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Ben Gurion University of the Negev (2013)

Extinction and re-colonization processes in the otter (Lutra lutra) population in Israel : the importance of connectivity and habitat quality

Shachal, Roni

Titre : Extinction and re-colonization processes in the otter (Lutra lutra) population in Israel : the importance of connectivity and habitat quality

Auteur : Shachal, Roni

Université de soutenance : Ben Gurion University of the Negev

Grade : Master of Science (MS) 2013

Résumé
The Eurasian otter (Lutra lutra) is a solitary mammal, inhabiting a variety of aquatic habitats, and feeding mostly on aquatic prey. Being a top predator, it is considered as a good bio-indicator species for aquatic habitats ; thus its continued existence is a conservation priority. The species has been listed in the IUCN Red List as “Near Threatened” and in Israel as "Critically Endangered" since 2004, due to its ongoing decline, resulting from water source drainage, water pollution, habitat fragmentation and degradation, and road effects. Roads, in particular, are one of the major factors threatening otter persistence and hampering movement between habitats. The Israeli otter population forms the southeastern border of the Mediterranean-Arab range of the species. As such, the habitats available to otters are limited to sparsely distributed natural streams, and to distinct artificial water reservoirs and fish ponds. Consequently, the population forms a metapopulation structure, of small local subpopulations, partially genetically differentiated, inhabiting spatially discrete patches linked by limited dispersal, which are subject to re-occurring local extinction and recolonization processes. This study aimed to investigate the extinction and re-colonization dynamics of the population, by evaluating their rates and their changes through time, and determining the relationship between them and the environmental characteristics of the habitats. Additionally, as part of the connectivity issue, I evaluated the effectiveness of II new ledges that were constructed under four "hot spots" bridges to prevent otter road kills. To answer these questions, I used a multi-model inference approach based on occupancy modeling (program MARK), which analyzed multiple-visits presenceabsence data (based on spraint detection) from 39 sites in in northern Israel from 2000- 2013. The model derived, for every year, the overall occupancy, extinction and recolonization rates. The various models included indices of habitat quality and connectivity for each site, comprised of factors known from the literature. To investigate the ledges’ effectiveness, I monitored their use by otters and other mammals, using foot tracks and I.R cameras. I found a continuous decrease in re-colonization rates and a moderate decrease in the proportion of occupied sites, but only a small increase in extinction rates through the years. Habitat quality, connectivity and the interaction between them revealed extensive effects on the parameters : overall occupancy and extinction are mostly affected by the above interaction, and re-colonization is mostly affected by the connectivity. Road ledges were used regularly by otters and other mammals. Long-term monitoring and evaluating population processes (occupancy, local extinctions and re-colonizations) are important for detecting negative changes in distribution in "real time," especially when the species is structured as a metapopulation in a highly fragmented and disturbed region. Identifying the environmental factors affecting these processes is crucial for proper management. As part of these management actions, road ledges may be used to mitigate road casualties and to enhance movement between different habitats. Additionally, conservation efforts for the isolated Israeli otter population should focus on the maintenance and restoration of habitats and their connecting ecological corridors.

Mots clés : Lutra lutra — Israel ; Lutra lutra — Israel — Recolonization ; Extinction (Biology) — Israel — Case studies

Présentation (BGU)

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Page publiée le 3 avril 2015, mise à jour le 26 novembre 2018