<p>A vast range of theoretical and empirical studies now suggests that MPAs can conserve marine biodiversity and, under some circumstances, increase fishery yields. However, despite the importance of pelagic apex predators to ecosystem function, the effectiveness of spatial management for the conservation of pelagic apex predator species is still unknown. I used fishery-dependent logbook and observer datasets to assess fishing effort and both the catch and size of pelagic apex predator species around five different MPAs. The US Hawaii-based deep-set or Atlantic pelagic longline fisheries fish the waters around these MPAs; both of these fisheries have experienced multiple management measures over time to protect species and maximize fishery yield. The MPAs selected for this study range in size, age, level of protection, and reason for establishment. I found that only two MPAs of the five appeared to be benefitting the pelagic apex predator species that I selected: the DeSoto Canyon and East Florida Coast MPAs, both in the Atlantic Ocean. The size of yellowfin tuna around the DeSoto Canyon MPA borders has increased over time, as has fishing effort. In contrast, the size of swordfish has decreased near the boundary of the East Florida Coast MPA, although the catch of swordfish has increased. The increase in catch of smaller swordfish was not a surprise because the East Florida Coast MPA was established around an area that is a nursery habitat for swordfish. These results are promising for the use of static MPAs for the conservation of pelagic apex predators, but three of the MPAs in my study did not show any indication of increased fishing effort, increased catch, or changes in pelagic apex predator size near their boundaries over time. Therefore, the characteristics of the DeSoto Canyon and East Florida Coast MPAs may provide a template for how to best design new MPAs for pelagic apex predators. Both of these MPAs were established with the specific intent of reducing pelagic apex predator bycatch, in areas where there were historically high catch rates. Both areas are relatively large (> 85,000 km2) and are also closed year-round. In combination, these characteristics may provide protection for pelagic apex predators.</p> / Dissertation

Top predators can have large effects on community and population dynamics but we still know relatively little about their roles in ecosystems and which biotic and abiotic factors potentially affect their behavioral patterns. Understanding the roles played by top predators is a pressing issue because many top predator populations around the world are declining rapidly yet we do not fully understand what the consequences of their potential extirpation could be for ecosystem structure and function. In addition, individual behavioral specialization is commonplace across many taxa, but studies of its prevalence, causes, and consequences in top predator populations are lacking. In this dissertation I investigated the movement, feeding patterns, and drivers and implications of individual specialization in an American alligator (Alligator mississippiensis) population inhabiting a dynamic subtropical estuary. I found that alligator movement and feeding behaviors in this population were largely regulated by a combination of biotic and abiotic factors that varied seasonally. I also found that the population consisted of individuals that displayed an extremely wide range of movement and feeding behaviors, indicating that individual specialization is potentially an important determinant of the varied roles of alligators in ecosystems. Ultimately, I found that assuming top predator populations consist of individuals that all behave in similar ways in terms of their feeding, movements, and potential roles in ecosystems is likely incorrect. As climate change and ecosystem restoration and conservation activities continue to affect top predator populations worldwide, individuals will likely respond in different and possibly unexpected ways.

Birds face many challenges from the process of urbanisation. Those species that are able to occupy urban areas offer opportunities to understand processes of acclimatisation to urban life and may help in the development of urban spaces for the benefit of wildlife. In many bird species, individuals that occupy territories in more urban areas show lower productivity and lower body condition of nestlings, which is thought to be mediated by food availability. Most of the studies exploring this issue were done on passerines and carried out in the global north, with very few studies exploring this topic on non-passerines, and even fewer in Africa. Studies addressing urban productivity in apex predators with slow life histories that are often of conservation concern are largely missing. Here, we explore the breeding performance of the African Crowned Eagles (Stephanoaetus coronatus) across an urbanisation gradient in KwaZuluNatal, South Africa. Specifically, we explored the hypothesis that living in an urban environment allows this species, which is typically a biennial breeder, to breed annually more often (i.e. increased breeding rate), and whether this might increase the productivity of this species. We also explore whether there may be any hidden costs of such a breeding strategy by examining the condition of chicks for pairs which had successfully bred in the previous year. We found that Crowned Eagles breeding in more urban areas attempted to breed more often (i.e., higher breeding rate), but that these birds also suffered from lower breeding success. These two contrasting responses counteracted each other and meant that overall productivity (number of young produced per occupied territory) was not influenced by urbanisation. Breeding annually did not appear to have a negative cost on the chick condition, as offspring in the year following a successful breeding attempt did not have lowered body condition. This species appears to be well adjusted to breeding in an urban environment. Crowned Eagles are currently considered vulnerable in South Africa, and ensuring that an urban population of this species is able to persist can help secure the conservation status of this charismatic species.

Mounting evidence suggests that large carnivores regulate the abundance and diversity of species at multiple trophic levels through cascading top-down effects. The fear large carnivores inspire in their prey may be a critical component of these top-down effects, buffering lower trophic levels from overconsumption by suppressing large herbivore and mesopredator foraging. However, the evidence that the fear of large carnivores cascades through food webs has been repeatedly challenged because it remains experimentally untested. My collaborators and I exploited a natural experiment – the presence or absence of mesopredator raccoons (Procyon lotor) on islands in the Gulf Islands of British Columbia, Canada – to examine the breadth of mesopredator impacts in a system from which all native large carnivores have been extirpated. By comparing prey abundance on islands with and without raccoons, we found significant negative effects of raccoon presence on terrestrial (songbirds and corvids), intertidal (crabs and fish) and shallow subtidal (red rock crabs Cancer productus) prey, demonstrating that, in the absence of native large carnivores, mesopredator impacts on islands can extend across ecosystem boundaries to affect both terrestrial and marine communities. To test whether fear of large carnivores can mitigate these community-level impacts of mesopredators, we experimentally manipulated fear in free-living raccoon populations using month-long playbacks of large carnivore vocalizations and monitored the effects on raccoon behaviour and the intertidal community. Fear of large carnivores reduced raccoon foraging to the benefit of the raccoon’s prey, which in turn affected a competitor and prey of the raccoon’s prey. By experimentally restoring the fear of large carnivores in our study system, we succeeded in reversing the impacts of raccoons, reinforcing the need to protect large carnivores given the conservation benefits the fear of them provides. Our experimental work demonstrated that fine-scale behavioural changes in prey in response to predation risk can have community-level effects relevant to biodiversity conservation. However, experimentally testing animal responses to predators and other sources of risk in free-living wildlife presents considerable logistical challenges. To address these challenges, my collaborators and I developed an Automated Behavioural Response system, which integrates playback experiments into camera trap studies, allowing researchers to collect experimental data from wildlife populations without requiring the presence of an observer. Here I describe tests of this system in Uganda, Canada and the USA, and discuss novel research opportunities in ecology and conservation biology made available by this new technology. / Graduate

Predadores de topo desempenham um papel importante na manutenção dos sistemas em que eles ocorrem porque influenciam diretamente a estrutura e a dinâmica de comunidades. Desta forma, este estudo descreveu alguns mecanismos de co-ocorrência espaço-temporal entre a onça-pintada (Panthera onca) e duas espécies de mesopredadores (Puma concolor e Leopardus pardalis), o seu controle top-down na comunidade de mamíferos e os requerimentos ambientais que determinam a sua distribuição no bioma Amazônia. Para as análises de co-ocorrência espaço-temporal foram utilizados o modelo de ocupação e a densidade de Kernel utilizando os registros de armadilhamento fotográfico (2008-2011). Para descrever o controle top-down foi elaborada uma rede trófica utilizando os itens alimentares consumidos pelas espécies e disponíveis na literatura (1983-2014). Para indicar quais as áreas mais adequadas foi utilizado o modelo de distribuição de espécies utilizando as localizações geográficas de ocorrência da espécie que foram compiladas de três diferentes bases de dados (2000-2013). A ocorrência das duas espécies de mesopredadores não foi diferente nos sítios com e sem a onça-pintada nas quatro temporadas de amostragem. A probabilidade de detecção da jaguatirica foi maior nos sítios com a presença da onça-pintada em apenas uma temporada de amostragem. A sobreposição no período de atividade das espécies de mesopredadores com a onça-pintada foi baixa, com cerca de 55% de sobreposição. Também ocorreu uma mudança razoável no período de atividade das espécies entre as temporadas de amostragem, com mínima de 32% e máxima de 56% de sobreposição. As maiores diferenças na detecção e na sobreposição temporal ocorreram na terceira temporada quando teve o maior número de capturas e recapturas da onça-pintada. A rede trófica apresentou seis níveis e grande riqueza de espécies e densidade de interações. Após a remoção da onça-pintada, houve a perda de um nível trófico e de aproximadamente 20% de interações. Quando comparada a distribuição atual da onça-pintada com a histórica, foi possível constatar a perda de espaço ambiental em áreas mais frias (< 6,3 °C), mais secas (< 288 mm), mais úmidas (> 7517 mm) e com maior elevação (> 3597 m). O modelo de distribuição também indicou que muitas áreas potenciais estão disponíveis à ocorrência da onça-pintada e que algumas merecem atenção, especialmente, nas porções leste e sul da Amazônia onde a espécie corre maior risco de desaparecimento local devido à antropização acelerada. Este estudo forneceu significativa contribuição para a compreensão da população de onça-pintada na Amazônia, bioma que ainda possui a maior lacuna de conhecimento sobre a biologia e ecologia da espécie. Demonstrou o efeito da sua presença na detectabilidade e no período de atividade de outras espécies. Também demonstrou seu papel ecológico como predador de topo exclusivo porque foi a única espécie que predou todas as outras de níveis tróficos inferiores. Descreveu o espaço ambiental originalmente ocupado (distribuição histórica) e o perdido (distribuição atual). Indicou as áreas mais adequadas à sua ocorrência e aquelas potenciais ao seu desaparecimento. / Apex predators play an important role in the maintenance of systems in which occur because they directly influence the structure and dynamics of communities Thus, this thesis aims to describe some of the mechanisms of spatio-temporal co-occurrence between the jaguar (Panthera onca) and mesopredators (Puma concolor and Leopardus pardalis), their top-down control on the community and environmental requirements that determine their distribution. To the analyses of spatio-temporal co-occurrence were used the occupancy model and the Kernel density with records derived from camera trapping (2008-2011). To the analysis of trophic networks was used a foodweb model with prey spectra of felids compiled from the available literature (1983-2014). To indicate the most suitable areas to its occurrence was used a species distribution model with geographic location of the species compiled from three different databases. The occupation of the two species of mesopredators was not different among sites with and without jaguar. The probability of detection was different for ocelot, with higher detection on sites with than without jaguar. The overlap in the activity pattern among jaguar and mesopredators was low, with approximately 55% of overlapping. Also there was a reasonable change in the overlap between sampling seasons, with a minimum of 32% and maximum of 56% of the difference in the activity pattern. The differences in the detection and temporal overlap occurred in the third season when occurred the highest number of jaguar captures and recaptures. The trophic network presented six levels and, a high species richness and links density. After removal of the jaguar, a trophic level and approximately 20% of links were lost. When compared historical and current distributions, the loss of environmental space occurred in areas colder (< 6.3 ° C), drier (< 288 mm), wetter (> 7517 mm) and at higher elevation (> 3597 m). The distribution model also indicated that there is many potential suitable areas available to the jaguar occurrence and, some of them deserve attention, particularly, in eastern and southern portions of Amazonia where the species is most at risk of local extinction. This study provided a significant contribution to the knowledge of the population of jaguar in the Amazon biome which still has the largest gap of information on the biology and ecology of the species. It demonstrated the effect of the presence of the species in the detectability and the activity pattern of others. Also, it demonstrated their ecological role as an apex predator exclusive because it was the only one that ate all other species of lower trophic levels. It described the environmental space originally occupied (historical distribution) and lost (current distribution). It indicated potential suitable areas to its occurrence and threatened areas to its disappearance.

Predadores de topo desempenham um papel importante na manutenção dos sistemas em que eles ocorrem porque influenciam diretamente a estrutura e a dinâmica de comunidades. Desta forma, este estudo descreveu alguns mecanismos de co-ocorrência espaço-temporal entre a onça-pintada (Panthera onca) e duas espécies de mesopredadores (Puma concolor e Leopardus pardalis), o seu controle top-down na comunidade de mamíferos e os requerimentos ambientais que determinam a sua distribuição no bioma Amazônia. Para as análises de co-ocorrência espaço-temporal foram utilizados o modelo de ocupação e a densidade de Kernel utilizando os registros de armadilhamento fotográfico (2008-2011). Para descrever o controle top-down foi elaborada uma rede trófica utilizando os itens alimentares consumidos pelas espécies e disponíveis na literatura (1983-2014). Para indicar quais as áreas mais adequadas foi utilizado o modelo de distribuição de espécies utilizando as localizações geográficas de ocorrência da espécie que foram compiladas de três diferentes bases de dados (2000-2013). A ocorrência das duas espécies de mesopredadores não foi diferente nos sítios com e sem a onça-pintada nas quatro temporadas de amostragem. A probabilidade de detecção da jaguatirica foi maior nos sítios com a presença da onça-pintada em apenas uma temporada de amostragem. A sobreposição no período de atividade das espécies de mesopredadores com a onça-pintada foi baixa, com cerca de 55% de sobreposição. Também ocorreu uma mudança razoável no período de atividade das espécies entre as temporadas de amostragem, com mínima de 32% e máxima de 56% de sobreposição. As maiores diferenças na detecção e na sobreposição temporal ocorreram na terceira temporada quando teve o maior número de capturas e recapturas da onça-pintada. A rede trófica apresentou seis níveis e grande riqueza de espécies e densidade de interações. Após a remoção da onça-pintada, houve a perda de um nível trófico e de aproximadamente 20% de interações. Quando comparada a distribuição atual da onça-pintada com a histórica, foi possível constatar a perda de espaço ambiental em áreas mais frias (< 6,3 °C), mais secas (< 288 mm), mais úmidas (> 7517 mm) e com maior elevação (> 3597 m). O modelo de distribuição também indicou que muitas áreas potenciais estão disponíveis à ocorrência da onça-pintada e que algumas merecem atenção, especialmente, nas porções leste e sul da Amazônia onde a espécie corre maior risco de desaparecimento local devido à antropização acelerada. Este estudo forneceu significativa contribuição para a compreensão da população de onça-pintada na Amazônia, bioma que ainda possui a maior lacuna de conhecimento sobre a biologia e ecologia da espécie. Demonstrou o efeito da sua presença na detectabilidade e no período de atividade de outras espécies. Também demonstrou seu papel ecológico como predador de topo exclusivo porque foi a única espécie que predou todas as outras de níveis tróficos inferiores. Descreveu o espaço ambiental originalmente ocupado (distribuição histórica) e o perdido (distribuição atual). Indicou as áreas mais adequadas à sua ocorrência e aquelas potenciais ao seu desaparecimento. / Apex predators play an important role in the maintenance of systems in which occur because they directly influence the structure and dynamics of communities Thus, this thesis aims to describe some of the mechanisms of spatio-temporal co-occurrence between the jaguar (Panthera onca) and mesopredators (Puma concolor and Leopardus pardalis), their top-down control on the community and environmental requirements that determine their distribution. To the analyses of spatio-temporal co-occurrence were used the occupancy model and the Kernel density with records derived from camera trapping (2008-2011). To the analysis of trophic networks was used a foodweb model with prey spectra of felids compiled from the available literature (1983-2014). To indicate the most suitable areas to its occurrence was used a species distribution model with geographic location of the species compiled from three different databases. The occupation of the two species of mesopredators was not different among sites with and without jaguar. The probability of detection was different for ocelot, with higher detection on sites with than without jaguar. The overlap in the activity pattern among jaguar and mesopredators was low, with approximately 55% of overlapping. Also there was a reasonable change in the overlap between sampling seasons, with a minimum of 32% and maximum of 56% of the difference in the activity pattern. The differences in the detection and temporal overlap occurred in the third season when occurred the highest number of jaguar captures and recaptures. The trophic network presented six levels and, a high species richness and links density. After removal of the jaguar, a trophic level and approximately 20% of links were lost. When compared historical and current distributions, the loss of environmental space occurred in areas colder (< 6.3 ° C), drier (< 288 mm), wetter (> 7517 mm) and at higher elevation (> 3597 m). The distribution model also indicated that there is many potential suitable areas available to the jaguar occurrence and, some of them deserve attention, particularly, in eastern and southern portions of Amazonia where the species is most at risk of local extinction. This study provided a significant contribution to the knowledge of the population of jaguar in the Amazon biome which still has the largest gap of information on the biology and ecology of the species. It demonstrated the effect of the presence of the species in the detectability and the activity pattern of others. Also, it demonstrated their ecological role as an apex predator exclusive because it was the only one that ate all other species of lower trophic levels. It described the environmental space originally occupied (historical distribution) and lost (current distribution). It indicated potential suitable areas to its occurrence and threatened areas to its disappearance.

As climate change continues, climactic extremes are predicted to become more frequent and intense, in some cases resulting in dramatic changes to ecosystems. The effects of climate change on ecosystems will be mediated, in part, by biotic interactions in those ecosystems. However, there is still considerable uncertainty about where and how such biotic interactions will be important in the context of ecosystem disturbance and climactic extremes. Here, I review the role of consumers in seagrass ecosystems and investigate the ecological impacts of an extreme climactic event (marine heat wave) and subsequent widespread seagrass die-off in Shark Bay, Western Australia. Specifically, I compare seagrass cover, shark catch rates, and encounter rates of air breathing fauna in multiple habitat types before and after the seagrass die-off to describe post-disturbance dynamics of the seagrass community, shifts in consumer abundances, and changes in risk-sensitive habitat use patterns by a variety of mesoconsumers at risk of predation from tiger sharks (Galeocerdo cuvier). Finally, I conducted a 16 month field experiment to assess whether xi loss of top predators, and predicted shifts in dugong foraging, could destabilize remaining seagrass. I found that the previously dominant temperate seagrass Amphibolis antarctica is stable, but not increasing. Conversely, an early-successional tropical seagrass, Halodule uninervis, is expanding. Following the die-off, the densities of several consumer species (cormorants, green turtles, sea snakes, and dugongs) declined, while others (Indo-Pacific bottlenose dolphins, loggerhead sea turtles, tiger sharks) remained stable. Stable tiger shark abundances following the seagrass die-off suggest that the seascape of fear remains intact in this system. However, several consumers (dolphins, cormorants) began to use dangerous but profitable seagrass banks more often following seagrass decline, suggesting a relaxation of anti-predator behavior. Experimental results suggest that a loss of tiger sharks would result in a behaviorally mediated trophic cascade (BMTC) in degraded seagrass beds, further destabilizing them and potentially resulting in a phase shift. My work shows that climactic extremes can have strong but variable impacts on ecosystems mediated in part by species identity, and that maintenance of top predator populations may by important to ecological resilience in the face of climate change.

Killer whales are the oceans’ apex predator and are known to have important effects on ecosystems. At Subantarctic Marion Island, southern Indian Ocean, they have only been studied opportunistically, resulting in limited knowledge of their ecosystem impact here. This dissertation describes the prey and seasonal abundance, estimates the population size and assesses the predatory impact of killer whales on seals and penguins at Marion Island, using dedicated and opportunistic shore-based observations and photographic identification, from 2006 to 2009. During 823 sightings of killer whales at Marion Island (2006 to 2009) 48 predation events were recorded; in only 10 cases could prey be identified. Killer whales fed on fur seals, elephant seals and penguins. Constant effort (dedicated) observations (259 hours, 2008 to 2009) showed that killer whale abundance, which peaked in September to December with a secondary peak in April to May, is linked to the abundance of seals and penguins. Mark-recapture analyses were performed using nearly 10 000 photographs taken from 2006 to 2009. Following careful quality control criteria 37 individuals were identified and a population size of 42 (95% CI = 35-50) individuals estimated using the open population POPAN parameterization in the software program MARK. The analytical approach is more rigorous than that used in any previous population size assessment at Marion Island. Finally, the above data were integrated to assess whether top-down control of seal and penguin populations at Marion Island is generally plausible using a simple process of elimination. Based on published data I predicted the energetic ingestion requirements of adult male and female killer whales as 1 394 MJ.day-1 and 1 028 MJ.day-1, respectively. Expanding these requirements to the 37 killer whales photographically identified at Marion Island, the population requires 40 600MJ.day-1. Based on available energy density and mass data, I predicted the energy content of available seal and penguin prey and calculated the rates at which killer whales would consume these prey in various scenarios. Penguins and Subantarctic fur seals are relatively insensitive to killer whale predation owing to their large population sizes (10 000s to 100 000s), conversely, the smaller populations (100s to 1 000s) of Antarctic fur seals and southern elephant seals are sensitive to predation, particularly the latter as they have a high energy content (approximately 2 000 to 9 000 MJ). Populations of these seals are currently increasing or stable and I conclude that presently killer whale predation is not driving population declines, although they clearly have the potential for regulation of these smaller populations. Thus, if population sizes were reduced by bottom-up processes, if killer whale diet shifted, or if prey availability changed, top-down control by killer whales could become significant. This study provides baseline information for the informed management and conservation of killer whales at Marion Island, identifies avenues for further research, and provides a foundation for the continuation of structured and dedicated killer whale research at Marion Island. / Dissertation (MSc)--University of Pretoria, 2011. / Zoology and Entomology / unrestricted