Mortality Causes in Captive Cantabrian capercaillie (Tetrao urogallus cantabricus) in Spain

Abstract

The Cantabrian capercaillie (Tetrao urogallus cantabricus) is one of the most severely threatened subspecies of capercaillie. Its current population range is restricted to a small area of the Cantabrian Mountains (northwestern Spain), with only around 200 individuals remaining. As part of the national strategy for the conservation of the subspecies, the Cantabrian capercaillie Captive Breeding Center of Sobrescobio opened in 2009. Here, we use the information provided by the necropsies performed in this facility on 29 individuals (11 males, 13 females and 5 undetermined; 16 chicks and 13 adults) in order to describe the main mortality causes of captive-bred Cantabrian capercaillies. After necropsy, tissue samples were taken for evaluation using standard methods in histology and microbiology. The majority of the captive animals (18/29, 62.07%) died due to infectious diseases, mainly due to Escherichia coli, Clostridium perfringens, or Aspergillus fumigatus infection. The remaining 11 animals died due to stress-related processes (i.e., rupture of the heart apex and cardiomyopathy or neurogenic shock) (8/29, 27.59%), duodenal obstruction and coelomitis (1/29, 3.45%), perforation of the proventriculus and heart with a briar branch (1/29, 3.45%) or euthanasia due to a valgus leg deformity that prevented proper animal welfare (1/29, 3.45%). Young animals (i.e., younger than 2 months) died mainly due to infectious diseases (14/16, 87.5%), while stress-related causes were responsible for most adult deaths (7/13, 53.85%). We additionally report that two free-ranging adult males died due to exertional myopathy. This study provides relevant information for reducing mortality in captive capercaillies and improving both living conditions in captivity and the adaptation of these animals to the wild.

First detection of herpesvirus and hemosporidians in the endangered Pyrenean Capercaillie (Tetrao urogallus aquitanicus)

“…The negative results for APEC, Salmonella spp. and C. jejuni were not completely unexpected, once these pathogens have been previously described in other wild free-ranging galliforms, although generally at low prevalences 11 , 50 – 52 , and not necessarily considered part of their normal microbiota 51 . In capercaillies, the presence of E. coli was confirmed in captive and free-ranging birds of Germany, with higher occurrence in the captive individuals 50 .…”

“…This could also be the case for Pyrenean capercaillies. Recently, García-Rodríguez et al 11 reported several cases of colibacillosis (caused by E. coli ) in captive Cantabrian Capercaillies (i.e., isolated E. coli infections in nine chicks and one adult, and a co-infection by E. coli , Clostridium perfringens , and Enterococcus gallinarum in one chick). The potential impact of this bacterium in free-ranging Pyrenean capercaillie chicks is unknown.…”

“…in two Western Capercaillies from Austria 10 , and Escherichia coli , Clostridium perfringens , Enterococcus spp. or Aspergillus fumigatus in Cantabrian Capercaillie ( T. u. cantabricus ) from a breeding center in Spain 11 .…”

Sound amplitude (dB) of male Western Capercaillie Tetrao urogallus

“…In recent years, passive autonomous acoustic monitoring has begun to be employed to study this bird's behaviour, status and population dynamics, as well as to improve its conservation management (Abrahams & Denny 2018, Abrahams 2019. Western Capercaillie populations in Central and Western Europe have declined during the twentieth century and the viability of its populations is threatened in many areas due to threats such as habitat destruction and predation (Jahren et al 2016, Gil et al 2020, García-Rodríguez et al 2023. It is globally ranked as of Least Concern (BirdLife International 2016, BirdLife International 2024) but as Endangered in Catalonia (Decret 172/2022).…”