REPRODUCTIVE DYNAMICS OF A POPULATION OF SMALL MARBLED NEWTS (TRITURUS-MARMORATUS PYGMAEUS) IN SOUTH-WESTERN SPAIN

A breeding population of small marbled newts in a temporary pond in SW Spain was sampled over five successive years. Males and females enter ed the pond just after it flooded in autumn. The adult aquatic season persisted until March or April, with maximum capture rates occurring m ostly in January. Several sampling methods were used of which the most efficient was funnel trapping. Recapture rates were low. The populati on was estimated at about 1000 newts in 1987. Sex ratio did not differ from 1:1 in three seasons. In the other two seasons, which were chara cterized by low autumn rainfall, males outnumbered females by 2:1, pro bably as a result of many females failing to enter the pond to breed i n those years. In the last two study years, the mean body size of newt s was smaller than in previous years, possibly as a consequence of the adverse conditions of the two preceding autumns, which would have had repercussions for the growth of juveniles. An increase in physical co ndition and individual body mass throughout the aquatic season was obs erved in both sexes, confirming that the adult aquatic phase is advant ageous for growth and maintenance of newts, as well as being necessary for reproduction. The age structure of the population was obtained in one of the seasons. Most males and females were 2-3 years old and a s mall percentage was one year old. The frequency of 1 year old mature f emales was lower than that of males. Females showed higher survival ra tes than males.