Assessing the Risk of Extinction for the Brown Bear (Ursus arctos) in the Cordillera Cantabrica, Spain

Abstract

The status of the brown bear (Ursus arctos) in Spain has suffered a dramatic decline during the last centuries, both in area and numbers. Current relict populations are suspected to be under immediate risk of extinction. The aim of our model is to attain an understanding of the main processes and mechanisms determining population dynamics in the Cordillera Cantabrica. We compile the knowledge available about brown bears in the Cordillera Cantabrica, northern Spain, and perform a population viability analysis (PVA) to diagnose the current state of the population and to support current management.The specially constructed simulation model, based on long-term field investigations on the western brown bear population in the Cordillera Cantabrica, includes detailed life history data and information on environmental variations in food abundance. The method of individual-based modeling is employed to simulate the fate of individual bears. Reproduction, family breakup, and mortalities are modeled in annual time steps under the influence of environmental variations in food abundance, mortality rates, and reproductive parameters. In parallel, we develop an analytical model that describes the mean behavior of the population and that enables us to perform a detailed sensitivity analysis.We determine current population parameters by iterating the model with plausible values and compare simulation results with the 1982-1995 time pattern of observed number of females with cubs of the year. Our results indicate that the population suffered a mean annual decrease of ϳ4-5% during the study period, 1982-1995. This decrease could be explained by a coincidence of high poaching pressure with a series of climatically unfavorable years during the period 1982-1988. Thereafter, population size probably stabilized. We estimate that the population currently consists of 25 or 26 independent females and a total of 50-60 individuals. However, our viability analysis shows that the population does not satisfy the criterion of a minimum viable population if mortalities remain at the level of the last few years of 1988-1995. The ''salvation'' of at least one independent female every three years is required.The population retains relatively high reproductive parameters, indicating good nutritive conditions of the habitat, but mortality rates are higher than those known in other brown bear populations. The most sensitive parameters, adult and subadult mortality of females, form the principal management target. Our model shows that the series of females with cubs contains valuable information on the state of the population. We recommend monitoring of females with cubs as the most important management action, both for collecting data and for safeguarding the most sensitive part of the population.

Evidence for improved connectivity between Cantabrian brown bear subpopulations

“…Th e brown bear Ursus arctos population in the Cantabrian Mountains (northwest Spain) is one of the most endangered in the world (Zedrosser et al 2001), mainly because of low numbers and limited habitat availability (Wiegand et al 1998, Naves et al 2003, Martin et al 2012. Th is brown bear population is the most southwestern in Europe and it has been completely isolated from other bear areas for centuries (Sorensen 1990, Zedrosser et al 2001.…”

“…Since the fi rst half of the 20th century, the Cantabrian bear population has been divided into two subpopulations (western and eastern), both occupying roughly the same amount of area ( ∼ 3700 km 2 ). Estimates of population size in the early 1990s yielded fi gures of only 55 -60 individuals for the western subpopulation (Wiegand et al 1998) and about 14 individuals in the eastern one (Clevenger and Purroy 1991). Th is reduction has also been noted at the level of genetic diversity (Valdiosera et al 2008(Valdiosera et al , P é rez et al 2009.…”

“…Opportunistic data of females with cubs-of-the-year (Fcub), based on direct observations and track signs collected by rangers and researchers, have been used to perform a non-spatial demographic population viability analysis of the western subpopulation with data for the period 1982 -1995 (Wiegand et al 1998). More recently, Fcub data from 1994 to 2004 were analyzed and a trend was interpreted as an increase in population size (Palomero et al 2007a).…”

“…In 2004, Palomero et al (2007b) estimated 105 -130 bears for the entire population. Nevertheless, the use of opportunistic Fcub data to estimate population size and trends (Eberhardt and Knight 1996, Wiegand et al 1998, Palomero et al 2007a has been cautioned for small bear populations (Brodie and Gibeau 2007, Harris et al 2007, Fern á ndez-Gil et al 2010.…”

Exploring the potential of brown bear (Ursus arctos arctos) as a long-distance seed disperser: a pilot study in South-Western Europe

“…Several countries are currently undertaking significant efforts to protect and reinforce local populations that have been on the verge of extinction (Taberlet et al 1997, Wiegand et al 1998, Mustoni et al 2003, Preatoni et al 2005, Mateo-Sanchez et al 2014. To aid these population recovery efforts, a better understanding of the ecological role of the brown bear and its impact on local biodiversity is crucial.…”