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The Secret Life of Dolphins

The Secret Life of Dolphins

By Heidi Pearson & Gabriel Machovsky-Capuska

New underwater camera technology has captured the social lives of wild dolphins for the first time, revealing how deep and for how long they dive, how they nurture their young and even how they play with objects in the ocean.

Dolphins are one of the most visible, intriguing and charismatic creatures of the sea, yet we know very little about what they’re doing underwater.

Until now…

Our team has developed a tracking device that has provided the first glimpses of dolphin behaviour from their perspective and on their own terms. With this information we can better understand the daily life of dolphins, such as how they interact with one another, how mothers raise their offspring, how they find food, and how they use their habitat. We can also understand how these animals might be impacted by threats such as coastal development, shipping traffic, vessel noise and interactions with fishing gear. Putting all of this together will help us to protect them.

Studying Wild Dolphin Behaviour

Dolphins are notoriously difficult to study in the wild. They have a small body size, are fast-moving and live in groups that can contain 1000 or more individuals.

Traditionally, dolphins have been observed from small research vessels that travel alongside the group. However, as dolphins spend only a small fraction of their time at the surface, scientists are unable to see many behaviours and social interactions. In addition, it’s nearly impossible to follow a single individual in these large dolphin groups. Therefore, observations are often taken at the group level, which may obscure important individualistic behaviour.

For the past 20 years, researchers have been attaching video cameras to large cetaceans such as humpback whales, blue whales and sperm whales. This has provided detailed information about the movement and behavioural patterns of these species.

However, the small body size and fast nature of dolphins prevented researchers from successfully deploying miniaturised cameras on them. Our multidisciplinary team developed a special technique for attaching our cutting-edge C-VISS (Cetacean-borne Video camera and Integrated Sensor System) device to dolphins.

A New Dolphin-Tracking Device

Our video camera was modelled on a system developed to record the behaviour of seabirds. However, attaching a video camera to a dolphin comes with a unique set of challenges that differ from seabirds. For example, while it’s possible to capture a masked booby to attach the camera, it’s not possible to capture a dolphin so we had to develop a specialised pole to deploy the device. While it’s possible to tape the camera to the tail feathers of a seabird, it’s not possible to do the same on dolphins so we had to develop a special attachment method using suction cups. Finally, dolphins dive deeper than boobies so we had to ensure that our system was both waterproof and strong enough to withstand the increasing pressure during deep dives.

While the video camera is the central component of our device, C-VISS contains additional instruments to help us to understand dolphin behaviour. A time–depth recorder measures the diving behaviour, allowing us to understand how deep and for how long a dolphin carrying the device is diving. C-VISS also contains satellite and VHF transmitters that help us track the dolphin while it’s tagged and to recover the device once it falls off the dolphin.

C-VISS is archival, so it must be recovered to download the data. The video camera, depth logger and transmitters are held in a special float that is durable enough to withstand the pressure increases that occur while a dolphin dives, yet light enough that it is buoyant. When the suction cups detach from the dolphin, the device floats to the surface, sending a signal to a satellite with the approximate geographic coordinates. Once we arrive in the area, we use a VHF antenna to find the device.

Importantly, C-VISS is non-invasive and does not harm the dolphin carrying the device. We conducted a series of trials with a Pacific white-sided dolphin at the Vancouver Aquarium and several dusky dolphins in the wild, and we did not detect any negative impacts of the device on the dolphins. One tagged dolphin appeared to be so undisturbed by C-VISS that we even observed it sleeping at the surface!

Meet the Dusky Dolphin

Working with our project partners at the New Zealand Department of Conservation, Massey University and the US National Oceanic and Atmospheric Administration, we spent 2 years developing, refining and testing the device. We then tagged eight free-swimming wild dusky dolphins off the coast of Kaikoura (Fig. 1), and obtained nearly 9 hours of video footage. The longest attachment duration was 5 hours while the shortest attachment duration was 9 minutes. The attachment duration depends on a variety of factors, including where the device is placed on the body, the strength of the suction cups and the dolphin’s behaviour.

Dusky dolphins are bioindicators: any changes we observe in their distribution, abundance and behaviour indicate larger changes in the ecosystem. We have been making boat-based observations of duskies since 2004, and this gives us a good understanding of their behaviour at the surface. However, we have always wondered what they were doing underwater.

Kaikoura is a perfect place for studying duskies because approximately 1000 individuals occur off the coast at any given time.

During the day, duskies are typically found near the coast where they socialise, rest and travel in large groups. These groups can be quite boisterous as individuals perform an amazing array of leaps including backflips, somersaults, side slaps and belly flops.

During the night, duskies move away from the coast to feed on fish and squid in the waters of the Kaikoura Canyon. Once this midnight feast is over, the dolphins return to the coast in the early morning hours where they start the cycle over again.

A Day in the Life of a Dusky Dolphin

For the first time we are seeing the behaviour of wild dolphins from their perspective, and getting an indication of what a day in the life of a dusky dolphin is like. Our video footage has even revealed instances where the dolphin was filming our research boat!

What have our data revealed? For example, how social are they? How do mothers care for their calves? What is their habitat like? How deep, how often, and for how long do they dive?

We are seeing how social individual dolphins are. We can quantify this by recording the number of individuals swimming with a tagged dolphin at any given time, and by looking for signs of affection such as flipper rubbing: dolphins show friendliness by gently extending their flippers to touch another dolphin’s flipper or other part of the body.

We are also seeing how mothers care for their calves. A calf typically swims in one of two positions near its mother (Fig. 2). It will swim beside its mother in echelon position, which helps the calf to get a “free ride” by riding the pressure waves created by the swimming action of its mother. A calf will also swim underneath its mother in infant position. This may provide protection from predators as the calf is physically tucked under its mother. Additionally, when viewed from below, the mother–calf pair looks like one large dolphin (Fig. 3), which may be a deterrent to predators such as sharks. We are even seeing intimate behaviours such as calves nursing (drinking their mother’s milk), which for most dolphin species is virtually impossible to be seen by researchers on the surface.

We are also seeing how dolphins use their habitat, from kelp forests to the sandy sea floor to depths beyond the sunlit zone where the sea becomes dark. We are also seeing how dolphins interact with their habitat, for example by playing and “wearing” kelp on their flippers (Fig. 4).

Finally, we can correlate all of these behaviours with data obtained from our time–depth recorder. This helps us to determine how behaviour changes according to how deep and for how long the dolphin is diving.

Future Research Directions

All that we have seen so far is revealing the complexity of the lives of dolphins, yet we are just breaking the surface with the power of this new research tool. We foresee several important future research directions.

Understanding the nutrition of wild marine predators, such as dolphins, is a challenge that science has yet to solve. We need to know exactly what the food and habitat requirements of marine predators are. Learning more about their feeding patterns on a daily basis and what nutrients they contain will be immensely useful for protecting endangered species.

As we continue to study duskies and other dolphin species, we can better monitor and understand changes to the marine environment. As we continue to monitor dolphins and correlate fine-scale information on their social, foraging and diving behaviours with data on how the ocean is changing with respect to sea surface temperatures, circulation patterns and plankton abundance, we will have a better understanding of how climate change is affecting other, less visible marine organisms.

Last but certainly not least, seeing the world through the eyes of a dolphin will help us to better protect them. The more we understand about how individual dolphins find food, care for their young, find mates and avoid predators, the better we can conserve them by establishing protected areas and developing policies that limit human interference with these behaviours.

Heidi Pearson is Associate Professor of Marine Biology at The University of Alaska Southeast. Gabriel Machovsky-Capuska is Loxton Research Fellow at The University of Sydney.