• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 96
  • 70
  • 32
  • 9
  • 8
  • 7
  • 1
  • 1
  • Tagged with
  • 343
  • 170
  • 132
  • 111
  • 98
  • 91
  • 60
  • 53
  • 52
  • 50
  • 40
  • 35
  • 34
  • 33
  • 26
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

A Confluence of Invasion, Behavioral, and Theoretical Ecology: What Drives Ephemeral Metacommunity Re-assembly?

Blanchard, Jesse Ryan 30 March 2018 (has links)
Metacommunity theory has been particularly useful in understanding the way spatially structured communities assemble. Both niche and neutral processes are known to influence metacommunity assembly, and the relative influence of each depends on the level of dispersal-limitation. Contemporary trait-based analyses of metacommunity assembly have enhanced our understanding of these processes. Of the traits investigated, individual personalities have received the least attention, but have been suggested to be drivers of metacommunity assembly model parameters, such as dispersal tendencies and patch density. I address this topic from three angles, three chapters, in this dissertation. First, I used a three-year field survey of fish metacommunity assembly in Everglades National Park to investigate the influence of dispersal-limitation on trait-based metacommunity assembly, asking which traits were important under different levels of dispersal-limitation. I found that the relative influence of traits and local environmental factors decreased, and the influence of regional factors increased with increasing dispersal-limitation. The Rocky Glades has recently been invaded by a micropiscivore with many novel traits, the African Jewelfish. In the second chapter I used my field data to ask what influence this invader has on metacommunity assembly. Overall, African Jewelfish abundance was the third most influential factor in driving assembly. I also used data, which were previously collected by collaborators, from three years prior and two years following the invasion to observe shifts in assembly rules. Assembly became significantly more aggregative immediately following the invasion, a condition which persisted more than a decade later. All previous studies asking the same question, found the same result: invasive introductions correspond with increased species aggregation. This may be a consistent, taxa-independent signal of truly invasive species that can be detected early in the invasion process, making it a potentially useful management tool after further empirical review. In the final chapter, I investigate the potential influence of individual personalities on a metapopulation’s structure. To do this, I used a behavioral individual-based model to explore the influence of sociability, an individual’s propensity to associate with conspecifics, on metapopulation structure at ecologically relevant spatiotemporal scales. I found that individual sociability can significant influence key metapopulation parameters such as dispersal distance and patch density but may not influence landscape occupation. Chapter three concludes with new hypothesis to be evaluated by future field studies. Overall, this dissertation demonstrates the relative roles of invasions, species traits, and individual personalities on metacommunity assembly processes.
12

How stimuli by toys affect pigs growth, health and welfare

Södergren, Carin January 2010 (has links)
Pigs do naturally have a high motivation to explore their environment. In a poor environment pigs still display this motivation and when there is no stimulation in the pen, pigs direct their behavior at pen-mates and pen components. Lack of stimulation can lead to decreased welfare and increased stress. This study investigates if extra stimuli by toys would affect pigs growth, health and welfare. Growing pigs (219) were followed during 7 weeks and divided into twenty two pens, eleven with toys and eleven without toys. I found partly support for the prediction that toys would help in a short time perspective but there was no support for the prediction that in a longer run the toys (used in this experiment) would increase pigs welfare. One explanation to this might be the straw that all the pens had (by law in Sweden), which seemed to be the most importuned component for satisfying pigs behavioral needs.
13

Etologické projevy u krav chovaných v systému bez tržní produkce mléka / Ethological manifestation at the beef cows bred in the system without market milk production

VESELÁ, Jana January 2008 (has links)
The aim of the work was evaluate on the dynamic of live performance at the beef cows in the system of breeding cows withour market milk production in the subnountain areas. The chosem method was a direct group observation within ten-minute intervals. The longest duration of pasture was in autumn 59.6 % of the day and the shortest in winter 30.8 % of the day. The activity of lying depended on standing and decreased from spring period 15.3 % of the day on 5.7 % of the day in winter period. The observation flows to the fact, that breeding of the livestock from welfare and adaptability herd of view is suitable in sub-mountain areas.
14

The foods and associated feeding behavior of the Yellow-bellied Marmot, Marmota flaviventris

Jonasson, Mark William 01 January 1981 (has links)
No description available.
15

Circadian Rhythms of the Spider Pholcus phalangeoides in Activity Monitors and Web Boxes

Dirmeyer, Steven 01 May 2019 (has links)
Circadian rhythms are endogenous molecular clocks that correspond to the 24-hour day and are regulated by light stimulus, allowing organisms to entrain to the dawn-dusk cycle. These clocks may allow organisms to anticipate daily events, influencing their behavior. In arthropods, including spiders, circadian rhythmicity is tested using activity monitors, which house individuals in tubes. However, this does not reflect the natural habitat of many spiders. We compared the locomotor activity of the cellar spider Pholcus phalangiodes in activity monitors with the locomotor activity in web boxes. After being entrained to a 12:12 light:dark cycle, the spiders were recorded in constant darkness. The resulting free-running periods demonstrated similar clock data for spiders in tubes as in boxes. This validates the activity-monitor research method.
16

A taxonomic study of two nominal subspecies of pikas (Ochotona princeps) in the Cascade Mountains of Oregon

Coots, Richard M 01 January 1972 (has links)
Pikas from four colonies in the Cascade Mountains of Oregon were examined. Two colonies were chosen from within the geographical distribution of two nominal subspecies. A discriminate analysis of morphological measurements taken from the specimens showed that each colony could be distinguished from each other. Each colony studied showed more intra-colony similarity than inter-colony similarity regardless of distance separating the colonies or subspecies designations. The results indicate that the validity of subspecies designations for this species can be questioned.
17

Dominance and Communication in a Cooperatively Breeding Bird

Dey, Cody 06 1900 (has links)
Social dominance can influence the allocation of resources in animal groups and has important consequences for individual fitness. In my thesis, I examined the structure, formation, maintenance and consequences of dominance, in the cooperatively breeding pukeko (Porphyrio melanotus melantous: Aves). I first describe a quantitative analysis of pukeko dominance networks (Chapter 2), which included one of the first applications of exponential random graph models in behavioural ecology. This study demonstrated that pukeko form highly ordered dominance hierarchies, and that dominance relationships were influenced by both the attributes of individual birds, as well as self-organizational processes such as winner and loser effects. Additionally, I demonstrated that hatching order has an important influence on the formation of dominance relationships, with earlier hatched chicks achieving higher dominance ranks as adults (Chapter 3). To maintain dominance relationships, pukeko use their red frontal shield as a ‘status signal’, with larger frontal shields indicating more dominant individuals. I showed that sexual dimorphism in frontal shield size is dramatically different in two pukeko populations, probably due to differences in the intensity of intrasexual competition (Chapter 4). Furthermore, by manipulating apparent frontal shield size, I demonstrated that shield phenotype both influences, and is influenced by, social interactions (Chapter 5). This bi-directional relationship between signals and social interactions challenges conventional signalling theory, and has important implications for how honesty is maintained in this signalling system. Finally, I expanded my findings on pukeko colour traits by exploring interspecific patterns of bill colouration in over 1600 bird species (Chapter 6). This study revealed that colourful bills likely evolved as a signal used in competitive interactions, rather than as a sexual signal. Taken together, my research provides a significant advancement in our understanding of the complex nature of dominance in a wild bird, and provides both a methodological and theoretical basis for future studies on animal social behaviour. / Thesis / Doctor of Science (PhD)
18

Effects of Anthropogenic Noise on the Provisioning Behavior of Western Bluebirds and Artificial Light at Night on Nestling Development

Ozkan, Kerstin H. 01 March 2024 (has links) (PDF)
Sensory environments are rapidly changing due to increased human activity in urban and non-urban areas alike. For instance, background sounds can interfere with parent-offspring communication and mask cues reflective of predation risk, resulting in elevated vigilance at the cost of provisioning. In chapter 1, we studied nestling provisioning behavior among Western Bluebirds (Sialia mexicana) in response to short-term (1 hr) and long-term (continuous exposure throughout nesting period) noise exposure. Provisioning rates were lower at nests exposed to short-term experimental traffic noise compared to exposure to ambient background sounds. Trial order strongly influenced provisioning behavior, with the decline in provisioning during noise playback occurring only during the second broadcast period of sounds. In contrast, provisioning rates increased with sound levels among nests exposed to long-term noise. Additionally, birds nesting in areas with high levels of noise returned to the nest more quickly than those in quiet areas following a simulated predation attempt. This study suggests that behavioral responses to short-term, experimental exposure to noise may not always be reflective of responses to longer-term noise exposure in real-world settings. It is essential to be cognizant of potential differences between experiments and real-world conditions as urbanization and sensory pollutants increase. The pervasive spread of artificial light at night has been documented to disrupt natural rhythms with varying consequences on wildlife. Disruption to the night sky can alter nestling development either through indirect exposure to light or due to changes in adults’ behavior, both having potential physiological costs or benefits. In chapter 2, we experimentally manipulated light outside of Western Bluebird nesting cavities and investigated whether exposure to light at night affects nestling development and adult behavior. Our results found no evidence of light at night affecting the onset or cessation of adult daily activity. However, we found that nestlings exposed to light have smaller wing chords and lower mass, but better overall body condition than those in the control. The number of chicks in the nest also strongly influenced the effect of the light at night: nests exposed to light with brood sizes of three nestlings had smaller wing chords and better body condition than nests without lights, but there were no strong differences between light exposed and dark nests with five chicks. Although light exposure appears to improve chick body condition, the chicks were smaller overall. These findings suggest that indirect artificial light outside the nesting cavity is enough to have consequences on the development of nesting birds, and ecologically relevant light exposure appears to alter chick condition without a temporal shift in parental behavior.
19

Temporal Factors Affecting Foraging Patterns of a Diurnal Orb-weaving Spider, Micrathena gracilis (Araneae: Araneidae)

Long, Mitchell Davis 01 May 2020 (has links)
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.
20

Socially influenced behaviour and learning in the context of food choice and egg-laying sites in Schistocerca gregaria

Lancet, Yaara 10 1900 (has links)
<p>Social learning, defined as learning from other individuals, has been well studied in vertebrates and social insect species. In order to promote further understanding of the evolution of social learning, I tested a non-social insect for social learning and socially influenced behaviour. The desert locust (Schistocerca gregaria) is a gregarious insect which has the opportunity for social learning and can benefit from such ability. Locusts showed rapid individual learning, preferring a diet they have experienced over another of equal nutritional quality. Adult locusts also showed socially influenced behaviour, preferring to eat and lay eggs in the vicinity of other locusts over doing so alone. Fifth instar locusts did not show the same socially influenced behaviours. Neither adult nor nymphs showed social learning after interacting with previously fed models or after observing models feed through a screen. These results provide evidence for socially influenced behaviour in locusts and for a difference in social behaviour between nymphs and adults. Further research utilizing locusts as a model system may help us gain a better understanding of the evolution of social learning.</p> / Master of Science (MS)

Page generated in 0.0505 seconds