The Cantabrian capercaillie: A population on the edge

Area of Science:

• Conservation Biology
• Wildlife Ecology
• Population Genetics

Background:

• The capercaillie (Tetrao urogallus), the world's largest grouse, is a circumboreal forest species with critically endangered populations in Spain.
• Two Spanish populations exist: Cantabrian (west) and Pyrenean (east), both experiencing severe declines, particularly the Cantabrian population.

Purpose of the Study:

• To estimate the current population size of the Cantabrian capercaillie using spatial capture-recapture (SCR) modeling and non-invasive DNA.
• To assess the population status and trajectory over 42 years (1978-2019) using integrated population models.
• To provide essential demographic data for developing effective conservation and management plans.

Main Methods:

• Spatial capture-recapture (SCR) modeling with non-invasive DNA samples for population size estimation.
• Integrated population model incorporating Dail-Madsen, multistate capture-recapture (survival), and Poisson regression (productivity) for population trajectory analysis.
• Analysis of data from 196 leks on the Southern slope of the Cantabrian Mountains over 42 years.

Main Results:

• Estimated 2019 population size: 191 individuals (60 females, 131 males).
• Estimated 83% shrinkage in population range since the 1970s.
• 2019 population size is approximately 10% of the 1978 estimate; annual survival (0.707) and recruitment (0.233) are insufficient for population stability.

Conclusions:

• The Cantabrian capercaillie population is critically endangered, with severe range contraction and low numbers.
• Current demographic parameters (survival and recruitment) are inadequate for population maintenance.
• Urgent conservation actions are needed to improve recruitment and survival, manage forest habitats, and assess future genetic viability.