Honors Theses and Capstones

Date of Award

Spring 2024

Project Type

Senior Honors Thesis

College or School

COLSA

Department

Department of Biology

Program or Major

Marine, Estuarine, and Freshwater Biology

Degree Name

Bachelor of Science

First Advisor

Michelle Fournet

Abstract

Animal density can define factors such as mating success, food acquisition, and communication. Inferring animal density from vocal rates is an important tool for estimating abundance and space use in difficult-to-study species like marine mammals and requires an understanding of the relationship between social context and calling rates. The goal of this project was to investigate the relationship between animal density and call rate in Southeast Alaskan humpback whales (Megaptera novaeangliae). Passive acoustic monitoring data were collected along with visual observations gathered near Frederick Sound and Stephen’s Passage, Southeast Alaska, over two summers (2019, 2022). Observers watched whales from a small boat to count the whales and place them into distance bins based on their distance from the boat, allowing for density (whales/km2) to be calculated. There were 98 total 10-minute surveys that took place over 34 days. The range of observations was 1 to 53 whales per survey. Call rate and density exhibited a negative logarithmic relationship; for every one unit increase in density call rates decreased by 42.5% (95% CI 31%-59%). Understanding the changes in humpback whale call rates associated with density has potential to improve monitoring practices and conservation efforts.

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