Graduation Year

2021

Document Type

Thesis

Degree

M.S.

Degree Name

Master of Science (M.S.)

Degree Granting Department

Biology (Integrative Biology)

Major Professor

Deby L. Cassill, Ph.D.

Committee Member

Michelle Green, Ph.D.

Committee Member

Timothy Henkel, Ph.D.

Keywords

mother-calf associations, maternal risk management, replacement fitness, replacement rate

Abstract

Cetacean maternal investments can be useful for conservation management as well as examining behaviors such as interspecific altruism in the humpback whale, Megaptera novaeangliae. Cetaceans are among the most threatened group of marine mammals. In the second chapter, maternal investments across ~90 species/subspecies of Cetacea were analyzed to aid in the understanding of recovery/replacement for conservation and management. Using Principal Components Analysis (PCA), a relative maternal-investment index for 41 cetacean species was built. The maternal-investment index was a composite of four maternal-investment variables, the duration of gestation, lactation, calving intervals, and the number of reproduction years per female per species. Furthermore, the number of years to produce two sexually mature offspring was calculated for 51 species. Maternal risk management, a general theory of reproduction, specifically for cetaceans offers extended explanations to the behavior of interspecific altruism in the humpback whale. Over 115 events of humpback whales interfering with predating killer whale, Orcinus orca, have been documented in a previous study, Pitman et al. 2017. Humpbacks elicit interspecific altruism in the majority of these events, seemingly aiding heterospecific from attacking killer whales. After statistical analysis, the theoretical framework of maternal risk management helps offer a new explanation of the drivers and evolution behind interspecific altruism in the humpback whale.

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