Sandhill Cranes in Colorado’s San Luis Valley: Exploring Field and Laboratory Technology for Improved Population Assessments
A Sandhill crane (Grus canadensis) grazing in a grass field. John J. Mosesso, USGS Gallery photo.
There are principally two subspecies of sandhill cranes in North America, greater sandhill cranes that breed throughout the inter-mountain west, and Lesser sandhill cranes that breed in Siberia and Alaska. In route to the wintering grounds, these two subspecies mix at important stop-over sites in the San Luis Valley. The proportion of each of these two species in the San Luis Valley is unknown and this information represents a critical need for the management of these populations. This project aims to estimate the proportion of each subspecies by genotyping DNA from feathers collected in the San Luis Valley.
Examining Range-wide Connectivity in White-tailed Ptarmigan
A White-tailed Ptarmigan on Mt. Evans in Colorado. Photo by Cameron Aldridge, USGS.
The goal of this study is to document levels of connectivity among white-tailed ptarmigan populations. Our preliminary results, based on microsatellite loci, revealed that there is significant population genetic structure throughout the species’ range. The Colorado and Vancouver Island populations were the most isolated and there was limited connectivity among populations in Alaska, the Yukon, Washington, and Montana. There is little evidence for movement from Colorado northward or from Vancouver Island eastward, raising concerns for the long term viability of two subspecies. As these areas are most impacted by climate change, this lack of connectivity to the core part of the range may have implications for the species’ ability to track shifting habitats due to warming climates.
Examining Current Subspecies Delineations in White-tailed Ptarmigan Using Genomic Data
A White-tailed Ptarmigan on Mt. Evans, Colorado. Photo by Cameron Aldridge, USGS.
The delineation of populations that are evolutionarily and demographically distinct is an important step in the development of species-specific management plans. Such knowledge is necessary for learning how conservation threats vary across a species’ range, for devising strategies to increase population growth rates, and for providing legal protection at the intraspecific level. It is also essential for conserving long-term evolutionary resilience, given that the genetic diversity that has evolved in response to spatial variation in environmental conditions could provide the raw ingredients necessary to fuel future adaptive evolution. We are using genomic data to delineate distinct evolutionary units across the range of the white-tailed ptarmigan. This information will inform management strategies for this alpine species, which may be vulnerable to climate change.
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 ecologically important events. We utilized four methods to estimate the growth rate of vibrissae in fetal, rookery pup, young-of-the-year (YOY), yearling, subadult, and adult SSL. The majority of vibrissae were collected from SSL live-captured in Alaska and Russia between 2000 and 2013 (n = 1,115), however, vibrissae were also collected from six adult SSL found dead on haul-outs and rookeries during field excursions to increase the sample size of this underrepresented age group. Growth rates of vibrissae were generally slower in adult (0.44 +/- 0.15 cm/mo) and subadult (0.61 +/- 0.10 cm/mo) SSL than in YOY (0.87 +/- 0.28 cm/mo) and fetal (0.73 +/- 0.05 cm/mo) animals, but there was high individual variability in these growth rates within each age group. Some variability in vibrissae growth rates was attributed to the somatic growth rate of YOY sea lions between capture events (P = 0.014, r2 = 0.206, n = 29).
Stable isotope values in pup vibrissae reveal geographic variation in diets of gestating Steller sea lions Eumetopias jubatus
Scherer, R.D., A.C. Doll, L.D. Rea, A.M. Christ, C.A. Stricker, B. Witteveen, T.C. Kline, C.M. Kurle, and M.B. Wunder
Spawning salmon deliver annual pulses of marine-derived nutrients (MDN) to riverine ecosystems around the Pacific Rim, leading to increased growth and condition in aquatic and riparian biota. The influence of pulsed resources may last for extended periods of time when recipient food webs have effective storage mechanisms, yet few studies have tracked the seasonal persistence of MDN. With this as our goal, we sampled stream water chemistry and selected stream and riparian biota spring through fall at 18 stations (in six watersheds) that vary widely in spawner abundance and at nine stations (in three watersheds) where salmon runs were blocked by waterfalls. We then developed regression models that related dissolved nutrient concentrations and biochemical measures of MDN assimilation to localized spawner density across these 27 stations. Stream water ammonium-N and orthophosphate-P concentrations increased with spawner density during the summer salmon runs, but responses did not persist into d15 the following fall. The effect of spawner density on N in generalist macroinvertebrates and three independent MDN metrics (d15N, d34S, and x3:x6 fatty acids) in juvenile Dolly Varden (Salvelinus malma) was positive and similar during each season, indicating that MDN levels in biota increased with spawner abundance and were maintained for at least nine months after inputs. Delta 15N in a riparian plant, horsetail (Equisetum fluviatile), and scraper macroinvertebrates did not vary with spawner density in any season, suggesting a lack of MDN assimilation by these lower trophic levels. Our results demonstrate the ready assimilation of MDN by generalist consumers and the persistence of this pulsed subsidy in these organisms through the winter and into the next growing season.