“Backcountry” is Home to Protected Sea Turtles

Due to low population numbers and threats to survival, loggerhead, green 

and hawksbill sea turtles are protected under the Endangered Species Act. 

All three species have been observed in the backcountry waters of the Key 

West National Wildlife Refuge. Refuge beaches have long been known as 

turtle nesting sites for green and loggerhead turtles, but in recent years 

the value of open waters to marine turtles has also been recognized and 

documented. The first evidence of sea turtles using refuge waters as foraging 

grounds came from satellite studies that tracked green turtles nesting on 

Florida’s east coast and panhandle, and in Mexico’s Yucatan Peninsula to 

refuge waters after the nesting season. 

Scientists Investigate Foraging Sea Turtles 

In 2007, using grant funds awarded by the U.S. Fish and Wildlife Service, 

scientists from Inwater Research Group and Florida’s Fish and Wildlife 

Research Institute continued their marine turtle research in the open 

waters of the refuge. To systematically document turtles in the water, 

scientists observed them from a tower on a small boat while traveling along 

random survey lines called transects. During these timed trips, turtles 

were identified and counted and their GPS positions were recorded. This 

survey method, which reported the number of turtles per kilometer of transect, allowed scientists to compare the abundance 

of turtles in one location to another. Some turtles were captured by scientists and brought aboard the boat where they were 

identified, weighed, measured, photographed and flipper tagged. Before releasing a turtle, blood was drawn for genetic studies. 

During the three-year study, 550 loggerheads, 1057 greens and 23 hawksbills were 

sighted on transects in the refuge and surrounding waters. A total of 353 sea turtles 

were captured (including 51 recaptures), tagged and released.

Refuge Provides Valuable Habitat for Large Loggerhead Turtles

The majority of sea turtles captured in this study were loggerheads and most of 

these were large subadults approaching maturity. Compared to other similar study 

sites in Florida, the refuge, along with Florida Bay, had higher proportions of large 

loggerheads. The coastal waters of the refuge and Florida Bay appear to provide 

important developmental habitat for individuals approaching maturity and for adults 

foraging between reproductive migrations. Like other sea turtles, loggerheads may 

make long migrations in between nesting seasons. Based on recapture data, most 

loggerheads had relatively small home ranges while in refuge waters. Some home 

ranges were maintained over months and years of residency, an indication that habitat 

in the refuge provides the right prey and in abundant quantities. 

Loggerhead sightings from the boat, mostly of subadults, were calculated at 

0.45 - 0.50 turtles per kilometer of transect, depending upon the region of the 

refuge. Turtles were more abundant in relatively shallow mixed hard-bottom habitats. 

Loggerheads use their strong crushing jaws to feed on bottom-dwelling invertebrates 

such as queen conch and spiny lobster.

 Sea Turtles in Refuge Waters

Florida Keys National Marine Sanctuary

http://floridakeys.noaa.gov/

Key West National Wildlife 

Refuge was established by 

President Theodore Roosevelt 

in 1908. Managed by the U.S. 

Fish and Wildlife Service, the 

refuge contains 200,000 acres 

of seagrass meadows, 

hard-bottom, sandy bottom 

and shallow coral reef habitats 

and 2,000 acres of remote 

low-lying mangrove islands. 

These uninhabited islands are 

designated wilderness under 

the Wilderness Act of 1964 

and are managed to preserve 

their natural character. 

www.fws.gov/nationalkeydeer/

keywest/

A hawksbill turtle forages in backcountry waters. 

Photo: Inwater Research Group
Larger Green Turtles Observed Feeding in Herds

Green turtles feed on seagrass in shallow coastal waters and are the only sea turtles that are strictly herbivorous as adults. In this 

study, greens were most frequently sighted in mixed habitats where sponge and hardbottom communities were near seagrass 

pastures. Juveniles were seen resting under sponges between foraging excursions. The highest abundances of greens were found 

around the Marquesas Keys, 1.21 turtles per kilometer of transect, and west of the Marquesas Keys, 1.61 turtles per kilometer 

of transect. 

Juvenile greens were observed feeding in the shallowest 

of waters where they were better protected from large 

predators such as sharks. Adult and subadult greens were 

observed foraging in small herds in deeper waters west 

of the Marquesas Keys. Herding may help protect turtles 

from large predators, especially when reef habitat is not 

available to offer shelter. In Florida, scientists rarely observe 

adult and sub-adult greens outside of the breeding season 

and this study is the first to document herding behavior 

among green turtles. The 34 adult and subadult greens 

captured in this study represent only a small portion of the 

number of greens found on this foraging ground, which is 

estimated to hold over 400 animals at any given time. In 

all other areas of the refuge only juveniles were captured. 

Juvenile greens seem to have relatively small home ranges; 

all recaptured individuals were found within one kilometer 

of their original capture location.

Backcountry is Developmental Habitat for Young Hawksbills 

Because Florida represents the northern extent of their range, hawksbills turtles are very rarely observed in Florida waters. 

However, the refuge contains a relatively high density of hawksbills and is one of only three sites in Florida where they are being 

studied. The backcountry appears to be an important developmental habitat for younger hawksbills. Juveniles use the shallow 

waters within the Marquesas Keys for foraging and reduced predation risk much the same as greens. In this area, hawksbills were 

seen resting or foraging for sponges (a key component of their diet) among hard-bottom and seagrass habitats. The most important 

area for hawksbills may be reef habitat in the northern part of the refuge where the highest density was measured, 0.11 turtles 

per kilometer of transect. The 82 turtles captured in this study ranged from juvenile to subadult. No adult animals were seen or 

captured. A total of 17 hawksbills were recaptured, some multiple times over months and years, indicating they have a high level 

of site fidelity to habitat in the refuge. 

Many Turtles in Refuge Waters Originate Elsewhere

According to genetic analyses conducted on captured individuals, most loggerheads were hatched from rookeries in the 

southeastern United States, Cuba, and Mexico and most greens came from rookeries in Florida, Mexico and Costa Rica. Sea turtles 

are thought to return to their beach of origin to nest. Two of the ten adult female greens captured in the refuge were later found 

nesting on beaches on the Yucatan Peninsula in Mexico and a third had nested in Costa Rica before being captured, emphasizing 

the international importance of this foraging ground to green populations. Nesting of hawksbills in Florida is rare and may explain 

why no adult animals were observed. Genetic analyses on captured hawksbills shows that they came from nesting rookeries in 

Mexico, Puerto Rico and Cuba. 

Protections Are Important to Survival of Marine Turtles

Backcountry open waters with expanses of seagrass and mixed hard-bottom habitats are important foraging grounds for various 

life stages of loggerhead, green and hawksbill turtles. Survival of these endangered and threatened species depends upon healthy 

young and sub-adult turtles surviving into adulthood. Even the smallest disruption by people or vessels approaching too closely 

can interfere with foraging. Changes in habitats, sea-level rise on nesting beaches, impacts from fishing gear and pollution are 

also threats to the survival of sea turtles populations. Prohibitions on operating personal watercraft, airboats, and hovercraft 

in the refuge and no-entry and buffer zones help shield turtles from human disturbance. Such restrictions also protect critical 

shallow water seagrass meadows from impacts that degrade habitat quality and affect sea turtle foraging and survival success. 

Principle Investigator: Michael Bresette, Inwater Research Group

Written by: Nancy Diersing, Florida Keys National Marine Sanctuary

Publication Date: February 2013

Scientists search for sea turtles in refuge waters from a small boat.

Photo: Inwater Research Group