COLLARS: By far the most commonly used option. There are 2 main types:
EAR TAGS: Best option for protection of juvenile or increasingly growing animals, as collars could suffocate over time.
Collars with expandable belting can also be used but there is a limit as to the level of expansion. Also a great option for Beaver as it is attached on the tail.
IMPLANTS: There is loss of detection range because of the type of antenna used and the body mass, but in many cases is the only option for mammals whose neck is larger than the head (e.g. otters)