Craig Stricker, Ph.D.
Science and Products
Environmental contaminants of natural and anthropogenic origin represent a major stressor to ecosystems, including human and wildlife populations.
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, general location and activity information are unavailable.
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.
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, pollution, and climate change can drastically alter the availability and quality of dietary resources. Stable isotope techniques offer a useful tool for gaining longer-term insight into the dietary habits for a variety of wildlife species.
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.
To create this dataset the authors exposed larval mayflies (Baetis tricaudatus) to an aqueous zinc gradient (3-340 µg Zn/l) and measured the change in zinc tissue concentrations at different stages of metamorphosis and changes in stable isotopes (δ15N and δ13C) in unexposed B. tricaudatus. Zinc concentrations in larvae and adults were positively related to aqueous concentrations.
Mechanisms associated with an advance in the timing of seasonal reproduction in an urban songbird
The colonization of urban environments by animals is often accompanied by earlier breeding and associated changes in seasonal schedules. Accelerated timing of seasonal reproduction in derived urban populations is a potential cause of evolutionary divergence from ancestral populations if differences in physiological processes that regulate...Fudickar, Adam M.; Greives, Timothy J; Abolins-Abols, Mikas; Atwell, Jonathan W.; Meddle, Simone L.; Friis, Guillermo; Stricker, Craig A.; Ketterson, Ellen D.
Opinion: Why we need a centralized repository for isotopic data
Stable isotopes encode and integrate the origin of matter; thus, their analysis offers tremendous potential to address questions across diverse scientific disciplines (1, 2). Indeed, the broad applicability of stable isotopes, coupled with advancements in high-throughput analysis, have created a scientific field that is growing exponentially, and...Pauli, Jonathan N.; Newsome, Seth D.; Cook, Joseph A.; Harrod, Chris; Steffan, Shawn A.; Baker, Christopher J. O.; Ben-David, Merav; Bloom, David; Bowen, Gabriel J.; Cerling, Thure E.; Cicero, Carla; Cook, Craig; Dohm, Michelle; Dharampal, Prarthana S.; Graves, Gary; Gropp, Robert; Hobson, Keith A.; Jordan, Chris; MacFadden, Bruce; Pilaar Birch, Suzanne; Poelen, Jorrit; Ratnasingham, Sujeevan; Russell, Laura; Stricker, Craig A.; Uhen, Mark D.; Yarnes, Christopher T.; Hayden, Brian
Zinc concentrations and isotopic signatures of an aquatic insect (mayfly, Baetis tricaudatus)
Insect metamorphosis often results in substantial chemical changes that can fractionate isotopes and alter contaminant concentrations. We exposed larval mayflies (Baetis tricaudatus) to an aqueous zinc gradient (3-340 µg Zn/l) and measured the change in zinc tissue concentrations at different stages of metamorphosis. We also measured changes in...Wesner, Jeff S; Walters, David; Schmidt, Travis S.; Kraus, Johanna M.; Stricker, Craig A.; Clements, William H.
Metamorphosis affects metal concentrations and isotopic signatures in a mayfly (Baetis tricaudatus): Implications for the aquatic-terrestrial transfer of metals
Insect metamorphosis often results in substantial chemical changes that can alter contaminant concentrations and fractionate isotopes. We exposed larval mayflies (Baetis tricaudatus) and their food (periphyton) to an aqueous zinc gradient (3-340 µg Zn/l) and measured zinc concentrations at different stages of metamorphosis: larval, subimago, and...Wesner, Jeff S.; Walters, David; Schmidt, Travis S.; Kraus, Johanna M.; Stricker, Craig A.; Clements, William H.; Wolf, Ruth E.
Trophic pathways supporting juvenile Chinook and Coho salmon in the glacial Susitna River, Alaska: patterns of freshwater, marine, and terrestrial resource use across a seasonally dynamic habitat mosaic
Contributions of terrestrial-, freshwater-, and marine-derived prey resources to stream fishes vary over time and space, altering the energy pathways that regulate production. In this study, we determined large-scale use of these resources by juvenile Chinook and coho salmon (Oncorhynchus tshawytscha and Oncorhynchus kisutch, respectively) in the...Rine, Kristin M.; Wipfli, Mark S.; Schoen, Erik R.; Nightengale, Timothy L.; Stricker, Craig A.
Isotopic incorporation and the effects of fasting and dietary lipid content on isotopic discrimination in large carnivorous mammals
There has been considerable emphasis on understanding isotopic discrimination for diet estimation in omnivores. However, discrimination may differ for carnivores, particularly species that consume lipid-rich diets. Here, we examined the potential implications of several factors when using stable isotopes to estimate the diets of bears, which can...Rode, Karyn D.; Stricker, Craig A.; Erlenbach, Joy; Robbins, Charles T.; Cherry, Seth; Newsome, Seth D.; Cutting, Amy; Jensen, Shannon; Stenhouse, Gordon; Brooks, Matt; Hash, Amy; Nicassio, Nicole
Reproductive allochrony in seasonally sympatric populations maintained by differential response to photoperiod: Implications for population divergence and response to climate change
Reproductive allochrony presents a potential barrier to gene flow and is common in seasonally sympatric migratory and sedentary birds. Mechanisms mediating reproductive allochrony can influence population divergence and the capacity of populations to respond to environmental change. We asked whether reproductive allochrony in seasonally sympatric...Fudickar, A.M.; Grieves, T.J.; Atwell, Jonathan W.; Stricker, Craig A.; Ketterson, Ellen D.
Wood decay in desert riverine environments
Floodplain forests and the woody debris they produce are major components of riverine ecosystems in many arid and semiarid regions (drylands). We monitored breakdown and nitrogen dynamics in wood and bark from a native riparian tree, Fremont cottonwood (Populus deltoides subsp. wislizeni), along four North American desert streams. We...Andersen, Douglas; Stricker, Craig A.; Nelson, S. Mark
Isotopic insights into biological regulation of zinc in contaminated systems
Aquatic organisms use a variety of biogeochemical reactions to regulate essential and non-essential trace metals. Many of these mechanisms can lead to isotopic fractionation, thus measurement of metal isotopes may yield insights into the processes by which organisms respond to metal exposure. We illustrate these concepts with two case studies, one...Wanty, Richard B.; Balistrieri, Laurie S.; Wesner, Jeff S.; Walters, David; Schmidt, Travis S.; Podda, Francesca; De Giudici, G.; Stricker, Craig A.; Kraus, Johanna M.; Lattanzi, Pierfranco; Wolf, Ruth E.; Cidu, R.
Ecotoxicoparasitology: Understanding mercury concentrations in gut contents, intestinal helminths and host tissues of Alaskan gray wolves (Canis lupus)
Some gastrointestinal helminths acquire nutrients from the lumen contents in which they live; thus, they may be exposed to non-essential elements, such as mercury (Hg), during feeding. The objectives of this study were: 1) determine the total mercury concentrations ([THg]) in Gray wolves (Canis lupus) and their parasites, and 2) use stable...McGrew, Ashley K.; O'Hara, Todd M.; Stricker, Craig A.; Castellini, Margaret; Beckmen, Kimberlee B.; Salman, Mo D.; Ballweber, Lora R.
Comment on "Donders, T.H. 2014. Middle Holocene humidity increase in Florida: climate or sea-level? Quaternary Science Reviews 103:170-174."
Donders (2014) has recently proposed that the climate of Florida became progressively wetter over the past 5000 years in response to a marked strengthening of the El Niño regime. This reconstruction is largely based on a re-analysis of pollen records from regions north of Lake Okeechobee (Fig. 1) using a new set of pollen transfer...Glaser, Paul H.; Hansen, Barbara CS; Donovan, Joseph J.; Givnish, Thomas J.; Stricker, Craig A.; Volin, John C.
Age-specific vibrissae growth rates: a tool for determining the timing of ecologically important events in Steller sea lions
Steller sea lions (SSL; Eumetopias jubatus) grow their vibrissae continually, providing a multiyear record suitable for ecological and physiological studies based on stable isotopes. An accurate age-specific vibrissae growth rate is essential for registering a chronology along the length of the record, and for interpreting the timing of...Rea, L.D.; Christ, A.M.; Hayden, A.B.; Stegall, V.K.; Farley, S.D.; Stricker, Craig A.; Mellish, J.E.; Maniscalco, John M.; Waite, J.N.; Burkanov, V.N.; Pitcher, K.W.