Humpback whale body condition on a breeding ground

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Overview

In August and September 2015, MUCRU researchers carried out their first successful field study towards the research project: Assessing body condition in baleen whales. This field study focussed on measuring the body condition of humpback whales (Megaptera novaeangliae) in the Exmouth Gulf, Western Australia. Exmouth Gulf provides a sheltered resting area for humpback whale female and calf pairs belonging to the Western Australian humpback whale population during their annual southern migration from waters off the north-west coast of Australia. The study was funded by Murdoch University and carried out in collaboration with Victorian UAS Training.

Humpback whale mother and calf pair resting in Exmouth Gulf, WA

Humpback whale mother and calf pair resting in Exmouth Gulf, WA

Approach

Within Exmouth Gulf, females and calves are generally found >3km from shore. Consequently, aerial photographs of free-swimming whales were collected from a small (<50cm) waterproof “Splashdrone” unmanned aerial vehicle (UAV) deployed from a small research boat. The UAV, equipped with both a still camera and a GoPro, was flown at heights between 20 and 50m above surfacing whales and recorded aerial images and videos of the animals. A live feed video system, connecting the GoPro camera of the UAV to a monitor on board the research vessel, was used to position the UAV right above the whales. From the photos, the length and width of the whales was measured, which was converted to a measure of relative body condition. By measuring the body condition of different whales throughout the breeding season, we were able to assess intra-seasonal changes in body condition of different age classes of whales (calves, immature, mature and lactating whales), to better understand the energetic costs that different age classes face during the breeding season.

Examples of humpback whale aerial photographs used to measure body condition. Images obtained under WA DPaW research permit.

Examples of humpback whale aerial photographs used to measure body condition. Images obtained under WA DPaW research permit.

Results

We found that mature and lactating whales decreased their body condition through the breeding season, whilst immature whales and calves did not change their condition. Furthermore, we found that the relative body condition of calves was positively correlated to the relative condition of their mothers. The results of this study were presented at the Australasian Wildlife Management Society conference in Perth in November 2015, and also the Biennial Conference on the Biology of Marine Mammals in San Francisco in December 2015.

Implications

Our findings provide important information on the health of the Western Australian humpback whale population visiting Exmouth Gulf, and how this relates to female reproduction success. Such baseline information is crucial for the development of management frameworks to assess the impacts of anthropogenic disturbance (ship noise, whale-watching, oil and gas exploration etc.) on humpback whales in the region, since behavioural responses to such disturbance is likely to express itself in the body condition of the animals. This field study also served as a valuable learning experience from which to fine-tune methods for future use of UAV systems to assess body condition of baleen whales.

Photograph of humpback whale mother and calf pair in Exmouth Gulf, WA, captured by a small UAV. Image obtained under WA DPaW research permit.

Photograph of humpback whale mother and calf pair in Exmouth Gulf, WA, captured by a small UAV. Image obtained under WA DPaW research permit.

Permits

This research project was carried out under a research permit from the WA Department of Parks and Wildlife (DPaW), and with approval from the Murdoch University Animal Ethics Committee. The UAV was operated under a UAV Operator Certificate and a Remotely Piloted Aircraft System License in accordance with Australian Civil Aviation Safety Authority regulations.

Collaborators

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 7:10:e01468. doi:10.1002/ecs2.1468.

Conference presentations

  • Measuring body condition of humpback whales and evaluating acoustic exposure of an UAV on target animals. Invited workshop talk at the 21st biennial conference on the biology of marine mammals. San Francisco, USA. 13 Dec 2015.
  • Using Unmanned Aerial Vehicles to measure body condition of humpback whales in Exmouth Gulf, WA. Invited talk at the Annual Australasian Wildlife Management Society Conference. Perth, WA. 23-26 Nov 2015.

Blogs

Media output

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