%0 Journal Article
%T A Model of the Effect of Environmental Variables on the Presence of Otters along the Coastline of the Isle of Skye
%A Paul Yoxon
%J International Journal of Biodiversity
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/386723
%X A survey of Eurasian otters (Lutra lutra) along the Skye coastline revealed a variation in distribution on different coastal types. Factors like geology, width of the intertidal zone, intertidal makeup, slope of coastline, inland vegetation, and number of freshwater pools could influence otter distribution. A quantitative method based on a logistic regression model is applied to take into account three scalable and four categorical environmental variables which may or may not affect otter distribution. Otter presence or absence in 500£¿m coastal sections was compared with binary dependent variables and a set of independent variables on 622 coastal sites. Analysis shows that this method can be used to characterise combinations of factors to predict if otters are likely to occur on a particular coastline. Geology, height 25£¿m above High Water Mark (indicating slope of coastline), and number of freshwater pools all affect otter utilisation of the coastal zone. Coastlines with Torridonian and Mesozoic rocks and the Landslip area show a positive effect on otters, while all other coastlines have a negative effect. Although primarily of theoretical importance, the model could be used as a tool to locate coastlines elsewhere which are of potential conservation importance for otters. 1. Introduction The Isle of Skye is renowned for its geology, largely because of the huge variation in age and rock type (see Figure 1). Figure 1: Geological coastal zones of the Isle of Skye. The oldest rocks are the Lewisian gneiss, which are up to 3,000 million years old and are in fact the oldest rocks in Britain. They are banded metamorphic rocks which have been altered by heat and pressure, and they form rugged, rocky coastlines. Lewisian rocks form much of the Sleat peninsula together with the Torridonian sandstone. The Torridonian is made of silica grains cemented together with silica which makes it impermeable, and so there are many freshwater pools. Cambrian rocks on Skye are mostly quartzite sandstones or limestones, although the limestones have been altered to form marbles as a result of the heat from Tertiary volcanic activity. Jurassic sediments, comprising mainly sandstones, limestones, and shales, form gently sloping shorelines. The youngest rocks are the Tertiary volcanics and intrusive. Volcanic rocks are those which are molten when they reach the earth¡¯s surface, but if they solidify within the earth, they are said to be intrusive. On Skye most of the volcanic rocks are in the north of the island and are basalts. Minor intrusions are formed when magma is pushed
%U http://www.hindawi.com/journals/ijbd/2013/386723/