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Research article - Peer-reviewed, 2022

Retention and loss of PIT tags and surgically implanted devices in the Eurasian beaver

Mayer, Martin; Lian, Marianne; Fuchs, Boris; Robstad, Christian A.; Evans, Alina L.; Perrin, Kathryn L.; Greunz, Eva M.; Laske, Timothy G.; Arnemo, Jon M.; Rosell, Frank

Abstract

Background Passive integrated transponder devices (PIT tags) are a valuable tool for individual identification of animals. Similarly, the surgical implantation of transmitters and bio-loggers can provide useful data on animal location, physiology and behavior. However, to avoid unnecessary recapture and related stress of study animals, PIT tags and bio-loggers should function reliably for long periods of time. Here, we evaluated the retention of PIT tags, and of very high frequency (VHF) transmitters and bio-loggers that were either implanted subcutaneously or into the peritoneal cavity of Eurasian beavers (Castor fiber). Results Over a 21-year period, we implanted PIT tags in 456 individuals and failed to detect a PIT tag at recapture in 30 cases, consisting of 26 individuals (6% of individuals). In all instances, we were still able to identify the individual due to the presence of unique ear tag numbers and tail scars. Moreover, we implanted 6 VHFs, 36 body temperature loggers and 21 heart rate loggers in 28 individuals, and experienced frequent loss of temperature loggers (at least 6 of 23 recaptured beavers) and heart rate loggers (10 of 18 recaptured beavers). No VHFs were lost in 2 recaptured beavers. Conclusions Possible causes for PIT tag loss (or non-detection) were incorrect implantation, migration of the tag within the body, a foreign body reaction leading to ejection, or malfunctioning of the tag. We speculate that logger loss was related to a foreign body reaction, and that loggers were either rejected through the incision wound or, in the case of temperature loggers, possibly adhered and encapsulated to intestines, and then engulfed by the gastro-intestinal tract and ejected. We discuss animal welfare implications and give recommendations for future studies implanting bio-loggers into wildlife.

Keywords

Animal welfare; Body temperature logger; Castor fiber; Heart rate logger; Surgery

Published in

BMC Veterinary Research
2022, volume: 18, article number: 219
Publisher: BMC

Authors' information

Mayer, Martin
Aarhus University
Lian, Marianne
Inland Norway University of Applied Sciences
Fuchs, Boris
Inland Norway University of Applied Sciences
Robstad, Christian
University of South-Eastern Norway (USN)
Evans, Alina L.
Inland Norway University of Applied Sciences
Perrin, Kathryn
San Diego Zoo Wildlife Alliance
Greunz, Eva
Center for Zoo and Wild Animal Health
Laske, Timothy G.
University of Minnesota Twin Cities
Arnemo, Jon M. (Arnemo, Jon)
Inland Norway University of Applied Sciences
Swedish University of Agricultural Sciences, Department of Wildlife, Fish and Environmental Studies
Rosell, Frank
University of South-Eastern Norway (USN)

UKÄ Subject classification

Other Veterinary Science

Publication Identifiers

DOI: https://doi.org/10.1186/s12917-022-03333-1

URI (permanent link to this page)

https://res.slu.se/id/publ/118027