Paper SC/60/BRG13 Isotopic and genetic evidence for site fidelity to feeding grounds in southern right whales (Eubalaena australis).

VALENZUELA, LUCIANO O; SIRONI, MARIANO; ROWNTREE, VICTORIA; SEGER, JON

Encuentro; International Whaling Commission Scientific Committeee; 2008

Ocean warming will certainly 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 go to feed in summer 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 data, 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 time scale 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 might explain why this population shows increased rates of reproductive failure in years following sea surface temperature anomalies off South Georgia, the richest known feeding ground for baleen whales in the South Atlantic.