Search

Human‐driven land use change can fundamentally alter ecological communities, especially the diversity and abundance of large‐bodied predators. Yet, despite the important roles large‐bodied predators play in structuring communities through feeding, there have been only a few investigations of how the feeding patterns of large‐bodied predators change in human‐dominated landscapes. One group of large‐bodied predators that has been largely overlooked in the context of land use change is the crocodilians. To help fill these gaps, we studied the feeding patterns of juvenile American alligators (Alligator mississippiensis) on neighboring barrier islands on the southeast coast of Georgia, USA. Jekyll Island has multiple golf courses and substantial amounts of human activity, while Sapelo Island does not have any golf courses and a much smaller amount of human activity. We found that juvenile alligator populations on both islands ate the same types of prey but in vastly different quantities. Sapelo Island alligators primarily consumed crustaceans while alligators that lived on Jekyll Island's golf courses ate mostly insects/arachnids. Furthermore, the Jekyll Island alligators exhibited a much more generalist feeding pattern (individuals mostly ate the same types of prey in the same quantities) than the more specialized Sapelo Island alligators (diets were more varied across individuals). The most likely explanation for our results is that alligators living on golf courses have different habitat use patterns and have access to different prey communities relative to alligators in more natural habitats. Thus, land use change can strongly alter the feeding patterns of large‐bodied predators and, as a result, may affect their body condition, exposure to human‐made chemicals, and role within ecological communities. [ABSTRACT FROM AUTHOR]

The burial of "blue carbon" in coastal marsh soils is partially offset by marsh‐atmosphere methane (CH4) fluxes, but this offset may be greater if other pathways of CH4 export exist. Here we report that salt marshes also export dissolved CH4 via submarine groundwater discharge (SGD). The volumetric fluxes of salt marsh groundwater into adjacent tidal creeks were calculated from mass balances of the conservative tracer 226Ra at four study sites in coastal Georgia, USA. Over the 2‐year study period, volumetric groundwater fluxes across all sites ranged between 1,700 and 105,000 m3 day−1. Dissolved CH4 fluxes of 27–1,200 μmol CH4 m−2 day−1 were calculated by multiplying the volumetric groundwater flux by the groundwater CH4 concentration and normalizing to the intertidal salt marsh area estimated from satellite images. On a mass basis, the cross‐site range in CH4 fluxes was 1.3–5.5 g CH4 m−2 year−1 with a cross‐site mean of 2.8 g CH4 m−2 year−1. This is equivalent to 125 (56–245) g CO2 m−2 year−1 assuming that CH4 is 45 times more potent than CO2 as a greenhouse gas over a 100‐year time frame. This sustained‐flux global warming potential is similar to the 138 (1.1–260) g CO2 m−2 year−1 average calculated across other studies of the direct marsh soil to atmosphere CH4 flux. Therefore, SGD drives an effective doubling of salt marsh CH4 export that offsets a combined total of ~30% of the global cooling potential derived from soil carbon sequestration. Plain Language Summary: Salt marshes are wetland ecosystems found along the coast. Scientists and policymakers are interested in salt marshes because they accumulate carbon in their soil over long time scales. This carbon would otherwise enter the atmosphere as carbon dioxide, exacerbating global climate change. However, microorganisms living in the soil break down some of this buried carbon and produce other greenhouse gases, such as methane, that contribute more to warming than carbon dioxide. Scientists have measured how much methane escapes from the soil to the atmosphere. Carbon burial more than offsets this methane export, meaning that salt marshes have a small net cooling effect on Earth's climate. In this study, we incorporate a previously unaccounted pathway for methane export from salt marshes into their radiative budget. Methane in marsh soil and surrounding sediments can be dissolved in groundwater that discharges from the pore spaces between soil and sediment particles. This groundwater flows slowly toward the marsh edge until it discharges into nearby surface waters, carrying dissolved methane with it. We estimate that this methane export from groundwater approximately doubles total methane emissions from salt marshes. This is still not enough methane export to counteract all of the climate cooling benefit of carbon burial in salt marsh soils. However, it is important for policymakers to include both pathways of methane export when calculating the climate cooling benefit of carbon burial in salt marsh soils or its economic value. Key Points: Submarine groundwater discharge drives methane export from salt marshes to adjacent coastal surface watersGroundwater‐derived methane export is similar in magnitude to the direct flux of methane from salt marsh soil to the atmosphereThis effective doubling of salt marsh methane export offsets ~30% of their carbon sequestration potential [ABSTRACT FROM AUTHOR]

Knowledge of roost selection by northern yellow bats (Lasiurus intermedius) is limited to a small number of known roost locations. Yet knowledge of basic life history is fundamental to understanding past response to anthropogenic change and to predict how species will respond to future environmental change. Therefore, we examined male northern yellow bat roost selection on 2 Georgia, USA, barrier islands with different disturbance histories. Sapelo Island has a history of extensive disturbance and is dominated by pine (Pinus spp.) forests; Little Saint Simons Island has a limited disturbance history with maritime oak (Quercus spp.) forest as the dominant cover type. From March–July 2012 and 2013, we radio‐tracked 35 adult male northern yellow bats to diurnal roosts and modeled roost characteristics at the plot and landscape scales. We located 387 roosts, of which 95% were in Spanish moss (Tillandsia usneoides) hanging in hardwood trees. On both islands, bats selected roost trees with larger diameters than surrounding trees and selected roost locations with greater open flight space (i.e., low midstory clutter) underneath. Roosts were located farther from open areas on Sapelo and closer to fresh water on Little Saint Simons compared to random locations. Lower availability of hardwood forest on Sapelo may have resulted in small‐scale roost site selection (i.e., plot level) despite potential increased costs of commuting to water and open areas for foraging. In contrast, greater availability of hardwood forest on Little Saint Simons likely allowed selection of roosts closer to fresh water, which provides foraging and drinking opportunities. Our results indicate that mature hardwood trees in areas with low midstory clutter are important in male northern yellow bat roost selection, but landscape‐level features have varying influences on roost selection, likely as a result of differences in disturbance history. Therefore, management will differ depending on the landscape context. Further research is needed to examine roost selection by females, which may have different habitat requirements. © 2020 The Wildlife Society. Mature hardwood trees in areas with low midstory clutter are important in male northern yellow bat roost selection at the plot level, but landscape‐level features have varying influences on roost selection. Management to provide suitable roosting habitat for male northern yellow bats should be tailored to specific landscape conditions. [ABSTRACT FROM AUTHOR]

Maritime forest communities on barrier islands along the Atlantic and Gulf coasts have been severely fragmented by a continuous history of human land use and natural disturbance. Isolated populations of certain tree species in maritime forest fragments may now be too small to be viable and their inability to regenerate may result in their eventual elimination from barrier islands. Using an 11-year study of a population of pignut hickory (Carya glabra), a common species of remnant maritime forest stands on St. Catherine's Island, Georgia, we present a case study of tree regeneration failure on a barrier island. We found that there has been no recruitment of new hickory individuals into the canopy of this population over the last 65 years. Field evidence of browse and a strong correlation between seedling density distributions and microsite protection from herbivory suggest that this trend in recruitment failure is related to an increased abundance of deer (Odocoileus) and pigs (Sus) on the island. Using a size class population projection model, we estimated that, if such recruitment failure and mortality rates continue, the hickory population will be extirpated from the maritime forest within 200 years. Tree species that are failing to regenerate within maritime forests represent a special challenge that is not currently being addressed in the long-term management of barrier island biodiversity. [ABSTRACT FROM AUTHOR]

The article focuses on a study described home range and habitat selection of an insular fallow deer, dama dama L., population on Little Saint Simons Island, Georgia. A total of six adult and one sub-adult deer were captured between April and July 2005. Habitat types were derived from an ecological community map and a digital color aerial photograph. The deer captured included to pregnant does and each reared a single fawn. Compositional analysis showed that deer used habitats differently than their availability at second deer selection. Overall, deer did not show differences in habitat selection between diurnal and nocturnal time periods.