The sudden appearance of a bottlenose dolphin mounding its back and flashing its dorsal fin at the surface is always an unexpected thrill. And when one is seen, more are almost certain to follow.

Some may emerge in unison within inches of each other, while others may be scattered hundreds of yards apart yet clearly moving as a group. Who can resist stopping whatever their doing to watch where they’ll come up next?

Bottlenose dolphins, or Tursiops truncates, are hardly unique to North Carolina. They occur in tropical and temperate coastal waters around the world. Their common occurrence close to shore probably makes them the most frequently sighted of all the world’s more than 80 species of whales and dolphins. Their widespread distribution, however, hasn’t prevented local interests from proclaiming special recognition to the dolphins in their area. This is a good thing, however.  It can help encourage local research and protection measures which are vital for conservation.

In North Carolina, for example, House Bill 598 filed in April 2019 would designate bottlenose dolphins as the state’s official marine mammal. Introduced by Reps. Bobby Hanig, R-Currituck, and Holly Grange, R-New Hanover, the bill won unanimous approval in the House and passed a first reading in the Senate, where it was then referred to committee. The North Carolina General Assembly is set to convene April 28, but some legislative committee meetings scheduled for this week have been canceled because of the COVID-19 pandemic.

Despite widespread distribution, bottlenose dolphins are divided into hundreds of discrete local and regional populations, or stocks, worldwide. Although the range of each stock typically overlaps at least one neighboring stock, each is biologically isolated to varying degrees by subtle social, ecological and behavioral differences. These differences reflect generations of experience learning about how to exploit the specific conditions in a given area. Consequently, stocks can differ widely in abundance, geographic range, food preferences, migratory patterns and other characteristics. But the loss of any one stock can leave a long-term gap in a species’ range and decrease its overall genetic and behavioral diversity.

Subdivided stocks

The National Marine Fisheries Service, or NMFS, the federal agency responsible for conserving most marine mammals in U.S. waters, recognizes 16 overlapping stocks of bottlenose dolphins between New York and southern Florida (S.A. Hayes et al 2019). Six, the oceanic stocks, occur primarily or exclusively in ocean waters, while 10 others are confined largely to specific inshore bays, sounds, and estuaries – the estuarine stocks.

The current subdivision of stocks is by no means a settled matter. Researchers at the NMFS Southeast Fisheries Science Center are developing techniques to identify genetic differences between the various U.S. bottlenose dolphin stocks and their work to date is promising. If successful, minute skin samples may soon be sufficient to identify which stocks individual animals belong to. This could result in some significant changes in the number or range of recognized stocks recognized along the Atlantic Coast.

As recently as the 1980s, East Coast dolphins were thought to be divided into just two stocks, an inshore and offshore stock. The more complex recognition of 16 stocks came to light as a result of recent studies using satellite telemetry tags and photo identification to track the movements of individual animals. And if current stock delineations further change significantly, it could lead to profound changes in conservation needs.

In North Carolina, photo-ID techniques were first applied to dolphins by Natural History Curator Keith Rittmaster at the North Carolina Maritime Museum and N.C. Division of Marine Fisheries Marine Mammal Stranding Coordinator Dr. Victoria Thayer, near Beaufort in 1985. Similar efforts around the state followed a decade later with Rich Mallon-Day working at the Nags Head Dolphin Watch on the Outer Banks, Dr. Laela Sayigh at the University North Carolina Wilmington and Dr. Andy Read at Duke University Marine Laboratory.

By the mid-1990s, scientists working to photo-identify bottlenose dolphins along the East Coast realized that, by pooling their local photo catalogues, a far more complete picture of dolphin movements and biology could be gained. Thus, in 1997, Kim Urian, a research analyst at Duke Marine Lab in Beaufort, cooperated with researchers and research organizations all along the East Coast to compiling single catalogue for all photo-identified dolphins along the Atlantic Coast

Initially funded by NMFS and still maintained by Urian, the result, the “Mid-Atlantic States Bottlenose Dolphin Photo-Identification Catalogue,” includes contributions from 37 researchers and research groups.  It contains more than 24,000 photographs of 15,400 individuals from the New York Bight to the Indian River in Florida. It includes 8,403 photographs of 5,424 individuals from North Carolina alone. Because most dolphins lack distinguishing marks or go unphotographed, and some identified dolphins have since died, the numbers represent an unknown portion of the total. And most are not assigned definitively to specific stocks, given limited sighting histories.

Based largely on these studies, five of the 16 East Coast stocks are found at least seasonally in North Carolina. Of the five stocks in North Carolina, two are estuarine and three are oceanic stocks. With the migratory patterns of each overlapping one or more adjacent stocks at different times of the year, North Carolina is one of the hardest areas on the East Coast to assign sightings or dead stranded dolphins to a particular stock.

One of the two estuarine stocks, the northern North Carolina estuarine stock is centered in northern parts of the state in Albemarle, Pamlico and Core sounds. Some of its members, however, have been seen as far north as the lower Chesapeake Bay, Virginia, in summer, and south to Wilmington or beyond in fall and winter. It currently numbers an estimated 782 dolphins.

The southern North Carolina estuarine stock is smaller. It occurs primarily in bays and sounds between the New River near Jacksonville and the South Carolina border, but some members have been photographed as far north as Core Sound near Beaufort in summer. There is no recent estimate of abundance for this stock, but photo-identification studies completed more than 15 years ago suggested it numbered fewer than 200 dolphins at that time. Individuals in both the northern and southern estuarine stocks occasionally pass through inlets traveling and foraging close to shore – generally within a few hundred yards of the beach.

The abundance and range of oceanic stocks tends to be greater than estuarine stocks, which is certainly true for the three stocks occurring at least seasonally off North Carolina. One – the offshore stock – ranges over the outer half of the continental shelf from Florida to southern New England and is by far the largest on the East Coast. It numbers some 75,000 dolphins.  Although occupying federal waters well beyond the state’s 3-mile jurisdiction, dead individuals from this stock sometimes wash ashore in North Carolina. Offshore dolphins tend to be larger and more robust than animals closer to shore and may even represent a separate species of dolphin.

The two other oceanic stocks off North Carolina are coastal stocks living over inner portions of the continental shelf generally between 3 and 40 miles of shore. Frequently, however, some of their members move to within a mile or less of the beach and will even poke into the mouths of inlets. Both coastal stocks migrate north in spring and south in the fall, but with different ranges they tend to occur off North Carolina at alternating times of the year.

The northern coastal migratory stock ranges from North Carolina in winter to New York in summer and is estimated to number more than 6,000 animals. The Southern Coastal Migratory Stock moves from northern Florida in winter to Virginia in summer and is thought to number about 3,700 animals. Thus, whereas the northern coastal stock is generally present off North Carolina in winter, the southern stock is present in summer. Both stocks, however, may be present off North Carolina in late fall and early winter.

Conservation issues

The bottlenose dolphin stocks in North Carolina currently appear to be stable and healthy.  Dolphins, however, are subject to human impacts. They can be injured or killed by entanglement in fishing gear and collisions with boats, and both pollution and disruption of natural behaviors can affect their health and reproduction, cause stress, and shorten their life spans. Such impacts can precipitate declines and even their disappearance in local areas. This is particularly true for small stocks, such as those in the state’s estuaries where exposure to human impacts is greatest. Assuring the stability and health of dolphin stocks in North Carolina therefore requires ongoing studies to monitor human-related injuries and deaths, track the abundance and reproduction rates of each stock, and assess the health of dolphins within stocks.

In this context, House Bill 598 is an important and worthy step. Although it authorizes no new funding or mandates for research or management, its formal recognition of bottlenose dolphins as a significant part of the state’s coastal ecosystem would increase public and scientific attention, and could encourage state, federal and non-governmental agencies and groups to use their own resources and abilities to help meet needs related to local bottlenose dolphin research and conservation.

With public support for House Bill 598 over the coming months in the form of letters to elected state representatives, it’s possible that bottlenose dolphins could be the official North Carolina marine mammal before the end of the year.

Second of two parts

Read Part 1

EMERALD ISLE — “Rare Manatee Seen in Outer Banks Marina” proclaimed a headline in a June 2018 edition of the Raleigh News & Observer. In recent years, reports of manatee sightings in North Carolina in the state’s media have become particularly notable not because of their rarity, but because of their increasing frequency.

This increase – particularly since 2010 – might be chalked up as yet another sign global warming enabling tropical species to expand their ranges further north. In this case, however, a more important factor may be successful recovery efforts in Florida that have enabled the size of the Florida manatee population to increase.

Now estimated to number some 8,800 animals, up from perhaps 1,000 to 2,000 in the early 1980s, there are simply more Florida manatees available to roam north as Florida’s winter chill gives way to warmer temperatures in spring.  Because manatees can’t tolerate waters colder than about 68 degrees for long periods, virtually all manatees in the southeastern United States, including North Carolina, retreat to Florida to overwinter.

Water temperatures throughout most of Florida also regularly dip to the low 60s or colder for weeks or at least days at a time in most winters. In some years these temperatures are reached even in southernmost Florida. Unlike areas farther north, however, the waterways in central and southern Florida have small, localized areas called “warm-water refuges” where water temperatures typically stay at or above 68 degrees during even the coldest winter days. These refuges rarely exceed a few acres in size, and are often no more than a few tens or hundreds of square feet.

Without warm-water refuges, even manatees in Florida would probably be unable to survive. All Florida manatees therefore learn to find and return into them whenever winter water temperatures dip into the mid-60s.

Manatees are so adept at detecting and following the most minute temperature gradients, Chip Deutch, a manatee biologist with the Florida Marine Research Institute, quipped that “manatees act like heat-seeking missiles” when cold weather sets in.

On the coldest days, up to 80% of all Florida manatees pack into about 15 major warm-water refuges to thermoregulate, or regulate their own temperature, and wait out passing cold fronts. Most refuges are natural springs or power plant outfalls that constantly discharge water 68-70 degrees or warmer.

In southernmost Florida, however, “passive thermal basins” also serve as refuges. These basins are generally smaller areas formed by local hydrological conditions that trap pockets of warm water for at least a few days, or areas with a surface lens of less dense freshwater that insulates a deeper layer of warmer, denser salt water.

Manatees also possess a truly remarkable talent for navigation. They act as if they have onboard GPS systems like those we use in cars to map routes and find the nearest gas station or restaurant. Once manatees find a good source of food, fresh water or warm water, their locations seem to be etched in their memory for future use whenever they happen to be in the neighborhood. Photo identification studies for example, reveal that most manatees faithfully return to the same warm-water refuges winter after winter despite widespread dispersion once water temperatures rise in spring.

The manatees’ inborn system, however, stores and recalls locations of important habitat features, such as warm-water refuges, grass beds, travel corridors and freshwater sources for drinking. These systems are programmed during the first year of life as calves follow their mothers. They enable manatees to trek 1,000 miles or more through murky mazes of channels and shoals, retrace their path within a span of a few weeks, and then repeat it all over again a year or more later.

For example, a manatee named Chessie, who was rescued in the Chesapeake Bay in fall 1994 and flown back to Florida, apparently made repeated visits to southern Virginia. Named after a legendary sea monster allegedly lurking in the famed Bay, Chessie was tracked moving back the Chesapeake Bay the following spring soon after being released into the wild with a satellite transmitter to monitor its movements. His tag unfortunately fell off before making his return trip to Florida, but his last confirmed sighting in August 2001 was made as he moved through the Great Bridges Lock in southern Virginia.

Lifelong ties to specific warm-water refuges, usually those first encountered with their mothers, effectively subdivide Florida manatees into four regional groups or “subpopulations.” Two subpopulations occur on Florida’s east coast – one along the Atlantic Coast south Cape Canaveral and one in the upper St. Johns River – and two on Florida’s west coast – one south of Tampa Bay and the other in northwest Florida around Crystal River. Manatees on the East and West Coasts, which are about equal in number, almost never move from one coast to the other. When they disperse from winter refuges in spring, most animals stay in Florida on their respective coast. However, depending on which coast they overwinter, a small percentage move out of state either north along the Atlantic Coast or west along the Gulf Coast.

Thus, all manatees seen in North Carolina are part of one or both of the two East Coast subpopulations. And because the St. Johns River subpopulation includes less than 20% of all East Coast manatees and tends to stay in the St. Johns River year-round, most, if not all of the manatees in North Carolina are probably seasonal emigrants from the Atlantic Coast subpopulation whose warm-water refuges extend from a power plant outfall in Cape Canaveral, Florida, south to thermal basins around Biscayne Bay (Laist 2005 and 2013).

Thus, the manatees seen each year in North Carolina have likely traveled some 600-800 miles from their overwintering refuges. Travel rates gleaned from manatee tracing studies suggest they could make this trip within two to three weeks.

What You Can Do

Boaters and coastal residents can make important contributions to manatee conservation. Collisions with boats cause 10-15% of all manatee deaths every year and virtually every Florida manatee sustains one or more nonlethal injuries from boat propellers and hull impacts during its life.

Many collisions can be avoided by alert, responsible boat operators. In addition, any action that could encourage manatees to approach people, boats or boating facilities should be avoided. Although seemingly benign, actions that habituate or reinforce manatee attraction to people or boats inevitably leads to situations that place animals at a higher risk of human-caused injury or death.

Precautions consistent with basic principles of safe boating and wildlife viewing can go a long way toward protecting manatees, including the following:

• Immediately call or text reports of injured, entangled, distressed or dead manatees to the North Carolina marine mammal stranding hotline: 252-241-5119.
• Before starting boat engines, check all around your boat to be sure no animals are present. If a manatee is seen, wait for it to pass and then follow a clear path at idle speed away from its location.
• When underway, wear polarized sunglasses and add “manatee footprints” to the navigation hazards you watch out for. Manatee footprints are circular surface swirls a few feet in diameter created by fluke stokes of animals swimming just beneath the surface.
• If you see a manatee or their “footprints,” slow to idle or slow speed and steer clear. Hitting a manatee at speed can cripple or kill the animal, disable your engine, damage the hull, and even injure passengers due to impact jolts.
• Never offer food to manatees.
• Never provide freshwater to manatees and turn off dock hoses not in use.
• Never attempt to touch manatees or approach them closer than about 50 feet.

You can also help scientists learn about manatees by reporting sightings.

In areas such as North Carolina where manatee studies are limited, public sighting reports are especially important for tracking population trends and detecting changes in habitat-use patterns.

Sightings should be reported by email Thayer at vicky.thayer@ncdenr.gov, or by calling or texting the state stranding hotline 252-241-5119.

Most important in sighting reports is accurate information on the time, date, location, number of animals seen, and contact information for the person making the report.

Other useful information would include a description of the animal’s behavior such as feeding, resting, milling around a dock or swimming, the direction of travel, presence of distinctive marks, like healed propeller scars, and if possible, good photos.

Photos showing distinctive scars or fluke notches are particularly valuable for identifying and tracking individual animals. Dead, injured or entangled manatees should be reported immediately to the hotline phone number.

If the manatee population continues to grow and pregnant females return with their calves teaching them of the region’s ample summer food supplies, North Carolina could become a significant summer feeding area for Florida manatees in the not too distant future.

Learn More

• Winter Habitat Preferences for Florida Manatees and Vulnerability to Cold

First of two parts

EMERALD ISLE – As the days lengthen, temperatures rise and the snow birds begin boating north along the Intracoastal Waterway, alert residents in coastal North Carolina just might spot another increasingly common sign of spring: The arrival of a few maverick manatees heading north from overwintering grounds in Florida.

Manatee sightings in North Carolina have been reported as early as April and May, but according to state Division of Marine Fisheries biologist Victoria Thayer, marine mammal stranding coordinator for central coastal and northern and central inland North Carolina, “… manatee sightings typically begin in June and continue through late fall.”

These gentle, yet ponderous creatures, which are roughly the size and weight of an Americana bison, are members of a subspecies of West Indian manatee called the Florida manatee, Trichechus manatus latirostris.

As a whole, the species is found from northern Brazil to the southeastern United States. Manatees were drastically reduced in number by centuries of unrestrained hunting before the 1900s. With recovery still in doubt due to reasons that vary in different parts of its range, the species is now listed as “threatened” under the U.S. Endangered Species Act.

Scientists recognize two distinct subspecies of West Indian manatees. One, the Antillean manatee, Trichechus manatus manatus, occurs in the Greater Antilles and along the Atlantic coasts of Central America and northern South America. A management plan for the subspecies in this region prepared in 2010 by the United Nations Environment Program, or UNEP, found a few signs of recovery in parts of the Caribbean, but concluded manatees may still be declining throughout much its range. The other subspecies, Florida manatees, occur only in the southeastern U.S.

At its low ebb in the late 1800s, perhaps a hundred Florida manatees still survived. In 1893, however, the State of Florida mercifully banned manatee hunting in what was one of the first wildlife protection laws ever adopted in the United States.

Since then, the subspecies has eked out a slow recovery despite high levels of human and natural mortality. At the end of 2018, a new abundance estimate of 8,810 animals was announced by scientists with the Florida Wildlife Research Institute and the U.S. Geological Survey.

The new estimate is an encouraging sign of recovery, yet with hundreds of manatees found dead every year in Florida, including more than 820 in 2018 alone, abundance trends could shift quickly. The leading causes of deaths in Florida are collisions with boats, toxins from red tides, and periodic cold stress die-offs.

Because cold temperatures can be lethal to manatees, they do not occur year-round north of Florida. A 2002 study led by Greg Bossart, a veterinarian then with the Harbor Branch Oceanographic Institute in Florida, identified two types of cold stress syndrome affecting manatees: acute and chronic.

Acute cold stress caused by exposure to temperatures colder than about 50 degrees Fahrenheit can kill manatees within hours or days; chronic cold stress results from exposure to temperatures between the mid-50s to 60 degrees for periods of a few weeks or more.

In spring and summer, however, as temperatures rise, some manatees begin to stray north. And as herbivores eating as much as 150 pounds of aquatic plants per day, roughly 7-15% of their body mass, they do quite well in warm months of the year in North Carolina and other mid-Atlantic States feeding on abundant beds of eel grass, widgeon grass and shoal weed.

Manatee Sightings in North Carolina

A handful of early North Carolina sightings compiled by Frank Swartz in 1995 suggest that the presence of manatees in the state in summer is not a new phenomenon, but since the 1970s, they have become increasingly common. At least a few sightings, and up to a dozen or more, are now reported annually.

In 2010, Erin Cummings, at the time a master’s student at University of North Carolina Wilmington, started a manatee sightings database for North Carolina and Virginia by compiling reliable records from various sources dating back to the 1990s.

From 1998 through September 2012, Cummings and her colleagues found reports of 98 sightings and nine strandings of dead animals in North Carolina. Except for 2006, when no reports were found, they documented at least one sighting every year in North Carolina, with a clear increase beginning in 2010.

In 2012 alone, there were 30 sightings. Subsequent reports haven’t been analyzed, but they do appear to confirm the increase. In 2018 there were at least 17 reports, including one involving four animals in Lockwood Folly River north of Oak Island in mid-August. Most sightings are from June through October.

For some northbound animals, North Carolina is probably far enough. Here they can linger to feed in the expansive systems of sounds, estuaries and rivers. Most are seen within a few miles of the Atlantic Intracoastal Waterway near Wilmington and Beaufort, but this probably reflects the greater number of eyes on the water in those areas, rather than true manatee distribution. Some poke far up coastal rivers and have been seen nearly 60 miles up both the Cape Fear and Neuse rivers. Others are occasionally spotted in the ocean close to shore possibly hopping between inlets.

Of course, all northbound manatees don’t stop in North Carolina.  Cummings found a slightly larger number of sightings in Virginia, 112 sightings, but those records dated back seven additional years to 1991. Some manatees continue even farther north. In September 2016 a new northern record was logged when a manatee was seen off the southern arm of Cape Cod in Dennis, Massachusetts.

By October, coastal water temperatures along the mid-Atlantic states begin to fall quickly into the low 60s or colder. Manatees that haven’t already begun moving south to Florida need to do so with haste or face a dim survival prospect due to cold stress. A slight uptick in North Carolina sightings in October could reflect an influx of manatees hurrying south from areas farther north. Manatees suffering chronic cold stress become lethargic, form white skin patches, reduce feeding and become emaciated and eventually die by sepsis or cardiac arrest.

In 2018, Kathy Ruge, a resident living on Bogue Sound, was amazed to find a manatee off a community dock Nov. 13 in Bogue Sound. She photographed it milling at the surface. Like many Florida manatees, it had a distinctive old propeller scar on its back.

Ruge said she “had never seen a manatee before, but somehow I sensed it was in trouble and that it was a pregnant female.” Ambient water temperatures had already dropped to the low- to mid-60s and the animal already may have been experiencing early stages of cold stress.

It apparently was trying to warm itself in the sun in a protected corner of the marina. Two other reports in November along Bogue Sound probably involved the same animal.

A manatee believed to be the one photographed by Mrs. Ruge was found dead on Dec. 19 in Beaufort. A necropsy by Dr. Craig Harms, veterinarian and director of the Marine Health Program at North Carolina State University Center for Marine Sciences and Technology, or CMAST, in Morehead City, and Dr. Thayer revealed that it was indeed a pregnant female that likely died of cold stress.

Another manatee likely killed by cold stress also was found that same day off the lower Neuse River. Thayer noted that strandings of dead manatees in the state “typically occur between October and January when temperatures are cold enough to be lethal.”

The U.S. Fish and Wildlife Service, the lead agency responsible for manatee protection, has neither the funding nor local staffing to respond to most distressed manatees outside of Florida. Doing so is a major undertaking requiring considerable funding, mobilizing an authorized rescue team, equipment and facilities for transport and captive care, and finding animals in places suitable for capture and transport.

On rare occasions, however, manatees lingering too long in northern states have been rescued. The animal found off Cape Cod in October 2016 was successfully rescued. It too proved to be a pregnant female. Fearing she was too far north to make her way back to Florida alive, a rescue team formed by the International Fund for Animal Welfare was able to capture and transport it to the Mystic Aquarium in Connecticut for observation and treatment. After a few weeks, she was flown back to Florida by the Coast Guard and released back into the wild in early November.

Next: Why there are more manatees and what to do when you see one

Learn More

• Influence of power plants and other warm-water refuges on Florida manatees