bluuebunny/crossref_metadata_2025 huggingface dataset:
Energetics of hummingbird foraging at low ambient temperature
Authors: Gass C L , Romich M T , Suarez R K
Published: April 2011

Because of their small size and the high energetic costs of hovering and forward flight, hummingbirds achieve the highest mass-specific metabolic rates known among vertebrates. Rufous hummingbirds (Selasphorus rufus) stop to refuel on floral nectar in subalpine meadows as they migrate south from British Columbia to Mexico. In such habitats they face the challenge of achieving daily net energy gain despite the high energetic costs of flight and thermoregulation at near-freezing morning temperatures. Hummingbirds provided with 15 or 20% sucrose while subjected to these conditions for 4 h in the laboratory did not remain in energy balance and lost mass. However, they achieved energy balance or net energy gain on 30% sucrose. Because these sucrose concentrations are within the range observed in the nectar of hummingbird-visited flowers, the results suggest that the energetic cost of thermoregulation may influence the coevolution of hummingbirds and flowers. Hummingbirds maintaining energy balance at low ambient temperature via high foraging frequencies and high rates of energy intake can sustain average metabolic rates of about 250 W/kg over a 4-h period. These are the highest metabolic rates known among vertebrates at which rates of dietary energy intake equal rates of energy expenditure.
Threat of predation: do ungulates behave aggressively towards different members of a coyote pack?
Authors: Gese Eric M
Published: April 2011

Wild ungulates have evolved a variety of antipredator strategies to deter or escape predation by carnivores. Among wild canids, the dominant pair of a pack often initiates attacks upon prey. Previous observations in Yellowstone National Park, Wyoming, showed that the alpha pair in a coyote (Canis latrans) pack most often leads attacks on ungulates during winter. We were interested in determining whether ungulates can distinguish (perhaps by body size or posture) which members of a coyote pack are the alpha individuals, and whether they initiate and direct aggressive behavior towards those members of the pack that pose the greatest threat of predation to themselves and (or) their offspring. During 2507 h of behavioral observations on 54 coyotes between January 1991 and June 1993, we observed 51 interactions between coyotes and adult elk (Cervus elaphus), bison (Bison bison), and pronghorn antelope (Antilocapra americana) in Yellowstone National Park. The interactions analyzed here are those in which the ungulate appeared to initiate aggressive behavior towards the coyote(s) and were not a response to an attack by the predators. We found that aggression by ungulates towards coyotes was highest during the summer months, when calves and fawns were present; female ungulates were more frequently aggressive than males. The frequency of aggression of adult ungulates towards small and large groups of coyotes was equal to the frequency of occurrence of these groups. Ungulates directed aggressive behavior more frequently towards alpha coyotes and were less aggressive towards beta coyotes and pups. Large ungulates, particularly elk and bison, appeared to perceive that alpha coyotes posed a greater threat to themselves and their offspring. The smaller ungulate, the pronghorn antelope, directed aggressive behavior equally towards all coyotes. Adult ungulates were probably responding to the larger body size of the alpha coyotes and the tendency of alpha coyotes to travel at the front of the pack.
Bears and ants: myrmecophagy by brown bears in central Scandinavia
Authors: Swenson Jon E , Jansson Anna , Riig Raili , Sandegren Finn
Published: April 2011

To determine general patterns of myrmecophagy in bears, we tested hypotheses regarding selection of ant species, factors important to bears when selecting ant species, factors influencing seasonal use of ants, and foraging behavior of brown bears (Ursus arctos) in central Sweden. Ants were an important food for these bears, constituting 12, 16, and 4% of fecal volume in spring, summer, and autumn, respectively. Ants were abundant, 30.5-38.5 tonnes per bear, and bears excavated 8-33% (mean 23%) of the mounds of red forest ants annually. Carpenter ants (Camponotus herculeanus) were highly preferred. Among mound-building red forest ants, the Formica aquilonia/polyctena complex was preferred over Formica exsecta and Formica lugubris. The ants selected by bears had high digestible energy and low formic acid content and behaved passively when the colony was disturbed. Colony size and density may also have influenced the selection of ants. Seasonal use of ants was related not to the availability of pupae or the quality of plant foods but probably to the availability of other foods. Bears consumed only a small proportion of the ants, 4000-5000, each time they opened a mound, probably because of rapidly increasing difficulty in capturing them after the colony was attacked. Eurasian brown bears feed more on ants than North American bears do, perhaps because of greater availability of large colonies of red forest ants. Carpenter ants may have been especially available in our study area following intensive clear-cutting.
Descriptive and functional morphometry of skeletal muscle fibres in wild birds
Authors: Torrella J R , Fouces V , Viscor G
Published: April 2011

The fibre types of four forelimb and two hind-limb muscles involved in locomotion were morphometrically analyzed in three species of wild birds: the mallard (Anas platyrhynchos), common coot (Fulica atra), and yellow-legged gull (Larus cachinnans). Fibre cross-sectional area and perimeter, maximal diffusion distance, and number of capillaries per fibre were measured and the functional implications and physiological demands of the muscles of each species were inferred. In general, all morphometric values were lower in oxidative fibres than in anaerobic fibres, indicating that the supply of oxygen and metabolites available to aerobically working muscles is enhanced. The lower level of activity required during gliding as opposed to flapping flight, and the need to maintain the wings in an outstretched position, presumably by means of isometric contractions, may explain the greater size of the oxidative fibres of the pectoralis and scapulotriceps muscles of the gull. In contrast, the high oxidative demand imposed on mallards and coots by sustained flapping flight is met by small oxidative fibres, possibly at the expense of a reduction in the ability of each fibre to generate force. Anaerobic fibres of the gastrocnemius muscle had greater cross-sectional areas in the mallard and coot than in the gull. This is interpreted as an adaptive response to force generation during burst locomotion, which is usually performed by both mallards and coots, in sharp contrast to the buoyant swimming and postural activities undertaken by gull's legs. The fast oxidative fibres of the gastrocnemius muscle were, in general, larger than those of the iliotibialis muscle in the three species, which matches the different mechanical and functional roles of these muscles during swimming.
Activity levels of enzymes of energy metabolism in heart and red muscle are higher in north-temperate-zone than in Amazonian teleosts
Authors: West J L , Bailey J R , Almeida-Val VMF , Val A L , Sidell B D , Driedzic W R
Published: April 2011

Fish living in the Amazon basin typically have body temperatures of about 30°C, whereas freshwater fishes of the north-temperate zone are eurythermal, with typical body temperatures of 10-20°C in summer. Enzyme activity levels in heart and red muscle of Amazonian species, which display various physiological mechanisms for dealing with hypoxic conditions, were compared with those in north-temperate-zone species. Five Amazonian species (acará-açu (Astronotus ocellatus), acari-bodó (Lipossarcus pardalis), tambaqui (Colossoma macropomum), tamoatá (Hoplosternum littorale), and pirarucu (Arapaima gigas)) and four north-temperate-zone species (American eel, bullhead, yellow perch, and rainbow trout) were studied. The Amazonian species included obligate and facultative air breathers. Activities of key indicator enzymes associated with carbohydrate metabolism, fatty acid metabolism, the citric acid cycle, and the electron-transport chain were determined. There was no obvious correlation between cardiac enzyme activity levels and the potential ability of fish to maintain blood oxygen levels in hypoxic water or the capacity of isolated heart preparations to survive anoxia. In heart, activity levels of hexokinase, phosphofructokinase, pyruvate kinase, lactate dehydrogenase, citrate synthase, cytochrome oxidase, and β-hydroxyacyl CoA dehydrogenase were about twice as high in north-temperate-zone species than in Amazonian species. Activities of red-muscle enzymes, especially those associated with aerobic fatty acid metabolism, were significantly higher in comparable north-temperate-zone species relative to Amazonian species. Increased enzyme activity levels in north-temperate-zone species relative to Amazonian species is considered to be an adaptation to generally lower body temperatures. This finding is consistent with earlier comparisions of Antarctic and north-temperate-zone species and with the results of studies of cold acclimation within north-temperate-zone fishes.
Do leks limit the frequency of aggressive encounters in fallow deer? Linking local male density and lek occurrence
Authors: Pélabon C , Komers P E , Höglund J
Published: April 2011

We suggest here that the formation of leks in ungulates is a mating tactic that aims at decreasing the number of aggressive encounters in which dominant males are involved when the local male density becomes too high. Using a simulation model, we show that the spatial stability of territories in leks should limit the number of aggressive encounters between males, despite a high number of males locally present. Data on the frequencies of aggressive interactions recorded in both lekking and nonlekking fallow deer (Dama dama) populations under different local male densities support our hypothesis.
Resistance to freezing in hatchling painted turtles (Chrysemys picta)
Authors: Packard Gary C , Lang Jeffrey W , Lohmiller Leslie D , Packard Mary J
Published: April 2011

We assessed the ability of hatchling painted turtles (Chrysemys picta) from northern Minnesota to resist freezing when exposed to conditions like those occurring in natural hibernacula (natal nests). We placed animals individually into artificial hibernacula constructed in jars of damp, loamy sand and then lowered the temperature to approximately -0.4°C, which was below the equilibrium freezing point for water in the soil (approximately -0.1°C) but above that for body fluids of the turtles (approximately -0.7°C). Next, ice was used to initiate freezing of water in the soil, after which the substratum was allowed to freeze to an equilibrium temperature of -0.4°C. The minimum temperature then was reduced by 1°C/day to either -2.5 or -6.5°C. The minimum was maintained for 9 days in the former treatment and for 5 days in the latter, so that turtles in both treatments were exposed for the same length of time to temperatures below the equilibrium freezing point for their body fluids. Some animals in each treatment were inoculated by ice crystals that penetrated their integument, and these turtles froze and died. However, many other animals resisted inoculation, remained unfrozen, and survived the test of tolerance. We conclude that hatchling painted turtles from northern Minnesota, like those from North Dakota, north-central Nebraska, and northern Illinois, withstand the cold of midwinter by supercooling and not by tolerating freezing.
Structure of the egg envelope of the haddock, Melanogrammus aeglefinus, and effects of microbial colonization during incubation
Authors: Morrison C , Bird C , O'Neil D , Leggiadro C , Martin-Robichaud D , Rommens M , Waiwood K
Published: April 2011

Haddock (Melanogrammus aeglefinus) eggs from an experimental culture were examined by electron and light microscopy to determine the structure of the egg envelope as preserved by various fixatives and to observe the effects on the envelope of microbial colonization during incubation. The egg envelope consisted of a featureless thin surface coating that readily dissociated into globules and was lost under standard fixation; a thin homogeneous surface layer penetrated by pores; a well-defined intact outer lamella 0.5-1.0 µm thick immediately beneath this; then about three more vaguely defined lamellae of similar thickness beneath which were several broader fibrillar layers. The total envelope thickness was 6.5-8.5 µm. Different fixatives primarily affected the appearance of the thin surface layer, which was well-preserved only by freezing or by fixation in glutaraldehyde with Alcian blue. Egg surfaces were colonized by microorganisms, regardless of early disinfection by various agents, and eggs at hatching were densely populated by bacteria, notably the filamentous genus Leucothrix. However, bacteria did not penetrate the egg envelope beyond the outer layers, where their presence was associated with surface erosion. A dense epiflora did not necessarily prevent normal development of the embryo, although very heavy infestations, as seen on eggs that failed to hatch, may cause suffocation. The envelope structure is compared with that of another gadoid which has been extensively studied and cultured, the Atlantic cod (Gadus morhua).
Sex differences in temporal parameters of partner preference in prairie voles (Microtus ochrogaster)
Authors: DeVries A Courtney , Carter C Sue
Published: April 2011

Prairie voles (Microtus ochrogaster) are monogamous rodents in which both sexes form social preferences for a familiar partner. This species exhibits many of the characteristics of monogamy, including long-term social bonds, mate guarding, and biparental care. Although the behaviors associated with the development of partner preferences are superficially similar in males and females, the present study documents sex differences in the temporal parameters of partner preferences in prairie voles. Following nonsexual cohabitation, female prairie voles formed partner preferences more quickly and these preferences lasted longer than in males. These data indicate that sex differences exist in the development and maintenance of social preferences and may reflect differences in the reproductive strategies of male and female prairie voles.
Diving behaviour of lactating harbour seals and their pups during maternal foraging trips
Authors: Bowen W D , Boness D J , Iverson S J
Published: April 2011

Female harbour seals (Phoca vitulina) undertake foraging trips during mid to late lactation. We show that they are accompanied by their pup during many of these foraging trips. Time-depth recorder data were obtained from 20 lactating females and 14 of their pups in 1995 and 1996 at Sable Island, Nova Scotia. Overall, females spent 55.4 ± 4.68% (mean ± SE) of their time at sea compared with 39.8 ± 2.29% for pups. Like those of their mothers, pups' dives occurred in clusters or bouts: 71.4 ± 4.4 dives, 2.5 ± 0.15 h in duration. Bouts of diving by females and pups began 0-3 days post partum. Mean dive duration of pups increased from about 1 to 1.5 min over the course of lactation, but was still shorter than that of adult females (1.5-2.25 min). Both females and pups appeared to dive within their theoretical aerobic dive limits (TADL) of 8.9 and 2.6-3.1 min, respectively. Up to 3.6% of dives by some pups may have exceeded their TADL. Pups appeared to compensate for their lesser diving ability by making more and shorter dives per bout than females, particularly during early lactation.
Fish prey of the sympatric Galápagos fur seals and sea lions: seasonal variation and niche separation
Authors: Dellinger Thomas , Trillmich Fritz
Published: April 2011

Analysis of fish otoliths in scats and vomits of Galápagos fur seals (Arctocephalus galapagoensis) and Galápagos sea lions (Zalophus californianus wollebaeki) was used to determine the numerical composition of the diets for the post-El Niño year 1983, the cold seasons in 1984 and 1985, and the warm season in 1986. Between 84 and 99% of all otoliths in fur seal scats were from myctophids and bathylagids. The fur seals' diet included 26 species. Only 3 species contributed more than 1% of otoliths. No seasonal differences in diet were found. Sea lion samples contained a mean of 14 otoliths. Sardines (Sardinops sagax) contributed 75-85% of otoliths. Sea lions preyed on 24 species, but only 3 surpassed 1% abundance. Seasonality was not reflected in the sea lions' diet. After the 1982-1983 El Niño, the diets of both species deviated from those in all other years of the study. Food-niche overlap between the two sympatric species was almost non-existent. This is hard to understand, based on our knowledge of the diving capabilities of the two species, but reflects the fact that Galápagos fur seals are nighttime foragers and sea lions are daytime foragers.
Regurgitative food transfer among wild wolves
Authors: Mech L David , Wolf Paul C , Packard Jane M
Published: April 2011

Few studies of monogamous canids have addressed regurgitation in the context of extended parental care and alloparental care within family groups. We studied food transfer by regurgitation in a pack of wolves on Ellesmere Island, North West Territories, Canada, during 6 summers from 1988 through 1996. All adult wolves, including yearlings and a post-reproductive female, regurgitated food. Although individuals regurgitated up to five times per bout, the overall ratio of regurgitations per bout was 1.5. Pups were more likely to receive regurgitations (81%) than the breeding female (14%) or auxiliaries (6%). The breeding male regurgitated mostly to the breeding female and pups, and the breeding female regurgitated primarily to pups. The relative effort of the breeding female was correlated with litter size (Kendall's τ = 0.93, P = 0.01).
Genetic and morphological variability in cestodes of the genus Proteocephalus: geographical variation in Proteocephalus percae populations
Authors: Hanzelová Vladimíra , nábel Viliam , Král'ová Ivica , Scholz Tomá , D'Amelio Stefano
Published: April 2011

Genetic and morphological variability was studied in the tapeworm Proteocephalus percae (Müller, 1780) (Cestoda: Proteocephalidae), a parasite of perch (Perca fluviatilis L.). Geographic variation in isoenzyme patterns, random amplified polymorphic DNA (RAPD) profiles, and morphological characters were found within six natural populations of P. percae from Slovakia and Switzerland. All approaches used showed that similarity was substantially higher among Swiss populations than among Slovak populations. Proteocephalus percae specimens from the Dobiná water reservoir (Slovakia) differed significantly from all other population sample sets in that they exclusively expressed the genotype Acp92/Acp92 and possessed a specific RAPD profile after amplification with the primer p78 and distinct measurements of the scolex (scolex width and apical sucker). The unique position of the P. percae population from Dobiná could be related to the contamination of this locality with heavy metals (cadmium), through the possible impact of these metals on the alterations observed. The taxonomic relevance and stability of the morphological characters related to the scolex in the Proteocephalus tapeworm group is confirmed.
Rates of inbreeding in the androdioecious clam shrimp Eulimnadia texana
Authors: Weeks S C , Zucker N
Published: April 2011

Populations of the clam shrimp Eulimnadia texana exhibit androdioecy, which is a mixed mating system composed of males and self-compatible hermaphrodites. It has been suggested that such mating systems are evolutionarily unstable, and yet most populations of E. texana appear to exhibit both outcrossing and selfing (a mixed mating strategy). Genetic and sex-ratio features of seven populations of these clam shrimp confirm that the majority of these populations show a mixture of inbreeding and outcrossing modes of reproduction. Additionally, we suggest that the relationship of inbreeding rate with male frequency indicates that mating is not random, as was suggested in a previous model of the mating system of E. texana.
Herring schooling manoeuvres in response to killer whale attacks
Authors: Nøttestad Leif , Axelsen Bjørn Erik
Published: April 2011

The antipredator behaviour of overwintering Norwegian spring-spawning herring (Clupea harengus L.) was investigated during repeated attacks by killer whales (Orcinus orca L.) in Tysfjord in northwestern Norway. The observations were made using a high-resolution (455 kHz) multibeam sonar. Ten different types of predator-prey interactions were recorded during 54 observed events (an average of one antipredator event every 3.9 min). Antipredator responses included "split," "hourglass," "vacuole," "bend," "dive," "herd," and "fountain." Large attacked schools demonstrated a different repertoire of antipredator manoeuvres than small ones and were less likely to be attacked. Despite being located in the vicinity of the whales, herring schools with a cross section exceeding 460 m2 were not attacked by killer whales. Attacked schools were significantly more circular (p < 0.0001) and had higher relative densities (p < 0.05) than schools that were not attacked.
Effect of seasonal differences in dietary meat intake on changes in body mass and composition in wild and captive brown bears
Authors: Hilderbrand G V , Jenkins S G , Schwartz C C , Hanley T A , Robbins C T
Published: April 2011

The influence of seasonal dietary meat intake on changes in body mass and composition in wild and captive brown bears (Ursus arctos) was investigated because the importance and availability of meat to brown bear populations is currently an important management consideration in several North American ecosystems. Adult female brown bears on the Kenai Peninsula, Alaska, utilized meat heavily in both spring and fall. Meat accounted for 76.2 ± 26.0% (mean ± 1 SD; primarily moose carrion and calves) of assimilated carbon and nitrogen in the spring and 80.4 ± 22.2% (primarily salmon) in the fall. Mass increases in the spring (71.8 ± 28.2%) were mostly lean body mass, but increases in the fall (81.0 ± 19.5%) were primarily fat. Daily intake by captive brown bears fed meat ad libitum during 12-day trials was positively related to body mass. Mass change was positively related to intake in both seasons, but the composition of the gain varied by season, with spring gains primarily lean body mass (64.2 ± 9.4%), while fall gains were 78.8 ± 19.6% lipid. Absolute rates of gain by wild bears occasionally equaled, but were usually much less than, those of captive bears. This was likely due to a combination of factors, which included the time required to locate and handle meat resources, the limited availability of or access to meat resources, and (or) the duration of meat resource availability. Estimated intake by bears not feeding selectively on high-energy components of moose and salmon were 8.5 ± 1.5 kg/day and 541 ± 156 kg/year and 10.8 ± 4.6 kg/day and 1003 ± 489 kg/year, respectively. Intake would drop by as much as 58% for bears feeding exclusively on salmon roe. Management strategies for areas with brown bears that consume significant amounts of meat should address the perpetuation and availability of these meat resources.
Ecology of two large, net-spinning caddisfly species in a mountain stream: distribution, abundance, and metabolic response to a thermal gradient
Authors: Lowe Winsor H , Hauer F Richard
Published: April 2011

We quantified the distribution and abundance of larvae of two species of caddisfly, Parapsyche elsis and Arctopsyche grandis (Trichoptera: Hydropsychidae), at 8 sites along a 560-m elevational gradient and a 36-km longitudinal gradient in a pristine mountain stream. Both species are widely distributed throughout the northern Rocky Mountains and have similar 2-year life-spans, similar catch-nets, and similar microhabitat requirements. However, the reach-scale distribution patterns were distinctly dissimilar. Parapsyche elsis larvae were most abundant in the upper reaches of the study stream, while A. grandis larvae were found only in lower stream segments. We examined the correlation between the stream gradient and the environmental variables that likely influence the distributions of these insects: temperature, food quantity and quality, current velocity, and substratum cobble size. Only those variables relating to temperature (i.e., annual degree-days, summer maximum) correlated with stream elevational and longitudinal gradients. Laboratory examination revealed a relationship between zones of temperature independence in the metabolism-temperature response of both species, maximum summer temperatures in the stream, and distribution of the two species. We propose that the physiological response of these species to stream temperature, with resulting bioenergetics, is the probable mechanism structuring the stream distribution and abundance patterns of these species.
Body mass and dive duration in alcids and penguins
Authors: Watanuki Yutaka , Burger Alan E
Published: April 2011

Interspecific allometric equations for dive duration were calculated for two groups of wing-propelled divers: penguins, which specializing in diving, and alcids, which balance demands for aerial flying with those of diving. The equations for maximum dive duration (min) were 1.433M0.702and 3.612M0.735(where M is body mass in kilograms) for penguins (10 species) and alcids (9 species), respectively, hence did not support a simple oxygen store/usage hypothesis based on the prediction that the mass exponent of aerobic dive limit is close to 0.25. Equations for feeding dives were 0.569M0.712and 1.094M0.391in penguins (9 species) and alcids (10 species), respectively. The allometric exponent for the duration of feeding dives for penguins did not match the predicted value of 0.25, but that for alcids did not differ significantly from this value. Alcids exhibited a maximum dive duration 2.5 times longer than that for penguins after mass effects were controlled for. The size of oxygen stores and metabolic rates based on laboratory studies of penguins and alcids failed to explain the longer dive duration in alcids than in penguins.
Seasonal variability in brown tree snake (Boiga irregularis) response to lures
Authors: Shivik John A , Wright William G , Clark Larry
Published: April 2011

In continuing investigations of brown tree snake, Boiga irregularis, attraction to carrion odor, we hypothesized that the attractiveness of live or dead and visually apparent or concealed lures varies seasonally. We determined that lure condition (live or dead mouse lures) and sensory cues (visually apparent or concealed lure) interact among wet and dry seasons. Concealed carrion lures were more effective during the dry season than the wet season, but the effectiveness of live mouse lures showed less seasonal variability. We identified weather variables that covary with observed seasonal trends in capture rates and investigated the influence of recent feeding on snake response to lures. Data suggest that live mouse lure capture rates correlate with wind and dead mouse capture rates correlate with rainfall. Recently fed and satiated snakes were not less responsive to lures but were less active than unfed snakes. Snakes held for over 2 years were less responsive than recently captured snakes. More intensive studies will be required to determine cause-and-effect relationships between lure type, seasonality, and snake behavior.
The disappearance of subordinate foundresses in paper wasps: eviction by nestmates or reproductive strategy?
Authors: Gamboa George J , Savoyard Janet L , Panek Laura M
Published: April 2011

Videotaped observations (371.3 h) were conducted in 1995, 1996, and 1997 on 50 multiple-foundress colonies of the social wasp Polistes fuscatus. Observations were made during the mid-preworker, late-preworker, and early-postworker stages of the colony cycle. The vast majority of lost subordinate cofoundresses (62 of 77) disappeared during the time interval from 2 weeks before to 4 weeks after the emergence of the first workers. The loss of subordinates did not appear to be the result of senescence or foraging-related mortality. Lost subordinates were from productive and presumably healthy colonies. In colonies containing two or more subordinates, lost subordinates had significantly greater dominance ranks than expected. There was no behavioural evidence that lost subordinates were evicted from their colony by queens, other subordinate foundresses, or workers. Lost subordinates were not observed to renest, join sister colonies, or adopt orphaned nests. Our results indicate that lost subordinates leave colonies of their own volition. Indirect evidence from other studies suggests that subordinates may disperse and usurp colonies from other sites.
Response of northwestern chipmunks (Tamias amoenus) to variable habitat structure in young lodgepole pine forest
Authors: Sullivan Thomas P , Klenner Walt
Published: April 2011

This study was designed to test the hypothesis that large-scale habitat alteration by stand thinning over a range of densities would increase the abundance and related population dynamics of northwestern chipmunks (Tamias amoenus) in young lodgepole pine (Pinus contorta) forest. Replicate study areas were located near Penticton, Kamloops, and Prince George in south-central British Columbia, Canada. Each study area had three stands thinned to densities of approximately 500 (low), 1000 (medium), and 2000 (high) stems/ha, with an unthinned young pine stand and an old-growth pine stand for comparison. Chipmunk populations were sampled intensively in thinned stands from 1989 to 1991 and in the unthinned and old-growth stands from 1990 to 1991. Habitat structure was sampled in all stands in 1990. For herbs and shrubs, the crown volume index values were similar among stands; for trees, this index was lowest for the low-density stands, with the index for all three thinned stands being lower than that for the unthinned stands. Species diversity and the structural diversity of vegetation were similar among stands. The abundance of chipmunks was significantly higher in low-density than in high-density thinned stands at Penticton (1.3-1.9 times higher) and Prince George (2.4-3.8 times higher) but not at Kamloops. Chipmunks were less abundant in old-growth stands than in the other four treatment stands. Breeding performance and recruitment followed the same pattern as abundance. Chipmunk survival was generally similar among stands. There were heavier chipmunks in the low-density stands in some years at Penticton. Northwestern chipmunks appear to prefer "open" habitats generated by heavy thinning of young lodgepole pine stands. This result was achieved in three different forest ecological zones and may enhance the overall forest ecosystem.
Habitat use by Pileated Woodpeckers at two spatial scales in eastern Canada
Authors: Savignac Carl , Desrochers André , Huot Jean
Published: April 2011

To study the multiple spatial scale pattern of habitat use by Pileated Woodpeckers (Dryocopus pileatus L.), we compared the vegetation characteristics at used sites with those at unused sites at macrohabitat (154 ha radius plots) and microhabitat (ca. 0.04 ha radius plots) scales in the La Mauricie region of Québec. Used macrohabitats were those in which woodpeckers were detected at playback stations. Used microhabitats corresponded to sites showing signs of foraging (i.e., excavated cavities). Pileated Woodpeckers responded to vegetation structure at both scales sampled. Macrohabitats used by woodpeckers had relatively low percentages of mixed shade-intolerant hardwood stands, coniferous stands, and stands of relatively low stem density and tree height, but included high percentages of 51- to 90-year-old stands. Microhabitats used by woodpeckers were characterized most strongly by a high density of large snags but also by a high density of small-diameter snags and a low density of shade-intolerant hardwood trees and coniferous trees [Formula: see text]30 cm diameter at breast height. The concordance between the observed and predicted use of micro- and macro-habitat plots was independent of spatial scale (logistic regression, χ20.05,1 = 1.8, P = 0.18, n = 429), suggesting that habitats use by woodpeckers was influenced to a similar extent by habitat features measured at both spatial scales. Because Pileated Woodpeckers are likely to require specific habitat features at different spatial scales, forest-management guidelines intended to conserve this umbrella species should consider a multiple spatial scales approach.
Fleeing to unsafe refuges: effects of conspicuousness and refuge safety on the escape decisions of the lizardPsammodromus algirus
Authors: Martín José , López Pilar
Published: April 2011

Theoretical models of escape behavior suggest that the optimal distance at which an animal starts to flee (approach distance) increases with distance to the refuge. However, the extent of reliance on refuges may strongly affect this relationship. The lizard Psammodromus algirus escapes a predator by fleeing into leaf litter, which is very abundant but not a safe refuge because the predator could still locate and capture a concealed lizard. We test the hypothesis that escape decisions of this lizard species are based on the conspicuousness of individuals and the type of refuge used, rather than on the distance to cover per se. A field study showed that approach distance was not significantly correlated with distance to available refuges or distance actually fled. However, the type of microhabitat and the type of refuge used influenced the approach distance. Lizards started to flee earlier in microhabitats where they were presumably more visible to potential predators. Lizards ran to refuges that were similar in quality to, but farther from, the nearest available one. A longer flight may be needed to mislead the predator. However, because fleeing may be costly, the flight distance should be optimized. Thus, lizards ran farther and faster when they fled through unsafe microhabitats. Lizards with a low body temperature have lower escape performance and their approach distances should be greater. However, although air temperature affected escape speed, it was not significantly correlated with approach distance or flight distance. The relatively low reliance on refuges by P. algirus indicated that the expected relationship between escape decision and distance to the refuge did not exist. However, the results indicate that P. algirus optimizes its escape decisions according to the costs of fleeing and the costs of remaining.
Recent changes in the winter diet of murres (Uria spp.) in coastal Newfoundland waters
Authors: Rowe Sherrylynn , Jones Ian L , Chardine John W , Elliot Richard D , Veitch Brian G
Published: April 2011

We investigated the winter diet of murres (Uria spp.) in coastal Newfoundland waters in relation to environmental and ecological changes that have occurred in the Northwest Atlantic since the 1980s. We analyzed the contents of 371 stomachs (311 from Thick-billed Murres, Uria lomvia, and 60 from Common Murres, Uria aalge) of birds shot by hunters around the Newfoundland coast during the winters of 1996-1998. We observed that the frequency of empty stomachs was greater in our study than in a similar study conducted during 1984-1986. We found no difference in the proportion of fish in the diet between the 1980s and the 1990s, however, Arctic cod (Boreogadus saida; from 55 to 12%) and capelin (Mallotus villosus; from 28 to 6%) decreased in frequency of occurrence. The proportion of stomachs containing crustaceans and squid did not change between the 1980s and 1990s, but hyperiid amphipods (Parathemisto spp.) replaced euphausiids (Thysanoessa spp.) as the predominant crustacean. Changes in murre winter diet off the coast of Newfoundland corroborate other sources of information indicating that major changes in the distribution and biology of marine organisms occurred in the Northwest Atlantic during the 1990s.
The prevalence and ecology of the haematozoan parasites of European blackbirds, Turdus merula
Authors: Hatchwell B J , Wood M J , Anwar M , Perrins C M
Published: April 2011

The prevalence and ecology of the haematozoan parasites of a rural population of European blackbirds, Turdus merula, were investigated. Parasites belonging to eight species from four genera (Leucocytozoon, Plasmodium, Haemoproteus, and Trypanosoma) were identified. Prevalence was high: 83% of adults and 80% of juveniles were infected by at least one species of haematozoa, but no parasites were detected in 8-day-old nestlings. There were no sex differences in infection rates and only Plasmodium infection varied with age among adult blackbirds. Haemo proteus infections increased and Plasmodium infections decreased through the sampling period (January to July), but infections with other haematozoa showed no seasonal change. Haemoproteus and Plasmodium were negatively associated with each other, even during the period when infections by both genera were frequent in the study population.
Long-term spatial stability of coyote (Canis latrans) home ranges in southeastern Colorado
Authors: Kitchen Ann M , Gese Eric M , Schauster Edward R
Published: April 2011

Long-term stability of territorial boundaries has not been well documented in canids. To evaluate the prevalence of long-term spatial stability of coyote (Canis latrans) home ranges, we compared the overlap of territorial boundaries and the spatial distribution of telemetry locations of packs in southeastern Colorado. From August 1983 to July 1988 (period 1), 16 coyotes from six packs were radio-tracked. From April 1996 to August 1997 (period 2), 12 coyotes from six packs were captured and tracked in the same area. Mean percentage of overlap of pack ranges was 89.8 ± 8.3% (±SD) for period 1 ranges over period 2 ranges and 55.8 ± 14.4% for period 2 ranges over period 1 ranges. Mean percentage of overlap of the 30% core area of the home ranges was 65.2 ± 13.9% for those of period 1 over those of period 2 and 66.3 ± 28.7% for those of period 2 over those of period 1. Despite substantial overlap of home-range and core-use areas, there were significant differences in the distribution of locations between periods in five of six home ranges. This suggests that, although packs are faithful to one site (i.e., boundaries remain similar over a period of years), their use of the site (i.e., distribution of locations within the range) may change temporally.
Effect of brief exposure to a potential predator on cortisol concentrations in female Columbian ground squirrels (Spermophilus columbianus)
Authors: Hubbs Anne H , Millar John S , Wiebe John P
Published: April 2011

We examined the effect of exposure to a potential predator on cortisol concentrations in captive female Columbian ground squirrels (Spermophilus columbianus) and determined if lactation mitigated this cortisol response. Lactating and nonlactating females were exposed to a dog (Canis familiaris) for 5 min once a week over a 8-week period. Blood was collected 5 min and 2.5 and 4.5 h after exposure to the dog. Females exposed to the dog had higher concentrations of total (but not free) cortisol than unexposed females only in the 5-min blood sample. Over the active season, total- and free-cortisol levels were 37-47% higher in females exposed to the dog than in unexposed females in early to mid-July when young were being weaned. The cortisol response to the dog was suppressed during lactation. Cortisol levels were, on average, 41-59% lower during lactation than during nonlactation 5 min (but not 2.5 or 4.5 h) after exposure to the dog.
Multipulse Chaotic Dynamics for a Laminated Composite Piezoelectric Plate
Authors: Zhang J. H. , Zhang W.
Published: April 2011

We investigate the global bifurcations and multipulse chaotic dynamics of a simply supported laminated composite piezoelectric rectangular thin plate under combined parametric and transverse excitations. We analyze directly the nonautonomous governing equations of motion for the laminated composite piezoelectric rectangular thin plate. The results obtained here indicate that the multipulse chaotic motions can occur in the laminated composite piezoelectric rectangular thin plate. Numerical simulations including the phase portraits and Lyapunov exponents are used to analyze the complex nonlinear dynamic behaviors of the laminated composite piezoelectric rectangular thin plate.
Local Analyticity in the Time and Space Variables and the Smoothing Effect for the Fifth‐Order KdV‐Type Equation
Authors: Tomoeda Kyoko
Published: April 2011

We consider the initial value problem for the reduced fifth‐order KdV‐type equation: , t, x ∈ ℝ, u(0, x) = ϕ(x), x ∈ ℝ. This equation is obtained by removing the nonlinear term from the fifth‐order KdV equation. We show the existence of the local solution which is real analytic in both time and space variables if the initial data ϕ ∈ Hs(ℝ)  (s > 1/8) satisfies the condition , for some constant A0    (0 < A0 < 1). Moreover, the smoothing effect for this equation is obtained. The proof of our main result is based on the contraction principle and the bootstrap argument used in the third‐order KdV equation (K. Kato and Ogawa 2000). The key of the proof is to obtain the estimate of ∂x(∂xu) 2 on the Bourgain space, which is accomplished by improving Kenig et al.′s method used in (Kenig et al. 1996).
Computation of Ice Shedding Trajectories Using Cartesian Grids, Penalization, and Level Sets
Authors: Beaugendre Héloïse , Morency François , Gallizio Federico , Laurens Sophie
Published: April 2011

We propose to model ice shedding trajectories by an innovative paradigm that is based on
cartesian grids, penalization and level sets. The use of cartesian grids bypasses the meshing issue, and
penalization is an efficient alternative to explicitly impose boundary conditions so that the body‐fitted
meshes can be avoided, making multifluid/multiphysics flows easy to set up and simulate. Level sets
describe the geometry in a nonparametric way so that geometrical and topological changes due to
physics and in particular shed ice pieces are straight forward to follow. The model results are verified
against the case of a free falling sphere. The capabilities of the proposed model are demonstrated on
ice trajectories calculations for flow around iced cylinder and airfoil.
Digital Control of a Continuous Stirred Tank Reactor
Authors: Di Ciccio M. P. , Bottini M. , Pepe P.
Published: April 2011

We project a novel digital control law for continuous stirred tank reactors, based on sampled measures of temperatures and reactant concentration, as it happens in practice. The methodology of relative degree preservation under sampling is used. It is proved that a suitably approximated sampled system, obtained by Taylor series expansion and truncation, in closed loop with the projected control law, is asymptotically
stable, provided that a condition on the sampling period is verified. Such condition allows for values of the sampling period larger than necessary in practical implementation with usual technology. Many simulations show the high performance of the proposed digital control law.
Chaos Control and Hybrid Projective Synchronization of a Novel Chaotic System
Authors: Wang Tao , Wang Kejun , Jia Nuo
Published: April 2011

Adaptive feedback controllers based on Lyapunov′s direct method for chaos control
and hybrid projective synchronization (HPS) of a novel 3D chaotic system are proposed.
Especially, the controller can be simplified ulteriorly into a single scalar
one to achieve complete synchronization. The HPS between two nearly identical
chaotic systems with unknown parameters is also studied, and adaptive parameter
update laws are developed. Numerical simulations are demonstrated to verify the
effectiveness of the control strategies.
SOD1 Transcriptional and Posttranscriptional Regulation and Its Potential Implications in ALS
Authors: Milani Pamela , Gagliardi Stella , Cova Emanuela , Cereda Cristina
Published: April 2011

Copper-zinc superoxide dismutase (SOD1) is a detoxifying enzyme localized in the cytosol, nucleus, peroxisomes, and mitochondria. The discovery that mutations inSOD1gene cause a subset of familial amyotrophic lateral sclerosis (FALS) has attracted great attention, and studies to date have been mainly focused on discovering mutations in the coding region and investigation at protein level. Considering that changes in SOD1 mRNA levels have been associated with sporadic ALS (SALS), a molecular understanding of the processes involved in the regulation ofSOD1gene expression could not only unravel novel regulatory pathways that may govern cellular phenotypes and changes in diseases but also might reveal therapeutic targets and treatments. This review seeks to provide an overview ofSOD1gene structure and of the processes through which SOD1 transcription is controlled. Furthermore, we emphasize the importance to focus future researches on investigating posttranscriptional mechanisms and their relevance to ALS.
On the Convergence of Implicit Iterative Processes for Asymptotically Pseudocontractive Mappings in the Intermediate Sense
Authors: Qin Xiaolong , Kim Jong Kyu , Wang Tianze
Published: April 2011

An implicit iterative process is considered. Strong and weak convergence
theorems of common fixed points of a finite family of asymptotically pseudocontractive mappings in the
intermediate sense are established in a real Hilbert space.
Urinary Elimination of Coproporphyrins Is Dependent onABCC2 Polymorphisms and Represents a Potential Biomarker of MRP2 Activity in Humans
Authors: Benz-de Bretagne Isabelle , Respaud Renaud , Vourc′h Patrick , Halimi Jean-Michel , Caille Agnès , Hulot Jean-Sébastien , Andres Christian R. , Le Guellec Chantal
Published: April 2011

MRP2 encoded by ABCC2 gene is involved in the secretion of numerous drugs and endogenous substrates. Patients with Dubin‐Johnson syndrome due to mutation in ABCC2 gene have elevated urinary coproporphyrin ratio (UCP I/(I + III)). Here we investigated whether this ratio could serve as a biomarker of MRP2 function.
Phenotype‐genotype relationships were studied in 74 healthy subjects by measuring individual UCP I/(I + III) ratio obtained on 24‐hour urine and by analyzing five common SNPs in ABCC2 gene. The UCP I/(I + III) ratio varied from 14.7% to 46.0% in our population. Subjects with 3972TT genotype had a higher ratio (P = .04) than those carrying the C allele. This higher UCP I/(I + III) ratio was correlated with a higher level of isomer I excretion.
This study provides a proof of concept that UCP I/(I + III) ratio can be used as a biomarker of MRP2 function in clinical studies as it provides quantitative information about the in vivo activity of MRP2 in a given patient.
Suppressing Chaos of Duffing‐Holmes System Using Random Phase
Authors: Longsuo Li
Published: April 2011

The effect of random phase for Duffing‐Holmes equation is investigated. We
show that as the intensity of random noise properly increases the chaotic dynamical behavior will be suppressed by the criterion of top Lyapunov exponent,
which is computed based on the Khasminskii′s formulation and the extension
of Wedig′s algorithm for linear stochastic systems. Then, the obtained results
are further verified by the Poincaré map analysis, phase plot, and time evolution on dynamical behavior of the system, such as stability, bifurcation, and chaos. Thus excellent agrement between these results is found.