The Influence of Water Level on the Detection of Signs of Neotropical Otters ( Lontra Longicaudis ) on a Flood Plain

摘要

The aim of this study was to characterize the habitat used by the Neotropical Otter on a section of the floodplain, and to examine the influence of river level on the detection of scent marking, defined as spraint and/or anal mucus. Over one year, a section of 6 km of the left bank of the Paraná River was searched for scent marking. Those sites were classified by the type of substrate and frequency of use. A linear regression analysis was applied between river level and the number of marking sites found. Most of the positive sites have rocky substrate, followed by sandy. Just over half of the marking sites were only used occasionally, and few sites were associated with high activity. The abundance of rocky substrate when river level is low is probably responsible for the high frequency of otter sign detected. We suggest that studies on Lontra longicaudis marking in a floodplain should be carried out during periods of lower river level to facilitate the finding of otter sign. We emphasize that estimates of density and habitat preference cannot be based solely on marking sites, because both this behaviour and its detection are subject to variations due to many factors, including the oscillation of the river level.