Temporal and spatial patterns of rest-site use by four female otters Lutra lutra along the south-west coast of Portugal


  • Pedro Rui Beja

    1. Laboratório Maritimo da Guia Forte de Na Sra da Guia, 2750 Cascais, Portugal
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      Parque Natural do Sudoeste Alentejano e Costa Vicentina, Rua Serpa Pinto, 32, 7630 Odemira, Portugal


Data from four radio-tracked female otters (Lutra lutra) were used to describe the temporal and spatial patterns of resting-sites by the species along the south-west coast of Portugal. Two female otters were tracked during 24-h periods, showing a continuous resting period in daylight, whereas during the night there were several hunting bouts in the sea interspersed with periods ashore. These otters spent most of the time each day in daytime rest-sites (72.1%), and devoted only a small time to hunting (18.3%) and other activities (9.6%). The onset of fishing activity was monitored for three animals, starting on average 45.4min after sunset; this was largely independent of the degree of human disturbance close to the rest-sites. Most rest-sites were located within dense thickets of Rubus sp. along coastal and estuarine streams, and sometimes they were near areas disturbed by human activities. Three otters were captured along the coast and they were found in eight daytime rest-sites on 116 occasions, each otter using regularly a small number of sites (2.7); the mean re-use rate of sites was high (9.5 days per site), and the sites were spread over 4.2-15.0km of coast, with 0.20-0.71 sites/km. One otter was captured in an estuarine stream, where she was found on 70 occasions in 13 daytime rest-sites spread over 6.0 km of streams; the density of rest-sites was 2.2 sites/km and the re-use rate was 5.4 days/site. The results of this study suggest that rest-sites are scarce for marine-feeding otters in south-west Portugal. This is probably because rest-sites used by these otters have an obligatory association with freshwater sources, and these are infrequent and scattered along this coast. Conservation implications of this study are discussed.