Aarhus University Seal / Aarhus Universitets segl

Telemetry
and tagging

Nearly all processes related to animal ecology, including foraging, predator avoidance, mating, dispersal and migration, are intimately linked to animal movements. The study of animal movement can help estimate survival and reproduction rates within specific populations and can determine distributions of individuals, populations, or species. As such, understanding and predicting where, how and why animals move to particular areas is arguably the most crucial objective of wildlife research and is therefore central to establishing proper management and conservation strategies.

Marine mammals (including seals, dolphins, whales and walruses) live in an environment that makes it extremely difficult to study them. Until fairly recently, direct observation was the most reliable method of collecting data on their location. Now, wildlife researchers often use telemetry (derived from Greek: tele = remote, and metron = measure) to more effectively collect vast quantities of location data, making it possible to study animal movements across a range of spatial and temporal scales. During this process, animals are fitted with electronic tags that communicate with satellites (GPS or Argos systems) to determine a position on earth. In addition, tags can also include sensors that measure temperature, activity, sound, diving depth and duration. This information is either stored within the tagging device, which then needs to be re-collected, or transmitted directly to a receiver device. When choosing the best tracking device, researchers must consider the size and movement patterns of the study animal, the study budget, and, most importantly, the research questions they want to address. 

Tagging systems

Argos

Argos is a French company that offers satellite positions from several kinds of tags, used to track animals all over the globe. It is particularly useful for tagging marine mammals that only surface for a few seconds at a time. The marine mammal research unit here at Aarhus University has used Argos tags on several whale and seal species since 1990. Additionally, in 1997, we initiated a close collaboration with some of the gill net fishermen; sometimes a porpoise is trapped in their nets, and then we help release it back into the wild. During these releases, our scientists have access to a live porpoise, which is a great opportunity to tag a healthy animal. We have now tagged over 150 harbour porpoises both with Argos tags and other types of tagging devices to follow their movement and behavior. It is possible to follow some of the tagged animals here on our live wildlife tracking site.

Example of a harbour seal fitted with an Argos tag. This individual was tagged on Anholt as part of large research project to study the movements and distribution of harbour seals in the Kattegat area (click on photo to enlarge) Photo by Anders Galatius.
Example of a movement path of one harbour seal fitted with a GPS collar near the Nysted wind farm (red grid). A Bayesian State-Space Model was used to classify each position into a behavioural state (red = foraging, green = moving). (Click on photo to enlarge).

GPS

Global positioning system

Example of a movement path of one harbour seal fitted with a GPS collar near the Nysted wind farm (red grid). A Bayesian State-Space Model was used to classify each position into a behavioural state (red = foraging, green = moving). (Click on photo to enlarge).

A-Tag

Photo by Au

D-Tag

Digital tag

Harbour porpoise with a D-tag (digital tag) mounted with suction cups, photo by Au