Comparative studies of populations occupying different environments can provide insights into the ecological conditions affecting differences in parental strategies, including the relative contributions of males and females. Male and female parental strategies reflect the interplay between ecological conditions, the contributions of the social mate, and the needs of offspring. Climate is expected to underlie geographic variation in incubation and brooding behavior, and can thereby affect both the absolute and relative contributions of each sex to other aspects of parental care such as offspring provisioning. However, geographic variation in brooding behavior has received much less attention than variation in incubation attentiveness or provisioning rates. We compared parental behavior during the nestling period in populations of orange-crowned warblers Oreothlypis celata near the northern (64°N) and southern (33°N) boundaries of the breeding range. In Alaska, we found that males were responsible for the majority of food delivery whereas the sexes contributed equally to provisioning in California. Higher male provisioning in Alaska appeared to facilitate a higher proportion of time females spent brooding the nestlings. Surprisingly, differences in brooding between populations could not be explained by variation in ambient temperature, which was similar between populations during the nestling period. While these results represent a single population contrast, they suggest additional hypotheses for the ecological correlates and evolutionary drivers of geographic variation in brooding behavior, and the factors that shape the contributions of each sex.
Why You Can’t Ignore Disease When You Reintroduce Animals
Infectious disease is an important consideration when contemplating reintroduction of a species to an area from which it has been extirpated and is one risk that has escalated in recent decades as use of large-scale and hands-on conservation measures increase. Reintroduction (in essence moving animals around), is a management tool considered when populations are failing or extirpations have occurred, yet is obviously at odds with many of the tenets of disease management. We focus on extirpations attributed to disease and formulate a decision tree to guide managers considering reintroduction. If disease was not the original cause of extinction or decline, it still is important to consider as inadvertent introduction of disease with reintroduced hosts may cause a reintroduction to fail, or may threaten members of the recipient ecological community. If disease was an important agent of extinction or decline, then the disease threat must be addressed before reintroduction is contemplated, or the effort is highly likely to fail. If disease resistant or tolerant stock are available, then reintroducing these animals may succeed. If such stock are not available, then it is important to determine whether reservoirs are present, and if they are, to develop strategies to manage disease adequately in the reservoirs. If reservoirs are not present, then the biggest threat to a reintroduction is the presence of still-infected members of the species being reintroduced. We illustrate these principles with two case studies, the boreal toad (Anaxyrus (Bufo) boreas), threatened by the amphibian chytrid fungus (Batrachochytrium dendrobatidis) and the Tasmanian devil (Sarcophilus hariisii), threatened by a transmissible cancer.
Integrating subsistence practice and species distribution modeling: assessing invasive elodea’s potential impact on Native Alaskan subsistence of Chinook salmon and whitefish
Luizza, M. W., P. H. Evangelista, C. S. Jarnevich, A. West, and H. Stewart
Alaska has one of the most rapidly changing climates on earth and is experiencing an accelerated rate of human disturbance, including resource extraction and transportation infrastructure development. Combined, these factors increase the state’s vulnerability to biological invasion, which can have acute negative impacts on ecological integrity and subsistence practices. Of growing concern is the spread of Alaska’s first documented freshwater aquatic invasive plant Elodea spp. (elodea). In this study, we modeled the suitable habitat of elodea using global and state-specific species occurrence records and environmental variables, in concert with an ensemble of model algorithms. Furthermore, we sought to incorporate local subsistence concerns by using Native Alaskan knowledge and available statewide subsistence harvest data to assess the potential threat posed by elodea to Chinook salmon (Oncorhynchus tshawytscha) and whitefish (Coregonus nelsonii) subsistence. State models were applied to future climate (2040–2059) using five general circulation models best suited for Alaska. Model evaluations indicated that our results had moderate to strong predictability, with area under the receiver-operating characteristic curve values above 0.80 and classification accuracies ranging from 66 to 89 %. State models provided a more robust assessment of elodea habitat suitability. These ensembles revealed different levels of management concern statewide, based on the interaction of fish subsistence patterns, known spawning and rearing sites, and elodea habitat suitability, thus highlighting regions with additional need for targeted monitoring. Our results suggest that this approach can hold great utility for invasion risk assessments and better facilitate the inclusion of local stakeholder concerns in conservation planning and management.
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