Browsing by Subject "Habitat selection"
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Item Predictors and benefits of microhabitat selection for offspring deposition in golden rocket frogs(2018-04-02) Pettitt, Beth A; Bourne, Godfrey R; Bee, Mark A; mbee@umn.edu; Bee, Mark AThis data set originates from a field study of habitat selection by parental frogs. In many tropical frogs, offspring development and survival potentially depend on microhabitat features associated with sites that parents select for oviposition and tadpole rearing. This study investigated the importance of microhabitat features in the selection of oviposition sites versus tadpole rearing sites, as well as in determining offspring survival, in the golden rocket frog, Anomaloglossus beebei. Endemic to Guyana, this species exhibits biparental care and exclusively uses phytotelmata in bromeliads for oviposition and tadpole rearing. The data included here were used in model based inference to evaluate evidence for the hypotheses that (1) parents prioritize different microhabitat features in selecting phytotelmata suitable for oviposition versus tadpole rearing and (2) microhabitat selection can adaptively promote offspring survival. The dataset includes descriptions of bromeliad size, phytotelm height, leaf angle (indicative of location within the bromeliad), water volume, water temperature, dissolved oxygen concentration, and the presence/absence of potential predators and nearby conspecifics. Compared to tadpole rearing sites, the data show that oviposition sites were found in phytotelmata associated with leaves at lower angles within bromeliads and that had smaller water volumes, lower water temperatures, higher dissolved oxygen concentrations, and more crabs. Compared with unsuccessful egg clutches, successful clutches were found in phytotelmata with lower water temperatures, higher dissolved oxygen concentrations, fewer crabs, more dragonfly larvae, and more nearby conspecifics. These data indicate that non-random patterns of microhabitat use for oviposition sites and tadpole rearing sites in golden rocket frogs are associated with specific environmental factors that promote offspring survival through a critical stage of the animals’ complex life cycle.Item Relationships among behavior, habitat, and population density in a cyclic population of ruffed grouse(2014-10) Berkeley, Lorelle IvanaUnderstanding how patterns of habitat use by animals vary in relation to population density is of major interest to ecologists and wildlife managers. For decades, biologists have linked high populations of ruffed grouse (Bonasa umbellus) with aspen (Populus spp.) forests in the northern part of their range. However, male ruffed grouse in northern populations also select territories in conifer forests, even when apparently suitable aspen forests nearby remain vacant. This selection of cover types that are presumed to be of lower quality presents a conundrum to biologists: why would males select inferior cover types when better cover types are available? To address this conundrum, I investigated the behavior, habitat, and population dynamics of a population of male ruffed grouse to evaluate relationships among these factors and elucidate mechanisms of their cover type selections. Little is known about the mechanisms underlying habitat selection in most species. Studying the behavior of individuals within a population is one technique used to evaluate these mechanisms. Ruffed grouse are an ideal species in which to study behavior, habitat, and population dynamics because the males are easily counted, they are territorial, their territories are relatively easy to locate, and many populations are cyclic. I conducted my study at the Cloquet Forestry Center in northern Minnesota and used data collected over the course of one complete 10-year ruffed grouse population cycle (2002-2011) during which time the population reached both a high and low point in the numbers of territorial males counted each year. The grouse population was declining when the study begin in 2002 and did not begin its cyclic increase until 2006. I used repeated auditory surveys to locate the territories of drumming males and estimate the population density of territorial male grouse. I assessed behavior questions by using automated video systems to record the activities of a stratified (by aspen and conifer cover types) random sample of 23 male ruffed grouse from all of the males detected on my surveys. The number of breeding males on my 1,419-ha study area varied from a low of 47 in 2005 to a high of 134 in 2010. I assumed that rates of male ruffed grouse display were indicative of their interactions with conspecifics. I developed a priori models that described the relationships among male display rates and environmental attributes, structured these models as generalized linear models, and used information theoretic model selection to evaluate these models. The null model (i.e., intercept only model) was the top-ranked model (received the lowest AICc score). I used generalized linear models with random effects and information theoretic model selection to evaluate a priori models that described relationships among male ruffed grouse densities per cover type and environmental variables associated with their territory locations. Aspen-dominated cover types contained the highest densities of male ruffed grouse during all years (0.09 to 0.24 males/ha during 2002-11) except 2006 and 2011, when density was highest in northern hardwoods-dominated cover types (0.12 and 0.13 males/ha in 2006 and 2011, respectively) followed by aspen-dominated cover types (0.10 and 0.12 males/ha in 2006 and 2011, respectively). The density of males in conifer-dominated cover types was always less than the density of males in aspen-dominated cover types (0.02 to 0.08 males/ha during 2002-11). In addition to consistently higher densities of males in aspen- versus conifer-dominated cover types, densities of males in aspen-dominated cover types exhibited a higher intrinsic rate of increase than in conifer-dominated cover types during all years. However, the consistent occupancy of conifer-dominated cover types by males throughout the study also suggested that males perceived conifer-dominated cover types as suitable sites for territories and display behavior. At the cover type scale, the top-ranked model related to male grouse population density included an interaction of cover type and year variables. The mean density of male ruffed grouse within landscapes during all years ranged from 0.04 to 0.10 males/ha with minimum and maximum densities of 0 and 0.16 males/ha, respectively, during the entire study. At this landscape scale, an interaction of the estimate of the relative evenness of cover types (Shannon's Evenness Index) within landscapes and year comprised the top-ranked model explaining male ruffed grouse densities. Based on my study, if there is a difference in quality of conifer and aspen cover types, it manifests itself either in the specific stand structure used for male breeding displays or some life stage or seasonal habitat need of the ruffed grouse other than male breeding display cover. My results show that grouse populations achieve their highest densities in heterogeneous landscapes when aspen-dominated cover types, composed of multiple age classes, are the key cover types on landscapes. Landscapes that are less heterogeneous and where the majority of cover types are not dominated by aspen also harbor grouse, but at lower densities than heterogeneous aspen-dominated landscapes. Traditionally, managers have focused on the distribution and abundance of aspen-dominated cover types to enhance ruffed grouse habitat. However, my findings suggest that managers should focus on managing the spatial complexity of cover types on landscapes, even when aspen-dominated stands are in low abundance.Item Space use behavior and multi-scale habitat selection of American marten (Martes americana) in northeastern Minnesota(2013-10) Joyce, Michael JamesTrack counts and anecdotal reports indicate that the American marten population in Minnesota has declined over the past 10 years. We deployed radiocollars on 170 marten from 2008-2012 and used location data to describe space use behavior, estimate home range size, and assess habitat selection at landscape and stand scales. Marten selected mature forest, but individual marten showed preference for different forest cover types. Rest sites and reproductive dens facilitate recruitment and protect marten from predators and inclement weather during periods of inactivity. We located 200 rest sites and 31 reproductive dens and measured vegetative characteristics at 31 reproductive dens, 62 rest sites, and 102 random sites. Marten selected dens and rest sites in mature, structurally complex forest stands. Collectively, our results suggest that forest management practices aimed at supporting marten populations should retain stands of mature, structurally complex forest to maintain suitable habitat across the landscape.Item Survival In A Landscape Of Fear: Prey Behavioral Responses To Predation Risk That Varies In Time And Space(2018-03) Palmer, MeredithThe fear of predation is a driving force shaping prey behavior and ecology. The “landscape of fear” hypothesis posits that prey perceive their environment in terms of peaks and valleys of predation risk; the behavioral decisions prey make as they navigate this “landscape” reflect a fitness tradeoff between minimizing risk and obtaining sufficient resources. While landscapes of fear have been well-examined in small-scale experimental systems, logistical challenges have greatly prohibited their study in communities of large vertebrates which inhabit vast spatial expanses. In a novel investigation of an unparalleled long-term camera trap dataset, I examined the behavioral tactics used by guilds of mammalian herbivores to navigate a risk-resource tradeoff in a natural savanna ecosystem. By studying the choice and scale of anti-predator behaviors elicited in response to multidimensional predation risk from an apex predator, the African lion (Panthera leo), I sought to derive overarching mechanisms which structure communities across different spatial and temporal scales. First, I determined the spatial mechanisms structuring the landscape of fear by quantifying anti-predator behaviors elicited in response to different components of the predation process (i.e., the risk of encountering predators vs. the risk of being killed given an encounter). I then incorporated predictable temporal variations in predation threat, assessing whether prey perceive heterogeneity in risk across time as well as space. For this, I tested whether prey changed their behaviors in response to diel fluctuations in lion activity patterns or monthly nocturnal variation in lion hunting success driven by changes in night-time luminosity. Finally, I evaluated immediate responses to cues of imminent predation risk within herbivore communities. I characterized the types of anti-predator behaviors used to mitigate risk across each spatiotemporal scale and examined how choice of anti-predator behavior changed across resource gradients in order to understand the costs and benefits associated with different suites of behavioral decisions. My work suggests that prey minimize dynamic variation in predation risk by exhibiting a variety of complementary and compensatory behaviors across spatiotemporal scales. This type of complexity is frequently suggested but rarely tested, and directly informs our ability to predict predator-mediated impacts on community structure and ecosystem functioning.