Browsing by Subject "Predation"
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Item Behavior & cause-specific mortality of Mule Deer (Odocoileus hemionus) fawns on the National Rifle Association Whittington Center of North Central New Mexico(2013-08) Taylor, Chase A.; Gipson, Philip S.; Wallace, Mark C.; Cox, Robert D.Declining trends have been reported in most mule deer (Odocoileus hemionus) populations in New Mexico and other western states. This includes the Rocky Mountain mule deer (Odocoileus hemionus hemionus) population on the National Rifle Association Whittington Center (WC) in north-central New Mexico where our study was conducted. Our objectives were to determine causes of mortalities of mule deer fawns and estimate seasonal survival rates. We hypothesized low fawn survival rates due to high predation rates by Black bears (Ursus Americana). We radio marked fawns (n=50) born on the WC during 2011 and 2012. We applied a series of biological covariates (age, sex, birth weight, resistance, stability, vocalization, total body length, chest girth and habitat types) to estimate survival rates at 14 days post capture and weekly survival through summer and fall. Survival analyses were performed using Program MARK (6.2). We implemented corrected Akaike’s information criteria (AICc) to determine covariates that were significant to survival. Our observations suggested the habitat types where fawns were captured might have been correlated to survival, but we failed to detect a significant relationship. Predation was the major source of neonate mortality accounting for 86.8% of deaths. Black bear were the highest source of predation on fawns ( 57.5%, n=19) and total mortality (49.9%), verifying our hypothesis. Coyotes (Canis latrans) were the second highest predation source ( 36.3%, n=12) and total mortality (31.6%). Eight month mean survival estimate was 24.4%. These survival estimates are slightly higher than those from a previous investigation in the same area. We also observed and analyzed behaviours of fawns from parturition to two weeks of age that influenced mortality rates. I intended to develop recommendations that landowners and game agencies can use to manage habitats and help reduce declines of mule deer populations.Item Effects of post-settlement habitat use and biotic interactions on survival of the seagrass-associated fish red drum (Sciaenops ocellatus)(2009-12) Fencil, Megan Christine; Holt, J. (Joan); Dunton, Kenneth H.; Montagna, Paul A.; Rocha, Luiz A.; Rooker, Jay R.Due to high mortality encountered by marine fish larvae during their first weeks of life, small changes in the number of individuals surviving through this period can cause large fluctuations in year-class strength. Larval Red Drum (Sciaenops ocellatus) are dependent upon structured estuarine habitat to avoid predation. A study of post-settlement larval Red Drum distribution in a subtropical seagrass meadow in Mission-Aransas Estuary, Texas, USA indicates that larvae settle over approximately two months. Abundance of larger settled larvae was significantly different among sites. The areas of highest larval abundance varied temporally, indicating that the entire extent of the seagrass bed is utilized. Regression analysis of abiotic environmental factors did not explain why larvae were more abundant at particular sites. To characterize the structure and variability of the fish species assemblage that Red Drum encounter upon settlement, larvae and juveniles were captured in the seagrass meadow during weekly collections. Of the 32 fish species collected, seven represented 92% of the assemblage. Multivariate species analysis indicated that collections widely separated in time and space shared the lowest Bray-Curtis similarity. Because Red Drum settle over a relatively long period and co-occur at body sizes known to cause cannibalism under laboratory conditions, I tested combinations of small and large Red Drum larvae at various field-realistic densities and at different levels of seagrass habitat structure to determine potential for cannibalism. Artificial seagrass did not protect small (5 – 6 mm SL) larvae from cannibalism, but natural dense seagrass had a protective effect relative to edge habitat. The final component of this research examined the emergent impacts of a common predator pinfish (Lagodon rhomboides) on mortality and cannibalistic interactions between small and large Red Drum larvae. Both pinfish and large Red Drum larvae alone readily consumed small Red Drum in all seagrass habitat structures tested. However, the combined treatment of pinfish and large Red Drum together led to reduced mortality of small Red Drum. Predation can significantly affect Red Drum survival during the post-settlement period, and multiple predators may have a protective effect on the smallest settlers if predation pressure is re-directed towards a larger size class.Item Evasion from predation : the perilous life of planktonic copepods throughout development(2011-05) Gemmell, Bradford James; Buskey, Edward Joseph, 1952-; Strickler, J. Rudi; Holt, G. Joan; Lenz, Petra; Shank, G. ChristopherAs one of the most abundant metazoan groups on the planet, copepods are found in virtually all marine environments. They provide a key link in marine food webs between photosynthetic algae and higher trophic levels. Subsequently, copepods are preyed upon by a wide variety of organisms throughout their life history. As a result copepods have evolved a powerful escape behavior at all stages of development, in response to hydrodynamic stimuli created by an approaching predator. Typically copepods exhibit 6 naupliar stages and 5 copepodite stages before becoming adults. This work focuses on quantifying the effectiveness of the escape behavior during key periods of development. The earliest developmental stage of copepod (nauplius N1) experiences the greatest amount of viscous forces and may be at a disadvantage when exposed to larger predators at cold temperatures. The results show that the nauplius exhibits a compensatory mechanism to maximize escape performance across its thermal range. Later in development, the nauplius (N6 stage) molts into a copepodite (C1 stage) which resembles the body form of an adult copepod. Here, there is a significant morphological change with little change in mass. Escape capabilities are investigated for key stages in response to feeding strikes from natural fish predators. The results demonstrate that the improvement in escape capability of the C1 stage is effective only against certain modes of predation. Finally, successfully escaping from predation has evolutionary fitness implications and adults (post C5) are the only reproductive stage. Some species have developed unique mechanisms to avoid predation such as breaking the water surface and making aerial escapes to avoid predators while in other cases, the predator has developed unique morphology in order to reduce the amount of hydrodynamic disturbance in the water which improves capture success of copepods. By investigating copepod behavior and their ability to avoid predation at various stages of development, we can begin to understand which stages copepods are most susceptible to different types of predators and how the escape response changes as development progresses. This can help in understanding localized abundances or deficiencies of both predator and prey in the marine food web.Item Influences of predation risk on mate evaluation and choice in female túngara frogs, Physalaemus pustulosus(2010-05) Bonachea, Luis Alberto; Ryan, Michael J. (Michael Joseph), 1953-; Muller, Ulrich G.; Pianka, Eric R.; Bolnick, Daniel I.; Bell, Chris J.Female choice is an important selective force shaping the evolution of communication and speciation in animals. However, predation risk can impose severe costs on longer searches and choosiness, thereby limiting the expression of female preferences for specific male traits. The work detailed in this dissertation explores how mate choice and sexual selection can be influenced by predation risk in túngara frogs. I begin by examining the effects of multiple simulated cues of predation risk on female search behavior and mate choice, taking a departure from the standard presence/absence paradigm used in similar studies to explore responses to quantitative variation in perceived predation risk. I demonstrate that light, longer travel times, and acoustic cues of predators are all sufficient to sway females away from otherwise more attractive conspecific males. Next, I explore the role of predation risk in altering female permissiveness, or the range of signals females will respond to. Using an artificial series of calls intermediate between heterospecific and conspecific, I demonstrate that predation risk dramatically increases the range of signals females will respond to, including a small number of females choosing pure heterospecific calls. Next I attempt to bridge a logical gap with our understanding of search costs, testing questions about how female search paths change with increasing distance. I demonstrate that females use more direct paths and move faster under higher light conditions, potentially reducing sampling but also reducing encounter rates with predators. Lastly, I examine factors that influence how individual females vary in their response to perceived risk, particularly hormonal state and experience. I demonstrate that naïve, captive-bred females respond to acoustic cues produced by natural predators in a manner similar to wild females and that, while hormonal state is obviously important in determining female receptivity, it has little effect directly on how females respond to predators. Together, these studies demonstrate that predation risk not only changes how females respond to conspecific males, but also increases female permissiveness and constrains search behavior. Predation risk can strongly influence and potentially even negate the expression of female preferences, having profound consequences for communication and the evolution of reproductive isolation between populations.Item Predatory portraiture : Goethe's Faust and the literary vampire in Gogol's [P]opmpem and Wilde's The picture of Dorian Gray(2010-12) Anderson, Matthew Neil, 1983-; Garza, Thomas J.; Richmond-Garza, Elizabeth M.Despite the fact that there seems to be no direct link between the works of Nikolai Gogol and those of Oscar Wilde, Gogol’s novella, Портрет (The Portrait) and Wilde’s novel, The Picture of Dorian Gray, share many elements in common, most notably the device of the predatory portrait. This report explores the parallels that exist between these two texts and argues that they mutually derive from elements found in Goethe’s Faust and the trope of the literary vampire.