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New research using stable isotopes sheds light on how New Zealand’s diverse range of toothed whales and dolphins coexist

Locations for 21 cetacean species (indicated by shape and color) sampled in New Zealand between 2010 and 2021. Sample sizes for each species are indicated in parentheses. Bathymetry is depicted with dark shades of blue representing deeper waters. Credit: National Institute of Water and Atmospheric Research (NIWA) under a CC BY license, with permission from the original copyright of NIWA [33]

An international collaborative study involving researchers from Massey University, the University of Canterbury, NIWA and Flinders University has analyzed the isotope niche of 21 toothed whale species in New Zealand.

The results show that some species have a clear niche separation, while others overlap significantly.

The study, published this week in the international journal Biology, describes almost no overlap in niche space between sperm whales and gray beaked whales, both of which are species that forage in deep waters. However, for species foraging in coastal waters or the open ocean, competition can be fierce, with species in these habitats significantly overlapping in their foraging niche.

Research leader Dr. Katharina Peters of the University of Canterbury says: “Animals often go to great lengths to avoid competition and enable coexistence. When there is a large overlap in the foraging niche, it is possible that they avoid competition in other ways, e.g., foraging at different times of the day.”

New Zealand is home to an extraordinarily rich marine fauna, including 50% of the world’s whale and dolphin species. This rich abundance almost guarantees that some species will compete for their supper. Study co-author Professor Karen Stockin, who leads the Cetacean Ecology Research Group at Massey University, says: “We’ve been studying these animals for over 20 years, but there’s still so much we don’t understand about their food ecology. Stable isotopes collected of stranded animals [have] now provided us with the first insights into the trophic levels at which these complex mammals feed and compete.”

<img src="https://whatsnew2day.com/wp-content/uploads/2022/08/1660078587_393_New-research-using-stable-isotopes-sheds-light-on-how-New.jpg" alt="Nieuw onderzoek met behulp van stabiele isotopen werpt licht op hoe het gevarieerde aanbod van tandwalvissen en dolfijnen in Nieuw-Zeeland naast elkaar bestaat" title="Habitat zones in which exemplary odontocete species are grouped. Note that not all species included in the study are shown here. Credit: Katharina J. Peters et al, Biology (2022). DOI: 10.3390/biology11081179″/>

Habitat zones in which exemplary odontocete species are grouped. Note that not all species included in the study are shown here. Credit: Katharina J. Peters et al, Biology (2022). DOI: 10.3390/biology11081179

Whales and dolphins play a crucial role in maintaining and functioning of ecosystems; so knowledge of their foraging ecology is essential to understand how the ecosystem will adapt to future changes, such as ocean warming from fishing pressures causing changes in prey abundance and distribution.

“We need to know more about the mechanisms that allow these species to coexist in New Zealand’s waters,” said Dr. Peters. “This is especially important for species endemic to New Zealand, such as the Hector’s dolphin, but we don’t know how this will affect the species.”

Climate change predicts southerly shift of large whale species in New Zealand

More information:
Katharina J. Peters et al, Too Close for Comfort? Isotopic niche segregation in the New Zealand Odontocetes, Biology (2022). DOI: 10.3390/biology11081179

Provided by the University of Canterbury

Quote: New stable isotope research sheds light on how New Zealand’s diverse ranges of toothed whales and dolphins coexist (2022, 9 August), retrieved 9 August 2022 from https://phys.org/news/2022-08 -stable-isotopes-zealand -diverse-range.html

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