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Item Out-migration dynamics of juvenile adfluvial bull trout in tributaries to the lower Clark Fork River, Montana(Montana State University - Bozeman, College of Letters & Science, 2021) Lewis, Madeline Collier; Chairperson, Graduate Committee: Christopher S. Guy; Christopher S. Guy, Eric W. Oldenburg and Thomas E. McMahon were co-authors of the article, 'Demographic characteristics and distribution of juvenile adfluvial bull trout at the tributary scale' submitted to the journal 'Transactions of the American Fisheries Society' which is contained within this thesis.; Christopher S. Guy, Eric W. Oldenburg and Thomas E. McMahon were co-authors of the article, 'Seasonal capture efficiencies influences knowledge of underlying out-migration dynamics in bull trout populations with juvenile downstream trap-and-haul programs' submitted to the journal 'North American journal of fisheries management' which is contained within this thesis.; Christopher S. Guy, Eric W. Oldenburg and Thomas E. McMahon were co-authors of the article, 'Individual characteristics and abiotic factors influence outmigration dynamics of juvenile bull trout' submitted to the journal 'Canadian journal of fisheries and aquatic sciences' which is contained within this thesis.In the lower Clark Fork River, Montana, a two-way trap-and-haul program is implemented to conserve the adfluvial life-history strategy in Bull Trout Salvelinus confluentus populations in the presence of hydropower dams. We used the infrastructure in place for the program, including a permanent weir trap and multiple stationary PIT antennas, to evaluate the demographic characteristics and out-migration dynamics of juvenile bull trout, and assess the efficacy of the downstream trapping component of the trap-and-haul program. We PIT-tagged 821 juvenile Bull Trout in Graves Creek, and 144 Bull Trout in East Fork Bull River in the summer of 2019 and summer of 2020. Bull Trout in Graves Creek were primarily age 1 and age 2, with a small number of age-3 Bull Trout present (< 1%). In East Fork Bull River, age-3 Bull Trout represented 14% - 46% of the population, with a small number of age-4 and older Bull Trout present (4% - 6%). From July 2019 through December 2020, 308 tagged Bull Trout outmigrated from Graves Creek, and most out-migrants were age 2 (n = 221). In East Fork Bull River, 18 Bull Trout out-migrated, and most out-migrants were age 3 (n = 13). Capture efficiency of the permanent weir in Graves Creek varied from 83% to 100% in autumn 2019 and 2020 and was substantially lower in the spring (14%). The majority of Bull Trout out-migrated from Graves Creek during autumn 2019, spring 2020, or autumn 2020 trapping seasons (n = 276). In Graves Creek, the largest Bull Trout within the 2018 year-class were five times more likely to out-migrate at age 1 when compared to smaller fish within the cohort. The magnitude of age-1 out-migration was positively related to density. Relative changes in abiotic factors, including discharge, water temperature, and photoperiod, were cues to out-migration, and the direction of change varied by season. Understanding the demographic characteristics and outmigration dynamics of the Bull Trout in Graves Creek and East Fork Bull River enables more informed management of the trap-and-haul program and can be used to inform conservation efforts of other migratory Bull Trout populations.Item Investigating diverse sources of variation in the amount of time Weddell seal (Leptonychotes weddellii) pups spend in the water during the lactation period(Montana State University - Bozeman, College of Letters & Science, 2020) Petch, Shane Morgan; Chairperson, Graduate Committee: Jay J. RotellaThe early-developmental period can have important consequences for offspring success later in life. Phenotypic differences among parents and offspring influence energy availability as well as patterns of allocation and trade-offs during development. Variation in behavioral development prior to weaning may be an important determinant of post-weaning success. Here, we use hierarchical Bayesian models and a long-term database of phenotypic characteristics to investigate sources of variation in total time spent in the water and age at first entry in Weddell seal pups from 11-30 days of age. We found that time in the water was greater for pups with higher birth mass, greater for female than for male pups, lower for pups first entering the water at older ages, had a quadratic relationship with maternal age that peaked at intermediate maternal ages, and was higher for pups born to mothers who skipped reproduction the previous year than those born to mothers that were pre-breeders or reproduced the previous year. Some mothers consistently gave birth to pups that spent more time in the water. Age at first entry was earliest for pups with higher birth mass born to mothers with above average reproductive experience. Maternal identity accounted for slight variation in age at first entry. We document that the first entry can occur as early as 4 days old, but on average occurs at age 14 days. Pups born heavier may have more stored energy to allocate to activity or mitigate costs of submergence. Male pups may spend less time in the water to compensate for higher developmental costs. We found support for proxies of maternal body condition but not maternal behavior in describing time in the water, although maternal reproductive experience was supported in our analysis of age at first entry. Our results indicate that some variation in time spent in the water can be explained by the phenotypic characteristics of mothers and pups, though unaccounted-for sources of variation could be involved. It would be useful if future studies would investigate additional sources of variation and seek to understand how time spent in the water is related to post-weaning outcomes.Item Experimental induction of territorial behavior in the deer mouse, Peromyscus maniclatus(Montana State University - Bozeman, College of Agriculture, 1969) Salonen, James JohnItem Movements and homing of cutthroat trout (Salmo clarki) from open-water areas of Yellowstone Lake(Montana State University - Bozeman, College of Agriculture, 1968) Jahn, Lawrence AllanItem Female Weddell seals show flexible strategies of colony attendance related to varying environmental conditions(2015-02) Rotella, Jay J.; Chambert, T. C.; Garrott, Robert A.Many animal life cycles involve movements among different habitats to fulfill varying resource demands. There are inherent costs associated with such movements, and the decision to leave or stay at a given location ought to be motivated by the benefits associated with potential target habitats. Because movement patterns, especially those associated with reproduction, can have important implications for the success (survival, reproduction) of individual animals, and therefore a population's dynamics, it is important to identify and understand their sources of variation (environmental and individual). Here, using a mark–recapture, multistate modeling approach, we investigated a set of a priori hypotheses regarding sources and patterns of variation in breeding-colony attendance for Weddell seal (Leptonychotes weddellii) females on sabbatical from pup production. For such females, colony attendance might be motivated by predation avoidance and positive social interactions related to reproduction, but some costs, such as reduced foraging opportunities or aggressive interactions with conspecifics, might also exist. We expected these benefits and costs to vary with a female's condition and the environment. Results revealed that the probability of being absent from colonies was higher (1) in years when the extent of local sea ice was larger, (2) for the youngest and oldest individuals, and (3) for females with less reproductive experience. We also found substantial levels of residual individual heterogeneity in these rates. Based on our a priori predictions, we postulate that the decision to attend breeding colonies or not is directly influenced by an individual's physiological condition, as well as by the ice-covered distance to good foraging areas, availability of predator-free haul-out sites, and the level of negative interactions with conspecifics inside colonies. Our results support the idea that in iteroparous species, and colonial animals in particular, seasonal and temporary movements from/to reproductive sites represent flexible behavioral strategies that can play an important role in coping with environmental variability.Item Toward a predictive theory of risk effects: hypotheses for prey attributes and compensatory mortality(2011-12) Creel, ScottRisk effects, or the costs of antipredator behavior, can comprise a large proportion of the total effect of predators on their prey. While empirical studies are accumulating to demonstrate the importance of risk effects, there is no general theory that predicts the relative importance of risk effects and direct predation. Working toward this general theory, it has been shown that functional traits of predators (e.g., hunting modes) help to predict the importance of risk effects for ecosystem function. Here, I note that attributes of the predator, the prey, and the environment are all important in determining the strength of antipredator responses, and I develop hypotheses for the ways that prey functional traits might influence the magnitude of risk effects. In particular, I consider the following attributes of prey: group size and dilution of direct predation risk, the degree of foraging specialization, body mass, and the degree to which direct predation is additive vs. compensatory. Strong tests of these hypotheses will require continued development of methods to identify and quantify the fitness costs of antipredator responses in wild populations.Item Inferential consequences of modeling rather than measuring snow accumulation in studies of animal ecology(2013-04)It is increasingly common for studies of animal ecology to use model-based predictions of environmental variables as explanatory or predictor variables, even though model prediction uncertainty is typically unknown. To demonstrate the potential for misleading inferences when model predictions with error are used in place of direct measurements, we compared snow water equivalent (SWE) and snow depth as predicted by the Snow Data Assimilation System (SNODAS) to field measurements of SWE and snow depth. We examined locations on elk (Cervus canadensis) winter ranges in western Wyoming, because modeled data such as SNODAS output are often used for inferences on elk ecology. Overall, SNODAS predictions tended to overestimate field measurements, prediction uncertainty was high, and the difference between SNODAS predictions and field measurements was greater in snow shadows for both snow variables compared to non-snow shadow areas. We used a simple simulation of snow effects on the probability of an elk being killed by a predator to show that, if SNODAS prediction uncertainty was ignored, we might have mistakenly concluded that SWE was not an important factor in where elk were killed in predatory attacks during the winter. In this simulation, we were interested in the effects of snow at finer scales (<1 km2) than the resolution of SNODAS. If bias were to decrease when SNODAS predictions are averaged over coarser scales, SNODAS would be applicable to population-level ecology studies. In our study, however, averaging predictions over moderate to broad spatial scales (9–2200 km2) did not reduce the differences between SNODAS predictions and field measurements. This study highlights the need to carefully evaluate two issues when using model output as an explanatory variable in subsequent analysis: (1) the model's resolution relative to the scale of the ecological question of interest and (2) the implications of prediction uncertainty on inferences when using model predictions as explanatory or predictor variables.Item Underestimating the frequency, strength and cost of anti-predator responses with data from GPS collars: an example with wolves and elk.(2013-11) Creel, Scott; Winnie, John A. Jr.; Christianson, David A.Field studies that rely on fixes from GPS-collared predators to identify encounters with prey will often underestimate the frequency and strength of antipredator responses. These underestimation biases have several mechanistic causes. (1) Step bias: The distance between successive GPS fixes can be large, and encounters that occur during these intervals go undetected. This bias will generally be strongest for cursorial hunters that can rapidly cover large distances (e.g., wolves and African wild dogs) and when the interval between GPS fixes is long relative to the duration of a hunt. Step bias is amplified as the path travelled between successive GPS fixes deviates from a straight line. (2) Scatter bias: Only a small fraction of the predators in a population typically carry GPS collars, and prey encounters with uncollared predators go undetected unless a collared group-mate is present. This bias will generally be stronger for fission–fusion hunters (e.g., spotted hyenas, wolves, and lions) than for highly cohesive hunters (e.g., African wild dogs), particularly when their group sizes are large. Step bias and scatter bias both cause underestimation of the frequency of antipredator responses. (3) Strength bias: Observations of prey in the absence of GPS fix from a collared predator will generally include a mixture of cases in which predators were truly absent and cases in which predators were present but not detected, which causes underestimation of the strength of antipredator responses. We quantified these biases with data from wolves and African wild dogs and found that fixes from GPS collars at 3-h intervals underestimated the frequency and strength of antipredator responses by a factor >10. We reexamined the results of a recent study of the nonconsumptive effects of wolves on elk in lItem Ecosystem scale declines in elk recruitment and population growth with wolf colonization: a before-after-control-impact approach(2014-07) Christianson, David A.; Creel, ScottThe reintroduction of wolves (Canis lupus) to Yellowstone provided the unusual opportunity for a quasi-experimental test of the effects of wolf predation on their primary prey (elk – Cervus elaphus) in a system where top-down, bottom-up, and abiotic forces on prey population dynamics were closely and consistently monitored before and after reintroduction. Here, we examined data from 33 years for 12 elk population segments spread across southwestern Montana and northwestern Wyoming in a large scale before-after-control-impact analysis of the effects of wolves on elk recruitment and population dynamics. Recruitment, as measured by the midwinter juvenile:female ratio, was a strong determinant of elk dynamics, and declined by 35% in elk herds colonized by wolves as annual population growth shifted from increasing to decreasing. Negative effects of population density and winter severity on recruitment, long recognized as important for elk dynamics, were detected in uncolonized elk herds and in wolf-colonized elk herds prior to wolf colonization, but not after wolf colonization. Growing season precipitation and harvest had no detectable effect on recruitment in either wolf treatment or colonization period, although harvest rates of juveniles:females declined by 37% in wolf-colonized herds. Even if it is assumed that mortality due to predation is completely additive, liberal estimates of wolf predation rates on juvenile elk could explain no more than 52% of the total decline in juvenile:female ratios in wolf-colonized herds, after accounting for the effects of other limiting factors. Collectively, these long-term, large-scale patterns align well with prior studies that have reported substantial decrease in elk numbers immediately after wolf recolonization, relatively weak additive effects of direct wolf predation on elk survival, and decreased reproduction and recruitment with exposure to predation risk from wolves.Item Female elk contacts are neither frequency nor density dependent(2013-09) Cross, Paul C.; Creech, Tyler G.; Ebinger, Michael R.; Manlove, Kezia R.; Irvine, K.; Henningsen, J.; Rogerson, J.; Scurlock, Brandon M.; Creel, ScottIdentifying drivers of contact rates among individuals is critical to understanding disease dynamics and implementing targeted control measures. We studied the interaction patterns of 149 female elk (Cervus canadensis) distributed across five different regions of western Wyoming over three years, defining a contact as an approach within one body length (∼2 m). Using hierarchical models that account for correlations within individuals, pairs, and groups, we found that pairwise contact rates within a group declined by a factor of three as group sizes increased 33-fold. Per capita contact rates, however, increased with group size according to a power function, such that female elk contact rates fell in between the predictions of density- or frequency-dependent disease models. We found similar patterns for the duration of contacts. Our results suggest that larger elk groups are likely to play a disproportionate role in the disease dynamics of directly transmitted infections in elk. Supplemental feeding of elk had a limited impact on pairwise interaction rates and durations, but per capita rates were more than two times higher on feeding grounds. Our statistical approach decomposes the variation in contact rate into individual, dyadic, and environmental effects, and provides insight into factors that may be targeted by disease control programs. In particular, female elk contact patterns were driven more by environmental factors such as group size than by either individual or dyad effects.