Wells discusses dolphin research at GPICA meeting
The Greater Pine Island Civic Association welcomed Dr. Randy Wells, vice president of Marine Mammal Conservation at the Chicago Zoological Society and director of the Sarasota Dolphin research program, to its meeting May 3.
Wells gave a presentation on the behavior, social structure, life history, ecology, health population and biology of the 170-member dolphin community program, of which he is the director in Sarasota. According to Wells, he and the team he works with have gotten to know the dolphins they encounter individually over the years. The team tracks them through their lives, as they are recognizable by patterns on their dorsal fins.
In some cases, he said, they can be tracked over periods of decades.
“When we got started in 1970, it was as a pilot study,” said Wells, “we didn’t have any funding at all. We did it in our spare time, as Blaire Irvine, who started the project, took me on as a high school assistant.”
Irvine’s interest in the behavior of wild dolphins led him to go out and study the mammals with a local commercial dolphin collector. In the beginning of this research, Wells said, they had no preconceived notions about what dolphins did. As they began tagging the dolphin, it became apparent that they were seeing the same dolphin, although some of the tags, he said, didn’t stay fastened, there were marks indicating that they had been previously tagged.
By 1975 and 1976, a grant was secured from the Marine Mammal Commission agency, then newly formed from the Marine Mammal protection Act. They were able to locate 11 of 12 dolphins they had tagged in 1970 and 1971, said Wells.
“We used tags and markings of various kinds, and these ancient radio transmitters that were state of the art at the time to tell us something about the movement patterns of the dolphins,” said Wells. “These radio transmitters worked in the CB range so while we were out tracking dolphins in the middle of the night with the skip that you get sometimes with CB radios, we’d be hearing truckers in Omaha over our receiver, and they were probably wondering what the beeps were that they were getting and probably figured the government was listening in on them.
“The movement patterns that we learned from these transmitters and from re-sightings of the tagged animals showed that there was a resident community of dolphins from the southern edge of Tampa Bay southward down to what was midnight pass at the time.”
This conclusion was reached by the continuation of this work, Wells said, through a variety of organizations, such as the University of California Santa Cruz and Dolphin Biology Research Institute, and eventually Chicago Zoological Society. They were able to follow the animals for years, if not decades, by looking at natural markings on their fins to pursue the idea of residency.
“The idea that dolphins had home ranges was both our first discovery and probably our most important discovery,” Wells said. “We learned that the dolphins in Sarasota lived in a multi-decadal, multi-generational, year-round resident community. We studied about six generations in that resident community and at any given time we can have as many as five concurrent generations within a maternal lineage with individuals of up to 67 years of age.”
Some of the work done by the organization has taken the group down into Tampa Bay, Charlotte Harbor and Pine Island Sound. What they’ve learned about Pine Island Sound and Charlotte Harbor animals is that they have patterns that are very similar to those in Sarasota. They saw consistency in terms of numbers of individuals from season to season and year after year, Wells said. In 2006, after Hurricane Charley and a particularly bad season of red tide, they were able to locate 94 percent of the same animals they had identified in the early 2000s, in the waters of Charlotte Harbor and Pine Island Sound.
“These animals truly are long-term residents, just like the ones we see up in Sarasota,” said Wells.
Wells further explained the maturation, reproduction and habits of these animals, with their mortality often held in the hands of humans. The females, he said, mature at about 5 to 10 years of age and the males at about 10 years of age. Most births occur from May to July. The calving season occurs after a 12 1/2-month gestation period. Using ultrasound to look at pregnancies, they’ve learned that 83 percent of the pregnancies result in live calves. Mothers can be anywhere from 6 to 48 years of age, investing 3 to 6 years in each of their calves.
“We’ve been able to look at the social systems of these animals,” said Wells. “We’ve learned that they live in a fish-infusion society… They don’t live in a family group like humans do.”
There are, however, certain basic components to their social system, Wells said, such as grouping by age or dynamics. In trying to determine what causes death, he explains that roughly 1/5 of the deaths cannot be determined due to the high temperature of the water decomposing the dolphin carcasses. A little over half of dolphin mortality, he said, is due to natural causes, but a little more than a quarter of their mortalities are caused by humans.
“Whether it’s entanglement in nets from boat strikes, entanglement in recreational fishing gear, ingestion of recreational fishing gear or entanglement in crab traps,” said Wells. “It’s these human-caused sources of mortality that we focus on as conservation scientists to try to understand how we can give the animals a better chance of thriving in their natural environment. One of the things that people sometimes don’t understand is that the dolphins don’t get to choose which threat they’re going to face at any given time.”
If anyone would like more information on the Dolphin Research Program visit their website at www.sarasotadolphin.org