Post-release monitoring of pilot whales from a mass stranding in the Florida Keys

Jan 17, 2012 No comments By

 

Tagged adult male pilot whale

One of two adult male pilot whales tagged with a satellite-linked transmitter prior to his release.

Responding to a request by NOAA Fisheries on Friday night, 6 May, SDRP staff drove to Cudjoe Key in the lower Florida Keys early on the morning of 7 May to tag two male short-finned pilot whales from a mass stranding of about 21 whales.

The animals were initially scattered through the area when the stranding began on 5 May.

The Marine Mammal Conservancy and others were able to move all of the whales to a more centralized location and set up a temporary enclosure for initial treatment and evaluation.

The two adult males were determined by the attending veterinarians and NOAA Fisheries to be in adequate health and condition for immediate release.

The remaining live whales were subsequently transported to a rehabilitation center for continuing care.

The males were tagged with single-point attachment satellite-linked transmitters produced by Wildlife Computers.

These tags provided data on location, dive depths, and dive durations. One of the males was tracked for 17 days, and the other for 66 days, until the tag’s AA battery was drained.

Map of satellite tracking locations

Map of satellite tracking locations for stranded pilot whale Y-400 after release.

Both whales remained close together for the entire period both tags were transmitting, as they moved northward, and the dive patterns of the two whales were very similar to one another.

Given the whales’ previous behavior, researchers speculate that the abrupt loss of the signal from one whale resulted from failure of the transmitter or attachment on the whale’s dorsal fin rather than a gradual decline in the health of the whale.

As can be seen from the map, the remaining whale, Y-400, continued around the north and east side of the Bahamas and then southward to the northern shore of the Dominican Republic, often moving with prevailing currents. It continued to the northeast tip of Cuba, and then remained in the Windward Passage, separating Cuba from Haiti, for the last days signals were received.

The whale made occasional dives to 1,000-1,500 meters and occasionally stayed down for more than 40 min, among the deepest and longest documented dives for this species.

One of the concerns for mass strandings has been that retaining all of the members of the group in rehab until all are sufficiently healthy to be released at once may be detrimental to those individuals who were initially healthy.

The apparently successful release of these whales supports the idea of evaluating initial health and releasing individuals from the stranding site rather than retaining entire groups. The tagging and follow-up monitoring were supported by the NOAA John H. Prescott grants program.

 

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About the author

Randall Wells, PhD, is the Director of the Chicago Zoological Society’s Sarasota Dolphin Research Program (SDRP). He began studying bottlenose dolphins in Sarasota as a high school volunteer at Mote Marine Laboratory in 1970. He received his BA in Zoology from the University of South Florida in 1975, a Master’s in Zoology from the University of Florida in 1978, a PhD in Biology from the University of California, Santa Cruz in 1986, and a Post-doctoral Fellowship in Biology from the Woods Hole Oceanographic Institution in 1987. Employed by the Chicago Zoological Society since 1989, he is a Senior Conservation Scientist, and in this capacity he also manages Mote Marine Laboratory’s Dolphin Research Program. As a Professor of Ocean Sciences (adjunct) at the University of California, Santa Cruz, he serves as major advisor for MS and PhD students, and he is an adjunct Professor with the University of North Carolina, Wilmington, Duke University, and the University of Florida’s College of Veterinary Medicine. Wells was President of the Society for Marine Mammalogy (2010-2012).
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