Follow-up observations of satellite-tagged sperm whales in the Gulf of Mexico for evaluation of potential tag effects and wound healing

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Long-term implantable satellite tags provide valuable distribution and behavior information for wide-ranging large whales. Follow-up observations of whales tagged with these telemetry devices are critical in evaluating potential health effects from tagging, but are especially difficult for species with cosmopolitan distributions with the ability to travel 100+ km/day. Sperm whales in the Gulf of Mexico are good subjects for such studies, in that animals can be predictability relocated year-round in areas around bathymetric features and have been tagged over a period of many years. A total of 134 Argos satellite-monitored radio tags were deployed on sperm whales from 2001 to 2013: 94 Telonics ST-15 location-only tags (1.9 cm diameter, 26.3 cm long implantable portion), 20 Wildlife Computers Spot-5 location only tags (2.1 cm diameter, 27.2 cm long implantable portion), and 20 Wildlife Computers MK-10 Advanced Dive Behavior tags (2.6 cm diameter, 24.8 cm long implantable portion). Whales were photographed at the time of tagging for identification and to assess tag application. Follow-up observations were undertaken in subsequent tagging seasons and on dedicated resighting trips. Twenty-nine whales were resighted (some up to four times in multiple years) from 1 day to 10 years after tagging. Fifteen of these had tags still attached and 28 were resighted without tags. Some whales were initially resighted with tags, but without tags on subsequent observations. Swelling occurred at two tag sites. Scars after tag loss consisted of fully re-pigmented divots (1-3 cm deep by 4-8 cm diameter). None of the resighted whales showed signs of emaciation or having other health issues, and their behavior was similar to that of untagged whales. One whale was observed with a new calf one year after tagging. These results indicate that satellite tagging poses little or no observable adverse health effects for sperm whales.