Figure 1. “Betty” and son “Big Al” at Mote’s dolphin hospital.

      A mass stranding on 5 May 2007 involved two mother-calf pairs of Risso’s dolphins coming ashore near Bonita Beach, Lee County, Florida.  Both pairs were transported to Mote’s dolphin hospital, where one pair died, but the other pair was successfully rehabilitated (Figure 1).  The surviving mother, “Betty”, was admitted with septicemia caused by a very drug-resistant bacterium and internal abscesses that required a long course of treatment.  The calf, “Big Al”, was thought to be only several weeks old at the time of stranding.  He appeared healthy initially, but soon developed an infection.  Both dolphins eventually responded to treatment, and on 27 September 2007 they were transported aboard the yacht “Tomcat” about 100 nautical miles southwest of Sarasota.  “Betty” was tagged with a satellite-linked transmitter for remote tracking and collection of dive data (Figure 2), and both were released together over the edge of the continental shelf. 

Figure 2.  Satellite-linked transmitter on “Betty’s” dorsal fin.

Since release, “Betty”  has covered much of the Gulf of Mexico, mostly remaining near the continental shelf edge and slope (Figure 3), in habitats of the kinds known to be used by Risso’s dolphins.  Much like “Clyde”, the adult male Risso’s dolphin tracked following rehabilitation and release in 2006, “Betty”  spends most of her time in waters less than 50 m deep, but she makes occasional dives to 600-800 m, and can remain on a dive for 11-15  minutes.

Figure 3.  “Betty’s” track since release on 27 September 2007.