Population estimates, density–dependence and the risk of disease outbreaks in the Alpine ibex Capra ibex

M Sarasa,C De Danielli

doi:10.32800/abc.2015.38.0101

Abstract

Wildlife monitoring and the identification of factors associated with disease outbreaks are major goals in wildlife conservation. We reviewed demographic and epidemiological data for the Alpine ibex Capra ibex from 1975–2013 to characterize the species’ abundance and distribution dynamics on a large scale. We also explored methodological bias in monitoring and analyzed the factors potentially associated with the risk of disease outbreaks. Our results revealed that the overall abundance and distribution of Alpine ibex appeared to be increasing at both national and international scales, in agreement with the IUCN’s ‘Least Concern’ conservation status on the international scale and on the national scale for Italy, Switzerland and France. Our comparative analysis of common monitoring methods highlights the fact that abundance values from counts are underestimated and suggests that the Alpine ibex is more abundant than is usually reported. The appearance and persistence of disease outbreaks (e.g. sarcoptic mange, keratoconjunctivitis or brucellosis) are related to local ibex density and abundance. The observed correlation between the demographic growth of ibex populations and disease outbreaks suggests that the risk of epizooties may be increasing or might already be high in several populations of Capra ibex.

Highlights

The genus Capra includes flagship species living in rupicolous and mountain environments that were the subject of conservation, reintroduction and management programs during the past century (Stüwe & Nievergelt, 1991; Pérez et al, 2002)
We searched for data from all the countries in which Alpine ibex exist in the wild (Italy, Switzerland, France, Austria, Germany and Slovenia); most published data came from Italy, France and Switzerland
The predicted values of the generalized additive models (GAM) suggest that, in agreement with national reports, at both national and international scales, the Alpine ibex has increased in abundance (Apollonio et al, 2009; Corti, 2012)

Summary

Introduction

The genus Capra includes flagship species living in rupicolous and mountain environments that were the subject of conservation, reintroduction and management programs during the past century (Stüwe & Nievergelt, 1991; Pérez et al, 2002). Known as the Alpine ibex due to its distribution (Sarasa et al, 2012), is a good example of this phenomenon This species is present in the wild in at least six countries (Italy, Switzerland, France, Austria, Germany and Slovenia) and national reports from Italy and France reveal that its abundance and distribution is increasing (Apollonio et al, 2009; Corti, 2012). It was threatened by extinction at the beginning of the twentieth century but today is found in numerous colonies that are occasionally exposed to risk of disease outbreaks (Couturier, 1962; Gauthier et al, 1991; Stüwe & Nievergelt, 1991; Apollonio et al, 2009). Such research can aid in the identification of key factors regarding the compatibility —defined as a population’s predisposition as a suitable environment for potential outbreaks (Combes, 2001)— to disease outbreaks on a population scale

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Conclusion