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Equidae belong to a group of large herbivores, which survival in natural environment depends beside others on their capability of fast predator recognition and detection. They can sensually recognise a possible threat in advance and react by immediate escape, which increases their survival. Also domestic horses still show very sensitive reaction to sudden (unexpected) stimuli. So we assume, that the ability to detect predator immediately is conserved despite of the long domestication process. The supportive indirect evidence is given by the successful breeding of the feral herds all over the world. However, studies showing the direct reaction of domestic horse toward the canids (as the most common predators), are still absent. Aim of the work was to find, if the horses (Equus caballus) could recognize acoustic sign of dogs like predators and if they could recognize the level of potential threat according to the number of predators, similarly as their wild ancestors. The recordings of barking of big dog breeds were obtained and modified. The final recording contained the set of barking coming from one individual or three different. The recording was played to the experimental horses, under controled conditions, together with white sound as a control. The reactions were recorded. Altogether 12 horses out of...

Equidae belong to a group of large herbivores, which survival in natural environment depends beside others on their capability of fast predator recognition and detection. They can sensually recognise a possible threat in advance and react by immediate escape, which increases their survival. Also domestic horses still show very sensitive reaction to sudden (unexpected) stimuli. So we assume, that the ability to detect predator immediately is conserved despite of the long domestication process. The supportive indirect evidence is given by the successful breeding of the feral herds all over the world. However, studies showing the direct reaction of domestic horse toward the canids (as the most common predators), are still absent. Aim of the work was to find, if the horses (Equus caballus) could recognize acoustic sign of dogs like predators and if they could recognize the level of potential threat according to the number of predators, similarly as their wild ancestors. The recordings of barking of big dog breeds were obtained and modified. The final recording contained the set of barking coming from one individual or three different. The recording was played to the experimental horses, under controlled conditions, together with white sound as a control. The reactions were recorded. Altogether 12...

No description available.

L’affaissement et la dégradation des sols organiques, utilisés pour les cultures maraîchères du Québec, sont actuellement des sujets criants. Ces sols très fertiles sont utilisés pour la production d’environ 50 % des légumes au Québec. Cependant, une partie de cette ressource est perdue, à chaque année, à cause de l’érosion et de l’activité microbienne. Plusieurs mesures sont actuellement prises pour réduire ces pertes, telles que l’utilisation de brise-vent et la réduction des labours, dans le but d’augmenter la durée de vie de cette ressource. Toutefois, ces méthodes ne sont pas suffisantes et ne considèrent pas les facteurs biotiques derrière la dégradation des sols organiques. La respiration (oxydation) microbienne représente pourtant plus de 50 % de la perte totale de matière organique dans le sol. Comme les nématodes libres sont les prédateurs principaux du microbiote, leur abondance et leur diversité pourraient influencer les populations microbiennes, mais les conséquences de cette interaction sur la composition et la diversité des communautés sont peu connues. Cette étude fait ressortir le rôle indirect des nématodes dans la dégradation de la matière organique via la prédation des bactéries et des champignons dans le sol et la régulation de ces communautés. Nous avons manipulé les communautés de nématodes afin d’observer des variations de composition et de diversité dans la communauté bactérienne, ainsi que dans les processus de dégradation de la matière organique. Des variations significatives ont été observées pour la production possible d’enzymes extracellulaires provenant des bactéries, l’abondance des bactéries, la disponibilité de l’azote dans le sol et le rendement des feuilles de laitues. Ces résultats permettent de faire ressortir l’importance de la prédation des nématodes et la nécessité d’accorder à ce groupe une plus grande attention dans la mise en place de systèmes de production végétale. L’ajustement des pratiques culturales pourrait aider à maintenir des réseaux écologiques plus stables et augmenter la longévité des sols organiques. / The subsidence and degradation of organic soils, used for vegetable crops in Quebec, is currently a critical issue. These very fertile soils are used for the production of about 50% of the vegetables in Quebec. However, part of this resource is lost every year due to erosion and microbial activity. Several measures are currently being taken to reduce these losses, such as the use of windbreaks and the reduction of plowing, to increase the life span of this resource. However, these methods are not sufficient and do not consider the biotic factors behind organic soil degradation. Microbial respiration (oxidation) accounts for more than 50% of the total loss of organic matter in the soil. Free-living nematodes are the main predators of the microbiota, their abundance and diversity could influence microbial populations, but the consequences of this interaction on community composition and diversity are poorly understood. This study highlights the indirect role of nematodes in the degradation of organic matter via predation of bacteria and fungi in the soil and the regulation of these communities. We manipulated nematode communities and observed variations in composition and diversity in the bacterial community, as well as in organic matter degradation processes. Specifically, significant variations were obtained for the possible production of extracellular enzymes from bacteria, bacterial abundance, soil nitrogen availability, and lettuce leaf yield. These results serve to highlight the importance of nematode predation and the need for greater attention to this group in the development of crop production systems. Adjusting cultural practices could help maintain more stable ecological networks and increase the longevity of organic soils.

A growing body of research focuses on how background sounds shape and alter critical elements of animals’ lives, such as foraging behavior, habitat use, and ecological interactions (Bradbury & Vehrencamp, 2011; Barber et al., 2010; Kight & Swaddle, 2011; Shannon et al., 2016). Much of this research has centered on the effects of anthropogenic noise (Dominoni et al., 2020; Francis & Barber, 2013; Ortega, 2012; Swaddle et al., 2015), but recent studies have also revealed that natural sound sources can influence animal behavior (Davidson et al., 2017; Le et al., 2019). Natural sounds, such as crashing surf, can create conditions where signaling and listening are difficult, but how this influences different species’ ecological interactions are unknown. To study the effects of crashing surf sound we experimentally introduced landscape-level acoustic playbacks where surf sound was not naturally present to create a “phantom ocean”. Phantom ocean treatment sites were employed alongside higher frequency “shifted” treatment sites to test for frequency-dependent effects, “real ocean” sites where surf sound was endemic, and ambient control sites. The phantom and shifted treatments were played continuously during the spring and summer of 2017-2019. Within this acoustic experimental landscape we conducted multiple studies to test the effects of crashing surf sound on animal behavior, habitat use, and ecological interactions. Through an artificial caterpillar predation experiment modeled after Roslin et al. (2017), we found that when exposed to natural sound treatments the foraging activity of rodents and arthropods increased, while that of birds declined. A potential explanation for this pattern includes taxon-specific responses reflecting different perceived risk-reward trade-offs in natural sound conditions. To follow this up we performed occupancy modeling on data collected by camera traps set within our system. We observed different responses among groups of species with different functional roles in the community for both detection (p) and occupancy (Ψ) probabilities. Our combined results indicate different species and functional groups have unique foraging behavior and patch use responses to natural sounds, likely based on their ecological interactions. Specifically, Cricetid rodents are likely more active in areas exposed to natural sounds, possibly due to lower perceived predation risk because mesocarnivores are less active. Insectivorous birds are also likely less active under natural sounds conditions, although the frequency of the sound, and the body size and diet of the bird appear influential. Together these findings suggest that natural sounds shape not only individual behavioral adjustments, but also multi-trophic, community level interactions. Our results show that natural sounds are an important driver of ecological interactions, but much remains to be uncovered. The mechanisms by which natural sounds influence individuals, populations, and many other aspects of ecology remain unexplored and provide fertile ground for future inquiry.

The potential impact of generalist predators on armyworm mortality was evaluated in the field, through a predator removal study, and in the laboratory, through controlled feeding trials. The most common potential armyworm predators removed from the field included ground beetles (Carabidae), rove beetles (Staphylinidae), ants (Formicidae), and spiders (Araneae). Armyworm damage to corn plants was significantly greater where generalist predator populations were reduced, through the use of pitfall traps and exclusion arenas, than in the control where predator populations were unaltered. The differences in the proportion of damaged plants and the degree of damage between the predator removal treatment and the control were statistically significant. Generalist predator consumption rates of live armyworm larvae in the laboratory were variable, however most predators did feed on the larvae. Large carabid beetles, including Pterostichus chalcites Say, Pterostichus lucublandus Say, and Scarites subterraneus F., exhibited the highest consumption rates. Generalist predators were sampled in four reduced-tillage corn systems which differed in the degree of soil disturbance and quantity and structure of the surface mulch due to tillage and cover crop management practices. The two sampling methods which were used, pitfall trapping and vacuum sampling, showed similar trends in predator abundance. The treatment with the highest degree of mulch ground cover had the highest overall predator abundance while the treatment which was disked and had no surface mulch had the lowest. Although several species tended to prefer the system with the least amount of ground cover, most of the common species preferred the treatment with the most groundcover. Pitfall trap catches over a three-day period indicated that predator activity was significantly higher during the day than night in all treatments. However, a laboratory study provided evidence that night activity in the field may have been reduced due to unusually low temperatures. Catch data from pitfall traps, unbaited and baited with live armyworm larvae, indicated that long-distance chemical detection is not an important cue for generalist predators in finding armyworm as prey. A removal sampling technique was used and evaluated for estimating the absolute densities of ground beetles (Carabidae). Removal sampling is a method of absolute density estimation based on the decline in successive catch numbers as individuals are removed from a population. Field arenas were used to isolate sampling areas in a no-till corn field and barrier pitfall traps were installed within the arenas to remove the carabids. Three three-week sampling trials were conducted in 1991 providing data for estimates on 5 June, 26 June, and 17 July. A single six-week sampling period was conducted in 1992 providing data for estimates on 2 June based on three, four, five, and six weeks of sampling. A linear regression method was used for calculating the estimate from the removal sampling data. The technique's practicality and agreement with the assumptions of removal sampling are discussed. / Master of Science

Effective delineation and management of stream fish populations requires a thorough knowledge of dispersal patterns, because these patterns affect a number of other demographic rates such as population growth, reproduction, survival, and gene flow. Previous studies of stream fish dispersal patterns have generally established species- and stream-specific home ranges and movement rates, but have largely failed to account for the environmental variables that may cause these parameters to vary. Many fishes occupy a variety of streams across a broad spectrum of ecological conditions, and movement rates (and thus population dynamics) may respond to these environmental gradients. Furthermore, enhanced understanding of the ecological features that induce or impede dispersal will help guide future management of stream channels for population connectivity. To determine the instream features that influence the dispersal patterns of darters, I conducted a spatially intensive mark/recapture study of three darter species in the upper Roanoke River watershed. Logistic regression was used to relate observed inter-riffle movements to gradients in riffle and corridor attributes. During the first study period, habitat area loss and habitat spacing drove dispersal patterns. However, a model developed from these data transferred poorly to the second study period, in which density dependence was a more effective predictor of dispersal. Individual size did not seem to influence the probability of emigration, but did influence the distance traveled following emigration, particularly for the two more specialist species. This finding suggests a size-based dominance hierarchy for habitat selection and occupancy in darters. Predation threat had only a minor effect on the probability of traversing inhospitable corridors, but experimentally introduced structural cover significantly elevated dispersal rates through such corridors. Taken together, results of this study indicate that a complex array of ecological features interact to produce heterogeneity in dispersal rates across the stream landscape. Knowledge of these influences can be used to manage stream channels for dispersal permeability. In addition to field studies, laboratory studies were undertaken to determine the efficacy of visible implant elastomer (VIE) and injectable photonic dye (IPD) for marking darters. No previous studies have rigorously evaluated these marks in darters, and comparisons of the two technologies in any taxa are few. Results of the laboratory study indicated that VIE is preferable to IPD for marking darters, particularly when mark longevity greater than 80 days is desired. Individuals marked with VIE exhibited higher survival and mark retention rates than did individuals marked with IPD. Additionally, VIE mark retention was more consistent across body locations. Retention of both marking technologies was biased by color. My study indicates that the results of tagging efficiency studies are not applicable across taxa, and that pilot studies are necessary prior to field use of marks in previously untested species. / Master of Science

Doctor of Philosophy / Department of Biology / Kimberly A. With / The loss, fragmentation, and degradation of grasslands have resulted in widespread declines in grassland birds. Nest predation is the leading cause of avian reproductive failure; therefore minimizing nest predation can lessen the severity of bird declines. Snakes are important predators of bird nests, but little is known about how snakes may enhance predation risk. To address this issue, I studied the habitat use, movement behavior, population genetic structure, and connectivity of snakes in the grasslands of northeastern Kansas. I addressed the connectivity of eastern yellowbelly racer (Coluber constrictor flaviventris) populations by using a landscape genetics approach at a broad scale (13,500 km2). I also radio-tracked the yellowbelly racer and Great Plains ratsnake (Pantherophis emoryi) at Konza Prairie Biological Station to understand their spatial ecology while simultaneously evaluating nest survival in grassland birds. Individual racers had limited dispersal (<3 km), but substantial admixture occurred within 30 km and populations were in migration-drift equilibrium and had high allelic diversity; therefore, racers must be abundant and continuously distributed for gene flow to be fluid throughout the region. Racers may be more likely to encounter bird nests, as they had more frequent movements and traversed greater distances on average than ratsnakes, which exhibited long periods of inactivity between directed movements. As for grassland birds, nest survival rates decreased with increasing shrubs and decreasing vegetation height. Discriminant function analysis revealed that successful nests were likely to occur in tall vegetation but reduced shrub cover, whereas higher shrub cover characterized snake habitats. Because snakes often use shrubs, nests in areas of increased shrubs may be at higher risk of predation by snakes. Targeted removal of shrubs may increase nest success by minimizing the activity of predators attracted to shrubs. Although predator removal is often a strategy for protecting bird populations, it may not be feasible in this instance, especially since snakes are a native component of the grassland community. Efforts to reduce snake predation on grassland bird nests should therefore focus on managing habitat within grasslands (i.e., shrubs) that influence snake activity, as no natural or anthropogenic habitat barriers currently limit snake movement across the landscape.

There is an inherent tension between a seller and a buyer as their relationship progresses towards closing the deal.The salesperson fears that the buyer wastes his time, which he could otherwise spend towards real potential buyers.The buyer questions the sincerity of the salesperson. Both evaluate the amount of trust and cooperation they should invest in the relationship. It is possible, after all, that the salesperson wants to take advantage of every weakness he detects in the buyer in order to guarantee the sale, and it is equally possible that the buyer tries to fool the salesperson, with false credit information for example. This thesis examines tensions that exist between salespeople and buyers by using an extended version of grounded theory, by which date is collected and analysed both qualitatively and quantitatively. It demonstrates that perceived predation reduces considerably the quality of the relationship.The thesis suggests that the phenomenon of predation exists in every sphere of human activity, including in the legal system.The PARDU Model ( pr edator-pr ey) initially developed to discuss the phenomenon of predation evolves, as the research progresses, towards the OPERA Model and the MESLYª grid, which offer pratical tools to better manage informational predation.