Intertidal migration by the shore crab Carcinus maenas (L.) was studied on a seasonal and tidal basis from May to December 1992 on Ynys Faelog, Menai Strait, North Wales, UK. Work was carn e d out using a specially designed, remotely operated, unbaited directional trap, in conjunction with other conventional methods. Highly oriented migration was detected, with significantly more crabs taken in traps facing up-and downshore tidal flow than when facing against or 90" to flow. Facing-flow crab catches from falling tides were greater than those from rising tides. No significant differences were found in the numbers of daytime and nighttime migrants. Green (early intermoult) crabs were more attracted to bait than were red (late intermoult) crabs, food searching activity being extensive dunng times of flood bde, and rare dunng ebb hdes. Most crabs caught in the unbaited trap were green male early intermoults, and they were retneved more abundantly from the top half of the shore; female crabs were virtually absent from the lower shore. Upper-shore migrants were smaller than lower-shore migrants, which contained a higher proportion of late intermoult red crabs Crabs remaining on the shore at low tide were smaller than high-tide migrants, nearly all were green and they were located most abundantly around the midshore Numbers of both resident and migrant crabs declined between summer and winter.

Restoration of extirpated species via captive breeding has typically relied on population viability as the primary criterion for evaluating success. This criterion is inadequate when species reintroduction is undertaken to restore ecological functions and interactions. Herein we report on the demographic and ecological outcomes of a five-decade-long population restoration program for a critically endangered species of “ecosystem engineer”: the endemic Española giant Galapagos tortoise (Chelonoidis hoodensis). Our analysis of complementary datasets on tortoise demography and movement, tortoise-plant interactions and Española Island’s vegetation history indicated that the repatriated tortoise population is secure from a strictly demographic perspective: about half of tortoises released on the island since 1975 were still alive in 2007, in situ reproduction is now significant, and future extinction risk is low with or without continued repatriation. Declining survival rates, somatic growth rates, and body condition of repatriates suggests, however, that resources for continued population growth are increasingly limited. Soil stable carbon isotope analyses indicated a pronounced shift toward woody plants in the recent history of the island’s plant community, likely a legacy of changes in competitive relations between woody and herbaceous plants induced by now-eradicated feral goats and prolonged absence of tortoises. Woody plants are of concern because they block tortoise movement and hinder recruitment of cactus–a critical resource for tortoises. Tortoises restrict themselves to remnant cactus patches and areas of low woody plant density in the center of the island despite an apparent capacity to colonize a far greater range, likely because of a lack of cactus elsewhere on the island. We conclude that ecosystem-level criteria for success of species reintroduction efforts take much longer to achieve than population-level criteria; moreover, reinstatement of endangered species as fully functioning ecosystem engineers may often require large-scale habitat restoration efforts in concert with population restoration.

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Ecosystem specialists are predicted to be more vulnerable to global change than generalists, but whether specialists within an ecosystem will respond similarly to those changes is often largely unknown. Will specialists track changes in their habitats as a group, or are their distributions governed by landscape gradients that will make some species more sensitive to habitat changes? In this study, we forecasted the effects of sea level rise (SLR) on two salt marsh specialist bird species: clapper rails Rallus crepitans and seaside sparrows Ammodramus maritimus. We sampled the abundance of these two species in salt marshes throughout the Georgia, USA, coast in 2013-2014, and analyzed count data using a Bayesian N-mixture model. Model predictions were applied to an SLR land cover model to determine distribution shifts over 100 years. Both species distributions were most sensitive to the relative elevation gradient, with clapper rails using lower elevation marshes and seaside sparrows using higher elevation marshes. These disparities in habitat use, along with other differences according to marsh salinity and distance to forested areas, led to divergent responses to SLR. Clapper rail habitat is predicted to increase with SLR by 52%, but seaside sparrow habitat will contract by 81% by the year 2100. Seaside sparrow habitat is not predicted to decline until sometime between 2025 and 2050, at which point the decline will rapidly accelerate, indicating the importance of careful monitoring in future decades. Diverging responses to a global perturbation create a conservation planning dilemma: if specialists have opposing responses to SLR, it may be difficult to manage conservation areas that accommodate many species.

Loss of key plant-animal interactions (e.g., disturbance, seed dispersal, and herbivory) due to extinctions of large herbivores has diminished ecosystem functioning nearly worldwide. Mitigating for the ecological consequences of large herbivore losses through the use of ecological replacements to fill extinct species' niches and thereby replicate missing ecological functions has been proposed. It is unknown how different morphologically and ecologically a replacement can be from the extinct species and still provide similar functions. We studied niche equivalency between 2 phenotypes of Galápagos giant tortoises (domed and saddlebacked) that were translocated to Pinta Island in the Galápagos Archipelago as ecological replacements for the extinct saddlebacked giant tortoise (Chelonoidis abingdonii). Thirty-nine adult, nonreproductive tortoises were introduced to Pinta Island in May 2010, and we observed tortoise resource use in relation to phenotype during the first year following release. Domed tortoises settled in higher, moister elevations than saddlebacked tortoises, which favored lower elevation arid zones. The areas where the tortoises settled are consistent with the ecological conditions each phenotype occupies in its native range. Saddlebacked tortoises selected areas with high densities of the arboreal prickly pear cactus (Opuntia galapageia) and mostly foraged on the cactus, which likely relied on the extinct saddlebacked Pinta tortoise for seed dispersal. In contrast, domed tortoises did not select areas with cactus and therefore would not provide the same seed-dispersal functions for the cactus as the introduced or the original, now extinct, saddlebacked tortoises. Interchangeability of extant megaherbivores as replacements for extinct forms therefore should be scrutinized given the lack of equivalency we observed in closely related forms of giant tortoises. Our results also demonstrate the value of trial introductions of sterilized individuals to test niche equivalency among candidate analog species.

Sea level rise (SLR) may degrade habitat for coastal vertebrates in the Southeastern United States, but it is unclear which groups or species will be most exposed to habitat changes. We assessed 28 coastal Georgia vertebrate species for their exposure to potential habitat changes due to SLR using output from the Sea Level Affecting Marshes Model and information on the species' fundamental niches. We assessed forecasted habitat change up to the year 2100 using three structural habitat metrics: total area, patch size, and habitat permanence. Almost all of the species (n = 24) experienced negative habitat changes due to SLR as measured by at least one of the metrics. Salt marsh and ocean beach habitats experienced the most change (out of 16 categorical land cover types) across the three metrics and species that used salt marsh extensively (rails and marsh sparrows) were ranked highest for exposure to habitat changes. Species that nested on ocean beaches (Diamondback Terrapins, shorebirds, and terns) were also ranked highly, but their use of other foraging habitats reduced their overall exposure. Future studies on potential effects of SLR on vertebrates in southeastern coastal ecosystems should focus on the relative importance of different habitat types to these species' foraging and nesting requirements. Our straightforward prioritization approach is applicable to other coastal systems and can provide insight to managers on which species to focus resources, what components of their habitats need to be protected, and which locations in the study area will provide habitat refuges in the face of SLR.

32Species are being lost at an unprecedented rate due to human-driven environmental changes. The 33 cases in which species declared extinct can be revived are rare. However, here we report that a 34 remote volcano in the Galápagos Islands hosts many giant tortoises with high ancestry from a 35 species previously declared as extinct: Chelonoidis elephantopus or the Floreana tortoise. Of 150 36 individuals with distinctive morphology sampled from the volcano, genetic analyses revealed 37 that 65 had C. elephantopus ancestry and thirty-two were translocated from the volcano's slopes 38 to a captive breeding center. A genetically informed captive breeding program now being 39 initiated will, over the next decades, return C. elephantopus tortoises to Floreana Island to serve 40 as engineers of the island's ecosystems. Ironically, it was the haphazard translocations by 41 mariners killing tortoises for food centuries ago that created the unique opportunity to revive this 42 "lost" species today. 43 44

Hybridization poses a major challenge for species conservation because it threatens both genetic integrity and adaptive potential. Yet, hybridization can occasionally offer unprecedented opportunity for species recovery if the genome of an extinct taxon is present among living hybrids such that selective breeding could recapture it. We explored the design elements for establishing a captive‐breeding program for Galapagos tortoises (Chelonoidis spp.) built around individuals with admixed ancestry involving an extinct species. The target individuals were hybrids between the extinct species from Floreana Island, C. niger, and an extant species, C. becki, which were recently found in the endemic range of C. becki, from Wolf Volcano on Isabela Island. We combined genotypic data from 35 tortoises with high ancestry from C. niger with forward‐in‐time simulations to explore captive breeding strategies that maximized overall genetic diversity and ancestry from C. niger while accommodating resource constraints, species biology, and the urgency to return tortoises to Floreana Island for facilitating ecosystem restoration. Overall genetic diversity was maximized when in the simulation tortoises were organized in relatively small breeding groups. Substantial amounts of the C. niger genome were captured despite limited resources available for selectively breeding tortoises in captivity. Genetic diversity was maximized when captive‐bred offspring were released to the wild rather than being used as additional breeders. Our results provide genetic‐based and practical guidance on the inclusion of hybrids with genomic representation from extinct taxa into species restoration programs and informs the ongoing debate on the value of hybrids in biodiversity conservation.