No description available.

Identifying factors influencing kill rates or predation risk is crucial to relate predator effects on prey populations. In multi-predator landscapes, some predators may also perceive predation risk which may not only influence their distributions but also their effects on prey populations across landscapes. In the Upper Peninsula of Michigan, USA white-tailed deer (Odocoileus virginianus) exist in a multi-predator landscape which includes black bears (Ursus americanus), bobcats (Lynx rufus), coyotes (Canis latrans), and gray wolves (C. lupus). The objectives of this research were to examine spatial relationships among predators and their prey by identifying: 1) competition between wolves and coyotes, 2) factors influencing kill rates of predators, and 3) predator-specific predation risk for white-tailed deer fawns. We quantified the degree of temporal, dietary, and spatial overlap of wolves and coyotes at the population level to estimate the potential for interference competition and identify the mechanisms for how these sympatric canids coexist. We observed significant overlap across resource attributes yet the mechanisms through which wolves and coyotes coexist appear to be driven largely by how coyotes exploit differences in resource availability in heterogenous landscapes. We examined how heterogeneity in landscapes, search rate, and prey availability influence the time between kills for black bears, bobcats, coyotes, and wolves. Spatial heterogeneity in prey availability appeared to be a unifying extrinsic factor mediating time-to-kill across predators, potentially a consequence of more frequent reassessments of patch quality, which can reduce kill rates. We used white-tailed deer fawn predation sites to identify predator-specific predation risk with consideration for active predator occurrence, adult female white-tailed deer occurrence, linear features which may influence prey vulnerability, and habitat characteristics including horizontal cover and deer forage availability. Predator occurrence alone was a poor metric for predation risk. We identified differing landscapes of risk among ambush and cursorial foraging strategies which were more important for defining spatial variation in predation risk than predator density. These findings suggest that in a multi-predator landscape some predators may benefit from greater landscape heterogeneity due to availability of niche space, even though resource heterogeneity reduced predator efficacy and habitat complexity reduced predation risk for prey.

This thesis examines how Eastern grey squirrels, Sciurus carolinensis, modify their foraging and hoarding behaviour in relation to different risks, particularly those which involve a trade-off between securing food resources and avoiding a negative outcome with a competitor. While foraging for food to eat and hoard, squirrels must compete with conspecifics and heterospecifics for access to resources, and they must ensure the safety of their food hoards from onlookers or opportunistic pilferers. While engaging in these behaviours in the most efficient way, they must also avoid being predated upon. Five studies were conducted to further understanding of grey squirrel foraging, hoarding and pilferage behaviours, and how they are affected by different risk factors. The data in this thesis provide experimental evidence that grey squirrels respond directly to conspecific presence as a cue of pilferage risk and adjust their behaviour in ways that may help to reduce cache theft. The data also support the view that conspecific and heterospecific competitors pose risks to foraging and caching, with squirrels modifying their behaviour in ways that serve to avoid negative competitive interactions. Predation risk was found to be particularly disruptive to foraging behaviour, and it also had a seasonal effect upon pilferage rates of experimenter-made caches. A variety of strategies that squirrels might use to pilfer caches were investigated, however, the data did not provide a clear indication of pilferage strategy used by squirrels; they did not seem to use observational spatial memory, and they did not simply pilfer in profitable foraging locations. This thesis raises questions about the mechanisms grey squirrels use to assess pilferage risk and how they engage in pilferage in comparison to other caching species; the studies conducted illustrate different methods that future research could use to investigate food hoarding and pilfering behaviour in wild and captive squirrels.

I developed a spatially explicit individual-based model (IBM) to capture the dynamic behavioral interaction between a fierce predator (killer whale, Orcinus orca) and a clever prey (dusky dolphin, Lagenorhynchus obscurus), and to answer the ultimate question of costs vs. benefits for dusky dolphins when making anti-predator decisions. Specifically, I was interested in calculating time/distance budgets for dusky dolphins in the presence/absence of killer whales and the presence/absence of movement and behavioral rules, which presumably evolved in response to spatial and temporal variations in predation risk. Results reveal that dusky dolphins rest less, travel more and have reduced foraging time when killer whales are present. These effects are more pronounced with increased presence of killer whales. The model suggests that a strong reason favoring the adoption of short and long-term anti-predator mechanisms is increased survival resulting from decreased encounters with killer whales. Further, a mother with calf rests less and travels more when killer whales are present relative to a dolphin without calf. However, a mother with calf on average, flee shorter distances and have fewer encounters with killer whales than a dolphin without calf. Thus, despite ecological costs, it makes evolutionary sense for dusky dolphins to adopt anti-predator rules. Bioenergetic consequences for dusky dolphins with and without calf were estimated as total energetic costs and foraging calories lost due to low/high presence of killer whales. I calculated total energy costs as: Foraging costs (FC) Locomotor costs (LC) (Travel) or LC (Travel) LC (Flee) based on the absence, as well as low/high presence of killer whales. Foraging costs contributed significantly to total energetic costs estimated. Travel costs are minimal owing to proximity to deep waters. The total energy costs were not significantly higher from low or high presence of killer whales for mother with calf, but increases by about 90 kcal/day for a dusky without calf. However, I estimate foraging calories lost due to increased killer whale presence is almost 5 times more for mother with calf. Therefore, it might be important to consider indirect predation risk effects by social type in future studies on animal bioenergetics.

It is only recently that studies have explored the use of olfaction in birds. Birds are now known to use odour cues for navigation, and locating food. Odours produced by the birds themselves can also function in nest recognition and even mate choice. The odours of most birds stem from the preen wax produced by the uropygial or preen gland. The wax is comprised of a complex mixture of esters and volatiles, and is known to vary in some species with age, sex, season, or environmental conditions. Its function has been associated with feather maintenance, but it may also play a role in sexual selection and chemical communication. In this thesis, I used the preen gland and its preen wax to perform comparative studies on the evolution of odours between island birds and their continental relatives. I used the birds of the Oceania region as a model system, where most passerines originated from continental Australia but have colonised numerous surrounding islands such as New Zealand and New Caledonia. As islands generally lack mammalian predators, and have less parasites and less interspecific competition than continents, these differences in environmental conditions likely shaped functional differences in the preen gland and its products. I measured the size of the preen gland and collected preen wax from a variety of forest passerines in Australia, New Zealand and New Caledonia. I found that island birds have larger preen glands and therefore likely produce more preen wax than their continental relatives. I also found that the preen wax composition differed among species, with a shift to birds on islands producing disproportionately lighter and more volatile compounds. I suggest that selection favoured the gain of more volatile molecules in island birds as they were released from the constraint to camouflage their odours that is imposed by mammalian predators on continental areas. It is possible that this also allowed greater communication through olfactory channels in island birds, and such communication is enhanced through the use of more volatile compounds. To support this hypothesis I showed that the South Island robin (Petroica australis) was able to detect and react to the odour of a conspecific (odours produced by preen wax) in the absence of any visual cues. From a conservation perspective, increased volatility of the preen waxes of island birds might place them at increased risk from introduced mammalian predators that use olfaction to locate their prey. However, in both laboratory tests using Norway rats (Rattus norvegicus), a common exotic predator, and in field trials using rodent tracking tunnels, I found only limited evidence to suggest the odour of island birds places them at greater risk, and more experiments are needed to test this hypothesis. Finally, my findings of more conspicuous odours in island birds suggest new avenues of research for their conservation, including whether island species that seem especially prone to predation have preen waxes (and thus odours) that are also especially attractive to exotic mammalian predators. Conservation programmes to protect endangered island birds may even benefit from considering whether olfactory cues can be minimised as a method of reducing predation risk.

The effects of habitat complexity and predation risk on community assembly in small standing waters are reviewed. Both lethal and nonlethal predator effects are discussed. Emphasis is put on the role of omnivorous predators which do not fit into the standard food chain model. The review is complemented by a manuscript intended for publication in Freshwater Biology. It reports the results of a mesocosm experiment focusing on the effects of both lethal and nonlethal predation risk, induced by the invasive crayfish species Orconectes limosus, and habitat complexity on the abundance and biomass of macroinvertebrates in a naturally assembled community.

No description available.

Abstract Habitat selection decisions are crucial in determining fitness. Research indicates that individuals of many taxa are flexible in habitat selection and gather information prior to decision-making in order to control for environmental unpredictability. For time limited migrant birds, cues provide a quick and reliable information source with which to make habitat selection decisions. In this thesis I investigate habitat selection decisions, and their fitness consequences, of boreal passerines using heterospecifics or predators as cues. In support of the heterospecific attraction hypothesis, plots with augmented resident titmice densities attracted increased migrant densities. The predicted negative effects stemming from competition did not occur even at unnaturally high resident densities. This suggests that in the north it may always be beneficial for migrants to use residents as cues in habitat selection decisions. By manipulating habitat selection, I found that great tits (Parus major) had poorer reproductive success when forced to breed in close proximity to pied flycatcher (Ficedula hypoleuca) compared to when breeding alone. Flycatchers, in contrast, did slightly better when breeding close to tits. These results indirectly suggest that heterospecific attraction may not be a mutually positive species interaction. Indeed, flycatchers seem to parasitize the high quality microhabitat indicated by breeding great tits. I also tested if residents provide a reliable cue relative to predation risk. However, willow tit (P. montanus) nest location appeared random relative to avian predator nests. They do not appear to reliably indicate safe breeding habitats to later arriving migrants. In addition, closer proximity to breeding avian predators had a negative impact on willow tit reproductive output. Later arriving migrants may be in a better position to avoid avian predator nests during habitat selection. Pied flycatchers avoid settling in the immediate vicinity of sparrowhawk (Accipiter nisus) nests. However, nest box occupation, laying dates and initial reproductive investment (clutch size) showed a unimodal relationship with distance to sparrowhawk. A unimodal trend in these measures indicates there may be a trade-off between the costs (increased adult predation risk) and potential benefits (decreased nest predation risk) of settling in proximity to avian predator nests. Spatially predictable predation risk gradients that emanate from predator nests are termed a "predation risk landscape". Furthermore, flycatchers nesting closer to sparrowhawks produced fewer and smaller nestlings than those farther away. In addition, measures of maternal physiological stress (body condition and stress protein levels) had a negative linear relationship with distance to sparrowhawk nest. It appears that increased perceived predation risk near avian predator nests results in stressful and poor conditions for adult passerines, which results in lower reproductive output. This thesis highlights the importance of information gathering prior to making habitat selection decisions in order to optimise territory location relative to heterospecifics or predators. These decisions clearly impact individual fitness.

<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

The loss of large apex predators, and their subsequent reintroduction, has been identified as a substantial driver on the structure and function of ecological communities through behavioral mediated trophic cascades (BMTCs). The reintroduction of wolves (Canis lupus) to Yellowstone National Park (YNP) has served as foundational case study of BMTCs. In our system, it has been suggested that wolves have established a ‘landscape of fear’ in which the primary prey, elk (Cervus elaphus), now avoid risky places, which ultimately led to the recovery of the vegetation community. Although this case is frequently cited as a well-understood example of a landscape of fear, researchers never quantified whether elk avoided risky places, a critical component of the BMTC hypothesis. Thus, I employed numerous quantitative approaches to evaluate the role of wolves and cougars on elk habitat selection in northern Yellowstone. The results from this work suggest that the daily activity schedule of wolves provide a temporally predictable period of risk that allows elk to use risky places during safe times. As such, diel predator activity flattened (i.e., made less risky) the landscape of fear for 16 hours per day, 7 days a week, which permitted elk to forage on deciduous woody plants despite the presence of wolves. Thus, suggests that any trophic cascade in northern Yellowstone is likely driven by the consumptive effects of wolves on elk. In addition, my results suggest that daily activity patterns are an important component of predation risk, and as such, provide a predictable avenue for elk to avoid predators despite residing in an environment spatially saturated with wolves and cougars. Thus, the ability of elk to avoid predators through fine-scale spatial decisions provides support for my findings that the current spatial distribution of prey is largely driven by the consumptive effects of predators on the prey population, rather than a landscape of fear. In combination, these results suggest that the landscape of fear, and more generally, fear effects, may be of less relevance to conservation and management than direct killing within free-living, large landscapes.