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Understanding dispersal is central to interpreting the effects of climate change, habitat loss and habitat fragmentation, and species invasions. Prior to dispersal, animals may gather information about the surrounding landscape via forays, or systematic, short‐duration looping movements away from and back to the original location. Despite theory emphasizing that forays can be beneficial for dispersing organisms and that such behaviors are predicted to be common, relatively little is known about forays in wild populations. Theory predicts that individuals that use forays may delay dispersal and such behaviors should increase survival, yet empirical tests of these predictions remain scarce. We tested these predictions in a natural system using the critically endangered snail kite (Rostrhaumus sociabilis), a wetland‐dependent raptor. We GPS tracked 104 snail kites from fledging through emigration from the natal site across their breeding range to understand the demographic consequences of movement. We found that forays were common (82.7% of individuals tracked), and natal habitat played an important role in the initiation, execution, and outcome of foray behavior. The effect of foraying on survival was indirect, where forayers emigrated later than non‐forayers, and individuals that emigrated later had the highest survival. Poor hydrological conditions in the natal environment were especially important for eliciting forays. Finally, females responded more strongly to natal hydrology than males, making more forays and significantly longer, more distant trips. These results emphasize the fundamental role of natal habitat for determining behavioral patterns, strengthen links between individual movement decisions and their demographic consequences, and provide an important behavioral focal point for interpreting movement tracks that would not otherwise be captured by conventional movement models. Despite theory predicting the benefits of forays for dispersal, there is relatively little empirical evidence of forays and even less on their fitness consequences. We address this gap using an extensive GPS‐tracking dataset from snail kites tracked from fledging through emigration from the natal site, a critical life stage when many animals are vulnerable to mortality. We find that natal habitat is related to the timing, distance, and duration of forays and that foraying kites initiate dispersal later than kites who do not foray, with indirect survival benefits.

The mechanisms underlying polyandry and female mate choice in certain taxonomic groups remain widely debated. In elasmobranchs, several species have shown varying rates of polyandry based on genetic studies of multiple paternity (MP). We investigated MP in the finetooth shark, Carcharhinus isodon, in order to directly test the encounter rate hypothesis (ERH), which predicts that MP is a result of the frequency of encounters between mature conspecifics during the breeding season, and should therefore increase when more time is available for copulation and sperm storage. Female finetooth sharks in the northern Gulf of Mexico (GoM) have been found to reproduce with both annual periodicity and biennial periodicity, while finetooth sharks from the northwestern Atlantic Ocean have only been found to reproduce biennially, allowing us to compare mating opportunity to frequency of MP. Our results show high rates of MP with no significant difference in frequency between females in the GoM (83.0%) and Atlantic (88.2%, p = .8718) and varying but nonsignificant rates of MP between females in the GoM reproducing annually (93.0%) and biennially (76.6%, p = .2760). While the ERH is not supported by this study, it remains possible that reproductive periodicity and other physiological factors play a role in determining rates of MP in elasmobranchs, with potential benefits to individuals and populations. We investigated multiple paternity in the finetooth shark in order to directly test the encounter rate hypothesis, which predicts that multiple paternity is a result of the frequency of encounters between mature conspecifics during the breeding season. We found high rates of multiple paternity with no significant differences corresponding to reproductive periodicity or location.

The spread of non-native species raises concerns about native species displacement, while other negative effects on native species (e.g., habitat degradation) should also be considered. The highly invasive non-native apple snail Pomacea maculata has raised such concerns as it has become established in a wide range of aquatic systems worldwide. While monitoring native Florida P. paludosa populations in Lake Tohopekaliga (LTOHO) from 2001 to 2009 and in Water Conservation Area 3A (WCA3A, Everglades) from 2006 to 2015, we opportunistically documented the establishment and distribution of P. maculata. We estimated snail densities and recorded egg cluster presence in three study sites (12 total plots, LTOHO) and 137 sites (WCA3). On LTOHO, native snails were absent or at very low densities prior to finding P. maculata. Few snails of either species were found in high-stem-density vegetation of the littoral zone. Pomacea maculata immigration into the littoral zone occurred following managed vegetation removal, and Hydrilla verticillata proliferation in LTOHO likely contributed to the spread of P. maculata. We found both native and non-native apple snail species in many WCA3A sites following P. maculata invasion. We initially found the non-native snail in two sites in southern WCA3A; they were mostly restricted to within three kilometers of initial sites over the next four years. Overall plant community compositions in LTOHO and WCA3A appeared less impacted than expected based on previous reports of P. maculata invasions.

Foraging-patch selection may be influenced by prey density, prey availability, and the energetic costs associated with searching for and capturing prey. Although prey density influences profitability, prey availability may be influenced by habitat and environmental characteristics. We made in situ observations of Snail Kites (Rostrhamus sociabilis) foraging on their exclusive prey, apple snails (Pomacea paludosa), in selected habitats and environmental conditions. We measured the time to capture a snail at 10 sites on Florida lakes (two sites sampled twice over different years for 12 data points total) and five sites in wetlands of the Everglades. Capture times had an inverse asymptotic relationship to snail density. As snail density increased from ∼0.1 to 0.2m-2, capture times declined from ∼600 to 200 sec; capture times leveled off to ∼75 sec between 0.4 and 1.4 snails m-2. Densities of emergent plant stems and water depths, which may influence capture times, were controlled for by site selection; analyses verified these factors had no effects. Snail Kites were significantly more likely to abandon a foraging bout if snail density was <0.2m-2. We interpret the results in the context of foraging for inconspicuous prey. Our data and other reports indicate ∼0.1–0.2 snails m-2 as an approximate threshold below which flight costs increase dramatically and fewer kites tend to forage. Our observations contribute to the limited information available on what constitutes prey density sufficient for the Snail Kite, and we discuss associated conservation implications for this endangered dietary specialist.

Florida apple snails, Pomacea paludosa, serve as the nearly exclusive prey for the endangered Florida snail kite, Rostrhamus sociabilis, and many other predators in Florida wetlands. As the Florida Everglades is a hotspot for non-native species, it is prudent to understand the potential impacts non-native predators have on apple snails. In an aquarium setting, we recorded and documented the interactions between the non-native jewelfish, Hemichromis letourneuxi, and native apple snails. We compared these interactions to those recorded between apple snails and redear sunfish, Lepomis microlophus, a native predator. We found that sunfish successfully ate more snails. However, jewelfish attacked apple snails more frequently (n = 314) compared to sunfish (n = 68), resulting in apple snails withdrawing into their shells and displaying longer recovery times from attacks. Apple snails appear to spend more time recovering from attacks or possibly avoiding predation risk, rather than conducting normal movements, in the presence of the jewelfish. This may have impacts on apple snail behavioral ecology, physiology, and demography, potentially reducing prey availability for the endangered snail kite and other predators. Our research provides evidence that jewelfish negatively impact a critically important prey species in Florida wetland food webs.

Context The Florida Everglades has diminished in size and its existing wetland hydrology has been altered. The endangered snail kite ( Rostrhamus sociabilis ) has nearly abandoned the Everglades, and its prey, the apple snail ( Pomacea paludosa ), has declined. Objective We developed a population model (EverSnail) to understand apple snail response to inter- and intra-annual fluctuations in water depths over the Everglades landscape. EverSnail was developed as a tool to understand how apple snails respond to different hydrologic scenarios. Methods EverSnail is an age- and size-structured, spatially-explicit landscape model of P. paludosa in the Everglades. Landscape-level inputs are water depth and air temperature. We conducted sensitivity analyses by running EverSnail with ±20 % the baseline value of eight parameters. Results EverSnail was sensitive to changes in survival and water depth associated with reproduction. The EverSnail population varied with changes and/or differences in depth generally consistent with empirical data; site-specific comparisons to field data proved less reliable. A simulated 3-year wet period resulted in a shift in apple snail distribution, but little change in total abundance over the landscape. In contrast, a simulated 3-year succession of relatively dry years resulted in overall lower snail abundances. Conclusions Comparisons of model output to empirical data indicate the need for more data to better understand, and eventually parameterize, several aspects of snail ecology in support of EverSnail. A primary value of EverSnail is its capacity to describe the relative response of snail abundance to alternative hydrologic scenarios considered for Everglades water management and restoration.

Understanding how predators respond to fluctuations in prey density has important conservation and management implications, particularly for threatened and endangered specialists. However, directly linking prey densities to predator behavior and demography over broad spatial and temporal scales is rare, in part, because it can be prohibitively expensive and time-consuming to quantify prey density over large areas. We link nesting data collected by a long-term monitoring program for the endangered snail kite (Rostrhamus sociabilis plumbeus) with 44 density estimates of its primary prey, the Florida apple snail (Pomacea paludosa), collected by multiple, smaller-scale studies from 2002 to 2010. We found evidence that key components of kite breeding biology—nest density and the number of young fledged per successful nest—were positively related to snail density. Although previous studies have shown that densities greater than approximately 0.1-0.2 snails/m², may be necessary to sustain profitable foraging and that capture times for individual foraging kites begin to level off as snail densities exceed approximately 0.4 snails/m², we found continued numerical responses in snail kite reproductive parameters at greater snail densities. At occupied sites (i. e., snail-sampling sites in which ≥ 1 snail kite nest was present within a 2-km radius during the primary sampling period: Mar-May), the average snail density was 0.45 snails/m² (SE = 0.12, n = 17), whereas that of unoccupied sites was 0.12 snails/m² (SE = 0.02, n = 27). Along the snail density gradient from 0.2 to 0.4 to 1.2 snails/m², model predictions indicated that 1) the probability of site occupancy (by nesting kites) increased from 0.48 to 0.69 to 0.90,2) local nest abundance of occupied sites increased from 4 to 7 to 16 nests, and 3) the probability of a successful nesting attempt fledging more than 1 young increased from 0.02 to 0.07 to 0.43. We found no evidence of a snail density effect on nest survival. Understanding the differential effects of snail density on various components of snail kite breeding biology is essential to the development and implementation of management tools used for snail kite conservation and Everglades restoration. Published 2014. This article is a U. S. Government work and is in the public domain in the USA.

Pomacea (Ampullariidae) snails, commonly referred to as apple snails, serve as prey for many freshwater-dependent predators, and some species are highly invasive. Identifying limits to apple snail distribution and abundance are pertinent to understanding their ecology. Calcium (Ca²⁺) availability and pH generally influences freshwater snail populations, yet scant data exist for Pomacea snails. We measured 6-week change in shell length (ΔSL) in P. paludosa in two laboratory experiments with varying Ca²⁺ and pH levels. ΔSL was significantly higher in ≥28 mg Ca²⁺/l compared with treatments ≤14 mg/l. Snails from populations living in low Ca²⁺/pH waters did not appear genetically predisposed at growing faster in these conditions. Smallest ΔSL was in snails treated with 3.6 mg Ca²⁺/l and pH < 6.5 water; these snails had signs of shell erosion. Shell crush weights (CWs) were lowest for snails grown in the lowest Ca²⁺/pH treatment. Smaller shells and lower CWs have implications for predation vulnerability and reproductive success. Our results are consistent with reports associating relatively low snail densities with relatively low Ca²⁺/pH waters, and they are consistent with the geographic distribution of P. paludosa as related to the underlying water chemistry as influenced by geology.

Florida apple snails (Pomacea paludosa Say) are prey for several wetland-dependent predators, most notably for the endangered Florida snail kite (Rostrhamus sociabilis Vieillot). Management concerns for kites have been raised regarding the impacts of wetland dry downs on snails, but little data exists to validate these concerns. We simulated drying events in experimental tanks, where we observed that snail survival patterns, regardless of hydrology, were driven by a post-reproductive die off. In contrast to earlier reports of little to no dry down tolerance, we found that 70% of pre-reproductive adult-sized snails survived a 12-week dry down. Smaller size classes of snails exhibited significantly lower survival rates (< 50% after eight weeks dry). Field surveys showed that 77% of egg production occurs in April–June. Our hydrologic analyses of six peninsular Florida wetlands showed that most dry downs overlapped a portion of the peak snail breeding season, and 70% of dry downs were ≤ 12 weeks in duration. Dry down timing can affect recruitment by truncating annual egg production and stranding juveniles. Dry down survival rates and seasonal patterns of egg cluster production helped define a range of hydrologic conditions that support robust apple snail populations, and illustrate why multiple characteristics of dry down events should be considered in developing target hydrologic regimes for wetland fauna.

Wetlands often support a variety of juxtaposed habitat patches (e.g., grass-, shrub- or tree-dominated) differentially suited to support the inhabiting fauna. The proportion of available habitat types has been affected by human activity and consequently has contributed to degrading habitat quality for some species. The Florida apple snail (Pomacea paludosa) has drawn attention as a critical prey item for wetlands wildlife and as an indicator of wetlands restoration success in peninsular Florida, USA. An apparent contradiction has evolved wherein this species appears intolerant of drying events, but these disturbances may be necessary to maintain suitable habitat structure for apple snails. We recently reported that assertions regarding intolerance to dry downs in this species were inaccurate. Here, we compared snail density in habitats with (wet prairie) and without (slough) emergent macrophytes, as well as evaluating the effects of structural attributes within the broad wet prairie habitat type. Snail densities were greater in prairies relative to sloughs (χ2 = 12.90, df = 1, P = 0.0003), often by a factor of two to three. Within wet prairie habitats, we found greater snail densities in Panicum hemitomon as compared to Eleocharis cellulosa (χ2 = 31.45, df = 1, P = 0.0001). Significantly fewer snails were found in dense E. cellulosa as compared to habitats with lower stem density (χ2 = 10.73, df = 1, P = 0.011). Our results indicate that wet prairie habitat supports greater snail densities than Nymphaea-dominated slough. Our results have implications for wetlands water management in that continuous inundation has been shown to convert wet prairie to slough habitat, and we suggest this should be avoided in support of apple snails and their predators.