Modern approaches to animal tracking and monitoring are possible due to the development of technologies that generate large, high-resolution datasets. These technologies, along with advances in analytical methods, enable biologists to follow the movements of free-ranging mammals, birds, and fish at unprecedented scales.
Modern technologies also help scientists understand how movement behavior helps animals survive and adapt in a changing world. These advantages do, however, come with typical big-data issues, such as computational load, intensive data management and processing, and challenging statistical analyses.
In a recent publication in the journal Science, Professor Ran Nathan of the Hebrew University of Jerusalem, together with students and colleagues from 12 countries around the world, reviewed a variety of technologies that have been used to gather information on the movements of animals in their natural environments.
All animals move, whether actively or passively, regularly or during specific life stages, to meet energy, survival, reproductive and social demands. Today, the ability of species to move is crucial if they are to cope with the effects of human-induced environmental changes.
In their review, Nathan and his colleagues assessed the main tools, insights, challenges and opportunities of the big-data revolution that has turned the field of movement ecology from a data-poor to a data-rich discipline. Wildlife tracking technologies vary in how they tackle the basic trade-offs between data collection rate, spatial coverage, tracking duration and the size of tracked animals.
Among eight major tracking technologies examined in this study, a technology called “reverse-GPS” stood out because of its capacity to produce big data on animal movement in a cost-effective manner. Other tracking technologies, such as GPS devices, computer vision systems and radars, can also produce big data, and the researchers recommended viewing all major tracking technologies as complementary rather than competing alternatives.
The new reverse-GPS system, called ATLAS, was developed by Nathan and Professor Sivan Toledo of Tel Aviv University, and their teams, under the auspices of the Minerva Center for Movement Ecology. It is unusual in its ability to track dozens of wild animals simultaneously, to within a few meters of their actual location, and at a high resolution (every second), over months. In addition, this system uses small, inexpensive radio tags that are attached to each animal. The system has already been used in Israel, UK, the Netherlands, and Germany, where it has enabled researchers to answer questions about basic movement ecology that could previously not be investigated.
“This sophisticated tracking system has ushered in a range of exciting discoveries and novel insights, including the first evidence for the existence of a cognitive map in a wild animal (a fruit bat), a pioneering study linking variation among individual birds (pheasants) in their cognitive ability and space-use patterns, and a discovery of a notable spatial segregation in foraging areas among bats that roost in two adjacent colonies, owing to an individual’s memory and information transfer among bats, with surprisingly no evidence for competition as a driving force,” Nathan shared.
“Acoustic telemetry,” another example of a reverse-GPS system, uses acoustic tags to track fish and other aquatic animals under water. Systems of this kind have been used in rivers, lakes and seas around the world, to gain insights into dealing with risks for wildlife that derive from their interactions with humans.
For example, by using an acoustic tracking system in European rivers, researchers found that downstream-migrating eels (a critically endangered species) and Atlantic salmon change their movement behavior when they encounter dams, which is likely to result in increased energy expenditure and mortality risk.
GPS is another important tracking technology that has been used to track relatively large animals at high resolution. For example, GPS tracking allowed Nathan and his students to reveal that young vultures from the declining population in Israel climb the thermals (rising columns of warm air) much less efficiently than do experienced adult vultures when those thermals are drifted by winds.
Elsewhere, GPS tracking of critically endangered California condors can provide early alerts to avoid collisions with wind turbines in the area, while GPS tracking of albatrosses can help locate vessels fishing illegally in remote ocean areas. All these applications help to uncover the reasons why animal behavior varies and to assist in biodiversity conservation and ecosystem management.
In another fascinating application, GPS tracking provided unique information about the avian flu epidemic that led to the death of thousands of cranes in Israel earlier this winter. This is such recent research that it has not been included in the review article in Science.
“At the first sign of death among a few dozen cranes, a much greater proportion of our GPS-tagged cranes died or were suspected to be infected, given the sudden reduction in their movement and activity. We informed the authorities that a drastic mortality event was coming, as unfortunately did happen, and that urgent measures should be taken,” Nathan explained.
Later, the team was able to trace the fate of infected birds and found that some had eventually recovered. “We now closely watch the data from cranes that winter in Africa to monitor the possible second wave of the outbreak when millions of migrating birds will soon arrive,” Nathan emphasized.
The field of movement ecology is rapidly expanding scientific frontiers, not only through the use of the big-data technologies discussed by Nathan and colleagues, but also through enhanced opportunities for interdisciplinary and collaborative research projects.
“This is also the story of our research,” Nathan explained, referencing a Fish Telemetry workshop in the Czech Republic organized by Professor Ivan Jarić in 2018 that he was invited to attend. “I met a group of excellent researchers with backgrounds, expertise and research subjects quite different from mine. I remember the exact moment that gave birth to our joint project, when I shared my vision for a big-data revolution in movement ecology. Preparing our review together has been a wonderful experience; working together across disciplines is certainly the way to go.”
By Alison Bosman, Earth.com Staff Writer