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Whether or not a migratory songbird embarks on a long-distance flight across an ecological barrier is likely a response to a number of endogenous and exogenous factors. During autumn 2008 and 2009, we used automated radio tracking to investigate how energetic condition, age, and weather influenced the departure timing and direction of Swainson's thrushes (Catharus ustulatus) during migratory stopover along the northern coast of the Gulf of Mexico. Most birds left within 1 h after sunset on the evening following capture. Those birds that departed later on the first night or remained longer than 1 day were lean. Birds that carried fat loads sufficient to cross the Gulf of Mexico generally departed in a seasonally appropriate southerly direction, whereas lean birds nearly always flew inland in a northerly direction. We did not detect an effect of age or weather on departures. The decision by lean birds to reorient movement inland may reflect the suitability of the coastal stopover site for deposition of fuel stores and the motivation to seek food among more extensive forested habitat away from the barrier.

Broad variation in egg hatching success observed in gopher tortoise (Gopherus polyphemus) populations led us to investigate hatching success and other reproductive attributes within a unique, high-quality site in the eastern portion of the species' range. We documented use of a juvenile tortoise burrow as a nest site, a mean clutch size of 5.9 eggs, long oviposition-to-hatchling emergence times (96–128 d), and 73% hatching success for predator-protected eggs. Although consistent with previous reports of greater hatching success in eastern gopher tortoise populations than in western ones, hatching success at our eastern site was on the low end of values from other eastern populations, possibly reflecting above average rainfall during this study.

Adult North American tortoises (Gopherus spp.) engage in aggressive interactions with conspecifics when competing for mates and burrows. However, aggressive interactions have not been widely reported in hatchling and juvenile tortoises. We describe aggressive interactions between wild hatchling and juvenile gopher tortoises (Gopherus polyphemus) based on video recordings collected at tortoise burrows. Immature tortoises usually inhabited burrows alone but occasionally shared them. Presence of multiple individuals inside burrows hindered tortoise movements in burrows. Hatchlings or juveniles exhibited overt aggression toward similar aged/sized conspecifics in at least 6 of 13 (46%) encounters, and cameras may have failed to detect aggression occurring inside burrows. Hatchlings and juveniles also exhibited aggressive responses to foreign objects that were similar in appearance to small tortoises. Aggressive behaviors resembled those of adults and included repeated ramming, pushing, biting, and flipping. Young tortoises may respond aggressively to conspecifics at burrows because the presence of additional individuals constrains thermoregulatory and antipredator movements within these important microhabitats. Social interactions appear to play a greater role in the ecology of hatchling and juvenile gopher tortoises than previously recognized.

Researchers often employ radio telemetry to locate study animals efficiently, but the time required to locate individuals can make monitoring large populations difficult and costly. In 2010–2011 we located nesting ornate box turtles (Terrapene ornata) in a large group of radio-tagged animals. To minimize search efforts, we investigated whether automated radio telemetry and the signal change method could be used to identify nesting activity before locating animals. The signal change method relies on the principle that any movement of a radio transmitter, including minor changes in orientation, can strongly affect the intensity of the transmitter's signal at a stationary receiving station. Using video recordings of free-ranging radio-tagged turtles, we confirmed that transmitter signal strength values can be analyzed to identify periods of box turtle activity. Early in the 2010 nesting season, automated telemetry observations indicated that some females engaged in nocturnal activity. Previous reports indicate that ornate box turtles often nest at night but are otherwise inactive after dark. Based upon this information and relatively little indication of nocturnal activity by males, we hypothesized that nocturnal activity corresponded to nesting. We subsequently monitored female nighttime activity in near real time, hand-tracked four night-active individuals, and found three of these turtles nesting. In 2011 we again selectively hand-tracked night-active females and located nests for 12 of 18 study animals, which approximates the expected annual reproductive rate for our population. We demonstrate that the signal change method can be used to identify nesting activity in ornate box turtles and suggest this method may be of use in other species that nest outside of their normal activity periods.

The effect of commercial fisheries on nontarget species is a burgeoning issue for both fishery managers and estuarine biologists. We documented diamondback terrapin (Malaclemys terrapin) bycatch in cloth-funnel eel pots used in a Maryland (United States) commercial American eel (Anguilla rostrata) fishery. Between 1992 and 2001, we obtained 40 male and 9 female terrapin captures and 1 male terrapin recapture from commercial eel pots. To quantify terrapin catch rates and evaluate a potential solution to terrapin bycatch in eel pots, we conducted two experiments that tested the effects of a novel eel pot bycatch reduction device on terrapin bycatch and eel harvest. We determined low terrapin bycatch rates (0.000-0.008 terrapins pot-1d-1) in pots with small entrance funnels and high terrapin capture rates (0.458 terrapins pot-1d-1) in pots with large entrance funnels. The BRD eliminated terrapin bycatch and had no effect on eel catch making it an economically-viable solution for terrapin mortality in eel pots. We demonstrated that terrapin bycatch can be a problem in the American eel pot fishery and that our bycatch reduction device is a simple and cost-effective solution to this problem.

We used an experiment and regression analyses to quantify effects of spatial variation in habitat structure abundance on a riverine macroinvertebrate community under winter conditions. Concrete slabs (0.21 m2; n = 24) with different numbers of stones (mean individual stone surface area = 6.44 cm2) attached to upper faces were placed in the James River and retrieved after 28 d. Macroinvertebrate abundance and taxonomic richness on slabs were significantly positively related to stone abundance. Total macroinvertebrate abundance and abundance of oligochaetes (Nais spp.), Asiatic clams (Corbicula fluminea), caddisflies (Leptoceridae), riffle beetles (Elmidae) and stoneflies (Strophopteryx sp.) were linearly related to stone abundance. However, nonlinear relationships occurred between stone abundance and macroinvertebrate taxonomic richness and between stone abundance and abundance of dragonflies (Erpetogomphus sp.), caddisflies (Hydropsychidae), chironomids (Eukiefferiella spp.), mayflies (Ephemerellidae) and stoneflies (Taeniopteryx sp.). Nonlinear relationships were usually characterized by dramatic increases in macroinvertebrate abundance and taxonomic richness across a gradient of increasing stone abundance when abundance was low (0–43 stones/0.08 m2 slab face; 0–40% of slab face covered by stones), but weak responses to additional stones at higher stone abundance (84–160 stones/0.08 m2; 89–96% cover). These nonlinear relationships reflected similar nonlinear relationships between abundance of stones and particulate matter. We conclude that small quantities of habitat structure have significant positive effects on macroinvertebrate abundance and diversity in the James River during winter. At a local scale, habitat structure promotes macroinvertebrate colonization and retention by increasing habitat diversity. Stones and similar physical objects also indirectly benefit macroinvertebrates by trapping particulate matter that provides animals with food and additional habitat.

Few terrestrial vertebrate ectotherms are strictly herbivorous, and those that are tend to inhabit tropical or warm desert environments, presumably reflecting thermal constraints on digestion of plant matter via fermentation. However, the imperiled gopher tortoise (Gopherus polyphemus) of the southeastern United States is solely herbivorous and often occupies shaded forests. Its ancestral environment is hypothesized to have consisted largely of warmer semi-open canopy longleaf pine (Pinus palustris ) forests, but fire suppression and other factors have led to grand scale conversion of this highly biodiverse ecosystem to more shaded habitats. I investigated thermoregulatory strategies, thermal constraints on growth, and antipredator behavior of neonate, hatchling, and juvenile gopher tortoises in a longleaf pine forest of southwest Georgia. My findings indicate young gopher tortoises exploit most thermal opportunities available at burrows, basking increases growth rates, and low environmental temperatures likely constrain growth throughout the active season. Extensive basking begins at the neonate stage, where young exhibit a high-basking, rapid-growth strategy that exposes them to predation risk during thermoregulatory activity, but is presumably optimal overall. Although young bask extensively, their body temperatures may be particularly influenced by shade because they limit this activity to just in front of burrows. The field and laboratory data also suggest that tortoise body temperatures and thermosensitivity of growth are such that small changes in environmental temperature, including those that could be incurred by increased shading or climate change can substantially impact growth rates and time spent at small body sizes, where individuals are most susceptible to predators. Although young tortoises can increase growth rates by basking, surface activity also increases exposure to predators. Individuals appear to manage predation risk by limiting most basking to burrow aprons and entrances, remaining vigilant, and quickly hiding belowground in response to potential predators. Simulated predator approaches on basking hatchlings and juveniles revealed very long flight initiation distances, which increased strongly with size/age, and apparent use of vibrations (aerial or ground) to detect and avoid danger, providing a possible ecological function for uniquely large otolith ear bones characteristic of this species. Consistent with the hypothesis that young exploit most thermal opportunities available at burrows to maximize growth, disturbed individuals hid for short durations, especially when using cool burrows. Similarly, surface activity during the hour following disturbance correlated negatively with burrow temperature. Tortoises raised in captivity during the first year of their lives for thermal physiology experiments also exhibited a high-basking, rapid-growth strategy and generally normal antipredator responses following hard release back into the field. Taken together, behavior, physiology, and environmental temperatures indicate warmer environments can reduce neonate–juvenile exposure to predators by increasing growth rates and, at least during certain times of the year, decreasing surface activity.