Lutra Lutra) Population in Israel - the Importance of Connectivity and Habitat Quality
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Ben-Gurion University of the Negev The Jacob Blaustein Institutes for Desert Research The Albert Katz International School for Desert Studies Extinction and re-colonization processes in the otter (Lutra lutra) population in Israel - The importance of connectivity and habitat quality Thesis submitted in partial fulfillment of the requirements for the degree of "Master of Science" By: Roni Shachal November 2013 I Extinction and re-colonization processes in the otter (Lutra lutra) population in Israel - The importance of connectivity and habitat quality By Roni Shachal Thesis submitted in partial fulfillment of the requirements for the degree of "Master of Science", Ben-Gurion University of the Negev, Jacob Blastein Institute for Desert Research, Albert Katz International School for Desert Studies, 2013. 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 re- colonization 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 presence- absence 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 re- colonization 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. III Acknowledgments I want to thank my supervisors Dr. Amit Dolev and Prof. David Saltz, for giving me a great opportunity to study this wonderful animal, and to be a part of this interesting and important project. I would also like to thank the ecologists of the NPA and to the managers and rangers of the reserves, Talia Oron, Ifat Artzi, Hava Goldstein, Rabia Dabus, Nahel Dabus, Yoram Malka and many more, for the help in the field work and in everything else that was needed. Many thanks to Tomer Gueta, for all the great and friendly help in the GIS analysis. To Amos Bouskila, who was the first to introduce me to the world of Ecology and the study of nature. To Assaf Ben-David, who introduced me to the world of foot-prints. To all the people, friends and family who came to search for otter feces with me… To Shay, for all the support, ideas and motivation through the way. And to Aya & Amir, who gave me a warm and most friendly home while doing the field work in the north for the last two years. This study was supported and was done in collaboration with the Mammals Research Center of the Society for the Protection of Nature in Israel, and with the Nature and Park Authority. IV Table of Contents 1 INTRODUCTION .................................................................................5 1.1 Research objectives ................................................................................... 14 1.2 Hypotheses........... ....................................................................................... 15 2 METHODS ......................................................................................... 16 2.1 Study area……………… .................................................................................. 16 2.2 Field work and data collection ................................................................ 19 2.3 Data analysis. .............................................................................................. 21 2.3.1 Occupancy models ..................................................................................... 21 2.3.2 Indices of environmental covariates .......................................................... 22 2.3.3 Statistical Analysis ..................................................................................... 33 2.3.4 Model construction process ....................................................................... 36 2.4 Monitoring the effectiveness of the ledges .................................................. 39 2.4.1 Track pads:............................................................................................... 40 2.4.2 I.R Cameras: ............................................................................................. 41 3 RESULTS............................................................................................. 43 3.1 Covariate values ............................................................................................. 43 3.1.1 Habitat quality.......................................................................................... 43 3.1.2 Connectivity ............................................................................................. 43 3.2 Model selection results .................................................................................. 45 3.3 Trends in time ............................................................................................... 48 3.3.1 Changes in proportion of occupied sites through time ......................................... 48 3.3.2 Changes in re-colonization probabilities through time......................................... 48 3.3.3 Changes in extinction probabilities through time................................................. 49 3.4 Effect of environmental factors ..................................................................... 50 3.4.1 The effect of interaction between habitat quality and connectivity ........... 50 3.4.2 Site connectivity effect on extinction, re-colonization and overall occupancy...... 51 3.4.3 Habitat quality effect on extinction and overall occupancy ................................. 52 3.4.4 Sensitivity Analyses Results ................................................................................ 53 3.5 Monitoring the effectiveness of the ledges ................................................... 55 3.5.1 Track pads.................................................................................................... 55 3.5.2 I.R Cameras:.................................................................................................. 55 4 DISCUSSION ........................................................................................ 56 5 REFERENCES ....................................................................................... 70 6 APPENDICES ....................................................................................... 79 4 1 Introduction The Eurasian otter (Lutra lutra) is a nocturnal, solitary mammalian top predator (Carnivora: Mustelidae), inhabiting a variety of aquatic habitats, such as rivers with clean running water, as well as water reservoirs and fishponds adjacent to these streams, and feeding mostly on aquatic prey (Kruuk 2006). As predators at the top of many freshwater food chains (Ruiz-Olmo 2007) that are sensitive to water