Theses and Dissertations from UMD
Permanent URI for this communityhttp://hdl.handle.net/1903/2
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
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Item MOVEMENT ECOLOGY OF THE MEXICAN FISH-EATING BAT, MYOTIS VIVESI(2020) Hurme, Edward; Wilkinson, Gerald S; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Foraging behavior is influenced by the distribution of prey in time and space and the presence of conspecifics. Echolocating bats, which advertise their behavior while vocalizing, provide a unique opportunity for understanding how an organism interacts with conspecifics and the environment to find food. Here I use GPS tracking combined with on-board recording to investigate the foraging movements of lactating Mexican fish-eating bats, Myotis vivesi, in the Gulf of California, Mexico, over a 5-year period. In Chapter 1, I assessed five alternative methods for behavioral state segmentation of GPS tracked foraging paths using on-board audio for validation. While most methods perform well, hidden-Markov model segmentation showed the highest accuracy at predicting foraging movement. In Chapter 2, I evaluated habitat selection across multiple scales for fish-eating bats foraging in the Midriff Islands Region in the Gulf of California. Foraging site use at large scales is most predictive and is associated with dynamic (chlorophyll concentration) and static variables (ocean depth, sea floor slope) consistent with known tidal upwelling regions. In Chapter 3, I examine the function of in-flight social calls recorded from roughly half of all tagged individuals during their foraging flights. Calls contained spectral differences among individuals, were associated with the ends of flights as bats return to their roost, and increased in occurrence with pup age, consistent with directive calls used to communicate with mobile pups. In Chapter 4, I explore how prey distribution impacts social behavior and foraging movements. On-board audio reveals that conspecifics are present during commuting and foraging and playback experiments demonstrate an attraction to foraging call sequences. In collaboration with several colleagues I combined these findings with data from four other bat species ranging in diet and habitat type. Taken together, bat species that frequently encounter conspecifics, such as Myotis vivesi, have ephemeral prey and variable flights (e.g. duration and foraging site location), whereas bats that forage solitarily have predictable or non-shareable prey, such as a congener Myotis myotis, show less variability in their flights. Overall, these results provide new insights into the foraging dynamics and social behavior of bats.Item COMMUNICATING IN SOCIAL NETWORKS: EFFECTS OF REVERBERATION ON ACOUSTIC INFORMATION TRANSFER IN THREE SPECIES OF BIRDS(2011) Blumenrath, Sandra; Dooling, Robert J; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In socially and acoustically complex environments the auditory system processes sounds that are distorted, attenuated and additionally masked by biotic and abiotic noise. As a result, spectral and temporal alterations of the sounds may affect the transfer of information between signalers and receivers in networks of conspecifics, increasing detection thresholds and interfering with the discrimination and recognition of sound sources. To this day, much concern has been directed toward anthropogenic noise sources and whether they affect the animals' natural territorial and reproductive behavior and ultimately harm the survival of the species. Not much is known, however, about the potentially synergistic effects of environmentally-induced sound degradation, masking from noise and competing sound signals, and what implications these interactions bear for vocally-mediated exchanges in animals. This dissertation describes a series of comparative, psychophysical experiments in controlled laboratory conditions to investigate the impact of reverberation on the perception of a range of artificial sounds and natural vocalizations in the budgerigar, canary, and zebra finch. Results suggest that even small reverberation effects could be used to gauge different acoustic environments and to locate a sound source but limit the vocally-mediated transfer of important information in social settings, especially when reverberation is paired with noise. Discrimination of similar vocalizations from different individuals is significantly impaired when both reverberation and abiotic noise levels are high, whereas this ability is hardly affected by either of these factors alone. Similarly, high levels of reverberation combined with biotic noise from signaling conspecifics limit the auditory system's ability to parse a complex acoustic scene by segregating signals from multiple individuals. Important interaction effects like these caused by the characteristics of the habitat and species differences in auditory sensitivity therefore can predict whether a given acoustic environment limits communication range or interferes with the detection, discrimination, and recognition of biologically important sounds.