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Many ecosystems are influenced by disturbances that create specific successional states and habitat structures that species need to persist. Estimating transition probabilities between habitat states and modeling the factors that influence such transitions have many applications for investigating and managing disturbance-prone ecosystems. We identify the correspondence between multistate capture-recapture models and Markov models of habitat dynamics. We exploit this correspondence by fitting and comparing competing models of different ecological covariates affecting habitat transition probabilities in Florida scrub and flatwoods, a habitat important to many unique plants and animals. We subdivided a large scrub and flatwoods ecosystem along central Florida's Atlantic coast into 10-ha grid cells, which approximated average territory size of the threatened Florida Scrub-Jay (Aphelocoma coerulescens), a management indicator species. We used 1.0-m resolution aerial imagery for 1994, 1999, and 2004 to classify grid cells into four habitat quality states that were directly related to Florida Scrub-Jay source-sink dynamics and management decision making. Results showed that static site features related to fire propagation (vegetation type, edges) and temporally varying disturbances (fires, mechanical cutting) best explained transition probabilities. Results indicated that much of the scrub and flatwoods ecosystem was resistant to moving from a degraded state to a desired state without mechanical cutting, an expensive restoration tool. We used habitat models parameterized with the estimated transition probabilities to investigate the consequences of alternative management scenarios on future habitat dynamics. We recommend this multistate modeling approach as being broadly applicable for studying ecosystem, land cover, or habitat dynamics. The approach provides maximum-likelihood estimates of transition parameters, including precision measures, and can be used to assess evidence among competing ecological models that describe system dynamics.

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The combined effects of habitat quality, breeder experience and sociobiology on population demography are poorly understood. Natural fire regimes, which influence habitat quality and sociobiology, have been replaced by controlled fire management in most ecosystems. Managing fire mosaics (vegetation at different ages since fire) can be important to sustain species in fire-maintained habitats, but requirements are usually poorly defined. Source-sink theory provides a foundation to quantify such habitat heterogeneity, but source-sink applications are largely focused on modeling. We quantified how habitat quality, breeder experience and non-breeding adult helpers affected Florida scrub-jay (Aphelocoma coerulescens) recruitment to describe source-sink heterogeneity within local populations. We used 22 years of census data of uniquely marked Florida scrub-jays to measure recruitment at 36 sites and combined that data with habitat-specific survival to characterize habitat-specific demography. To define habitat quality at the territory scale, we used static habitat features (soils, scrub oak cover) and dynamic habitat states (shrub heights and open sandy patches) that resulted from fire mosaics. Habitat quality most affected recruitment followed by the presence of helpers; fire mosaics, described by habitat states, determined whether territories functioned as strong sources, weak sources or sinks. Subdividing landscapes into habitat states allowed quantification of the fire mosaic at the territory scale and population scale, as the proportions of habitat states can predict local population growth rates. Our approach provides an example of how characterizing habitat quality at the territory scale, relative to source-sink categories, can explain habitat heterogeneity within local populations and inform fire management. bs_bs_banner Animal Conservation. Print

Species displaying temperature-dependent sex determination (TSD) are especially vulnerable to the effects of a rapidly changing global climate due to their profound sensitivity to thermal cues during development. Predicting the consequences of climate change for these species, including skewed offspring sex ratios, depends on understanding how climatic factors interface with features of maternal nesting behaviour to shape the developmental environment. Here, we measure thermal profiles in 86 nests at two geographically distinct sites in the northern and southern regions of the American alligator's ( Alligator mississippiensis ) geographical range, and examine the influence of both climatic factors and maternally driven nest characteristics on nest temperature variation. Changes in daily maximum air temperatures drive annual trends in nest temperatures, while variation in individual nest temperatures is also related to local habitat factors and microclimate characteristics. Without any compensatory nesting behaviours, nest temperatures are projected to increase by 1.6–3.7°C by the year 2100, and these changes are predicted to have dramatic consequences for offspring sex ratios. Exact sex ratio outcomes vary widely depending on site and emission scenario as a function of the unique temperature-by-sex reaction norm exhibited by all crocodilians. By revealing the ecological drivers of nest temperature variation in the American alligator, this study provides important insights into the potential consequences of climate change for crocodilian species, many of which are already threatened by extinction.

Resolving the geographic extent and timing of coastal shark migrations, as well as their environmental cues, is essential for refining shark management strategies in anticipation of increasing anthropogenic stressors to coastal ecosystems. We employed a regional-scale passive acoustic telemetry array encompassing 300 km of the east Florida coast to assess what factors influence site fidelity of juvenile lemon sharks (Negaprion brevirostris) to an exposed coastal nursery at Cape Canaveral, and to document the timing and rate of their seasonal migrations. Movements of 54 juvenile lemon sharks were monitored for three years with individuals tracked for up to 751 days. While most sharks demonstrated site fidelity to the Cape Canaveral region December through February under typical winter water temperatures, historically extreme declines in ocean temperature were accompanied by rapid and often temporary, southward displacements of up to 190 km along the Florida east coast. From late February through April each year, most sharks initiated a northward migration at speeds of up to 64 km day−1 with several individuals then detected in compatible estuarine telemetry arrays in Georgia and South Carolina up to 472 km from release locations. Nineteen sharks returned for a second or even third consecutive winter, thus demonstrating strong seasonal philopatry to the Cape Canaveral region. The long distance movements and habitat associations of immature lemon sharks along the US southeast coast contrast sharply with the natal site fidelity observed in this species at other sites in the western Atlantic Ocean. These findings validate the existing multi-state management strategies now in place. Results also affirm the value of collaborative passive arrays for resolving seasonal movements and habitat preferences of migratory coastal shark species not easily studied with other tagging techniques.

Anthropogenic influences have altered most fire regimes. Fire management programs often try to mimic natural fire regimes to maintain fuels and sustain native fire-dependent species. Lightning is the natural ignition source in Florida, substantiating the need for understanding lightning fire incidence. Sixteen years of lightning data (1986–2003, excluding 1987 and 2002 due to missing data) from the NASA Cloud to Ground Lightning Surveillance System and fire ignition records were used to quantify the relationship between lightning incidence and ignitions on Kennedy Space Center, Merritt Island National Wildlife Refuge, and Cape Canaveral Air Force Station. There were 230 lightning fires with an average of 14 ignitions per year, primarily in July, and only one winter ignition. Precipitation influenced the efficiency of lightning ignitions, particularly July precipitation. We found that negative polarity strikes caused the majority of ignitions. Pine flatwoods was ignited more frequently than expected given equal chance of ignition among landcover types. About half (51%) of detected fires were instantaneous ignitions and the other 49% were delayed an average of 2 days. This information is useful for paramaterizing fire regime models and for mimicking the natural fire regime through fire prescriptions on these properties and throughout the southeastern United States. These methods may be useful in fire-maintained systems globally.

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