Assessing body condition in baleen whales

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Overview

Little is known about the link between body condition and reproduction in large whales, which makes it difficult to monitor the health of whale populations. Further, methods to assess body condition in free-living whales are scarce, or require lethal techniques (i.e. scientific whaling) not suitable for vulnerable populations. Thus there is a need to develop and test new methods to measure body condition in large whales to assess the health of baleen whale populations globally.

A group of adult humpback whales

A group of humpback whales in Exmouth Gulf, WA, photographed from a UAV. Image obtained under WA DPaW research permit. 

MUCRU researcher Dr. Fredrik Christiansen, in collaboration with Prof. Lars Bejder, is developing a research project to improve our understanding of baleen whale body condition and reproduction by using novel non-invasive technology to measure body condition in free-living whales. The study involves using unmanned aerial vehicles (UAVs) to measure intra-seasonal variations in body condition of baleen whales and its influence on calf production and growth. This is a novel, non-invasive technique, for which the only current alternative is lethal sampling (i.e. scientific whaling).

Baleen whales play an important role as top-predators in the marine ecosystem and a better understanding of their body condition and bioenergetics is crucial to better understand the potential impact that environmental changes, e.g. global warming, will have on baleen whale populations. This research project focuses on a number of baleen whales species, including humpback (Megaptera novaeangliae), right (Eubalaena australis) and minke whales (Balaenoptera bonaerensis), which can all be found around Australia.

Specifically, the project aims to improve our understanding of:

  • The health of the baleen whale populations.
  • The relationship between female body condition and the body condition of their offspring.
  • The use of UAV technology as a non-invasive tool to measure body condition in free-living whales.
A UAV is launched from a small research vessel and piloted into position above southern right whales in order to collect photographs for subsequent morphometric analyses. Image obtained under WA DPaW research permit. Copyright: Murdoch University Cetacean Research Unit.

A UAV is launched from a small research vessel and piloted into position above southern right whales in order to collect photographs for subsequent morphometric analyses. Image obtained under WA DPaW research permit. Copyright: Murdoch University Cetacean Research Unit.

Approach

This project utilizes aerial photographs of baleen whales to assess body condition in a non-invasive manner. UAVs are used to fly above and photograph free-swimming whales, with a number of morphometric measurements (e.g. length and width) subsequently derived from these photographs. The photographs are scaled (i.e. pixels are converted to cm in the photographs) either by knowing the altitude of the UAV (using trigonometry) or by photographing the whales together with an object of known size (i.e. the research vessel). The surface area of the whale is then calculated and used as a proxy for body condition. Whales are divided into different maturity classes (e.g. calves, juveniles and adults) based on their size (length). By investigating intra-seasonal changes in body condition of different maturity classes, the relative energetic costs that different maturity classes face during their reproductive cycle can be estimated. Further, annual variations in body condition can be related to prey productivity in the polar regions (the main feeding grounds of baleen whales), to determine the relationship between primary productivity and baleen whale health.

Morphometric measurements are derived from photographs taken by UAV. Image obtained under WA DPaW research permit.

Morphometric measurements are derived from photographs taken by UAV. Image obtained under WA DPaW research permit.

Component sub-projects

In 2015, the first field season of this project was conducted on humpback whales on their breeding grounds in Exmouth Gulf, Western Australia. This was followed by a shorter field study in early 2016 on humpback whales in the Antarctic peninsula, an important feeding ground. In the austral winter of 2016, data collection is being carried out on Southern right whales on their breeding grounds at the Head of Bight, South Australia. More information on these sub-projects, including collaborators and funding sources, is available through the following pages:

Publications

  • Christiansen, F., Dujon, A.M., Sprogis, K.R., Arnould, J.P.Y. and Bejder, L. (2016). Non-invasive Unmanned Aerial Vehicle provides estimates of the energetic cost of reproduction in humpback whales. Ecosphere. Doi: 10.1002/ecs2.1468

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