We have been studying the Sarasota dolphin community since 1970. Each dolphin has a life story.
By following individual dolphins over so many years, we’ve also come to know their families. We have followed Cathy through 5 generations.
Male dolphins tend to form alliances. One of the males, named Petey, has been quite successful with the lady dolphins.
A dolphin named Ginger needed help just to survive.
Each dolphin has a life story.
Cathy: Great-Great-Great Grandma
We have known Cathy since 1976. Much of what we know about Sarasota dolphins is mirrored in the lives of Cathy and her four subsequent generations.. Cathy was estimated to be 44 years old in 2010.
Dolphin calves usually stay with their moms for 3-6 years. Cathy’s family is unusual because two calves were orphaned at much younger ages: Bobby Jo at an age of 16 months, and Thrasher at age of 2 years. We were pleasantly surprised to observe that, despite their young ages, both survived.
As you can see in Cathy’s family tree, three of her descendants died from stingray barbs. Stingrays have been a growing source of mortality in Sarasota for dolphins in the last several decades.
Possibly, overfishing of sharks, which prey on stingrays, has led to greater numbers of stingrays. We’re not sure how dolphins come to be struck, but it likely happens when dolphins swim through very shallow water where they rub on the bottom. Stingrays tend to stay on the bottom, and only use their barbs defensively.
Cathy’s family tree also shows how vulnerable dolphins can be to boats. Cathy’s daughter Duckbill was struck by a boat as an infant, and we think that eventually was implicated in her early death.
Cathy also showed us how some dolphins can shift their core areas within the community home range over time. Early on, Cathy traveled mainly through the northern half of the community home range. In recent years, however, she and her family spend more time in the southern half (see map).
In this map, the two oldest dolphins, Cathy (FB43) and daughter FB37 emphasized the northern half of the community range in their early years. Later, Cathy and subsequent generations emphasized the southern half of the home range in their daily movements, with occasional visits to the north.
Cathy’s great-granddaughter Annie had her first calf 7 years of age. This is a young age for giving birth. As happens often to first-born calves, this calf (1251) did not survive its first year.
Reasons for the frequent loss of first-born calves may be physiological immaturity or a lack of experience of the mom, or the transfer of environmental contaminants in the mother’s milk.
The latest addition to Cathy’s family, her great-great grandson, was born in 2007. He was examined in the 2009 health assessment and pronounced in good health by the veterinarians. We see him regularly with his mother Annie during boat surveys.
Petey: Male alliances and reproductive success
Petey (FB10) was born in 1981 to Ms. Mayhem, and he became independent at 5-7 years of age. He later became part of a male alliance.
We first described the formation of long-lasting alliances of Sarasota males in the 1970’s. An alliance is formed when two male dolphins pair up, traveling together virtually all of the time.
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More than 90% of the male dolphins in Sarasota eventually become members of an alliance, with the first alliances formed shortly after reaching sexual maturity. Some alliances last for decades, usually ending only upon the death of one of the pair.
Petey’s first alliance with Wee Willie in 1988 lasted only a year. But his next alliance with FB46 lasted for 14 years, until FB46 disappeared in 2003. Petey formed an alliance a year later with FB36, and they are still usually seen together in the Sarasota dolphin community.
Why form an alliance? There are likely a variety of reasons. Perhaps because it reduces the risk of shark attack or aids in battles with other males. Teamwork also might make catching prey easier.
Perhaps of greatest adaptive value, male alliances seem to improve reproductive success. DNA paternity testing has shown that males in alliances are more likely to father calves.
And Petey has been very successful. DNA testing show that he has so far sired at least three calves, each from a different mother. Petey is one of the most reproductively successful male in the Sarasota dolphin community.
Ginger: Healthy After Rehab
On December 16, 2008 a newly independent, 3-year old dolphin stranded near the SDRP lab. Taken to Mote Marine Dolphin and Whale Hospital, she was nicknamed “Ginger” (short for Gingerbread) because she stranded so close to the holidays.
While in rehab, she was fed live pinfish, a common local dolphin prey species. Live local fish were fed to help Ginger have a smooth transition back into the wild. The fish were introduced each day without humans in sight, to keep Ginger from associating humans with food.
After two months of treatment, Ginger was healthy enough to release back into the wild. She was outfitted with a small radio tag, so SDRP researchers could monitor her closely for the next few months.
Ginger was released back into Sarasota Bay in front of a large crowd of well-wishers in February 2009. She even wowed the crowd with a few high leaps soon after release. This was a good sign that she had the strength to survive.
During 2 months of follow-up monitoring, she was tracked nearly every day. During that time she was seen behaving and feeding normally, in places she had been observed prior to stranding.
Since the end of radio tracking in April 2009, Ginger has been seen during regular dolphin surveys of Sarasota Bay. Her range has increased, and she has been observed interacting with other dolphins, including her mother and new sibling from time to time.
A health assessment was performed on Ginger in May 2010. This is the first time a rehabilitated dolphin has been evaluated by veterinarians after being returned to the wild. She was found to be in excellent condition and appears to have re-adapted quite well to life in the wild.
All photos © Sarasota Dolphin Research Program under NMFS permit #522-1785