Ces dernières décennies, l'augmentation conjointe des populations de grands herbivores et des activités humaines de nature a donné lieu à de nouveaux enjeux de gestion du territoire conciliant objectifs de conservation et développement touristique. Afin de faire face à ce défi, les gestionnaires ont besoin de mieux comprendre les choix comportementaux qui sont à l’origine de la répartition spatiale des animaux et l’impact des activités humaines sur ces comportements. En prenant l'exemple du chamois (Rupicapra rupicapra), l'objectif de cette thèse est de répondre à ce besoin de connaissances sur le comportement spatial des grands herbivores, en prenant en compte d'une part la sélection des ressources alimentaires en fonction de l'hétérogénéité spatiale et de la dynamique de leur environnement, et d'autre part la réponse comportementale à l'influence de différents types d'activités récréatives de plein air. Nous avons tout d’abord modélisé le paysage alimentaire du chamois et ses variations saisonnières en combinant des données sur la végétation et sur le régime alimentaire à des données de télédétection. Puis à partir de 10 années de suivi de près de 100 animaux par collier GPS dans la Réserve de Chasse et de Faune Sauvage du massif des Bauges, nous avons démontré que les chamois ajustent leurs critères de sélection spatiale au cours du temps en fonction de l’évolution temporelle des caractéristiques de leur fourrage (qualité et quantité), notamment en fonction de leur variabilité ou caractère limitant. Ceci nous a amené à réévaluer le cadre d’application de deux hypothèses classiques en écologie spatiale des herbivores, l’hypothèse de la maturation du fourrage (Forage Maturation Hypothesis) et l’existence d’une réponse fonctionnelle dans la sélection d’habitat. Une des originalités de cette thèse est d’avoir pris en compte le caractère grégaire de cette espèce et de montrer comment la structure socio-spatiale de la population entraîne des variations locales du processus de sélection d’habitat, avec des implications démographiques fortes pour les individus. Nos résultats remettent en cause l’idée que les animaux se redistribuent au sein des populations en fonction des ressources disponibles, ce qui découle probablement de l’importance des relations sociales et du cout et des risques associés à la dispersion. Dans un second temps, nous avons abordé la thématique du dérangement du chamois face à trois activités humaines saisonnières, dont l’étude de la distribution dans notre site d’étude, à l’aide de GPS distribués aux pratiquants, a permis d’établir le paysage du dérangement pour les animaux. Le ski de randonnée et la marche à pied impactent clairement les déplacements des animaux, induisant une dépense énergétique supplémentaire. En revanche pour la chasse, la complexité de la réponse des chamois ne permet pas à l'heure actuelle de différentier l’impact des chasseurs de simples randonneurs, qui sont également présent sur le site en période de chasse. Ce travail se conclut par des propositions de gestion durable des populations sauvages compatibles avec la pratique des activités de loisirs de plein air. / These last decades, large herbivores population and outdoor human activities increased tremendously leading to the emergence of new challenges for the management of wild species and recreational activities, which need to reconcile conservation goals and tourist development. In order to face these challenges, wildlife managers need to better understand behavioral choice of animal that lead to their spatial distribution and how these behaviors are influenced by human activities. Based on chamois (Rupicapra rupicapra) as a study case, the aim of this PhD is to enhance our knowledge of spatial behavioral of large herbivores, on one hand by understanding individual selection for food resources according to resource spatial heterogeneity and their temporal dynamics, and on the other hand, by assessing the impact of human outdoor recreational activities on spatial behavior. We first modeled the foodscape of chamois and its seasonal variation by combining field data on vegetation and animal diet with remote sensing data. Then, based on a 10 years dataset of monitoring of >100 animals marked with GPS collars in the Game and Wildlife Reserve of the “massif des Bauges”, we demonstrated chamois adjusted their criteria for spatial selection through time according to the temporal evolution of their forage traits (quality and quantity), accounting notably whether these traits were variable or limiting. This led us to reevaluate the framework of two classical hypotheses in studies of herbivore spatial ecology, the “Forage Maturation Hypothesis” and the emergence of a functional response in habitat selection. One newness in our work is to have accounted for the gregariousness of this species, which allowed us to unveil that socio-spatial structure of the population induced local variation in the habitat selection process, with marked consequences on individual demographic performances. This challenges the idea that individuals should redistribute in space within a population according to available resources, probably because of the importance of social relationships and costs and risks associated with dispersal. Second, we investigated the response of chamois to disturbances resulting from 3 outdoor activities. We assessed the spatial use of recreationists by ditributing GPS-tracker from which we defined landscape of disturbance to animal. Ski touring and hiking both impacted animal movements, resulting in supplementary energetic expenditures. On the other hand, hunting induced complex spatial responses in chamois that need further investigation, as the response to hunters could not be differentiated from responses to hikers who continue to be on site even during the hunting period. We conclude this work with proposals for a better long-term management of wildlife compatible with the practice of outdoor recreational activities.

La plupart des écosystèmes sont aujourd'hui soumis à une pression anthropique croissante. Les études portant sur l'effet des activités humaines sur la biodiversité se multiplient mais elles se focalisent, principalement pour des raisons méthodologiques, sur un nombre restreint de groupes taxonomiques. L'originalité de ces travaux repose sur l'application d'une approche basée sur l'ADN environnemental permettant d'accéder à l'ensemble de la diversité biologique. Elle a ici été utilisée pour étudier l'impact des activités anthropiques sur les communautés biologiques et la résilience de ces dernières, à travers différentes échelles spatiales et temporelles. Dans une première partie, les communautés édaphiques, sous l'influence de diverses perturbations anthropiques, ont été caractérisées grâce à l'ADN contenu dans les sols. Ces études, réalisées dans différents milieux, mettent en évidence l'impact direct des activités humaines et leur influence sur les paramètres biotiques et abiotiques déterminant la distribution spatiale de la biodiversité des sols. La seconde partie se propose d'examiner l'impact à long terme des activités anthropiques au travers d'un exemple particulier en milieu de montagne. L'ADN contenu dans les archives sédimentaires lacustres a permis de retracer l'histoire des activités pastorales au cours de l'Holocène mais également les changements environnementaux que ceux-ci ont engendrés dans le bassin versant. L'approche mise en œuvre se révèle pertinente pour étudier à la fois les changements induits par les perturbations humaines sur les communautés et les facteurs influençant leurs dynamiques. Les résultats obtenus mettent notamment en lumière l'impact à long terme qu'exercent les activités anthropiques sur les communautés biologiques via les modifications profondes qu'elles génèrent sur les caractéristiques abiotiques du milieu. / Most ecosystems undergo an increasing anthropogenic pressure. Studies about the effects of human activities on biodiversity are proliferating but they focus on few taxonomical groups, mainly for methodological reasons. The originality of this work is based on the application of an approach based on environmental DNA that allows access to the biodiversity as a whole. It was used here to study the impact of anthropogenic activities on biological communities and the resilience of these latter, across different spatial and temporal scales. In the first part, edaphic communities under the influence of several human disturbances were characterized from soil DNA. These studies, performed in various environments, bring out the direct impact of human activities and their influence on biotic and abiotic parameters driving spatial distribution of soil biodiversity. In the second part, long-term impact of human activities was investigated through the analysis of lake sediments in the Alps. DNA from lacustrine sediments allowed to reconstruct livestock farming history over the Holocene and environmental changes that they induced in the catchment. We showed that this approach was relevant to study both changes generated by human disturbances on communities and factors driving their dynamics. Our results highlight the long-term impact of anthropogenic activities on biological communities, in relation to the alteration of environmental characteristics.

Apesar da reconhecida importância da fragmentação no balanço de carbono (C) das florestas tropicais, a maior parte do conhecimento a cerca deste assunto provém de estudos conduzidos na floresta Amazônica e desconsidera processos relacionados à influência da configuração da paisagem. Em particular, estimativas precisas da emissão de CO2 devido à fragmentação devem levar em consideração efeitos aditivos de borda e a idade das bordas. Nós investigamos estes efeitos sobre parâmetros estruturais de florestas (densidade, altura e área basal das árvores) e no estoque de C em oito fragmentos florestais (13 a 362 ha) antigos (>=70 anos), cercados de pastagens, em uma região de Mata Atlântica. Amostramos 5297 troncos, divididos em quatro tratamentos em cada um dos fragmentos: interior dos fragmentos; bordas antigas (>50 anos) em quina; bordas antigas retas; bordas novas (<50 anos) retas. Calculamos a biomassa acima do solo (BAS) através de equações alométricas que consideram a altura do tronco e seu diâmetro à altura do peito (DAP) e convertemos esse valor em carbono estocado na vegetação. O estoque de C foi altamente variável entre tratamentos, abrangendo valores entre 6.61 Mg ha-1 até 87.96 Mg ha-1 (média= 29.55 ± 14.97 Mg ha-1). As áreas de interior continham um estoque de C maior, bem como maior área basal, densidade de árvores e árvores mais altas do que as de borda. No entanto, a seleção de modelos não detectou influência da idade ou de efeitos aditivos no estoque de C. Nossos resultados sugerem que os padrões de efeitos de borda para a Mata Atlântica são diferentes dos observados em florestas tropicais fragmentadas mais recentemente, como é o caso da Amazônia. A Mata Atlântica tem um longo histórico de perturbação humana e uma dinâmica complexa de desmatamento e regeneração, que pode levar a uma condição de degradação generalizada, posto que até áreas mais distantes das bordas em manchas remanescentes de Mata Atlântica já perderam quantidades significativas de carbono. Nestas paisagens antrópicas, os efeitos de borda que atuam sobre a mortalidade de árvores e na redução da BAS podem ser mais abrangentes do que inicialmente estimado pelos modelos construídos para a floresta Amazônica. / Despite the importance of fragmentation for tropical forest carbon (C) balance, most of our knowledge comes from few sites in the Amazon and disregard underlying processes that relates landscape configuration with C stocks. Particularly, accurate estimation of CO2 emission from fragmentation must account for additive edge effects and edge age. Here we investigated those effects on carbon stock and forest structure (density, height, basal area) in eight old-growth forest (>=70 years) fragments (13 to 362 ha), surrounded by pasture, in the Brazilian Atlantic forest region. We sampled 5,297 stems in four distinct treatments, distributed in each fragment: fragment interiors; old (> 50 years) corner edge; old straight edge; and new (< 50 years) straight edge. Aboveground biomass (AGB) was estimated from tree height and diameter at breast height (DBH), and converted to carbon. C stock was highly variable between treatments, scoring from 6.61 Mg ha-1 up to 87.96 Mg ha-1 (average of 29.55 ± 14.97 Mg ha-1). Interior treatments had higher C stock, basal area, tree stem density and taller trees than edges. We found no significant effects of edge age or additive edge effects on C stocks. These results suggest that edge effects in the heavily-disturbed Atlantic rainforest may differ than those observed in more recently fragmented tropical forests, such as the Amazonian forest. In heavily human-modified landscapes, edge effects on tree mortality and reduction on AGB may contribute to overall higher levels of degradation across entire forest fragments, reducing the observed difference between edge and interior habitats, and suggesting that existing Amazonian forest models may underestimate the true impacts of tropical forest fragmentation for C storage.

No description available.

This research deals with the challenges of the conservation of tiger (Panthera tigris tigris) in the Chitwan National Park of Nepal and aims to be a model for tiger conservation in the tropical areas of other tiger range countries. Despite the high level of public concern and major investments during the last few decades for conservation, wild tigers continue to be under grave threat, and their preservation now requires, more than ever before, using reliable ecological knowledge for their conservation interventions. In this dissertation, I investigated various factors that affect on tiger conservation in this park: population status of prey, dietary patterns of tiger and its impact on sympatric carnivores (e.g., leopard) and increasing human-wildlife conflicts, effects of habitat structures and human disturbances on prey and predator species abundance and distribution.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2017-03-30T13:02:00Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação_Daniela_Reis_FINAL.pdf: 1679628 bytes, checksum: 38cb33a0301c9b8b0b881b5bee95a35c (MD5) / Made available in DSpace on 2017-03-30T13:02:00Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação_Daniela_Reis_FINAL.pdf: 1679628 bytes, checksum: 38cb33a0301c9b8b0b881b5bee95a35c (MD5) Previous issue date: 2016-02-25 / Universidade Federal de Pernambuco / Florestas Secas são ecossistemas expostos às perturbações antrópicas crônicas (PAC) e estão entre os mais ameaçados por mudanças climáticas devido às previsões de aumento de temperatura e redução de precipitação. Apesar de parecerem gradativos, os efeitos podem ser também bastante deletérios para a biota deste ecossistema. Neste estudo, foi investigado se o aumento da PAC e a redução da precipitação afetam a comunidade e populações de plantas com NEFs e os atributos morfo-anatômicos destas glândulas de duas espécies da Caatinga. O estudo foi realizado no Parque Nacional do Catimbau, onde os indivíduos com NEFs presentes em 19 parcelas ao longo de dois gradientes independentes de PAC e de precipitação foram marcados e suas espécies identificadas. Para análise anatômica foram coletadas amostras de glândulas de Poincianella microphylla e Pityrocarpa moniliformis. Foram encontradas 28 espécies pertencentes a 5 famílias. A composição de espécies variou apenas ao longo do gradiente de precipitação. As abundâncias de Senegalia bahiensis e Senna velutina aumentaram com a precipitação enquanto Po. microhylla e Sapium glandulosum diminuíram. Em relação aos atributos morfológicos, apenas a largura do tecido secretor e o comprimento e largura das glândulas de Pi. moniliformis foram relacionados positivamente com a precipitação e não com o gradiente de perturbação. Nossos resultados indicam que a disponibilidade de água é um fator chave para a Caatinga uma vez que o nível de precipitação local tem uma influência mais forte sobre comunidades e populações de plantas com NEF que a PAC. / Dry forests are exposed to chronic anthropogenic disturbances (CAD) and are one of the ecosystems most threatened by climate changes due to future previsions involving increasing in temperature and decreasing in rainfall. Besides the effects seem to be gradual, they can be seriously deleterious for the biota of this ecosystem. In this study was investigated if an increasing in CAD and a reduction in rainfall level affect the community and population of EFN-bearing plants and the morph-anatomical characters of these glands in Caatinga. The study was carried out at the National Park of Catimbau (Pernambuco, Brazil), where individuals with EFNs were found in 19 plots through two independent gradients of CAD and rainfall where species were marked and then identified. For the morph-anatomical analyses were collected glands surveys of Poincianella microphylla and Pityrocarpa moniliformis. It was found 28 species belonging to 5 families. Species composition changed only through the rainfall gradient. The abundances of Senegalia bahiensis and Senna velutina were positively related to the rainfall, as Po. microhylla and Sapium glandulosum were negatively related. In relation to the morphological attributes only the width of secretory tissue and the lenght of glands of Pi. moniliformis were positively related with the rainfall and not with the disturbance gradient. The results indicate that water availability is a key factor for Caatinga once the rainfall level has stronger influence on communities and populations of plants bearing EFNs than PAC do.

Population growth for species with long lifespans and low reproductive rates (i.e., K-selected species) is influenced primarily by both survival of adult females and survival of young. Because survival of adults and young is influenced by habitat quality and resource availability, it is important for managers to understand factors that influence habitat selection during the period of reproduction. My thesis contains two chapters addressing this issue for K-selected species in Utah. Chapter one evaluates habitat selection of greater sage-grouse (Centrocercusurophasianus) on Diamond Mountain during the critical nesting and brood-rearing period. Chapter two address selection of birth sites by bison (Bison bison) on Antelope Island, Utah. We collected micro-habitat data for 88 nests and 138 brood locations of greater sage-grouse from 2010-2012 to determine habitat preferences of nesting and brooding sage-grouse. Using random forests modeling techniques, we found that percent sagebrush, percent canopy cover, percent total shrubs, and percent obscurity (Robel pole) best differentiated nest locations from random locations with selection of higher values in each case. We used a 26-day nesting period to determine an average nest survival rate of 0.35 (95% CI = 0.23 – 0.47) for adults and 0.31 (95% CI = 0.14 – 0.50) for juvenile grouse.Brood sites were closer to habitat edges, contained more forbs and less rock than random locations. Average annual adult female survival across the two-year study period was 0.52 (95% CI= 0.38 – 0.65) compared to 0.43 (95% CI= 0.28 – 0.59) for yearlings.Brooding and nesting habitat at use locations on Diamond Mountain met or exceeded published guidelines for everything but forb cover at nest sites. Adult and juvenile survival rates were in line with average values from around the range whereas nest success was on the low end of reported values. For bison, we quantified variables surrounding 35 birth sites and 100 random sites during 2010 and 2011 on Antelope Island State Park. We found females selected birth sites based on landscape attributes such as curvature and elevation, but also distance to anthropogenic features (i.e., human structures such as roads or trails). Models with variables quantifying the surrounding vegetation received no support.Coefficients associated with top models indicated that areas near anthropogenic features had a lower probability of selection as birth sites. Our model predicted 91% of observed birth sites in medium-high or high probability categories. This model of birthing habitat, in cooperation with data of birth timing, provides biologists with a map of high-probability birthing areas and a time of year in which human access to trails or roads could be minimized to reduce conflict between recreation and female bison.

Cyclic and extreme ecological disturbances have the capacity to alter resources and thereby animal populations. Interactions between disturbance and resource availability can influence predator-prey interactions. Predator-prey responses to ecological disturbance may be more pronounced in herbivores and their predators as herbivores track food resources that are often augmented by ecological disturbance. My objective with this dissertation was to examine how various forms of ecological disturbance influence predator-prey interactions through the lens of a case study – white-tailed deer (Odocoileus virginianus) and Florida panther (Puma concolor coryi) in southwestern Florida public and conservation lands. I quantified species-specific behavior of deer to an extreme disturbance event (i.e., Hurricane Irma), examined behavior of females with different fate outcomes to varied ecological disturbances and predation, investigated how ecological disturbance mediates the influence of human disturbance on predator-prey interactions, and quantified deer spatial ecology in response to fire, hydrology, panther and human activity. I found that deer behaviorally mediated the negative fitness impacts of Hurricane Irma. Further, I found that female deer with different fate outcomes selected areas of different ecological disturbance and the ecological disturbance type conferred different fitness costs (through differences in predation risk). Finally, I found that South Florida deer utilize diurnal times when humans are the most active to temporally reduce predation risk as panthers were more nocturnal in response to humans. My work here suggests that ecological disturbance regimes have the capacity to influence predator-prey interactions through nuanced mechanisms. Outcomes of these nuanced species-specific and predator-prey responses should be examined further. More practically, if disturbance influences aspects of animal fitness, a deeper understanding of species-specific and predator-prey responses to disturbance will improve management and conservation efforts as some regimes can be manipulated (e.g., prescribed fire). More broadly, consideration of ecological disturbance when examining predator-prey interactions may yield novel insight that deviates from predictions based on inference suggested in systems without disturbance. Highlighting nuanced predator-prey interactions mediated by ecological disturbances will improve predictions regarding species and community responses to global changes such as climate change and ecological restoration. / Doctor of Philosophy / Events that cause temporary changes to ecosystem structure and function (ecological disturbances) have the capacity to influence resources (i.e., food and shelter) for wild animals. Changes in resources as a function of ecological disturbance has the capacity to influence prey and predator species interactions. Predator-prey responses to ecological disturbance may be more pronounced in plant-eating animals (herbivores) and their predators as herbivores utilize food resources that are often altered by ecological disturbance. My objective with this dissertation was to examine how various forms of ecological disturbance influence interactions between predators and prey by using the white-tailed deer (Odocoileus virginianus) and Florida panther (Puma concolor coryi) in southwestern Florida wildlands as a case study. I quantified species-specific behavior of deer to an extreme climate event (i.e., Hurricane Irma). Next, I quantified and compared behavioral differences in responses to ecological disturbance (flooding and fire) and panther predation risk between female deer that survived and those killed by panthers during the offspring rearing season. I also investigated how ecological disturbance and human use of wildlands influenced predator-prey interactions. Finally, I characterized deer behavior in response to fire, hydrology, and panther and human activity. I found that deer changed their behavior during Hurricane Irma, presumably to offset the negative impacts of the storm as all our monitored deer survived the event. Further, I found that different ecological conditions generated by fire and flooding, respectively, influenced female behavior during the offspring rearing season in response to predation risk, and those behavioral differences may explain differences in mortality outcomes. Finally, I found that South Florida deer utilize daylight hours when humans are the most active to minimize encounters with predators as panthers were shown to be more active at night in areas with greater human use. My findings suggest that ecological disturbances have the capacity to influence predator-prey interactions in novel ways not suggested elsewhere. Outcomes of novel predator and prey interactions in response to ecological disturbance should be investigated further. More practically, if disturbance influences aspects of animal livelihood, a deeper understanding of species-specific and predator-prey responses to disturbance will improve management and conservation efforts as some disturbances can be manipulated (e.g., prescribed fire). More broadly, consideration of ecological disturbance when examining predator-prey interactions may yield novel insight that deviates from predictions based on inference suggested in systems without disturbance. Highlighting novel predator-prey interactions that is changed as a result of ecological disturbances will improve predictions regarding species and community responses to global changes through climate change and ecological restoration.

Large carnivores are among the most challenging species to conserve in our modern and crowded world. Having large spatial requirements and living in low density, they generally require wide and relatively undisturbed areas. In Europe, one of the most anthropized areas of the planet, these needs must be fulfilled in a complex human-dominated landscape. The reintroduced brown bear population living in the Central Alps represents one of the most emblematic examples of a constrained carnivore: despite a steady population increase in the first few years after reintroduction, the population did not substantially expand its range, nor has the Alpine-Dinaric metapopulation been reestablished as envisioned. Although humans have lived in the Alps for centuries, little is known about their impact on the bear population. In other environments humans are known to function as a “super-predator” by changing habitats, competing for space, consuming resources, and harvesting, which alters the ecological niche of animals, especially large carnivores. This dissertation aims to evaluate this phenomenon by assessing the effects of human disturbance on brown bears in the Alps. Anthropogenic disturbance is generally assessed by structural proxies, such as infrastructure and land use, which overlook the impact of human presence. In the first Chapter, we developed the Cumulative Outdoor activity Index (COI) to derive anthropogenic disturbance using crowdsourced data by Strava and validated it with ground truth observations derived from a local camera trapping survey. The intensity of COI provided an effective measure of functional anthropogenic disturbance, and it outperformed all commonly-used proxies of structural disturbance in predicting bear habitat use. When displacement is not an option because of habitat limitations and social mechanisms, bear mobility may clash with human activity. During the moments of lowest mobility, such as resting periods, animals have decreased ability to cope with risky situations, and therefore the selection of suitable resting areas is crucial for the long-term survival of individuals. In the second Chapter, we measured multi-scale response to risk perception (i.e., COI) and resource proximity using bedding sites by GPS radio-collared adult brown bears in the Alps. To map resources across the study area, we developed a GIS-database combining spatial and non-spatial ecological information to map fruit availability. We observed that bears apply a security-food trade-off strategy, avoiding functional anthropogenic disturbance while in proximity to resources. In the third Chapter, we explicitly tested the effect of an abrupt interruption of human mobility during COVID-19 lockdown on bears’ use of ecological corridors. Using bear occurrences reported to local authorities during the recent COVID-19 outbreak, we observed that bears used human-dominated areas more frequently, approached more intensively hot spots for road crossing network, and used areas further from the population core areas more often than previous years, suggesting that connectivity increased with reduced human mobility. In a comparatively human-free system, for the fourth Chapter we used longitudinal morphometric data to analyze drivers of changes in body mass as part of an international collaboration with biologists studying the grizzly bear in the Greater Yellowstone Ecosystem. Specifically, we analyzed changes in lean body mass and fat percentage during years of major ecosystem perturbations. We observed that individual lean body mass during the last two decades was primarily associated with population density, but not body fat percentage, showing density-dependent factors. Our combined findings (Chapters 1-3) showed that brown bears have to adapt their space use, movement, and resource proximity as a result of functional anthropogenic disturbance. In Chapter 4 we explored one effect of unconstrained bear space use on individuals, as manifested through density-dependent effects on body size. In the Alps, however, we found multiple instances of the human-super predator outcompeting bears so as to make density-dependent effects likely less significant as compared to human-caused mortality. These effects could occur in a variety of socio-ecological contexts across Europe, jeopardizing the long-term establishment of both newly reintroduced bear populations, as well as spatially limiting those naturally present in the environment. In response to disturbance, bears have had to reduce their ecological niche in human-dominated landscapes. Allowing humans and bears to coexist in the same landscape is a challenging task, but it is essential for the long-term survival of this newly reintroduced population that are otherwise at risk of extinction.

<p>Management of predation on sea turtle nesting beaches is vital to conservation efforts for the vulnerable loggerhead turtles (<i>Caretta caretta</i>) and olive ridley turtles (<i>Lepidochelys olivacea</i>). Sea turtles increasingly face threats from invasive and human-tolerant mammalian predators as human disturbances on nesting beaches rises. The intensity of mammalian predation has increased in Las Baulas National Park in Costa Rica which is an important nesting site for several species of threatened and endangered sea turtles. I analyzed loggerhead and olive ridley nest predation on four beaches in the United States and Costa Rica that were chosen for variations in degree of human disturbance and management strategies. My objectives were to 1) determine if egg predation rates differ at the four sites, 2) determine the most destructive predators at each location, and 3) suggest management options to alleviate mammalian threats to turtle clutches on Playa Grande and Playa Cabuyal in Costa Rica. My results show that the beaches without a nest protection or predator control program had very high rates of predation. Invasive mammalian predators and mammalian predators associated with human disturbance were the most destructive at the four sites. I recommend that regulations regarding dogs and the take of eggs from the beach are enforced at Playa Cabuyal and that physical nest protection is rapidly implemented at Playa Grande. I also recommend that the National Park consider managing raccoon predation by removing problem individuals, but caution that they do so in a way that maintains the animals’ role in the ecosystem.</p>