The current explanation for the absence, or low abundance, of filter-feeding invertebrates from some rocky shores is that because of local variation in nearshore oceanographic conditions, larvae do not arrive in sufficient numbers to establish populations. One putative consequence of this is that macroalgae are able to establish dominance in areas where filter-feeders (especially mussels) do not recruit well. While macroalgae have been transplanted to mussel-dominated shores with varying success, the survival, growth and reproduction of transplanted mussels has not been tested in areas dominated by macroalgae. To determine specifically what tips the balance between shores dominated by filter-feeding invertebrates and those dominated by macroalgae, I monitored the recruitment of intertidal mussels at four sites on the Kaikoura coast: two with mussels present and two algal-dominated. No significant differences in mussel recruitment rates were found between habitats and recruitment intensity at all sites was found to be very low. Recruitment limitation is not the reason for the absence of mussels from algal dominated shores but some form of limitation does occur to reduce the number of arriving mussels. Predation effects were examined by transplanting juvenile mussels into caged, uncaged and control treatments. No significant differences in predation rates between habitats were found and transplanted mussels in open cages at all sites were removed within 3 days. Mobile fish predators appeared to be the most likely cause of this intense predation. Growth of transplanted mussels into algal and mussel habitats was found to be significantly different. Mussels grew faster in mussel dominated habitats and after 6 months in algal dominated habitats, all mussels had died. The outcome of these experiments indicates that there is a close relationship between recruitment, survival and growth which tips the balance and allows the existence of mussel beds along the Kaikoura coastline.

Cyrba algerina is a salticid (Salticidae) spider that lives on the undersides of stones. Two populations were studied, Sintra and Algarve (Portugal), and shown to have similar phenology but different dominant prey. Life cycle in the laboratory was similar for the two populations, but Sintra matured at larger size than Algarve individuals, with these differences potentially having a genetic basis. Sintra individuals used prey-specific prey-capture behaviour against allopatric (Oecobius amboseli) and sympatric (O. machadoi, Trachyzelotes bardiae) spider and insect (bristletails) species. In contrast, Algarve C. algerina only adopted specialised capture behaviour against bristletails. Sintra, but not Algarve, individuals responded to the odour of O. machadoi and T. bardiae, and showed preference for T. bardiae over O. machadoi. Interpopulation variation in the use of specific prey-capture behaviour and in sensitivity to odour cues from prey is directly related to the prey available to individuals from each population, suggesting local adaptation to local prey. Preference for oecobiids seems to be controlled by an experiencetriggered developmental switch. The optics and histology of C. algerina’s principal eye suggest that living in a microhabitat with dim ambient light has favoured sensitivity at the expense of spatial acuity. Short focal length, reduced power of the eye’s diverging lens, and wide, contiguous rhabdomeres, seem to minimise the visual constraints imposed by the low light levels in C. algerina’s microhabitat. While relying solely on vision, C. algerina can detect, identify and capture prey in dim-light conditions under which other salticids perform poorly. C. algerina’s behaviour suggest use of temporal summation to improve its visual performance in dim light.

Ecological communities along gradients of environmental stress are thought to be structured by trade-offs between resisting biotic interactions in physically benign habitats and successfully exploiting physically stressful habitats. However, these trade-offs are likely to be affected by the predictability of abiotic stressors, and variation in the strength of biotic interactions. I investigated community assembly and food web interactions in ponds across an unpredictable gradient of water inundation (pond permanence) in Canterbury, New Zealand. Pond community composition and species richness were strongly influenced by pond permanence. However, species in temporary ponds were a nested subset of generalists that were also found in permanent ponds, rather than a unique assemblage of temporary pond specialists. Subsequent experiments indicated predator impact decreased with pond permanence, partially due to the foraging suppression of predatory invertebrates in permanent ponds by fish. Weak predation in permanent ponds combined with unpredictable drying regimes likely selected for generalist traits, and resulted in community assembly being driven by a gradient of drying stress rather than trade-offs between biotic interactions and drying. Furthermore, predator impact increased over time in temporary ponds. In predictable snow-melt ponds in the Colorado Rocky Mountains, seasonal windows of weak predation were exploited by vulnerable species, leading to increased diversity within habitats. However in unpredictable systems like Canterbury, temporal increases in predation risk that depend on drying history are likely to increase variability in the spatial arrangement of suitable habitats for particular species. This should further favour the evolution of generalist traits and reduce the importance of trade-offs between predation and drying in the assembly of communities. Considering the predictability of disturbance regimes and the spatial and temporal variation in biotic interactions will greatly enhance understanding and management of communities in heterogeneous landscapes.

Tests of optimal foraging theory have shown that many predators are selective about which prey and which patches should be utilized. I hypothesize that prey species "exploit" this choosiness by evolving characteristics that cause predators to choose alternate prey. Specifically, prey should evolve traits that increase the probability of predator death, decrease the per prey or per patch nutritional intake, increase processing time, and advertise (or mimic advertisements of) undesirable traits. Predator choosiness allows prey to divert the predator instead of defeating it. The evolution of a long-term, prudent foraging strategy requires that three conditions be met: (1) The forager must use resources from a discrete subpopulation; (2) use of that subpopulation must be relatively exclusive; (3) the resource population must respond in such a way that a long-term strategy provides an economic advantage. For the horned lizard-ant system, conditions (1) and (2) were tested by tagging lizards with transmitters or radioactive tags. Horned lizards occupy home ranges much smaller than would be expected if they moved at random and home range overlap was less than expected by random placement of home ranges, thus conditions (1) and (2) were not rejected. Most techniques of home range study do not distinguish random from nonrandom movement. Condition (3) was tested by subjecting ant colonies to various levels of artificial predation. In none of five experiments was the result obtained that an increased harvest intensity led to a decrease in long-term yield; condition (3) is tentatively rejected. Ant colonies shut down in response to predation; this puts a ceiling on their losses. Short-term foraging models were tested for horned lizards foraging at ant colonies. A prediction of the marginal value theorem was not rejected: Horned lizards tended to leave colonies when their instantaneous rate of harvest at that colony had fallen to their average rate of harvest for the day. Another short-term prediction, however, was rejected: Lizards did not stay longer at the "better" of two colonies. A more liberal version of the same prediction was not rejected. Apparently, horned lizards forage adaptively but not optimally.

Communities of granivorous desert rodents are structured by habitat selection and may be influenced by either predatory risk or resources. To examine these hypotheses, I manipulated illumination using lanterns, parachute canopies, or natural moonlight and resources using seeds. Foraging behavior is risk-sensitive; increased illumination reduces foraging in open areas while adding shadows to open areas using parachutes increases foraging there. Foraging behavior is also affected by resource enrichments. Differences among species in habitat selection were determined by specific abilities to detect and avoid predators. The least vulnerable species, Dipodomys deserti, foraged heavily in the open and was largely unaffected by treatments; other species of kangaroo rats and kangaroo mice also prefer the open, but responded to both risk and resource manipulations; highly vulnerable Peromyscus maniculatus was always restricted to bushes even under the most favorable circumstances; Perognathus longimembris was restricted to bushes in the absence of P. maniculatus in 1980 and was displaced from preferred microhabitats by the presence of kangaroo rats in 1981. A correlation between auditory bullar volume and use of open habitat by the various species in this community suggests that predatory risk provides an axis along which habitat segregation occurs. Predation can shape community structure by influencing foraging decisions of individuals. Desert rodents from North America and the Middle East have converged morphologically and perhaps in behavior and in community structure. Using desert rodent communities in the Great Basin Desert of U.S.A. and in the Negev Desert of Israel, I manipulated predatory risk in both communities and noted that foraging activity declines with increased predatory risk. Additional evidence suggests that predation also affects habitat selection behavior in both communities. Furthermore, differences in habitat utilization among species which promotes coexistence are related to morphological anti-predator specialization of the species. Predation appears to have shaped behavior and contributed to community structure in similar ways in both communities.

Positive frequency-dependent predation (FDP) has been proposed as a species coexistence mechanism and theoretical models have shown how it may function. In positive FDP a rare species receives a temporary reprieve from predation pressure allowing an increase to its population growth rate and a chance for it to recover from rarity. This study tests for frequency-dependent foraging by granivorous desert rodents on the seeds of three species of winter annual plants that grow in the Sonoran Desert. While the preference for one species is much higher than the other two, preferences for each species are higher when common than when rare showing an asymmetric form of positive FDP. This study is the first empirical test for positive FDP on winter annual plants and by granivorous desert rodents and one of few to use more than two prey species, native prey species, or asymmetrically preferred prey species.

This research is designed to test how sublethal exposure to copper affects tadpole predator-escape behavior and how quickly tadpoles recover. After exposure, tadpoles were separated. Escape behavior was recorded for two-thirds of exposed tadpoles while one-third of the exposed population was measured weekly to determine growth and recovery. Control tadpoles were consumed within 15 minutes whereas those exposed to higher concentrations were consumed at a slower rate, which does not support the hypotheses. Although the rate of predation was lower, tadpoles exposed to higher Cu concentrations were on average, 1.47 cm in total body length. Those exposed to 0.93 mg/L averaged 0.86 cm. After being placed into clean water, treatment tadpoles recovered after 20 days.

Maintaining desired numbers of wildlife species requires an understanding of species-specific population dynamics. For ungulate species such as the white-tailed deer (Odocoileus virginianus), understanding the neonatal survival rate of a population and factors that influence that survival rate, may be two of the most important factors to successful deer management. We examined neonatal survival in an eastern Kentucky population of deer living in relatively low densities (/ km2), with adequate habitat and supposedly poor population growth. Neonates (102) were captured in the summer birth periods of 2014 - 2016 and radio-monitored until the beginning of the fall archery deer season. We found moderate-to-low survival estimates to four months of 43% (95% CI: 29 – 57%) that are consistent with many areas in the Midwest and southeastern United States. Predation, including suspected predation events, from bobcats (Lynx rufus) and coyotes (Canis latrans) accounted for 80% of all neonate mortalities. A thorough examination of the survival and mortality in the neonate component of this population is discussed herein.

<p>The ultimate goal of wildlife recovery is abundance growth of a species, though it must also involve the reestablishment of the species’ ecological role within ecosystems frequently modified by humans. Reestablishment and subsequent recovery may depend on the species’ degree of adaptive behavior as well as the duration of their functional absence and the extent of ecosystem alteration. In cases of long extirpations or extensive alteration, successful reestablishment may entail adjusting foraging behavior, targeting new prey species, and encountering unfamiliar predatory or competitive regimes. Recovering species must also increasingly tolerate heightened anthropogenic presence, particularly within densely inhabited coastal zones. In recent decades, gray seals (Halichoerus grypus) recovered from exploitation, depletion, and partial extirpation in the Northwest Atlantic. On Cape Cod, MA, USA, gray seals have reestablished growing breeding colonies and seasonally interact with migratory white sharks (Carcarodon carcharias). Though well-studied in portions of their range due to concerns over piscivorous impacts on valuable groundfish, there are broad knowledge gaps regarding their ecological role to US marine ecosystems. Furthermore, there are few studies that explicitly analyze gray seal behavior under direct risk of documented shark predation. </p><p> In this dissertation, I apply a behavioral and movement ecology approach to telemetry data to understand gray seal abundance and activity patterns along the coast of Cape Cod. This coastal focus complements extensive research documenting and describing offshore movement and foraging behavior and allows me to address questions about movement decisions and risk allocation. Using beach counts of seals visible in satellite imagery, I estimate the total regional abundance of gray seals using correction factors from haul out behavior and demonstrate a sizeable prey base of gray seals locally. Analyzing intra-annual space use patterns, I document small, concentrated home ranges utilizing nearshore habitats that rapidly expand with shifting activity budgets to target disperse offshore habitats following seasonal declines in white sharks. During the season of dense shark presence, seals conducted abbreviated nocturnal foraging trips structured temporally around divergent use of crepuscular periods. The timing of coastal behavior with different levels of twilight indicate risk allocation patterns with diel cycles of empirical white shark activity. The emergence of risk allocation to explain unique behavioral and spatial patterns observed in these gray seals points to the importance of the restored predator-prey dynamic in gray seal behavior along Cape Cod.</p> / Dissertation

Native to Asia, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) is an invasive non-native ladybird in Europe and North America, where it was widely introduced as a biological control agent of aphids and coccids. There were three main objectives of this study: firstly, to investigate the spread and distribution of H. axyridis in Europe from the start of the invasion process; secondly, to study its ecology in Great Britain; and thirdly, to examine its effects on native ladybirds in Britain. In Europe, collaborations with a network of scientists allowed the collation of H. axyridis occurrence data from across the continent. In Great Britain, a web-based public survey (www.harlequin-survey.org) was used, leading to the receipt of over 10,000 verified records of H. axyridis between 2004 and 2008. National land cover data enabled the habitats used by H. axyridis to be identified across Great Britain. These datasets were analysed in order to study the spread and ecology of H. axyridis in Europe and Britain. Fieldwork over a three year period (2006 to 2008) was carried out to examine changes in ladybird species assemblages during the invasion phase of H. axyridis in eastern England. Laboratory work was conducted to detect intraguild predation by H. axyridis, through PCR analyses of gut contents of field-collected ladybirds. In Europe, H. axyridis has spread since 2001 at the rate of approximately 200km yr-1. It has become established in at least 23 European countries. The established range extends from Norway in the north to southern France in the south, and from Ukraine in the east to Great Britain in the west. In the first five years of establishment H. axyridis spread north through Britain at the rate of 105km yr-1 and west at the rate of 145km yr-1. Evidence of the production of two generations per year was found, giving H. axyridis an advantage over most native ladybirds in Britain. Although H. axyridis was very common in urban habitats, it increasingly used semi-natural habitats. In addition, whilst the species was most common on deciduous trees, it was increasingly found on herbaceous plants. Aceraceae, Rosaceae and Malvaceae were the dominant plant families used by H. axyridis, especially for breeding. In eastern England H. axyridis increased from 0.1% to 40% of total ladybirds in three years, whilst native aphidophagous ladybirds declined from 84% to 41% of total ladybirds in the same period. Three species in particular experienced declines: Adalia 2-punctata, Coccinella 7-punctata and Propylea 14-punctata. Harmonia axyridis was the most abundant species by the end of the study. Detection of intraguild predation by one coccinellid on another, in the field in Europe, was shown for the first time using PCR techniques: A. 2-punctata DNA was detected in the gut of one of 112 field-collected H. axyridis. Harmonia axyridis has spread very quickly since 2001 and has become one of the most widely distributed coccinellids in Europe. Populations of native aphidophagous ladybirds were negatively affected by the arrival of H. axyridis, partly through intraguild predation.