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At least 487 records · Page 27Linked to original sources
USGS2007

A genetic assessment of the recovery units for the mojave population of the desert tortoise, Gopherus agassizii

In the 1994 Recovery Plan for the Mojave population of the desert tortoise, Gopherus agassizii, the US Fish and Wildlife Service established 6 recovery units by using the best available data on habitat use, behavior, morphology, and genetics. To further assess the validity of the recovery units, we analyzed genetic data by using mitochondrial deoxyribonucleic acid (mtDNA) sequences and nuclear DNA microsatellites. In total, 125 desert tortoises were sampled for mtDNA and 628 for microsatellites from 31 study sites, representing all recovery units and desert regions throughout the Mojave Desert in California and Utah, and the Colorado Desert of California. The mtDNA revealed a great divergence between the Mojave populations west of the Colorado River and those occurring east of the river in the Sonoran Desert of Arizona. Some divergence also occurred between northern and southern populations within the Mojave population. The microsatellites indicated a low frequency of private alleles and a significant correlation between genetic and geographic distance among 31 sample sites, which was consistent with an isolation-by-distance population structure. Regional genetic differentiation was complementary to the recovery units in the Recovery Plan. Most allelic frequencies in the recovery units differed. An assignment test correctly placed most individuals to their recovery unit of origin. Of the 6 recovery units, the Northeastern and the Upper Virgin River units showed the greatest differentiation; these units may have been relatively more isolated than other areas and should be managed accordingly. The Western Mojave Recovery Unit, by using the new genetic data, was redefined along regional boundaries into the Western Mojave, Central Mojave, and Southern Mojave recovery units. Large-scale translocations of tortoises and habitat disturbance throughout the 20th century may have contributed to the observed patterns of regional similarity. ?? 2007 Chelonian Research Foundation.

California↗
USGS2014

Demography and behavior of polar bears summering on land in Alaska

Polar bears (Ursus maritimus) in the southern Beaufort Sea population (SB) are spending increased time on the coastal North Slope of Alaska between July and October (Gleason and Rode 2010). The duration spent on land by polar bears, satellite collared on the sea-ice in the spring, during the summer and fall has also increased (USGS, unpublished data; Figure 1). This change in polar bear ecology has relevance for human-bear interactions, subsistence harvest, prevalence of defense kills, and disturbance associated with existing land-based development [e.g., National Petroleum Reserve of Alaska (NPRA), Arctic National Wildlife Refuge (ANWR)], Native Alaskan communities, recreation (ANWR) and tourism (e.g., bear viewing in Kaktovik, AK). These activities have the potential to impact, in new ways, the status of the entire SB population. Concomitantly, the change in polar bear ecology will impact these human activities, and a base-line characterization of this phenomenon can better inform mitigation (e.g., industry permitting under the Endangered Species Act and Marine Mammal Protection Act). In this study we aim to characterize the demography, habitat-use, and aspects of foraging ecology and health of polar bears spending fall on land. The SB population is characterized by a divergent-sea ice ecology, where polar bears typically spend most of the year on the sea-ice, even as the pack ice retreats northward, away from the coast, to its minimal extent in September (Amstrup et al. 2008; Durner et al. 2009). From 2000 – 2005, using coastal aerial surveys, Schliebe et al. (2008) observed between 3.7 and 8% of polar bears from SB (~ 60 – 120 of 1526, Regher et al. 2006) on land during the autumn. Sighting probability was not estimated in these surveys, and therefore the numbers represent minimum numbers of bears on land. Our analysis of USGS data suggest an annual average of 15% (± 3%, SE) of polar bears satellite-tagged on the spring-time sea ice (total n = 18 of 124 satellite tags, 2003 – 2009) come to land during July – October. Based on these data, and an assumption that bears satellite-tagged on the spring time sea ice are representative of the entire SB population of independent bears, there would be an average of 230 bears on land each fall. In contrast to the SB population, in five of the world’s 19 polar bear populations (Obbard et al. 2010), polar bears spend significant periods of time on land (1 – 5 months) when ice completely melts. In these seasonal-ice populations (Amstrup et al. 2008), polar bears are largely in a hypophagic condition (e.g., Hobson et al. 2009), relying on fat stores from the spring hyperphagic season, when ringed seals (Phoca hispida) pup. In general, these seasonal-ice populations are demographically productive (Taylor et al. 2005), although recently an increase in the ice-free season has resulted in a population decline in western Hudson Bay (Stirling et al. 1999; Regehr et al. 2007). There have been measured declines in the body condition and productivity of polar bears in SB, and changes in these parameters have been linked to declining optimal ice habitat (e.g., Durner et al. 2009; Regehr et al. 2010). We do not understand the relationship between land-use and the overall status of the population. Individual polar bears that use land may have increased or decreased fitness, in comparison to polar bears that remain on ice in the autumn. This project, which focuses on the biology of animals that spend time on-shore, will help address this question. This project is funded by the Bureau of Ocean Energy Management (BOEM) under Agreement No. M09PG00025 and the USGS Outer Continental Shelf Program (OCS) for FY 2009-2014. Parts of this study are also funded by US Fish and Wildlife Service, Office of Marine Mammals Management; the Bureau of Land Management; and the North Slope Borough, Department of Wildlife Management. This report is comprehensive, describing results for achieving the overlap

Beaufort Sea, Chukchi Sea↗
USGS2002

Natal and breeding dispersal of northern spotted owls

We studied the dispersal behavior of 1,475 northern spotted owls (Strix occidentalis caurina) during banding and radio-telemetry studies in Oregon and Washington in 1985-1996. The sample included 324 radio-marked juveniles and 1,151 banded individuals (711 juveniles, 440 non-juveniles) that were recaptured or resighted after dispersing from the initial banding location. Juveniles typically left the nest during the last week in May and the first two weeks in June (x?? ?? SE = 8 June ?? 0.53 days, n = 320, range = 15 May-1 July), and spent an average of 103.7 days in the natal territory after leaving the nest (SE = 0.986 days, n = 137, range = 76-147 days). The estimated mean date that juveniles began to disperse was 19 September in Oregon (95% CI = 17-21 September) and 30 September in Washington (95% CI = 25 September-4 October). Mean dispersal dates did not differ between males and females or among years. Siblings dispersed independently. Dispersal was typically initiated with a series of rapid movements away from the natal site during the first few days or weeks of dispersal. Thereafter, most juveniles settled into temporary home ranges in late October or November and remained there for several months. In February-April there was a second pulse of dispersal activity, with many owls moving considerable distances before settling again in their second summer. Subsequent dispersal patterns were highly variable, with some individuals settling permanently in their second summer and others occupying a series of temporary home ranges before eventually settling on territories when they were 2-5 years old. Final dispersal distances ranged from 0.6-111.2 km for banded juveniles and 1.8-103.5 km for radio-marked juveniles. The distribution of dispersal distances was strongly skewed towards shorter distances, with only 8.7% of individuals dispersing more than 50 km. Median natal dispersal distances were 14.6 km for banded males, 13.5 km for radio-marked males, 24.5 km for banded females, and 22.9 km for radio-marked females. On average, banded males and females settled within 4.2 and 7.0 territory widths of their natal sites, respectively. Maximum and final dispersal distances were largely independent of the number of days that juveniles were tracked. Although statistical tests of dispersal direction based on all owls indicated that direction of natal dispersal was non-random, the mean angular deviations and 95% CI's associated with the samples were large, and r-values (vector length) were small. This lead us to conclude that significant test results were the result of large sample size and were not biologically meaningful. Our samples were not large enough to test whether dispersal direction from individual territories was random. In the sample of radio-marked owls, 22% of males and 44% of females were paired at 1 year of age, but only 1.5% of males and 1.6% of females were actually breeding at 1 year of age. At 2 years of age, 68% of males and 77% of females were paired, but only 5.4% of males and 2.6% of females were breeding. In contrast to the radio-marked owls, most juveniles that were banded and relocated at 1 or 2 years of age were paired, although few were breeding. Although recruitment into the territorial population typically occurred when owls were 1-5 years old, 9% of banded juveniles were not recaptured until they were > 5 years old. We suspect that our estimates of age at recruitment of banded owls are biased high because of the likelihood that some individuals were not recaptured in the first year that they entered the territorial population. A minimum of 6% of the banded, non-juvenile owls on our demographic study areas changed territories each year (breeding dispersal). The likelihood of breeding dispersal was higher for females, young owls, owls that did not have a mate in the previous year, and owls that lost their mate from the previous year through death or divorce. Mean and median distances dispersed by adults were

Wildlife Monographs↗
USGS2016

Management implications of brood division in Golden-winged Warblers

Brood division in the postfledging period is a common avian behavior that is not well understood. Brood division has been reported in Golden-winged Warblers ( Vermivora chrysoptera) , but it is not known how common this behavior is, whether males and females exhibit different strategies related to parental care and habitat use, or how brood division might influence management strategies. We radiomarked fledglings and monitored divided broods of Golden-winged Warblers from fledging until independence from parental care at three sites in the western Great Lakes region from 2010 to 2012 to assess differences in strategies between male and female parents and to consider possible management implications. Male - and female-reared sub-broods exhibited different space use during the dependent post-fledging period despite similar fledgling survivial, cover-type use, and microhabitat use. By independence, female-reared sub-broods traveled over twice as far from the nest (mean = 461 ± 81) SE m) as male-reared sub-broods (164 ± 41 m). Additionally, female-reared sub-broods traveled over three times as far from the natal patch edge (35 ± 72 m) as male-reared sub-broods (108 ± 36 m). Without accounting for differential space use by male- and female-reared sub-broods, we would have reported broods traveling 292 (± 46 m) from the nest and 214 (± 40m) from the natal patch edge - distances that do not reflect how far females move sub-broods. Parental strategies differ between sexes with regard to movement patterns, and we recommend incorporating the differences in space use between sexes in future management plans for Golden-winged Warblers and other species that employ brood division. Specifically, management actions might be most effective when they are applied at spatial scales large enough to incorporate the habitat requirements of both sexes throughout the entire reproductive season.

Studies in Avian Biology↗
USGS2020

Spatial and temporal diving behavior of non-breeding common murres during two summers of contrasting ocean conditions

Successful foraging of marine predators depends on environmental conditions, which also influence prey availability. Neutral or negative El Niño Southern Oscillation and Pacific Decadal Oscillation ocean conditions during the summer of 2013 and strongly positive conditions during the summer of 2015 in the northern California Current System provided a case study to evaluate a marine predator's response to anomalously warm conditions. We used satellite transmitters with saltwater switches to track movements and estimate dive behavior among non-breeding common murres (Uria aalge) off Oregon prior to and during a marine heatwave. We quantified differences in space-use between years, applied linear mixed models to determine environmental influences (e.g. sea surface temperature, surface salinity, chlorophyll a, ocean depth, and calendar date) on dive frequency and dive duration, and contrasted dive activity between time of day, year, and sexes. The majority of birds dispersed away from capture locations, which were situated near the southern range limit of their population. In both years, murres used the Salish Sea and the Columbia River plume; however, murres spent more time foraging in the Columbia River plume and in continental slope habitat during the marine heatwave of 2015. During 2015, dive frequency was reduced, and dive durations were almost twice as long during daytime indicating deeper or more dispersed prey. Increased dive frequency was positively associated with temperature, chlorophyll a, and crepuscular periods. Cluster analysis of dive activity and the top-ranked predictive dive duration model revealed associations between longer-duration dives and decreased dive frequency, marine slope habitat, and cooler ocean temperatures. Murres were relatively inactive throughout the night and we found no sex differences in dive activity. Changes in common murre foraging tactics were associated with ocean warming and revealed selectivity in spatial and temporal use of foraging habitats. Productive marine features including the Columbia River plume provided refuge for murres during apparently poor ocean conditions associated with the marine heatwave. Identifying refuge areas used by highly mobile species experiencing varying ocean conditions is critical for adaptive marine spatial planning that can accommodate a changing ocean climate.

California↗
USGS2017

Spring fasting behavior in a marine apex predator provides an index of ecosystem productivity

The effects of declining Arctic sea ice on local ecosystem productivity are not well understood but have been shown to vary inter-specifically, spatially, and temporally. Because marine mammals occupy upper trophic levels in Arctic food webs, they may be useful indicators for understanding variation in ecosystem productivity. Polar bears ( Ursus maritimus ) are apex predators that primarily consume benthic and pelagic-feeding ice-associated seals. As such, their productivity integrates sea ice conditions and the ecosystem supporting them. Declining sea ice availability has been linked to negative population effects for polar bears but does not fully explain observed population changes. We examined relationships between spring foraging success of polar bears and sea ice conditions, prey productivity, and general patterns of ecosystem productivity in the Beaufort and Chukchi Seas (CSs). Fasting status (≥7 days) was estimated using serum urea and creatinine levels of 1,448 samples collected from 1,177 adult and subadult bears across three subpopulations. Fasting increased in the Beaufort Sea between 1983–1999 and 2000–2016 and was related to an index of ringed seal body condition. This change was concurrent with declines in body condition of polar bears and observed changes in the diet, condition and/or reproduction of four other vertebrate consumers within the food chain. In contrast, fasting declined in CS polar bears between periods and was less common than in the two Beaufort Sea subpopulations consistent with studies demonstrating higher primary productivity and maintenance or improved body condition in polar bears, ringed seals, and bearded seals despite recent sea ice loss in this region. Consistency between regional and temporal variation in spring polar bear fasting and food web productivity suggests that polar bears may be a useful indicator species. Furthermore, our results suggest that spatial and temporal ecological variation is important in affecting upper trophic-level productivity in these marine ecosystems.

Global Change Biology↗
USGS2003

Comparative ontogenetic behavior and migration of kaluga, Huso dauricus, and Amur sturgeon, Acipenser schrenckii, from the Amur River

We conducted laboratory experiments with kaluga, Huso dauricus, and Amur sturgeon, Acipenser schrenckii, to develop a conceptual model of early behavior. We daily observed embryos (first life phase after hatching) and larvae (period initiating exogenous feeding) to day-30 (late larvae) for preference of bright habitat and cover, swimming distance above the bottom, up- and downstream movement, and diel activity. Day-0 embryos of both species strongly preferred bright, open habitat and initiated a strong, downstream migration that lasted 4 days (3 day peak) for kaluga and 3 days (2 day peak) for Amur sturgeon. Kaluga migrants swam far above the bottom (150 cm) on only 1 day and moved day and night; Amur sturgeon migrants swam far above the bottom (median 130 cm) during 3 days and were more nocturnal than kaluga. Post-migrant embryos of both species moved day and night, but Amur sturgeon used dark, cover habitat and swam closer to the bottom than kaluga. The larva period of both species began on day 7 (cumulative temperature degree-days, 192.0 for kaluga and 171.5 for Amur sturgeon). Larvae of both species preferred open habitat. Kaluga larvae strongly preferred bright habitat, initially swam far above the bottom (median 50-105 cm), and migrated downstream at night during days 10-16 (7-day migration). Amur sturgeon larvae strongly avoided illumination, had a mixed response to white substrate, swam 20-30 cm above the bottom during most days, and during days 12-34 (most of the larva period) moved downstream mostly at night (23-day migration). The embryo-larva migration style of the two species likely shows convergence of non-related species for a common style in response to environmental selection in the Amur River. The embryo-larva migration style of Amur sturgeon is unique among Acipenser yet studied.

Environmental Biology of Fishes↗
USGS1993

Behavior of radio-marked breeding American woodcocks

During spring 1986-89, we equipped 175 male and 89 female American woodcocks (Scolopax minor) with radio transmitters. Radio-marking had little effect on behavior; within 1 day of marking, 37 of 64 (58%) displaying males were dominant and within 7 days, 138 of 157 (88%) were dominant. All females marked before nesting proceeded to nest, and marked females with broods remained with broods after release. Dominance of males declined from 73% in April to 69% in May and to 26% in June as breeding activity waned. In all years, after-second-year (ASY) males were dominant more often than second-year (SY) males (67.5% vs. 58.9%). ;Most males displayed at more than one (range = 2-12) site. Distances that males moved between the primary singing ground and subsequent singing grounds averaged 775 m in all years and ranged from 618 m (1986) to 966 m (1988). Females visited males at singing grounds throughout the breeding cycle; some females visited more than one site. During prenesting, females remained in daytime covers during the crepuscular period (55%), flew to different feeding covers (22%), visited singing grounds (14%), or flew from daytime covers to unknown locations (9%). During nesting, females left nests during the crepuscular period (72%) and moved to singing grounds (5%), to feeding areas (59%), and to undetermined locations (7%). Females with broods remained with their broods during the crepuscular period (62%), flew to feeding areas (30%), visited singing grounds (1%), or flew to undetermined locations (6%). The woodcock mating system is similar to a resource-based polygyny. Males compete for singing grounds near high-quality nesting areas. The fitness of males is expressed by dominance at more than one singing ground. Woodcocks are not monogamous; females may visit more than three different males during a single courtship period but do not visit males regularly. Most females leave nests during the crepuscular period to feed in a different cover.

Biological Report↗
USGS2017

Life history and status of Shortnose Sturgeon (Acipenser brevirostrum LeSueur, 1818)

Shortnose Sturgeon = SNS (Acipenser brevirostrum) is a small diadromous species with most populations living in large Atlantic coast rivers and estuaries of North America from New Brunswick, Canada, to GA, USA. There are no naturally landlocked populations, so all populations require access to fresh water and salt water to complete a natural life cycle. The species is amphidromous with use of fresh water and salt water (the estuary) varied across the species range, a pattern that may reflect whether freshwater or saltwater habitats provide optimal foraging and growth conditions. Migration is a dominant behavior during life history, beginning when fish are hatchling free embryos (southern SNS) or larvae (northeastern and far northern SNS). Migration continues by juveniles and nonspawning adult life stages on an individual time schedule with fish moving between natal river and estuary to forage or seek refuge, and by spawning adults migrating to and from riverine spawning grounds. Coastal movements by adults throughout the range (but particularly in the Gulf of Maine = GOM and among southern rivers) suggest widespread foraging, refuge use, and widespread colonization of new rivers. Colonization may also be occurring in the Potomac River, MD–VA–DC (midAtlantic region). Genetic studies (mtDNA and nDNA) identified distinct individual river populations of SNS, and recent rangewide nDNA studies identified five distinct evolutionary lineages of SNS in the USA: a northern metapopulation in GOM rivers; the Connecticut River; the Hudson River; a Delaware River–Chesapeake Bay metapopulation; and a large southern metapopulation (SC rivers to Altamaha River, GA). The Saint John River, NB, Canada, in the Bay of Fundy (north of the GOM), is the sixth distinct genetic lineage within SNS. Life history information from telemetry tracking supports the genetic information documenting extensive movement of adults among rivers within the three metapopulations. However, individual river populations with spawning adults are still the best basal unit for management and recovery planning. The focus on individual river populations should be complemented with attention to migratory processes and corridors that foster metapopulation level risks and benefits. The species may be extirpated at the center of the range, i.e., the midAtlantic region (Chesapeake Bay, MD–VA, and probably, NC), but large rivers in VA, including the James and Potomac rivers, need study. The largest SNS populations in GOM and northeastern rivers, like the Kennebec, Hudson, and Delaware rivers, typically have tens of thousands of adults. This contrasts with southern rivers, where rivers typically have much fewer (<2500) adults, except for the Altamaha River (>6000 adults). River damming in the 19th and 20th Centuries extirpated some populations, and also, created two dysfunctional segmented populations: the Connecticut River SNS in CT–MA and the SanteeCooper rivers–Lake Marion SNS in SC. The major anthropogenic impact on SNS in marine waters is fisheries bycatch. The major impacts that determine annual recruitment success occur in freshwater firstly, where adult spawning migrations and spawning are blocked or spawning success is affected by river regulation and secondly, where poor survival of early life stages is caused by river dredging, pollution, and unregulated impingement/entrainment in water withdrawal facilities. Climate warming has the potential to reduce abundance or eliminate SNS in many rivers, particularly in the South. In 1998, the National Marine Fisheries Service (NMFS) recommended management of 19 rivers as distinct population segments (DPSs) based on strong fidelity to natal rivers. A Biological Assessment completed in 2010 reaffirmed this approach. NMFS has not formally listed DPSs under the ESA and the species remains listed as endangered rangewide in the USA.

Journal of Applied Ichthyology↗
USGS2008

Interaction between introduced trout and larval salamanders (Ambystoma macrodactylum) in high-elevation lakes

The larval stage of the long-toed salamander ( Ambystoma macrodactylum ) is the top vertebrate predator in high-elevation fishless lakes in the North Cascades National Park Service Complex, Washington (U.S.A.). Although most of these high-elevation lakes were naturally fishless, trout have been stocked in many of them. We sought to determine the effects of physicochemical factors and introduced trout on abundance and behavior of A. macrodactylum larvae. Larval salamander densities were estimated by snorkeling. Snorkelers carefully searched through substrate materials within 2 m of the shoreline and recorded the number of larvae observed and if larvae were hidden in benthic substrates. Physicochemical factors were measured in each lake on the same day that snorkel surveys were conducted. In fishless lakes, larval salamander densities were positively related to total Kjeldahl-N concentration and negatively related to lake elevation. Crustacean zooplankton, especially cladocerans, were important food resources for larval A. macrodactylum . Crustacean zooplankton and cladoceran densities were positively related to total Kjeldahl-N, suggesting that increased food resources contributed to increased densities of larval A. macrodactylum . Differences in larval salamander densities between fish and fishless lakes were related to total Kjeldahl-N concentrations and the reproductive status of trout. Mean larval salamander densities for fishless lakes with total Kjeldahl-N < 0.045 mg/L were not significantly different from mean larval densities in lakes with reproducing trout or in lakes with nonreproducing trout. In fishless lakes with total Kjeldahl-N ≥ 0.045 mg/L, however, mean larval densities were significantly higher than in lakes with reproducing trout where fish reached high densities. In fishless lakes with total Kjeldahl-N ≥ 0.095 mg/L, mean larval densities were significantly higher than in lakes with nonreproducing trout where trout fry were stocked at low densities. Reduced larval salamander densities in lakes with trout likely resulted from trout predation. There were no significant differences in the percentage of larvae hidden in benthic substrates between fishless lakes and lakes with fish. Our results imply that assessment of the effects of fish on amphibians requires an understanding of natural abiotic and biotic factors and processes influencing amphibian distribution and abundance.

Washington↗
USGS2016

A dynamic leaf gas-exchange strategy is conserved in woody plants under changing ambient CO 2 : evidence from carbon isotope discrimination in paleo and CO 2 enrichment studies

Rising atmospheric [CO 2 ], c a , is expected to affect stomatal regulation of leaf gas-exchange of woody plants, thus influencing energy fluxes as well as carbon (C), water, and nutrient cycling of forests. Researchers have proposed various strategies for stomatal regulation of leaf gas-exchange that include maintaining a constant leaf internal [CO 2 ], c i , a constant drawdown in CO 2 ( c a − c i ), and a constant c i / c a . These strategies can result in drastically different consequences for leaf gas-exchange. The accuracy of Earth systems models depends in part on assumptions about generalizable patterns in leaf gas-exchange responses to varying c a . The concept of optimal stomatal behavior, exemplified by woody plants shifting along a continuum of these strategies, provides a unifying framework for understanding leaf gas-exchange responses to c a . To assess leaf gas-exchange regulation strategies, we analyzed patterns in c i inferred from studies reporting C stable isotope ratios (δ 13 C) or photosynthetic discrimination (∆) in woody angiosperms and gymnosperms that grew across a range of c a spanning at least 100 ppm. Our results suggest that much of the c a -induced changes in c i / c a occurred across c a spanning 200 to 400 ppm. These patterns imply that c a − c i will eventually approach a constant level at high c a because assimilation rates will reach a maximum and stomatal conductance of each species should be constrained to some minimum level. These analyses are not consistent with canalization toward any single strategy, particularly maintaining a constant c i . Rather, the results are consistent with the existence of a broadly conserved pattern of stomatal optimization in woody angiosperms and gymnosperms. This results in trees being profligate water users at low c a , when additional water loss is small for each unit of C gain, and increasingly water-conservative at high c a , when photosystems are saturated and water loss is large for each unit C gain.

Global Change Biology↗
USGS2024

Bringing traits back in the equation: A roadmap to understand species redistribution

Ecological and evolutionary theories have proposed that species traits should be important in mediating species responses to contemporary climate change; yet, empirical evidence has so far provided mixed evidence for the role of behavioral, life history, or ecological characteristics in facilitating or hindering species range shifts. As such, the utility of trait-based approaches to predict species redistribution under climate change has been called into question. We develop the perspective, supported by evidence, that trait variation, if used carefully can have high potential utility, but that past analyses have in many cases failed to identify an explanatory value for traits by not fully embracing the complexity of species range shifts. First, we discuss the relevant theory linking species traits to range shift processes at the leading (expansion) and trailing (contraction) edges of species distributions and highlight the need to clarify the mechanistic basis of trait-based approaches. Second, we provide a brief overview of range shift–trait studies and identify new opportunities for trait integration that consider range-specific processes and intraspecific variability. Third, we explore the circumstances under which environmental and biotic context dependencies are likely to affect our ability to identify the contribution of species traits to range shift processes. Finally, we propose that revealing the role of traits in shaping species redistribution may likely require accounting for methodological variation arising from the range shift estimation process as well as addressing existing functional, geographical, and phylogenetic biases. We provide a series of considerations for more effectively integrating traits as well as extrinsic and methodological factors into species redistribution research. Together, these analytical approaches promise stronger mechanistic and predictive understanding that can help society mitigate and adapt to the effects of climate change on biodiversity.

Global Change Biology↗
USGS2013

Permeability of roads to movement of scrubland lizards and small mammals

A primary objective of road ecology is to understand and predict how roads affect connectivity of wildlife populations. Road avoidance behavior can fragment populations, whereas lack of road avoidance can result in high mortality due to wildlife-vehicle collisions. Many small animal species focus their activities to particular microhabitats within their larger habitat. We sought to assess how different types of roads affect the movement of small vertebrates and to explore whether responses to roads may be predictable on the basis of animal life history or microhabitat preferences preferences. We tracked the movements of fluorescently marked animals at 24 sites distributed among 3 road types: low-use dirt, low-use secondary paved, and rural 2-lane highway. Most data we collected were on the San Diego pocket mouse ( Chaetodipus fallax ), cactus mouse ( Peromyscus eremicus ), western fence lizard ( Sceloporus occidentalis ), orange-throated whiptail ( Aspidoscelis hyperythra ), Dulzura kangaroo rat ( Dipodomys simulans ) (dirt, secondary paved), and deer mouse (Peromyscus maniculatus) (highway only). San Diego pocket mice and cactus mice moved onto dirt roads but not onto a low-use paved road of similar width or onto the highway, indicating they avoidpaved road substrate. Both lizard species moved onto the dirt and secondary paved roads but avoided the rural 2-lane rural highway, indicating they may avoid noise, vibration, or visual disturbance from a steady flow of traffic. Kangaroo rats did not avoid the dirt or secondary paved roads. Overall, dirt and secondary roads were more permeable to species that prefer to forage or bask in open areas of their habitat, rather than under the cover of rocks or shrubs. However, all study species avoided the rural 2-lane highway. Our results suggest that microhabitat use preferences and road substrate help predict species responses to low-use roads,but roads with heavy traffic may deter movement of a much wider range of small animal species.

California↗
USGS1979

Endocrine correlates of reproduction in the wolf. I. Serum progesterone, estradiol and LH during the estrous cycle

The estrous cycle of 10 intact female wolves, aged 8 months-8 years at the initiation of the study, was characterized in terms of vaginal smears, behavioral observations and serum concentrations of estradiol-17β, progesterone and luteinizing hormone (LH) from January through June. No estrous cycles occurred in these animals between June and December. All were housed with male wolves. Two pups and 1 adult remained anestrous during this interval. One pup and 2 adults produced litters between May 4-6. Four adults exhibited endocrine changes similar to those of the pregnant animals but no litters or signs of abortion were observed. The duration of proestrus was 15.7 ± 1.6 days (X ± SEM, n = 6), of estrus 9.0 ± 1.2 days (n = 4) and of the luteal phase 63 ± 2 days (n = 6). The duration of pregnancy was between 60-65 days. The anestrous females (86 blood samples) had 6 progesterone values between 1-2 ng/ml and the remainder below 1 ng/ml. Their estradiol-17β concentrations varied between 5-20 pg/ml. Values for LH varied between 0.1-2 ng/ml, except for 1 value above 15 ng/ml for each of the 2 anestrous pups on 12 January. The 7 estrous animals (260 samples) included 1 pup and 2 adults that delivered litters. Estradiol-17β varied between 10-20 pg/ml during proestrus, peaked at 30-70 pg/ml late in proestrus and fluctuated between 10-30 pg/ml during pregnancy or the duration of luteal activity in the nonpregnant animals. The preovulatory LH rise, 5-15 ng/ml, extended over 3 days during and immediately following the peak estradiol-17β values. An earlier elevation in LH was observed in 3 of the estrous animals. Progesterone began increasing during the LH surge and peaked 11-14 days later at 22-40 ng/ml. Progesterone concentrations greater than 3 ng/ml were maintained for 56-68 days in 6 of the 7 animals exhibiting estrus. Progesterone concentrations declined at parturition but continued to fluctuate between 0.2-3 ng/ml for 3-6 weeks.

Biology of Reproduction↗
USGS2018

Factors affecting nesting ecology of Apalone spinifera in a northwestern Great Plains river of the United States

The nesting ecology of Apalone spinifera in large North American rivers is largely unknown despite the wide distribution of the species in these naturally dynamic ecosystems. We describe the nesting locations, timing, behavior, and habitat of A. spinifera in relation to natural and anthropogenic factors in the Missouri River. Nesting followed annual peak river stage, mostly occurred in the afternoon when air temperatures were 25°–30°C, and did not occur when human activity was nearby. Apalone spinifera nested in June in a year with average discharge (2012), but nested 20 d later in a year with a large flood event (2011). During the average discharge year, 90% of nests were found on islands, but similar proportions of nests were found on island and mainland habitats during the flood year because many islands were inundated. Nests were mostly in mixed-gravel substrates where vegetation cover was sparse or absent. Depredation occurred only after the emergence of hatchlings (∼ 60 d after nesting) and more often on nests on the mainland than on islands. Emergence rates were ∼ 1.5 times higher in the average year than the flood year, and emergence rates were higher in mixed-gravel nests than in pure-sand nests in 2011. In artificial nests, incubation temperatures averaged ∼ 4.3°C higher in mixed-gravel than in sand substrates, and freezing temperatures in winter penetrated to depths greater than the mean egg chamber depth (7.5 cm) for up to 3 wks. Therefore, incubation might be accelerated in mixed-gravel substrates. Accelerated incubation would enhance reproductive success because freezing temperatures preclude hatchlings from overwintering in nests in our study area. Mountain snowmelt-driven hydrology, coupled with the onset of freezing temperatures in autumn, might create a temporal “runoff-freeze squeeze” that limits the successful reproduction of A. spinifera in some years. However, high runoff also scoured vegetation from shorelines where A. spinifera nested in subsequent years. Natural variation in annual discharge might therefore be crucial to conservation of A. spinifera in large rivers.

Chelonian Conservation and Biology↗
USGS2019

Plasticity in elk migration timing is a response to changing environmental conditions

Migration is an effective behavioral strategy for prolonging access to seasonal resources and may be a resilient strategy for ungulates experiencing changing climatic conditions. In the Greater Yellowstone Ecosystem (GYE), elk are the primary ungulate, with approximately 20,000 individuals migrating to exploit seasonal gradients in forage while also avoiding energetically costly snow conditions. How climate-induced changes in plant phenology and snow accumulation are influencing elk migration timing is unknown. We present the most complete record of elk migration across the GYE, spanning 9 herds and 414 individuals from 2001 to 2017, to evaluate the drivers of migration timing and test for temporal shifts. The timing of elk departure from winter range involved a trade-off between current and anticipated forage conditions, while snow melt governed summer range arrival date. Timing of elk departure from summer range and arrival on winter range were both influenced by snow accumulation and exposure to hunting. At the GYE scale, spring and fall migration timing changed through time, most notably with winter range arrival dates becoming almost 50 days later since 2001. Predicted herd-level changes in migration timing largely agreed with observed GYE-wide changes—except for predicted winter range arrival dates which did not reflect the magnitude of change detected in the elk telemetry data. Snow melt, snow accumulation, and spring green-up dates all changed through time, with different herds experiencing different rates and directions of change. We conclude that elk migration is plastic, is a direct response to environmental cues, and that these environmental cues are not changing in a consistent manner across the GYE. The impacts of changing elk migration timing on predator–prey dynamics, carnivore–livestock conflict, disease ecology, and harvest management across the GYE are likely to be significant and complex.

Idaho, Montana, Wyoming↗
USGS1981

Biological and economic impact of stream alteration in the Virginia Piedmont

A 31 month (September 1974 - March 1977) study was conducted on warmwater streams located in the Roanoke Creek watershed of the Piedmont Region of Virginia. The purpose of the study was to determine the effects of stream channelization on the aquatic/riparian wildlife resource and agricultural land-use patterns associated with the altered streams. Three streams, which were channelized 3, 6, and 10 years prior to initiation of the study, and teo unaltered streams, were selected as representative streams for the study. Recently channelized streams lacked overstory cover but has an abundance of herbaceous and small woody plany cover, Conversely, control streams had significantly larger percentages of trees over 46 m tall. Plant species diversity, foliage height diversity, and evenness diversity increased as age since channelization increased. No major differences in water quality parameters were found for either channelized or control streams, although channelized streams had greater deposits of sand and lesser amount of rock, rubble, and gravel. These changes in substrate composition did not significantly modify actual stream flow rates. Fish species composition and species diversity among channelized and unchannelized streams were only slightly different, with most of the differences probably attributable to strays from adjacent habitats, However, evenness diversity for fish communities was lower in channelized streams. The benthic population showed greater changes than did the fish populations with an increase in Chironominae tolerant of unstable sand substrates in channelized streams. Evenness diversity of benthic populations was also higher and showed more consistency in the control stream than in channelized streams. Evenness diversity of benthic communities in control stream averaged between 0.5 to 0.6 and was quite consistent; whereas, the average in the two youngest channelized streams was 0.3 to 0.4. These data seem to indicate decreased stability of the biota in altered streams. In general, benthic macroinvertabrate and fish community parameters collected from channelized streams located 1200 m below a reservoir were either comparable to, or intermediate between, upstream (unchannelized) and reservoir tailwater values. The shallow surface discharge impoundments associated with channelized streams appeared to have a highly localized impact on the downstream benthic marcoinvertabrate and fish communities. During winter, bird species diversity (BSD) among channelized stream sites was not significantly different. During the breeding season, species richness (number of breeding species) and BSD increased with age since channelization. Breeding bird densities were 6.2 pairs/ha in the most recent (3 yr) channelized site and 13.3 pairs/ha on the control streams. Bird diversity and density, particularly for Parulids (warblers), during the breeding season were reduced significantly by removal of tree and shrub layers along channelized streams. No significant differences were found among study sites for either total number of small mammals or their species diversity indices; although, there was a trend toward increasing diversity as age since channelization increased. Smaller differences in species diversity values for small mammals on channelized sites than for birds suggests that small mammal populations require less time for recovery following channelization than avian communities. When streams are channelized: 1) vegetation should be removed from only one side of the stream, with minimal disturbance of top-soil; followed by plantings of herbaceous and woody vegetation, 2) hedgrow plantings should be maintained between agricultural fields and the stream for bank stabilization, 3) dead snags and large trees should be left for birds, 4) all channelization projects should be designed according to the most recent guidelines recommended by the SCS and other resources agencies. In 1958, the Roanoke County Watershed Work Plan projected annual costs of the structured measures (mainly reservoirs and downstream channelization) to be $79,897 and the average annual monetary benefits to be $111,103. With this favorable benefit/cost ration of 1.4, work began in 1960. In 1970, the annual capital cost was 60,780 and operations/maintenance costs were 10,402, or a total annual project cost of $71, 182. High and low values of annual benefits from agricultural income, water supply, recreation, and non-agricultural flood damage were determined for 1970 and compared to annual project cost. The benefit/cost ratio obtained was between 0.25 and 0.58, considerably lower than the 1.4 estimate of the 1958. work plan. This unsatisfactory ratio for the project was due mainly to the failure of the project to encourage large scale cropping of bottomland area. Future projects should be planned with 1) a greater recognition of constraints on farm operator behavior which affect land use change, 2) conservative projection for land use changes in area where agriculture ids in overall decline, 3) increased use of sensitivity analysis to examine the consequences for project economic justification of alternative land use change projections.

Virginia↗
USGS2016

Sex differences in contaminant concentrations of fish: a synthesis

Comparison of whole-fish polychlorinated biphenyl (PCB) and total mercury (Hg) concentrations in mature males with those in mature females may provide insights into sex differences in behavior, metabolism, and other physiological processes. In eight species of fish, we observed that males exceeded females in whole-fish PCB concentration by 17 to 43%. Based on results from hypothesis testing, we concluded that these sex differences were most likely primarily driven by a higher rate of energy expenditure, stemming from higher resting metabolic rate (or standard metabolic rate (SMR)) and higher swimming activity, in males compared with females. A higher rate of energy expenditure led to a higher rate of food consumption, which, in turn, resulted in a higher rate of PCB accumulation. For two fish species, the growth dilution effect also made a substantial contribution to the sex difference in PCB concentrations, although the higher energy expenditure rate for males was still the primary driver. Hg concentration data were available for five of the eight species. For four of these five species, the ratio of PCB concentration in males to PCB concentration in females was substantially greater than the ratio of Hg concentration in males to Hg concentration in females. In sea lamprey (Petromyzon marinus), a very primitive fish, the two ratios were nearly identical. The most plausible explanation for this pattern was that certain androgens, such as testosterone and 11-ketotestosterone, enhanced Hg-elimination rate in males. In contrast, long-term elimination of PCBs is negligible for both sexes. According to this explanation, males ingest Hg at a higher rate than females, but also eliminate Hg at a higher rate than females, in fish species other than sea lamprey. Male sea lamprey do not possess either of the above-specified androgens. These apparent sex differences in SMRs, activities, and Hg-elimination rates in teleost fishes may also apply, to some degree, to higher vertebrates including humans. Our synthesis findings will be useful in: (1) developing sex-specific bioenergetics models for fish, (2) developing sex-specific risk assessment models for exposure of humans and wildlife to contaminants, and (3) refining Hg mass balance models for fish and higher vertebrates.

Biology of Sex Differences↗