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Whale LIMPET Tags
December, 3rd 2016
Cetaceans have long captured the attention of both scientists and the general public, yet our understanding of their biology and our ability to implement viable management strategies for them has been hampered by the logistical difficulties of observing them and measuring important parameters such as distribution, feeding and migratory behavior, and vital rates. These problems have been partly overcome in the last twenty years by application of rapidly improving telemetry techniques. Biologists have been especially successful in attaching tracking devices to cetaceans at the small and large end of their size range. Large body size in some species has permitted researchers to achieve long attachment durations by utilizing anchoring systems that penetrate 15 to 33 cm into the whale. This approach is clearly not suitable for smaller cetaceans whose blubber and muscle thickness combined is much less than 15 cm. Until recently, there were only two options for attaching telemetry devices to small to medium-size cetaceans: short-term attachment with suction cups, or capture and subsequent surgical
implantation of attachment pins for securing devices. The obvious disadvantage of suction-cup attachment is the short duration (typically < 24 hours). Capture and surgical pin attachment has numerous disadvantages including difficulty, cost and potential for adverse impact on the subject. In our attempt to quantify the role of killer whale predation on marine mammal populations in the North Pacific, we set out to design a new miniature, low-drag location-only satellite transmitter package and a method for remotely-attaching it to the dorsal fin of killer whales. Various designs were tested, but we focused on barnacle-type tags, so called because the tags mimic a barnacle with the main body outside of the whale being held on by small percutaneous projections. Our most successful design was a tag and attachment system we now call the Low Impact Minimally Percutaneous External-electronics Transmitter (LIMPET) tag. We first used this system to tag killer whales in Antarctica. (Download File)
The method of deployment for the LIMPET tag uses a modified airgun or crossbow to launch an arrow with the LIMPET tag held onto its end. Here you can see an early version of the LIMPET tag with the barbed titanium darts designed to penetrate approximately 6.5 cm into the dorsal fin.
Duration of transmissions on killer whales ranged from a few days to 3 months. Tags fall out by the darts simply backing out of the entry holes and not by tearing through new fin tissue. The wounds usually heal quickly, - within 6 months after tag loss, killer whales usually have nothing worse than small (< 3 cm) well-healed scars at the dart penetration sites.