Using unmanned aerial vehicles to measure body condition of humpback and minke whales in Antarctica
*Fredrik Christiansen1 and Lars Bejder1
1Murdoch University, Australia
Background Date: 21 January 2016
· Baleen whales around the world face a number of anthropogenic threats (e.g. ship strikes, net entanglements, anthropogenic noise, human induced climate change etc.), which might impede the rate of recovery from last centuries whaling.
· Knowledge of the body condition of baleen whales, and its relationship to reproduciton and survival, is crucial to understand non-lethal anthropogenic impacts (e.g. anthropogenic noise).
· Non-invasive methods to assess body condition (health) of humpback whales and minke whales is lacking.
· We propose to use Unmanned Aerial Vehicles (UAVs) to measure seasonal variations in body condition of humpback whales and minke whales and its influence on calf growth and body condition in Antarctica.
Methods:
A small (<50cm diameter, <3kg) waterproof multi-rotor (a Splashdrone quadcopter) unmanned aerial vehicles (UAVs) will be used to take aerial photographs of humpback whales and minke whales (Figure 1) off the Antarctic Peninsula (including Flandres, Andvord, Wilhelmina and Charlotte Bay), during the Southern hemisphere summer feeding season. We aim to photograph all age and maturity classes of whales. Further, one of our aims to is photograph females with calves, so that the relative body condition of the females can be related to that of their calf. The UAV will be deployed from a smaller research vessel (5-10m), which will be positioned 50-300m from the targeted whale during the launch. The UAV will be initially flown above the whales at heights between 5 and 50 meters. Once above a whale, the UAV will take vertical photographs of the animal. This will allow photogrammetry to be used to measure the size (length and width) of the whales from the photographs (Miller et al. 2012) (Figure 1). A live video link, providing the UAV operator with live feed from the GoPro camera, will be used to correct the position of the UAV above the whale and also confirm that photos of adequate quality had been obtained. The UAV will then be flown up to an altitude of 80 to 120m, while the research vessel will move in closer to the whale (25-50m distance from the animal) until both the whale and the boat is visible in the same photo. The size of the research vessel will then use to scale the photograph. Once the scale photo has been obtained, the UAV will return to the research boat and land safely in the water.
In August and September 2015, we carried out a successful pilot study in Exmouth Gulf, WA, using the same approach to measure the body condition of humpback whales. 200 individual whales (including 49 pairs of mother and calves) were successfully measured under a Western Australian Department of Parks and Wildlife permit and Murdoch University Ethics permit. The whales measured did not show any visible response to the UAV, indicating that this method caused minimal disturbance to the animals. Preliminary results from this study were presented at a UAV workshop at the Biennial Conference on the Biology of Marine Mammals in San Francisco in December 2015.
Having measured the body condition of humpback whales in their breeding/resting grounds (i.e. Exmouth Bay), the proposed research project will complement this data set by adding information about humpback whales body condition from the feeding grounds, to cover the migratory cycle of these animals.
Analytical Framework
The length and width of the measured whales, obtained from the UAV photos (Figure 1), will be converted to a measure of relative body condition. More specifically, we will use the surface area of the whale as a proxy for body condition and estimate the relative body condition of females and calves while accounting for their length. By comparing the body condition of individual whales to the average body condition of the sampled population we will be able to obtain a measure of relative body condition for each sampled whale (Christiansen et al. 2014). This will allow us to compare the relative body condition of lactating females with the body condition of their calves (obtained using the same approach as described above), to see how female body condition can influence calf growth and survival.
Our quantitative approach to measure body condition will also allow us to investigate variations in body condition over time (years), and allow comparison with other study areas, to get a better understanding of the health of humpback whales in the Southern Hemisphere.
References
Christiansen, F., G. A. Víkingsson, M. H. Rasmussen, and D. Lusseau. 2014. Female body condition affects foetal growth in a capital breeding mysticete. Functional Ecology 28:579–588.
Miller, C. A., P. B. Best, W. L. Perryman, M. F. Baumgartner, and M. J. Moore. 2012. Body shape changes associated with reproductive status, nutritive condition and growth in right whales Eubalaena glacialis and E. australis. Marine Ecology Progress Series 459:135–156.