Patterns and trends in the diet of long‐finned pilot whales (Globicephala melas) in the northeast Atlantic

Abstract

There is little previous information on feeding habits of long‐finned pilot whales (Globicephala melas) in the northeast Atlantic. The present study analyzed stomach contents of pilot whales stranded in Portugal (n = 6), Galicia (northwest Spain) (n = 32), and Scotland (United Kingdom) (n = 10), from 1990 to 2011. These animals ranged from 213 to 555 cm in length (24 females, 19 males and 5 of unknown sex). The main prey identified were cephalopods of the families Octopodidae and Ommastrephidae, the former being numerically more important in Iberia (Portugal and Galicia) and the latter more important in Scotland, with Iberian whales also showing a more diverse diet. Multivariate analysis revealed evidence of geographical and seasonal variation in diet. Generalized Additive Modeling results indicated that more octopus (Eledone cirrhosa) were eaten in Iberia than in Scotland, more in the first half of the year, and more in larger whales. Numbers of ommastrephid squids in the stomach decreased over the study period and varied with season and whale length. This study confirms cephalopods as the main prey of pilot whales, as previously reported, although our results also suggest that, in the northeast Atlantic, ommastrephid squid are largely replaced as the main prey by octopods at lower latitudes.

An assessment of contaminant concentrations in toothed whale species of the NW Iberian Peninsula: Part II. Trace element concentrations

“…Pilot whale and striped dolphin exhibited the highest Cd concentrations in both liver and kidney (see Table 1). This result is in line with the similar feeding patterns of these species since both species primarily feed in offshore waters and have a high proportion of oceanic squid in their diet (Spitz et al, 2006(Spitz et al, , 2011Santos et al, 2013a;2013b). Squid are known to accumulate large amounts of cadmium and to be the major source of Cd in top predators (Bustamante et al, 1998;Lahaye et al, 2005).…”

An assessment of contaminant concentrations in toothed whale species of the NW Iberian Peninsula: Part I. Persistent organic pollutants

“…The five toothed whale species studied here have rather similar trophic levels in the NWIP, ranging from 4.3 to 5.3 (Méndez-Fernandez et al, 2012). However, stomach contents and stable isotope analyses revealed that these species feed on different prey types and forage in different habitats (Méndez-Fernandez et al, 2012Santos et al, 2007Santos et al, , 2013aSantos et al, , 2013bSantos et al, , 2013c). In addition, marine mammal organochlorine loads tend to increase with age during the juvenile stage of both genders, because the uptake of pollutants usually exceeds metabolism and excretion.…”

Long-finned pilot whale population diversity and structure in Atlantic waters assessed through biogeochemical and genetic markers

“…However, analysis of biogeochemical markers, such as stable isotopes (based solely in three animals, Abend & Smith 1995), parasites (IWC 1990) and morphometric differences (Bloch & Lastein 1993) suggested the segregation of pilot whale in the North Atlantic, particularly between the West and East Atlantic. Additionally, previous stomach contents analysis in the Northeast Atlantic reported the occurrence of dietary variation in pilot whales, based on geographical location, sex and length of the animal (Santos et al 2014). Considering the contrasting results previously found about the population structure of pilot whales, based on biogeochemical and genetic markers, the main objective of the present study is to combine ecological and genetic approaches to provide new insights regarding potential pilot whale stocks, in this oceanic basin.…”

“…In the NWIP, pilot whales seem to be present in neritic habitats and exhibit a preference for benthic prey species (such as curled octopus, Eledone cirrhosa) (e.g. Pierce et al 2010, Méndez-Fernandez et al 2012, Santos et al 2014). In the USA, pilot whales seem to perform seasonal inshore-offshore movements (e.g.…”

“…Off the UK and Faroe Islands, pilot whales exhibit an oceanic preference in terms of both habitat and prey species, since they mostly occur in areas off the continental shelf in both locations (Bloch et al 2003, MacLeod et al 2007, although sightings also occur from land in FI (Zachariassen et al 1993), and European flying squid (Todarodes sagitattus) and Gonatus sp. squids seem to be the most important prey species (Desportes & Mouritsen 1993, Santos et al 2014).…”