| Autor: |
Fossette S; Environmental Research Division NOAA Southwest Fisheries Science Center Monterey CA USA.; Present address: Department of Biodiversity, Conservation and Attractions 17 Dick Perry Av Kensington WA 6151 Australia., Abrahms B; Environmental Research Division NOAA Southwest Fisheries Science Center Monterey CA USA.; Department of Ecology and Evolutionary Biology University of California Santa Cruz Santa Cruz CA USA., Hazen EL; Environmental Research Division NOAA Southwest Fisheries Science Center Monterey CA USA.; Department of Ecology and Evolutionary Biology University of California Santa Cruz Santa Cruz CA USA., Bograd SJ; Environmental Research Division NOAA Southwest Fisheries Science Center Monterey CA USA., Zilliacus KM; Department of Ecology and Evolutionary Biology University of California Santa Cruz Santa Cruz CA USA., Calambokidis J; Cascadia Research Collective Olympia WA USA., Burrows JA; Division of Marine Science and Conservation Duke University Marine Laboratory Beaufort NC USA.; Moss Landing Marine Laboratories Moss Landing CA USA., Goldbogen JA; Department of Biology Hopkins Marine Station Stanford University Pacific Grove CA USA., Harvey JT; Moss Landing Marine Laboratories Moss Landing CA USA., Marinovic B; Department of Ecology and Evolutionary Biology University of California Santa Cruz Santa Cruz CA USA., Tershy B; Department of Ecology and Evolutionary Biology University of California Santa Cruz Santa Cruz CA USA., Croll DA; Department of Ecology and Evolutionary Biology University of California Santa Cruz Santa Cruz CA USA. |
| Abstrakt: |
Resource partitioning is an important process driving habitat use and foraging strategies in sympatric species that potentially compete. Differences in foraging behavior are hypothesized to contribute to species coexistence by facilitating resource partitioning, but little is known on the multiple mechanisms for partitioning that may occur simultaneously. Studies are further limited in the marine environment, where the spatial and temporal distribution of resources is highly dynamic and subsequently difficult to quantify. We investigated potential pathways by which foraging behavior may facilitate resource partitioning in two of the largest co-occurring and closely related species on Earth, blue ( Balaenoptera musculus ) and humpback ( Megaptera novaeangliae ) whales. We integrated multiple long-term datasets (line-transect surveys, whale-watching records, net sampling, stable isotope analysis, and remote-sensing of oceanographic parameters) to compare the diet, phenology, and distribution of the two species during their foraging periods in the highly productive waters of Monterey Bay, California, USA within the California Current Ecosystem. Our long-term study reveals that blue and humpback whales likely facilitate sympatry by partitioning their foraging along three axes: trophic, temporal, and spatial. Blue whales were specialists foraging on krill, predictably targeting a seasonal peak in krill abundance, were present in the bay for an average of 4.7 months, and were spatially restricted at the continental shelf break. In contrast, humpback whales were generalists apparently feeding on a mixed diet of krill and fishes depending on relative abundances, were present in the bay for a more extended period (average of 6.6 months), and had a broader spatial distribution at the shelf break and inshore. Ultimately, competition for common resources can lead to behavioral, morphological, and physiological character displacement between sympatric species. Understanding the mechanisms for species coexistence is both fundamental to maintaining biodiverse ecosystems, and provides insight into the evolutionary drivers of morphological differences in closely related species. |
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