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MEPS prepress abstract   -  DOI:

Reproductive capacity of an endangered and recovering population of humpback whales in the Southern Hemisphere

Guillaume Chero*, Roger Pradel, Solène Derville, Claire Bonneville, Olivier Gimenez, Claire Garrigue

*Corresponding author:

ABSTRACT: Estimating demographic parameters is essential to assess the recovery potential of severely depleted populations such as the baleen whales, which were decimated by commercial whaling of the past century. Due to its small size and low recovery rate, the Oceania humpback whale (Megaptera novaeangliae) population is classified as endangered by the IUCN. Nevertheless, an anomalously strong increase has recently been detected in the New Caledonia breeding population. To determine drivers of population growth, reproductive parameters were estimated for the first time for a humpback whale population of Oceania. Based on an extensive monitoring program (1995-2018), recapture histories were reconstructed for 607 females and incorporated in multi-event capture-recapture models. As the females’ ages were generally unknown (87%), two models with contrasting age scenarios were investigated. For females of unknown age, the “mature scenario” assumed maturity at the first encounter, while the “immature scenario” assumed immaturity within 7 years after the first encounter, unless the female was encountered breeding. These models respectively resulted in a calving interval of 1.49 years (95% CI: 1.21 – 2.08) or 2.83 years (95% CI: 2.28 – 3.56), and a calving rate of 0.67 or 0.35. The relatively high calving rate modelled by the mature model is consistent with high pregnancy rates recently observed in the migratory corridors of the Kermadec Islands, and on the feeding grounds of the Antarctic Peninsula. Therefore, our results suggest that the recovery of the New Caledonia humpback whale population from past exploitation may be partially driven by an increased reproductive capacity.