Diet, breeding success, detectability, and density of the great horned owl (Bubo virginianus) at its northern range limit

Thesis (M.S.) University of Alaska Fairbanks, 2019I studied the diet, breeding success, detectability, and density of great horned owls (Bubo virginianus) in the Middle Fork of the Koyukuk Valley in Arctic Alaska. The study extended from the southern slopes of the Brooks Range to latitudinal tree line, the northern breeding limit of the species, and included what are likely to be the northernmost great horned owl nests on record (up to 68.0113 degrees north). I completed the study during the 2017 and 2018 breeding seasons, during years of high snowshoe hare (Lepus americanus) abundance. The focus of this study was to gain an understanding of how high snowshoe hare abundance influences the recruitment, diet, and distribution of this apex generalist predator, and to determine best methods of detecting great horned owls for similar studies in the future. I used motion sensor cameras on nests as well as pellet analysis for diet and breeding studies, and call surveys for information on detectability and density. Great horned owl diet consisted mostly of snowshoe hares by mass (mean 80%, range 65-99%), with an average prey size of 714 g (95% CI ± 34.26). Nestlings received an average of 459 g (95% CI ± 75) of prey per chick per day, and the proportion of hares in their diet positively correlated with fledging success (P = 0.01). During call surveys, length of playback was the most important factor in detecting great horned owls throughout 12 minute surveys, reaching 23% (95% CI = ± 6.4) at 3 minutes, and up to 80% (95% CI = ± 6.1) at 9 minutes. Inclusion of silent listening periods may lessen the chance of detecting great horned owls during playback surveys, though a larger sample size is needed (P = 0.18). There was no correlation between cloud cover and probability of detection (P = 0.60) or wind speed and probability of detection (P = 0.28). However, there was a positive correlation between temperature and probability of detection (P = 0.02). Call surveys gave an estimate of 4.1 great horned owls per square kilometer (z = 4.302, 95% CI = ± 2.63). This was the northernmost study of North America's most widespread year-round bird of prey, and the first density estimate at their northern breeding limit.National Park ServiceChapter 1: Diet and Reproductive Success -- Chapter 2: Methods of Using Call Surveys to Detect Great Horned Owls -- General Conclusions -- References

Biological Barriers: Transdermal, Oral, Mucosal, Blood Brain Barrier, and the Blood Eye Barrier

© Springer Science+Business Media New York 2013. And Gregor Cevc 2013. All rights reserved. Compartmentalisation is a precondition for the development of life, allowing concentration gradients to be maintained, facilitating selective transport of molecules, functional polarisation, protection of cells and tissues. Consequently, organisms have evolved highly sophisticated structures and mechanisms that allow compartmentalisation to be maintained and controlled in a highly regulated fashion. Under normal conditions these compartmentalising structures are essential building blocks of life, their smooth functioning being central to our health. However, the same effectiveness that is a bonus under physiological conditions means the same structures may become considerable barriers to the pharmacotherapy of diseases, as access of drugs to the sites of disease may be severely restricted. This chapter describes the architecture, organisation, and function of key barriers that therapeutic nanoparticles may encounter for the most important routes of drug administration. The epithelial barriers (skin, mucosa of the airways, and gastrointestinal tract) and endothelial barriers share many commonalities as they all share key design elements that have evolved to support compartmentalisation