Category Archives: Wildlife Research

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.

Update on Panther Reproduction North of the Caloosahatchee River

By Marc Criffield

In March of 2017, FWC documented a female Florida panther with two kittens north of the Caloosahatchee River on the Babcock Ranch Preserve (BRP) via trail cameras (see April 2017 Field Notes). This followed the documentation of a female panther on the BRP in November 2016; the first since 1973. These were momentous events for the recovery of the endangered Florida panther.

Monitoring of these trail cameras by FWC, with support from a group of private and public partners, continued throughout 2017. These types of data collected on panthers will help guide the delineation of the boundary for the known breeding range as successful dens are verified.

No additional photos of the kittens from March 2017 were documented over the summer. This may be a testament to the hardships panther kittens face during their first year of life, a period where our analyses have demonstrated that survival rates are only 32%. If this litter did not survive, it certainly would not be unexpected.

A second litter of panther kittens was documented on the BRP on 22 November 2017. A female panther was photographed with two, approximately 4-month-old, kittens. Given that the number of documented females north of the River is so low, and that females will go into estrous soon after the loss of a litter, there is a high probability that this is the same female that produced a litter in March.

These events give some perspective as to the challenges impacting panther recovery. Although the loss of a litter is disappointing, new kittens demonstrate the resiliency of wild animals in their quest to survive. This most recent litter may certainly be comprised of survivors as they already weathered hurricane Irma in the confines of their den. This latest discovery offers renewed hope for the natural range expansion of panthers that is critical to their long-term recovery.

Investigating Loggerhead Sea Turtles and Where They Go When Not Nesting in Florida

By Simona Ceriani

Sea turtles, a long-living and highly migratory species, are a conservation concern that is primarily studied on nesting beaches, where they are easily accessible. However, only a small fraction of a female’s life is spent near a nesting beach. Reproductively active females undertake breeding migrations every 1 to 5+ years. These breeding migrations are often from distant foraging areas to their natal nesting beach, where they typically lay several clutches in a nesting season. Protecting sea turtle nesting habitat and monitoring nest counts is essential, but an understanding of where females are when they are not nesting (the majority of their time) is equally vital to ensure their protection.

The last decade has seen a growing interest in using stable isotopes, a type of intrinsic marker, as a tool to study migratory connectivity and identify foraging area locations. Work, combining satellite telemetry and stable isotope analysis, showed that post-nesting, satellite-tracked females migrating to geographically separate foraging areas can be identified by differences in their isotopic values. Thus, researchers have increasingly focused on sea turtle nesting aggregations by sampling nesting females and their nest and have used stable isotope analysis to infer foraging areas of larger numbers of untracked females.

Florida hosts ~90% of all the loggerhead nesting activity in the Southeast USA, yet few research groups encounter nesting females at night. In contrast, thousands of nests are marked to assess hatchling production through an extensive program coordinated by the FWC’s Fish and Wildlife Research Institute (FWRI). In 2013, we began a statewide project aiming to identify loggerhead foraging hotspots and determine inter-annual contribution of foraging areas to the Florida nesting aggregation. The project relies on the support and help of over a dozen Marine Turtle Permit Holders across Florida that collect non-viable eggs from a subsample of loggerhead nests marked as a part of FWRI’s hatchling Productivity Assessment Program. Sampling occurs over the entire course of the loggerhead nesting season and reflects nesting temporal distribution.

A few thousand non-viable loggerhead eggs are then transferred to the Sea Turtle Migration Research lab at FWRI Headquarters in St. Petersburg where interns and volunteers help prepare the eggs for analysis. Stable isotope values of unhatched eggs are then used to infer foraging areas used by females during the non-reproductive season.

This study provides a non-invasive and non-destructive method of sampling a relatively large percentage of the loggerhead population nesting in Florida and represents the most comprehensive geographic assessment of foraging areas to date. Using unhatched eggs to assign females to foraging grounds provides an opportunity to:

  1. Sample at a much larger scale, fostering collaborations among research groups and stakeholders
  2. Obtain information that is more representative at the population level
  3. Begin understanding the relative importance of foraging areas and how each foraging ground contribution changes among years.

Conservation funds are limited and there is a need to prioritize where funds should be spent to maximize conservation outcomes. Understanding relative importance of foraging areas will allow us to make more informed management decisions by focusing mitigation and by-catch reduction measures to areas that are loggerhead hotspots.

The first two years of this work were conducted when the principle investigator was at the University of Central Florida and were funded by the Florida Sea Turtle Grants Program. The Sea Turtle Grants Program is funded from proceeds from the sale of the Florida Sea Turtle License Plate.  Since 2015, the scope and scale of the project augmented thanks to the support of a National Oceanic and Atmospheric Administration (NOAA) – National Marine Fisheries Service (NMFS) – ESA Section 6 grant.

Florida Scrub-Jay Translocation Research

By Karl E. Miller

Florida scrub-jay (Aphelocoma coerulescens) populations throughout the state are vulnerable from the effects of habitat fragmentation. The species is mostly sedentary and rarely disperses long distances through non-scrub habitat. Currently, >90% of the remaining scrub-jay populations consist of fewer than 25 family groups.

FWC staff are conducting experimental translocations of Florida scrub-jays to determine the feasibility of a state-wide translocation program to stabilize smaller populations and prevent genetic isolation. The conservation goal is to transport – or “translocate” – birds from a large, stable population in the Ocala National Forest to smaller populations where extensive habitat has been restored but has not been discovered or occupied by Florida scrub-jays. FWC researchers are following up these translocations with intensive monitoring to determine whether the donor population is resilient to the loss of birds and also to determine their impact on populations at recipient sites.

During winter 2017 (December 22-March 21), we relocated 9 Florida scrub-jays, constituting 4 family groups, from Ocala National Forest to Seminole State Forest, which is a distance of >32 km. This initial translocation was a collaborative effort between staff from FWC, the Florida Forest Service, and the US Forest Service.

Translocated groups were tracked using radio telemetry to determine the extent to which they moved throughout the landscape and to understand interactions with neighboring groups. All birds survived transport and release and soon established breeding territories within 200 m of where they were released. During the first week of July, the first successful nest fledged.

In Ocala National Forest, the territories that were vacated were soon occupied by other Florida scrub-jays, including some groups that immigrated from adjacent sub-optimal habitat patches that were heavily overgrown.

Overall, translocated birds appeared to acclimate well to recipient sites, and populations at donor sites did not appear to be negatively affected, which suggests that future translocations will be a worthwhile tool for stabilizing and increasing populations of Florida scrub-jays on managed lands. During winter 2018, we will increase the number of birds moved and the number of recipient sites involved and continue to test the effectiveness of moving different age classes of scrub-jays. We will also continue to test the effectiveness of novel transport and release methods.

Floods, Fires and Hurricanes

By Elina Garrison

In 2015, FWC and other agencies partnered with the University of Georgia and Joseph W. Jones Ecological Center to begin “The South Florida Deer Research Project” in Big Cypress National Preserve (BCNP) and Florida Panther National Wildlife Refuge (FPNWR). One of the main objectives of the study is to understand how hydrology, fire and predators impact deer populations in the unique South Florida system. To date, the team has captured close to 300 deer and fitted 263 adult deer with GPS radio-collars, yielding over 548,000 locations. In addition, three camera grids containing a total of 180 remote-sensing cameras were deployed to monitor deer and other species. Thus far, the team has recorded and cataloged over 360,000 photos. The study was designed to include four years of field work in an effort to capture seasonal and annual fluctuations in weather, predation, and hunting pressure. However, none of us would have expected to capture the weather extremes we have thus far!

In winter 2016, a normally dry season turned into a record-breaking high water event. By February the water stage was over 12 inches above normal and exceeded the prior winter flood record of 1995. We documented unusual deer movement activity, for example, the number of deer detections in our camera grid in FPNWR more than doubled as deer from lower elevations moved to higher ground. Luckily, the duration of the winter 2016 high water event did not last as long as it had 1995.

January in Florda is typically in the middle of the dry season. However, in 2016, an unusual amount of rain caused record flooding throughout our study area.

In March 2017, one of the largest wildfires in Florida started in BCNP. It would eventually burn over 21,000 acres, including an area that contained one of the project’s camera grids and numerous collared deer. No mortalities of collared deer occurred due to the fire and interestingly, deer stayed within their established home-ranges as the woods around them burned. Furthermore, collar data demonstrated deer in proximity to the burn moved into the burned landscape shortly after.

June 2017 brought another flooding event; more rain fell in three days (over 15 inches) than had in the previous 36 weeks, breaking another record. In some areas of BCNP, the water level rose five feet in three days.

Just two days after the large Cowbell Fire burned through much of North Addition Lands, one of the GPS-collared female deer emerges from the burn with another deer.


The most recent event, Hurricane Irma, just occurred. The eyewall of this massive hurricane came within 25 miles of our study site. None of the collared deer died during the hurricane, and preliminary data indicate some that deer moved into pine flatwoods and tropical hammocks, but overall movement rate did not decrease during the storm.

These “record-breaking” events make field work difficult, but they give us insight into impacts of weather extremes that may become more common in the future. The data gathered, both through telemetry and remote cameras, will allow us to analyze how these extreme events impact deer survival, movement, habitat use, and recruitment of fawns, and other aspects of deer ecology. In addition, although the study is focused on white-tailed deer, the cameras capture all wildlife that use these areas, allowing us to examine the effects of extreme weather at a community level.

For more information and quarterly updates, please visit the South Florida Deer project website.