Estimated calving interval for the New Zealand southern right whale (Eubalaena australis)

ABSTRACT

Southern right whales (Eubalaena australis) were widespread in New Zealand waters before commercial whaling in the nineteenth century caused drastic declines in their abundance and distribution. Following the cessation of whaling, the population has been recovering and is now slowly recolonising its former range. Estimates of population demographics, including reproductive output, are essential for predicting the trajectory of this population. We gathered photo-identification data on female southern right whales during annual field trips to the Auckland Islands, the principal calving area in New Zealand waters. Forty-five calving intervals were observed between 2006 and 2013 (mean interval = 3.31 years, 95% CI = 3.06–3.57). Incorporating the effects of possible missed calving events produced a plausible range of mean calving intervals from 3.17 to 3.31 years. Our results suggest that the calving interval of New Zealand southern right whales is similar to that found in populations elsewhere.

KEYWORDS:

• Eubalaena australis
• calving interval
• reproductive rate
• Southern Right Whale
• New Zealand
• bootstrapping
• demography

Acknowledgements

The field data were collected with funding from the Foundation for Research, Science and Technology (FRST), the New Zealand Whale and Dolphin Trust, Otago Museum and the University of Otago Marine Science Department. We thank the Captain and crew of Evohe and Polaris II; Bill Dickson, Phil Heseltine, Steve Little, Evan Kenton, Sophie Fern and Tim Lever, for support to and from the Auckland Islands. From 2010 to 2013, research was conducted under Marine Mammal Research Permit Per/NO/2010/05 led by Dr Will Rayment and Professor Steve Dawson (University of Otago). Additional thanks to Simon Childerhouse who made data from between 2006 and 2009 available for this research (conducted under Marine Mammal Research Permit SO-25791-MAR and Animal Ethics Approval (University of Auckland): AEC/02/2005/R334), and to Glen Dunshea for assistance with the photo-ID data.

Disclosure statement

No potential conflict of interest was reported by the authors.