Humpback pregnancy rates and environmental variation: Supporting datasets

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 signi..., Biopsy collection
We collected skin and blubber samples from female humpback whales during the 2013–2020 austral summers (December-March). This was done in the nearshore waters of the Western Antarctic Peninsula (WAP) using standard biopsy techniques (Fig. 1). We used a crossbow to project modified bolts and 40mm stainless steel biopsy tips (CetaDart) to obtain samples from a distance of 10–30 meters, targeting the area of the body below the dorsal fin.   Samples were collected opportunistically when whales were encountered during prey or visual surveys conducted within ~10 nautical miles of scientific research stations (i.e., Palmer Station, Anvers Island, USA, or Akademik Vernadsky Station, Galindez Island, Ukraine). Dedicated research cruises or platforms of opportunity, including ecotour vessels, were also used. Dependent calves were not sampled during seasons 2013–2019, but all age and sex classes of humpback whales were sampled during 2020. Because of this change in protocol, samp..., 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.Â