Distribution and sprainting activity of the Otter (<i>Lutra lutra</i>) in the Pollino National Park (southern Italy)

Abstract

From March 2001 to December 2002, 32 stretches (sampling stations, mean length 673 m) distributed on 17 watercourses of the Pollino National Park (southern Italy) and the surrounding area were searched monthly for otter Lutra lutra signs, mainly spraints. All the watercourses were positive for otter with a mean percentage of 82.2%, indicating a stable presence of otters, mainly on Sinni and Mercure-Lao catchments (central-northern part of the park). Mean sprainting activity was 12.8 sprainting sites/km and 31.7 spraints/km, and showed a seasonal variation only in 2001 with two peaks, in May-June and in October. Sprainting activity was positively correlated with the percentage of positive stretches on watercourses, confirming that spraint density can represent an indicator of the population size of otters. A preliminary evaluation of the relationship between fish availability and otter marking intensity was performed along 39 km of the River Sinni on one day. A positive correlation was found between sprainting intensity (spraints/km) and the number of suitable sites for fish, such as pools or stretches of streams with good vegetation cover. Sprainting activity seemed to be linked to the distribution of fish availability. Since the Pollino National Park occupies a strategic position within the Italian otter range, an accurate management plan is needed to improve the quality of riverine ecosystems and to conserve otters.