Oregon State University



Event Details

Logan Pallin, MSc Defense

Temporal Variation in the Population Demographics of Humpback Whales (Megaptera novaeangliae) along the Western Antarctic Peninsula (WAP): Links to a Changing Ecosystem

Friday, May 26, 2017 10:00 AM - 11:00 AM

Abstract:  Humpback whale populations in Antarctica are recovering after intense commercial whaling in the 20th century.  Along the Western Antarctic Peninsula (WAP) this recovery is occurring in an environment that is experiencing the fastest warming of any region on the planet.  To begin to understand the dynamics of this recovery under such dramatic climate change, we are studying the demography of these whales. To date, we have collected 583 biopsy samples from 239 individual males and 268 individual females during the austral feeding season from 2010, 2013-2016. The overall sex ratio of our sample population is 0.89 M:F, supporting early observations that sexes mix randomly on the feeding grounds, however, we did document a significant seasonal shift towards females along the WAP into the fall. We believe that this shift represents a tendency for pregnant female humpback whales to depart last from the feeding grounds. Additionally, we examined progesterone levels of females to determine pregnancy; to our knowledge, this is the first non-lethal estimation of pregnancy rates in Antarctic whales. We verified our results with assays of humpbacks of known pregnancy status (n=29) from the northwestern Atlantic. Mean progesterone levels for pregnant humpback whales from the WAP was 250 ng progesterone/g blubber (n = 155). The mean value for non-pregnant females was 2.10 ng progesterone/g blubber (n = 89). We detected a significant increase in apparent pregnancy rate (58% to 72%) from summer to autumn across all years. Annual pregnancy rates varied significantly across all years, from 36% in 2010 to 86% in 2014. Some female whales in this population engaged in a post-partum ovulation followed by conception (annual pregnancy); on average, more than half (52%) of female whales accompanied by calves were pregnant.  These are some of the first quantitative observations of the demography of recovering humpback whale populations in the Antarctic and provides a critical reference point as the Antarctic climate continues to change.

Off Campus
Hatfield Marine Science Center
Guin Library Seminar Room
2030 SE Marine Science Dr
Minda Stiles
1 541 867 0202
minda.stiles at oregonstate.edu
Marine Mammal Institute
This event appears on the following calendars: