1
|
van den Berg GL, Vermeulen E, Valenzuela LO, Bérubé M, Ganswindt A, Gröcke DR, Hall G, Hulva P, Neveceralova P, Palsbøll PJ, Carroll EL. Decadal shift in foraging strategy of a migratory southern ocean predator. Glob Chang Biol 2020; 27:1052-1067. [PMID: 33319502 DOI: 10.1111/gcb.15465] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 11/17/2020] [Accepted: 11/18/2020] [Indexed: 06/12/2023]
Abstract
Rapid anthropogenic environmental change is expected to impact a host of ecological parameters in Southern Ocean ecosystems. Of critical concern are the consequences of these changes on the range of species that show fidelity to migratory destinations, as philopatry is hypothesized to help or hinder adaptation to climate change depending on the circumstances. Many baleen whales show philopatry to feeding grounds and are also capital breeders that meet migratory and reproductive costs through seasonal energy intake. Southern right whales (Eubalaena australis, SRWs) are capital breeders that have a strong relationship between reproductive output and foraging success. The population dynamics of South Africa's population of SRWs are characterized by two distinct periods: the 1990s, a period of high calving rates; and the late 2010s, a period associated with lowered calving rates. Here we use analyses of stable carbon (δ13 C) and nitrogen (δ15 N) isotope values from SRW biopsy samples (n = 122) collected during these two distinct periods to investigate foraging ecology of the South African population of SRWs over a time period coincident with the demographic shift. We show that South African SRWs underwent a dramatic northward shift, and diversification, in foraging strategy from 1990s to 2010s. Bayesian mixing model results suggest that during the 1990s, South African SRWs foraged on prey isotopically similar to South Georgia/Islas Georgias del Sur krill. In contrast, in the 2010s, South African SRWs foraged on prey isotopically consistent with the waters of the Subtropical Convergence, Polar Front and Marion Island. We hypothesize that this shift represents a response to changes in preferred habitat or prey, for example, the decrease in abundance and southward range contraction of Antarctic krill. By linking reproductive decline to changing foraging strategies for the first time in SRWs, we show that altering foraging strategies may not be sufficient to adapt to a changing ocean.
Collapse
Affiliation(s)
- Gideon L van den Berg
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Pretoria, South Africa
| | - Els Vermeulen
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Pretoria, South Africa
| | - Luciano O Valenzuela
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Laboratorio de Ecología Evolutiva Humana (LEEH, Facultad de Ciencias Sociales, Unidad de Enseñanza Universitaria Quequén, UNCPBA, Buenos Aires, Argentina
- School of Biological Sciences, University of Utah, Salt Lake City, UT, USA
- Instituto de Conservación de Ballenas, Buenos Aires, Argentina
| | - Martine Bérubé
- Marine Evolution and Conservation Group, Groningen Institute of Evolutionary Life Sciences, University of Groningen, Groningen, The Netherlands
- Centre for Coastal Studies, Provincetown, MA, USA
| | - Andre Ganswindt
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Pretoria, South Africa
| | - Darren R Gröcke
- Stable Isotope Biogeochemistry Laboratory (SIBL), Department of Earth Sciences, Durham University, Durham, UK
| | - Grant Hall
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Pretoria, South Africa
| | - Pavel Hulva
- Department of Zoology, Faculty of Science, Charles University, Prague, Czech Republic
- Department of Biology and Ecology, Faculty of Science, University of Ostrava, Ostrava, Czech Republic
| | - Petra Neveceralova
- Department of Zoology, Faculty of Science, Charles University, Prague, Czech Republic
- Ivanhoe Sea Safaris, Gansbaai, South Africa
- Dyer Island Conservation Trust, Great White House, Kleinbaai, South Africa
| | - Per J Palsbøll
- Marine Evolution and Conservation Group, Groningen Institute of Evolutionary Life Sciences, University of Groningen, Groningen, The Netherlands
- Centre for Coastal Studies, Provincetown, MA, USA
| | - Emma L Carroll
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
| |
Collapse
|