Long-term monitoring of southern right whale feeding behavior indicates that Península Valdés is more than a calving ground

Abstract

Península Valdés, Patagonia, Argentina, is recognized as a calving ground for the southern right whale (SRW, Eubalaena australis) population from the southwestern Atlantic Ocean. Previous studies have reported that SRWs feed during their calving season, but little is known about their foraging ecology in this area. Here, we collected photo data of SRWs at Península Valdés from 2007 to 2019 to monitor and investigate the SRW feeding frequency and to know whether calves also feed on zooplankton (i.e., the diet composed of both milk and solid food). In addition, we systematically reviewed studies on the composition and abundance of zooplankton to assess the available prey for SRWs in the area. Finally, we examined satellite-derived chlorophyll-a (chl-a) to study if the chl-a variability shows any relationship with SRW feeding. Observations show that at Península Valdés, SRWs feed at and below the surface, primarily on calanoid copepods. We also found evidence that SRWs feed near-bottom. In addition, we report calves feeding at surface including the first-ever photographs documentation. Whales feed mainly during austral spring, with a higher mean frequency in November. A time lag of 1 month was found between highest chl-a levels and the highest number of feeding events observed. Over the 12-year study period, we observed that whales were foraging yearly, which indicates that feeding in this calving area is more frequent than prior studies suggested. These data reveal the importance of the waters off Península Valdés as a multi-use habitat for SRW.