3-7). The lack of significant sexual differences in body dimensions and the relatively small testis of adult males suggest, following HESKE & OSTFELD (1990), that the Cabrera vole has a monogamous mating system. Males and females do not differ significantly in skull dimensions. Allometric analyses of skull variables show that during postnatal life the splanchnic region increases most strongly in relation to increasing dimensions of the brain case. The zygomatic arches widen noticeably during postnatal life, probably in connection with the development of the lateral masseter muscle. The articular process grows allometrically in relation to the elongation of the mandible, because of the pronounced mass development of the masseter and lateral pterygoid muscles. The biometric homogeneity between geographic populations reported herein corroborates previous morphological and biochemical results, and supports the opinion that there is no reason to maintain a subspecific distinction within M. cabrerae.