This article gives a cool account of how to tag a hammer head shark with an electronic chip, giving an insight into how scientists must come up with technological advances in order to track animals that are difficult to follow or under-studied. Attaching tags is much harder in species that have no neck for a collar. This problem is solved in the hedgehog by gluing a small VHF radio transmitter to a patch of spines. For the shark, the tag is inserted under the skin.