Lagoon woes leading to displacement of dolphins
STORY
Times are tough for bottlenose dolphins in the Indian River Lagoon with high levels of disease and an unprecedented die-off in the northern part of the estuary over the past several months, and conditions seem to be getting worse.
Recently, Harbor Branch researchers spotted two dolphins known to inhabit the northern lagoon swimming near the Moorings, far outside their habitual range.
Harbor Branch’s dolphin research program discovered years ago that Indian River Lagoon dolphins live in three distinct communities – in the northern, central and southern parts of the estuary – with animals in each group staying in their native region from birth to death.
A displaced northern dolphin in south Vero waters is another indication of just how badly out of whack lagoon ecology has gotten.
Dolphin dorsal fins are nearly as unique as human fingerprints, and over the past 15 years, senior research associate Marilyn Mazzoil and her colleagues have compiled an extensive database of fin photos that enables them to keep track of dolphin births, deaths, social relationships and habitat ranges in the lagoon.
The group’s research results, which are published in peer-reviewed scientific journals, are essential for determining the nature and severity of threats to lagoon dolphins and for developing conservation policies to protect the long-lived, highly-intelligent animals.
“We have identified 780 distinct individuals in the lagoon since we started,” says Mazzoil, who can recognize dolphins by sight when their fins emerge from the estuary’s brackish water.
Researchers give the dolphin’s nicknames and many are old friends they have known for years.
“I tend to get most excited when we see the dolphins I have known the longest,” says Mazzoil. “They have fascinating life stories.”
Mazzoil says bottlenose dolphins have unique personalities that range from goofy and gregarious to much more reserved and stand-offish. Some females are careful, conscientious mothers while others are more lackadaisical.
In general, female dolphins, who have lived to be 35 in the lagoon, invest much time in preparing their calves to survive on their own in an environment that includes speeding motorboats and hungry sharks.
“The earliest we have seen them have babies is age seven,” Mazzoil says. “They keep their calves with them for two and a half to three years, before having another baby.”
An exception to that timeframe that illustrates the variability of dolphin behavior is a female known to Mazzoil and her colleagues who has a “mama’s boy” that’s stayed with her for more than six years. “She touches him with her fluke each time they dive,” Mazzoil says.
Working with Mazzoil in Harbor Branch’s Population Biology and Behavioral Ecology program are Program Director and Associate Research Professor Greg O'Corry-Crowe, Ph.D. and marine biologists Elisabeth Howells, Elizabeth Murdoch Titcomb and Elizabeth Hartel.
The program is funded by the Protect Wild Dolphins license plate, which Mazzoil helped get approved back in 1997 when she and fellow Harbor Branch researcher Stephen McCulloch founded the institute’s dolphin research program.
Mazzoil and McCulloch both started their careers handling captive animals, Mazzoil as a killer whale trainer at SeaWorld in Orlando, McCulloch capturing wild dolphins in the Keys while he was still a teenager.
When they shifted their focus to protecting wild dolphins and their habitat, the pair started a research foundation that merged with Harbor Branch after one year.
The marine mammal program they started at Harbor Branch includes four main components: photo ID, an on-call rescue team to help stranded or injured dolphins and whales, an annual medical exam of select lagoon dolphins to track their health, and necropsies of animals that have died to determine their age, physical condition and cause of death.
Mazzoil and the three Elizabeths in the photo-ID program operate out of ramshackle lab a few steps from the docks on Harbor Branch’s small boat harbor.
They try to survey the entire 157-mile stretch of the Indian River Lagoon each month identifying and photographing every dolphin they see to add another layer to their data base.
The database includes hundreds of thousands of dorsal fin photos arranged in an ingenious system that allows researchers to quickly match a new photo with existing records.
Besides a steadily accumulating knowledge base encompassing the overall lagoon population, there are in-depth files on many individual dolphins that may include results from one or more compressive physicals, geographical coordinates for dozens of sightings, information about when and where the dolphin was born and who its offspring are.
By seeing the same dolphins over and over again, year after year, researchers learn the limits of each animal’s habitat, which dolphins are the animal’s long-term associates and relatives and how they relate to each other. They can also track the dolphins’ health status and correlate disease with changes in water quality – foundational knowledge needed to inform intelligent conservation policy.
Mazzoil and her colleagues have made a number of startling and ecologically important discoveries since the late 1990s.
“We documented the first wild dolphin adopting an orphaned calf and have made many other unique findings on social behavior and structure,” Mazzoil says.
“We are the ones who determined that lagoon dolphins do not go out into the ocean. That really surprised us. We thought they would go in and out the passes, but they don't.”
As reported in a 2008 article in the journal EcoHealth, the Harbor Branch Researchers discovered that the 1,000 or so dolphins in the lagoon live in three distinct communities, one in the northern lagoon and Banana River, one in the central lagoon and one in the southern stretch of the estuary.
Individuals are born, grow up, hunt, breed and die within the 15-30 mile range of their home group, seldom if ever straying into the territory of an adjacent community.
“That was a huge finding that is significant because it allowed us to start correlating the health of the animals with conditions in their home ranges,” says Mazzoil.
The knowledge has taken on added importance this year as dolphins have begun to die at an unprecedented rate in the northern lagoon.
“More have died up there so far in the first five months of 2013 then usually die in a year in the entire lagoon,” says Mazzoil.
Because researchers know that the northern lagoon dolphins have a well-established history of staying in their home range, they can narrow their analysis of environmental factors that may be causing the deaths to that region.
So far the die-off remains a mystery even as it adds to the overwhelming evidence of environmental degradation in the estuary that has led to an outbreak of viral and cancerous diseases in marine mammals, mass manatee and pelican deaths, declining fish populations and the loss of most seagrass north of the 17th Street Causeway.
“We started seeing dolphins that were very skinny in December,” says Wendy Noke Durden, a marine biologist with Hubbs-SeaWorld Research Institute who is investigating the deaths. “Deaths were high in January and February and accelerated in March and are continuing. Nine dolphins died in March, nine in April and eight in the first three weeks of May.”
Many of the dead dolphins show signs of shark attacks, inflicted either before or after death.
On a photo-ID excursion in the middle of May Mazzoil and biologist Elisabeth Howells saw another sign of ecological disruption when they spotted a northern lagoon dolphin they call Reno near The Moorings.
“Reno has historically been seen in the southern end of the Mosquito Lagoon and the northern end of the Indian River proper,” says Howells. “She has never been seen as far south as Vero.”
If conditions have gotten so bad in the northern lagoon that dolphins are beginning to migrate to new ranges in a way never before seen, it could cause a host of new problems including over-fishing by dolphins that will exhaust their food stocks and territorial conflict between existing central lagoon dolphins and newcomers.
Besides Reno, who was traveling with an unidentified calf, Howells and Mazzoil saw 19 other dolphins during a two-hour cruise from Harbor Branch up to the Barber Bridge and back.
Despite all the challenges dolphins face in a badly polluted Indian River Lagoon, Mazzoil remains upbeat about their prospects.
“I am always optimistic,” she says.
