Isotopic and genetic evidence for culturally inherited site fidelity to feeding grounds in southern right whales (Eubalaena australis)

Abstract

Ocean warming will undoubtedly affect the migratory patterns of many marine species, but specific changes can be predicted only where behavioural mechanisms guiding migration are understood. Southern right whales show maternally inherited site fidelity to near-shore winter nursery grounds, but exactly where they feed in summer (collectively and individually) remains mysterious. They consume huge quantities of copepods and krill, and their reproductive rates respond to fluctuations in krill abundance linked to El Niño Southern Oscillation (ENSO). Here we show that genetic and isotopic signatures, analysed together, indicate maternally directed site fidelity to diverse summer feeding grounds for female right whales calving at Península Valdés, Argentina. Isotopic values from 131 skin samples span a broad range (-23.1 to -17.2‰ δ¹³C, 6.0 to 13.8‰ δ¹⁵N) and are more similar than expected among individuals sharing the same mitochondrial haplotype. This pattern indicates that calves learn summer feeding locations from their mothers, and that the timescale of culturally inherited site fidelity to feeding grounds is at least several generations. Such conservatism would be expected to limit the exploration of new feeding opportunities, and may explain why this population shows increased rates of reproductive failure in years following elevated sea-surface temperature anomalies off South Georgia, the richest known feeding ground for baleen whales in the South Atlantic.

Changes in distribution, relative abundance, and species composition of large whales around South Georgia from opportunistic sightings: 1992 to 2011

“…Southern right whales and humpback whales that breed off the coast of South America (Peninsula Valdés, Argentina, and Abrolhos Bank, Brazil, respectively) have been traced to South Georgia feeding grounds; however, these are limited cases representing only a handful of individual whales (Best et al 1993, Moore et al 1999, Rowntree et al 2001, Stevick et al 2006, Zerbini et al 2006, Engel & Martin 2009, Valenzuela et al 2009). This Minke whales recorded may also be of the species B. acutorostrata Kemp & Bennett (1932) general lack of knowledge stems from the inherent difficulty associated with studying cetaceans in the Antarctic; research in the area is quite costly, and sighting conditions are often unfavorable.…”

“…1) (Kemp & Bennett 1932). The South Georgia area is known to be an important feeding ground for large whales due to the high density of Antarctic krill Euphausia superba there (Reid et al 2000, Hedley et al 2001, Rowntree et al 2001, Atkinson et al 2004, Leaper et al 2006, Murphy et al 2007, Valenzuela et al 2009, International Whaling Commission 2010, 2011a. These waters are characterized by high biomass and productivity of phytoplankton, zooplankton, and vertebrate predators.…”

Short-term reactions and long-term responses of bottlenose dolphins (Tursiops truncatus) to remote biopsy sampling

“…The collection of small tissue samples from live cetaceans is essential to addressing questions in population genetics (Baker et al 1990;), phylogenetics (Caballero et al 2008), taxonomy (Rosenbaum et al 2002;Caballero et al 2007), foraging ecology (de Stephanis et al 2008;Valenzuela et al 2009), social structure (Duffield & Wells 1991;Kru¨tzen et al 2005), toxicology (Fossi et al 2000), reproductive success (Rosenbaum et al 2002), population dynamics (Oremus et al 2007) and aging of individuals (Herman et al 2009). Methods used for the collection of samples from wild cetaceans include 'skin swabbing' the animals using a velcro pad (Harlin et al 1999), collection of sloughed skin (Amos & Hoelzel 1990), faeces from the water column (Parsons et al 1999), use of a biopsy dart mounted on a pole (Bilgmann et al 2008), the deployment of a remote biopsy dart using a crossbow (Lambertsen 1987) or a modified veterinary capture rifle (Kru¨tzen et al 2002).…”

Groups of related belugas (Delphinapterus leucas) travel together during their seasonal migrations in and around Hudson Bay

“…Some 150 years later, these areas have never been fully re-colonized [69 -71]. Such migratory conservatism is also seen in southern right whales, where maternally directed site fidelity limits populations to two distinct feeding areas despite the availability of alternative feeding areas with abundant resources [72]. For belugas, the primary function of reaching shallow estuarine embayments is not fully understood.…”