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Craig Stricker, Ph.D.

Craig Stricker is a Research Biologist at the Fort Collins Science Center. 

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Fort Collins Science Center

Fort Collins Science Center Labs and Facilities

The Fort Collins Science Center has scientists working in several diverse locations as well as three in house highly specialized laboratories, studying subjects from molecular ecology to brown treesnakes, dendroecology to streamflows, and macroinvertebrate species to Burmese pythons. Our extraordinary scientists work in each of these locations advancing studies in their particluar areas of study...
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Ecosystems Mission Area, Biological Threats and Invasive Species Research Program, Fort Collins Science Center
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Fort Collins Science Center Labs and Facilities

The Fort Collins Science Center has scientists working in several diverse locations as well as three in house highly specialized laboratories, studying subjects from molecular ecology to brown treesnakes, dendroecology to streamflows, and macroinvertebrate species to Burmese pythons. Our extraordinary scientists work in each of these locations advancing studies in their particluar areas of study...
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Two scientists work on a study of mercury contamination in the water.

Contaminant Biology: Stable Isotope Applications

Environmental contaminants of natural and anthropogenic origin represent a major stressor to ecosystems, including human and wildlife populations.
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Fort Collins Science Center
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Contaminant Biology: Stable Isotope Applications

Environmental contaminants of natural and anthropogenic origin represent a major stressor to ecosystems, including human and wildlife populations.
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Seemingly Surreal Swallows in a Spring Snowstorm, by Keith Williams.

Biogeography: Stable Isotope Applications

The distribution of species across the landscape is of great interest to conservation biology. Habitat quality and quantity are thought to be important drivers of occurrence and distribution, and numerous studies have demonstrated fitness-related consequences. However, for species with cryptic or migratory life histories, we often lack sufficient detail about habitat usage and in many cases...
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Fort Collins Science Center
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Biogeography: Stable Isotope Applications

The distribution of species across the landscape is of great interest to conservation biology. Habitat quality and quantity are thought to be important drivers of occurrence and distribution, and numerous studies have demonstrated fitness-related consequences. However, for species with cryptic or migratory life histories, we often lack sufficient detail about habitat usage and in many cases...
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Waterfall in Appalachian Forest

Biogeochemistry: Stable Isotope Applications

Biogeochemical cycling is a cornerstone of ecosystem function and structure. Much has been learned about element cycles in a variety of systems using standard geochemical techniques.
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Fort Collins Science Center
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Biogeochemistry: Stable Isotope Applications

Biogeochemical cycling is a cornerstone of ecosystem function and structure. Much has been learned about element cycles in a variety of systems using standard geochemical techniques.
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The sunset on the main city beach in Laguna Beach, CA.

Ecological Applications of Stable Isotopes

Environmental contaminants of natural and anthropogenic origin represent a major stressor to ecosystems, including human and wildlife populations. FORT scientists are studying these stressors in order to understand the contaminant cycling under natural environmental conditions. Stable isotope techniques are extremely useful in resolving trophic pathways by which contaminants become bioavailable...
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Land Management Research Program, Fort Collins Science Center
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Ecological Applications of Stable Isotopes

Environmental contaminants of natural and anthropogenic origin represent a major stressor to ecosystems, including human and wildlife populations. FORT scientists are studying these stressors in order to understand the contaminant cycling under natural environmental conditions. Stable isotope techniques are extremely useful in resolving trophic pathways by which contaminants become bioavailable...
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A polar bear in a pool.

Foraging Ecology Using Stable Isotopes

Understanding species habitat requirements is incomplete without insight into nutrition, including various aspects of foraging ecology. Traditional diet studies can be challenging because of logistics, issues related to resource availability, and observations are often short-term in nature based on gut contents or scat. Additionally, perturbations such as species introductions, habitat degradation...
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Land Management Research Program, Species Management Research Program, Fort Collins Science Center
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Foraging Ecology Using Stable Isotopes

Understanding species habitat requirements is incomplete without insight into nutrition, including various aspects of foraging ecology. Traditional diet studies can be challenging because of logistics, issues related to resource availability, and observations are often short-term in nature based on gut contents or scat. Additionally, perturbations such as species introductions, habitat degradation...
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Filter Total Items: 13

Total mercury, methylmercury, and isotopic composition in various life stages of boreal chorus frogs (Pseudacris maculata) at two subalpine ponds in the Rocky Mountains, CO, USA, 2015

Mercury is an atmospherically transported contaminant found even in relatively pristine habitats. Once accumulated at the base of the food web, mercury can move between animals that are linked trophically. Pond-breeding amphibians may be particularly important vectors of mercury flux from remote freshwater to terrestrial systems because they feed on algae and detritus as tadpoles and metamorphose
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Columbia Environmental Research Center

Mercury concentrations, isotopic composition, biomass, and taxonomy of stream and riparian organisms in the vicinity of Yellow Pine, Idaho, 2015-2016.

This data release includes sampling location data; field-collected stream attribute data; laboratory-analyzed chemistry concentrations (total mercury, methyl mercury) and isotopic composition (total mercury, carbon, and nitrogen) for stream biota (seston, periphyton, benthic insects, emerging adult insects, riparian spiders, and fish); density, body length, and taxonomic information for benthic in
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Mineral Resources Program, Columbia Environmental Research Center, Geology, Geophysics, and Geochemistry Science Center

Dataset for temporal influences on selenium partitioning, trophic transfer, and exposure in a major U.S. river

The trace element selenium is an essential element with a narrow window between concentrations needed to support life and those that cause toxicity to egg laying organisms. Selenium bioaccumulation in aquatic organisms is primarily the result of trophic transfer through food webs and is poorly predicted by dissolved concentrations in freshwater bodies. To better understand the hydrologic and biolo
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Wyoming-Montana Water Science Center

Chemistry of water, stream sediment, wildfire ash, soil, dust, and mine waste for Fourmile Creek Watershed, Colorado, 2010-2019

In response to the 2010 Fourmile Canyon fire near Boulder, Colorado, the U.S. Geological Survey collected data to support investigations into the magnitude and critical drivers of water-quality impairment after wildfire. We analyzed chemistry of stream water, sediment, wildfire ash, soil, dust, and mine waste for metals and other parameters in order to evaluate the effects of legacy mining and wil
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Water Resources Mission Area

Radiogenic strontium isotope data for non-native walleye otoliths collected from select areas of the Upper Colorado River Basin

This dataset includes radiogenic strontium isotope compositions of non-native walleye otoliths collected from select areas of the Upper Colorado River Basin (UCRB). Strontium isotope data have been widely used to assess natal areas for a variety of fish species. Following on previous work, this project sought to fill data gaps for walleye collected from the Colorado River (river miles 11-109.3), t
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Fort Collins Science Center

Stable carbon isotope and wood component concentration data for riparian cottonwood tree rings, Little Missouri River, North Dakota

This dataset includes stable carbon isotope values, lignin, cellulose, and hemicellulose concentrations (expressed as percent of ash-free dry mass) for riparian cottonwood (Populus deltoides) tree rings growing on the Little Missouri River floodplain, Theodore Roosevelt National Park, North Dakota. Drought stress induces stomatal closure and the carbon isotope ratio of annual tree rings tends to
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Fort Collins Science Center

Stable carbon and nitrogen isotope data for Siberian barn swallow subspecies collected during the breeding season

This dataset includes stable carbon and nitrogen isotope values for the inner tail retrices of three subspecies of barn swallow (Hirundo rustica rustica, H. r. tytleri, and H. r. gutturalis). Sampling was conducted in Russia (summer 2013), China (summer 2014), Mongolia (summer 2014), Japan (summer 2014), and western China (summer 2015) using mist nets. Stable carbon and nitrogen isotope data are u
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Fort Collins Science Center

Ovary mass and stable hydrogen isotope data for resident and migratory female dark-eyed juncos

This dataset includes ovary mass and stable hydrogen isotope compositions of feathers and claws from resident and migratory female dark-eyed juncos (Junco hyemalis) collected during early spring at Mountain Lake Biological Station, Pembroke, Virginia. A total of 18 migrant and 15 resident female dark-eyed juncos, a songbird that exhibits seasonal sympatry, were caught during March-April. Stable hy
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Fort Collins Science Center

Lignin phenol data for solid phase peat cores collected from the Alligator River and Great Dismal Swamp National Wildlife Refuges

This dataset includes lignin phenol monomer concentrations normalized to 100 mg of organic carbon. These analyses were conducted on select intervals from peat cores collected at the Alligator River (AR) and Great Dismal Swamp (GDS) National Wildlife Refuges in North Carolina and Virginia/North Carolina, USA, respectively. The eight lignin phenol monomers provide unique proxy information on the sou
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Fort Collins Science Center

Stable carbon and nitrogen isotope data for: 'Ecotoxicoparasitology of the gastrointestinal tracts of pinnipeds: effect of parasites on bioavailability of total mercury (THg)'

Parasites, such as acanthocephalans, cestodes, and some species of nematodes acquire nutrients from the lumen contents within the host gastrointestinal (GI) tract. For ubiquitous toxicants like mercury, both the host species and parasites are potentially exposed. The focus of this study was to determine if there is an effect of parasites on the dietary availability and therefore exposure to mercur
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Fort Collins Science Center

Data for Biogeochemical and Physical Processes Controlling Mercury and Selenium Bioaccumulation in Bighorn Lake, Bighorn Canyon National Recreation Area, Montana and Wyoming, 2015-2016

This dataset includes the field measurements and laboratory analyses of surface water, seston, fish tissue, and sediment samples collected from Bighorn Lake, within Bighorn Canyon National Recreation area (BICA), during high flow (July 2015) and low flow (August 2016) conditions. The study area includes 7-9 sampling sites that follow a transect spanning the entire length of the reservoir from the
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Upper Midwest Water Science Center, Wyoming-Montana Water Science Center, Mercury Research Laboratory

Hydrogen stable isotope data for: 'Mechanisms associated with an advance in the timing of seasonal reproduction in an urban songbird'.

This dataset includes stable hydrogen isotope values of the nonexchangeable hydrogen contained in the outer most secondary feathers of dark-eyed juncos (Junco hyemalis thurberi) collected from the University of California San Diego campus in La Jolla, California in 2014. Hydrogen isotope values in feathers have become a powerful tool for inferring the breeding grounds of a wide variety of avian sp
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Fort Collins Science Center
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Filter Total Items: 80

Diet energy density estimated from isotopes in predator hair associated with survival, habitat, and population dynamics

Sea ice loss is fundamentally altering the Arctic marine environment. Yet there is a paucity of data on the adaptability of food webs to ecosystem change, including predator-prey interactions. Polar bears (Ursus maritimus) are an important subsistence resource for Indigenous people and an apex predator that relies entirely on the under-ice food web to meet their energy needs. Here, we assessed whe
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Karyn D. Rode, Brian D. Taras, Craig A. Stricker, Todd C. Atwood, Nicole P Boucher, George M. Durner, Andrew E. Derocher, Evan S. Richardson, Seth Cherry, Lori T. Quakenbush, Lara Horstmann, Jeffrey F. Bromaghin
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Ecosystems Mission Area, Alaska Science Center, Fort Collins Science Center

Summer/fall diet and macronutrient assimilation in an Arctic predator

Free-ranging predator diet estimation is commonly achieved by applying molecular-based tracers because direct observation is not logistically feasible or robust. However, tracers typically do not represent all dietary macronutrients, which likely obscures resource use as prey proximate composition varies and tissue consumption can be specific. For example, polar bears (Ursus maritimus) preferentia
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Craig A. Stricker, Karyn D. Rode, Brian D. Taras, Jeffrey F. Bromaghin, Lara Horstmann, Lori T. Quakenbush
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Ecosystems Mission Area, Alaska Science Center, Fort Collins Science Center

Increased mercury and reduced insect diversity in linked stream-riparian food webs downstream of a historical mercury mine

Historical mining left a legacy of abandoned mines and waste rock in remote headwaters of major river systems in the western United States. Understanding the influence of these legacy mines on culturally and ecological important downstream ecosystems is not always straight-forward because of elevated natural levels of mineralization in mining-impacted watersheds. To test the ecological effects of
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Johanna M. Kraus, JoAnn Holloway, Michael Pribil, Ben N. Mcgee, Craig A. Stricker, Danny Rutherford, Andrew S. Todd
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Ecosystems Mission Area, Columbia Environmental Research Center

The reuse of avian samples: Opportunities, pitfalls and a solution

Tissue samples are frequently collected to study various aspects of avian biology, but in many cases these samples are not used in their entirety and are stored by the collector. The already collected samples provide a largely overlooked opportunity because they can be used by different researchers in different biological fields. Broad reuse of samples could result in multispecies or large-scale s
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Vojtěch Brlík, Pavel Pipek, Kate Brandis, Nikita Chernetsov, Fábio J. V. Costa, L. Gerardo Herrera M., Yosef Kiat, Richard B. Lanctot, Peter P. Marra, D. Ryan Norris, Chima J. Nwaogu, Petra Quillfeldt, Sarah T. Saalfeld, Craig A. Stricker, Robert L. Thomson, Tianhao Zhao, Petr Procházka
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Ecosystems Mission Area, Fort Collins Science Center

Energetic and health effects of protein overconsumption constrain dietary adaptation in an apex predator

Studies of predator feeding ecology commonly focus on energy intake. However, captive predators have been documented to selectively feed to optimize macronutrient intake. As many apex predators experience environmental changes that affect prey availability, limitations on selective feeding can affect energetics and health. We estimated the protein:fat ratio of diets consumed by wild polar bears us
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Karyn D. Rode, Charles T. Robbins, Craig A. Stricker, Brian D. Taras, Troy N Tollefson
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Ecosystems Mission Area, Alaska Science Center, Fort Collins Science Center

Juvenile Coho and Chinook salmon growth, size, and condition linked to watershed-scale salmon spawner abundance

Anadromous Pacific salmon Oncorhynchus spp. are semelparous, and resource subsidies from spawning adult salmon (marine-derived nutrients [MDN]) benefit juvenile salmonids while they rear in freshwater. However, it is unclear if juvenile salmon populations respond predictably to the abundance of spawning salmon at the watershed scale. To address whether hypothesized benefits to rearing juveniles sc
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Philip J. Joy, Craig A. Stricker, Renae Ivanoff, Shiao Y. Wang, Mark S. Wipfli, Andrew C. Seitz, Jiaqi Huang, Mathew B. Tyers
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Ecosystems Mission Area, Cooperative Research Units, Fort Collins Science Center

Temporal influences on selenium partitioning, trophic transfer, and exposure in a major U.S. river

Hydrologic and irrigation regimes mediate the timing of selenium (Se) mobilization to rivers, but the extent to which patterns in Se uptake and trophic transfer through recipient food webs reflect the temporal variation in Se delivery is unknown. We investigated Se mobilization, partitioning, and trophic transfer along approximately 60 river miles of the selenium-impaired segment of the Lower Gunn
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Jessica E Brandt, James Roberts, Craig A. Stricker, Holly Rogers, Patricia Nease, Travis S. Schmidt
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Ecosystems Mission Area, Water Resources Mission Area, Fort Collins Science Center, Great Lakes Science Center, Wyoming-Montana Water Science Center

Breeding at higher latitude is associated with higher photoperiodic threshold and delayed reproductive development in a songbird

Many seasonally breeding animals exhibit a threshold day length (critical photoperiod; CPP) for gonadal growth, and populations breeding at higher latitudes typically have a higher CPP. Much less is known about latitudinal variation in CPP in migratory population that winter away from their breeding range and must time their reproduction to match favorable conditions at their destination. To addre
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Devraj Singh, S. M. Reed, A. A. Kimmitt, K. A. Alford, Craig A. Stricker, P. D. Polly, Ellen D. Ketterson
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Ecosystems Mission Area, Fort Collins Science Center

Evidence of post-breeding prospecting in a long-distance migrant.

Organisms assess biotic and abiotic cues at multiple sites when deciding where to settle. However, due to temporal constraints on this prospecting, the suitability of available habitat may be difficult for an individual to assess when cues are most reliable, or at the time they are making settlement decisions. For migratory birds, the postbreeding season may be the optimal time to prospect and inf
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Max Ciaglo, Ross Calhoun, Scott W Yanco, Michael B. Wunder, Craig A. Stricker, Brian D Linkhart
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Ecosystems Mission Area, Fort Collins Science Center

Short- and long-term responses of riparian cottonwoods (Populus spp.) to flow diversion: Analysis of tree-ring radial growth and stable carbon isotopes

Long duration tree-ring records with annual precision allow for the reconstruction of past growing conditions. Investigations limited to the most common tree-ring proxy of ring width can be difficult to interpret, however, because radial growth is affected by multiple environmental processes. Furthermore, studies of living trees may miss important effects of drought on tree survival and forest cha
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Derek M. Schook, Jonathan M. Friedman, Craig A. Stricker, Adam Z. Csank, David J. Cooper
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Ecosystems Mission Area, Fort Collins Science Center

A new chamber design for measuring community metabolism in a Michigan stream

We designed an open-ended community metabolism chamber to simultaneously measure surface and hyporheic metabolism. Our chamber design eliminated reaeration, compartmentalized metabolism, maintained ambient conditions and included hyporheic respiration. We compared results from our hyporheic chamber to results obtained from: (1) closed benthic community metabolism chambers constructed as recommende
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D.G. Uzarski, T.M. Burton, Craig A. Stricker
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Ecosystems Mission Area, Fort Collins Science Center

Development of a preliminary invertebrate index of biotic integrity for Lake Huron coastal wetlands

The biota of aquatic systems are integrators of overall habitat quality, revealing both episodic as well as cumulative disturbance, and therefore are able to serve as natural monitors of the systems they inhabit. Invertebrate communities from three relatively pristine coastal wetlands located along the northern shore of Lake Huron were compared to those from three relatively impacted Saginaw Bay c
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Thomas M. Burton, Donald G. Uzarski, Joseph P. Gathman, John A. Genet, Brian E. Keas, Craig A. Stricker
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Ecosystems Mission Area, Fort Collins Science Center

Non-USGS Publications**

Burton, T.M., Uzarski, D.G., Gathman, J.P. et al. Wetlands (1999) 19: 869. doi:10.1007/BF03161789
Uzarski, D., Burton, T. & Stricker, C. Hydrobiologia (2001) 455: 137. doi:10.1023/A:1011929719866

**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.

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