Category Archives: Wildlife Research

Monitoring Suburban Florida Sandhill Cranes

By Tim Dellinger

The Florida sandhill crane (Antigone canadensis pratensis) is one of five sandhill crane sub-species found in North America.  Florida sandhills are non-migratory and range from southeastern Georgia to the Everglades.  The current population estimate is around 4,600 birds and it is state-listed as Threatened in Florida.

Like other crane species, Florida sandhills need wetlands as well as uplands.  Wetlands such as shallow depression marshes and lake edges are used for nesting, foraging, and roosting.  Uplands with low vegetation, such as private ranchland and dry prairie, are used for foraging and loafing.  Both habitat types are equally important to cranes.  Unfortunately, wetlands are often drained and open uplands bulldozed to make way for roads, shopping malls, and subdivisions.  Remarkably, however, some cranes are remaining in or moving to urbanized areas and living among us.

Staff banding and tagging a Florida sandhill crane captured in a strip mall parking lot in Seminole County.

In 2017 we began a project examining how Florida sandhills are using urbanized areas.  We are currently tagging adult cranes with cellular GPS transmitters in suburbs and developed areas.  The transmitters collect GPS locations at 30-minute intervals and are uploaded to us daily.  We are also tagging Florida sandhills in rural and conservation areas to help us better understand survivorship, productivity, and habitat use along the urban gradient.

Preliminary data show that some urban cranes solely inhabit suburban or developed areas.  They use suburban yards, grassy roadsides, golf courses, and open areas around colleges and hospitals as uplands, and retention ponds or lake edge for wetlands.  However, most urban cranes regularly moved between rural areas or conservation lands to suburban areas to meet their daily needs.  Preliminary movement data for Florida sandhills tagged on conservation lands show that all individuals use some man-made habitat daily, either a mowed area near a road, a yard with a bird feeder, or improved pastureland. We will continue to tag cranes during 2019.

Diamondback Terrapin Status Assessment

By Traci Castellón

The diamondback terrapin (Malaclemys terrapin) is a once common estuarine turtle that experienced serious declines a century ago and has declined further in recent decades due to numerous pressures including habitat loss and drowning in crab traps. The Florida coastline represents approximately 20% of the species range and is home to five of seven subspecies, three of which occur only in Florida. However, little is known about the status and distribution of diamondback terrapins in Florida.

Ornate diamondback terrapin (M.t. macrospilota)

With funding from a State Wildlife Grant, FWRI is collaborating with partners statewide to conduct a biological status assessment of the diamondback terrapin in Florida. The project includes population assessments in three locations with known terrapin populations (Banana River, Florida Bay and the middle Florida Keys), and, where possible, we are also helping facilitate population assessments and surveys by partners elsewhere in the state.

Another major component of the work is collection of tissue samples from terrapins statewide for a genetic analysis to assess validity of the currently recognized subspecies taxonomy and, where possible, to conduct population-level genetic analyses to assess effective population sizes, gene flow and possible signs of inbreeding depression. Other efforts include gathering and consolidating existing data from partners to update the known distribution of terrapins statewide and using these data to develop a spatial model to quantify habitat availability. Finally, we will estimate the magnitude of past and future population reductions based on historic and projected future habitat losses.

East coast Florida diamondback terrapin (M.T. tequesta)

To date we have developed numerous partnerships, mapped > 5,500 individual sightings, collected > 300 tissue samples for genetic analysis, completed one season of mark-recapture work in the Banana River, and will begin fieldwork in Florida Bay and the Florida Keys in November 2018.

Major partners include Eastern Florida State College; Sanibel-Captiva Conservation Foundation; the US Geological Survey’s Wetland and Aquatic Research Center; University of Florida’s Department of Wildlife Ecology and Conservation, Florida Sea Grant Extension, Nature Coast Biological Station, and Florida Museum of Natural History; Florida Department of Environmental Protection’s Indian River Lagoon and Tomoka Marsh Aquatic Preserves; North Florida Land Trust; Florida Audubon; Flagler College; Brevard Zoo; and FWC’s Fisheries Independent Monitoring, Habitat and Species Conservation Section, and Florida Keys Wildlife Environmental Area; as well as many dedicated volunteers, students and citizen scientists.

Ornate diamondback terrapin (M.t. macrospilota)

Please send diamondback terrapin sightings to Traci.Castellon@MyFWC.com.

Light Pollution and Sea Turtle Hatchling Orientation

By Shigetomo Hirama

Sea turtles are long-lived animals that utilize multiple developmental habitats. In all of the habitats, sea turtles encounter with various threats. Although some are naturally occurring (at least they seem to be), the majority of threats are caused by human. These anthropogenic threats in-water habitats include: fisheries’ activities, oil spills, debris ingestions, debris entanglements, boat strikes, dredging, and direct harvesting. On the beach, beach driving, artificial lighting (light pollution), armoring (sea walls, rock revetments, and other infrastructures), oil spills, and egg poaching are threats to nesting and hatchling turtles. Among these threats on the beaches, the installment of armoring structure – sea walls, rock revetments, and other infrastructures – are probably the most important threats, considering sea level rise as a consequence of climate change. Armoring structures are known to increase speed of erosion and may cause permanent loss of beach sand. Although it may not be as important, artificial lighting also is significant threats to the turtles. The artificial lighting differs from the armoring in terms of solving the issues. Coastal armoring, such as a sea wall, is difficult to remove once it is placed; however, we can change light bulb or retrofit light fixtures relatively easily. Through the present project, we provide valuable information to stakeholders to reduce hatchling mortality and increase chance of hatchlings’ survivorship.

Playalinda Beach. An example of a beach with no light pollution.

Artificial lighting alters natural illuminant environment and impacts behavior of wildlife. Nocturnal animals such as bats, moths, and some species of birds, are more susceptible to light pollution than others. Sea turtle hatchlings crawl toward ocean using the visual cues immediately after emerging from sand. The hatchlings disorient on the beach if the intensity of artificial light is relatively high and may never enter the ocean.

Cocoa Beach. An example of a beach with moderate to severe light pollution.

We have been quantifying accuracy of hatchling orientation in over the 20 Florida beaches in past five years. Hatching orientation is one of the subjects of sea turtle biology that has been studied well. Surprisingly, no known work has provided the benchmark orientation data that were collected at a natural beach and compared with the information that were collected at the beaches with varying levels of light pollution. The results of present project showed the accuracy of hatchling orientation varied widely depending on the beaches. The quantitative data of the project are currently in process of publishing in a peer-reviewed journal. In the present article, I provide photographic images that were taken by same camera, setting, and lens at the beaches with no (Playalinda), moderate to severe (Cocoa Beach), and severe (Miami Beach) light pollutions. We hope the data we provide would guide to take practical actions to reduce light pollution.

Miami Beach. An example of a beach with severe light pollution.

Gopher Frog Monitoring Project

By Aubrey Greene

The gopher frog is currently being considered for federal protection under the Endangered Species Act. While the gopher frog has experienced serious declines throughout the rest of its range, Florida currently represents a stronghold for the species. Consequently, the gopher frog was delisted as a state-designated Species of Special Concern in January 2017. As a part of the delisting process, a state species action plan was developed for the gopher frog. This action plan calls for the development of a statewide monitoring program for the species. Before the species was delisted, we began a pilot study to increase our understanding of species detection and wetland occupancy rates, as well as to determine the best methodology for a long-term gopher frog monitoring program.

Surveys for the gopher frog monitoring project started in Fall 2015. This project uses seasonal dipnet surveys and frogloggers (automated frog call recorders) to track the status of gopher frogs in 100 wetlands over time. Additional wetlands are also surveyed as time allows to locate new breeding wetlands and track the status of the species in additional known breeding ponds. During FY 2017-18, we surveyed 114 ponds in 22 counties on 29 public or conservation lands for gopher frogs, finding tadpoles in 72 ponds in 21 counties on 24 public lands. These surveys discovered one previously unknown gopher frog breeding pond and observed breeding for the first time in decades in some previously known ponds. Many of the “rediscovered” observations were made in the months following Hurricane Irma, which filled most of the study ponds.

An image of a sonogram of a gopher frog call.

As the data collection phase of this project comes to a close at the end of 2018, in-depth data analyses will begin. Froglogger recordings are already being analyzed using software that recognizes the specific call signature of the species. Unfortunately, this is a very long process due to the large amount of data collected over the three-year project. Dipnet and froglogger data will be analyzed to determine the annual and seasonal patterns of wetland occupancy in each region of the state, as well as the effects of different variables on species detection and wetland occupancy. We will also examine data from both methods to make recommendations about the most efficient sampling methods.

Wrapping Up the Statewide Reddish Egret Survey

By Andrew Cox

The reddish egret (Egretta rufescens) is North America’s rarest heron and is state-listed as Threatened in Florida. In 2016 we visited 305 coastal islands during the first statewide survey of the species to document its distribution, estimate Florida’s population size, and learn more about its nest-site selection patterns. In 2017 we attended to the less glamorous side of our work – sitting at our desks, crunching numbers and writing.

Reddish egrets were primarily concentrated in four areas of Florida: in and near Merritt Island National Wildlife Refuge, Florida Bay, the Lower Keys, and the Tampa Bay area south to Marco Island. The species has continued to slowly expand northward on the Gulf coast, with nesting occurring in Cedar Keys National Wildlife Refuge. There were an estimated 480 (95% CI: 375–606) nesting pairs at the 58 sites where birds we found birds. The largest colony we found had 23 nesting pairs, which is fewer than the three largest colonies documented in Florida Bay during 1978. Half of all colonies had 3 or fewer pairs.

Reddish egret foraging behavior can be something of a spectacle as birds move throughout tidal flats and other shallow estuarine waters in a graceful, high-energy pursuit of prey. Foraging habitat is probably the largest limiting factor for reddish egret populations, and our nest-site selection analysis confirmed that it was the most substantial predictor of occupancy and abundance of nesting reddish egrets. These results confirm the importance of incorporating foraging habitat into our restoration planning and highlight the need to understand how the shallow flats upon which reddish egrets rely will be affected by sea-level rise.

The photo accompanying this article was taken by Anne Macias. Anne was a retiree in Bonita Springs and a strong advocate for Florida’s birds. She took great pride in the colony of nesting wading birds in her neighborhood and raised awareness of their importance within her community. Our jobs are made that much easier by people like Anne. Anne unfortunately passed away earlier this year and will be deeply missed.

Florida Bonneted Bat Roost Selection: Implications for Conservation

By Elizabeth Braun de Torrez

The Florida bonneted bat (Eumpos floridanus), which occurs only in Florida, is federally endangered and extremely rare. These bats can traverse extensive areas to forage but their distribution may be restricted by the availability and security of roosting sites. However, we know very little about what types of natural roosts the bats use or whether tree roosts are readily available across the landscape. In our current study, we are working to identify and characterize previously unknown roost locations in conservation areas across southwest Florida. This information will allow us to protect existing roost structures and to develop guidelines for conserving or enhancing roosting habitat for this species.

Building upon research started with the University of Florida, we are using a combination of acoustic surveys, mist netting and radio-telemetry. Florida bonneted bats are notoriously difficult to capture in mist nets due to their high-altitude flight, and prior to our recent research this species had only been captured once away from known roost sites. Using a technique we developed involving an acoustic lure that broadcasts conspecific social calls to attract this species to nets, we now have the ability to capture free-flying individuals, attach radio-transmitters and track them back to unknown roost sites using radio-telemetry.

Florida bonneted bat with VHF radio-transmitter attached to break-away collar.

To capture bats, we erect a triple high mist net system (9 m high) coupled with an acoustic lure. Upon capture, we identify the individual’s species, sex, reproductive status and take standard measurements (e.g., mass, forearm length). We also collect a 4mm wing biopsy and guano sample for genetic and diet analysis. For adult, non-pregnant Florida bonneted bats, we secure a VHF radio-transmitter attached to a break-away collar and track the bats to roost structures using a combination of aerial and ground-based radio-telemetry. Due to the suspected distance that these bats are capable of flying between foraging areas and roost sites (ca. 25 miles) and the challenges of navigating throughout the south Florida terrain, aerial telemetry is essential to locate roost sites!

Once we locate a potential roost, we verify occupancy and colony size by counting the number of Florida bonneted bats that emerge around dusk, and measure characteristics of the roost tree (e.g. height, size and orientation of roost opening). We also measure characteristics of the surrounding vegetation (e.g., tree density, canopy height, canopy cover) in a plot around the roost tree and at four random tree plots.

Royal palm snag in Fakahatchee Strand Preserve State Park containing 80 Florida bonneted bats. This is the largest known colony for this species.

We are in the process of compiling data from natural roosts that we have located, in conjunction with our research partners, over the last several years. In total, we have located 17 roost trees, with 5 new roosts located in 2018. The roosts include enlarged woodpecker cavities, cavities formed from decay, and spaces under loose bark, and they occur in live and dead long leaf pine, slash pine, royal palm and cypress trees. Colony sizes range from 1 individual to a new record of 80 bats in a recently discovered royal palm roost in Fakahatchee Strand Preserve State Park in May 2018. Of these 17 roost trees, 6 have since been damaged or destroyed by fire or hurricanes. Ultimately, we will use the data collected on new Florida bonneted bat roost structures to examine patterns of roost site selection relative to a variety of local and landscape-scale variables, and make appropriate habitat management recommendations.

Long Distance Movements by Female Bears

By Walter McCown

FWRI bear researchers began efforts to develop a demographic profile of bears in the Apalachicola subpopulation in May 2016.  We have, thus far, placed Iridium satellite collars on 37 adult female bears to document survival rates, the age of first reproduction, the number of cubs produced, and the interval between litters.  Additionally, each spring we place VHF collars on cubs in the den and monitor them several times a week to document their survival rate.  While these demographic profiles will enable us to construct a population model useful for the management of this subpopulation of bears, the presence of a satellite collar programmed to acquire locations every two hours affords us interesting insights into these bears.

One intriguing aspect of bear behavior occurs during the fall when bears increase their normal food intake from about 8,000 calories (kcal) per day to approximately 20,000 calories per day, resulting in an increase of their body weight by approximately 1.5 kg per day.  This behavior, known as hyperphagia, creates stores of energy in the form of fat and is an adaptation by bears to the lack of food during the winter.  Because bear foods are normally isolated in time and by space, bears may wander widely in the fall and spend up to 20 hours per day eating.  Although the list of food items consumed by Florida bears is rather lengthy (over 100 items) and diverse (bromeliads to walking sticks), acorns and palmetto berries are dominant fall food items in most subpopulations.  When these food items are abundant bears do well and have smaller home ranges.  When these items are more scarce, bears must make greater movements to obtain the calories necessary to survive the winter.

In fall 2016 we noted movements of several bears of 20-30 km into remnants of coastal scrub habitat where they fed on acorns.  In fall 2017, when acorns were apparently not as abundant, bears moved similar distances but further inland to forage in stands of hardwoods along area creeks and rivers.

Interestingly, in fall 2017, bear F605 moved from her home range in Tate’s Hell State Forest near Carrabelle, to private land near Hosford, Florida.  This 12-year-old female accomplished this trek of approximately 58 km (as the crow flies) with her three 8-month-old cubs in only three days (see top photo).  Subsequently, she remained near Hosford all winter, did not make any more noteworthy movements, and successfully raised all three cubs (see map below).

Locations of female bear F605 and three cubs October 17-19, 2017 (click to enlarge).

Bear researchers are frequently impressed with how black bears adapt to their environment and changing conditions.  However, we are bewildered with their ability to somehow know that conditions in distant locations are superior to those in their current use area.  Yet, it is abundantly apparent they do know.  In previous studies, Florida researchers noted lengthy fall movements by bears in Big Cypress during an apparent palmetto berry failure and in Ocala when a drought caused both oak and palmetto fruit production to fail.  Nonetheless, the trek by F605 that we documented was an impressive one for a female with three cubs.

Songbirds in the Salt Marsh: Living on the Edge

By Amy Schwarzer

Two subspecies of little brown songbirds, the Worthington’s marsh wren (Cistothorus palustris griseus) and the MacGillivray’s seaside sparrow (Ammodramus maritimus macgillivraii), call the salt marshes of northeast Florida home. Both subspecies are salt marsh obligates, confined to the marshes near the mouths of the region’s rivers. These birds, which used to range from the state line to Volusia County, have seen their distributions contract until the most recent surveys in 2000-2001 only found breeding individuals north of the St. John’s River. The range contractions led to a state listing of Threatened for the Worthington’s marsh wren, while the MacGillivray’s seaside sparrow has been petitioned for federal listing.

In 2014-15 we conducted point counts both north and south of the St. John’s River to estimate occupancy rates and abundances of both species. We found no signs of repatriation into the previously abandoned southern areas, but no further range contractions north of the river. Both species preferred higher elevation patches in the saltier smooth cordgrass marshes over the neighboring brackish black needle rush marshes, and had increased occupancy rates and abundances farther from upland edges.

From 2015-2017, we monitored 996 wren nests and 123 sparrow nests at seven study plots to determine which habitat and nest features affected nest survival rates.  Study plots were picked based on our point count data and represented high, medium, and low densities of wrens and sparrows. Most singing male sparrows appeared to be unpaired at all but one site, which suggests that there is a sex ratio imbalance in the region. Both wrens and sparrows experienced high rates of nest loss, with evidence pointing to predation as the main cause. Yet daily high tide height most strongly predicted the probability of nest failure for both species, though we saw limited evidence of nest flooding for sparrows and even less for wrens, which nest comparatively higher off the ground in taller grasses.  It may be that extreme high tides concentrate predators in the higher elevation areas of the marsh where the birds tend to nest.

In the last component of our study, we radio-tagged and tracked 50 wren fledglings to look at post-fledging survival. Post-fledging survival was also low compared to similar songbird species, though fledglings that were heavier at the time of tagging survived much better than lighter birds.  The causes of fledgling mortality are unknown, but we confirmed at least one predation event when we tracked one of our transmitters to the belly of a corn snake!

Though analyses of the project’s data are on-going, it has become increasingly clear that these subspecies have a tenuous grasp on survival in northeast Florida, with both low nest survival and low fledgling survival.  While the birds are not yet losing many nests to flooding, they seem sandwiched between the uplands and the rising seas, with high predator concentrations suppressing their reproductive potential.  We intend to synthesize our count and demographic data to identify habitat features that best support wrens and sparrows and to share this information with local managers, hopefully leading to management and restoration efforts that will alleviate some of the pressures these little brown birds face.

Assessing Mercury Concentrations in Alligator Populations

By Alligator Research Staff

The American alligator seems, in some ways, to be one of those perfect species. It has persisted for eight million years with little change. It’s a long-lived (40-60 years) species with high adult survival and a high reproductive potential which helped it recover from once being on the endangered species list. Alligators are also a desired target of hunters for their meat and the value of their hides. And as an apex and keystone species, they play a notable role regulating prey populations and modifying their own environment in ways that benefit other wetland occupants.

Because of their longevity, position in the food chain, and tendency to reside in a limited area, alligators can serve as an indicator of local environmental conditions. Through the process of biomagnification, environmental contaminants can concentrate in their bodies and pose health risks to not only the alligators but also to humans that consume the meat. As a result, FWC’s Alligator Management Program requested that FWRI’s alligator research staff study and monitor mercury (Hg) concentrations in alligator muscle tissue from populations across the state. Our study revealed that average Hg concentrations in Florida waterways varied, but that the rate of accumulation is predictable. Based on these results, alligator research staff began a Hg monitoring program that assesses average Hg concentrations in alligator muscle tissue on harvested lakes, marshes, and river sections known as Alligator Management Units (AMUs). Approximately six or seven AMUs are sampled every year, with a goal of monitoring Hg on over 50 AMUs statewide.

The process involves capturing juvenile (3-6 ft) alligators by hand, snare, or snatch hook, and taking a 0.5-gm biopsy sample of tail muscle tissue to be tested for Hg. The alligator is marked for future identification and released. The tissue samples are sent to the Indian River Field Lab in Melbourne, where our FWRI collaborators analyze them for Hg concentrations. Based on the results and what we learned from the study, we estimate the average Hg concentration of a 7.5-ft alligator (an average-sized alligator that is harvested) on that AMU and inform the Alligator Management staff on whether health/consumption advisories need to be issued.

Advisories are issued to alligator hunters and nuisance trappers that hunt on areas with an average Hg concentration of ≥1 mg/kg. When applied, the advisories prohibit the sale of alligator meat from these areas and strongly discourage consumption. Hunters are, however, allowed to sell the alligator hide. To date, we have identified only two AMUs that meet the criteria for issuing health advisories. Both areas, Water Conservation Areas 1 and 2, are located in South Florida and are part of the eastern Everglades ecosystem. FWRI staff will continue to assess Hg levels in alligator meat to ensure that the public is informed of and protected from any potential health risk.

Working to Conserve Florida’s Endemic and Imperiled Grasshopper Sparrow

By Becky Schneider and Erin Ragheb

The unique Florida dry prairie, a habitat type that has been substantially encroached upon by development, is where the endemic Florida grasshopper sparrow (Ammodramus savannarum floridanus) calls home. Named for both their diet and buzzy insect-like vocalizations, grasshopper sparrows are intensely secretive songbirds that prefer walking over flying and build their nests directly on the ground. The federally-endangered Florida subspecies is one of the rarest birds in North America, and population numbers are dwindling at alarming rates. If this downward population trend continues, the Florida grasshopper sparrow may become extinct within the next decade. Starting in 2013, we initiated an intensive demographic research project on the largest remaining population of Florida grasshopper sparrows, located at Three Lakes Wildlife Management Area, attempting to identify and alleviate the causes of decline.

Beginning in 2015, we placed nest cameras in front of Florida grasshopper sparrow nests to document specific causes of nest failure. We recorded previously unconfirmed nest predators including Eastern spotted skunks, Southern black racers, and red corn snakes. After identifying these key predators, we set out to develop a technique to effectively exclude hungry mammals and snakes from Florida grasshopper sparrow nests. In the subsequent field seasons, we designed and constructed predator fences and installed them around Florida grasshopper sparrow nests. These 10-ft wide exclosures are inconspicuous enough that the incubating female can return to her nest naturally but robust enough to keep predators at bay. The fences have proven to be highly effective at reducing nest predation, and a fenced nest is up to five times more likely to successfully fledge young than an unprotected nest.

Still, predation is not the only factor contributing to low nest success, and our predator fences are not effective at eliminating other sources of nest mortality such as flooding. To reduce the risk of nest loss by flooding, we developed a successful method for elevating nests prior to severe rain events. These intensive management actions have been effective at increasing annual fledgling production and will buy time to develop landscape-level conservation strategies.

Our color banding and resighting data demonstrate that low adult survival rates are another worrying cause of population decline. Apparent survival rates for adult males have decreased dramatically from 75% in 2014 to 36% in 2017. We have also observed recent declines in adult female survival and an increasingly male-biased sex ratio. Our next important step in this study is to determine the causes of reduced adult survival and explore management actions in response. We are now partnering with the University of Florida to screen wild birds for a suite of potential pathogens to identify if disease is contributing to reduced adult survival.

Stalling, stopping, and reversing the perilous decline of the Florida grasshopper sparrow is indeed a daunting task, but with a team of dedicated researchers and strong public support, we expect to conserve this charismatic songbird and increase our knowledge and understanding of Florida’s unique grassland prairie habitat.