Development of the fire salamander larvae at the altitudinal limit in Lombardy (north-western Italy) : effect of two cohorts occurrence on intraspecific aggression

During 2013, we surveyed the larval population of the fire salamander that inhabits different pseudo-artificial headwater pools in Lombardy, Italy. To understand altitude effects on breeding, larval development and intraspecific aggression, we focused on sites at the altitudinal limit for the spawning of the species in this region (around 1491 m a.s.l.). Sites have been visited two times per month between spring and autumn; in each pool, larvae were collected, weighed, measured and individually recognized. We assessed the density of larvae and the frequency of injured ones. Through pipe-sampling we monitored prey biomass and density. Our study verifies that two cohorts of fire salamander larvae exist in the pools at the altitudinal limit in Lombardy. Moreover, we found the deposition of two eggs with abortive embryos inside. Larvae that were laid in April 2013 reached a total length of 47.0 to 62.5 mm by October. Pools hosted high prey density, but low biomass. The frequency of injured larvae found was generally higher than reported for caves and lower than observed in cases of high predation pressure by Odonata larvae. The deposition of abortive eggs represents the first record of this phenomenon for the populations of fire salamander of the Pre-Alps. Generally, our study provides new data on fire salamander larvae growing at high altitudes.