Philip C Darby

• PhD
• Professor (Full) at University of West Florida

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 em...

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 aquar...

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. Whil...

Plant community structure and the creation of ecotones from the juxtaposition of distinct habitats influence gastropod distribution, abundance and species diversity. However, the influence of edge effects associated with ecotones May be influenced by scale and sampling issues. In Florida’s Everglades, a common ecotone exists between dense sawgrass...

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...

Apple snails (Ampullariidae) are among the largest and most ecologically important freshwater snails. The introduction of multiple species has reinvigorated the field and spurred a burgeoning body of research since the early 1990s, particularly regarding two species introduced to Asian wetlands and elsewhere, where they have become serious agricult...

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 expe...

Florida apple snails, Pomacea paludosa, are the nearly exclusive prey of the endangered snail kite, Rostrhamus sociabilis plumbeus. Declines in snail numbers have been documented in wetlands critical to snail kite populations and are especially concerning given the raptor's dependence on them. Stock enhancement of hatchery-reared snails into wild p...

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)...

Gastropod movements have been studied in the context of habitat selection, finding food and mates, and avoiding predation. Many of these studies were conducted in the laboratory, where constraints on spatial scale influence behavior. We conducted a field study of Florida apple snail (Pomacea paludosa) movements using telemetry. We hypothesized that...

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 populat...

The role of food abundance and vegetation structure in selection of foraging habitat by the Snail Kite (Rostrhamus sociabilis) was explored. Selection of available foraging patches of either dense or sparse habitat structure within two prairie habitat types used extensively by foraging kites, Eleocharis flats and Panicum flats were examined. Estima...

Pomacea paludosa (native Florida apple snail) is found in wetlands in the southeastern United States. Pomacea insularum is an exotic apple snail which has invaded wetlands in Florida and co-occurs with P. paludosa. The effect of changes in density on growth in native juvenile snails was studied by manip- ulating native juvenile density, native adul...

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...

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...

Nitrate pollution in springs in Florida has been suggested as a possible reason for declining populations of the Florida apple snail, Pomacea paludosa (Say). No correlation was found between snail density and nitrate concentration measured in six Florida springs. In laboratory studies examining short-term acute impacts of nitrate, adult and juvenil...

Water-level drawdown has long been recognized as an effective approach to enhance habitat conditions for aquatic fauna in lakes and impoundments. Although targeted species such as sport fish may benefit, increasingly there are concerns over nontarget species. We assessed the impacts of a drawdown of Lake Kissimmee on Florida apple snails. Prior to...

Previous reports concluded that Florida apple snails (Pomacea paludosa Say) have little tolerance to dry conditions, which stands in contrast to other Ampullariidae studied to date. Given that inconsistency, and the fact that we do find snails in wetlands that periodically dry down, we were interested in elucidating dry season survival patterns in...

Florida apple snails (Pomacea paludosa) apparently have only a limited tolerance to wetland drying events (although little direct evidence exists), but their populations routinely face dry downs under natural and managed water regimes. In this paper, we address speculation that apple snails respond to decreasing water levels and potential drying ev...

The endangered Florida snail kite (Rostrhamus sociabilis) feeds exclusively on applesnails (Pomacea paludosa), yet we lack direct observations that link applesnail behavior to snail kite foraging success. The purpose of our study was to evaluate the temperature-activity profile of applesnails in the context of restricted foraging opportunities for...

Traditional methods for sampling aquatic macro-invertebrates are very labor-intensive and largely ineffective when attempting to collect Florida applesnails (Pomacea paludosa) from their natural wetland habitats. We found the use of funnel traps an effective alternative that decreased collection time ten-fold and required considerably less labor th...

I developed a method for retrieving dropped radio transmitters in wetland and lake habitats. Magnets mounted on a pole altered the transmitter signal, thereby rapidly reducing the search area. Retrieval using the magnetic probe was tested using 15-g and 1.6-g transmitters under a variety of conditions. Using a magnetic probe, transmitter retrieval...

Despite the long recognized importance of apple snails (Pomacea paludosa Say) in Florida wetland food webs, surprisingly little is known about their life history and ecology. The paucity of information is due, in part, to the lack of a validated sampling technique. In this study, we compared the effectiveness of a dip net, bar seine, and suction dr...

1. Reduced glutathione (GSH), glutathione reductase (GSSG-reductase) and glutathione peroxidase (GSH-peroxidase) activities were measured in the gill and digestive gland of Rangia cuneata.2. Substantial GSH concentrations were found in both gill (820 ± 80 nmole/g tissue) and digestive gland (930 ± 130 nmole/g tissue). The digestive gland exhibited...

Typescript. Thesis (M.S.)--Duke University, 1990. Includes bibliographical references.