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Archival Tags are miniature electronic data acquisition systems designed to be attached to or implanted in live animals. The term arose in the community that seeks to track wild animals or investigate their environmental conditions or behavior. One major function is Geolocation.

Such tags may simply record a time series of relevant environmental data such as solar irradiance, temperature, and (for a swimming animal) depth for processing later after the tag is recovered. Tags having a primary goal of geolocation to determine an animal track may perform a first level of inference on-board the animal, measuring environmental variables every minute but recording or transmitting condensed information such as sunrise and sunset times, sea surface temperature, and water opacity. Another approach for condensing data is to record or transmit only selected raw data judged to be most relevant, such as that surrounding apparent sunrise or sunset.

An advantage of such processing is that the resources required to store or transmit the information supporting geolocation is greatly reduced, allowing a tag with limited memory or a limited communication link to bring home an extended animal track in a relatively few bytes of data. Disadvantages of relying entirely on such a condensed record include that the experimenter's opportunities for being surprised by the data in an illuminating way are reduced, as there is less detail visible, and that some animal behavioral issues cannot be addressed. Some tags offer both features: a compact "day log" of processed results or extracted points for every day, with the rest of the usually-limited memory or communication capacity dedicated to blocks of raw data selected from the raw time series.

Major manufacturers of archival tags are Lotek Wireless (www.lotek.com), Microwave Telemetry (www.microwavetelemetry.com), Star-Oddi (www.star-oddi.com) and Wildlife Computers (www.wildlifecomputers.com). Research results obtained with such tags may be seen at www.tunaresearch.org .