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At least 109 records · Page 6Linked to original sources

USGS2004

Similarities in acute phase protein response during hibernation in black bears and major depression in humans: A response to underlying metabolic depression?

This study investigated the effects of hibernation with mild hypothermia and the stress of captivity on levels of six acute-phase proteins (APPs) in serial samples of serum from 11 wild and 6 captive black bears (Ursus americanus Pallas, 1780) during active and hibernating states. We hypothesize that during hibernation with mild hypothermia, bears would show an APP response similar to that observed in major depression. Enzyme-linked immunoabsorbent assay was used to measure alpha2-macroglobulin and C-reactive protein, and a nephelometer to measure alpha1-antitrypsin, haptoglobin, ceruloplasmin, and transferrin. Levels of all other proteins except ceruloplasmin were significantly elevated during hibernation in both wild and captive bears at the p < 0.05 to p < 0.001 level. Alpha 2-macroglobulin and C-reactive-protein levels were increased in captive versus wild bears in both active and hibernating states at the p < 0.01 to p < 0.0001 level. During hibernation with mild hypothermia, black bears do not show immunosuppression, but show an increased APP response similar to that in patients with major depression. This APP response is explained as an adaptive response to the underlying metabolic depression in both conditions. Metabolic depression in hibernating bears is suggested as a natural model for research to explain the neurobiology of depression.

Canadian Journal of Zoology↗

USGS2004

Stable foraging areas and variable chick diet in Cassin's auklets (Ptychoramphus aleuticus) off southern California

Planktivorous seabirds readily respond to changes in marine ecosystems and have the ability to integrate information regarding variability in abundance, availability, and community composition of key prey resources. We studied the foraging and breeding ecology of the Cassin's auklet, Ptychoramphus aleuticus (Pallas, 1811), off southern California during three breeding seasons (1999-2001), when large intra- and inter-annual variability occurred in local oceanographic conditions during a prolonged La Nina event. Radio-marked parents used consistent core foraging areas within 30 km of their colony, aggregated in shelf waters (< 200 m depth), and occasionally foraged in deeper waters. Parents delivered primarily euphausiids, pelagic larval-juvenile fishes, and minor amounts of cephalopods and other crustaceans. Whereas the euphausiid Thysanoessa spinifera Holmes, 1900 was most important during 1999 and 2001, Euphausia pacifica Hansen, 1911 replaced adult T. spinifera in 2000 after an anomalous eastward inflection of the California Current occurred near the auklets' foraging area. Differences in chick diets, however, did not significantly influence fledging success and growth among first chicks, but the proportion of pairs successfully fledging an alpha chick and initiating a second clutch was exceptional in 1999 (63%) and 2000 (75%), and less in 2001 (7%). We suggest that dietary composition was influenced by modified prey availability driven in part by fluctuations in regional upwelling and circulation. ?? 2004 NRC Canada.

Canadian Journal of Zoology↗

USGS2004

Migration and stopover strategies of individual Dunlin along the Pacific coast of North America

We radio-marked 18 Dunlin, Calidris alpina (L., 1758), at San Francisco Bay, California, and 11 Dunlin at Grays Harbor, Washington, and relocated 90% of them along the 4200 km long coastline from north of San Francisco Bay to the Yukon-Kuskokwim Delta, Alaska. The Copper River Delta, Alaska, was the single most important stopover site, with 79% of the marked birds detected there. Our second most important site was the Willapa Bay and Grays Harbor complex of wetlands in Washington. The mean length of stay past banding sites ranged from 1.0 to 3.8 days. Controlling for date of departure, birds banded at San Francisco Bay had higher rates of travel to the Copper River Delta than those banded at Grays Harbor. The later a bird left a capture site, the faster it traveled to the Copper River Delta. Length of stay at the Copper River Delta was inversely related to arrival date. We did not find any effect of sex on travel rate or length of stay. Combining the results of this study with our previous work on Western Sandpipers, Calidris mauri (Cabanis, 1875), reveals variation of migration strategies used within and among shorebird species along the eastern Pacific Flyway. ?? 2004 NRC.

Canadian Journal of Zoology↗

USGS2004

Haldane's rule and American black duck x mallard hybridization

Species ratios and rangewide distributions of American black ducks (Anas rubripes Brewster, 1902) and mallards (Anas platyrhynchos L., 1758) have undergone recent changes. Mechanisms behind these changes are not known with certainty, but recent investigations have focused on the possibility of competitive exclusion and the consequences of hybridization. Consequences of hybridization have been difficult to assess because of the difficulty in identifying hybrids beyond the F1 generation and lack of means to quantify introgression in wild populations. We documented a postmating isolating mechanism between the two species that follows Haldane's rule in controlled, interspecific matings in captive populations. Hybridization reduces the proportion of F1 females available to return to the breeding grounds in the subsequent year. This effect, although likely small in overall population consequences in any year, may be of local significance and may contribute to recent reports of range shifts in both American black ducks and mallards. ?? 2004 NRC.

Canadian Journal of Zoology↗

USGS2005

Landscape resistance to frog movements

An animal's capacity to recolonize a patch depends on at least two components: its ability to detect the patch and its ability to reach it. However, the disruption of such processes by anthropic disturbances could explain low animal abundance patterns observed by many investigators in certain landscapes. Through field experiments, we compared the orientation and homing success of northern green frogs (Rana clamitans melanota Rafinesque, 1820) and northern leopard frogs (Rana pipiens Schreber, 1782) translocated across disturbed or undisturbed surfaces. We also monitored the path selected by individuals when presented with a choice between a short distance over a disturbed surface and a longer, undisturbed route. Finally, we measured the water loss and behaviour of frogs on substrates resulting from anthropogenic disturbances and a control. When presented with a choice, 72% of the frogs avoided disturbed surfaces. Although able to orient towards the pond of capture when translocated on disturbed surfaces, frogs had a lower probability of homing successfully to the pond than when translocated at a similar distance on an undisturbed surface. Frogs lost the most water on substrates associated with disturbance and in the absence of cover. Our data illustrate that anthropically disturbed areas devoid of cover, such as mined peatlands and agricultural fields, disrupt the ability of frogs to reach habitat patches and are likely explanations to their reduced abundance patterns in such environments. ?? 2005 NRC Canada.

Canadian Journal of Zoology↗

USGS2005

Demography and decline of the Mentasta caribou herd, Alaska

We evaluated population trends in the Mentasta caribou ( Rangifer tarandus (L., 1758)) herd in Wrangell – St. Elias National Park and Preserve, Alaska, from 1990 to 1997 and determined factors contributing to its decline. We postulated that predation-related mortality of adult females and juveniles was the proximate cause of the decline, and that survival of juvenile caribou reflected interactions with winter severity, calving distribution, timing of births, density of caribou, and physical condition of neonates at birth. The population declined at its greatest rate from 1990 to 1993 ( r = –0.32) and at a lower rate from 1994 to 1997 ( r = –0.09). Recruitment (number of calves/100 females during September) averaged 4/100 during the rapid population decline from 1990 to 1993 and 13/100 from 1994 to 1997. Parturition rate of adult females ranged from 65% to 97%. Survival of adult females and juveniles ranged from 0.77 to 0.86 and from 0.00 to 0.22, respectively. Approximately 43%, 59%, and 79% of all juvenile mortality occurred by 1, 2, and 4 weeks of age, respectively. We confirmed predation-related mortality as the primary proximate cause of population decline, with gray wolves ( Canis lupus L., 1758), bears (species of the genus Ursus L., 1758), and other predators accounting for 57%, 38%, and 5%, respectively, of all juvenile mortality, and bears causing disproportionate mortality among 0- to 1-week-old neonates. We supported the hypotheses that timing of birth and habitat conditions at the birth site, particularly mottled snow patterns, affected vulnerability and survival of neonates, and birth mass affected survival of juveniles through summer. We speculate that the population will continue to decline before reaching a low-density equilibrium that is sustained by density-dependent changes in the functional responses of predators.

Alaska↗

USGS2006

Monitoring planktivorous seabird populations: Validating surface counts of crevice-nesting auklets using mark-resight techniques

Least Auklets ( Aethia pusilla (Pallas, 1811)) are the most abundant species of seabird in the Bering Sea and offer a relatively efficient means of monitoring secondary productivity in the marine environment. Counting auklets on surface plots is the primary method used to track changes in numbers of these crevice-nesters, but counts can be highly variable and may not be representative of the number of nesting individuals. We compared average maximum counts of Least Auklets on surface plots with density estimates based on mark–resight data at a colony on St. Lawrence Island, Alaska, during 2001–2004. Estimates of breeding auklet abundance from mark–resight averaged 8 times greater than those from maximum surface counts. Our results also indicate that average maximum surface counts are poor indicators of breeding auklet abundance and do not vary consistently with auklet nesting density across the breeding colony. Estimates of Least Auklet abundance from mark–resight were sufficiently precise to meet management goals for tracking changes in seabird populations. We recommend establishing multiple permanent banding plots for mark–resight studies on colonies selected for intensive long-term monitoring. Mark–resight is more likely to detect biologically significant changes in size of auklet breeding colonies than traditional surface count techniques.

Canadian Journal of Zoology↗

USGS2006

Experimental infection of the endangered bonytail chub (Gila elegans) with the Asian fish tapeworm (Bothriocephalus acheilognathi): impacts on survival, growth, and condition

Bothriocephalus acheilognathi Yamaguti, 1934, a tapeworm known to be pathogenic to some fish species, has become established in the endangered humpback chub (Gila cypha Miller, 1964) in Grand Canyon, USA, following the tapeworm’s introduction into the Colorado River system. The potential impact of this tapeworm on humpback chub was studied by exposing the closely related bonytail chub (Gila elegans Baird and Girard, 1853) to the parasite under a range of conditions that included potential stressors of humpback chub in their natal waters, such as abrupt temperature change and a limited food base. Survival of infected fish under low food rations was considerably lower than that of control fish, and mortality of infected fish began 20 days earlier. Growth of infected fish was significantly reduced, and negative changes in health condition indices were found. No significant negative impacts were revealed from the synergistic effects between temperature shock and infection. Bothriocephalus acheilognathi does present a potential threat to humpback chub in Grand Canyon and should be considered, along with conventional concerns involving altered flow regimes and predation, when management decisions are made concerning conservation of this endangered species.

Arizona↗

USGS2007

Effect of lipid extraction on analyses of stable carbon and stable nitrogen isotopes in coastal organisms of the Aleutian archipelago

We tested whether extracting lipids reduced confounding variation in ??13C and ??15N values by analyzing paired lipid-extracted (LE) and non-lipid-extracted (NLE) samples of bald eagle (Haliaeetus leucocephalus (L., 1766)) whole eggs, muscle tissue from nine seabird and one terrestrial bird species, muscle tissue from four marine fish species, and blue mussels (Mytilus edulis L., 1758) collected from the Aleutian archipelago, Alaska. Lipid extraction significantly increased ??13C by an average of 2.0??? in whole eggs, 0.8??? in avian muscle, 0.2??? in fish muscle, and 0.6??? in blue mussels. Lower ??13C values in NLE samples covaried positively with lipid content across all sample types. Lower ??13C values in NLE samples were not correlated with lipid content within bald eagle eggs and blue mussels, but covaried positively with percent lipid in avian and fish muscles. Neither lipid extraction nor percent lipid significantly changed ??15N values for any sample type. Lower ??13C values in most NLE avian and fish muscle tissues should not confound interpretation of pelagic versus nearshore sources of primary production, but lipid extraction may be necessary when highly precise estimates of ??13C are needed. Lipid extraction may not be necessary when only ??15N is of interest. ?? 2007 NRC.

Canadian Journal of Zoology↗

USGS2007

Influence of land use and climate on wetland breeding birds in the Prairie Pothole region of Canada

Bird populations are influenced by a variety of factors at both small and large scales that range from the presence of suitable nesting habitat, predators, and food supplies to climate conditions and land-use patterns. We evaluated the influences of regional climate and land-use variables on wetland breeding birds in the Canada section of Bird Conservation Region 11 (CA-BCR11), the Prairie Potholes. We used bird abundance data from the North American Breeding Bird Survey, land-use data from the Prairie Farm Rehabilitation Administration, and weather data from the National Climatic Data and Information Archive to model effects of regional environmental variables on bird abundance. Models were constructed a priori using information from published habitat associations in the literature, and fitting was performed with WinBUGS using Markov chain Monte Carlo techniques. Both land-use and climate variables contributed to predicting bird abundance in CA-BCR11, although climate predictors contributed the most to improving model fit. Examination of regional effects of climate and land use on wetland birds in CA-BCR11 revealed relationships with environmental covariates that are often overlooked by small-scale habitat studies. Results from these studies can be used to improve conservation and management planning for regional populations of avifauna. ?? 2007 NRC.

Canadian Journal of Zoology↗

USGS2007

Variation in winter diet of southern Beaufort Sea polar bears inferred from stable isotope analysis

Ringed seals ( Phoca hispida Schreber, 1775 = Pusa hispida (Schreber, 1775)) and bearded seals ( Erignathus barbatus (Erxleben, 1777)) represent the majority of the polar bear ( Ursus maritimus Phipps, 1774) annual diet. However, remains of lower trophic level bowhead whales ( Balaena mysticetus L., 1758) are available in the southern Beaufort Sea and their dietary contribution to polar bears has been unknown. We used stable isotope ( 13 C/ 12 C, δ 13 C, 15 N/ 14 N, and δ 15 N) analysis to determine the diet composition of polar bears sampled along Alaska’s Beaufort Sea coast in March and April 2003 and 2004. The mean δ 15 N values of polar bear blood cells were 19.5&permil; (SD = 0.7&permil;) in 2003 and 19.9&permil; (SD = 0.7&permil;) in 2004. Mixing models indicated bowhead whales composed 11%–26% (95% CI) of the diets of sampled polar bears in 2003, and 0%–14% (95% CI) in 2004. This suggests significant variability in the proportion of lower trophic level prey in polar bear diets among individuals and between years. Polar bears depend on sea ice for hunting seals, and the temporal and spatial availabilities of sea ice are projected to decline. Consumption of low trophic level foods documented here suggests bears may increasingly scavenge such foods in the future.

Canadian Journal of Zoology↗

USGS2007

Mass dynamics of wintering Pacific Black Brant: Body, adipose tissue, organ, and muscle masses vary with location

We compared body size and mass of the whole body, organs, adipose tissue, and muscles of adult Pacific Black Brant ( Branta bernicla nigricans (Lawrence, 1846)) collected concurrently in Alaska and Baja California during the fall, winter, and spring of 2002–2003. Head and tarsal lengths of males were similar between sites and slightly larger for females in Alaska than in Baja California. Brant appear to operate under similar physiological bounds, but patterns of nutrient allocation differ between sites. Birds wintering in Alaska lost similar amounts of adipose tissue during early winter as birds in Baja California gained during late winter before migration. Masses of the body, adipose tissue, and flight muscles during mid-winter were similar between sites. Seasonal adipose tissue deposition may, therefore, equally favor winter residency or long-distance migration. Gonad and liver masses increased in late winter for birds in Alaska but not for those in Baja California, suggesting birds wintering in Baja may delay reproductive development in favor of allocating reserves needed for migration. Phenotypic flexibility allows Brant to use widely divergent wintering sites. The wintering location of Brant likely depends more upon changes in environmental conditions and food availability, than upon physiological differences between the two wintering populations.

Alaska, Baja California↗

USGS2008

Discrimination of carbon and nitrogen isotopes from milk to serum and vibrissae in Alaska Steller sea lions (Eumetopias jubatus)

Knowledge of diet-tissue stable isotope discrimination is required to properly interpret stable isotope values and to identify possible diet shifts, such as might be expected from nursing through weaning. This study compared ??13C and ??15N of paired serum and vibrissal roots with those of ingested milk (n = 52) from free-ranging Steller sea lion (Eumetopias jubatus (Schreber, 1776)) pups (1-11 months) and juveniles (14-27 months) to estimate diet-tissue discrimination. Mean 15N enrichment from ingested milk to serum was 2.1??? ?? 0.6%??? and ??15N at the root of the vibrissae (representing current growth) were not significantly different from serum values. Milk was enriched for mean 13C by 5.0??? ?? 1.0%??? and 7.3??? ?? 1.2??? relative to serum and vibrissal roots, respectively, which was due to the presence of 13C-depleted lipids in milk. This was confirmed by lipid extraction from a subset of milk and serum samples, resulting in a 5.8??? ?? 1.0??? change only in milk. This study established that vibrissal roots and serum are reflective of a milk diet with approximately 2.0??? 15N enrichment, and vibrissal roots reflect serum and lipid-extracted milk values with approximately 2.0??? 13C enrichment. These discrimination factors are important to establish for stable isotope studies assessing diet shifts. ?? 2008 NRC.

Canadian Journal of Zoology↗

USGS2008

Dietary biomagnification of organochlorine contaminants in Alaskan polar bears

Concentrations of organochlorine contaminants in the adipose tissue of polar bears (Ursus maritimus Phipps, 1774) vary throughout the Arctic. The range in concentrations has not been explained fully by bear age, sex, condition, location, or reproductive status. Dietary pathways expose polar bears to a variety of contaminant profiles and concentrations. Prey range from lower trophic level bowhead whales (Balaena mysticetus L., 1758), one of the least contaminated marine mammals, to highly contaminated upper trophic level ringed seals (Phoca hispida (Schreber, 1775)). We used ??15N and ??13C signatures to estimate the trophic status of 42 polar bears sampled along Alaska's Beaufort Sea coast to determine the relationship between organochlorine concentration and trophic level. The ?? 15N values in the cellular portions of blood ranged from 18.2% to 20.7%. We found strong positive relationships between concentrations of the most recalcitrant polychlorinated biphenyls (PCBs) and ??15N values in models incorporating age, lipid content, and ??13C value. Specifically these models accounted for 67% and 76% of the variation in PCB153 and oxychlordane concentration in male polar bears and 85% and 93% in females, respectively. These results are strong indicators of variation in diet and biomagnification of organochlorines among polar bears related to their sex, age, and trophic position. ?? 2008 NRC.

Canadian Journal of Zoology↗

USGS2008

Individual variation affects departure rate from the natal pond in an ephemeral pond-breeding anuran

Frogs exhibit extreme plasticity and individual variation in growth and behavior during metamorphosis, driven by interactions of intrinsic state factors and extrinsic environmental factors. In northern red-legged frogs (Rana aurora Baird and Girard, 1852), we studied the timing of departure from the natal pond as it relates to date and size of individuals at metamorphosis in the context of environmental uncertainty. To affect body size at metamorphosis, we manipulated food availability during the larval stage for a sample (317) of 1045 uniquely marked individuals and released them at their natal ponds as newly metamorphosed frogs. We recaptured 34% of marked frogs in pitfall traps as they departed and related the timing of their initial terrestrial movements to individual properties using a time-to-event model. Median age at first capture was 4 and 9 days postmetamorphosis at two sites. The rate of departure was positively related to body size and to date of metamorphosis. Departure rate was strongly negatively related to time elapsed since rainfall, and this effect was diminished for smaller and later metamorphosing frogs. Individual variation in metamorphic traits thus affects individuals' responses to environmental variability, supporting a behavioral link with variation in survival associated with these same metamorphic traits. ?? 2008 NRC.

Canadian Journal of Zoology↗

USGS2008

Genetic characterization of Kenai brown bears (Ursus arctos): Microsatellite and mitochondrial DNA control region variation in brown bears of the Kenai Peninsula, south central Alaska

We collected data from 20 biparentally inherited microsatellite loci, and nucleotide sequence from the maternally inherited mitochondrial DNA (mtDNA) control region, to determine levels of genetic variation of the brown bears (Ursus arctos L., 1758) of the Kenai Peninsula, south central Alaska. Nuclear genetic variation was similar to that observed in other Alaskan peninsular populations. We detected no significant inbreeding and found no evidence of population substructuring on the Kenai Peninsula. We observed a genetic signature of a bottleneck under the infinite alleles model (IAM), but not under the stepwise mutation model (SMM) or the two-phase model (TPM) of microsatellite mutation. Kenai brown bears have lower levels of mtDNA haplotypic diversity relative to most other brown bear populations in Alaska. ?? 2008 NRC.

Canadian Journal of Zoology↗

USGS2008

Wolf body mass cline across Minnesota related to taxonomy?

Recent genetic studies suggest that in northern Minnesota two species of wolves (Canis lupus L., 1758 or western wolf and Canis lycaon Schreber, 1775 (= Canis rufus Audubon and Bachman, 1851) or eastern wolf) meet and hybridize. However, little morphological information is available about these two types of wolves in Minnesota. We analyzed the mass of 950 female wolves and 1006 males older than 1 year from across northern Minnesota and found that it increased from 26.30 ?? 0.56 kg (mean ?? SE) for females and 30.60 ?? 0.72 kg for males in northeastern Minnesota to 30.01 ?? 0.43 kg for females and 35.94 ?? 0.45 kg for males in northwestern Minnesota (females: r2 = 0.79, P < 0.02; males: r2 = 0.63, P = 0.06). These mass differences add morphological information to the identities of eastern and western wolves and support the view that ranges of the two species meet in Minnesota. ?? 2008 NRC.

Canadian Journal of Zoology↗

USGS2009

Seasonal movements and home ranges of white-tailed deer in north-central South Dakota

Knowledge of movement patterns of white-tailed deer ( Odocoileus virginianus (Zimmermann, 1780)) inhabiting landscapes intensively modified by agricultural systems is important to the present and future understanding of deer ecology. Little information exists regarding daily and seasonal movements of white-tailed deer in north-central South Dakota. Therefore, our goal was to determine movement patterns and home-range use of female white-tailed deer in north-central South Dakota. From January 2005 to January 2007, 29 adult (>18 months) and 13 yearling (8–18 months) white-tailed deer were monitored for movement using radiotelemetry. We collected 2822 locations, calculated 76 home ranges, and documented 50 seasonal movements. Mean migration distance between summer and winter home ranges was 19.4 km (SE = 2.0 km). Mean 95% home-range size was 10.2 km 2 (SE = 1.2 km 2 , n = 27) during winter and 9.2 km 2 (SE = 1.0 km 2 , n = 49) during summer. Ambient temperature appeared to be a primary cause of seasonal migration. Additionally, movements exhibited by white-tailed deer in north-central South Dakota were influenced by a highly fragmented landscape dominated by row crops and pasture or grassland.

South Dakota↗