Molecules and microchips: tools to unravel the secret lives of marine predators

Marine mammals and sea birds of the Southern Ocean live in some of the most remote and inaccessible environments on earth. As we travel the surface waters of their home on our way to and from Antarctica, we see only a fleeting view of a few animals, but learn little of why they are there, what they are doing, what they are hunting, and what might be hunting them. Answering questions such as these does more than satisfy scientific curiosity. We can only establish sustainable limits to the commercial fisheries of krill, squid and fish with some understanding of dynamic food chains. This means learning more than just who eats who, but also how much of a commercial species a predator might eat, and where, when and how it hunts for its prey.

Whilst these questions sound simple enough, answering them has proved an enormous challenge. As with so many complex endeavours, technology has provided the tools to move forward. Two developments in particular have provided tantalising insights into the diving behaviour of those marine predators that are small enough to catch and handle. The first is a miniaturised data-logger that records parameters such as water depth and temperature, light levels and swim velocity. The second is a radio transmitter that is tracked by satellite. When we use these instruments in combination, we're able to collect information about the travelling routes and dive depths of most species of seals and penguins. We are also able to get some idea of what they eat by sifting carefully through their faeces or vomits for recognisable remains of prey (not a pleasant task!). Notwithstanding these advances, the data have many biases and limitations, and important predators such as whales remain almost unstudied.

The Australian Antarctic Division has formed a new group called the Applied Marine Mammal Ecology (AMME) group within the Antarctic Marine Living Resources (AMLR) Program. The focus of this new group is to apply novel and ethically acceptable technologies to explore food-based relationships between southern ocean predators and commercially exploited species. An exciting combination of molecular and electronic tools is being developed. The molecular work incorporates the powerful approach of DNA-based studies, where, for the first time, faeces will be analysed for the DNA of all ingested prey. Other molecular analyses will complement this development, as well as the more traditional method of identifying recognisable remains of prey. Getting faeces from seals and penguins is relatively straightforward as they spend some of their lives ashore or on ice, and we can collect the material from those more accessible sites. We can even tell the species and sex of the animal that produced the faeces, as they leave traces of their own DNA in their faeces. Getting samples from animals that do not come ashore, such as whales, is more challenging. For this work, we have recruited collaborators from around the world who work with whales in areas they feed (and therefore defecate). We supply all these researchers with special “scoopers” to collect the faecal material. Fortunately, a whale’s physiology requires it to defecate near the surface.

In conjunction with the molecular work, developments in miniaturised electronics are making it possible to design and build a new generation of instruments. This should enable us to photograph a predator’s prey from a small camera on the animal’s head; track, and record the diving behaviour of whales over great distances; and record when an animal is feeding during a dive. The molecular and microchip technologies are currently being developed through detailed trials, often using animals from zoos and marine parks, or more accessible animals close to Australia. Applications to address strategic questions in Antarctica will commence in 2002.

The data generated by this new program will provide information for modellers and managers to better ensure the sustainable use of the marine living resources of the Southern Ocean.

Nick Gales
Antarctic Marine Living Resources Program,
Australian Antarctic Division