The development of hydroelectric power production and the damming of water courses that ensues causes a threat to the migration patterns of Atlantic salmon (Salmo salar), by altering their habitat and compromising river connectivity. Because the species’ survival heavily depends on the completion of their migration between rivers and oceans, the design of guidance structures that promote successful passages around dams is a critical goal. Physical structures have been used to steer downwards-migrating smolts through safe fishways but they have not always proven effective, both from an ecological and economical perspective. In this study, the potential of bubbles in guiding salmon trajectories around a hydropower dam was tested as an alternative to existing guiding systems. Here the hypotheses were: i) bubbles guide downstream-migrating smolts around dams; ii) the reaction of smolts to a bubble barrier is linked to their individual boldness; iii) bubbles have varying effects on different school sizes. The first and third hypotheses were tested in the field, by recording sonar footage at the entrance of a fishway, downstream of a bubble barrier. The second hypothesis was evaluated by conducting a scototaxis experiment and an assessment of the reaction of young salmon to bubbles in the laboratory. My analysis of the fish abundance data collected in the river confirmed the first and third hypotheses. In the field, the presence of a predator (Esox lucius) was revealed to be a more influential factor than bubbles in regulating the number of smolts steered towards the fishway, indicating that predators generated a larger anxiety-like response in smolts than bubbles. In the controlled laboratory setting, there was no significant correlation between anxiety-like behaviour and reaction to bubbles and the second hypothesis did not appear to be valid. Therefore, the cause of avoidance of the barrier remains unclear, but bubble barriers seem to be an efficient and cost-effective structure for guiding downstream-migrating salmon smolts.

Several studies have investigated the ecological factors that affect behavior in Micrathena gracilis, a diurnal orb-weaving spider that forages on flying insects during the day. However, none yet have considered how the temporal distributions of prey and predator occurrences shape their daily behavioral rhythms, especially web construction, which involves a heavy energetic investment well in advance of potential nutritional benefit. Recently, several orb-weaving spider species have been shown to exhibit a variety of abnormal rhythms, suggesting that circadian clock-controlled rhythms may play an unexpected role in behavioral evolution. Despite the appearance of significant insect abundance in the evenings, M. gracilis individuals stop foraging, take down their webs, and retreat before they can capitalize on this opportunity. Is the nutritional benefit of this forfeited prey significant compared to what they collect during the day, and if so, what potential cost might justify opting out of this potential gain? To investigate, sticky traps for prey collection and a camera array for recording predator activity were used at a local field site to survey what risks and rewards these spiders face throughout the 24-hour day. Spider activity and web captures in the field were also used to confirm behavioral patterns and capture success throughout the day. It was found that spiders begin foraging when prey becomes available but cease while prey is still abundant. These observations appear to support a theoretical model of behavioral decisions under predation risk. However, recorded predation events were rare, and predation was not confirmed outside of the foraging timeframe. These results support the notion that the circadian rhythm of Micrathena gracilis is shaped by factors other than prey availability, but the theoretical pressure from predation risk requires further investigation.

The population dynamics of small mammal populations in Punda Maria, Kruger National Park, South Africa was investigated with respect to community size and structure, seed predation and dispersal of several trees. Species populations, community structure and habitat attributes were measured at six sites comprising of 3 habitat types (2 sites per habitat); namely Acaciagrassland, North-facing and South-facing sloped sites. Seasonal variation was investigated at the Acacia sites during late summer (April) and winter months (July). Five habitat attributes were measured; percentages of total cover and herbage, plant litter depth (cm), height of dominant vegetation type measured (m) and edaphic condition were recorded at 15 randomly selected traps per site. Almonds (Prunus dulcis), baobabs (Adansonia digitata), mopane (Colophospermum mopane), and Acacia tortilis seeds were used in the predation and dispersal experiment. North- and South-facing sites were dominated by Aethomys sp. while Acacia sites were dominated by Mastomys natalensis. Seed predation was high at the North-facing slopes, with a significant difference in predation on A. tortilis seeds. Seed dispersal activity was low; no , scatter hoarding was identified; only larder hoarding was observed by Aethomys sp. and M. natalensis at North-facing sites and Acacia sites respectively. Trampling by megaherbivore activity impacted vegetation structure and has negatively affected rodent population and ground activity, particularly at the Acacia sites.

Wetland species are declining and efforts are being made to protect wetlands and their biodiversity. In Europe, these efforts could be hampered by the recent rise in the Western European Common crane (Grus grus) population. Increasing anecdotal evidence has raised concerns that this population increase has led to an increase in crane predation on other bird species’ eggs and chicks. This study aims to investigate, weather cranes are a potential threat to other bird species by predating on eggs and chicks, and ultimately biodiversity. Proxies, like habitat selection and time devoted to foraging in wetlands, were used to investigate risk of crane predation. Habitat selection and time devotion were studied using location data derived from 13 GPS-tagged Common cranes during May and June in 2017 to 2019. Observational foraging data was collected in the protected wetland Kvismaren, Sweden in June 2019, including adult non-breeding cranes only. During daytime, the three habitats with highest mean relative probability of presence within a 95% confidence interval for cranes are open wetland (0.87, CI: 0.86-0.89), followed by inland water (0.60, CI: 0.56-0.63) and arable land (0.55, CI: 0.52-0.59). The proportion of time cranes spend in wetlands is 0.39 in May and 0.28 in June. Cranes spend a proportional majority of their time (0.69) on foraging behavior compared to other activities they perform in wetlands. Since every encounter with a chick or egg can end in predation and cranes spend most of their time foraging in wetlands a population increase in cranes could have severe impact on bird species. Future research should take into account crane diet, which categories of cranes (e.g., non-breeding versus breeding) are most likely to predate on eggs and chicks and the negative impact on bird populations in relation to crane numbers to fill in the major research gap in this field. Lastly, future studies should evaluate how an increasing crane population also could impact the abundances of other wetland species such as, rodents, amphibians, fish and invertebrates.

The origin and maintenance of much of natural biodiversity can likely be explained by theecological speciation theory. Ecological speciation is defined as the process whenreproductive isolation arises through divergent selection caused by ecological factors, such asbiotic interactions and abiotic conditions. Many populations of European whitefish(Coregonus lavaretus) are currently going through sympatric speciation from a single littoralecotype to two or more ecologically separate ecotypes. It has been hypothesized that northernpike (Esox lucius) is promoting speciation in whitefish by exposing it to a trade-off betweenpredation risk and resource availability causing an initial divergence in size eventuallyleading to two or more ecologically and genetically distinct ecotypes. After initial divergencesmall whitefish ecotypes often abandon ancestral spawning sites to spawn in streams or deepwater suggesting that the ecotypes are at least partially reproductively isolated. The driver ofthis reproductive isolation could be predation risk as pike mainly forage in the littoral. If thisis true, we would expect to find significantly higher predation risk for small whitefish at thelittoral spawning sites than on alternative spawning sites. To test this idea, hooks baited withsmall whitefish was placed at different spawning sites during the fall spawning season andchecked every 12 hour for 36 hours. Relative predation risk for small whitefish wassignificantly higher at the ancestral littoral spawning sites than at stream spawning sites. Inaddition, there was a significant decrease in predation risk later in the spawning season. Thisindicates that predation is promoting reproductive isolation in European whitefish byselecting against small individuals spawning at littoral spawning sites, but potentially also byselecting for delaying spawning in small individuals in the littoral. To fully understand thespeciation process in this system more studies must be done considering the complexity ofthe speciation process. Because of the lack of studies investigating predation as a cause ofbehavioral changes, that in turn promotes reproductive isolation, future studies should putmore emphasis on predation as a possible driver of reproductive isolation.

Amphibians have been facing global declines over the last decades due to direct and indirect effects of anthropogenic activities. One of the leading causes is environmental contamination, particularly that of waterbodies which are used by many amphibian species for reproduction, development, and adult life. An important source of contamination comes from agricultural runoffs of pesticides such as neonicotinoids, which are known to alter anuran survival, behaviour, predation stress response, and development. However, few studies have investigated the possible interactions between neonicotinoids and natural environmental stressors which could alter the strength and direction of observed neonicotinoid effects. This study investigated how a concentration of imidacloprid (a neonicotinoid) measured in surface waters interacted with high population density, an important environmental stressor, to influence behaviour and development across metamorphosis in wood frogs (Lithobates sylvaticus) known to breed in agricultural landscapes. I reared tadpoles in a fully crossed design experiment, between two densities (0.33 and 1 tadpole/L) and clean vs contaminated water (10 µg/L imidacloprid). Behaviours were measured in the absence and presence of predation cues using open-field tests at three distinct developmental stages, up to the metamorph stage. I found that imidacloprid did not interact with population density or independently affect behaviours in the absence of predation cues. However, individuals raised at high density compared with low density were more active at an early developmental stage but less active at metamorphic climax. Furthermore, both density and imidacloprid independently decreased the natural behavioural response (i.e., “freezing”) of tadpoles to predation cues. Both treatments also slightly accelerated metamorphosis while only density altered final mass at metamorphosis. Finally, I found that distance travelled was weakly repeatable between aquatic stages but not repeatable across metamorphosis, a pattern that was not affected by treatments. This study provides novel insights on the ecotoxicology of imidacloprid in the presence of a natural stressor, highlighting the importance of including behavioural assays and stressors in studies of amphibian ecotoxicology.

Daily rhythms occur in numerous physiological and behavioral processes across an immense diversity of taxa, but there remain few cases in which mechanistic links between rhythms of trait expression and organismal fitness have been established. We construct a dynamic optimization model to determine whether risk allocation provides an adaptive explanation for the daily foraging rhythm observed in many species using the orb-weaving spider Cyclosa turbinata as a case study. Our model predicts that female C. turbinata should generally start foraging at lower levels of energy reserves (i.e., should be less bold) during midday when predators are most abundant. We also find that individuals’ foraging efficacy determines whether daily rates of encounters with predators or prey more strongly influences boldness under high risk. The qualitative model predictions are robust to variation in our parameter estimates and likely apply to a wide range of taxa. The predictions are also consistent with observed patterns of foraging behavior under both laboratory and field conditions. We discuss the implications of our study for understanding the evolution of daily rhythms and the importance of model predictions for interpreting empirical studies and generating additional hypotheses regarding behavioral evolution.

Nest success of dabbling ducks in the Prairie Pothole region of North America has been declining for the past 40 years in parallel with declines in duck populations. Low nest success seems to result from the combination of an extremely fragmented breeding ground in a human-dominated landscape with an abundant and expanding ii community of generalist nest predators. Studies that examined variables associated with nest vulnerability to predation have produced contradictory results, likely because of simplistic approaches, lack of spatio-temporal replication, use of artificial nests , and the effect of confounding variables. I attempted to clarify the equivocal findings of previous studies by using multiple regression to simultaneously examine the effect of several variables purportedly related to nest predation risk. I collected data on >1,800 dabbling duck nests and associated variables for 16 habitat patches (14 managed for duck production) during two nesting seasons in North Dakota. At the habitat patch level, early and late in each breeding season, I studied the relationship of nest success and upland area, nest density, predator abundance and richness, abundance of alternative prey for predators, and visual and physical obstruction provided by the vegetation . At the spatial scale of the nest and its neighborhood, I examined the likelihood of nest predation in association to nest initiation date, year, distance from nest to a wetland and to an edge, vegetation type at the nest, visual obstruction and heterogeneity of the vegetation around the nest, duck nest species , predator abundance, and presence/absence of 5 carnivorous predators at the nest habitat patch. Nest success was generally low and highly variable in time, and among and within habitat patches. I found no relationship between nest success and any of the variables measured at the patch scale. At the nest level, only initiation date, distance to water, visual obstruction, predator abundance, and duck species had an effect. High variability in the data and the lack of patterns in the relationship of nest predation and the predictor variables precluded me from building a predictive model that explains nest success. Nest success could not be predicted, predation was incidental and risk was high, and there were no safe nest sites for hens to choose in a landscape swamped by nest predators . Nests were located randomly; therefore, there were no clues predators could use to enhance their success in finding nests.

Canid predation poses a serious threat to the sheep industry in the United States. Llamas are becoming popular among livestock producers as part of their predation management programs but there is little information on the factors associated with llama guarding behavior. This study examined several physical and behavioral attributes of individual llamas to assess whether they might predict the aggressiveness llamas display coward canids. The study was conducted in three phases. The first involved determining some physical and behavioral traits of individual llamas. Twenty individuals were randomly assigned to one of four groups (n = 5/group) and frequencies with which animals initiated and responded to various behaviors, e.g., dominance, aggression, threats, subordination, leadership, and alertness, were documented using focal-group sampling. Individuals were then ranked according to the frequency with which they displayed each behavior. In the second phase, activity patterns of individual llamas with sheep were assessed. Lamas varied in how close to sheep they stayed (mean = 48.2 m I 3.5) as we 1 as in the way they distributed their activities. The third phase examined interactions among llamas, sheep, and a domestic sheep dog to assess their individual aggressiveness toward canids. Llamas varied in the degree of aggressiveness displayed toward the dog; some chased the dog, others ran from it, some stayed with the flock, and others did not. Llamas were ranked based on these responses. Llamas with top ranks were curious and chased the dog, but stayed close to the sheep. Bottom-ranked individuals ignored the sheep and ran from the dog. Physical and behavioral traits of llamas and their behavioral patterns with sheep were then compared with aggressiveness they displayed toward the dog. Leadership and alert behaviors were correlated with aggressiveness (r = 0.472, p = 0.064 and r = 0.607, p = 0.012, respectively) Weight of llamas was also correlated with aggressiveness (r = 0.475, p = 0.039). Llama coloration was associated with aggressiveness they displayed toward the dog (X2 = 6.003, df = 2, p = 0.049), however, color was also associated with the weight of llamas (X2 = 7.49, df = 2, p = 0.024). Traits correlated with llama aggressiveness are easily recognized and sheep producers interested in acquiring a llama should consider them when selecting livestock guardians.

Juvenile rainbow trout Oncorhynchus mykiss stocked into mid-elevation reservoirs in Utah are vulnerable to predation from piscivorous fish and birds. I determined how effectively juvenile trout used cover to avoid these predators by (1) direct observations (snorkel transects) of habitat selection in two reservoirs and (2) measurements of survival and growth rates in a pond experiment where adult brown trout Salmo trutta were predators. Observations of juvenile trout were conducted within five weeks of stocking in 1988 and 1989. During the day, juvenile trout were abundant in complex inshore habitats and avoided simple habitats such as sand and gravel. Measurements of gut fullness indicated that juvenile trout fed during the day but not during the night. Large Daphnia comprised more than 95% of the diet of juvenile trout. Because large Daphnia were often higher offshore than inshore in both reservoirs, selection of inshore cover is believed to be primarily a response to reduce predation risk. At night, trout in both reservoirs selected more exposed areas and rested on the bottom. In the pond experiment, the presence of brown trout significantly increased mortality of juvenile trout, decreased their growth rates, and caused them to avoid offshore areas. The presence of cover significantly decreased predation rates but did not affect growth of the juvenile trout.