bluuebunny/crossref_metadata_2025 huggingface dataset:
Natural otolith microstructure patterns reveal precise homing to natal incubation sites by sockeye salmon (Oncorhynchus nerka)
Authors: Quinn Thomas P , Volk Eric C , Hendry Andrew P
Published: April 2011

Experimental results suggest that anadromous salmon and trout learn (imprint) the odors of their natal site just prior to or during seaward migration. In contrast, information on the life histories of several species and the genetic structure of populations indicate that they must imprint earlier in life, probably during incubation in the gravel or when they emerge as free-swimming fry. To test the hypothesis that sockeye salmon (Oncorhynchus nerka) home to their incubation-emergence sites (rather than just to the lake where they reared before migrating to sea), we took advantage of the natural variation in otolith microstructure caused by differences in thermal regimes during incubation. We collected otoliths from adult sockeye salmon that returned to discrete spawning areas in Iliamna Lake, Alaska, and Lake Washington, Washington, and, in blind trials, these were classified based on comparison with otoliths from juveniles from the same sites and using information on site-specific thermal regimes. Our analysis showed that the salmon were much more likely to return to their natal incubation site than would have occurred by chance. Estimated straying rates were about 0.1% from the Woody Island population to the Pedro Pond population in Iliamna Lake and about 1% from the Cedar River population to the Pleasure Point population in Lake Washington. The results were consistent with genetic evidence for fine-scale structure of salmon populations and with conservation based on spatial scales appropriate for the early life history of the fish.
Effects of individual variation in age and size at metamorphosis on growth and survivorship of southern toad (Bufo terrestris) metamorphs
Authors: Beck Christopher W , Congdon Justin D
Published: April 2011

We conducted two experiments with the southern toad (Bufo terrestris) to examine whether individual variation in (i) metamorph body size and metabolic rate and (ii) age and size at metamorphosis were related to differences in survivorship or growth rate of postmetamorphic individuals. Results from the first experiment indicated that neither initial body size nor metabolic rate was related to survivorship or growth. Results from the second experiment showed that (i) size at metamorphosis was positively correlated with survivorship to first census (after 2 weeks), (ii) age and size at metamorphosis had no significant effect on survivorship from first to second census (after 2 months), (iii) size at metamorphosis had a marginally significant positive effect on survivorship from metamorphosis to second census, and (iv) age and size at metamorphosis were not significantly correlated with total growth. Our results suggest that in the southern toad, size at metamorphosis may lead to early differences in survival, size, and growth that later disappear. Furthermore, early differences in growth and survival attributable to size at metamorphosis are not due to size-related differences in metabolic rate. Therefore, although age and size at metamorphosis affect metabolic rate, they may not be related to fitness via effects on postmetamorphic survival and growth.
Gap junctions in the limb regeneration blastema of the axolotl,Ambystoma mexicanum, are not distributed uniformly and are regulated by retinoic acid
Authors: Miller Leigh-Anne D , Farquhar Melissa L , Greenwood John S , Scadding Steven R
Published: April 2011

Gap junctions are thought to play a role in pattern formation during limb development and regeneration by controlling the movement of small regulatory molecules between cells. An anteroposterior gradient of gap junctional communication that is higher posteriorly has been reported in the developing chick limb bud. In both the developing chick limb bud and the amphibian regenerating limb, an anteroposterior retinoic acid gradient is present, and this is also higher posteriorly. On the basis of these observations, we decided to examine the role of gap junctional communication in the regenerating amphibian limb. Gap junctions were observed in both the axolotl, Ambystoma mexicanum, limb regeneration blastema and cardiac tissue (as a positive control), using immunohistochemical labelling and laser scanning confocal microscopy. The scrape-loading/dye transfer technique for tracing the movement of a gap junction permeable dye, Lucifer yellow, showed that in blastemal epidermis there were nonuniform distributions of gap junctions in both the dorsoventral and anteroposterior axes of the blastema. Retinoic acid was found to increase gap junctional permeability in blastemal epidermis 48 h after injection and in blastemal mesenchyme 76 h after injection. The potential role of gap junctions during pattern formation in limb regeneration is discussed based on these results.
Vitamin E and vitamin A contents, fatty acid profiles, and gross composition of harp and hooded seal milk through lactation
Authors: Debier C , Kovacs K M , Lydersen C , Mignolet E , Larondelle Y
Published: April 2011

This study reports fatty acid profiles and vitamin A and vitamin E contents of the milk of the harp seal (Phoca groenlandica) and hooded seal (Cystophora cristata) throughout the lactation period, as well as standard compositional analyses. The milk for this study was collected from harp and hooded seals breeding on the pack ice in the Gulf of St. Lawrence. Mother-pup pairs were serially captured, or point-sampled, in order to obtain milk samples during different lactation stages. Milk lipids showed the respective species' typical patterns during lactation, with a significant increase for harp seal milk and a relatively constant value for hooded seal milk. The profiles of most of the milk fatty acids remained relatively stable over the course of lactation in both species. Vitamin A content was also quite stable through lactation. By contrast, vitamin E content underwent a dramatic drop between the day of birth and early lactation for harp seals and from birth to midlactation for hooded seals. It then continued to decrease at a slower rate until the end of lactation in both species. The highest vitamin E content of colostrum reached 125 mg/kg of milk for harp seals and 200 mg/kg of milk for hooded seals. These concentrations subsequently dropped to 20-50 mg/kg of milk by early or mid lactation. These changes in this lipophilic, antioxidizing vitamin were not correlated with milk lipid content or its polyunsaturated fatty acid profiles.
Atlantic salmon, Salmo salar L., and Arctic char, Salvelinus alpinus (L.): comparative correlation between iodine-iodide supplementation, thyroid hormone levels, plasma cortisol levels, and infection intensity with the sea louse Caligus elongatus
Authors: Mustafa A , MacKinnon B M
Published: April 2011

The interrelationship between plasma cortisol levels, iodine-iodide nutritional supplementation, plasma thyroid hormone levels (tri- and tetra-iodothyronine, T3 and T4 respectively), and infection intensity with the sea louse Caligus elongatus were investigated in Atlantic salmon, Salmo salar L., and Arctic char, Salvelinus alpinus (L.). Cortisol-implanted Atlantic salmon had significantly higher mean intensities of sea lice than salmon not implanted with cortisol. Untreated Arctic char had significantly higher plasma cortisol levels and sea lice infections than untreated salmon. Cortisol-implanted salmon had lower plasma levels of T3 and T4. Salmon and char treated with iodized feed and iodinated water had higher plasma T3 and T4 levels, higher plasma T3/T4 ratios, and lower plasma cortisol levels than controls. Sea lice infections were significantly reduced on salmon treated with either iodized feed (P < 0.05) or iodinated water (P < 0.05). Char treated with iodized feed also had significantly reduced infections (P < 0.05). In general, iodized feed had a greater effect than iodinated water in reducing sea lice numbers. This study indicates that elevated plasma cortisol levels in salmon and char result in lower plasma levels of thyroid hormone and an increased susceptibility to sea lice infections. It is concluded that providing the fish with sufficient iodine-iodide increases thyroid hormone levels, reduces plasma cortisol levels, and reduces susceptibility to sea lice infections.
Protective effects of calcium against the physiological effects of exposure to a combination of cadmium and copper in rainbow trout (Oncorhynchus mykiss)
Authors: Richards Jeff G , Playle Richard C
Published: April 2011

We report that an elevated aqueous calcium (Ca) concentration protects against acute respiratory and osmoregulatory action due to exposure to a combination of cadmium (Cd) and copper (Cu) in rainbow trout (Oncorhynchus mykiss), but does not protect against longer term ionoregulatory disruption. Trout exposed to 0.18 µM Cd and 0.80 µM Cu in soft water (40 µM Ca, 440 µM Na, pH 6.6) experienced a 60-torr decrease in arterial oxygen tension, a 5.5 mM increase in blood lactate concentration, and severe haemoconcentration as indicated by a 1.4-fold decrease in mean cell haemoglobin concentration, all of which occurred within 24 h. The addition of Ca to soft water (to reach 910 µM Ca, added as CaCl2; 430 µM Na, pH 6.8) eliminated these severe effects and slowed Cd uptake by the gills, plasma, and liver of trout, probably through competition for binding at gill Ca channels, but Ca did not affect Cu uptake by the gills or its entry into the plasma. Associated with slower Cd accumulation and unchanged Cu accumulation in the plasma were slow decreases in plasma concentrations of Na, Cl, and Ca, which were prevented initially by adding Ca to the water. Modelling using a modified aqueous chemistry computer program, MINEQL+, and previously published gill binding constants accurately simulated the initial (18 h) accumulation of Cd and Cu by trout gills and thus predicted acute toxicity, but our model did not adequately simulate the physiological mechanisms of Cd accumulation by trout gills over longer exposures up to 130 h.
Assessment of mitochondrial DNA structuring and nursery use in the North Atlantic right whale (Eubalaena glacialis)
Authors: Malik S , Brown M W , Kraus S D , Knowlton A R , Hamilton P K , White B N
Published: April 2011

The North Atlantic right whale (Eubalaena glacialis) inhabits five areas along the east coast of North America at different times of the year. During 17 years of field observations, it has been found that only 59% of the newborn calves are brought to the Bay of Fundy nursery area. To examine whether this is because of population structuring, the mitochondrial DNA (mtDNA) control region haplotypes were determined for 269 individuals. Seven polymorphic sites were found to define five haplotypes. Calves were divided into two groups based on whether or not they were brought to the Bay of Fundy nursery. Significant genetic structuring of mitochondrial haplotypes was found between these groups (p = 0.002). Mothers that have had more than three calves demonstrated significant fidelity (p = 0.005) to the Bay of Fundy, suggesting that philopatry is the basis for the genetic structuring. Although this study clearly identifies the existence of two subpopulations and an alternative nursery area(s), the location(s) of the alternative area(s) is unclear and remains an important issue for the conservation of the species.
Regional variation in muscle metabolic enzymes in individual American shad (Alosa sapidissima)
Authors: Leonard JBK
Published: April 2011

Evaluation of the activity of metabolic enzymes is often used to assess metabolic capacity at the tissue level, but the amount of regional variability within a tissue in an individual fish of a given species is frequently unknown. The activities of four enzymes (citrate synthase (CS), phosphofructokinase, lactate dehydrogenase (LDH), and β-hydroxyacyl coenzyme A dehydrogenase (HOAD)) were assayed in red and white muscle at 10 sites along the body of adult American shad (Alosa sapidissima). Red and white muscle HOAD and white muscle CS and LDH varied significantly, generally increasing posteriorly. Maximal variation occurs in red muscle HOAD (~450%) and white muscle LDH (~60%) activity. Differences between the sexes also vary with sampling location. This study suggests that the variability in enzyme activity may be linked to functional differences in the muscle at different locations, and also provides guidelines for sample collection in this species.
Predation on different-sized quail eggs in an artificial-nest study in western Newfoundland
Authors: Lewis Keith P , Montevecchi William A
Published: April 2011

In artificial-nest studies, Japanese Quail (Coturnix japonica) eggs have been used as surrogates for passerine eggs, although small mammals that prey on passerine eggs may be unable to consume Japanese Quail eggs. To determine the influence of egg size on nest predation in different landscapes on insular Newfoundland, we placed either a Japanese Quail egg or a smaller Chinese Painted Quail (Xexcalfactoris chinensis) egg in artificial ground nests along lakeshore forest edges and along riparian buffer strips. Clay eggs were used to identify nest predators. Levels of predation on nests with Japanese Quail and Chinese Painted Quail eggs were similar. Based on clay eggs, predation was attributed to red squirrels (Tamiasciurus hudsonicus), and we found no evidence that smaller mammals preyed on artificial nests. We conclude that the Japanese Quail egg is acceptable for use in artificial-nest studies in Newfoundland, and we discuss the implications of egg size and small mammals in nest-predation experiments.
The relationship between forelimb morphology and behaviour in North American carnivores (Carnivora)
Authors: Iwaniuk Andrew N , Pellis Sergio M , Whishaw Ian Q
Published: April 2011

We tested the validity of previously described relationships between forelimb structure and behaviour in mammals by measuring the forelimbs of 22 species of North American carnivores. Nine ratios were calculated from these measurements and made independent of the effects of allometry and phylogeny through the use of log-transformed regressions and independent contrasts analysis. The ratios were then directly compared with two behavioural traits: arboreal locomotion and vertebrate predation. Only five of the nine ratios exhibited a significant relationship with arboreal locomotion and three with vertebrate predation. It was concluded that the brachial index, relative size of the olecranon process, and total forelimb robusticity may be reliable predictors of arboreal locomotion, and that the brachial index, relative size of the olecranon process, and radial robusticity may be accurate predictors of vertebrate predation. The data also suggest that the morphology of the lower forelimb may be an important indicator of prey-capture and feeding behaviour in carnivores and could be used in conjunction with craniodental variables to extrapolate predatory behaviour of extinct species.
Genetic variation in susceptibility of Atlantic salmon to the sea louse Caligus elongatus Nordmann, 1832
Authors: Mustafa A , MacKinnon B M
Published: April 2011

Differences in susceptibility of distinct full-sibling families of Atlantic salmon, Salmo salar, to infection with the sea louse Caligus elongatus were investigated. Infection intensity with mobile stages of sea lice was monitored on 419 individual salmon from 73 full-sibling families held in a single sea pen and exposed to similar numbers of infectious larvae originating from nearby fish. The average intensity of infection calculated from the family groups ranged from 5 to 25, with 70 families having an average intensity of 10 or more preadult or adult sea lice. The overall average intensity was 15.30 and the prevalence was 100%. The calculated genetic heritability (h2) was 0.22, which indicates that this variability in susceptibility to infection may be heritable. This level of heritability also suggests that selection for improved resistance to sea lice is feasible.
Effect of experimental 3,5,3'-triiodothyronine hyperthyroidism on thyroid hormone deiodination in brain regions and liver of rainbow trout,Oncorhynchus mykiss
Authors: Fines Glenn A , Plohman James , Eales J Geoffrey
Published: April 2011

We studied the effect of 3,5,3'-triiodothyronine (T3) hyperthyroidism, induced by 12 ppm T3in food for 10 days, on the low-Kmactivities of thyroxine (T4) outer-ring deiodination (ORD) to form T3, T4inner-ring deiodination (IRD) to form 3,3',5'-triiodothyronine (reverse T3(rT3)), T3ORD to form 3,5-diiodothyronine (3,5-T2), and T3IRD to form 3,3'-diiodothyronine (3,3'-T2) in six brain regions and in liver of immature rainbow trout (Oncorhynchus mykiss) at 12°C. Throughout the brain, T4ORD activity of control trout was uniformly low and T3ORD activity was negligible. T4IRD and T3IRD activities were about 5-fold and 50-fold greater, respectively, than T4ORD activity and were higher in the optic lobes, hypothalamus, and telencephalon/olfactory bulbs than in the medulla or cerebellum. T3treatment doubled the plasma T3level with no change in plasma T4level and reduced T4ORD and T4IRD activities in all brain regions but did not alter T3IRD activity or the negligible T3ORD activity. Relative to controls, T3treatment reduced liver T4ORD activity 6-fold, increased T4IRD activity 8-fold, and increased T3IRD activity 12-fold. We conclude that (i) there are regional differences in trout brain T4IRD and T3IRD activities but not in T4ORD activity, indicating spatial variation in brain T4and T3catabolism, (ii) in response to a mild T3challenge the brain deiodination pathways do not undergo the same autoregulatory adjustments as those in liver, and (iii) a T3challenge reduces brain T4IRD activity with no change in T3IRD activity, which suggests that the two IRDs may be controlled by separate deiodinases.
Compensatory effect of the heat increment of feeding on thermoregulation costs of white-tailed deer fawns in winter
Authors: Jensen Paul G , Pekins Peter J , Holter James B
Published: April 2011

For northern white-tailed deer (Odocoileus virginianus) fawns, the energetic cost of thermoregulation (HcE) during severe winters can result in substantial catabolism of body-tissue reserves. The heat increment of feeding (HiE) has the potential to offset thermoregulatory energy expenditure that would otherwise require the catabolism of these reserves. During winters 1996 and 1997, we conducted 18 fasting and 18 on-feed heat-production trials using indirect respiration calorimetry in a metabolic chamber. Nonlinear regression analysis was used to estimate the lower critical temperatures (Tlc) and determine the fasting metabolic rate (FMR) and resting metabolic rate (RMR). Resulting models were used to calculate HiE, HcE, and percent substitution of HiE for HcE. For fawns fed a natural browse diet, estimated FMR and RMR were 352 and 490 kJ·kg body mass (BM)-0.75·d-1, respectively; this 40% increase in thermoneutral heat production reduced Tlc from -0.8 to -11.2°C between the fasted and fed states, respectively, and reduced HcE by 59% for fed fawns. For fawns fed a concentrate diet, estimated FMR and RMR were 377 and 573 kJ·kg BM-0.75·d-1, respectively. Level of browse intake had a significant effect on RMR andTlc. RMR was 12% higher for fawns on a high versus a low level of intake, and estimated Tlc was -15.6 and -5.8°C, respectively. Our data indicate that the energetic cost of thermoregulation is probably a minor portion of the energy budget of a healthy fawn consuming natural forage.
Scale-dependent trade-offs in foraging by European roe deer (Capreolus capreolus) during winter
Authors: Mysterud Atle , Lian Lise-Berith , Hjermann Dag Øystein
Published: April 2011

We studied food preferences of and patch and habitat selection by European roe deer (Capreolus capreolus) by snow-tracking radio-tagged individuals. To account for the possible biases caused by patch/habitat selection on measures of food preference, we adopted a new method in which diet choice is compared with availability within each forage patch successively rather than to some home-range or study-area average. There was no difference in food preference between males and females or between day and night. When compared with that in random sites 50 m from feeding sites (patch scale), selection was random with regard to cover; however, the food availability index was higher for feeding sites than for random sites. Roe deer selected feeding sites with more cover during cold weather, whereas the food availability index had no effect at this scale (habitat scale). Roe deer selected more open habitat and feeding sites closer to human settlement at night and as snow depth increased. Females tended to select foraging sites that were more hidden than those of males. There was direct evidence of a trade-off between selection of food availability and both canopy cover and distance to human settlement but not between food availability and concealment cover.
Begging behaviour and its energetic cost in great spotted cuckoo and magpie host chicks
Authors: Soler Manuel , Soler Juan J , Martínez Juan G , Moreno Juan
Published: April 2011

Begging is one of the main factors governing food delivery to chicks by adult birds and it is of great importance in studies of biological communication theory. Many theoretical models have been proposed to explain the evolution of this noisy and conspicuous behaviour, all of which assume that begging activity is energetically costly. We show that both great spotted cuckoo (Clamator glandarius) brood-parasitic chicks and magpie (Pica pica) host chicks ceased to beg after ingesting enough food, and that great spotted cuckoo chicks emitted more begging calls and begged for much longer than did magpie chicks. Using the doubly labelled water method to measure the daily energy expenditure of begging and nonbegging chicks in the laboratory, we show that begging behaviour consumes only a small quantity of oxygen compared with other avian activities usually assumed to be energetically costly.
Patterns of fatty acid composition in free-ranging yellow-bellied marmots (Marmota flaviventris) and their diet
Authors: Hill V L , Florant G L
Published: April 2011

In the laboratory, dietary polyunsaturated fatty acids (PUFAs) are conserved in the tissues of hibernators and are important for normal hibernation. Prior to this study, it was unknown if PUFAs are similarly conserved in the tissues of free-ranging hibernators or how the concentration of these PUFAs change in the natural diet over the summer. Therefore, we analyzed the fatty acid composition of the white adipose tissue (WAT) and plasma of free-ranging marmots (Marmota flaviventris) and of the plants in the marmots' diet, throughout the year. Marmots store PUFAs in WAT prior to hibernation but, over the winter, the percentage of the n-6 PUFA linoleic acid (18:2) increased in WAT, while the percentage of the n-3 PUFA α-linolenic acid (α-18:3) decreased in WAT. In the plasma, the concentration of nonesterified saturated and monounsaturated fatty acids was greater than that of nonesterified PUFAs, particularly in the spring. In the natural diet, the concentration of fatty acids varied significantly between plant species and between parts of the same plant. These data for free-ranging marmots corroborate previous results from studies on hibernators in the laboratory and, in addition, provide new information about the role of α-18:3 in hibernation.
Postnatal development of thermoregulation in the semiaquatic muskrat (Ondatra zibethicus)
Authors: MacArthur Robert A , Humphries Murray M
Published: April 2011

Developmental changes in thermoregulatory ability were followed in 1- to 34-d-old muskrats (Ondatra zibethicus) tested individually and in groups composed of 5 littermates. During their first 10-11 d of life, 20- to 60-g nestlings displayed limited thermogenic ability and could not maintain a stable body temperatures (Tb) during 2 h exposure to an air temperature (Ta) of 10 or 25°C. At 25°C, a Ta approximating nest temperatures in the field, nestlings were homeothermic at ca. 10-11 d of age, when they were fully furred, capable of limited swimming, and within 1-2 d of opening their eyes. The onset of thermoregulation occurred at a body mass (60 g) that was considerably less than predicted on the basis of adult body size. Huddling with littermates reduced the cooling of 20- to 60-g young at a Ta of 10°C, but did not advance the age (mass) at which they became effective homeotherms. Huddling by 20- to 60-g nestlings raised the mean Tb, leading to a substantive (64%) gain in the rate of oxygen consumption (Vo2). Conversely, in older nestlings that were close to or fully homeothermic, huddling with littermates consistently lowered Vo2, the greatest metabolic saving (38%) being realized by 17- to 21-d-old (100-140 g) young. We suggest that the rapid development of thermoregulation may be linked to the semiaquatic habit of muskrats, and that thermoregulatory behavior contributes importantly to the growth and morphological development of this prolific microtine rodent.
Influence of nest-site vegetation and predator community on the success of artificial songbird nests
Authors: Rangen Sheila A , Clark Robert G , Hobson Keith A
Published: April 2011

Vegetation characteristics are commonly invoked to explain differential nesting success, but few studies have identified how habitat attributes may be associated with specific predator groups responsible for nest losses. We measured vegetation characteristics at artificial songbird nests deployed on and above the ground in mixedwood forest in west-central Alberta, to discriminate characteristics of successful nests from those of nests destroyed by mice and voles, squirrels, and birds. Successful nests, and those depredated by mice and voles, tended to be on the ground and were well concealed by dense shrubs. Squirrels and birds usually raided aboveground nests at sites with few shrubs and high tree densities. These results suggest that nest visibility is a major factor influencing risk of predation, but the relative importance of concealment varies according to the types of predators and their behavior. The characteristics of nests from which eggs were removed, leaving no egg remains to identify predators, closely resembled those of nests visited by squirrels and birds. Our findings have implications for how individual songbird species cope with selection pressures imposed by nest predators associated with vegetation characteristics of birds' nest patches and, ultimately, how predators may shape the structure of avian communities.
Resource partitioning between coyotes and swift foxes: space, time, and diet
Authors: Kitchen Ann M , Gese Eric M , Schauster Edward R
Published: April 2011

In its current distribution and abundance, the swift fox (Vulpes velox) has been significantly reduced from its historic range. A possible cause is competition with, and predation by, coyotes (Canis latrans). We investigated the level of spatial, temporal, and dietary resource use overlap between swift foxes and coyotes at the Pinon Canyon Maneuver Site in southeastern Colorado. We captured and radio-tracked 73 foxes and 24 coyotes from April 1997 to August 1998. We collected 10 832 and 5350 locations of foxes and coyotes, respectively. Overall, home-range sizes of foxes and coyotes were 7.6 ± 0.5 (mean ± SE) and 19.8 ± 1.9 km2, respectively. A high degree of interspecies spatial overlap was apparent, with fox home ranges being overlapped by coyote home ranges by as much as 100% and coyote sign (tracks and scats) being evident in all swift fox home ranges. There was no evidence of temporal avoidance of coyotes in fox movement patterns. Coyotes traveled significantly farther than foxes during diurnal hours; foxes spent the majority of diurnal hours in or on top of dens. Coyotes and foxes showed a high index of overlap for dietary resources, although some dietary partitioning was apparent. Swift foxes specialized in small prey, such as insects and rodents, while coyotes used greater proportions of large prey, such as lagomorphs and ungulates. Interference competition was evident, with 48% (12/25) of fox mortalities identified as confirmed or probable coyote-caused deaths. In each case, death occurred outside either the fox's home range or the 85% isopleth of that range, indicating that coyotes are more likely to attack a fox successfully when it is a substantial distance from a den. We propose that swift foxes are able to coexist with coyotes, owing to year-round den use and a degree of dietary partitioning.
Effects of food quality on growth and survival of juvenile Columbian ground squirrels (Spermophilus columbianus)
Authors: Bennett Ronald P
Published: April 2011

Within a cohort of Columbian ground squirrels (Spermophilus columbianus), most deaths during hibernation usually occur in the first winter. Over-winter survivorship of juvenile Columbian ground squirrels is positively related to prehibernation body mass, which is primarily determined by the growth rate after emergence from natal burrows. This study examined how food quality influences growth and survival of juvenile Columbian ground squirrels. Growth and survival of juveniles in three colonies was measured, and biomass, composition (forb versus grass content), gross energy, crude protein, and digestibility of the summer forage supply were assessed. Differences in biomass and gross energy among colonies did not explain differences in growth and survival of resident ground squirrels. Growth and survival of juveniles was enhanced on sites with higher forb content in the forage supply. Forbs contained 15-40% more protein and were 30-50% more digestible than grasses, but protein levels on all sites were probably in excess of ground squirrels' requirements. This suggests that digestibility was limiting growth and was a more important food-quality indicator for juvenile ground squirrels than either energy or protein.
Spatial dynamics of a migratory wolf population in winter, south-central Ontario (1990-1995)
Authors: Cook S Joy , Norris D Ryan , Theberge John B
Published: April 2011

We examined the spatial distribution and movements of migratory wolves (Canis lupus lycaon) to a deer yard located adjacent to Algonquin Provincial Park, Ontario, during 5 winters from 1990 to 1995. Wolves from eastern and central Algonquin Provincial Park followed the annual migration of deer to yards located 13 km outside of the Park boundary. Spatial distributions were determined through mapping of telemetry locations and nearest neighbour analysis. We defined three spacing systems: consistent/high fidelity, clustered/moderate fidelity, and transitional/low fidelity. We found inconsistencies among packs in their adherence to these systems. Data indicate that areas of use changed quickly and tolerance levels among wolves in the deer yard were very high; alien wolves were recorded 163 times in close spatial and (or) temporal proximity. The social behaviour exhibited by this migratory population of wolves has never been recorded in a forested wolf-deer ecosystem. Factors that may contribute to this behavioural plasticity include food abundance, a high degree of genetic relatedness among wolf packs, and high rates of human-caused mortality.
Effects of removing duck-nest predators on nesting success of grassland songbirds
Authors: Dion Nancy , Hobson Keith A , Larivière Serge
Published: April 2011

During 1995 and 1996 we monitored natural and simulated nests of grassland songbirds following removal of duck-nest predators, primarily raccoons (Procyon lotor), striped skunks (Mephitis mephitis), and red foxes (Vulpes vulpes), in North Dakota, U.S.A. We were unable to detect an effect of predator removal on survival of natural (n = 153 nests) or simulated (n = 2264 nests) nests of grassland songbirds in either year. However, the assemblage of predators destroying simulated nests differed between removal and non-removal sites in 1995, when medium-sized carnivores and small mammals were the most important predators on non-removal sites, whereas ground squirrels were most important on removal sites. Our study indicates that grassland songbirds were not negatively affected, at least in the short term, by removal of duck nest predators. However, changes in the relative importance of predators on removal sites in 1995 suggest that smaller predators that were not targeted by removal efforts (i.e., ground squirrels) may have caused compensatory predation. Long-term studies are necessary to determine if the removal of duck-nest predators affects the numerical or functional response of predators at a lower trophic level, such as ground squirrels and other small mammals.
The growth hormone axis and cognition: empirical results and integrated theory derived from giant transgenic mice
Authors: Rollo C D , Ko C V , Tyerman JG A , Kajiura L J
Published: April 2011

Sleep is required for the consolidation of memory for complex tasks, and elements of the growth-hormone (GH) axis may regulate sleep. The GH axis also up-regulates protein synthesis, which is required for memory consolidation. Transgenic rat GH mice (TRGHM) express plasma GH at levels 100-300 times normal and sleep 3.4 h longer (30%) than their normal siblings. Consequently, we hypothesized that they might show superior ability to learn a complex task (8-choice radial maze); 47% of the TRGHM learned the task before any normal mice. All 17 TRGHM learned the task, but 33% of the 18 normal mice learned little. TRGHM learned the task significantly faster than normal mice (p < 0.05) and made half as many errors in doing so, even when the normal nonlearners were excluded from the analysis. Whereas normal mice expressed a linear learning curve, TRGHM showed exponentially declining error rates. The contribution of the GH axis to cognition is conspicuously sparse in literature syntheses of knowledge concerning neuroendocrine mechanisms of learning and memory. This paper synthesizes the crucial role of major components of the GH axis in brain functioning into a holistic framework, integrating learning, sleep, free radicals, aging, and neurodegenerative diseases. TRGHM show both enhanced learning in youth and accelerated aging. Thus, they may provide a powerful new probe for use in gaining an understanding of aspects of central nervous system functioning, which is highly relevant to human health.
Sensitivity of amphibian embryos, tadpoles, and larvae to enhanced UV-B radiation in natural pond conditions
Authors: Crump Douglas , Berrill Michael , Coulson Donna , Lean David , McGillivray Lise , Smith Alex
Published: April 2011

Temperate zone amphibians are exposed to the maximum change in UV-B radiation influx during early stages of their development. Embryos and tadpoles of six anurans, Bufo americanus, Rana sylvatica, Rana pipiens, Rana clamitans, Rana catesbeiana, and Hyla versicolor, and embryos and larvae of two salamanders, Ambystoma maculatum (the yellow-spotted salamander) and Ambystoma laterale (the blue-spotted salamander), were exposed to different UV-B radiation regimes in containers (12 cm in diameter and 4.5 cm deep) with Nitex screening (1 mm) on the sides to permit natural exchange with pond water. The containers were secured to a floating structure in a small natural pond in south-central Ontario, where most of the species tested lived and successfully recruited offspring. Three exposure conditions were evaluated: (i) natural incident light, (ii) incident light with the UV-B radiation filtered out, and (iii) incident light with the UV-B radiation enhanced by UV-B lamps. Embryos of all species hatched successfully under enhanced and incident UV-B radiation conditions. However, salamander larvae and anuran tadpoles were sensitive to enhanced UV-B radiation conditions and a differential sensitivity was observed based on developmental stage. When 2 weeks old, anuran tadpoles showed greater sensitivity than when newly hatched. Incident levels of UV-B radiation had no significant effect on tadpoles or larvae. Because of the tolerance of the embryos and the very rapid attenuation of UV-B radiation in the water of small ponds (high in dissolved organic carbon (DOC)), little direct damage is likely to occur during the aquatic stages of these amphibians.
Greater predation by Double-crested Cormorants on cutthroat versus rainbow trout fingerlings stocked in a Wyoming river
Authors: Lovvorn James R , Yule Daniel , Derby Clayton E
Published: April 2011

We studied the relative vulnerability of Yellowstone cutthroat trout (Oncorhynchus clarki bouvieri) versus rainbow trout (Oncorhynchus mykiss) stocked as fingerlings in the North Platte River, Wyoming, to Double-crested Cormorant (Phalacrocorax auritus) predation. Cutthroat fingerlings decreased as a fraction of the population from stocking in late June to electrofishing surveys in the following October and March. In contrast, the fraction of cutthroat fingerlings among tagged fingerlings eaten by cormorants collected on the river was significantly greater than that in the population when originally stocked. More limited data from pellets regurgitated by adult cormorants at a nearby colony and in American White Pelicans (Pelecanus erythrorhynchos) collected on the river showed the same trend toward greater percentages of cutthroat trout being consumed than were present among trout stocked. There were no differences in cormorant predation rates on the Eagle Lake strain of rainbow trout reared under shaded versus partially shaded conditions, or between Auburn and Bar BC strains of Snake River (Yellowstone) cutthroat trout. On the North Platte River, cutthroat trout fingerlings were more susceptible to cormorant predation than rainbow trout of similar size that were stocked simultaneously.
Effects of forest fragmentation on behaviour patterns in the eastern chipmunk (Tamias striatus)
Authors: Mahan Carolyn G , Yahner Richard H
Published: April 2011

We examined behaviour in adult eastern chipmunks (Tamias striatus) from 1992 to 1995 in a landscape altered by forest clear-cutting in central Pennsylvania, U.S.A. Our objective was to compare behaviour patterns in chipmunk populations occupying mature continuous forest versus mature forested corridors (100 m wide) surrounded by clearcuts. Chipmunks spent a significantly greater proportion of their time pausing in the forested-corridor habitat than in the continuous-forest habitat. In addition, chipmunks spent less time locomoting and foraging in the forested-corridor habitat than in the continuous forest. We attributed differences in behaviour patterns between chipmunks in the two forest types primarily to the influence of forest fragmentation on the risk of predation and to the availability of food resources.
Nutritive quality of forage plants for greater snow goose goslings: when is it advantageous to feed on grazed plants?
Authors: Piedboeuf Nathalie , Gauthier Gilles
Published: April 2011

Foraging herbivores often face a choice: move to ungrazed sites, where the biomass is high, or use grazed sites, where the biomass is lower but the quality of the regrown plants is often higher. Foraging strategies should therefore depend on the difference in biomass between grazed and ungrazed sites and the food quality in the two types of site, both variables that are likely to vary seasonally. We compared the nutritive quality (in terms of metabolisability of food, nitrogen, and energy, and rate of food intake) of grazed and ungrazed sites for early- and late-hatched greater snow goose (Chen caerulescens atlantica) goslings throughout the summer. We conducted field experiments with captive goslings feeding on grasses and sedges in the Arctic. Plant quality declined seasonally (nitrogen concentration decreased and fibre content increased) but, contrary to our initial expectations, grazed plants were not higher in quality or metabolisability than ungrazed ones. This was possibly a consequence of poor regrowth after grazing because of drought conditions that prevailed during this study. Consequently, rates of intake of food, metabolisable nitrogen, and metabolisable energy were always higher at ungrazed than at grazed sites. Rates of intake of metabolisable nitrogen and energy declined seasonally for both grazed and ungrazed plants, which suggests that goslings were not able to compensate for the seasonal decline in food quality by increasing their rate of food intake. No difference was found between early- and late-hatched goslings in food metabolisability, and both groups were exposed to the same seasonal effects. Weak regrowth after grazing leads to poor feeding conditions for goslings. Under these circumstances, ungrazed sites are of higher nutritive value for goslings than grazed sites.
Behavioral responses of coyotes to wolf recolonization in northwestern Montana
Authors: Arjo Wendy M , Pletscher Daniel H
Published: April 2011

Recent recolonization of northwestern Montana by wolves (Canis lupus) provided an opportunity to examine behavioral responses of coyotes (Canis latrans) to a reestablished wolf population. Coyote and wolf annual home ranges overlapped extensively; however, seasonal overlap was not as pronounced. Most seasonal coyote home ranges were located between wolf packs or along the edge of wolf territories, but wolves and coyotes did not use the seasonal overlap area differently than expected. Most of the coyotes maintained random separation distances from wolves, though three coyotes were closer to wolves than expected. No difference in summer activity was found between the canids; however, temporal partitioning occurred during the winter, which may have allowed the increase in home-range overlap observed during the winter. Additionally, temporal partitioning occurred through differential arrangement of canid home ranges (i.e., wolf home ranges were smaller in summer) and reduced overlap of seasonal home ranges. Coyotes were usually singletons and some pairs, and before wolf colonization they fed on lagomorphs and plants. After wolf colonization, coyotes tended to be in pairs and small packs and they relied on ungulates. Although we documented wolves killing coyotes, coyotes are coexisting with wolves through spatial and temporal separation and behavioral changes.
Senescence in field crickets (Orthoptera; Gryllidae): examining the effects of sex and a sex-biased parasitoid
Authors: Gray David A , Cade William H
Published: April 2011

The evolutionary theory of aging proposes that senescence is related to decreased selection against deleterious mutations acting late in life. Senescence, i.e., an increase in intrinsic mortality with age, should reflect levels of extrinsic mortality early in life. We tested these predictions using two species of field cricket, Gryllus integer and Gryllus pennsylvanicus. Gryllus integer males are host to a sex-biased parasitoid fly, which orients to the male calling song. As a result, males have reduced life expectancy compared with females in the field. In contrast, G. pennsylvanicus males and females appear to have similar life expectancies in the wild. Thus, we predicted that there would be a significant species × sex interaction, with G. integer males having the shortest life-span. In two replicates, we found that males of both species died at a significantly younger age than females. However, no evidence of a species × sex interaction was found: in the first replicate, G. integer males died earliest, in the second replicate, G. pennsylvanicus males died earliest.
Differences in tolerance to and recovery from zebra mussel (Dreissena polymorpha) fouling by Elliptio complanata and Lampsilis radiata
Authors: Hallac David E , Marsden J Ellen
Published: April 2011

Zebra mussels (Dreissena polymorpha) in Lake Champlain have colonized the shells of many native unionids, causing declines in their abundance. Periodically cleaning zebra mussels from unionids may be an effective conservation technique, if unionids can recover from the stress induced by zebra mussels. Efforts will need to target species that are most vulnerable to fouling and subsequent energetic losses. We used glycogen as a biochemical indicator of energetic stores to assess species-specific differences in tolerance to zebra mussels. There was no evidence that glycogen levels decreased as dreissenid/unionid mass ratios increased in Elliptio complanata. However, dreissenid/unionid mass ratios as low as 0.25 in Lampsilis radiata were correlated with a significant decline in glycogen content. The ability of these species to recover glycogen after zebra mussel removal and replacement in situ was also evaluated. Mussels were cleaned of zebra mussels and replaced in situ. After 10 weeks, cleaned, heavily fouled, and never-fouled (control) mussels were collected. Glycogen levels in fouled mussels were lower than in the control mussels, while glycogen levels in cleaned mussels did not differ from the control mussels. Results suggest that heavily fouled E. complanata and L. radiata can recover glycogen levels if cleaned of zebra mussels and that cleaning may be a viable option for unionid conservation.
The importance of microhabitat factors and habitat stability to the threatened Louisiana pearl shell, Margaritifera hembeli (Conrad)
Authors: Johnson Paul D , Brown Kenneth M
Published: April 2011

Margaritifera hembeli, the Louisiana pearl shell, is a threatened mussel with a distribution limited to the headwaters of three tributaries of the Red River in central Louisiana, U.S.A. We assessed the role that several habitat characters played in determining its abundance and distribution. Pearl shell mussels were more common in second-order streams with elevated conductivity (approximately 0.04 mS/cm) and water hardness (8 mg/L). A discriminant analysis indicated that mussel density was related to water depth, substrate size, substrate compaction, and water velocity. Mussels were rare in deep, stagnant pools with silt-covered bottoms, and were more common in shallow, wide areas of streams with higher current velocities and in sediments with larger particle sizes. Mussel beds were also more likely to occur in sections of the stream where the substrate was more stable through time. These habitat associations may occur because individuals that recruit into, or later select, more stable microhabitats, have an advantage owing to the relatively long life cycle of this mussel. We suggest that the measurement of microhabitat characteristics can be important when evaluating habitat preferences and management plans for endangered mussel species in headwater streams.