bluuebunny/crossref_metadata_2025 huggingface dataset:
Breeding success, nest-site characteristics, and diet of Swainson's hawk (Buteo swainsoni) in a stable population in northern México
Authors: Rodríguez-Estrella Ricardo
Published: April 2011

Swainson's hawk (Buteo swainsoni) populations are declining in parts of their North American range, though apparently they are stable in other areas. Information on the species, ecological requirements and demographic characteristics throughout its distribution are needed to understand changes that affect its local status. In 1979 and 19851986, Swainson's hawks in the Mapimí desert in northern México nested on the top of 24 m high mesquite and yucca trees in "playas" (flat valleys). Dominant vegetation associations around the nests were species of ProsopisLarrea and ProsopisFouquieriaYucca. The first three factors of a principal component analysis explained 90% of the total variance, showing that topography, nest-tree structure, and distance to human activity were the factors most correlated with the presence of nests. Swainson's hawks in Mapimí fed mainly on ground squirrels (Spermophilus spp.), lizards (Phrynosoma spp. and Sceloporus spp.), and some groups of invertebrates (Coleoptera, Orthoptera). Prey and nest-site availability may be responsible for the high density and productivity of Swainson's hawk in the Mapimí desert.
Physiological and ecological aspects of low-temperature tolerance in embryos of the wood frog, Rana sylvatica
Authors: Frisbie Malcolm Pratt , Costanzo Jon P , Lee, Jr. Richard E
Published: April 2011

Wood frogs (Rana sylvatica) breed in late winter in temporary ponds, where eggs are deposited in communal surface rafts. Subsequently, developing embryos may face subzero temperatures. In the laboratory, individual embryos supercooled moderately (to 4.2°C for embryos in their jelly capsules; to 5.0°C for embryos removed from the jelly capsule) when chilled in the absence of external ice nuclei, but did not resist inoculative freezing when chilled in contact with external ice. They survived acute episodes (118 h) of supercooling to temperatures between ca. 0.5 and 2.0°C. Stage-12 embryos (six of six) survived freezing for 1 h at 2.0°C, but only one of six survived a 3.5-h freezing episode at the same temperature. Stage-13 and -14 embryos survived freezing episodes of 4.5 h at 1.0°C (six of six survived) and 18 h at 0.5°C (six of six survived), respectively. In the field, temperatures were monitored every 5 min for 21 d in embryo masses of wood frogs and Jefferson salamanders (Ambystoma jeffersonianum) at a breeding pond in central Kentucky. Wood frog embryos experienced higher daily maximum and lower daily minimum temperatures than salamander embryos, which were deeper in the water column. Wood frog embryos spent more time at risk of cryoinjury (i.e., at temperatures [Formula: see text]1°C), but the two species accumulated similar degree-days over the 21-d observation period. Their position in the water column may permit wood frogs to garner a developmental advantage in milder years, when daily minimum temperatures are similar between the two species. Wood frog embryos appear to offset some of the risks associated with this more exposed position by tolerating somatic freezing at high subzero temperatures.
The relative importance of body size, phylogeny, locomotion, and diet in the evolution of forelimb dexterity in fissiped carnivores (Carnivora)
Authors: Iwaniuk Andrew N , Pellis Sergio M , Whishaw Ian Q
Published: April 2011

Using a new rating scale of forelimb dexterity that separates the contribution of proximal components (shoulder, upper forelimb, and lower forelimb) from distal components (forepaw), we examined the relationship between functional demands and phylogeny and forelimb dexterity in 45 species of fissiped carnivores (Carnivora). Specifically, we examined the effects of body size, phylogenetic relatedness, diet (vertebrate predation), and locomotion (arboreality) on the differential evolution of forelimb dexterity. Regression analyses indicate that, although body size does appear to be positively correlated with the dexterity of the proximal components, the inclusion of phylogenetic information results in a nonsignificant relationship. Phylogenetic relatedness was found to account for a significant amount of interspecific variation in proximal, distal, and total (proximal + distal) dexterity. When phylogenetic effects were incorporated, arboreality was not significantly correlated with any of the dexterity scores, but vertebrate predation was, albeit a negative correlation. The amount of variation in the dexterity of proximal and distal components did, however, differ in magnitude within each significant result. Thus, each component can be differentially affected by specific functional demands. By examining the significant associations with diet and phylogeny and mapping the dexterity scores onto the phylogeny, we also demonstrate that the ancestral degree of forelimb dexterity of both the caniform and feliform lineages was approximately equal to that of the average extant carnivore. Thus, forelimb dexterity has decreased or increased within particular lineages, with reductions or elaborations in some species resulting from the invasion of specific niches not occupied by congeners.
Energy costs of chick rearing in Black-legged Kittiwakes (Rissa tridactyla)
Authors: Golet Gregory H , Irons David B , Costa Daniel P
Published: April 2011

We studied energy expenditure in adult Black-legged Kittiwakes (Rissa tridoctyla) with doubly labeled water to measure energy costs of chick rearing. We removed eggs from randomly selected nests and compared energy expenditure late in the chick-rearing period between adults raising chicks and adults whose eggs had been removed. Adults raising chicks expended energy at a rate 21% higher than adults from manipulated nests, apparently owing to differences in activity patterns while away from the colony. No sex-specific differences were detected in energy costs of chick rearing or energy expenditure, although statistical power for these analyses was fairly low. Among the unmanipulated group, energy expenditure tended to be positively related to natural brood size. An ancillary goal of our study was to test hypotheses that describe how population-level field metabolic rates (FMRs) vary during chick rearing. We compared FMRs among kittiwakes raising chicks at a colony in Alaska (61°09'N) with those reported for a colony in Norway (76°30'N). FMRs of adults raising chicks were nearly identical at the two colonies, suggesting that adults may have preferred levels of energy expenditure during chick rearing that are relatively invariant with environmental conditions, and that are not adjusted according to adult survival probabilities.
A numerical response of wolves to bison abundance in Wood Buffalo National Park, Canada
Authors: Joly Damien O , Messier François
Published: April 2011

The numerical response of predators to changing prey density is an important component of predator-prey dynamics. We examined factors influencing two indices of wolf (Canis lupus) abundance in Wood Buffalo National Park, Canada: historical wolf pelt harvests from 1970 to 1988 and sightings of wolves by park staff on survey flights from 1973 to 1991. We tested the effect of pelt price (adjusted to 1986-equivalent Canadian dollars), number of trappers, and bison (Bison bison) population size on wolf pelt returns for an 18-year period using a multiple linear regression model. We then tested the relationship between wolf sightings on survey flights and bison population size for an overlapping 19-year period. Wolf pelt price was a significant determinant of wolf harvest, whereas numbers of bison or trappers were not significant predictors of wolf harvest. However, there was a significant relationship between wolf sightings and bison population size. This analysis suggests that wolf population size was correlated with bison numbers, similar to the numerical response seen in other wolf-prey systems.
Inferring a classification of the Adenophorea (Nematoda) from nucleotide sequences of the D3 expansion segment (26/28S rDNA)
Authors: Litvaitis Marianne K , Bates Jeffrey W , Hope W Duane , Moens Tom
Published: April 2011

Nucleotide sequences of the D3 expansion segment of the 28S rDNA gene were used to reconstruct evolutionary relationships within the Adenophorea. Neighbor-joining and parsimony analyses of representatives of most major taxa revealed a paraphyletic Adenophorea (p = 0.0005). Within Adenophorea, the Enoplia, Enoplida, and Enoplina were paraphyletic (p = 0.0024, 0.0014, and 0.0120, respectively). A major division was evident within the Enoplida, with one lineage consisting of a basal Thoracostomopsidae and Enoplidae, and a second lineage consisting of Oncholaimidae and Encheliididae. Tripyloidina clustered close to the basal enoplid branch and formed a monophyletic taxon. Although appearing as paraphyletic in the maximum-parsimony and neighbor-joining trees, constraining Chromadoria and Chromadorida into monophyletic groups did not result in a longer tree. Within the Chromadoria, the order Desmodorida sensu Malakhov (1994) was paraphyletic. However, Desmodorida sensu Lorenzen (1994), which does not include Ceramonematidae, was monophyletic. Monhysterida formed a monophyletic order within Chromadoria, equivalent to Chromadorida and Desmodorida. The position of the Comesomatidae was tentatively identified among the Chromadorida, however, the possibility of their placement among the Monhysterida cannot be excluded completely.
Effects of laboratory ultraviolet radiation and natural sunlight on survival and development of Rana pipiens
Authors: Ankley Gerald T , Tietge Joseph E , Holcombe Gary W , DeFoe David L , Diamond Stephen A , Jensen Kathleen M , Degitz Sigmund J
Published: April 2011

Changes in solar ultraviolet (UV) radiation have been proposed as a possible factor contributing to seeming increases in hind-limb malformations in anuran amphibians in North America. One purpose of this study was to reproduce results from an earlier experiment (G.T. Ankley, J.E. Tietge, D.L. DeFoe, K.M. Jensen, G.W. Holcombe, E.J. Durhan, and S.A. Diamond. 1998. Environ. Toxicol. Chem. 17: 25302542) in which Rana pipiens (northern leopard frog) developed hind-limb ectromelia and ectrodactyly when exposed to an artificial source of UV radiation in the laboratory. Additionally, we sought to assess the effects of natural sunlight on survival and development in this species. Animals exposed to UV radiation in the laboratory from stage 2526 (just prior to hind-limb development) through forelimb emergence exhibited a dose-dependent elevation of hind-limb dysmorphogenesis. The observed malformations usually were bilateral and typically symmetrical, and consisted primarily of missing and reduced digits. Exposure of animals at this life stage to full intensity natural sunlight caused significant mortality, while exposure to screened sunlight (ca. 5060% of ambient) resulted in an elevated incidence of abnormal hind limb pathology (ectromelia, ectrodactyly) identical to that observed in organisms exposed to UV radiation in the laboratory. Owing to uncertainties in dose extrapolation, for example, in the context of animal behavior, the potential significance of our results in terms of explaining adverse effects in amphibians from the field is as yet unclear.
Experimental manipulation of predation and food supply of arctic ground squirrels in the boreal forest
Authors: Byrom Andrea E , Karels Tim J , Krebs Charles J , Boonstra Rudy
Published: April 2011

We examined whether arctic ground squirrel (Spermophilus parryii plesius) populations in northern boreal forest in the Yukon Territory, Canada, were limited by food, predators, or a combination of both, during the decline and low phases of a snowshoe hare cycle. From 1990 to 1995, populations were monitored in large-scale (1 km2) experimental manipulations. Squirrels were studied on eight 9-ha grids: four unmanipulated control grids, two food-supplemented grids, a predator-exclosure grid, and a predator-exclosure + food-supplemented grid. Population density was measured on all grids by livetrapping and active-season survival was measured using radiotelemetry. Population densities were lowest in 1992 and 1993 (2 years after the snowshoe hare population decline). Rates of population change were negative from 1991 to 1993, when predation pressure was most intense after the snowshoe hare decline, and positive from 1993 to 1995, when hares and predators were at low densities. Predation accounted for 125 of 130 mortalities (96%) of radio-collared squirrels. Adult survival was significantly lower in 1992 and 1993 than in 1994 and 1995, and was a strong predictor of annual rates of population change in arctic ground squirrels. Treatments were ranked as follows in their effect on adult survival: predator exclosure + food-supplemented > food-supplemented > predator exclosure > controls. Juvenile survival was lowest in 1992, and food addition and predator removal separately increased juvenile survival. On average, predator exclusion increased population densities twofold, food supplementation increased densities fourfold, and food supplementation and predator removal together increased densities 10-fold. We conclude that food and predation interact to limit arctic ground squirrel populations in the boreal forest during the decline and low phases of the snowshoe hare cycle. The snowshoe hare cycle may indirectly create a lagged secondary fluctuation in arctic ground squirrel populations through shared cyclic predators.
Regulation of chick provisioning in the thin-billed prion: an interannual comparison and manipulation of parents
Authors: Duriez Olivier , Weimerskirch Henri , Fritz Hervé
Published: April 2011

To investigate how thin-billed prions, Pachyptila belcheri, regulate their chick-provisioning behaviour, we compared data from two seasons with different food availability (1992 and 1997) and increased the costs of foraging by using load bands during 1997. The 1992 breeding season was poorer than 1997, but during both seasons parents used a two-part foraging strategy, mixing long trips, when they built up body reserves, with short trips, when they used previously stored reserves and foraged to feed the chick. In 1992, parents alternated long and short trips and spent more time on long trips, whereas in 1997 they performed several short trips before a long trip. As a consequence, provisioning rates were higher in 1997. Similarly, manipulated birds decreased their provisioning rates compared with control birds. During the two seasons, both control and experimental parents kept their body mass constant, and survival rates did not differ between seasons or groups. Using a logistic regression, we examined the factors influencing the decision whether, after a first short trip, to start a long trip or a second short trip. This decision was not influenced by the body condition of the chick, the meal mass, or the duration of the previous foraging trip, only by adult body condition. The results show that parents regulate their provisioning according to their body mass, which is the main factor influencing decisions concerning energy allocation between current reproduction and survival in this small long-lived seabird.
Season and ambient air temperature influence the distribution of mites (Proctophyllodes stylifer) across the wings of blue tits (Parus caeruleus)
Authors: Wiles P R , Cameron J , Behnke J M , Hartley I R , Gilbert F S , McGregor P K
Published: April 2011

Changes in the distribution of the wing-feather mite Proctophyllodes stylifer (Buckholz 1869) on the flight feathers of blue tits (Parus caeruleus) were studied throughout the seasons and in relation to ambient air temperature at three combinations of study sites (Lancashire, West Midlands, and South Midlands). We tested the hypotheses that the distribution of mites is influenced in part by season and ambient air temperature. In the winter months mites clustered predominantly on the tertiary feathers, whereas in late spring, summer, and autumn, mite-infestation scores were higher on the proximal primary and secondary feathers. Three approaches were employed to determine whether this seasonal redistribution of mites arose as a response to changes in microclimate, probably ambient air temperature, rather than to season per se. Firstly, meteorological data for the Lancashire study sites, and our own monitoring of the precise air temperature at the time of handling and inspection at the West Midlands study sites, enabled us to establish a link between distribution pattern and ambient temperature. Secondly, limited observations on the distribution of mites on birds recaptured when ambient air temperatures differed by 5°C or more between first and second nettings, one temperature being below 10°C and the other above, supported the idea that the change in distribution was associated with air temperature. Finally, the results of a small experiment in which heavily infested birds caught on a day when air temperatures ranged from 9 to 11°C were taken indoors and temporarily subjected to a higher ambient air temperature (20 min) prior to re-inspection and release also confirmed that mite movement was associated with the temperature of their environment. We conclude that the seasonal changes in distribution were driven by microclimatic changes, in part by temperature.
Delayed capelin (Mallotus villosus) availability influences predatory behaviour of large gulls on black-legged kittiwakes (Rissa tridactyla), causing a reduction in kittiwake breeding success
Authors: Massaro Melanie , Chardine John W , Jones Ian L , Robertson Gregory J
Published: April 2011

During 1998 and 1999, the impact of predation by herring gulls (Larus argentatus) and great black-backed gulls (Larus marinus) on breeding success of black-legged kittiwakes (Rissa tridactyla) at Gull Island, Witless Bay, southeastern Newfoundland, was quantified in relation to the timing of the annual arrival of capelin (Mallotus villosus) to spawn. The frequency of predation attempts by large gulls on kittiwakes was compared among three periods: before the mean hatching date for herring gulls, between the mean hatching date for herring gulls and the arrival of the capelin, and following capelin arrival. The frequency varied significantly among the three periods, being highest after gull chicks hatched but before the capelin arrived. The frequency of gull predation was significantly correlated with the percentage of kittiwake eggs and chicks that disappeared each week. We estimated that 43 and 30% of kittiwake eggs and chicks at Gull Island were taken by gulls in 1998 and 1999, respectively. Kittiwakes have been indirectly (through increased predation by gulls) affected by the delayed arrival and lower abundance of capelin in recent years, which underlines the need to understand multispecies interactions when interpreting the effects of human alteration of the marine environment.
Differential use of visual and chemical cues in predator recognition and threat-sensitive predator-avoidance responses by larval newts (Notophthalmus viridescens)
Authors: Mathis Alicia , Vincent Frank
Published: April 2011

For prey under the threat of predation, the ability to distinguish between different levels of danger can have important fitness consequences. Larval central newts, Notophthalmus viridescens louisianensis, distinguished between predatory (Ambystoma tigrinum tigrinum larvae) and nonpredatory (Hyla chrysoscelis/versicolor complex tadpoles) heterospecifics, but only when chemical cues were available. When only visual cues were present, larvae responded to both predatory and nonpredatory stimuli by reducing activity (fright response), but did not distinguish between the two types. Fine-scale discrimination of visual stimuli may have failed to develop because larval newts typically live in aquatic habitats in which chemical cues may be more reliable than visual cues, owing to large amounts of sediments and vegetation or possibly to myopia. Late-stage newt larvae that were approaching metamorphosis were unpalatable to A. t. tigrinum, and histological examination of the skin revealed that granular (poison) glands were present in the skin of late-stage but not early-stage larvae. Late-stage larvae did not distinguish between chemical stimuli from predators and nonpredators, which suggests that fright responses of larval newts are plastic and can be modified according to the level of perceived threat.
An experimental test of kin association in the house mouse
Authors: Dobson F Stephen , Jacquot Catherine , Baudoin Claude
Published: April 2011

Studies of genetic markers have suggested that female house mice (Mus musculus domesticus) prefer spatial association and nest sharing with close kin. Further, observations of mothers in single and communal nests suggest a potential advantage of association with kin, namely, improved reproductive success through cooperative defense of young against infanticide. In semi-natural enclosures, we tested for spatial association of female mice in small groups of sisters versus small groups of virtually unrelated females. We also examined success in producing and weaning litters by sisters versus mothers that were not close kin. Sisters exhibited greater spatial association than expected, although some groups of nonsisters showed close associations as well. All 14 sisters in the enclosures produced and weaned young in communal nests. Among 15 mothers that did not have sisters available, 4 did not produce litters, 2 shared a nest, and only 3 weaned young. Although infanticide occurred for both kinds of mothers, it was significantly more common in the single nests of nonsister mothers than for sisters. Thus, sisters were more successful at weaning young, probably owing to advantages of communal nesting. These results suggest that close female kin may associate spatially, and that there are distinct reproductive advantages due to the presence of close kin. The society of house mice is generally described as male dominated, but association of female kin may constitute the basis of social grouping in house mice.
Evolutionary biogeography of water shrews (Neomys spp.) in the western Palaearctic Region
Authors: Krystufek B , Davison A , Griffiths H I
Published: April 2011

We studied the morphology, DNA sequence, and Recent and Pleistocene distributions of three species of the water shrew genus Neomys (N. fodiens, N. anomalus, and N. teres) represented by samples from the Balkans and Asia Minor. Adaptations to semi-aquatic life (large body size, fringes of stiff hairs bordering the hind foot, and a tail keel) were most developed in N. fodiens and N. teres and least developed in N. anomalus. However, sympatric N. fodiens and N. anomalus did not differ significantly in relative braincase size. The three Neomys species clearly differed in glans penis morphology, N. teres being the most distinct, with a longer glans (length = 10.8-14.6 mm) than N. anomalus (7.0-8.0 mm) or N. fodiens (7.5-8.5 mm). Phylogenetic analysis placed N. fodiens as a sister-group to the anomalus-teres clade, based on both cytochrome b and 12S rRNA fragments. Palaeodistribution maps are presented for the three Recent taxa and the palaeospecies N. newtoni and N. browni. Possible evolutionary scenarios are proposed.
Conduction and coordination in deganglionated ascidians
Authors: Mackie G O , Wyeth R C
Published: April 2011

The behaviour of Chelyosoma productum and Corella inflata (Ascidiacea) was studied in normal and deganglionated animals. Chelyosoma productum lived for over a year after deganglionation and the ganglion did not regenerate. Electrophysiological recordings were made from semi-intact preparations. Responses to stimulation and spontaneous activity continued to be transmitted through the body wall and branchial sac after deganglionation. Spread was slow, decremental, and facilitative. Treatment with >10 µg·mL-1d-tubocurarine abolished all responses, indicating that nerves mediate conduction of excitation after deganglionation. Histological study using cholinesterase histochemistry and immunolabelling with antisera against tubulin and gonadotropin-releasing hormone showed no evidence of a peri pheral nerve net in regions showing conduction, contrary to previous claims. The cell bodies of the motor neurones were found to lie entirely within the ganglion or its major roots. Their terminal branches intermingled to form netlike arrays. Sensory neurons were identified with cell bodies in the periphery, in both the body wall and the branchial sac. Their processes also intermingled in netlike arrays before entering nerves going to the ganglion. It is concluded that the "residual" innervation that survives deganglionation is composed of either interconnected motor nerve terminals, interconnected sensory neurites, or some combination of the two. In re-inventing the nerve net, ascidians show convergent evolution with sea anemones, possibly as an adaptation to a sessile existence.
Preroosting behaviour of hooded crows (Corvus corone cornix)
Authors: Hansen H , Smedshaug C A , Sonerud G A
Published: April 2011

Gatherings of birds at preroosts before departure to nocturnal roosts have rarely been studied and their function is poorly understood. We recorded preroosting behaviour of hooded crows, Corvus corone cornix, in a mixed farmland-forest landscape in southeastern Norway during fall and winter, by selecting gatherings attended by at least one radio-tagged crow for observation. The preroosting crows perched in a highly aggregated and exposed group and did not forage. As the amount of snowfall during the preceding 24 h increased, an indication of sudden difficulty in finding food, the maximum number of crows that gathered increased, the duration of the gathering increased, and the straight-line distance covered by the radio-tagged crows from preroost to roost increased. The crows flew conspicuously in formation more often and for a longer time when on their way from preroost to roost on days with stronger winds. The results suggest that, in hooded crows, a preroost gathering is not simply a consequence of many individuals approaching the same roosting area but has some function, presumably that of maximizing the probability of finding rewarding food sites the next day by finding is a communal roost where information on the location of these sites may be obtained.
Seed selection in the Java Sparrow (Padda oryzivora): preference and mechanical constraint
Authors: van der Meij MA A , Bout R G
Published: April 2011

Very few studies address the effect of hardness on seed selection in granivorous birds. As a defense against predators, plant species may produce seeds of various hardnesses, some of which are too hard for a bird to crack. Unsuccessful cracking attempts lead to loss of time and, thus, lowers energy-intake rate. Birds may prefer seeds with a short handling time and a large chance of being cracked. However, without knowing the maximal cracking force of the bird, it is difficult to distinguish between seed selection as a result of mechanical constraints and selection as a result of preference. Our experiments aimed to discriminate between these two effects. During two series of experiments, Java Sparrows (Padda oryzivora) were offered safflower seeds. Size characters and hardness of the seeds that remained after feeding were compared with a control group. Without prior experience, the birds showed selection as a result of mechanical constraints. Seeds were chosen randomly and only seeds with a hardness less than the maximal crushing force were eaten, with the rest being rejected. After some experience, birds started to actively select for seed size (e.g., depth) and preferred to eat the smallest seeds. Although the correlation between size and hardness is low, the birds successfully used size characteristics as a predictor for hardness.
How temperature influences muscle and cuttlebone growth in juvenile cuttlefish (Sepia elliptica) (Mollusca: Cephalopoda) under conditions of food stress
Authors: Martínez Pilar , Bettencourt Vera , Guerra Ángel , Moltschaniwskyj Natalie A
Published: April 2011

Environmental factors influencing growth during the first stages of an animal's life cycle are determinative. External factors have often been implicated in the determination of rates of development of teleost larvae; however, the first stages of development of cephalopods remain poorly studied. In view of the fact that previous studies had shown that temperature is an important factor affecting cephalopod growth, particularly at high food concentrations, in this study the effect of temperature under conditions of non-satiation were investigated. A food-stress experiment was carried out for 75 days on 80 juvenile cuttlefish (Sepia elliptica) reared under two temperatures (25 and 30°C) and two food rations of glass shrimps Acetes sibogae australis at high and low proportions (2:1, respectively). We examined the effect of temperature and feeding regime on the growth of the whole animal, cuttlebone, and muscle tissue. Mantle-muscle blocks were 15% larger at 30°C than at 25°C, with the greatest difference in the middle mantle region (21% more at 30°C), whereas cuttlebone and somatic growth varied when the combination that included either the higher temperature or the higher food ration was used. Thus, at 30°C under the low feeding regime, final dorsal mantle length (DML) and cuttlebone growth index (CGI) were higher; however, at 25°C, final DML, CGI, and survivorship increased under the higher feeding regime. It was concluded that food scarcity may exaggerate the effect of small temperature differences. The results are discussed in the light of previous findings on the growth of other cuttlefish species, cephalopods, and teleosts.
Amplified fragment length polymorphism and mitochondrial sequence data detect genetic differentiation and relationships in endangered southwestern U.S.A. ambersnails (Oxylomaspp.)
Authors: Miller Mark P , Stevens Larry E , Busch Joseph D , Sorensen Jeff A , Keim Paul
Published: April 2011

The Kanab ambersnail (Oxyloma haydeni kanabensis) is a federally endangered mollusc currently known to reside in two locations in the southwestern U.S.A. To determine the extent of within- and between-population genetic variation of this taxon, the amplified fragment length polymorphism (AFLP) technique was used to generate 110 genetic markers among individuals sampled from the two Kanab ambersnail populations and from the only two known southwestern populations of the Niobrara ambersnail (Oxyloma haydeni haydeni) in Utah and northern Arizona. Additional information was obtained from sequence data of cytochrome b and cytochrome oxidase I gene fragments. Results suggest high levels of differentiation among populations, as evidenced through the application of UPGMA (unweighted pair-group method with arthimetic averaging) clustering, F statistics, and Fisher's exact test. Various levels of within-population genetic diversity were observed among populations. Expected heterozygosities ranged from 0.239 to 0.086 under a model assuming Hardy-Weinberg genotypic proportions and ranged from 0.205 to 0.061 under an obligate-selfing completely homozygous model. Results from cluster analyses showed that one Kanab ambersnail population and one Niobrara ambersnail population were more similar than the two Kanab ambersnail populations studied (supported by >80% of bootstrap replicates). These findings were further supported through the phylogenetic analysis of both mito chondrial gene fragments. The data suggest that taxonomic designations need revision, an act that will likely affect the protected status of some of the populations.
Trophic ecology of largemouth bass and northern pike in allopatric and sympatric assemblages in northern boreal lakes
Authors: Soupir Craig A , Brown Michael L , Kallemeyn Larry W
Published: April 2011

Largemouth bass (Micropterus salmoides) and northern pike (Esox lucius) are top predators in the food chain in most aquatic environments that they occupy; however, limited information exists on species interactions in the northern reaches of largemouth bass distribution. We investigated the seasonal food habits of allopatric and sympatric assemblages of largemouth bass and northern pike in six interior lakes within Voyageurs National Park, Minnesota. Percentages of empty stomachs were variable for largemouth bass (38-54%) and northern pike (34.7-66.7%). Fishes (mainly yellow perch, Perca flavescens) comprised greater than 60% (mean percent mass, MPM) of the northern pike diet during all seasons in both allopatric and sympatric assemblages. Aquatic insects (primarily Odonata and Hemiptera) were important in the diets of largemouth bass in all communities (0.0-79.7 MPM). Although largemouth bass were observed in the diet of northern pike, largemouth bass apparently did not prey on northern pike. Seasonal differences were observed in the proportion of aquatic insects (P = 0.010) and fishes (P = 0.023) in the diets of northern pike and largemouth bass. Based on three food categories, jackknifed classifications correctly classified 77 and 92% of northern pike and largemouth bass values, respectively. Percent resource overlap values were biologically significant (greater than 60%) during at least one season in each sympatric assemblage, suggesting some diet overlap.
Sexual dimorphism in the antennae of terrestrial isopods: a result of male contests or scramble competition?
Authors: Lefebvre F , Limousin M , Caubet Y
Published: April 2011

In Oniscidea (terrestrial crustaceans), males are known to have longer antennae than females. This sexual dimorphism may result from a variety of selection pressures. However, some species are well known for their highly aggressive males, which use their antennae as weapons. We tested the hypothesis that longer antennae in males have been selected for by means of antennal contests. Morphological analysis of the antennae and behavioral analysis of male dyads were performed in parallel on 7 species. We demonstrate significant sexual dimorphism of the antennae in 6 of the 7 species, and various forms of male aggressiveness depending on the species. Our hypothesis was rejected because we found a negative correlation between the use of the antennae in contests and the magnitude of sexual dimorphism. Furthermore, some species are sexually dimorphic but the males never compete using their antennae. We propose and argue that scramble competition to be the first to find receptive females could explain why males have longer chemoreceptive antennae.
Developmental changes in circulatory vitamin A (retinol) and its transport proteins in free-ranging harbour seal (Phoca vitulina) pups
Authors: Simms Wendy , Ross Peter S
Published: April 2011

Although vitamin A (retinol) levels are highly regulated within individual organisms, natural (e.g., age, sex, disease) and anthropogenic (e.g., environmental contaminants) factors can affect the dynamics of this essential nutrient. In this study, we examined developmental changes in the circulatory vitamin A system of free-ranging harbour seal (Phoca vitulina) pups by collecting serial blood samples from healthy known-age animals throughout their nursing period. While harbour seal pups were born with relatively low levels of circulatory retinol (144.4 ± 13.9 µg/L), nursing animals more than doubled these levels within 2 days (385.0 ± 46.9 µg/L), and levels continued to rise more gradually until weaning (431.0 ± 35.8 µg/L). Animals that were not nursing, such as orphaned (184.4 ± 34.2 µg/L), fasted (347.0 ± 14.4 µg/L), and weaned (204.5 ± 38.5 µg/L) pups, had significantly lower circulatory retinol levels. Despite the developmental changes observed in total retinol, the concentration of retinol bound by its transport proteins, retinol binding protein and transthyretin, remained relatively constant throughout the nursing period. This suggests that, like most mammals, the delivery of retinol to target tissues is highly regulated in harbour seal pups. Furthermore, the high concentrations of circulatory retinol observed in harbour seal pups may serve to saturate transport proteins, ensuring a steady delivery of vitamin A to target tissues during a period of potentially variable supply. Understanding how natural factors affect circulatory retinol and its transport proteins is an important facet of assessing the impact of environmental contaminants on vitamin A dynamics in marine mammals.
Habitat use and habitat selection by spotted seals (Phoca largha) in the Bering Sea
Authors: Lowry L F , Burkanov V N , Frost K J , Simpkins M A , Davis R , DeMaster D P , Suydam R , Springer A
Published: April 2011

Twelve spotted seals (Phoca largha) equipped with satellite-linked tags were tracked in the Bering Sea for 46-272 days during August-June 1991-1994. Alaskan seals were mostly near shore during August-October and 100-200 km offshore in January-June, and were broadly distributed in the region north of the 200-m isobath. Russian seals were located primarily near shore and within 100 km of the 200-m isobath during all months. During August-October, all seals were usually more than 200 km south of the sea-ice edge. In January-June, seals were mostly 0-200 km north of the sea-ice edge, often in areas with extensive ice coverage (7/10-9/10). We tested for habitat selection by determining how frequently a randomly moving seal would have been located in each habitat and comparing that with observed habitat use. Russian seals selected for nearshore and shallow-water areas in September-October and for near shore, within 25 km of the 200-m isobath, and the ice front during November-April. Alaskan seals selected for near shore areas in September-December; for offshore, shallow water, and the ice front in January-February; and for shallow water and pack ice in March-April. Biological processes associated with the highly productive "Green Belt" may have influenced the habitat use of Russian seals, but this did not appear to have been the case with Alaskan seals.
Nest mites (Pellonyssus reedi) and the reproductive biology of the house finch (Carpodacus mexicanus)
Authors: Stoehr Andrew M , Nolan Paul M , Hill Geoffrey E , McGraw Kevin J
Published: April 2011

We investigated the effects of a hematophagous nestling mite (Pellonyssus reedi, Acari: Macronyssidae) on the reproductive biology of the house finch (Carpodacus mexicanus) in east-central Alabama, U.S.A. Mites were absent from nests for the first half of the breeding season, but after their initial appearance they increased in number and were present in almost all nests. High nest-mite levels were associated with decreased nestling mass and hematocrit, but not with decreased nestling tarsus length. Experimental elimination of mites from some nests confirmed that the effects observed were mite-induced, not seasonal. The plumage colour of breeding adult male house finches was not correlated with nest-mite levels, nor did it appear that redder males' offspring suffered less from the effects of mites. Adult house finches fed nestlings from highly parasitized nests less often than those from nests with few or no mites. It appears unlikely that mites are directly involved in the sexual selection of bright male plumage coloration in this population of house finches. However, it is known that early-nesting females preferentially pair with redder males, therefore the benefit of nesting early and avoiding mite infestations is greater for redder male house finches.
Geographic variation in foraging patterns of pre-incubating female Mallards
Authors: Dugger B D , Petrie M J
Published: April 2011

Differences in productivity between habitats in different parts of a duck's breeding range may influence how birds allocate time to meet the exogenous nutritional requirements of clutch formation. However, no study has compared activity patterns between birds in different portions of their breeding range. We used focal-bird observations to compare the time-activity patterns of pre-incubating female Mallards (Anas platyrhynchos) in the prairie pothole region of Manitoba and North Dakota with those in eastern forested New Brunswick. Birds in eastern Canada had higher foraging effort (63.7 vs. 41.6%, P < 0.01) and spent less time in comfort (12.2 vs. 7.6%, P = 0.01) and locomotion (12.7 vs. 4.1%) activities than birds on the prairies. Females responded to lower productivity by devoting more time to foraging, which may be why Mallards in eastern Canada are able to lay first clutches that are equal in size to those of prairie Mallards.
Display-area size, tenure length, and site fidelity in the aquatically mating male harbour seal, Phoca vitulina
Authors: Van Parijs Sofie M , Janik Vincent M , Thompson Paul M
Published: April 2011

Previous studies of the distribution and activity of male harbour seals, Phoca vitulina, based on telemetric techniques have shown that males restrict their range at the onset of the mating season and perform vocal and dive displays. While these data illustrated broad changes in male behaviour and distribution, they were not precise enough to reveal the extent to which individual males repeatedly return to the same locations to display. In this study we used an acoustic array to localise male vocalisations. This technique provided small-scale information on male behaviour over 3 consecutive years. This study provides the first details concerning display-area size in an aquatically mating phocid. Male vocalisations were located in two discrete areas each covering between 40 and 135 m2. Vocalisations were repeatedly located in these two areas over the 3-year period. Comparisons of four vocal parameters suggested that only one individual occupied each area throughout a mating season. Furthermore, comparative analysis suggested that males might return to the same two display areas in successive years. Although the number of males using the site was small, this study showed that acoustic localisation can be a valuable tool for detailed study of the underwater behaviour of aquatically mating pinnipeds.
The standard energetics of mammalian carnivores: Felidae and Hyaenidae
Authors: McNab Brian K
Published: April 2011

Data concerning the energy expenditure of nine species in the family Felidae and one species in the family Hyaenidae are presented, all of which were obtained under standard conditions. An examination of basal rates of metabolism in these felids and in two species reported in the literature indicates that basal rate is primarily correlated with body mass; of these species, nine have a high basal metabolic rate by general mammalian standards, the two exceptions being the margay and jaguarundi. The low basal metabolic rate of the margay may be related to its arboreal habit in association with small muscle mass, but the reason for the low rate in the jaguarundi is unknown. The omnivorous striped hyaena and termitivorous aardwolf have typical mammalian basal rates. Felids that weigh less than 7 kg have slightly low minimal thermal conductances relative to mammals generally; larger species have high conductances. Felids have slightly high body temperatures.
Prey preferences ofPhaeacius malayensis, a spartaeine jumping spider (Araneae: Salticidae) from Singapore
Authors: Li Daiqin
Published: April 2011

Phaeacius malayensis (Salticidae: Spartaeinae) is an atypical jumping spider that routinely includes other jumping spiders in its diet. This paper presents the first detailed study of P. malayensis' prey preferences. Three basic types of tests of prey preference were used: different types of prey were provided on alternate days (alternate-day tests), two types of prey were provided simultaneously (simultaneous-presentation tests), and an alternative prey type was provided while the predator was already feeding (alternative-prey tests). In alternate-day and simultaneous-presentation testing, but not in alternative-prey testing, (i) P. malayensis preferred spiders (salticids and hunting spiders) to insects; (ii) P. malayensis preferred salticids to hunting spiders; (iii) these preferences were not exhibited in some paired choices when the background was nonmatching, indicating that visual concealment is important with respect to some, but not all, prey; (iv) P. malayensis' prey preferences were not affected by a prior 14-day period without food; (v) after 21 days of fasting, P. malayensis took different types of prey indiscriminately. The adaptive significance of preferences for particular types of prey is discussed in the context of optimal-foraging theory.
The spatial component of variation in small-mammal abundance measured at three scales
Authors: Bowman Jeff , Forbes Graham J , Dilworth Tim G
Published: April 2011

We studied small-mammal populations across a range of spatial scales to determine if they exhibited spatial variability that was independent of the distribution of vegetation. Between 1996 and 1999, systematic livetrapping surveys were conducted on nested grids at three scales: (1) extent (total area covered by a grid) = 4900 ha, grain (minimum space between sampling points) = 1000 m; (2) extent = 306 ha, grain = 250 m; and (3) extent = 31 ha, grain = 125 m. The four most abundant species were the red-backed vole (Clethrionomys gapperi), the short-tailed shrew (Blarina brevicauda), the deer mouse (Peromyscus maniculatus), and the woodland jumping mouse (Napaeozapus insignis). Small mammals exhibited spatial population structure over distances up to 250 m but not over 1000 m. There was a component of this population structure that appeared to be temporally and spatially dynamic, and that was not correlated with measured vegetation variables. We discuss processes that would create the observed metapopulation structure in seasonal landscapes.
Effects of experimental food restriction and body-mass changes on the avian T-cell-mediated immune response
Authors: Alonso-Alvarez Carlos , Tella José L
Published: April 2011

The T-cell-mediated immune response (CMI) of birds, measured with the phytohaemagglutinin skin test, is in most cases positively correlated with their body mass. This correlation, however, does not imply causality, since high-quality birds may be more immunocompetent as well as heavier at the time of sampling. We assessed this relationship experimentally by measuring the changes in body mass and CMI in individual captive yellow-legged gulls (Larus cachinnans) maintained with food provided ad libitum (control group), with no food (fasting group), or with one-third of their daily food requirements (subfeeding group). We identified a direct, nonlinear relationship between food intake, body mass, and CMI. Before the experiment started, body mass of birds (corrected for size) fed ad libitum did not correlate with their CMI, while a positive correlation was found after food restriction. This suggests that birds may reach a threshold above which increases in food intake and body mass do not enhance CMI. Thereafter, food restriction caused decreases in CMI that were significantly correlated with the percentage of body mass lost by each bird. However, for birds that lost similar proportions of body mass, changes in CMI varied according to food-restriction treatment, the subfeeding group exhibiting a stronger CMI than the fasting group.