Abstract

Wild pinnipeds often require capture for disentanglement, rehabilitation, or research studies. Capture of these animals has been accomplished on land or in water with a combination of nets, divers, or traps.^1,2 More recently, the use of remote sedation delivered by dart has been used for captures.^3,4 This technique can improve targeting of specific individuals and easier handling of larger animals such as adult California sea lions (Zalophus californianus).^3,5 Recent studies have shown that some animals that are sedated on land and subsequently reenter the water continue to resurface to breathe, even in a sedated state.⁴ However, there is still risk of drowning due to entrapment, or of injury from other animals or boats in the area. Furthermore, it can be difficult to relocate sedated animals, as they may swim long distances or be located within a group of conspecifics. To aid in tracking and recovery of wild pinnipeds, we have developed a remote sedation dart with an integrated acoustic transmitter that allows for tracking of a darted animal up to 1 kilometer away. Using a portable, directional hydrophone we have successfully tracked darted animals by boat, which allows for approach and recovery once the animal is sedated. We selected the transmitter based on size, weight, and frequency to allow for efficient delivery, while taking care to mitigate further risk to the animal. The selected frequency is outside the hearing range of tested pinnipeds species in air or water.^6,7 We hypothesize that acoustic-transmitter darts will increase capture success while decreasing negative outcomes in remotely sedated animals. Early results support this hypothesis. This technique can be applied to targeted capture of many pinnipeds species for research, disentanglement or rescue of pinnipeds.

* Presenting author

Literature Cited

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7.  Mulsow J, Finneran JJ, Houser DS. California sea lion (Zalophus californianus) aerial hearing sensitivity measured using auditory steady-state response and psychophysical methods. Journal of the Acoustical Society of America. 2011;129:2298.