The Eurasian otter Lutra lutra (Linnaeus, 1758) in Portugal

Abstract

La nutria eurasiática Lutra lutra (Linnaeus, 1758) en Portugal Lutra lutra (Linnaeus, 1758) igaraba eurasiarra Portugalen ABSTRACT Eurasian otters Lutra lutra (Linnaeus, 1758) are known to occur in Portugal since historical times but only in 1995 a national survey confirmed the species' broad distribution. Since then, studies and projects conducted in different aquatic environments indicate the existence of a healthy population, the availability of vegetation cover, water and prey being the major factors explaining otter presence. Spraint analyses showed that fish, amphibians and American crayfish form the bulk of otter diet. Due to increasing knowledge about the species ecology and distribution, in 2005, otter status was changed, from "Insufficiently Known" to "Least Concern". Recent main lines of investigation have become increasingly threat specific and include: otter use of reservoirs, man-otter conflicts (fish farming), otters and non-native species interactions (prevalence in otter diet; competition with American mink) and otters and antimicrobial resistant bacteria. Destruction of the riparian vegetation commonly associated with dam construction, river regulation, agricultural expansion, gravel and sand extraction, as well as the development of tourism in, costal and wetland areas are still potential threats to otter populations. Overall, in the near future otters seem safe from major disrupting settings but otter conservation and effective management are still an important issues. This is especially relevant in the Iberian Peninsula, as climate changes are expected to reduce suitable otter habitats. Knowledge gaps and future research needs are also addressed in this chapter. KEYWORDS:Conservation, otter, Portugal, research, status. RESUMENLa presencia de la nutria euroasiática Lutra lutra (Linnaeus, 1758) en Portugal se conoce desde tiempos históricos, pero no fue hasta 1995 cuando gracias a un sondeo nacional se confirmó la amplia distribución de la especie. Desde entonces, se han realizado múltiples estudios y proyectos en diferentes ambientes acuáticos que indican la existencia de una población sana, siendo la disponibilidad de cobertura vegetal, el agua y las presas los principales factores que explican la presencia de la nutria. Los análisis de excrementos mostraron que los peces, los anfibios y el cangrejo de río americano forman el grueso de la dieta de la nutria. Debido al aumento de los conocimientos sobre la ecología y distribución de la especie, en 2005, el estado de la nutria pasó de "Insuficientemente Conocida" a "Preocupación Menor". Recientes líneas de investigación se han dado a conocer un aumento de amenazas específicas que incluyen: el uso de los embalses por parte de las nutrias, los conflictos hombre-nutria (acuicultura), y las interacciones entre las nutrias y las especies no nativas (prevalencia en la dieta de la nutria , la competencia con el visón americano) y las nutrias y bacterias resistentes a los antimicrobianos. La destrucción de la vegetación de ribera asociada comúnmente ...

Habitat Use by Pseudochondrostoma duriense and Squalius carolitertii Downstream of a Small-Scale Hydropower Plant

“…Another issue that may have compromised our detection rate is associated with the river ecosystem. Located in a mountainous and remote area, the studied reach harbors the mammal, European otter, with a diet including small-sized fish [54]. We hypothesized that fish would be eaten by the otters and tags would be afterwards excreted in the river banks, and, thus, lost for the accounting.…”

“…The remainder fish either: (i) were located in the study area, but may have escaped downstream while the operator with the portable antenna was moving upstream to detect fish; (ii) were located in a deep area perhaps below a boulder and the receiver was out of range, (iii) could have been eaten by animals at a higher level of the food chain, such as the European otter (Lutra lutra) [54] not spotted during the field sampling events, or (iv) could have moved longer distances downstream and left the studied reach.…”

Presence of the Eurasian otter Lutra lutra on the islands of Greece: a review

“…Lack of permanent freshwater wetlands and lotic waters could affect otter survival since food supply may become scarce and food availability could be a major constraint in their distribution and abundance (Ruiz-Olmo et al 2001). Studies in Mediterranean areas, where wetlands dry-out during summer and freshwater availability is limited, show that otters may shift their diet or travel between watersheds to find suitable habitats to withstand extreme conditions (Galanaki 2000, Prenda et al 2001, Ruiz-Olmo et al 2001, Clavero et al 2003, Smiroldo et al 2009, Pedroso et al 2014. Freshwater is also vital for otters for drinking and to wash salt out of their fur, which may otherwise lose its insulative properties (Beja 1992, Kruuk 2006.…”