Too Close for Comfort? Isotopic Niche Segregation in New Zealand's Odontocetes

Katharina J Peters; Sarah J Bury; Bethany Hinton; Emma L Betty; Déborah Casano-Bally; Guido J Parra; Karen A Stockin

doi:10.3390/biology11081179

Too Close for Comfort? Isotopic Niche Segregation in New Zealand's Odontocetes

Biology (Basel). 2022 Aug 5;11(8):1179. doi: 10.3390/biology11081179.

Authors

Katharina J Peters^{1

2

3}, Sarah J Bury⁴, Bethany Hinton¹, Emma L Betty¹, Déborah Casano-Bally¹, Guido J Parra⁵, Karen A Stockin¹

Affiliations

¹ Cetacean Ecology Research Group, School of Natural Sciences, Massey University, Auckland 0745, New Zealand.
² School of Earth and Environment, University of Canterbury, Christchurch 8041, New Zealand.
³ Evolutionary Genetics Group, Department of Anthropology, University of Zurich, 8057 Zurich, Switzerland.
⁴ National Institute of Water and Atmospheric Research, Wellington 6021, New Zealand.
⁵ Cetacean Ecology, Behaviour and Evolution Lab, College of Science and Engineering, Flinders University, Adelaide 5001, Australia.

Abstract

Species occurring in sympatry and relying on similar and limited resources may partition resource use to avoid overlap and interspecific competition. Aotearoa, New Zealand hosts an extraordinarily rich marine megafauna, including 50% of the world's cetacean species. In this study, we used carbon and nitrogen stable isotopes as ecological tracers to investigate isotopic niche overlap between 21 odontocete (toothed whale) species inhabiting neritic, mesopelagic, and bathypelagic waters. Results showed a clear niche separation for the bathypelagic Gray's beaked whales (Mesoplodon grayi) and sperm whales (Physeter macrocephalus), but high isotopic niche overlap and potential interspecific competition for neritic and mesopelagic species. For these species, competition could be reduced via temporal or finer-scale spatial segregation or differences in foraging behaviour. This study represents the first insights into the coexistence of odontocetes in a biodiverse hotspot. The data presented here provide a critical baseline to a system already ongoing ecosystem change via ocean warming and subsequent effects on prey abundance and distributions.

Keywords: SGD14; carbon; diet; dolphins; feeding ecology; nitrogen; stable isotopes; trophic relationships.

Grants and funding

Funding for this project was provided by the PADI Foundation (K.J.P.) and Massey University Research Fund (K.A.S.). During part of this study, K.J.P. was supported by an Australia Awards Endeavour Research Fellowship, and a Postdoc Grant from the University of Zurich. K.A.S. was supported by a Royal Society Te Aparangi Rutherford Discovery Fellowship (2019–2024). B.H. was supported by a Massey University Doctoral Scholarship and a Wildbase Trust research grant.