Earthwatch Dolphin Monitoring Program 2005-2006
By Jason Allen, BS, Field Coordinator and Lab Manager, SDRP

Spectrograms of the original and the synthetic version of a signature whistle used in playback experiments.

We have been able to continue our year-round monthly monitoring of the Sarasota dolphin community thanks to support from Earthwatch Institute volunteers and NOAA Fisheries. The Sarasota bottlenose dolphin community is the most thoroughly studied free-ranging dolphin population in the world. We continue to address increasingly refined questions about the lives of these animals with the benefit of information gained through our intensive year-round studies of their distribution, social and reproductive patterns.

F155 with her third calf, 1553, born in June 2006.

Photo-identification surveys were conducted on 102 days from November 2005 through October 2006 with the assistance of Earthwatch volunteers and undergraduate interns. We had a total of 15 volunteers from ten states and two countries. These volunteers contributed over 2,000 hours to our project. We had 593 group sightings that totaled 1,900 dolphins (including resighted animals). Monthly values were variable (Figure 1), but overall we averaged about five sightings and almost 18 dolphins per day. These values have remained fairly consistent over the past several years. We had a high of 14 sightings in one day during a September 2006 survey and a high of 92 dolphins on that same day.

Merrily, her yearling, F228 and others in a large group off Key Royale Bar, January 2006.

We documented the births of seven new calves during the spring/summer of 2006. FB 25 had her sixth calf and Claire had her fifth while, at the age of eleven, Scooter had her first. Other mothers included Saida Beth, Murphy Brown, FB 93, and FB 183. Sadly, Saida Beth’s calf was never seen alive. She was observed on the 27th of June carrying the dead calf on her rostrum. The calf was recovered the next day; upon necropsy no cause of death could be determined. Of her eight calves, only two have survived more than three years (Noah and FB 173). Four of the ten calves from summer 2005 have also died, or are missing and presumed dead.

Murphy Brown surfacing under Longboat Pass Bridge. Neither the local boys on the beacch nor our field team could tell that she was pregnant with her third calf.

Since November 2005 we have lost four adult long-term Sarasota Bay community members: FB 06, FB 75 (Pup), Jose, and FB 100 (Scythe Fin). Sadly, each of these deaths involved human interactions, specifically ingestion of recreational fishing gear. Scrappy, the calf of Scooby Doo, was involved in yet another, though very unusual, case of human interaction. He was observed this past July with an unknown type of cloth wrapped around him just in front of his pectoral fins. When we briefly handled the animal to remove the material, we discovered that it was an extra large men’s Speedo! Scrappy was released the same day, has been observed many times since, and is doing well.

Through our Earthwatch-sponsored surveys, we have accounted for over 90% of the Sarasota Bay community members during the 2005-2006 field season. As of October 2006, the number of dolphins regularly using the waters surrounding Sarasota Bay stands at approximately 155 animals. We would like to thank all of our Earthwatch volunteers for their interest in, and support of, the Sarasota Dolphin Research Program.

Births, additions, deaths, and losses to the Sarasota Bay population over the past year. Seven new calves were born and four well-known animals were confirmed dead.