bluuebunny/crossref_metadata_2025 huggingface dataset:
Functional classification of harbor seal (Phoca vitulina) dives using depth profiles, swimming velocity, and an index of foraging success
Authors: Lesage Véronique , Hammill Mike O , Kovacs Kit M
Published: April 2011

Time-depth-speed recorders and stomach-temperature sensors were deployed on 11 harbor seals (Phoca vitulina) in the St. Lawrence estuary to examine their diving and foraging behavior. Fifty-four percent of dives were to depths of <4 m. Dives that were [Formula: see text] 4 m deep were classified into five distinct types, using a combination of principal components analysis and hierarchical and nonhierarchical clustering analyses. Feeding, indicated by a sharp decline in stomach temperature, occurred during dives of all five types, four of which were U-shaped, while one was V-shaped. Seals swam at speeds near the minimum cost of transport (MCT) during descents and ascents. V-shaped dives had mean depths of 5.8 m, lasted an average of 40 s, and often preceded or followed periods of shallow-water (<4 m) activity. Seals invariably dove to the bottom when performing U-shaped dives. These dives were to an average depth of 20 m during daylight and occurred in shallower waters (~8 m) at twilight and during the night. Once on the bottom, seals (i) swam at MCT speeds with occasional bursts of speed, (ii) swam at speeds near MCT but not exceeding it, or (iii) remained stationary or swam slowly at about 0.15 m/s, occasionally swimming faster. It is unlikely that all dives to depths [Formula: see text] 4 m are dedicated to foraging. However, the temporal segregation of dive types suggests that all types are used during foraging, although they may represent different strategies.
Thermoregulation and repeatability of oxygen-consumption measurements in winter- acclimatized North American porcupines (Erethizon dorsatum)
Authors: Fournier François , Thomas Donald W
Published: April 2011

We measured the thermoregulatory responses of 13 North American porcupines (Erethizon dorsatum) to low ambient temperatures during respirometry trials in both air and a helium-oxygen gas mixture (helox). The objective was to quantify the energy metabolism of porcupines under varying ambient temperatures. The basal metabolic rate of our winter-acclimatized porcupines was higher than expected for animals of their body size, whereas thermal conductance was lower than allometric predictions. The increase in metabolic rate that we observed at -20°C was ca. 2 X BMR, although this was not the animals' maximum thermogenic capacity. The mean increase in thermal conductance for individuals placed in a helox atmosphere over that measured in an oxygen atmosphere was 1.91 and this represented a metabolic rate of ca. 3 X BMR at -20°C. We also determined that the repeatability of oxygen-consumption measurements below thermoneutrality were highly repeatable over medium-length time intervals (mean = 11 days) for both absolute and residual values.
Premature loss of winter hair in free-ranging moose (Alces alces) infested with winter ticks (Dermacentor albipictus) is correlated with grooming rate
Authors: Mooring Michael S , Samuel W M
Published: April 2011

Premature loss of winter hair coat can be a serious problem for moose (Alces alces), possibly leading to escalated heat loss and depleted reserves. Studies of captive moose have indicated that premature winter hair loss is associated with infestation by winter ticks (Dermacentor albipictus), and the extent of hair loss is associated with grooming efforts directed at removing the ticks. In this study we observed the grooming behaviour and hair-loss patterns of wild moose throughout the winter to test the prediction that the extent of hair loss would be positively correlated with the rate of grooming actions (oral grooming, scratching, and rubbing). Moose were observed throughout the winter of 1995-1996 at Elk Island National Park, Alberta. Both the proportion of hair loss and the rate of grooming increased from October through April, with hair-loss and grooming rates highest during the period of adult tick engorgement in March and April. Correlation analysis showed that moose which groomed more experienced greater hair loss. Increased grooming effort was negatively associated with feeding activity, possibly because moose sacrificed feeding time in order to remove engorging ticks; however, metabolic or anorectic effects cannot be ruled out. Despite the potential cost of hair loss from increased grooming, total fitness costs may be greater for moose that fail to groom adequately and subsequently suffer blood loss from feeding nymphal and adult winter ticks.
Prevalence and intensity of hematozoan infections in a population of American kestrels
Authors: Dawson Russell D , Bortolotti Gary R
Published: April 2011

Interest in hematozoan parasites has been considerable in recent years, mostly as a result of Hamilton and Zuk's idea that parasites influence the expression of sexually selected traits. However, little is known about the basic patterns of parasitism and the dynamics of host-parasite relationships. We describe the patterns of blood parasitism in American kestrels (Falco sparverius) sampled throughout the breeding seasons of 1994 and 1995, and investigate the influence of several variables on parasite load. Parasite prevalences in kestrels were high, ranging from 75 to 94% depending on the sex of the birds and stage of the breeding season. Prevalence increased with date, indicating either active parasite transmission or relapses of chronic infections. Parasite intensity also increased with date, but these effects were sex- and year-specific. We detected no sex differences in either prevalence or intensity, but prevalences were higher in young (second calendar year) birds than in older birds. Because this effect was evident early in the breeding season, we suggest that it was due to differential recrudescence of chronic infections between age-classes. Food supply had no effect on parasite load. Among birds that were sampled twice in the same year, parasite status remained relatively constant, although some birds acquired infections while others lost them. Change in intensity between samples was dependent on year; nonetheless, intensities remained relatively stable throughout the breeding season. Kestrels sampled in both years had consistent parasite loads. Parasites were detected in only 3% of kestrel nestlings.
Temporal variation in shedding of coccidial oocysts: implications for sexual-selection studies
Authors: Brawner III William R , Hill Geoffrey E
Published: April 2011

Studies of the effects of parasites on the sexual ornamentation and behavior of animals are becoming increasingly common. A potential difficulty in many studies of this type is the accurate assessment of parasite prevalence within a population and of the parasite burden of individual hosts. We present data that illustrate how a simple factor such as the time of day at which samples are collected can drastically alter the results of parasite assessments. House finches (Carpodacus mexicanus) infected with coccidians of the genus Isospora shed oocysts in their feces predominantly during the late afternoon. The importance of recognizing such circumstances (e.g., diurnal periodicity) is discussed in the light of possible negative effects on studies of host-parasite relationships.
Environmentally induced variation in body size and condition in hatchling snapping turtles (Chelydra serpentina)
Authors: Packard Gary C , Miller Kirk , Packard Mary J , Birchard Geoffrey F
Published: April 2011

We performed an experiment at a field site in north-central Nebraska, U.S.A., to assess the importance of the nest environment as a determinant of body size and condition in hatchling snapping turtles (Chelydra serpentina). The contents of newly constructed nests were manipulated by reciprocal transplant so that each of several nests received a complement of eggs from each of several females. The eggs were recovered from nests after 8 weeks and allowed to complete incubation under standard conditions in the laboratory. Live mass, dry mass and water content of carcasses, and dry mass of unused yolk varied significantly among hatchlings that incubated in different nests. This variation apparently resulted from variation in water exchange by eggs, because embryos in eggs that absorbed water during 8 weeks in the field consumed more of their yolk, grew to a larger size, and were better hydrated at hatching than embryos in eggs that lost water to the nest environment. Phenotypic variation of the magnitude observed in this investigation may affect survival of hatchlings, and therefore needs to be considered explicitly in theories for the evolution of life histories in these long-lived animals.
Sperm-cell ultrastructure of North American sturgeons. II. The shortnose sturgeon (Acipenser brevirostrum, Lesueur, 1818)
Authors: DiLauro Martin N , Kaboord Wayne S , Walsh Rosemary A
Published: April 2011

The fine structure of the sperm cell of the shortnose sturgeon (Acipenser brevirostrum) was examined using transmission electron microscopy and selected metrics. The cell possesses a distinct acrosome, a defined head region, a midpiece, and a single flagellum. The mean length of the sperm cell body (acrosome + nucleus + midpiece) is approximately 9.71 µm, and the length of the flagellum is about 37 µm, resulting in a total cell length of about 46 µm. The sperm cell of the shortnose sturgeon is much longer and slightly wider than that of the Atlantic sturgeon. The nuclei of shortnose, white, and stellate sturgeon sperm cells are elongate trapezoids with the anterior (acrosome) end narrowest, the opposite of that of the Atlantic sturgeon. Although slightly smaller in total length and width than the sperm cells of the stellate and white sturgeons, that of the shortnose sturgeon is most similar to them in overall ultrastructure, as all three cells have three endonuclear canals. A structural connection of unknown function between the nuclear fossa and the proximal centriole, which is similar to the fibrous body in other species, is present in the shortnose sturgeon sperm cell. Our results suggest a more recent evolutionary link between the shortnose, white, and stellate sturgeons than between any of these and the Atlantic sturgeon. This is the first description of sperm cell ultrastructure in the shortnose sturgeon, an endangered species.
Mass dynamics of the spleen and other organs in geese: measures of immune relationships to helminths?
Authors: Shutler Dave , Alisauskas Ray T , McLaughlin J Dan
Published: April 2011

The spleen is an important organ of avian immune systems. We examined whether helminth loads were related to spleen mass in the lesser snow goose, Chen caerulescens caerulescens. On 27 collecting occasions, 744 geese were obtained at 13 different locations in a south-north gradient in midcontinental North America. The masses of the spleen, caecum, small intestine, large intestine, pancreas, heart, and crop of all geese were determined, and intestinal and caecal helminths were counted. Seventy-eight percent of geese harbored at least one helminth species. For analyses, helminths were grouped as cestodes (26% prevalence), trematodes (19% prevalence), and nematodes (70% prevalence). After sample location and time, host age, host sex, and host body size were controlled for in a multivariate analysis of covariance, nematodes were the only helminth group associated with variation in organ masses. Greater nematode loads were weakly associated with lower spleen, higher caecum, lower large intestine, and lower heart masses. When uninfected individuals were excluded from the analysis, greater nematode loads were no longer associated with variation in spleen size but were associated with higher crop mass, and greater cestode loads were associated with higher heart mass. In neither of these analyses were any other cestode-organ or trematode-organ associations significant. Geese carrying two or more helminth groups had lower spleen masses than did geese infected with no or one helminth group. When we interchanged response and explanatory variables from the preceding analyses and retained the same covariates, the same organ mass - helminth associations tended to remain significant. Nonetheless, the small variation in helminth loads explained by variation in spleen mass (or vice versa) provided only weak support for the hypothesis that intraspecifically, wild individuals with lower investment in immunity are more susceptible to nematode infections.
Length-mass relationship, histopathology, and parasitism in winter flounder (Pleuronectes americanus) living near a PCB-contaminated naval facility in Newfoundland
Authors: Khan R A
Published: April 2011

A study was conducted to ascertain the health of winter flounder (Pleuronectes americanus) sampled near a naval facility contaminated with polychlorinated biphenyls (PCBs), using length-mass relationship, hematological values, histopathology, and parasitism as bioindicators of stress. Samples were collected by SCUBA divers about 2 km (Broad Cove) and 5 km (Fox Harbour) down-current from the dockyard and a reference site (Fox Island) 5 km offshore in Placentia Bay, Newfoundland. Length, mass, and condition factor were significantly greater in both sexes sampled at the reference site than at the two contaminated sites, whereas macroscopic anomalies, including fin necrosis, infestation with ectoparasitic metacercariae of the digenean Cryptocotyle lingua, and histopathological lesions in the liver, kidney, spleen, and gills, were more frequent at the latter locations. A greater variety of prey were consumed by fish taken at Fox Island than at Fox Harbour, while food was absent in several samples from Broad Cove. Three endoparasites, Ceratomyxa acadiensis, Echinorhynchus gadi, and Steringophorus furciger, were less prevalent and abundant in flounder sampled at Broad Cove than at the other two sites. These results suggest a connection between PCB contamination and impaired fish health. In addition, anomalies were more prevalent in samples collected nearest to the contaminated site than in those collected farther away.
Fine structure of antennal sensilla of the female sphinx moth, Manduca sexta (Lepidoptera: Sphingidae). II. Auriculate, coeloconic, and styliform complex sensilla
Authors: Shields VDC , Hildebrand J G
Published: April 2011

The antennal flagellum of the female sphinx moth, Manduca sexta, bears eight types of sensilla: two trichoid, two basiconic, one auriculate, two coeloconic, and one styliform complex. We previously described the fine structure of the trichoid and basiconic sensilla (Shields and Hildebrand 1999). In this paper, we describe one type of auriculate, two types of coeloconic, and one type of styliform complex sensilla. The auriculate (ear- or spoon-shaped) sensillum is a small peg that averages 4 µm in length, is innervated by two bipolar sensory cells, and has structural features characteristic of an insect olfactory sensillum. Each of the two types of coeloconic sensilla is a small peg that averages 2 µm in length and is recessed in a cuticular pit. One type of coeloconic sensillum is innervated by five bipolar sensory cells and has structural features characteristic of an insect olfactory sensillum or olfactory-thermosensillum, while the other is innervated by three bipolar sensory cells and has structural features characteristic of an insect thermo-hygrosensillum. The styliform complex sensillum is a large peg that averages 38-40 µm in length and is formed by several contiguous sensilla, the number of which depends on the location of the peg on the flagellum. Each unit of the styliform complex sensillum is innervated by three bipolar sensory cells and has structural features characteristic of a thermo-hygrosensillum. We also ascertained the number and distribution of each of the eight types of sensilla on a single flagellomere (annulus) about midway along the flagellum of a female antenna. A total of 2216 sensilla were found on the dorsal, ventral, and leading surfaces of that annulus.
The effects of moonlight on nocturnal activity in bushy-tailed wood rats (Neotoma cinerea)
Authors: Topping Michael G , Millar John S , Goddard James A
Published: April 2011

The nocturnal activity of bushy-tailed wood rats (Neotoma cinerea) was monitored for two breeding seasons (1993 and 1994) in the Canadian Rockies. Radiotelemetry was used under three levels of moonlight to assess two measures of nocturnal activity: (i) the proportion of animals crossing rocky outcrops and entering the surrounding forest to forage, search for mates, or both, and (ii) the distance moved from the den site while in the forest. Males and females exhibited significant differences among moonlight levels, with greater activity on nights of intermediate-level moonlight and less activity on nights with bright or dark moonlight. There was no difference in the proportions of males and females active at any moonlight level. The distances moved from the den did not differ among moonlight levels for either males or females. Having traversed the rocks and entered the forest, individuals moved similar distances regardless of light level. These results suggest that wood rats respond to moonlight only when making the decision to cross rocks and enter the forest. This behaviour presumably serves to counteract the increased risk of predation on bright nights.
Breeding patterns of Common Loons on lakes with three different fish assemblages in north-central Alberta
Authors: Gingras B A , Paszkowski C A
Published: April 2011

Studies of the Common Loon, Gavia immer, in eastern Canada and the United States suggest that the species' dependence on fish for food limits its breeding habitat to large deep lakes with stocks of fish sufficient to support adults and chicks. In central Alberta, breeding Common Loons are widespread, occurring on nutrient-rich lakes that vary in morphometry and prey base. From 1993 to 1997, small shallow lakes that were fishless (invertebrates were available as principal prey) or contained small-bodied fishes ("minnow lakes"), as well as larger deeper lakes containing large-bodied fishes ("pike lakes"), were surveyed to determine if the occurrence and breeding patterns of Common Loons were influenced by prey assemblage and habitat type. Territorial pairs occurred on all three lake types, but nesting loons and fledglings were more likely to be present on pike lakes than on fishless or minnow lakes. Fishless lakes offered good nesting sites but chicks rarely fledged. Minnow lakes provided good chick-rearing conditions but loons did not often nest on these lakes.
Individually distinctive pup vocalizations fail to prevent allo-suckling in grey seals
Authors: McCulloch Susanne , Pomeroy Patrick P , Slater Peter JB
Published: April 2011

In crowded aggregations that occur in breeding colonies, female pinnipeds commonly become separated from their pups and may use spatial, olfactory, or auditory cues to locate them. A system of mutual recognition based on vocalizations is known for otariids. Female phocids are known to use location and olfaction to help identify pups, but evidence for vocal recognition is weak. During the 1997 breeding season on the Isle of May, Scotland, vocalizations were recorded from grey seal, Halichoerus grypus, pups; playback experiments were carried out; and nursing of nonfilial pups was observed. Pup vocalizations were found to be both stereotyped and individually distinctive, features normally associated with a system of individual recognition. However, playback experiments revealed that mothers did not respond more to vocalizations of their own pups than to those of nonfilial pups. Furthermore, seventeen cases of allo-suckling were observed during 68 h of observation on the colony. High densities of animals and frequent separations present challenges to identification of pups by their mothers.
Spatial and temporal variability in the diet of juvenile Pacific herring (Clupea pallasi) in Prince William Sound, Alaska
Authors: Foy Robert J , Norcross Brenda L
Published: April 2011

The diet of juvenile Pacific herring, Clupea pallasi, from four bays in Prince William Sound, Alaska, varied spatially and seasonally. In Zaikof Bay, which was sampled in each season, stomach fullness of this herring was highest in May and declined significantly through the winter. Diversity of prey taxa in the diet was highest in June, after the spring phytoplankton bloom. In October, Oikopleura species were dominant in the fish diets of all bays. In March, fish eggs, Cirripedia nauplii, small Calanoida, and large Calanoida were the dominant prey in Eaglek, Simpson, Whale, and Zaikof bays, respectively. Energy density of stomach contents was highest in May, highlighting the importance of high lipid copepod taxa in Zaikof Bay. Estimated assimilation rates suggest that the diets of smaller age-0 herring provide close to maintenance levels of energy prior to winter. Therefore, variability in diet composition and diet energy density could account for relative differences in nutritional conditions of age-0 herring in Prince William Sound.
Sources of bias in the use of shell fragments to estimate the size of zebra and quagga mussels (Dreissena polymorpha and Dreissena bugensis)
Authors: Mitchell Jeremy S , Bailey Robert C , Knapton Richard W
Published: April 2011

Several researchers have examined size-selective predation on dreissenid mussels by first measuring septa from crushed mussel shells found in predators' gastrointestinal tracts and then using a regression of septum length on shell length to infer the size of consumed mussels. We examine three assumptions made when using this approach: (1) that the shell length : septum length relationship is site-independent within the study area, (2) where both zebra mussels (Dreissena polymorpha) and quagga mussels (Dreissena bugensis) are present, that the shell length : septum length relationship is the same for both mussel species, and (3) that the predator foraged exclusively at the site of collection. We collected mussels at 6 sites along an 8-km stretch of Lake Erie shoreline and found that the shell length : septum length relationship varied significantly both among sites and between zebra mussels and quagga mussels. We then compared the regression for quagga mussels at one of these sites with that for intact valves of mussels taken from scaup (Aythya marila, Aythya affinis) collected at the site. Although ice cover at the time of collection restricted scaup to the site while foraging within the study area, regressions were again significantly different, i.e., scaup had been foraging elsewhere. Our results indicate that for at least some study sites, the use of septa to estimate dreissenid mussel size is not appropriate. However, when intact valves are found in a predator, variation in shell morphology can help to confirm or exclude possible foraging locales.
Behavior of adult chinook salmon (Oncorhynchus tshawytscha) in British Columbia coastal waters determined from ultrasonic telemetry
Authors: Candy John R , Quinn Thomas P
Published: April 2011

To characterize adult chinook salmon (Oncorhynchus tshawytscha) migratory behavior, we used ultrasonic tracking to describe their vertical and horizontal movements in upper Johnstone Strait, British Columbia during 1990-1992. Movement patterns varied: several fish showed a postrelease "escape" response and a protracted "recovery" period, with evidence of diel patterns of vertical and horizontal movements becoming apparent after 8 h. After release, 12 of the 32 chinook salmon that were tracked tended to dive deep. Chinook salmon that dived deep (>200 m) were significantly larger than fish that remained nearer the surface (mean fork length, 87.2 vs. 77.3 cm, respectively), and deep diving was not correlated with aspects of handling that might have stressed the fish. The mean depth of travel calculated over all tracks was 70 m and the maximum depths were between 300 and 400 m. Average depths of travel were shallower during the day (25-64 m) than at night (49-78 m). Overall, mean ascent and descent rates were similar (11-12 m/5 min). Gross travel rates (ground speed), defined as the distance moved during 5-min intervals, averaged 1.9 km/h, but tidal currents could have influenced these estimates. Net travel rates, defined as the distance between the point of release and track termination, were slower than gross rates, averaging 0.60 km/h. Average grounds speeds were more rapid during the day (1.9-3.2 km/h) than at night (1.7-2.5 km/h). Compared with sockeye salmon tracked in the same area during 1985-1986, chinook salmon moved more slowly, in both gross and net travel rates, and swam deeper.
Concentration of bat activity in riparian habitats over an elevational gradient
Authors: Grindal S D , Morissette J L , Brigham R M
Published: April 2011

Riparian areas are generally assumed to represent important foraging areas for insectivorous bats, but this contention has rarely been formally quantified. To test this assumption, we used bat detectors to compare the relative activity levels of a community of temperate-zone bat species between riparian (lake) and upland (cutblock) habitats at three different elevations (ranging from 540 to 1800 m) in a forested area of southern British Columbia. In addition, we also investigated the sex and age class distributions of bats (based on mist-net captures) between riparian and upland habitats among the elevational zones. Bat activity levels were significantly greater in riparian than upland areas (10 and 40 times greater for foraging and commuting activity, respectively). Capture rates were greater in riparian areas and biased towards females, suggesting that female bats may preferentially select riparian areas, probably because of the abundant prey resources typically associated with this habitat. Captures of females also predominated at lower elevations, whereas males were captured more often in higher elevation zones. Our data support the assumption that riparian habitats represent important foraging and probably drinking areas for bats. The sex bias and differences in capture rates and activity levels need to be considered when designing bat surveys in different habitat types or over elevational gradients.
Pitch separation as a possible jamming-avoidance mechanism in underwater calls of bearded seals (Erignathus barbatus)
Authors: Terhune John M
Published: April 2011

Bearded seals (Erignathus barbatus) produce simultaneous loud, long, narrowband underwater trills. It is likely that calls separated by 1/3 octave will not mask each other. Three call (trill) types were identified. Pitch separations between nearest-neighbour calls were measured by sampling at 1-s intervals. Calls spanned 5 octaves and were centred near 1 kHz. Mean pitch separations decreased significantly as the number of simultaneous calls increased from 2 to 9-11, but remained relatively constant at about 0.3 octave at higher numbers of simultaneous calls. For 2-12 simultaneous calls, the pitch separations between 0.0 and 0.4 octave were fewer than random. Proportions of the three trill types did not change as the numbers of simultaneous calls increased. All three call types had fewer pitch separations below 1/3 octave than between 1/3 and 2/3 octave. No relationship was found between pitch separation and call duration. Differences in starting pitch and the regular decline in pitch throughout most calls ensured that mean pitch separations of >1/3 octave were maintained even when many calls occurred simultaneously. Bearded seals may use pitch separation as a jamming-avoidance mechanism.
Responses of turtle assemblage to environmental gradients in the St. Croix River in Minnesota and Wisconsin, U.S.A.
Authors: DonnerWright Deahn M , Bozek Michael A , Probst John R , Anderson Eric M
Published: April 2011

We investigated how environmental gradients measured along the St. Croix River in Minnesota and Wisconsin, U.S.A., influenced the turtle assemblage. Among seven species, the five most common species were generalists and had wide distributions throughout the study area. However, patterns in assemblage structure were related to environmental gradients along the river. Sex ratios were male-dominated for the five most common species, and few or no juveniles were captured during the study. The first two canonical axes of a canonical correspondence analysis accounted for 92.7% of the variation in species-environment gradients. Most of the variation in distribution and abundance was attributed to gradients in channel morphology and physical characteristics along the river channel. Abundances of common snapping (Chelydra serpentina), false map (Graptemys pseudogeographica), and painted (Chrysemys picta bellii) turtles were associated with muck substrates and the number of basking sites (i.e., snags, rocks), which increased farther downstream. Abundance of spiny softshell turtles was closely related to increased water velocity and depth, which were related to hydraulic control points in the river. Abundance of common map turtles was associated with the presence of open sandy areas, uniform channel bottom, and gravel substrates. Geomorphic changes along the St. Croix River clearly influence the turtle assemblage and these specific relations should be considered in efforts to preserve and restore components of the assemblage.
Phylogenetic analysis of Gyrodactylus spp. (Platyhelminthes: Monogenea) using ribosomal DNA sequences
Authors: Cable J , Harris P D , Tinsley R C , Lazarus C M
Published: April 2011

Species of the viviparous monogenean genus Gyrodactylus are difficult to identify morphologically and relationships within the genus are unclear. Partial or complete sequences were obtained for the internal transcribed spacers (ITS-1 and ITS-2) and 5.8S ribosomal DNA (rDNA) of 11 Gyrodactylus species (G. kobayashii, G. gurleyi, G. pungitii, G. rogatensis, G. gasterostei, G. derjavini, G. salaris, G. rarus, G. turnbulli, G. bullatarudis, and G. arcuatus) and the related Gyrdicotylus gallieni. Phylogenetic analyses (parsimony, distance, and maximum likelihood) separated species of the Gyrodactylus wageneri species-group (with a long ITS-1) from those of the Gyrodactylus eucaliae and G. arcuatus species-groups (with a short ITS-1). This subdivision into species with a long (610-630 base pairs (bp)) or short (300-500 bp) ITS-1 was also apparent with 5.8S rDNA and ITS-2 data. No support could be found for the hypothesis that G. salaris is a member of a separate species group, as this species clustered within the G. wageneri group. The morphologically homogeneous G. wageneri group was subdivided by our molecular data into five species that infect cottids, gasterosteids, and salmonids and two species that infect cyprinid fishes. Overall, the ITS-2, combined with the 5.8S rDNA (an alignment of 668 bp), appeared to be the most informative indicator of phylogenetic relationships within the genus Gyrodactylus. The potential importance of this technique for future gyrodactylid systematics is discussed.
Natal dispersal of juvenile arctic ground squirrels in the boreal forest
Authors: Byrom Andrea E , Krebs Charles J
Published: April 2011

Natal dispersal is assumed to be costly because of the risk of mortality, yet rarely are movement patterns and survival of dispersers observed directly. We determined the fates and dispersal distances of 150 radio-collared juvenile arctic ground squirrels from 1993 to 1995 at Kluane, Yukon Territory, Canada (61°N, 138°W). We tested the hypothesis that dispersal has a high mortality cost, and we also attempted to distinguish among three hypotheses to explain natal dispersal: competition for mates, competition for resources, and inbreeding avoidance. Juveniles were radio-collared at emergence from the natal burrow on five 9-ha grids nested within larger (1 km2) experimental manipulations: two controls, a predator exclosure, a food-supplemented grid, and a predator exclosure + food grid. In all years and on all areas, dispersing juveniles were more likely to die than philopatric squirrels, and the risk of mortality increased with distance from the natal burrow for both sexes. Overall, survival of philopatric squirrels was 73%, whereas survival of dispersing squirrels ranged from a maximum of 40% to a minimum of 25%. Juvenile females were strongly philopatric independent of population density, except on the predator exclosure + food grid in 1995, where population density was extremely high and resources other than food were probably limiting. Resource competition may explain patterns of philopatry and dispersal in female arctic ground squirrels. Juvenile males moved farther from their natal site than females and more of them died. Males also had a strong tendency to disperse that was independent of food availability or population density, which suggests that male arctic ground squirrels ultimately may disperse to avoid either inbreeding with female relatives or intrasexual competition for mates.
Overcoming radiotelemetry bias in habitat-selection studies
Authors: Rettie W James , McLoughlin Philip D
Published: April 2011

For many species, determination of habitat selection is based on habitat-use data obtained through radiotelemetry. Recent papers pertaining to study techniques have largely ignored the effect of habitat-dependent bias in the performance of radiotelemetry systems. Such biases cannot be overcome by increasing radiotelemetry precision, excluding data, or increasing sample sizes, as the biases are centred around data that are missing or that contain habitat-dependent errors in location. The problem is best addressed at the data-analysis stage through the use of geographic information systems. We used Monte Carlo simulations to assess the effect of habitat-dependent bias in radiotelemetry studies on the assessment of habitat selection. We looked at the effects of habitat-patch size, level of telemetry signal inhibition, level of habitat co-occurrence, and selection pattern. We demonstrated that regarding use as the composition of habitat types within a circular area around each telemetry location can help to overcome the inaccurate assessment of habitat-selection patterns that biased data produce. The size of the circular area best able to overcome the bias is related to habitat patch size and to the level of association between two or more habitat types. Furthermore, we argue that the characteristics of habitat mosaics selected by animals can and should be studied in this way.
Demography of Peromyscus leucopus populations on habitat patches: the role of dispersal
Authors: Krohne David T , Hoch Greg A
Published: April 2011

We studied the demography of populations of the white-footed mouse, Peromyscus leucopus, inhabiting forest patches. Patch populations were characterized by high density, low rates of emigration and immigration, large temporal variance in density, low spatial variation in density, and high home-range overlap. There was no relationship between density and the distance from other forest patches. However, patches less than 2 ha in size had the highest mouse densities. Radiotelemetry, fluorescent-powder tracking, and trapping indicated that few mice disperse through grassland or agricultural fields surrounding patches. The recovery of a population from extinction was slower in more distant patches. We suggest that dispersal plays a key role in the demography of P. leucopus metapopulations that inhabit a landscape composed of a mosaic of large forest tracts, isolated forest patches, and agricultural fields.
Vigilance behavior in lactating female Alpine ibex
Authors: Toïgo Carole
Published: April 2011

We compared time budgets of lactating females with those of nonbreeding females, yearlings, and adult males in a French Alpine ibex (Capra ibex ibex) population. We tested whether lactating females spent as much time as other sex-age classes feeding, moving, resting, and being vigilant. Females with young at heel fed and moved as much as other sex and age classes, but rested less and were more vigilant. The decrease in time spent resting was possibly a way to minimize costs due to increased vigilance. The higher vigilance rate is considered to be an antipredation behavior exhibited by lactating females to protect their young.
Scanning electron microscopy of newly excysted juvenile and adult Cyclocoelum mutabile (Digenea)
Authors: Tajrine D D , Kapoor N N , McLaughlin J D
Published: April 2011

In this study, changes were examined in surface structures and tegumental morphology of newly excysted, migrating, and adult Cyclocoelum mutabile obtained from experimentally infected coots (Fulica americana). Newly excysted juveniles were spinous and had two large depressions situated at the anterior tip of the body and a large acetabulum. Small papillae were scattered around the mouth region and also formed a row that encircled the anterior end of the fluke. Four groups of larger papillae, two ventrolateral and two lateral, originated from points slightly posterior to the mouth region. The two ventrolateral bands of papillae terminated slightly posterior to the acetabulum; the two lateral rows of papillae terminated about three-quarters of the length along the specimen. Six large multilobed papillae were associated with the acetabulum. Juveniles migrating through the liver lost the spines and papillae by day 6, but the anterior depressions persisted into the adult stage. The tegument of 6- and 12-day-old flukes was smooth with a varying number of transverse folds. The tegument of 15-day-old specimens from the body cavity ranged in appearance from folded and pitted to reticulate. The reticulations were more prominent in adults and the entire body was covered with a reticulate pattern of loculus-like structures that are believed to aid in the movement of the flukes within the air sacs of the coot host.
Spatial distribution of Serengeti wildebeest in relation to resources
Authors: Wilmshurst John F , Fryxell John M , Farm Brian P , Sinclair ARE , Henschel Chris P
Published: April 2011

We investigated the spatial distribution of radio-marked wildebeest (Connochaetes taurinus) in the Serengeti ecosystem in relation to the distribution of their food resources, comparing patterns in the wet and dry seasons and at local and landscape spatial scales. A mechanistic model of ruminant energy optimization predicted that wildebeest should maximize energy intake on swards 3 cm high and maintain energy balance on swards between 3 and 10 cm high. At the ecosystem scale, wildebeest preferred short and intermediate-height grass of moderate greenness during both the wet and dry seasons. This was consistent with the model prediction which suggests that large-scale movements by wildebeest are motivated, at least partially, by an energy-maximizing strategy. At the local scale, however, wildebeest showed spatial selectivity only on the basis of grass greenness, not on grass height. This differed from model expectations and may have resulted from wildebeest exploiting ephemeral green flushes of grass caused by localized rainfall in their movement radius. According to these results, the influence of other nutritional or behavioural factors on wildebeest distributions is not rejected, yet they suggest the potentially important role of an energy intake maximizing strategy on movement patterns. Our findings show that wildebeest movements are broadly similar to those of other large herbivores that migrate in response to resource gradients.
Social bonding and aggression in female Roosevelt elk
Authors: Weckerly Floyd W
Published: April 2011

The relationship between degree of social bonding (extent of association among individuals) and level of aggression in ruminants is unclear. I examined social bonding and aggression in three groups of female Roosevelt elk (Cervus elaphus roosevelti) over 2 years. I hypothesized that when animals are socially bonded, bouts of aggression will be won by the individual initiating the aggression, occur quickly, and involve little physical contact, and the level of aggression does not correlate with group size. The degree of social bonding was high among individuals in all groups. Dyads of known individuals were together >80% of the time. A permutation analysis indicated that groups with the observed sizes had <0.001 chance of random association, except on one occasion when the probability was 0.72 for one group. Using focal-animal sampling, aggressive interactions were won 72% of the time by the initiator, occurred quickly (<5 s), and involved little physical contact, and the level of aggression was not correlated with group size. The level of aggression was, however, significantly lower in one of the groups. This group may have had access to more abundant food resources than the other groups. Socially bonded elk conducted aggressive interactions in a fashion that did not disrupt social stability.
The diet of the insectivorous Hawaiian hoary bat (Lasiurus cinereus semotus) in an open and a cluttered habitat
Authors: Jacobs David S
Published: April 2011

The Hawaiian hoary bat, Lasiurus cinereus semotus, foraged in both an open and a cluttered habitat. In the cluttered habitat it used slow, manoeuvring flight. In the open habitat it used rapid, less manoeuvring flight with echolocation calls of higher frequency than in the cluttered habitat. The combination of faster flight with higher frequency echolocation calls means that it should detect insect prey too late to manoeuvre for capture unless it preyed on relatively larger insects in the open habitat. The mean size of dietary items should therefore be greater in the open habitat than in the cluttered habitat. There should also be a greater preponderance of larger insects in the open than in the cluttered habitat to ensure that the use of rapid flight with higher frequency echolocation calls is efficient. I tested these predictions by comparing the diets and insect fauna in one open site with those in one closed site on the island of Hawai'i. As predicted, the dietary items were larger (t = 60.9, df = 259, p < 0.00001) in the open habitat (length = 18.9 ± 1.3 mm (mean ± SD); range 14-24 mm) than in the cluttered habitat (6.5 ± 1.6 mm; range 4-15 mm). In the cluttered habitat 86% of the insects fell into the three smallest length categories, while 52% of the insects in the open habitat fell into the two largest length categories. The preponderance of larger insects in the open habitat, with the consequent increase in detection range, enabled the bats to increase their flight speed despite their use of higher frequency echolocation calls. Rapid flight increases the rate at which insect prey are encountered and improves the foraging efficiency of bats. This provides evidence that bats are capable of altering their foraging strategy in response to prey characteristics and not just to the physical environment.
Bird predation affects canopy-living arthropods in city parks
Authors: Gunnarsson Bengt , Hake Mikael
Published: April 2011

Earlier studies suggest a significant top-down impact of vertebrate predators on arboreal arthropods. However, the general importance of such predator-prey interactions is not yet established. The impact of bird predation on macro-arthropods living in canopies of birch (Betula pendula) and oak (Quercus robur) was studied at six sites in four city parks in Göteborg, southwestern Sweden. In a 17-week field experiment we manipulated the bird-predation pressure on arthropods on birch and oak branches. Passerine numbers differed significantly between birch sites but not between oak sites. Bird predation significantly reduced the abundance on both birch and oak branches of seven out of nine arthropod taxa examined: Araneae, Opiliones, Dermaptera, Psocoptera, Heteroptera (oak only), Coleoptera, and Lepidoptera (birch only). For birch, arthropods were of larger average body size on experimental than on control branches at two sites. At the third site, however, arthropods were larger on control branches. For oak, arthropods were significantly larger on experimental than on control branches at two sites. At the remaining site, in the same park as the deviating birch site, there was no difference between size distributions. Thus, in one of the parks, experimental effects on size distributions at birch and oak sites contradicted the results from the other parks. Site effects on arthropod abundance were found for three insect taxa on birch and one insect taxon on oak. There were significant interactions between experimental treatment and site for Dermaptera on birch and for Araneae on oak. Although one of the parks (the central one) differed from the others in certain aspects, the results suggest that overall, bird predation was not seriously affected by the urban environment. We conclude that bird predation on arthropods is an important link in canopy food webs of temperate-zone forests.
Pivotal temperature and predicted sex ratios for hatchling hawksbill turtles from Brazil
Authors: Godfrey Matthew H , D'Amato Adriana F , Marcovaldi Maria Â , Mrosovsky N
Published: April 2011

Like all other species of sea turtle, the hawksbill turtle (Eretmochelys imbricata) exhibits temperature-dependent sexual differentiation, with high incubation temperatures producing females and low temperatures producing males. Relatively little is known about the sex ratios of hatchlings produced by nesting populations of hawksbill turtles. Here we estimate the overall seasonal sex ratios of hatchling hawksbill turtles produced in Bahia, Brazil, during 6 nesting seasons, based on incubation durations, pivotal temperature, and pivotal incubation duration. The overall sex ratio of hatchlings produced in Bahia from 1991-1992 through 1996-1997 was estimated to be >90% female, which is more female-biased than estimated sex ratios of hatchling loggerhead turtles from Bahia and Florida, U.S.A. The biological and conservation implications of skewed sex ratios are discussed.
Nesting ecology of Blanding's turtle (Emydoidea blandingii) in Nova Scotia, the northeastern limit of the species' range
Authors: Standing K Lorraine , Herman Thomas B , Morrison Ian P
Published: April 2011

This study was conducted to obtain accurate information on the reproductive ecology of the threatened population of Blanding's turtle (Emydoidea blandingii) in Nova Scotia. In 1994, 1995, and 1996, beaches and roadways in Kejimkujik National Park were surveyed for nesting turtles; all nests observed were covered with wire-screen cages to prevent predation and facilitate the collection of data on incubation and nest success. Nesting lasted from mid-June until early July. In each year, 80% of nesting occurred during a 10-day period in the third and fourth weeks of June. Turtles nested in the evening and predominantly on lakeshore cobble beaches. Site fidelity is high in this population: 73.3% of multiparous females returned to nest on the same beach in all years. No female produced more than one clutch per season, and most females (67.9%) nested less than annually. Mean clutch size was 10.6 eggs. Hatchlings emerge in September and October. Incubation times ranged from 80 to 128 days (mean = 94 days, SD = 11.7 days; n = 26 nests). In 1994 and 1995, most protected nests were productive; that is, 76.4 and 93.3% of protected nests produced at least one live hatchling in 1994 and 1995, respectively. In 1996, only 18.1% of protected nests were productive. Between 50 and 75% of productive clutches contained unhatched eggs and, on average, between 1.0 and 1.2 eggs failed per productive clutch. Total annual egg failure ranged from 26.5 to 94%. In the absence of nest predation, lower temperatures during incubation and nest flooding appear to be major cause of egg failure in this population. More effective means of reducing nest failure and bolstering recruitment must be implemented if efforts to aid the recovery of this threatened population of Blanding's turtle are to be successful.