Seasonal breeding and food resources of otters, Lutra lutra (Carnivora, Mustelidae), in south-west Portugal: A comparison between coastal and inland habitats

Data on the breeding chronology and litter sizes of otters inhabiting coastal and inland habitats in Southwest Portugal were obtained, primarily through inquiries carried out to local fishermen, farmers and shepherds. In coastal habitats otters were mostly born from October to December, whereas inland they were mostly born from January to March. This difference in breeding seasonality between both habitats was associated with the distinct patterns of seasonal prey availability. In the coast the first months of lactation (the most energetically demanding in the female carnivore) were associated with the peak abundance of corkwing wrasse Symphodus melops, occurring in December-March whereas inland they were associated with the period of most predictable high availability of eels Anguilla anguilla, occuring in spring and early summer. The mean litter size in the coast (1.7) was consistently smaller than inland (2.9). Possible reasons for this disparity, which seems to be the rule for coastal and inland populations across Europe, are discussed.