bluuebunny/crossref_metadata_2025 huggingface dataset:
Relationship between deer mouse population parameters and dieldrin contamination in the Rocky Mountain Arsenal National Wildlife Refuge
Authors: Allen Daniel L , Otis David L
Published: April 2011

A small-mammal capture-recapture study was conducted in the Rocky Mountain Arsenal National Wildlife Refuge to quantify the effects of soil contamination with dieldrin on demographic parameters of deer mouse (Peromyscus maniculatus) populations. Increased dieldrin concentrations were significantly associated with larger deer mouse populations, although the size of populations on contaminated sites decreased during the study. The most parsimonious model for estimating survival rates was one in which survival was a decreasing function of dieldrin concentration. A significantly higher proportion of female deer mice in the populations residing on the more highly contaminated sites exhibited signs of reproductive activity. Development of genetic resistance in P. maniculatus to chronic chemical exposure is suggested as a possible mechanism responsible for the species' observed dominance and relatively high densities on contaminated sites. Under the additional stress of unfavorable environmental conditions, however, these populations may suffer disproportionately greater mortality. The design and analytical methods presented offer a rigorous statistical approach to assessing the effects of environmental contamination on small mammals at the population level.
Dynamics of woodland caribou populations at the southern limit of their range in Saskatchewan
Authors: Rettie W James , Messier François
Published: April 2011

Woodland caribou (Rangifer tarandus caribou) in central Saskatchewan are aggregated into several spatially disjunct populations. Historical data indicate that some local populations were eliminated and that the regional metapopulation declined during the 1970s. Proximate causes of decline may have included hunting, severe winter weather, and the end of predator control, though the ultimate causes may relate to road construction and logging activity, which expanded after 1966. There has been no sport hunting since 1987, yet the caribou populations in the region appear to be declining. Based on serum progesterone levels, first conception by females occurred at 16 months and the overall pregnancy rate was 94%, and in addition the minimum parturition rate was 86%, all of which indicate adequate nutrition. The annual survival rate of adults was 84%, which is comparatively low, though similar to results from other studies on woodland caribou. We observed a low rate of calf recruitment (28 calves : 100 cows), which we suspect was due to predation. Wolves (Canis lupus) have long been thought to limit woodland caribou populations while subsisting on other ungulate prey, but we speculate that black bear (Ursus americanus) predation may be an important cause of poor calf survival.
Influence of cliffs on bird community diversity
Authors: Matheson J D , Larson D W
Published: April 2011

Cliffs along the Niagara Escarpment in Ontario, Canada, support a long, narrow presettlement forest that includes three distinct geomorphic and vegetation zones: cliff edge, cliff face, and talus slope. This unique landform provides an opportunity to evaluate differences in bird communities between the escarpment and adjacent forest relative to habitat features. We sampled forest birds 12 times during the summer of 1994 in plots located in plateau forests, on talus slope, at cliff edges, and on cliff faces. Eleven habitat variables considered important to birds were also sampled in the plots. We arranged plots along six randomly spaced transects at a south site and a north site. Both sites had the consistent habitat heterogeneity considered important to birds. Bird species richness and composition responded to this heterogeneity, but differently at each site: plateau deciduous forests always had the lowest richness and the simplest species composition, whereas both cliff edges and talus slopes had a higher diversity of birds. Cliff faces had large numbers of species in the south but smaller numbers in the north. Escarpment zones form a habitat mosaic that supports many species not found in the adjacent forest and is consistent with the effect of habitat edge. The results suggest that cliffs represent a significant additive influence on avian biodiversity, even when the cliff is a very narrow component of the landscape.
Effects of the zebra mussel (Dreissena polymorpha) invasion on the macrobenthos of the freshwater tidal Hudson River
Authors: Strayer David L , Smith Lane C , Hunter Dean C
Published: April 2011

To assess the effect of the zebra mussel (Dreissena polymorpha) invasion on benthic animal communities, we monitored the macrozoobenthos at eight sites in the freshwater tidal Hudson River in 1990-1995. Zebra mussels were absent or scarce in the Hudson River before September 1992, but abundant (mean 17 000/m2) on hard substrata in 1993-1995 and responsible for large declines in phytoplankton biomass. All of our monitoring stations had soft sediments, and so had low local densities of zebra mussels (mean 78/m2). Nevertheless, we observed marked changes in the macrozoobenthos at these stations. Sphaeriid clams declined by 67% between 1990-1992 and 1993-1995, but no other group of macrobenthos showed a simple change in density between 1990-1992 and 1993-1995 across all eight monitoring sites. Instead, most taxa showed a strong interaction between zebra mussel impacts and water depth. At deep-water sites, macrozoobenthic density declined by 33% between 1990-1992 and 1993-1995, while at shallow-water sites, density rose by 25%. We suggest that these changes were probably caused by reduced sedimentation of edible particles at deep-water sites combined with increased biomass of macrophytes and attached algae at shallow-water sites.
Natural temperature regimes for loggerhead and green turtle nests in the eastern Mediterranean
Authors: Kaska Y , Downie R , Tippett R , Furness R W
Published: April 2011

Temperatures of green turtle (Chelonia mydas) and loggerhead turtle (Caretta caretta) nests on the beaches of northern Cyprus and Turkey were examined. Electronic continuous-temperature recorders programmed by computer were placed at the top, middle, and bottom of the nests. The sex of 3-7 hatchlings from each level was determined from gonadal histology. The maximum temperature increase during the incubation period was 9.6oC for both species. The mean temperature during the middle third of the incubation period is a good indicator of the sex ratio of the clutch. The percentage of female embryos increased with temperature, 50% being female at 29°C. The mean temperature over the entire incubation period is not a good indicator of sex ratio but can be used to predict the duration of incubation period. The temperature differences within the clutch were larger in loggerhead than in green turtle nests. Eggs at the top of the nest experienced generally warmer (up to 1.4°C) conditions than eggs at the bottom of the same nest, and this caused variation in sex ratio within nests. Over all nests, the sex ratio (percent female) of hatchlings was 91% at the top, 83% at the middle, and 69% at the bottom. There was considerable interbeach thermal variation. Marked diel cycles of up to 1.5°C were detected in loggerhead turtle nests but not in the deeper nests of green turtles.
Effect of floral symmetry on flower choice and foraging behaviour of bumble bees
Authors: West E L , Laverty T M
Published: April 2011

Bumble bees are known to prefer symmetrical over asymmetrical flowers and bilateral over radial flower types. This study examined the basis of these preferences in three experiments with artificial flowers. The first experiment showed that flower-naive worker bees (Bombus impatiens) displayed no innate preference for symmetrical over asymmetrical or bilateral over radial flowers in choice tests. The second experiment tested whether bees showed a learning or memory bias for symmetrical over asymmetrical rewarding flowers when foraging on arrays of either bilateral or radial flower types. There was no evidence that bees learned or remembered symmetrical rewarding flowers better than asymmetrical rewarding flowers. The percentage of visits to rewarding flowers during test runs for bees foraging on arrays with bilateral flowers was consistently greater than on arrays with radial flowers. A third experiment examined the effect of nectar-guide symmetry on flower-handling and travel times. Bees were tested on homogeneous arrays with bilateral or radial flowers of either symmetrical or asymmetrical shapes and with symmetrical, asymmetrical, or no nectar guides. Guide symmetry had no effect on flower-handling or travel times. However, bees handled symmetrical flowers about 20% faster than asymmetrical flowers and bilateral flowers about 45% faster than radial flowers; travel times of bees on arrays with bilateral flowers were about 2.5 times faster than travel times of bees foraging on arrays of radial flowers.
Tick-removal grooming by elk (Cervus elaphus): testing the principles of the programmed-grooming hypothesis
Authors: Mooring Michael S , Samuel W M
Published: April 2011

The grooming behaviour of elk (Cervus elaphus) was observed in order to test the predictions of the programmed-grooming hypothesis. The highest grooming rates occurred when most winter ticks, Dermacentor albipictus, were blood-feeding. Elk at Elk Island National Park (EINP) and Jasper National Park (JNP) oral-groomed most during October-November, when larval ticks were engorging, with a secondary peak of grooming occurring during February-March-April, when nymphal and adult ticks were engorging. Elk at JNP supported 3 times the density of ticks and groomed 2-4 times more frequently than elk at EINP. Extensive grooming resulted in hair loss on JNP elk, with highest prevalence of hair loss in months with high grooming rates. These results support the prediction of the "tick-challenge principle" that hosts will groom more frequently when the threat of tick infestation is greater. At JNP, calves 1-6 weeks old groomed at 6-10 times the rate of cows, supporting the prediction of the "body-size principle" that smaller animals will groom more than larger animals. These patterns of grooming in elk may reflect an intrinsic grooming clock selected to optimize the tick-removal benefits of grooming in accordance with the constraints imposed by the Canadian winter.
Experimental tests of intraspecific competition in stream riffles between juvenile and adult longnose dace (Rhinichthys cataractae)
Authors: Mullen Dennis M , Burton Thomas M
Published: April 2011

This study was conducted to examine the role of intraspecific competition in size-specific habitat segregation by longnose dace (Rhinichthys cataractae). Previous studies indicate that adults use faster velocity areas and larger substrates than juveniles. An instream maze containing fast- (40-50 cm/s), medium- (25-35 cm/s), and slow-velocity (0-10 cm/s) habitats was used to examine the habitat preferences of both size classes. Cages provided with a single shelter were used to examine the effect of the presence of adults on shelter use by juveniles, and adults were removed from an enclosed riffle to examine the response of juveniles. Both adults and juveniles used the fast- and medium-velocity habitats within the maze and avoided the slow-velocity habitat. Juveniles reduced their use of the shelters in the presence of adults, and expanded their niches to include faster velocity areas of the riffle when adults were removed from the enclosed riffle. However, juveniles did not increase their use of larger substrates in the absence of adults. These results suggest that segregation of juvenile and adult longnose dace according to velocity is due to intraspecific competition for faster velocity areas within the riffle, while segregation according to substrate size may be due simply to an increasing preference for larger substrates as fish grow.
Growth, nutrition, and blow fly parasitism in nestling Pied Flycatchers
Authors: Merino Santiago , Potti Jaime
Published: April 2011

The nutritional status of the host may play a major role in mediating the detrimental effects of parasites. We performed an experiment with the aim of determining whether increased food availability can compensate for the effects of ectoparasites on growth during the late nestling period, final size, and survival until fledging of Pied Flycatcher (Ficedula hypoleuca) nestlings. Nests were provided with supplementary food, treated with insecticide, given both treatments, or given neither treatment (control). Differences in the number of blood-sucking, ectoparasitic blow fly larvae (Protocalliphora azurea) occurred between treated nests. Nestlings in the group given supplementary food and with low numbers of parasites grew faster and had a higher haematocrit value than those in groups that were fumigated and given supplementary food, with nestlings from control nests attaining the lowest values. Nestling measurements did not differ between fumigated and food-supplemented groups. Although the final sizes attained did not differ among nestlings from the different experimental groups, there was a significant difference in the rates of increase in size among groups. Nestlings in nests fumigated and provided with extra food were (nonsignificantly) smaller and leaner than nestlings from the other groups at the beginning of the experiment, but were slightly larger and heavier (again nonsignificantly) at the end of the experiment. Thus, their growth was faster than that of the other groups. The results are discussed, highlighting problems related to the function linking intensity of parasit ism to host fitness and variation in external (climate, food) conditions.
Avifaunal and habitat changes resulting from conversion of native prairie to crested wheat grass: patterns at songbird community and species levels
Authors: Sutter G C , Brigham R M
Published: April 2011

Many North American grassland songbirds are experiencing significant population declines, partly because of land-use practices associated with agricultural activity. The aim of this study was to compare the habitat correlates of songbirds breeding in native mixed-grass prairie with patterns found in introduced vegetation dominated by crested wheat grass (Agropyron pectiniforme). We assessed plant species composition, habitat structure, and bird species diversity over 2 years to document species- and community-level trends in southwestern Saskatchewan, Canada. In addition to having higher plant species richness and diversity, native vegetation consisted of significantly more grass and sedge cover, less bare ground, deeper litter, and higher density within 10 cm of the ground than introduced vegetation. Bird species richness and diversity and the abundance of Baird's Sparrows (Ammodramus bairdii) and Savannah Sparrows (Passerculus sandwichensis) increased significantly along a multivariate gradient from open to more sheltered habitat, regardless of vegetation type. Sprague's Pipits (Anthus spragueii) showed a curvilinear increase along the same gradient, occurring in high numbers where habitats offered an intermediate level of cover. Our findings suggest that species richness and diversity within songbird communities and the abundance of some species may be reduced where conversion to crested wheat grass results in more open habitat.
Habitat use by Harlequin Ducks breeding in Hebron Fiord, Labrador
Authors: Rodway Michael S
Published: April 2011

Understanding of breeding habitat requirements is vital to recovery plans for the endangered eastern North American population of Harlequin Ducks (Histrionicus histrionicus). I compared habitat characteristics and benthic invertebrate fauna between streams in Hebron Fiord, Labrador, used and unused by Harlequin Ducks in 1996. Used streams were narrower, had higher pH and temperature, a larger substrate, steeper shorelines, and greater vegetation cover on islands and shorelines than unused streams. Greater numbers of invertebrates were recovered from kick samples, simuliid larvae and plecopteran nymphs were more frequent, and chironomid larvae and emphemeropteran nymphs were less frequent in used than in unused streams. Results from this study will help focus future survey and conservation efforts.
Interannual variation in birth mass and postnatal growth rate of Juan Fernández fur seals
Authors: Ochoa-Acuña Hugo , Francis John M , Boness Daryl J
Published: April 2011

The objectives of this study were to establish body mass at birth, postnatal growth rate, and the factors that influence these parameters for the Juan Fernández fur seal, Arctocephalus philippii. Females of this species have an unusual attendance pattern in which foraging trips and shore visits last, on average, 12.3 and 5.3 days, respectively. Pup mass was obtained from cohorts born during the reproductive seasons in 1988 through 1992. Birth masses of male and female pups were significantly different, averaging 6.1 and 5.5 kg, respectively (F = 13.2, P < 0.0003, n = 238). Birth masses also differed among cohorts, being lowest in 1992 and highest in 1990. During the first 2 months of life, male and female pups grew at the same rate (79 ± 61.5 g · day-1 (mean ± SD); F[1] = 0.03, P = 0.8562). Interannual differences in growth rate during the first month were significant (F[4] = 8.14, P < 0.0001), as was the interaction between month and year effects (F[2] = 6.81, P = 0.0012). Growth rates for the 1990 cohort were lower than those in all other years except 1992. Birth masses and postnatal growth rates of Juan Fernández fur seal pups are comparable to those of other otariid species.
Population density, survival, and rabies in raccoons in an urban national park
Authors: Riley Seth PD , Hadidian John , Manski David A
Published: April 2011

Density and survival of a raccoon (Procyon lotor) population in Rock Creek Park, an urban national park inWashington, D.C., were estimated using markrecapture and radio-tracking over an 8-year period following the appearance ofthe mid-Atlantic States (Mid-Atlantic) rabies epizootic. Raccoon density ranged from 333.3 to 66.7/km2 , with an overall parkestimate of 125/km2 . This density places the Rock Creek population within the range of other urban and suburban populationsand is many times greater than raccoon densities reported from other habitats. Density was particularly high in one thin spur ofparkland with the smallest ratio of area to urban edge. Raccoon survival rates were high except among juveniles during therabies epizootic. Data on rabies prevalence from Washington, D.C., indicate a cycle with peaks in 1983 during the initialepizootic and again in 1987 and 1991, a pattern similar to that seen in other carnivores and in rabies models. We found evidenceof decreased raccoon density during and after the 1987 rabies resurgence relative to the years following the original epizootic,when rabies prevalence was low. While hunting and trapping represent a major mortality factor for many rural raccoonpopulations, urban and suburban populations and protected populations may frequently be subject to epizootics of diseasessuch as canine distemper and rabies, even years after initial contact with a disease.
Compromises: sound frequencies used in echolocation by aerial-feeding bats
Authors: Fenton M B , Portfors C V , Rautenbach I L , Waterman J M
Published: April 2011

Hunting aerial-feeding bats, species that take airborne prey (usually flying insects), use echolocation to detect, track,and assess targets. The echolocation calls of aerial-feeding bats at sites in Canada (British Columbia and Ontario), Mexico,Brazil, and Zimbabwe were significantly dominated by frequencies between 20 and 60 kHz, although at the more tropicallocations some aerial-feeding bats used echolocation calls with most energy <20 or >60 kHz. The impact of frequency-specificattenuation, perhaps combined with frequency-specific, hearing-based defenses of some insects, suggests that by usingecholocation calls <20 kHz, bats could both extend the effective range of echolocation and make their calls less conspicuous toinsect ears. Bats using calls >60 kHz would be less conspicuous to the insects. We found two patterns of echolocation-callbehaviour. Most adjacent echolocation calls, and all that were dominated by sounds >20 kHz, showed large (80%) overlap inbandwidth. The other pattern involved much less overlap in bandwidth (030%) between adjacent calls and was evident in thecalls of the molossid Tadarida midas, which used echolocation calls dominated by sounds <20 kHz. This behaviour wouldallow the echolocating bat to extend its effective range of perception by separating in frequency the echoes returning fromadjacent calls.
A major sextet of mitochondrial DNA phylogenetic assemblages extant in eastern North American brook trout (Salvelinus fontinalis): distribution and postglacial dispersal patterns
Authors: Danzmann Roy G , Morgan II Raymond P , Jones Matthew W , Bernatchez Louis , Ihssen Peter E
Published: April 2011

Mitochondrial DNA (mtDNA) restriction fragment length polymorphisms (RFLPs) of 2422 brook trout (Salvelinus fontinalis) from 60 units (major drainages, small stream catchments, and isolated lakes) representing 155 populations in eastern North America were examined to test hypotheses regarding postglacial dispersal and recolonization. An analysis of molecular variance (AMOVA) indicated that 38.8% of the variation was partitioned among the units, while approximately 60% was distributed among populations (phiST = 59.3) compared with 40.7% within populations. This distribution of variation suggests a large degree of heterogeneity in population founding events and phylogeographic structuring in this species. Comparisons of mtDNA diversity between fish from putative refugial and recolonization zones for this species indicate that more than one refugial region contributed to northern recolonization. Haplotypic diversities in recolonized regions are greatest in south-central populations (i.e., southern Great Lakes region), while only one haplotype (haplotype 1) predominates in northern, western, and eastern postglacial zones. Large phylogenetic differences were found between northern and southern populations. Populations outside the zone of glaciation were the most genetically heterogeneous and were represented by fish from all six (A-F) of the major evolutionary clades identified. Only fish from the A, B, and C clades were found in glaciated regions, with C lineage fish restricted to south-central glaciation zones. Fish from the C clade are putatively the most ancestral lineage within the species based upon composite shared RFLPs with lake trout (Salvelinus namaycush) and Arctic char (Salvelinus alpinus).
How many flower types can bumble bees work at the same time?
Authors: Gegear R J , Laverty T M
Published: April 2011

Bumble bees often restrict their foraging behaviour to the flowers of two plant species on a single foraging trip ("a major and a minor" sensu Heinrich), perhaps because learning additional flower-handling techniques interferes with their ability to recall previously learned flower-handling skills. This hypothesis was tested with bumble bees (Bombus impatiens) foraging on arrays of artificial flower types. Test bees were first trained on one flower type, then retested on the same flower type after learning one, two, or three different types. The number of flower types selected by bees on a mixed array consisting of several types was also tested. Interference effects increased with the number and complexity of interfering flower types: a 0% increase for one simple flower type; 278% for two simple flower types; 357% for three simple flower types; and 565% for two complex flower types; switching among more than two flower types caused substantial interference. On the mixed array of three flower types, none of the 20 foragers tested randomly visited all three types, 67% primarily visited two types, and 33% primarily visited one type. These findings suggest that the bees limited the number of flower types to two because of the substantial costs incurred when a third flower type was included in their foraging repertoire.
Ecological correlates of mortality of roe deer fawns in a predator-free environment
Authors: Andersen Reidar , Linnell John D
Published: April 2011

The mortality of roe deer (Capreolus capreolus) fawns in summer was studied on Storfosna Island (10 km²), a predator-free island 2 km off the west-central coast of Norway, during a period of rapid population increase. Between 1991 and 1994 the population density increased from about 10 to 40 roe deer/km2. During this period 285 live and 36 stillborn fawns were found and the live fawns were all subsequently radio-collared. All observed mortality occurred within the first 35 days of life. The main causes of death were stillbirth, starvation/hypothermia, drowning, car accidents, and falls. The average annual total mortality for all 4 years was 18%. Although there was a large increase in mortality between 1991 and 1992 (from 10 to 18%), there was little subsequent increase in the last 3 years, resulting in an overall weak density dependence in total mortality. However, the proportion of stillbirths (5% in 1991 to 15% in 1994) showed a clear and significant trend toward an increase with increasing density. Low temperatures in April, which strongly affect the timing of the spring flush of high-quality forage during late gestation, also tended to contribute to higher mortality. Fawns that died were found to have reduced individual growth rates prior to death compared with fawns that survived. Fawns born to relatively light mothers or in triplet litters had higher mortality rates than those born to heavy mothers or in smaller litters. Maternal age and date of birth or sex of fawn had no effect on mortality.
Daily activity and behavioral thermoregulation of the guanaco (Lama guanicoe) in winter
Authors: de Lamo Daniel A , Sanborn Allen F , Carrasco Cynthia D , Scott Donald J
Published: April 2011

We investigated daily activity and the effects of ambient conditions on that activity to determine behavioral mechanisms of thermoregulation in the guanaco (Lama guanicoe). Observations of captive animals (an adult female, an adult male, and a yearling male) show that ambient conditions affect the posture of the animals. These behaviors have the effect of closing "thermal windows" in the axillary and flank regions, thus decreasing heat loss through radiation and convection. When the ambient temperature (Ta) was between 0 and 10°C, the animals used postural adjustments to decrease the area of the thermal windows to 5-7% of total surface area. At Ta > 10°C the animals increased the area (up to 22%) of the thermal windows to regulate heat loss through radiation and convection. When Ta was below 0-1°C the animals tended to bed and huddle together. Bedding and huddling were only initiated by the yearling. Another thermoregulatory behavior the animals exhibited was to bed with their hindquarters into the wind. Bedding and the orientation of the animal in the bedding posture are two behavioral strategies used to decrease convective heat loss. These postures can lead to calculated energy savings of 67%. Posture was determined to be one of the most sensitive parameters for regulating heat loss in the guanaco.
Sex and species differences in cell-mediated immune responses in voles
Authors: Klein Sabra L , Nelson Randy J
Published: April 2011

Males generally display reduced immune responses and greater susceptibility to disease than females, possibly reflecting the suppressive effects of androgens on the immune system. It is presumed that this androgenic effect on immune function is more pronounced among polygynous than monogamous species because concentrations of circulating androgens are generally higher among polygynous than monogamous males. The present study examined sex and species differences in cell-mediated immunity of two Microtus species. Cell-mediated immunity was assessed among individually housed polygynous meadow voles (M. pennsylvanicus) and monogamous prairie voles (M. ochrogaster) by examining the proliferative responses of splenocytes to the T-cell mitogen concanavalin A (Con A) and the B-cell mitogen lipopolysaccharide (LPS). Neither sex nor species differences were observed in response to stimulation with Con A. In contrast, meadow voles exhibited higher proliferative responses to LPS than prairie voles. Sex differences in immune function were only observed among prairie voles; males exhibited higher proliferative responses to LPS than females. Male meadow voles had higher circulating testosterone concentrations than male prairie voles and female prairie voles had higher estradiol concentrations than female meadow voles. Males of both Microtus species weighed more than conspecific females. The immunological differences were not related to differences in either body mass or hormone concentrations. Overall, these data do not support the hypothesis that higher androgen concentrations in polygynous males influence sex or species differences in immune function.
Morphological alteration in two types of gill chloride cells in Japanese eels (Anguilla japonica) during catadromous migration
Authors: Sasai Seiji , Kaneko Toyoji , Hasegawa Sanae , Tsukamoto Katsumi
Published: April 2011

Gill chloride cell morphology and Na+,K+-ATPase activity were examined in cultured Japanese eels (Anguilla japonica) acclimated to fresh water (FW) or seawater (SW), and in yellow and silver eels caught in wild stocks. Gill Na+,K+-ATPase activity was higher in SW-acclimated cultured eels than in FW eels. Chloride cells were detected in both filament and lamellar epithelia by immunocytochemical staining using anti-Na+,K+-ATPase serum. The filament chloride cells were more abundant and larger in SW eels than in FW eels, whereas there was no apparent difference in lamellar chloride cells. In wild-caught eels, gill Na+,K+-ATPase activity increased as they developed from yellow to silver eels. Filament chloride cells in silver eels were more active than those in yellow eels. In contrast, lamellar chloride cells, which were frequently observed in yellow eels, had decreased in number or disappeared in silver eels. These findings suggest that chloride cells in the filament are responsible for excretion of excess salt in hyperosmotic environments, and that lamellar chloride cells may play a significant role in hypoosmotic environments, presumably acting as sites of ion uptake. The excellent euryhalinity of the Japanese eel may be due, at least in part, to the presence of functionally different types of chloride cells. The activation of filament chloride cells in silver eels in FW, together with the increase in Na+,K+-ATPase activity, could be interpreted as a preadaptive response to forthcoming entry into SW.
Sex differences in parental care in the common swift (Apus apus): effect of brood size and nestling age
Authors: Carere Claudio , Alleva Enrico
Published: April 2011

We analysed sex differences in parental behaviour in a Mediterranean population of common swifts (Apus apus). Females attended the nest and fed the chicks at a higher rate than males and were more in contact with the nestlings during the first days after hatching, while no sex differences were found in other parameters measured. For larger broods no quantitative sex differences were observed in meal-delivery and brooding time, while for small broods the rate of feeding by males was lower than the rate of feeding by females, and males attended the nest less than females. No sex differences were observed at the early nestling stage, but males attended the nest less than females later in the nestling stage. No extra-pair breeding activity was observed. These results suggest that males reduce parental care when the energy requirements of the chicks decrease, while females do not.
Cumulative impacts of an evolving oil-field complex on the distribution of calving caribou
Authors: Nellemann C , Cameron R D
Published: April 2011

We investigated changes in distribution and terrain use of calving barren-ground caribou (Rangifer tarandus granti) with increasing density of roads in the Kuparuk Development Area, an oil-field region near Prudhoe Bay, Alaska. In June of 1987-1992, caribou density, as determined by aerial surveys, was inversely related to road density, declining by 63% at >0.0-0.3 km road/km2 and by 86% at >0.6-0.9 km road/km2. The latter road density virtually excluded cow-calf pairs. Effects of avoidance were most apparent in preferred rugged terrain, comprising important habitats for foraging during the calving period. Our results show that (i) females and calves are far more sensitive to surface development than adult males and yearlings, (ii) the greatest incremental impacts are attributable to initial construction of roads and related facilities, and (iii) the extent of avoidance greatly exceeds the physical "footprint" of an oil-field complex. A disproportionate reduction in use of foraging habitats within the Kuparuk Development Area, combined with decreasing tolerance of the expanding industrial complex, may explain the recent displacement of some calving activity to areas farther inland, and, in part, lower fecundity. Possible consequences include heightened competition for forage, increased risk of predation, and lower productivity of the herd.
Sexual differences in the pattern of spatial variation in the brachypterous grasshopper Podisma sapporensis (Orthoptera: Podisminae)
Authors: Tatsuta Haruki , Akimoto S
Published: April 2011

We examined sexual dimorphism and its geographical pattern in 10 morphological characters, including the genitalia, in the brachypterous grasshopper Podisma sapporensis. Conspicuous sexual dimorphism was observed in all characters. In nine characters, variance in females was significantly greater than in males. Sexual differences among populations varied more in the genitalia than in other characters. Spatial autocorrelation analysis demonstrated that there was no geographical trend in the female genitalia, whereas significant autocorrelation existed in the male genitalia. These results suggest that cryptic female choice is responsible for the autocorrelation pattern of the male genitalia, while random genetic drift or a larger effect of environment has created the geographical pattern of the female genitalia.
Covariation of parasite intensities in willow ptarmigan, Lagopus lagopus L.
Authors: Holmstad Per R , Skorping Arne
Published: April 2011

The distribution of parasites in individual willow ptarmigan (Lagopus lagopus) hosts and associations between parasite numbers were used to investigate whether host susceptibility, in addition to factors associated with exposure, may have influenced the patterns of infection. Eight species of parasites were found, Trichostrongylus tenuis, Capillaria caudinflata, Splendidofilaria papillocerca, Hymenolepis microps, Paroniella urogalli, Leucocytozoon lovati, Eimeria sp., and Trypanosoma sp., in addition to microfilariae. Frequency distributions of all but one of these parasite species were overdispersed. Host age was more closely related to parasite abundance than was host gender. Intensities of different parasites in individual hosts were found to be more similar than expected by chance. Parasite intensities therefore tended to covary in individual hosts, and this covariation became more pronounced when only microparasites and the most abundant macroparasites were analysed. Pairwise correlations between intensities gave significantly more positive than negative values. Common transmission routes cannot account for this pattern, and we conclude that differences in host susceptibility must have been an important factor.
Population differentiation in the franciscana (Pontoporia blainvillei) from two geographic locations in Brazil as determined from mitochondrial DNA control region sequences
Authors: Secchi Eduardo R , Wang John Y , Murray Brent W , Rocha-Campos Claudia C , White Bradley N
Published: April 2011

The franciscana, Pontoporia blainvillei, is a dolphin that experiences extensive incidental mortality in fisheries throughout its restricted distribution and is perhaps the most exploited species along the Atlantic coast of South America. However, the basic information required for effective conservation of this species is lacking. To understand the population structure of this platanistoid dolphin, we sequenced 418 base pairs (bp) of the control region and 68 bp of the adjacent pro-tRNA gene of the mtDNA from 20 franciscana that were captured incidentally by gill-net fisheries of Rio Grande do Sul and Rio de Janeiro, Brazil. Of 11 haplotypes found, 5 were exclusive to franciscana from Rio Grande do Sul and 6 were found only in franciscana from Rio de Janeiro and no haplotypes were shared between locations. Reconstruction of the phylogenetic relationships among the haplotypes through a maximum-likelihood analysis of sequences revealed two distinct lineages that were consistent with the geographic sampling locations. Analysis of molecular variance also showed the population structure (phiST = 0.403, p < 0.0001). Furthermore, the estimate of nucleotide diversity for the northern population (0.38 ± 0.13%) was significantly lower than for the southern population (1.01 ± 0.30%). The genetic evidence indicated that at least two populations of franciscana exist.
Ontogeny of black-footed ferret predatory behavior towards prairie dogs
Authors: Vargas Astrid , Anderson Stanley H
Published: April 2011

To study the effects of environmental upbringing and predation experience on black-footed ferret (Mustela nigripes) predatory skills towards prairie dogs, we compared killing efficiency and behaviors of 32 black-footed ferret kits (from 24 different litters). Four treatment groups were established: group 1 (n = 8), kits raised in indoor cages and never exposed to live prey; group 2 (n = 8), kits raised in indoor cages and fed live hamsters twice a week beginning at 8 weeks of age; group 3 (n = 8), kits raised in indoor cages, fed live hamsters, and exposed to live prairie dogs in family trials once per week; and group 4, kits raised in outdoor enclosures with ad libitum access to live prairie dogs in natural burrows. Juvenile black-footed ferrets raised with exposure to live hamsters were more successful at killing prairie dogs than kits devoid of any predation experience. Previous experience with prairie dogs (in both indoor cages and outdoor pens) significantly increased predation efficiency. Witnessing a black-footed ferret mother performing a kill enhanced the kit's predatory skills. We conclude that the placement of the kill bite appears to be innate for black-footed ferrets, but the likelihood of killing and the efficiency at handling prey are substantially enhanced by experience.
Embryo development and reproductive cycle in the snow crab, Chionoecetes opilio (Crustacea: Majidae), in the southern Gulf of St. Lawrence, Canada
Authors: Moriyasu Mikio , Lanteigne Carole
Published: April 2011

Embryonic stages and egg-incubation durations were compared between female snow crabs, Chionoecetes opilio, in captivity and from the wild. In the southern Gulf of St. Lawrence the incubation time is 24-27 months. There are two prolonged periods of embryo development: (1) stages 3 and 4 (cleavage and blastula, gastrula) last for at least 6 months between May and January following egg extrusion, and (2) stages 11 and 12 (eye-pigment formation, chromatophore formation) last for 3-4 months between October and January of the following year. Water temperature plays an important role in determining the egg-development rate. Embryo development takes 12-13.5 months (365-410 days) when females are kept at a higher temperature (1.8-3.8°C) than that of the normal habitat (-1 to +1°C). Ovigerous females usually inhabit depths of 40-100 m, which is the cold intermediate water in the southern Gulf of St. Lawrence (year-round temperature and salinity -1 to +1°C and 32-33, respectively). However, ovigerous females are also observed at depths of 100-300 m in the Laurentian Channel, where the year-round water temperature is 3-5°C. For ovigerous females that do not migrate to the deeper, warmer waters, the duration of embryo development is 2 years, whereas females that inhabit deeper waters develop their embryos over a 1-year cycle. The reproductive potential and abundance of females with 1- and 2-year embryo-development cycles in the southern Gulf of St. Lawrence are unknown.
Reproductive performance of female Steller sea lions: an energetics-based reproductive strategy?
Authors: Pitcher Kenneth W , Calkins Donald G , Pendleton Grey W
Published: April 2011

We examined the reproductive performance of female Steller sea lions (Eumetopias jubatus) in order to evaluate the hypothesis that low pup production was associated with nutritional stress and to assess whether reduced birth rates could have been a factor in a recent large-scale decline in numbers. Nearly all (97%) sexually mature females were pregnant during early gestation. However, by late gestation, pregnancy rates had declined to 67 and 55% in the 1970s and 1980s, respectively, owing to reproductive failures. We found that body condition, as depicted by mass index and blubber index, had a positive effect on the probability that a female would be pregnant during late gestation. Age, age2, and lactation were also associated with pregnancy status during late gestation. These findings support the hypotheses that reproductive failures were associated with lowered nutritional status and that the resulting low birth rates were a proximate factor in the decline. We speculate that abortion is a part of the reproductive strategy of the female Steller sea lion that enhances overall reproductive performance during times of suboptimal nutrition. A major shift in oceanic regime occurred in the Gulf of Alaska during the late 1970s that resulted in a reduction of about 50% in the overall biomass of fishes and a shift in species composition. Prey resources may not have been adequate to successfully support the Steller sea lions' "energetically expensive" reproductive/foraging strategy during the period of our study.
Health and reproduction: the sex-specific clinical profile of great tits (Parus major) in relation to breeding
Authors: Hõrak P , Jenni-Eiermann S , Ots I , Tegelmann L
Published: April 2011

To describe the changes in clinical profile of individuals that occur during different stages of the reproductive cycle, 17 condition indices including leukocyte counts, plasma protein and metabolite concentrations, hematocrit, and hemoparasite prevalence were examined in prelaying and brood-rearing great tits (Parus major). The metabolic profile pointed to increased fat metabolism during the prebreeding period. Protein metabolism did not indicate nutritional limitation. Prelaying birds had elevated gamma-globulin levels, which may indicate either greater investment in humoral immune defence or, alternatively, greater exposure to immune challenge than for breeders. The sexes did not differ with respect to prevalence of hemoparasites, but females had generally lower albumin/globulin ratios than males, which might indicate a greater predisposition to infectious diseases. Breeding females had higher hematocrit values and heterophile/lymphocyte ratios than males, suggesting that brood rearing imposes a greater work load and exerts greater stress on females. In contrast to the breeding period, males seemed to be more stressed than females prior to egg laying, as indicated by their lower lymphocyte counts and higher heterophile/lymphocyte ratios.
Parvalbumin content in striated muscles of the common shrew (Sorex araneus)
Authors: Savolainen J , Vornanen M
Published: April 2011

The parvalbumin content of mammalian muscles correlates positively with isometric relaxation rate and fiber type IIB frequency of the muscles but negatively with animal size. Since shrews are small-bodied animals with a relatively low number of type IIB fibers, it is of some interest to know how the parvalbumin content of shrew muscle correlates with the above factors. Parvalbumin content in heart, diaphragm, and gastrocnemius muscle of the common shrew, mouse, and rat was determined electrophoretically. Parvalbumin was not found in heart muscle of any species. Shrew diaphragm (0.29 ± 0.04 g/kg) had significantly less parvalbumin than mouse (0.63 ± 0.11 g/kg) or rat (0.54 ± 0.09 g/kg) diaphragm. Similarly, the parvalbumin content of shrew gastrocnemius muscle (0.28 ± 0.04 g/kg) was significantly lower than in that of mouse (2.88 ± 0.38 g/kg) or rat (0.96 ± 0.25 g/kg) gastrocnemius muscle. The isometric twitch of the gastrocnemius muscle was somewhat faster than the twitch of the diaphragm in all three species. The isometric contractions of shrew and mouse skeletal muscles were generally very similar in duration, with the exception of the relaxation time of the gastrocnemius muscle, which was shorter in the mouse. Diaphragm and gastrocnemius muscle of the rat were clearly slower than the respective muscles in the mouse or shrew with regard to both the contraction and relaxation phases. The half-relaxation time of isometric contractions correlated relatively weakly with parvalbumin content of the muscles (r = 0.40) but more strongly with their fiber IIB content (r = 0.81). The unexpectedly low parvalbumin content and relatively slow rate of contraction in shrew skeletal muscles are attributed to the exceptional fiber type composition, i.e., a high proportion of type IID fibers.
Sleep-vigilance trade-off in Green-winged Teals (Anas crecca crecca)
Authors: Gauthier-Clerc Michel , Tamisier Alain , Cezilly Frank
Published: April 2011

We observed the effect of several variables on the sleep-vigilance trade-off in Green-winged Teals (Anas crecca crecca) during winter in the Camargue, southern France. We investigated the relationship between flock size and peeking rate, using field observations and controlling for the effects of other variables with which vigilance previously has been reported to be correlated: sex, date, time of day, distance from shore, and predator presence. Vigilance while sleeping decreased with increasing flock size for females but not for males. The peeking rate was reduced at the end of the winter, when Green-winged Teals were facing important energy requirements. Exposure to a predator resulted in maintenance of a high peeking rate. We discuss these results in relation to predator detection, mate competition, and wintering strategy.
Activity rhythm in High Arctic Svalbard ptarmigan (Lagopus mutus hyperboreus)
Authors: Reierth Eirik , Stokkan Karl-Arne
Published: April 2011

Feeding activity was recorded in captive Svalbard ptarmigan (Lagopus mutus hyperboreus) under natural photoperiodic conditions at 70°N and 79°N. At 79°N, activity was intermittent and non-circadian in summer, when the sun was permanently above the horizon, and in midwinter, when the sun was permanently lower than 6° below the horizon. The intermittent feeding pattern was evident in summer at 70°N, whereas feeding activity in winter appeared to be entrained. In spring and autumn all birds were diurnal, with morning and evening bouts of feeding activity. The phase relationship between the onset or end of activity and the photoperiod showed marked changes, especially at 79°N, but in general, activity onset was more precise relative to twilight than activity end. At 79°N there was a sigmoidal relationship between activity time and photoperiod and activity time was longer in autumn than in spring at equal photoperiods. Based on our results, the activity pattern of Svalbard ptarmigan may be described in terms of a two-oscillator model, although a one-oscillator model cannot be excluded. The possibility is discussed that rhythmic feeding or food availability may act as a zeitgeber in addition to the light-dark cycle.