Age and size structure of populations of small marbled newts (Triturus marmoratus pygmaeus) from Donana National Park (SW Spain). A case of dwarfism among dwarfs

The body size of specimens of Triturus marmoratus pygmaeus from Donana is the smallest recorded for this subspecies. Snout-vent length averages 42.3 mm in males, and 43.9 mm in females. Mean body mass in males is 2.04 g and 2.29 g in females. The age of newts was estimated by means of skeletochronological methods. The maximum longevity recorded was 10 years in females and nine years in males, with one or two years being the age at maturity. As in other newts, body size is not a good predictor of age, since a wide range of body length was found within each age class. Growth in females was substantial in subsequent years, showing an overall positive tendency. However, males showed slight or even negative growth. Newts from Donana are different from other nearby localities with similar climatic characteristics. This is mainly due to their short juvenile and terrestrial phase.