Wildlife reserves have historically allowed scientists to keep track of endangered species on the ground. But how do we monitor wildlife that flies or swims?
Scientists track a wide variety of animals, from butterflies to great white sharks, in order to study how they use their environment, which foods are important and to gain insights into behaviour and condition of the creatures as well as to identify key breeding areas that may need protection.
Miniaturisation of electronics and improvement in battery technology is making it possible to follow even the smallest birds and insects on their migrations. Satellite technology allows us to track the position of animals anywhere on the planet, while crittercams and accelerometers give us a ringside view of their behaviour. “Is it diving, running or sleeping? We can follow animals into great wildernesses without having to be there,” says John Fryxell, an arctic ecologist at the University of Guelph, Ontario, Canada.
It is advances in technology that make it possible to study animals in even the remotest polar regions and the deepest oceans without interfering with the creature’s day to day activities.
For most approaches, the target animal must be caught and appropriate technology attached to it. This is much harder than it sounds. “It’s very much a case of horses for courses – what works on a ladybird won’t work for an elephant matriarch in the Serengeti or a deep-diving Antarctic elephant seal,” says Professor Mike Fedak of the Sea Mammal Research Unit (SMRU) at the University of St Andrews, Fife, UK, world leader in tag design.
Fixing a satellite tag to a great white requires chumming the waters with a smelly cocktail of rotting whale blubber from a boat, so that the shark swims up the scent trail, and then physically darting the shark on the dorsal fin using a long pole – a keen sense of balance is essential.
Male polar bears have long slender necks that conventional large-animal GPS collars will not stay on, so the bears have to be darted from a helicopter, anaesthetised, and small transmitters implanted inside the ear. The females have a different head and neck shape, and so are fitted with conventional collars.
The very lightest of tags are attached to small birds and insects. The epic migration of the Arctic tern, which travels 70,000km a year from pole to pole in search of food, was recently unravelled using a GPS tag weighing only 1.4g and attached to a ring on the bird’s foot.
Tiny 12mg transponders, in combination with entomological scanning radar, are used with foraging bees and butterflies. This is being used to determine the effects of pesticides and disease on their flight paths.
It is not only size and habitat that dictate the type of tag used to track an animal, but the budget and the question to be studied. Does Arctic mining affect caribou migration routes? Are subsea tidal turbines harmful to marine mammals? When is an invasion of insect pests due? What effect is climate change having on Antarctic glaciers?
In one of the largest migrations in the world, great herds of caribou migrate across a vast area of northern Canada over one million kilometres square. Some herds travel over 3,000 km every year between their winter and summer ranges. Their routes are determined by their need to search for food and shelter, to reach traditional calving grounds, and to avoid wolves or biting insects.
The University of Guelph’s Fryxell is exploring the world of caribou and their chief predator, the wolf, using a combination of crittercams, which show both animal’s point of view, and a GPS/accelerometer on a collar to provide information on behaviour. This can form a baseline before any extractive industries commence.
Subsea turbines are relatively new in our seas and little is known about how dolphins, whales, seals and porpoises will react to them, if at all. The mammals are tagged with acoustic pingers, and the pings are picked up by listening stations. “It’s generally much easier to hear species such as the harbour > < porpoise than it is to see them, particularly in poor weather” says SMRU’s acoustic tracking expert Douglas Gillespie. “However, developing methods for working out how many animals there are from acoustic data is much harder than for visual and that’s something we’re working on, it’s non-invasive and useful in turbid waters.
“We can also use acoustic systems to track vocalising animals in 3D to see how they behave around seabed structures. Obviously this approach does not work too well with less vocal animals like UK seals, so we will combine passive and active acoustic tracking to cover those too.” Similar approaches can answer questions as to the effects of seismic surveys or pile driving in sensitive areas.
Radar in flight
Vertical radar is used to track the arrival of migratory agricultural pests such as the silver Y moth. The insects leave Africa and arrive in the UK during the peak growing season. The radar has been tracking their arrival and departures for a decade in a long-term project that may result in an early warning system for migratory invasions of insects. The radar has also revealed information about their behaviour.
“Far from being completely at the mercy of the winds, these insects rise in the evening to test the prevailing air currents,” says Rothamsted Research’s radar engineer Jason Lim. “If they are unfavourable for their journey, they will descend and stay put.
“By using only favourable winds the insects multiply their flight speed by five or six times to fly as fast as migratory songbirds – up to 100km/h, completing the journey to North Africa from the UK in only four days.” These flying insects are probably able to sense their orientation relative to wind direction by using geomagnetic cues.
The radar sends up a spinning cone-shaped beam at 9.41GHz and samples at 15 height bands from 150m to 1.2km altitude, covering an area from 13m diameter to 60m across. At 300m altitude the radar can discriminate even insects as small as 2mg and 5mm-long such as ladybirds. The radar scans the underside of the insect’s body multiple times in its passage across the beam, while the insect’s speed, direction, shape, size and wingbeats are determined, all of which help to identify the insect. Balloon-suspended trapping nets are sent up to the different sample heights to ‘air-truth’ the radar, and help to develop the algorithm that is used to identify the insect to group level. The same radar system is used to track imminent swarms of locusts in Australia.
Many biologists’ tags have been taking advantage of the ARGOS satellite system since the 1980s. The system was originally launched to receive oceanographic data. “At the SMRU, scientists and engineers work closely as users and designers of tags,” says SMRU’s head of instrumentation Phil Lovell.
“It’s about getting feedback about what works and what makes sense. We are always trying to work out how to improve the on-board algorithms for crunching data prior to transmission because ARGOS restricts us to the equivalent of a 40-character tweet – a mere 32 bytes – and that includes an ID code.”
Even under these tight constraints, a great deal can be learned from tagging data. Many marine mammals forage at productive oceanic frontal systems and alteration in these water masses are likely to be one of the first major effects of climate change in the oceanic environment. Knowledge of how the animals interact with them is vital to allow us to predict what impact this might have.
There is something of a natural progression of curiosity in the world of animal tracking. Early studies asked the simple question – where do they go? Now researchers are finding that ever more complex questions can be answered – there is still a huge amount to be learned from tracking animals as they go about their daily lives.
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