Biological processes like species interactions and patterns such as abundance and distribution observed in nature can vary depending on the scale at which the subject of interest is evaluated. Knowing that there is no single natural scale at which systems should be studied, in this thesis, I conducted a series of basic and applied ecological approaches in order to examine the phenomena that can occur at different scales of space, time, and ecological organization. Species abundances can vary over large spatial and temporal scales. By studying the habitat use of an abundant species, which uses a wide range of habitats, insights can be gained into how seascape-scales might influence population-level patterns. Similarly, temporal scales might affect the dynamics of species that have complex life cycles where migration is involved. Therefore, in the first study I used an eight-year dataset to conduct a population-level study at broader time- and seascape- scales of an abundant species in Tampa Bay, Florida. The goal of this study was to provide the first in-depth study on the habitat use of Pinfish on the eastern Gulf of Mexico and to provide insights on how seascape-scales can influence their abundance and distribution. Predator-prey interactions can be influenced by habitat at different spatial scales. In seagrass systems, blade density can provide prey refugia at local scales, which are further embedded within the seascape-scale effect of turbidity. In the second study, I used a combination of in situ field experiments and laboratory-controlled experiments to examine and separate the effects of habitat across these local and seascape scales on the relative predation rates of tethered Pinfish (Lagodon rhomboids). The broad-scale analyses indicated that population-level differences, such as abundance patterns and distribution can be influenced by temporal and spatial scales. Field- studies showed that habitat can influence ecological interactions at local- and seascape- scales. Overall, this research demonstrates the importance of using multiple spatial and temporal scale approaches when studying ecology, especially of those organisms that move over large distances and have complex life histories.

<p>This thesis deals with the evolution of individuals within a species adapted to utilize specific resources, i.e. resource polymorphism. Although a well-known phenomenon, the understanding of the mechanisms behind is not complete. Considering the ruling theories, resource polymorphism is suggested to depend on severe competition for resources, the presence of open niches to be occupied leading to a reduction in competition, and disruptive selection where generalist are out-competed due trade-offs in foraging efficiency for different prey. In order to study resource polymorphism, I have used fish as the animal group in focus and the methods I have used range over laboratory experiments, field experiments, literature surveys and theoretical modelling.</p><p>In my work, I have showed that different resource use induces different body shapes and that the rate of change is dependent of the encounter rate of different resources. The induced body changes partly led to increased foraging efficiency but surprisingly I did not find any trade-offs due to specialization. However, when studying predation risk in relation to resource polymorphism, my studies point towards that resource use and predation risk may act as balancing factors in such a way that disruptive selection can take place.</p><p>My work also shows that population feedbacks have to be explored when considering the evolution of resource polymorphism. In pond and field experiments, I found that changes in resource densities affected the actual resource use despite previous adaptations to certain resources. By performing a literature survey, I found that cannibalism indirectly by its effect on population dynamics seems to facilitate the evolution of resource polymorphism. Modelling a size-structured population, I found that resource dynamics were stabilized, and the relative availability of different resources was levelled out due to cannibalism.</p><p>Taken together, my studies strongly suggest that to understand the development of resource polymorphism in consumer populations, future studies have to include the effect of a dynamic environment both with respect to resources and predators.</p>

A ubiquitous problem for all foragers is the trade-off between acquiring food energy while simultaneously avoiding the risk of predation. In central montane Alberta I modelled how ungulate forage changes with succession within cutblocks and the implications for forage availability to ungulates under current harvest regimes. Because cutblocks are discrete patches in space, I developed a dynamic state variable model for an ungulate to explore under what conditions an individual forager could (1) behaviourally avoid predation within a patch through inactivity, (2) overcome patch isolation when confronted with predation during transit between patches, and (3) alter patch use across a home range to optimize fitness. The model includes the requirement to process forage into energy through rumination behaviour that constrains foraging, and compares outcomes under a time-minimizing (sigmoid) and energy maximizing (linear) fitness functions. When an ungulate is in high energetic state, inactivity provides an effective behavioural refuge, or animals prioritize safety over energy gain, individuals avoid predation within patches reducing the need to move between patches. When energy acquisition is prioritized, individuals are at a low energetic state, or within patch anti-predator behaviours are ineffective, individuals move among patches to avoid predators in space, and configuration of the patches influences fitness. When model results were qualitatively compared to activity patterns and cutblock use of female, GPS-collared elk appear to follow a time minimizing strategy in their patch use across the home range and with their activity within riskier patches. I discuss the implications of these findings for the management of elk and cutblocks in west central Alberta.

This thesis deals with the evolution of individuals within a species adapted to utilize specific resources, i.e. resource polymorphism. Although a well-known phenomenon, the understanding of the mechanisms behind is not complete. Considering the ruling theories, resource polymorphism is suggested to depend on severe competition for resources, the presence of open niches to be occupied leading to a reduction in competition, and disruptive selection where generalist are out-competed due trade-offs in foraging efficiency for different prey. In order to study resource polymorphism, I have used fish as the animal group in focus and the methods I have used range over laboratory experiments, field experiments, literature surveys and theoretical modelling. In my work, I have showed that different resource use induces different body shapes and that the rate of change is dependent of the encounter rate of different resources. The induced body changes partly led to increased foraging efficiency but surprisingly I did not find any trade-offs due to specialization. However, when studying predation risk in relation to resource polymorphism, my studies point towards that resource use and predation risk may act as balancing factors in such a way that disruptive selection can take place. My work also shows that population feedbacks have to be explored when considering the evolution of resource polymorphism. In pond and field experiments, I found that changes in resource densities affected the actual resource use despite previous adaptations to certain resources. By performing a literature survey, I found that cannibalism indirectly by its effect on population dynamics seems to facilitate the evolution of resource polymorphism. Modelling a size-structured population, I found that resource dynamics were stabilized, and the relative availability of different resources was levelled out due to cannibalism. Taken together, my studies strongly suggest that to understand the development of resource polymorphism in consumer populations, future studies have to include the effect of a dynamic environment both with respect to resources and predators.

Perceived predation risk alters animals’ behavior. This shift in behavior often comes at the cost of attaining resources. Generally, African elephants (Loxodonta africana) experience little predation pressure; however, the risk of predation by lions (Panthera leo) increases other prey species are less abundant. In elephant herds, related females and their offspring travel together in family groups, led by the eldest female. Response to predation pressure was examined by playing lion calls to the population of 437 elephants at the Main Camp Section of Addo Elephant National Park (AENP) in South Africa. Unfamiliar lion calls from a single male and two males, static, and running water were played from a remote speaker to elephants at waterholes. These trials were recorded by video. Behaviors of elephants were then extracted from video into focal observations of thirty second segments before, during and after a sound was played. I analyzed these data using parametric t-tests and non-parametric randomization tests. When no sound was played, elephants did not alter their behavior. Water elicited low levels of distress behaviors. Elephants behaved in a threatened or annoyed manner toward static. Elephants changed their behavior more in response to lion calls than to the controls, namely by decreasing drinking and increasing walking and distress behaviors. I also examined how individuals differed in their responses to the lion calls based on a number of demographic factors. Adult and subadult females performed more social behaviors after lion calls when the matriarch was absent than when she was present. Furthermore, when group size was larger and more calves were present, females decreased drinking and increased time exhibiting distress behaviors. Based on this and other studies it can be concluded that elephants of different demographics perceived similar levels of elevated risk when hearing lion calls. Landscape of fear models are useful for assessing habitat use by prey species in response to real and perceived predation risk. The present study corroborates findings from a study in East Africa that elephants perceive threat from lions based on calls alone and appear to distinguish levels of threat by the number of lions calling.

Previous studies have shown that ice cover has many positive effects on brown trout (Salmo trutta), including protection from endothermic predators. I tested whether it is the cover provided by the ice itself or the reduction in light that causes behavioral changes in juvenile brown trout. To distinguish between these two effects, behavioural observations were made with and without ice at the same light intensity (500 lux). An additional ice-free, high light (3000 lux) treatment was included to be able to measure brown trout’s response to light reduction. A mink model was used to simulate predation risk to be able to measure the fish’s anti-predator response under these three conditions. I found a significant treatment effect on body and eye coloruration. For eye colouration, I found that fish under ice had a paler eye colouration than fish that experienced high light, which in turn were paler than fish subjected to low light. For body colouration, fish under ice had paler body colouration than fish from the two ice-free treatments, which did not differ from each other. There was no effect of treatment on ventilation rate, time to initiate foraging, time to initiate activity or swimming activity, although both foraging and activity were lowest and swimming activity highest under ice. The changes in body and eye colouration indicate that trout are less stressed under ice, presumably because they perceive ice as a barrier against terrestrial predators. These results suggest that the ongoing climate change, which is leading to shorter periods of sustained ice cover, may have negative consequences for trout populations in the near future. / Tidigare studier har visat att yttäckande is medför många positiva effekter för öring (Salmo trutta), bland annat genom att utgöra skydd mot endoterma predatorer. Jag undersökte om det är den yttäckande isen i sig som medför beteendeförändringar hos juvenila öringar eller om det är det reducerade ljusinsläppet som isen medför. För att separera dessa två effekter gjordes beteendeobservationer med och utan ytis under samma ljusintensitet (500 lux). En ytterligare isfri behandling gjordes, med starkt ljus (3000 lux), för att kunna mäta öringens respons på ljusreduceringen. En uppstoppad mink användes för att simulera predationsrisken, detta för att kunna mäta fiskarnas antipredationsresponser under dessa tre förhållanden. Jag fann en signifikant behandlingseffekt på kropps- och ögonfärg. Under is hade fiskarna en blekare ögonfärg än när de befann sig under starkt ljus, som i sin tur resulterade i blekare färg än när fiskarna utsattes för svagt ljus. När det gäller kroppsfärg uppvisade fiskarna en blekare kroppsfärg under is än när de utsattes för de två isfria behandlingarna, vilka inte skiljde sig från varandra. Behandlingarna gav ingen effekt på gälslagsfrekvens, tid till att initiera födosök, tid till att initiera aktivitet eller simaktivitet, dock var tid till både födosök och aktivitet lägst och simaktivitet störst under is. Förändringarna i kropps- och ögonfärg indikerar att öring är mindre stressad under is, vilket eventuellt kan bero på att de uppfattar isen som en barriär mot terrestra predatorer. Dessa resultat tyder på att den pågående klimatförändringen, som innebär kortare perioder av ihållande yttäckande is, kan medföra negativa konsekvenser för öringpopulationer inom den närmaste framtiden.

No description available.

Mountain caribou, an arboreal lichen-feeding ecotype of woodland caribou (Rangifer tarandus caribou), have been extirpated from much of their historic range. Mountain caribou are federally listed as Endangered by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) and red-listed by the BC government. Habitat loss and fragmentation of old growth forest is the ultimate cause for population declines. Yet, predation, linked to apparent competition, is the proximate cause for high rates of mortality. One of the most imperiled populations resides in the Purcell Mountains of BC, which was experimentally augmented in 2012 with 19 northern caribou from northern BC. The caribou-predator literature predominantly focuses on the relationship between caribou and wolves (Canis lupus) in northern caribou populations. However, cougars (Puma concolor) have been identified as a major predator of Purcells-South (PS) caribou, yet caribou-cougar interactions remain largely unstudied. I evaluated cougar predation risk in space and time on resident and translocated caribou in the Purcell Mountains. To do so, I determined biologically relevant seasons for resident, donor (i.e. not translocated) and translocated caribou, and cougars. I then used these seasons to investigate seasonal patterns of movement and habitat use between the three groups of caribou and cougars. Next I used resource selection functions (RSFs) to estimate habitat based seasonal variation in predation risk. I used these RSFs to compare the seasonal habitat selection and risk to cougar predation between resident and translocated caribou. Five resident caribou seasons and two cougar seasons were defined. Translocated caribou displayed inconsistent movement behavior with no clear seasonal pattern. Resident caribou remained at high elevations year-round and selected for low risk cougar habitat during the calving season at the home range scale and year-round at the landscape scale. Translocated caribou displayed risky behaviour throughout the study period by traveling to mid to low elevations and habitats selected by cougars. Translocated caribou displayed the same general pattern of elevational movement as their northern conspecifics, spending the majority of their time at lower elevations than resident caribou. Of the 19 translocated caribou, 17 (89%) died during the study, six of which were preyed upon by cougars, two by wolves, and the remainder due to accidents or unknown causes. In summary, translocated caribou did not adopt the predator avoidance or habitat selection strategies of resident caribou. I recommend that future efforts to augment small caribou populations use donor caribou experienced with similar predators and that possess comparable seasonal habitat use to the recipient population. However, because most suitable donor populations are declining, a soft-release of captive-reared mountain caribou might be the best option for mountain caribou recovery efforts. / Graduate / 0366 / 0329

Consequences of within population variation have recently attracted an increased interest in evolutionary ecology research. Theoretical models suggest important population-level consequences, but many of these predictions still remain to be tested. These issues are important for a deepened understanding of population performances and persistence, especially in a world characterized by rapid fragmentation of natural habitats and other environmental changes. I review theoretical models of consequences from intra population genetic and phenotypic variation. I find that more variable populations are predicted to be characterized by broader resource use, reduced intraspecific competition, reduced vulnerability to environmental changes, more stable population dynamics, higher invasive potential, enhanced colonization and establishment success, larger distribution ranges, higher evolvability, higher productivity, faster population growth rate, decreased extinction risk, and higher speciation rate, compared with less variable populations. To test some of these predictions I performed experiments and compared how different degree of colour polymorphism influences predation risk and establishment success in small groups. My comparisons of predation risk in mono- and polymorphic artificial prey populations showed that the risk of being eaten by birds does not only depend on the coloration of the individual prey item itself, but also on the coloration of the other members of the group. Two experiments on establishment success in small founder groups of Tetrix subulata pygmy grasshoppers with different degree of colour morph diversity show that establishment success increases with higher degree of diversity, both under controlled conditions in outdoor enclosures and in the wild. These findings may be important for re-stocking of declining populations or re-introductions of locally extinct populations in conservation biology projects. I report on remarkably rapid evolutionary shifts in colour morph frequencies in response to the changed environmental conditions in replicated natural populations of pygmy grasshoppers in fire ravaged areas. This finding 1 illustrates the high adaptive potential in a polymorphic species, and indicates the importance of preserved within-species diversity for evolutionary rescue. Finally, I review if theoretical predictions are supported by other published empirical tests and find strong support for the predictions that more variable groups benefit from reduced vulnerability to environmental changes, reduced population fluctuations and extinction risk, larger distribution ranges, and higher colonization or establishment success. In conclusion, my thesis illustrates how within-population variation influences ecological and evolutionary performances of populations both in the short and long term. As such, it emphasizes the need for conservation of biodiversity also within populations.

The loss of large-bodied herbivores and/or top predators has been associated with large-scale changes in terrestrial, freshwater, and marine ecosystems around the world. Understanding the consequences of these declines has been hampered by a lack of studies in relatively pristine systems. To fill this gap, I investigated the dynamics of the relatively pristine seagrass ecosystem of Shark Bay, Australia. I began by examining the seagrass species distributions, stoichiometry, and patterns of nutrient limitation across the whole of Shark Bay. Large areas were N-limited, P-limited, or limited by factors other than nutrients. Phosphorus-limitation was centered in areas of restricted water exchange with the ocean. Nutrient content of seagrasses varied seasonally, but the strength of seasonal responses were species-specific. Using a cafeteria-style experiment, I found that fast-growing seagrass species, which had higher nutrient content experienced higher rates of herbivory than slow-growing species that are dominant in the bay but have low nutrient content. Although removal rates correlated well with nutrient content at a broad scale, within fast-growing species removal rates were not closely tied to N or P content. Using a combination of stable isotope analysis and animal borne video, I found that green turtles (Chelonia mydas) – one of the most abundant large-bodied herbivores in Shark Bay – appear to assimilate little energy from seagrasses at the population level. There was, however, evidence of individual specialization in turtle diets with some individuals foraging largely on seagrasses and others feeding primarily on macroalgae and gelatinous macroplankton. Finally, I used exclusion cages, to examine whether predation-sensitive habitat shifts by megagrazers (green turtles, dugongs) transmitted a behavior-mediated trophic cascade (BMTC) between sharks and seagrasses. In general, data were consistent with predictions of a behavior-mediated trophic cascade. Megaherbivore impacts on seagrasses were large only in the microhabitat where megaherbivores congregate to reduce predation risk. My study highlights the importance of large herbivores in structuring seagrass communities and, more generally, suggests that roving top predators likely are important in structuring communities - and possibly ecosystems - through non-consumptive pathways.