Northern Rocky Mountain Science Center (NOROCK)
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Bruce Pugesek's Research Projects
Dr. Pugesek engages in an eclectic mix of research projects, ranging from life history biology of long-lived animals to complex systems analysis of riparian ecosystems. Most of these studies have a common underlying thread of having a longitudinal (i.e. time dependent) component and the statistics of causal and longitudinal data analysis. In addition, Dr. Pugesek frequently consults with other researchers on studies where these statistical methods are used.
Current Projects:
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Title: Life history biology
How long-lived animals allocated reproductive effort throughout their lives is not well understood, in part, due to the difficulty of obtaining data on individuals that may live 30 years or more. However, many species including threatened and endangered species are long-lived and knowledge about demographic parameters, including reproductive rates and mortality patterns, is essential in determining the status and potential growth of their populations. These animals typically display delayed maturation, and low reproductive output during multiple reproductive periods. Reproductive effort is the risks and energy investments incurred by adults in the production of offspring. Therefore, current reproduction has tradeoffs in terms of reduced potential for future reproduction. How individuals allocate reproductive effort across their lifespan to maximize their reproductive potential is crucial to measuring the viability and growth of populations of long-live animals. Research on California gulls is unique in that it measures long term reproductive rates, survival, and reproductive behavior on a large sample of individuals in attempt to measure age-specific variation in reproductive effort and its consequences for population growth.
Research on the endangered Whooping Cranes assesses the relationship between the abundance of a major food source, the blue crab, and the overwintering survival of adults and fledglings. The abundance of blue crabs is heavily impacted by commercial fishing and is potentially threatened by sequestration of freshwater and alteration of salinity in the estuary surrounding the Aransas-Matagorda National Wildlife Refuge where adults and juvenile Whooping Cranes spend the winter months.
Title: Snake River Riparian Study
Although located within a national park, the hydrology of the Snake River in GTNP is partly determined by releases from Jackson Lake Dam. The dam was first built in 1908, before GTNP was established, and only became part of the National Park system when GTNP was expanded to include most of Jackson Hole. However, the Bureau of Reclamation (BOR) manages the dam and sets discharge schedules, primarily to meet agricultural needs, and to a lesser extent the needs of recreational river use. Management of instream flows from Jackson Lake dam has the potential to affect the riparian plant community, wildlife and fisheries and, as a consequence, is a major concern for federal and state managers within GTNP and surrounding lands. Our ongoing research on the Snake River seeks to determine the historical effects of Jackson Lake dam on the ecosystem and whether it is possible or necessary to manage the ecosystem through modification of dam operations.
Structural Equation Modeling
Ecological research frequently involves complex systems with numerous interacting variables. For this reason, multivariate statistics are essential. Structural equation modeling methods (SEM) offer ecologists a way to develop inferential tests of their hypotheses regarding the structure and function of complex systems, causal relationships, and interactions among variables. SEM is an extremely flexible tool that allows investigators to simultaneously analyze continuous and categorical data, non-normal data and non-linear relationships. Of particular interest is developing methods of survival analysis with SEM.
Book: Structural Equation Modeling: Applications in Ecological and Evolutionary Biology.
