Published by Informa UK Limited, trading as Taylor & Francis Group. We developed an agent-based computer model of an ecosystem to predict interactions of competition and predation. In our simulations of the model, the effects of the ‘Gause law’ emerged as the results of population fluctuations and a large number of stochastic events. Small biases in life history parameters produced strong effects through the interactions of positive feedback with the population fluctuations. In a low-production environment, the smaller and faster consumer outcompetes the larger and slower one, but in a high production environment the larger and slower consumer survives. Predation hastens the extinction of one of the consumers, but niche partitioning of the consumers increases both the coexistence of consumers and the number of predators. Predators with medium efficiency are able to coexist in the system longer and in larger numbers. Besides the ecological insights this model provides, we conclude that agent-based simulations are very effective tools to explore the interactions between predation and competition interactions.

Two congeneric damselfly species, Enallagma traviatum and E. aspersum, dominate the littoral macroinvertebrates of Bays Mountain Lake and of the adjacent fish-free Ecology Pond, respectively (northeastern Tennessee, USA). Extending previous experimental studies, we test seven hypotheses concerning the role of fish (bluegill sunfish, Lepomis macrochirus) and larvaldragonfly (Anax junius) predation, competitive effects on damselflies, and the interaction between competition and predation, in determining invertebrate dominance in these communities. Three types of experiments were conducted: an enclosure experiment within Ecology Pond, an outdoor replicated tub experiment, and a laboratory behavior experiment. The in-situ enclosure experiment showed that E. traviatum larvae were more susceptible to Anax predation than were E. aspersum larvae; a tendency toward greater vulnerability to fish of E. aspersum compared with E. traviatum was not statistically significant. The outdoor tub experiment confirmed both of these trends with statistically significant results. In the tubs, both predators inhibited feeding of both zygopterans (as indicated by reduced fecal mass), particularly for E. aspersum in the presence of fish. This effect appears to have been primarily indirect, mediated through exploitation of the zooplankton. We also detected competitive effects of E. traviatum on E. aspersum: E. traviatum reduced the emergence and increased the exposure above the substrate of E. aspersum. In the absence of predators, E. traviatum inhibited feeding of E. aspersum via interference. In the laboratory behavior experiment, predators inhibited crawling by E. aspersum. E. aspersum was more exposed than was E. traviatum; it swam and crawled more than did E. traviatum, considerably increasing these movements at night. Over all, E. traviatum consistently appeared to be the more cryptic of the two species, and E. aspersum appeared to be much more active. Our results suggest an explanation for the clear difference in structure between communities like Bays Mountain Lake and Ecology Pond: predaceous fish eliminate large invertebrate predators and shift the community toward cryptic forms at relatively low densities, reflecting the effects of both predation and exploitation competition. In the absence of fish, large invertebrate predators are less able to deplete littoral invertebrates but may favor the more active forms, perhaps because these are better able to avoid invertebrate predators.

This thesis outlines research conducted as part of a collaborative project between Virginia Tech and Plant and Food Research New Zealand (PFRNZ) to introduce Heringia calcarata (Loew) (Diptera: Syrphidae) to New Zealand (NZ) for biological control of woolly apple aphid (WAA), Eriosoma lanigerum (Hausmann) (Hemiptera: Aphididae). Ultimately, the introduction of H. calcarata to New Zealand will be contingent upon satisfying regulatory requirements and concerns, including documentation that it will not have an adverse effect on the existing biological control of WAA by Aphelinus mali (Haldeman) (Hymenoptera: Aphelinidae). As well, it will be critical to develop methods for sustained rearing of H. calcarata in captivity. Basic and applied studies were conducted toward providing essential information for advancing this project. Apple shoot sections with a WAA colony that did or did not contain mummified aphids parasitized by A. mali were deployed in pairs at the base of apple trees. There was no significant difference in the mean number of H. calcarata eggs deposited between shoots with parasitized (1.5 ± 0.34 SE) and non-parasitized colonies (1.75 ± 0.42 SE), although female H. calcarata laid eggs less frequently on colonies with a high percentage parasitization. In choice-test feeding studies, larvae were offered non-parasitized aphids in combination with aphids in an early stage of parasitization or mummified aphids. Larvae consumed significantly fewer aphids in an early stage of parasitization (10.8 ± 0.48 SE) than non-parasitized aphids (13.4 ± 0.42 SE) and very few mummies (0.4 ± 0.14 SE) compared with non-parasitized aphids (14.2 ± 0.4 SE). In no-choice feeding trials, larvae consumed significantly more non-parasitized aphids (25.3 ± 1.93 SE) than aphids in an early stage of parasitization (19.7 ± 1.85 SE) or mummified aphids (2.2 ± 0.71 SE) and significantly fewer mummified aphids were consumed than early parasitized aphids. WAA colonies in situ on the branches of potted apple trees were exposed to H. calcarata, A. mali, or both. Exposure to H. calcarata larvae independently and in combination with A. mali was shown to have a significant effect on the number of WAA compared with control colonies, and H. calcarata larvae did not affect the number of mummified aphids produced within colonies. Heringia calcarata eggs were collected by deploying excised apple shoot sections containing at least one WAA colony at the base of apple trees for 8-12 h. One or more eggs were laid on 29% of shoots (n = 233 shoots). On shoots with eggs, 2.4 ± 0.21 SE eggs per shoot were recorded. In 2012, four shipments of H. calcarata eggs and larvae (total of 178) were sent from Virginia to a quarantine containment facility in NZ. This demonstrated that juvenile H. calcarata could be successfully transported internationally. In total, 124 adult flies were generated in NZ, representing 69.9% of the number of eggs and larvae recovered upon delivery to quarantine. Field-collected gravid female H. calcarata oviposited on WAA colonies under captive conditions: 63% in 2011 (n = 8) and 80% in 2012 (n = 15). In 2012, 98% of the eggs deposited hatched. Virgin females reared from eggs in the laboratory developed mature oocytes regardless of access to pollen. The findings of this research offer valuable insights into the biology and ecology of H. calcarata that are directly relevant to the project goals and that will help guide the development of H. calcarata as a classical biological control agent for WAA in NZ. / Master of Science in Life Sciences

Diet of cougars (Felis concolor) was studied from December 1978 to August 1981, on a 4500 km2 study area near Escalante, Utah. Prey eaten was determined from analysis of 112 animals consumed as prey, and from 239 cougar scats. Mule deer (Odocoileus hemionus) were the major prey item, comprising 81% of biomass consumed. Lagomorphs, large rodents, and smaller predators were also important components. Cattle comprised Motion-sensitive radio-transmitters were placed on 15 cougars, from 3 months to 7-9 years of age. Three parameters of the radio signal were used to determine activity levels during 6843 1-minute sampling periods: number of changes in pulse rate, predominant pulse mode, and signal integrity, based on 308 minutes of "known" acti vity. Cougars showed distinct crepuscular (sunrise, sunset ± 2 hrs) activity peaks (P Estimates of energetic costs of basal metabolism, and of activity, growth, and reproduction were used in a predictive model of energy cost of free-existence. Information on dietary composition, live weight and energy content of prey animals, and assimilation efficiencies were used to provide estimates of the frequency at which deer were killed (deer/day) and consumed (kg/day). Single adults were estimated to kill 1 deer per 8-16 days. Females with 3 large cubs would kill 1 deer as often as every 2-3 days. A known population of 8 adult cougars was predicted to consume 417 deer per year.

Woodpeckers create nesting cavities for other birds and animals in forests. This creates dynamic interactions between both woodpeckers and these other animals. Using video cameras, we documented direct behavioral interactions between nesting woodpeckers and other animals in the Eastern Washington Cascades during the 2015 and 2016 breeding seasons. Additionally, we offered 937 students in a General Biology laboratory course to participate in this original research opportunity and described and the impact the experience had on the participants as well as the researchers. In 2015, Western Blubebirds took over two active Black-backed Woodpecker nests by physically attacking the woodpeckers. In 2016, almost half of the woodpecker nests were reused by other animals, with Western Bluebirds being are most common SCU. We found that some nests we reused within minutes to hours of vacancy. However, we were not able to significantly predict nest reuse or the presence of other animals at the nest. Parent woodpeckers towards avian cavity nesters when compared to rodent, predators, and other woodpeckers. Our fine-scale analysis provides a new window into behavioral interactions at woodpecker nests and same-season nest reuse, but it is limited by its scope. Thus, we suggest for larger-scale video studies examining behavioral interactions around the nest. About 15% of students in the course participated in our research, and we found that students accurately recorded data approximately 90% of the time. Most students came away from the experience with a more positive attitude towards undergraduate research and were able to restate the main research question. However, many students had difficulty understanding their role as a data collector. We suggest making the experience mandatory to include all students and placing a greater emphasis on the process of science.

A landscape perspective is critically important for understanding community structure, particularly in systems dominated by migratory fauna. I aimed to understand how the structure of riverscapes in Puerto Rico mediates potential anthropogenic impacts, predator-prey interactions, and the migratory behavior of a diadromous species. I surveyed fishes and shrimps at sites throughout two watersheds, designed transplant experiments that investigated the role of natural barriers on predator-prey interactions, and developed models of shrimp migration specific to a particular river network. I did not detect an effect of anthropogenic changes to the landscape on fish and shrimp species distributions in two watersheds that drain the Luquillo Experimental Forest. These communities were primarily affected by the position of natural barriers: predatory fish distributions were limited by waterfalls and most shrimp species were found upstream from fish barriers. Thus, steep terrain mediated predator-prey interactions between fishes and shrimps, with one shrimp (Atya lanipes) likely avoiding predation by migrating above fish barriers. Lab and field experiments provided the first mechanistic evidence for landscape-level predator-avoidance behavior by A. lanipes. Both postlarval and adult shrimp avoided the scent of three predatory fish species in a y-maze fluvarium. In natural streams above fish barriers, adult A. lanipes did not respond to the addition of fish scent, but adult abundances did decline when fish were added to in-stream cages. To integrate our ideas about how shrimp behaviors scale up to observed adult A. lanipes distributions across the landscape, we developed a set of nested models specific to a particular river network. The best models parameterized branch choice at nodes within the river network to be heavily weighted toward particular mid-elevation tributaries above fish barriers. Our models indicated that distance traveled above and below fish barriers had little effect on adult distributions. Because the number of migrants decreases with distance upstream, the latter result was likely an artifact of the model. In montane river systems with migratory fauna, scientists would benefit by creatively designing new experiments and models that incorporate river network structure, as this is the template upon which all processes occur.

This study examined the activity patterns and social relation ships between individuals in a large herd of domestic sheep (Ovis aries) in an effort to determine if behavioral characteristics predisposed certain individuals to coyote (Canis latrans) predation. The research was conducted on the Cook Ranch near Florence, Montana, from March through September of 1975. Data were collected from a herd of 627 ewes and 1082 lambs, each individually identifiable. A random sample of 44 ewes and their 75 lambs were intensively studied over a 16-wk period to establish activity budgets and the relationships between sheep activity and vulnerability to coyote predation. The feasibility of creating target lambs in a free-ranging environment by altering movement, appearance, or social relationships with other herd members was examined in six experiments. During the study, 24 ewes and 47 lambs died from natural causes. Predators killed 7 ewes and 73 lambs. Coyotes selected single lambs, lambs displaying aberrant movement, and lambs whose dams had restricted mobility. Reduced mobility appeared to increase the probability of a lamb being on the periphery of the bedground and this in turn increased the probability of it being encountered by an attacking coyote. Grazing and resting periods of lambs were highly correlated with those of the ewes. Lambs were not within sight of their dams 30 percent of the time and showed a greater tendency to be absent during rest periods than during other activity periods. Yearling ewes investigated less and won less encounters. Brocatelface ewes grazed less and slept more than whiteface ewes. The oldest ewes interacted with other members of the herd less than younger ewes. Although significant differences in behavior existed between different age and genotype cl asses, the behavior of ewes whose lambs were killed by coyotes was remarkably similar to all other ewes. Male lambs were consistently absent from their dams less than female lambs. Single lambs also showed a tendency to be with the ewe more than twins. Single lambs spent more time nursing than twins during the first half of the study but not the last half. Siblings that were killed by coyotes consistently lay down less than their litter mates. Although differences existed in the behavioral signature of various classes of lambs, no relationships between these differences and vulnerability to predation was apparent. / coyote predation on domestic sheep seems to be related more to the chance of a lamb being on the periphery of the bedground than to differences in behavioral signatures. No pairwise associations were found between ewes. Yearling ewes associated with other yearling ewes and were peripheral individuals both during the day and on the bedground. Brocatelface ewes were peripheral during the day, but not on the bedground. Statistically, yearling ewes were leaders, but leadership in a welfare sense did not exist. The general lack of file formations and the rolling pattern of files when files were formed suggests that leadership in domestic sheep is not a robust phenomenon. The influence of dominance on positional behavior observed during the study was reflected in strange-lamb experiments. Lambs which were unfamiliar with the herd were subordinate and were forced into peripheral positions where they were more vulnerable to predation for up to 3 weeks. ' Lambs with a high susceptibility to coyote predation can be created by simply raising lambs in isolation and later releasing them into a herd.

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