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

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.

Distribution, status, and recent population dynamics of Alpine ibex Capra ibex in Europe

“…The European distribution of Alpine ibex presented in this study confirms that the species is currently present on the entire Alpine arc, with 178 colonies and more than 53000 individuals. A previous attempt to estimate the number of Alpine ibex produced a total number of 50195 ± 1012 individuals in 2013 (De Danieli & Sarasa 2015), which is consistent with the estimate of our model for that year.…”

“…Comparing the total number of individuals estimated in our study for 2015 (N = 55297; lower 95% CrI: 51157; upper 95% CrI: 62710) with the minimum number reported for 2005‐2007 (Apollonio et al 2009, N = 47000 individuals), with the unofficial report provided during the GSE‐AIESG meeting in 2012 (N = 49000‐50000 individuals), and with the estimate by De Danieli and Sarasa (2015) for 2013 (N = 49000‐51000 individuals), the overall number of individuals appears to have increased slightly over the last 10 years. Nevertheless, our linear model does not provide clear evidence of a numerical increase in the total number of individuals during the years 2004‐2015, due to the high level of uncertainty around the estimates.…”

“…However, the different management strategies in the European countries (for a brief description of the management regulations in the European countries hosting Alpine ibex populations, see Appendix ) and the lack of a communal policy on data sharing have resulted in fragmented information about the current status of the species. Some information is published in regional and national reports (also reviewed by De Danieli & Sarasa 2015), but much remains unpublished. Despite its recent successful reintroduction history and the strong interest in this charismatic species, a comprehensive and current update of the distribution and status of Alpine ibex is still lacking.…”

Sustaining Transmission in Different Host Species: The Emblematic Case ofSarcoptes scabiei

“…Direct contact among individuals is generally considered the primary mechanism of S. scabiei transmission for many host species (Walton et al 2004, Arlian andMorgan 2017), particularly those that are social (living in herds, packs, and family groups) and have frequent interindividual contact (Lunelli 2010, Kołodziej-Sobocińska et al 2014, Danieli and Sarasa 2015. Whether S. scabiei persists endemically, becomes epidemic, or goes locally extinct is likely determined by the rate and nature of contacts among individuals (which can be a function of density) and their susceptibility to clinical disease (Sugiura et al 2018, Niedringhaus et al 2019a.…”

“…This has been attributed to males living in larger groups, higher rates of contact with other individuals, and a decreased immune response compared with females, which collectively promote further transmission (Lopez-Olvera et al 2015). Nevertheless, the specific role of ibex population structure in enhancing pathogen transmission, establishment, and persistence has so far been poorly documented (Danieli and Sarasa 2015).…”