[MARMAM] New paper - SRW foraging

Els Vermeulen els.vermeulen at up.ac.za
Tue Dec 15 22:01:33 PST 2020

Dear all,

On behalf of all my co-authors, we are happy to share our most recent
publication on South Africa's southern right whales, entitled "Decadal
shift in foraging strategy of a migratory southern ocean predator".

Rapid anthropogenic climate 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 hypothesised 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 characterised 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 (δ13C) and nitrogen (δ15N)
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 between 1990s to 2010s.
Bayesian mixing model results suggest that during the 1990s, South African
SRWs foraged on prey with isotopic values similar to South Georgia krill.
In contrast, in the 2010s, we infer that South African SRWs foraged on prey
with isotopic values consistent with the waters of the Subtropical
Convergence, Polar Front and Marion Island. This shift could represent a
strategy to cope with changes in preferred prey or habitat. By linking
reproductive decline to a shift in foraging strategy for the first time in
SRWs, we show that altering foraging strategies may not be sufficient to
adapt to a changing ocean.

The article is available at
https://onlinelibrary.wiley.com/doi/epdf/10.1111/gcb.15465 or can be
requested via email to els.vermeulen at up.ac.za

Kind regards,

Dr Els Vermeulen - Research Manager
Mammal Research Institute Whale Unit
Department of Zoology and Entomology
University of Pretoria, South Africa

Office: Shop 11 Astoria Village, Main Road, Hermanus 7200
Cell: +27 (0)60 9714301


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