Recent Submissions

  • Survival and Growth of American Alligator (Alligator mississippiensis) hatchlings after artificial incubation and repatriation

    Temsiripong, Yosapong; Woodward, Allan R.; Ross, J. Perran; Kubilis, Paul S.; Percival, H. Franklin (2006)
    Hatchling American Alligators (Alligator mississippiensis) produced from artificially incubatedwild eggs were returned to their natal areas (repatriated). We compared artificially incubated andrepatriated hatchlings released within and outside the maternal alligator’s home range with naturallyincubated hatchlings captured and released within the maternal alligator’s home range on Lake Apopka,Lake Griffin, and Orange Lake in Florida. We used probability of recapture and total length at approximatelynine months after hatching as indices of survival and growth rates. Artificially incubated hatchlings releasedoutside of the maternal alligator’s home range had lower recapture probabilities than either naturallyincubated hatchlings or artificially incubated hatchlings released near the original nest site. Recaptureprobabilities of other treatments did not differ significantly. Artificially incubated hatchlings wereapproximately 6% shorter than naturally incubated hatchlings at approximately nine months after hatching.We concluded that repatriation of hatchlings probably would not have long-term effects on populationsbecause of the resiliency of alligator populations to alterations of early age-class survival and growth rates ofthe magnitude that we observed. Repatriation of hatchlings may be an economical alternative to repatriationof older juveniles for population restoration. However, the location of release may affect subsequent survivaland growth.
  • Temperature effects on Florida applesnail activity: implications for snail kite foraging success and distribution

    Stevens, Amanda J. (2002)
    The endangered Florida snail kite (Rostrhamlls sociaiJilis) feeds exclusively on applesnails(Pomacea pailiclosa), yet we lack direct observations that link applesnail behavior to snailkite foraging success. The purpose of our study was to evaluate the temperature-activityprofile of applesnails in the context of restricted foraging opportunities for snail kites.Applesnail activity was monitored in water temperatures ranging from 2-24
  • Scale-Dependent Habitat Selection of Nesting Great Egrets and Snowy Egrets

    Stolen, Eric D.; Collazo, Jaime A.; Percival, H. Franklin (2007)
    Foraging habitat selection of nesting Great Egrets (Ardea alba) and Snowy Egrets (Egretta thula) wasinvestigated within an estuary with extensive impounded salt marsh habitat. Using a geographic information system,available habitat was partitioned into concentric bands at five, ten, and 15 km radius from nesting colonies to assessthe relative effects of habitat composition and distance on habitat selection. Snowy Egrets were more likely thanGreat Egrets to depart colonies and travel to foraging sites in groups, but both species usually arrived at sites thatwere occupied by other wading birds. Mean flight distances were 6.2 km (SE = 0.4, N = 28, range 1.8-10.7 km) forGreat Egrets and 4.7 km (SE = 0.48, N = 31, range 0.7-12.5 km) for Snowy Egrets. At the broadest spatial scale bothspecies used impounded (mostly salt marsh) and estuarine edge habitat more than expected based on availabilitywhile avoiding unimpounded (mostly fresh water wetland) habitat. At more local scales habitat use matched availability.Interpretation of habitat preference differed with the types of habitat that were included and the maximumdistance that habitat was considered available. These results illustrate that caution is needed when interpreting theresults of habitat preference studies when individuals are constrained in their choice of habitats, such as for centralplace foragers.
  • Vegetation Effects on Fish Distribution in Impounded Salt Marshes

    Stolen, Eric D.; Collazo, Jaime A.; Percival, H. Franklin (2009)
    We compared the density and biomass of resident fish in vegetated andunvegetated flooded habitats of impounded salt marshes in the northern IndianRiver Lagoon (IRL) Estuary of east-central Florida. A 1-m2 throw trap was usedto sample fish in randomly located, paired sample plots (n = 198 pairs) over 5 seasonsin 7 impoundments. We collected a total of 15 fish taxa, and 88% of the fisheswe identified from the samples belonged to three species: Cyprinodon variegatus(Sheepshead Minnow), Gambusia holbrooki (Eastern Mosquitofish), and Poecilialatipinna (Sailfin Molly). Vegetated habitat usually had higher density and biomassof fish. Mean fish density (and 95% confidence interval) for vegetated and unvegetatedsites were 8.2 (6.7–9.9) and 2.0 (1.6–2.4) individuals m-2, respectively; meanbiomass (and 95% confidence interval) for vegetated and unvegetated sites were3.0 (2.5–3.7) and 1.1 (0.9–1.4) g m-2, respectively. We confirmed previous findingsthat impounded salt marshes of the northern IRL Estuary produce a high standingstock of resident fishes. Seasonal patterns of abundance were consistent with fishmoving between vegetated and unvegetated habitat as water levels changed in theestuary. Differences in density, mean size, and species composition of residentfishes between vegetated and unvegetated habitats have important implications formovement of biomass and nutrients out of salt marsh by piscivores (e.g., wadingbirds and fishes) via a trophic relay.
  • Trapping success and population analysis of Siren lacertina and Amphiuma means

    Sorensen, Kristina (University of Florida, Wildlife Ecology and Conservation, 2003)
    Siren and Amphiuma are two poorly known genera of aquatic salamanders thatoccur in the Southeastern United States. A primarily bottom-dwelling existence makesthese salamanders difficult to detect with conventional sampling methodologies.Therefore, the current status of their populations is unknown. I compared the capturesuccess of modified crayfish traps and plastic minnow traps in capturing thesesalamanders. In addition, a mark-recapture study of S. lacertina (Greater siren) and A.means (Two-toed amphiuma) was conducted at Okefenokee National Wildlife Refuge(southern Georgia) and at Katharine Ordway Preserve (north-central Florida) fromAugust 2001 until September 2002.Crayfish traps were much more successful than minnow traps in catching sirenand amphiuma. Crayfish traps yielded 270 captures for an overall capture success of16%, whereas minnow traps yielded only 13 captures for an overall success rate of0.05%. In addition, several marking techniques were evaluated, and of these, only passive integrated transponder (PIT) tags were retained for the duration of the study.Therefore, I recommend this marking technique for long-term monitoring of S. lacertinaand A. means.Several variables were found to have significant effects on capture rates ofsalamanders. A. means were most often captured in summer and the number of captureswas positively correlated with water temperature, water level, and rainfall. S. lacertinawere most often captured during winter and spring. Number of captures was negativelycorrelated with water temperature, while no relationship was found with water level orrainfall. Trap day and baiting had no significant effect on number of A. means or S.lacertina captured.Recapture probabilities of both species were low, 0.025-0.03 for S. lacertina and0.08-0.11 for A. means. Monthly survival rates were high, 0.77-0.97 for A. means and0.88-1.00 for S. lacertina. Density estimates of 1.3 salamanders/m2 (S. lacertina) and0.28 salamanders/m2 (A. means) were obtained for Lake Suggs using Jolly-Seber models.Siren and amphiuma make up a substantial part of wetland biomass and can impact manyother wetland species. Thus, more attention must be focused on evaluating andmonitoring their populations.
  • Home range and habitat use by Kemp's Ridley turtles in West-Central Florida

    Schmid, J.R.; Bolten, Alan B.; Bjorndal, Karen A.; Lindberg, William J.; Percival, H. Franklin; Zwick, Paul D. (2003)
    The Kemp's ridley turtle (Lepidochelys kempii) is an endangered species whose recovery depends in part onthe identification and protection of required habitats. We used radio and sonic telemetry on subadult Kemp's ridleyturtles to investigate home-range size and habitat use in the coastal waters of west-central Florida from 1994 to1996. We tracked 9 turtles during May-August up to 70 days after release and fou.ld they occupied 5-30 km2 foragingranges. Compositional analyses indicated that turtles used rock outcroppings in their foraging ranges at asignificantly higher proportion than expected. based on availability within the study area. Additionally. turtles usedlive bottom (e.g .• sessile invertebrates) and green macroalgae habitats significantly more than seagrass habitat. Similarstudies are needed through'mt the Kemp's ridley turtles' range to investigate regional and stage-specific differencesin habitat use. which can then be used to conserve important foraging areas.
  • Activity patterns of Kemp's ridley turtles, Lepidochelys kempii, in the coastal waters of the Cedar Keys, Florida

    Schmid, J.R.; Bolten, Alan B.; Bjorndal, Karen A.; Lindberg, William J. (2002)
    Radio and sonic telemetry were used to investigatethe tidal orientation, rate of movement(ROM), and surfacing behavior of nine Kemp's ridleyturtles, Lepidochelys kempii, tracked east of the CedarKeys, Florida. The mean of mean turtle bearings onincoming (48 ± 49 0) and falling (232 ± 41 0) tides wassignificantly oriented to the mean directions of tidal flow(37±9°, P<0.0025, and 234±9 0, P<0.005, respectively).Turtles had a mean ROM of 0.44±0.33 km/h(range: 0.004-1.758 km/h), a mean surface duration of18± 15 s (range: 1-88 s), and a mean submergence durationof 8.4± 6.4 min (range: 0.2-60.0 min). ROM wasnegatively correlated with surface and submergencedurations and positively correlated with the number ofsurfacings. Furthermore, ROMs were higher and surface and submergence durations were shorter during the day.Daily activities of turtles were attributed to food acquisitionand bioenergetics.
  • Estimating Sighting Proportions of American Alligator Nests during Helicopter Survey

    Rice, Kenneth G.; Percival, H. Franklin; Woodward, Allan R. (2000)
    Proportions of American alligator (Alligator mississippiensis) nests sightedduring aerial survey in Florida were estimated based upon multiple surveys by differentobservers. We compared sighting proportions across habitats, nesting seasons, and observerexperience levels. The mean sighting proportion across all habitats and years was0.736 (SE=0.024). Survey counts corrected by the mean sighting proportion reliablypredicted total nest counts (R2=0.933). Sighting proportions did not differ by habitattype (P=0.668) or year P=0.328). Experienced observers detected a greater proportionof nests (P<O.OOOl) than did either less experienced or inexperienced observers. Reliableestimates of nest abundance can be derived from aerial counts of alligator nestswhen corrected by the appropriate sighting proportion.
  • Alligator Diet in Relation to Alligator Mortality on Lake Griffin, FL

    Rice, Amanda Nicole; Ross, J. Perran; Woodward, Allan R.; Carbonneau, Dwayne A.; Percival, H. Franklin (2007)
    Alligator mississippiensis (American Alligators) demonstrated low hatchratesuccess and increased adult mortality on Lake Griffin, FL, between 1998 and2003. Dying Lake Griffin alligators with symptoms of poor motor coordination werereported to show specific neurological impairment and brain lesions. Similar lesionswere documented in salmonines that consumed clupeids with high thiaminase levels.Therefore, we investigated the diet of Lake Griffin alligators and compared it withalligator diets from two lakes that exhibited relatively low levels of unexplainedalligator mortality to see if consumption of Dorosoma cepedianum (gizzard shad)could be correlated with patterns of mortality. Shad in both lakes Griffin and Apopkahad high levels of thiaminase and Lake Apopka alligators were consuming greateramounts of shad relative to Lake Griffin without showing mortality rates similar toLake Griffin alligators. Therefore, a relationship between shad consumption aloneand alligator mortality is not supported.
  • Diet and condition of American Alligators (Alligator mississippiensis)in three central Florida lakes

    Rice, Amanda Nicole (University of Florida, Natural Resources and Environment, 2004)
    Understanding the diet of crocodilians is important because diet affects condition, behavior, growth, and reproduction. By examining the diet of crocodilians, valuable knowledge is gained about predator-prey interactions and prey utilization among habitats. In this study, I examined the diet and condition of adult American alligators (Alligator mississippiensis) in three central Florida lakes, Griffin, Apopka, and Woodruff. Two hundred adult alligators were captured and lavaged from March through October 2001, from April through October 2002, and from April through August 2003.Alligators ate a variety of vertebrate and invertebrate prey, but vertebrates were more abundant and fish dominated alligator diets in the lakes. Species composition of fish varied among the lakes. The majority of the diet of alligators from Lakes Apopka and Woodruff was fish, 90% and 84% respectively. Lake Apopka alligators consumed a significantly (P = 0.006) higher proportion of fish in their diet. Fish were 54% of the diet of Lake Griffin alligators and the infrequent occurrence of reptiles, mammals, birds, and amphibians often resulted in a large biomass. Differences in alligator diets among lakes may be due to differences in sample size (higher numbers of samples from Lake Griffin), prey availability, habitat, prey vulnerability, or prey size.Alligator condition (Fulton’s Condition Factor, K) was significantly (P < 0.001) different among the lakes. Alligators from Lake Apopka had the highest condition, followed by those from Lake Griffin, and alligators from Lake Woodruff had the lowest condition. Composition of fish along with diversity and equitability of fish in alligator diets may have contributed to differences in condition among lakes. Condition was probably also due to factors other than diet such as alligator hunting behavior, alligator density, or year-round optimal temperature that prolongs feeding. The observed diet and condition differences probably reflect both habitat differences and prey availability in these three lakes.
  • Caretta caretta (Loggerhead Sea Turtle). Nest Architecture.

    Tiwari, Manjula; Carthy, Raymond R.; Silveira, Alex; Bjorndal, Karen A. (2003)
    Researchers compared nest architecturein loggerhead sea turtles at natural beaches in Florida, USA andBrazil to determine how similarities and differences in femalemorphology and reproductive output in these two populations arereflected in the structure of the nest.
  • Herpetofaunal Inventories of the National Parks of South Florida and the Caribbean: Volume II. Virgin Islands National Park

    Rice, Kenneth G.; Waddle, J. Hardin; Crockett, Marquette E.; Carthy, Raymond R.; Percival, H. Franklin (U.S. Geological SurveyReston, VA, 2005)
    Amphibian declines and extinctions have been documented around the world, often in protectednatural areas. Concern for this alarming trend has focused attention on the need to document all species ofamphibians that occur within U.S. National Parks and to search for any signs that amphibians may bedeclining. This study, an inventory of amphibian species in Virgin Islands National Park, was conductedfrom 2001 to 2003. The goals of the project were to create a georeferenced inventory of amphibianspecies, use new analytical techniques to estimate proportion of sites occupied by each species, look forany signs of amphibian decline (missing species, disease, die-offs, etc.), and to establish a protocol thatcould be used for future monitoring efforts.Several sampling methods were used to accomplish these goals. Visual encounter surveys andanuran vocalization surveys were conducted in all habitats throughout the park to estimate the proportionof sites or proportion of area occupied (PAO) by amphibian species in each habitat. Line transect methodswere used to estimate density of some amphibian species and double observer analysis was used to refinecounts based on detection probabilities. Opportunistic collections were used to augment the visualencounter methods for rare species. Data were collected during four sampling periods and every majortrail system throughout the park was surveyed.All of the amphibian species believed to occur on St. John were detected during these surveys.One species not previously reported, the Cuban treefrog (Osteopilus septentrionalis), was also added tothe species list. That species and two others (Eleutherodactylus coqui and Eleutherodactylus lentus) bringthe total number of introduced amphibians on St. John to three. We detected most of the reptile speciesthought to occur on St. John, but our methods were less suitable for reptiles compared to amphibians.No amphibian species appear to be in decline at this time. We found no evidence of disease or ofmalformations. Our surveys provide a snapshot picture of the status of the amphibian species, socontinued monitoring would be necessary to determine long-term trends, but several potential threats toamphibians were identified. Invasive species, especially the Cuban treefrog, have the potential to decreasepopulations of native amphibians. Introduced mammalian predators are also a potential threat, especiallyto the reptiles of St. John, and mammalian grazers might have indirect effects on amphibians and reptilesthrough habitat modification. Finally, loss of habitat to development outside the park boundary couldharm some important populations of amphibians and reptiles on the island.
  • Littoral vegetation of Lake Tohopekaliga: community descriptions prior to a large-scale fisheries habitat-enhancement project

    Welch, Zahariah C. (University of Florida, Wildlife Ecology and Conservation, 2004)
    An extreme dry-down and muck-removal project was conducted at LakeTohopekaliga, Florida, in 2003-2004, to remove dense vegetation from inshore areas andimprove habitat degraded by stabilized water levels. Vegetation was monitored fromJune 2002 to December 2003, to describe the pre-existing communities in terms ofcomposition and distribution along the environmental gradients. Three study areas(Treatment-Selection Sites) were designed to test the efficacy of different treatments inenhancing inshore habitat, and five other study areas (Whole-Lake Monitoring Sites)were designed to monitor the responses of the emergent littoral vegetation as a whole.Five general community types were identified within the study areas by recordingaboveground biomasses and stem densities of each species. These communities weredistributed along water and soils gradients, with water depth and bulk density explainingmost of the variation. The shallowest depths were dominated by a combination ofEleocharis spp., Luziola fluitans, and Panicum repens; while the deeper areas hadcommunities of Nymphaea odorata and Nuphar luteum; Typha spp.; or Paspalidiumgeminatum and Hydrilla verticillata. Mineralized soils were common in both the shallowand deep-water communities, while the intermediate depths had high percentages oforganic material in the soil. These intermediate depths (occurring just above and justbelow low pool stage) were dominated by Pontederia cordata, the main species targetedby the habitat enhancement project. This emergent community occurred in nearlymonocultural bands around the lake (from roughly 60–120 cm in depth at high poolstage) often having more diverse floating mats along the deep-water edge. The organicbarrier these mats create is believed to impede access of sport fish to shallow-waterspawning areas, while the overall low diversity of the community is evidence of itscompetitive nature in stabilized waters. With continued monitoring of these study areaslong-term effects of the restoration project can be assessed and predictive models may becreated to determine the efficacy and legitimacy of such projects in the future.
  • Defining the Present Before Restoring the Past: Everglades Vegetation Communities

    Zweig, Christa L.; Kitchens, Wiley M.; Society of Wetland Scientists (2009)
  • Evaluation of Field Measurements of the American Alligator for Use in Morphometric Studies

    Zweig, Christa L.; Mazzotti, Frank J.; Rice, Kenneth G.; Brandt, Laura; Abercrombie, C.L. (2004)
  • The Semiglades: the collision of restoration, social values, and the ecosystem concept

    Zweig, Christa L.; Kitchens, Wiley M. (2010)
    Opinion article
  • Effects of landscape gradients on wetland vegetation communities: information for large-scale restoration

    Zweig, Christa L.; Kitchens, Wiley M. (2008-00-00)
    Projects of the scope of the restoration of the Florida Everglades require substantialinformation regarding ecological mechanisms, and these are often poorly understood. We provide criticalbase knowledge for Everglades restoration by characterizing the existing vegetation communities of anEverglades remnant, describing how present and historic hydrology affect wetland vegetation communitycomposition, and documenting change from communities described in previous studies. Vegetationbiomass samples were collected along transects across Water Conservation Area 3A South (3AS).
  • Impact of harvest on survival of a heavily hunted game bird population [In Press]

    Rolland, Virginie; Hostetler, Jeff; Hines, Tommy; Percival, H. Franklin; Oli, Madan (2011)

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