Published December 16, 2022 | Version v1
Dataset Open

Humpback pregnancy rates and environmental variation: Supporting datasets

  • 1. University of California, Santa Cruz

Description

The krill surplus hypothesis of unlimited prey resources available for Antarctic predators due to commercial whaling in the 20th century has remained largely untested since the 1970s. Rapid warming of the Western Antarctic Peninsula (WAP) over the past 50 years has resulted in decreased seasonal ice cover and a reduction of krill. The latter is being exacerbated by a commercial krill fishery in the region. Despite this, humpback whale populations have increased but may be at a threshold for growth based on these human-induced changes. Understanding how climate-mediated variation in prey availability influences humpback whale population dynamics is critical for focused management and conservation actions. Using an eight-year dataset (2013–2020), we show that inter-annual humpback whale pregnancy rates, as determined from skin-blubber biopsy samples (n = 616), are positively correlated with krill availability and fluctuations in ice cover in the previous year. Pregnancy rates showed significant inter-annual variability, between 29% and 86%. Our results indicate that krill availability is in fact limiting and affecting reproductive rates, in contrast to the krill surplus hypothesis. This suggests that this population of humpback whales may be at a threshold for population growth due to prey limitations. As a result, continued warming and increased fishing along the WAP, which continue to reduce krill stocks, will likely impact this humpback whale population and other krill predators in the region. Humpback whales are sentinel species of ecosystem health, and changes in pregnancy rates can provide quantifiable signals of the impact of environmental change at the population level. Our findings must be considered paramount in developing new and more restrictive conservation and management plans for the Antarctic marine ecosystem and minimizing the negative impacts of human activities in the region.

Notes

Please see the README document ("README-HumpbackPregnancyEnvironmentalChange.rmd") and the accompanying published article: L.J. Pallin, N.M. Kellar, D. Steel, N. Botero-Acosta, C.S. Baker, J. A. Conroy, D.P. Costa,  C.M. Johnson, D.W. Johnston, R. C. Nichols, D.P. Nowacek, A.J. Read, O. Savenko11,12, O.M. Schofield, S.E. Stammerjohn, D.K. Steinberg, A.S. Friedlaender. A surplus no more? Variation in krill availability impacts reproductive rates of Antarctic baleen whales. Global Change Biology. 

Funding provided by: Office of Polar Programs
Crossref Funder Registry ID: http://dx.doi.org/10.13039/100000087
Award Number: 1643877

Funding provided by: National Science Foundation
Crossref Funder Registry ID: http://dx.doi.org/10.13039/100000001
Award Number: Graduate Research Fellowship Program DGE1339067

Funding provided by: National Geographic Society
Crossref Funder Registry ID: http://dx.doi.org/10.13039/100006363
Award Number: NGS-909906R-21

Funding provided by: Marine Mammal Commission
Crossref Funder Registry ID: http://dx.doi.org/10.13039/100005199
Award Number:

Funding provided by: Palmer Long-term Ecological Research Program*
Crossref Funder Registry ID:
Award Number: 1440435

Funding provided by: Palmer Long-term Ecological Research Program*
Crossref Funder Registry ID:
Award Number: 2026045

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README-HumpbackPregnancyEnvironmentalChange.md