Effects of a morbillivirus epizootic on long-finned pilot whales Globicephala melas in Spanish Mediterranean waters

Long-finned pilot whales Globicephala melas are a commonly encountered species in the Mediterranean Sea. In 2006−2007, an outbreak of the dolphin morbillivirus in the Western Mediterranean resulted in increased mortality of this species. The aim of this study was to determine whether survival rates differed between clusters of Spanish Medi terranean pilot whales, and how the epizootic in fluenced these survival rates. Photo-identification surveys were conducted between 1992 and 2009. Association indices were used to define clusters of individuals that associate with each other more frequently than with others. Based on a Cormack-JollySeber survival rate model, apparent survival rate estimates varied from 0.821 to 0.995 over 11 clusters for the 1992−2009 period. When the effect of the morbillivirus outbreak was modeled, 3 clusters with distinctly lower survival rates from previous models presented lower estimates after the outbreak (survival rate dropped from 0.919 [95% CI: 0.854−0.956] to 0.547 [95% CI: 0.185−0.866]), suggesting a negative influence of the epizootic or other unknown additive factors on certain clusters. This information is critical for the conservation of long-finned pilot whales, since they are listed as ‘data deficient’ in the Mediterranean Sea by the IUCN and as ‘vulnerable’ in the Spanish National Catalogue of Endangered Species.