bluuebunny/crossref_metadata_2025 huggingface dataset:
The importance of prey distribution in habitat use by arctic foxes (Alopex lagopus)
Authors: Jepsen Jane U , Eide Nina E , Prestrud Pål , Jacobsen Linn B
Published: November 2002

The use of habitat by reproducing arctic foxes (Alopex lagopus) in relation to prey distribution was examined on the Svalbard archipelago in the Norwegian High Arctic during 19871988 and 19972000 by means of VHF telemetry. The distribution and abundance of the main prey species of foxes was registered in 4 separate periods during summer. The availability of 9 habitat types was estimated on the basis of a classification of a Landsat-5 TM scene. Three resource areas that differed with regard to distribution and availability of prey, vegetation, and terrain were identified within the study area: (1) inland areas with no geese, (2) inland areas with geese present, and (3) coastal areas with bird cliffs. The use of resources by foxes was calculated in the 4 separate periods, as was the average speed of movement (m/h) of foxes and the distance between fox locations and their natal dens. Resource-selection functions (RSFs) calculated for individual animals showed that resource use was nonrandom and similar for foxes that lived within the same resource area. In inland areas in which resource availability was low but fairly stable (area 1), RSFs were simple and in some cases of low significance compared with a no-selection model. In inland areas with highly dynamic resources (area 2), RSFs were complex and resource use differed significantly between periods. In coastal areas (area 3), where resources were plentiful, highly concentrated, and stable, RSFs were of intermediate complexity and resource use differed less between periods.
Mane variation in African lions and its social correlates
Authors: Kays Roland W , Patterson Bruce D
Published: November 2002

Manes are generally thought to characterize all adult male lions (Panthera leo). Here we document a population of lions in Tsavo National Park, Kenya, that is largely maneless and describe aspects of their social organization. Because Tsavo's arid landscape supports sparse prey populations, we expected that surveys of lions there would document small social groups. We hypothesized that Tsavo lions would consequently experience reduced sexual selection pressures for mane development. Adult males from Tsavo typically have sparse blond hair forming a dorsal crest, beard, chest tufts, and (or) sideburns, but lack the large flowing manes reported from other lion populations. No fully maned lions were seen. Maneless males in Tsavo appear to be well integrated into pride life, and were observed copulating, hunting, and otherwise interacting with groups of females, playing with dependent cubs, and advertising territories with scent markings and roars. Only one adult male was observed in each of five prides, which differs surprisingly from the coalitions of 24 pride males noted in other lion groups. However, female group size was large (mean 7.4) and comparable with what has been documented in the Serengeti and elsewhere, refuting our "group size  mane size" hypothesis. Future research should focus on the effect of Tsavo's physical and physiological effects on mane condition, and the possible correlation of male hormone levels with both manelessness and small male-group size.
Cougar predation and population growth of sympatric mule deer and white-tailed deer
Authors: Robinson Hugh S , Wielgus Robert B , Gwilliam John C
Published: November 2002

Mule deer (Odocoileus hemionus) populations throughout the west appear to be declining, whereas white-tailed deer (Odocoileus virginianus) populations are increasing. We compared abundance, number of fetuses per female (maternity rate), recruitment, and cause-specific adult ([Formula: see text]1 year old) mortality rate for sympatric mule deer and white-tailed deer in south-central British Columbia to assess population growth for each species. White-tailed deer were three times more abundant (908 ± 152) than mule deer (336 ± 122) (mean ± 1 SE). Fetal rates of white-tailed deer (1.83) were similar to those of mule deer (1.78). There was no statistically significant difference in recruitment of white-tailed deer (56 fawns : 100 does) and mule deer (38 fawns : 100 does). The annual survival rate for adult white-tailed deer (SWT = 0.81) was significantly higher than that for mule deer (SMD = 0.72). The main cause of mortality in both populations was cougar predation. The lower mule deer survival rate could be directly linked to a higher predation rate (0.17) than for white-tailed deer (0.09). The finite growth rate (λ) was 0.88 for mule deer and 1.02 for white-tailed deer. The disparate survival and predation rates are consistent with the apparent-competition hypothesis.
Fractal dimension of African mole-rat burrows
Authors: Le Comber Steven C , Spinks Andrew C , Bennett Nigel C , Jarvis Jennifer UM , Faulkes Chris G
Published: November 2002

The African mole-rats (Bathyergidae) are a model taxon on which to test evolutionary theories of the origin and maintenance of mammalian social behaviour, since species within the family range in social complexity from solitary to eusocial. The aridity food-distribution hypothesis suggests that sociality within the Bathyergidae has evolved as a consequence of habitat aridity, and the subsequent pattern of geophyte abundance and distribution. In more arid environments, because of the patchiness of this food resource, and the fact that burrowing is only possible during brief periods where rainfall has softened the soil, the risk of unsuccessful foraging is high. This risk may decrease when large numbers of animals are involved in cooperative searching. We examined 25 burrows of seven species within the Bathyergidae and used a simple box-counting method to determine their fractal dimension, which we propose as a measure of burrow architecture that allows explicit testing of differences in African mole-rat burrows within the theoretical framework of the aridity food-distribution hypothesis. We investigate the effect of habitat type and colony size on this parameter, and conclude that habitat type is reflected in burrow architecture in the common mole-rat, Cryptomys hottentotus hottentotus. We also found evidence that the burrows of species with larger maximum group size explore the surrounding area more thoroughly. The results support the contention that larger group size offers adaptive benefits in terms of how thoroughly the surrounding area is explored, and is not simply a consequence of the increased costs of dispersal and colonization in arid areas.
Estimating low-density snowshoe hare populations using fecal pellet counts
Authors: Murray Dennis L , Roth James D , Ellsworth Ethan , Wirsing Aaron J , Steury Todd D
Published: November 2002

Snowshoe hare (Lepus americanus) populations found at high densities can be estimated using fecal pellet densities on rectangular plots, but this method has yet to be evaluated for low-density populations. We further tested the use of fecal pellet plots for estimating hare populations by correlating pellet densities with estimated hare numbers on 12 intensive study areas in Idaho; pellet counts from extensive transects (n = 615) across northern Idaho enabled rectangular plots (0.155 m2) to be compared with paired small (0.155 m2) and large (1 m2) circular plots (metre-circle plots). Metre-circle plots had higher pellet prevalence, lower sample variance, and lower estimates of pellet density than the other plot types. Transects comprising circular plots required less establishment time, and observer training reduced the pellet-count bias attributable to plot shape. The number of hares occupying intensive study sites was correlated with pellet density on all plot types, but rectangular plots provided a slightly closer linear fit to hare numbers than did metre-circle plots. The relationship between pellet density and hare number may have been curvilinear rather than linear, but linear and nonlinear models provided similar numerical estimates over much of the range of pellet densities. These results indicate that pellet counts are a robust estimator of hare numbers in low-density populations, and that metre-circle plots represent an improvement over standard rectangular plots in terms of unbiased pellet counts, sacrificing little predictive power. We recommend using pellet counts in metre-circle plots for estimating populations of snowshoe hares in their southern distribution.
Factors affecting wild boar (Sus scrofa) occurrence in highly fragmented Mediterranean landscapes
Authors: Virgós Emilio
Published: November 2002

This paper is an analysis of the effects of forest fragmentation on wild boar (Sus scrofa) occurrence in coarse-grained fragmented landscapes (<20% forestscrubland cover on a landscape scale; N = 140 forest fragments, four regions) in central Spain. Occurrence was examined in relation to forest size, isolation, habitat quality, and region. Wild boar occurrence was mainly explained by the location of the forest fragments on the northern or southern plateau. Wild boars were more abundant on the northern plateau than on the southern plateau. In addition, wild boars are more frequent in large forest fragments adjacent to other large forests near mountains or riparian woodlands. The percent presence of wild boars in fragments varied among the four regions sampled (regional effect). Although wild boars occurred more frequently in large than in small forests, this pattern was less pronounced than that found in badgers (Meles meles), roe deer (Capreolus capreolus), and stone martens (Martes foina) and similar to that found in red foxes (Vulpes vulpes). The spatial distribution of wild boars may be affected by forest fragmentation despite their typical generalist life-history traits and potential use of agricultural areas as food habitats. These results support the idea that landscape pattern (degree of fragmentation and grain pattern) may be a determinant of species' abundance and distribution in fragmented landscapes.
Assessment of sources of variance and patterns of overlap in microchiropteran wing morphology in southeast Queensland, Australia
Authors: Rhodes Martin P
Published: November 2002

In ecomorphological relationships, ecological similarities or overlap between species may occur with morphological similarity or overlap. Determination of morphological distinctness is thus important when relating morphology with ecology. This is the first of a series of papers investigating the ecomorphology of Microchiroptera in southeast Queensland, Australia, and in it I describe means and ranges of measurements and distinctness of wing morphology. In 21 species from this region, species means for aspect ratio (relative wing width) ranged from 4.98 to 8.25, while wing loading (mass by wing area) ranged from 4.32 to 15.9 N/m2. For these variables, each species' range (minimummaximum) overlaps that of at least one other species, with greater overlap at lower values. Morphological overlap was frequent, owing to a consistently wide range of wing dimensions within species, with greater overlap at low aspect ratios and wing loadings where species were more closely packed. For all variables, the variance arising from the method of measurement (wing extend and trace) was less than intraspecific variance, but in many cases was similar to interspecific overlap. A proportion of the range and overlap in wing-morphology variables is attributable to measurement variance. The variance in aspect ratio was lower than in wing loading at species, genus, family, and region levels. Phylogenetic constraint on aspect ratio appears to be greater than on wing loading, particularly at the family level. At family and genus levels, aspect ratio varied less than wing loading. No overlap in aspect ratio occurred at family level. I group species into morphologically distinct units and provide predictions of the flight behaviour of these.
The timing of adult sockeye salmon migration into fresh water: adaptations by populations to prevailing thermal regimes
Authors: Hodgson Sayre , Quinn Thomas P
Published: November 2002

Anadromous fishes migrate to sea, apparently to take advantage of growing conditions, and return to fresh water to spawn. Despite favorable growing conditions at sea in summer, some populations leave the ocean in spring, many months prior to spawning. We hypothesized that this premature migration is a consequence of the fish having to avoid stressful summer temperatures in order to access certain suitable areas for spawning in the fall. We tested this idea in sockeye salmon, Oncorhynchus nerka, by compiling data on the timing of migration and spawning and the freshwater temperature regime along the migration route in populations throughout the species' North American range. The timing of migration varied among populations and was primarily related to temperature regime during migration and the timing of spawning. When temperatures were moderate (<19°C), sockeye salmon tended to migrate to the vicinity of the spawning grounds about 1 month prior to spawning, regardless of the length of the freshwater migration. However, populations on whose migration route the average temperature exceeded 19°C displayed two basic patterns. Some populations entered fresh water prior to the warmest period, months before spawning, whereas others migrated after the period of highest temperatures had occurred.
Phylogeny of the species of the superfamily Echeneoidea (Perciformes: Carangoidei: Echeneidae, Rachycentridae, and Coryphaenidae), with an interpretation of echeneid hitchhiking behaviour
Authors: O'Toole Bruce
Published: November 2002

A phylogenetic analysis, based on 138 putatively informative characters, of the 11 species of the superfamily Echeneoidea (Echeneidae, Rachycentridae, and Coryphaenidae) resulted in a single most parsimonious tree. This tree strongly supports the monophyly of the superfamily with the following relationships: Coryphaenidae + (Rachycentridae + (Phtheirichthys lineatus + ((Echeneis naucrates + Echeneis neucratoides) + (Remora brachyptera + (Remora remora + (Remora australis + (Remora osteochir + Remora albescens))))))). One of the traditional subfamilies, Echeneiinae, and one of the traditional genera, Remora, were both found to be paraphyletic. A new classification of the family based on natural groupings eliminated the subfamilial designations and subsumed the genus Remorina under the genus Remora, rendering it monophyletic. An examination of the behavioural data resulted in the hypothesis of a gradual step-by-step development of "hitchhiking" behaviour from general schooling behaviour (outgroups) to attaching to a select few types of hosts in the pelagic environment (as exhibited by R. osteochir).
A short spring before a long jump: the ecological challenge to the steppe tortoise (Testudo horsfieldi)
Authors: Lagarde Frédéric , Bonnet Xavier , Nagy Ken , Henen Brian , Corbin Johanna , Naulleau Guy
Published: November 2002

The steppe tortoise (Testudo horsfieldi) is probably the most widespread and abundant of all living terrestrial tortoises, but paradoxically, this chelonian as been studied only superficially. Steppe tortoise populations are declining rapidly as a result of massive harvesting for the pet trade and extensive disruption of their habitat by intensive agriculture. Thus, it is urgent to acquire accurate information on major life-history traits. Our 5-year field study at the Djeiron Ecocenter in the Republic of Uzbekistan indicates that steppe tortoises usually remain buried in one place for over 9 months, which helps them cope with the extreme environmental conditions that occur in summer, fall, and winter. After emerging in late winter, steppe tortoises have less than 3 months in spring to forage to obtain the fuel needed for growth and reproduction, and replenish the body reserves necessary for the subsequent 9 months of total starvation. The mating period occurred between the end of March and mid-April and the egg-laying period from the end of April to mid-June. Using radio-tracking and focal sampling, we measured the time devoted to different activities by males and females. During the mating period, males allocated a large proportion of their daily activity to sexual behaviours, whereas females' sexual activity tended to be cryptic. However, males devoted less time to feeding and resting than did females. During the postmating period, both males and females spent much time foraging. The strong sexual divergences indicate that each sex copes differently with the extreme continental climate. The seasonal and interannual changes in body mass indicate complex interactions between climatic conditions, activity budget, and body reserves.
The relationship between song performance and male quality in snow buntings (Plectrophenax nivalis)
Authors: Hofstad E , Espmark Y , Moksnes A , Haugan T , Ingebrigtsen M
Published: November 2002

Attracting females is considered to be one of the main functions of bird song. Both the rate and complexity of male song are assumed to be reliable, quality-related cues that may be used by the female when choosing a mate. In this study of the snow bunting (Plectrophenax nivalis) on Svalbard, both these song parameters were considered as possible quality indicators for the female. Owing to the challenging environmental conditions in the High Arctic, a high degree of male effort is probably necessary to successfully raise the clutch. Male song rate and song complexity were therefore predicted to be correlated with early mating, male feeding rate during the female's incubation, male feeding rate during the nestling stage, and the number of fledglings produced. Although song length tended to be positively associated with the number of fledged young, the different song complexity parameters did not show any clear association with the onset of breeding, the male's food provisioning rate, and the number of fledglings. However, the song rate was significantly correlated with early mating, and there was a positive, although not significant, correlation between song rate and the rate at which older chicks were fed by the male. These results are consistent with the hypothesis that females might use male song rate to assess male quality and ability to participate in raising chicks.
Climate change and caribou: effects of summer weather on forage
Authors: Lenart Elizabeth A , Bowyer R Terry , Hoef Jay Ver , Ruess Roger W
Published: November 2002

In 1989, the Chisana caribou (Rangifer tarandus) herd in the northern Wrangell Mountains, Alaska, U.S.A., declined substantially in population size and productivity. Grasses, sedges, forbs, and willows (Salix spp.) are critical components of the diet of caribou in spring and summer, and the abundance and quality of forage are influenced by climate. To evaluate effects of climatic variation on caribou forage we conducted a field experiment in subarctic tundra where light, air temperature, and precipitation were manipulated. We used a plastic tarpaulin to increase air temperature and decrease precipitation. We also decreased light intensity with a shade cloth and increased precipitation by adding water to determine climatic effects on nutrient content and biomass of forage for caribou during the summers of 1994 and 1995. The most notable treatment effect on aboveground biomass was that shading resulted in higher nitrogen concentrations in all plant growth forms. In addition, shading consistently reduced biomass in forbs during mid and late season. Water treatment increased total plant biomass in the greenhouse plots during midseason in 1994 and in late spring in 1995. Water treatment also increased late-season biomass in control plots during 1994 but had no effect on biomass in shaded plots in either 1994 or 1995. A decline in nitrogen concentration in plants occurred throughout summer, a pattern that was not evident in in vitro dry matter digestibility. Climate variation and subsequent effects on forage plants have the potential to influence the population dynamics of caribou through effects on their food supply.
Sequence variations in the mitochondrial DNA control region and their implications for the phylogeny of the Cypriniformes
Authors: Liu Huanzhang , Tzeng Chyng-Shyan , Teng Hui-Yu
Published: November 2002

The mitochondrial DNA control region of six cobitids and two catostomids was sequenced and compared with sequences of other cypriniforms to study their sequence variations. The extended termination associated sequence (ETAS) domain, central domain, and conserved sequence block (CSB) domain were partitioned and the ETAS sequence, CSB-D, CSB-E, ECSB-F, CSB1, CSB2, and CSB3 were identified. It is suggested that the "hairpin" TACAT-ATGTA is the key sequence of ETAS and GACATA is the symbol of CSB1. Phylogenetic analysis based on the CSB domain showed that all cyprinids evolved as one monophyletic group, while the non-cyprinid Cypriniformes could be another monophyly that is in accordance with the hypothesis proposed by Siebert. Further analysis of the phylogeny of the Cobitoidei was also conducted and it is tentatively suggested that their relationships are Catostomidae + (Gyrinocheilidae + (Botiinae + (Homalopteridae + (Cobitinae + Nemacheilinae)))).
Refuge use in a killifish: influence of body size and nutritional state
Authors: Dowling Lisa M , Godin Jean-Guy J
Published: November 2002

Refuge use by animals provides greater safety from predation. A refuging animal continuously must decide whether to stay in the refuge or to emerge into open habitat. This decision may depend on its energetic state and vulnerability to predation, both of which can vary with individual body size. We experimentally tested the concurrent effects of body size and nutritional (hunger) state on refuge use in the banded killifish (Fundulus diaphanus). Individual killifish were "attacked" in an open laboratory habitat (containing food) by either a trout predator model or a control model that did not resemble a trout. Frightened fish typically fled into a foodless refuge nearby. The amount of time that killifish spent in the refuge before emerging increased significantly with body length, but was not affected by their current nutritional state or the threatening stimulus (type of model). Smaller killifish were thus more risk-prone than larger conspecifics irrespective of their current nutritional state. Such size-mediated risk-taking behaviour has important consequences for individual fitness and implications for population and community composition and dynamics in nature.
Sexual dimorphism in trophic morphology and feeding behavior of wolf spiders (Araneae: Lycosidae) as a result of differences in reproductive roles
Authors: Walker Sean E , Rypstra Ann L
Published: November 2002

Sexual dimorphism in animals is thought to be a result of differences between the sexes in the relationship between reproductive success and a trait, or a result of intersexual niche divergence. Intersexual niche divergence occurs as a result of competition between the sexes and is generally inferred from sexual dimorphism in morphological features associated with feeding. However, differences between the sexes in trophic morphology can be a result of either intersexual niche divergence or differences in the relationship between foraging success and reproduction between the sexes. In this study we examined sex differences in the trophic morphology of six wolf spider species and in the feeding behavior of two of these species. Females were larger than males in almost all characteristics even after differences in body size were accounted for, and killed and consumed more prey. We found little evidence of intersexual niche divergence based on differences in the relative prey sizes preferred by males and females of two species. Our data suggest that differences in the reproductive roles of males and females have resulted in foraging success being more important for female fitness than for male fitness and that differences in reproductive roles can result in sexual dimorphism.
Repeatability of condition indices in captive greenfinches (Carduelis chloris)
Authors: Hõrak Peeter , Saks Lauri , Ots Indrek , Kollist Hannes
Published: November 2002

Animal ecologists often encounter a major problem when they wish to use individual condition indices measured at some point in an animal's life cycle as a reference to some persistent component of individual phenotypic quality. It is therefore important to know the time period for which a certain measurement is valid. We measured both short-term (48 days) and long-term (over 4 months) repeatabilities of 17 condition indices in captive greenfinches (Carduelis chloris). All studied traits (leukocyte counts and serum protein concentration and profile, serum triglyceride concentrations, body mass, basal metabolic rate (BMR), and spontaneous locomotory activity) revealed significant and moderate to high repeatabilities within the 4- and 8-day periods. Hence, all these traits are suitable for detecting short-term experimental effects upon an individual's physiology. Leukocyte variables (total leukocyte count, heterophil and lymphocyte hemoconcentrations, and heterophil/lymphocyte ratio), BMR, and body mass revealed significant individual consistency within the 4-month period. These variables thus reflect relatively long-term components of individual condition and may appear suitable for exploring the relationships between individual phenotypic quality, life-history traits, and signal traits.
The effects of selective logging on nest-site selection and productivity of hooded warblers (Wilsonia citrina) in Canada
Authors: Whittam Rebecca M , McCracken Jon D , Francis Charles M , Gartshore Mary E
Published: November 2002

We examined nest-site selection by hooded warblers (Wilsonia citrina) in two forests differing in composition (extensive pine plantation versus largely deciduous) and management (recent selective logging versus minimal logging). We measured habitat at 52 nests and 66 controls in one forest and 57 nests and 41 controls in the second. Nests had denser ground vegetation, fewer tree stems, less basal area due to small trees and greater basal area due to large trees than controls in both forests. In the managed forest with extensive pine plantations, hooded warblers were in coniferous and logged stands more often than expected by chance, nests had more stumps and greater canopy height than controls, and 91% (52/57) of all nests were found in gaps, 84% of which were created by harvest. Gap age was 6.2 ± 0.9 years (mean ± SE) in 1999, and 7.6 ± 0.6 years in 2000. In the managed forest, 52% of 24 nests were parasitized in 1999 and 39% of 33 nests were parasitized in 2000. The daily survival rate was 0.936 ± 0.019 in 1999 and 0.944 ± 0.014 in 2000. Successful nests did not differ from unsuccessful nests in any habitat variable. To benefit hooded warblers, forest managers should mimic natural gap creation by using selective logging to create gaps no larger than 0.05 ha, and should leave a residual basal area of mature trees (>38 cm diameter at breast height) of at least 12 m2/ha.
Food-chemical discrimination and correlated evolution between plant diet and plant-chemical discrimination in lacertiform lizards
Authors: Cooper Jr., William E , Caldwell Janalee P , Vitt Laurie J , Pérez-Mellado Valentín , Baird Troy A
Published: November 2002

Lizards use chemical cues to locate and identify prey and plant food, assess the nutritional quality of food, and detect plant toxins. Among insectivorous lizards, all actively foraging species studied respond strongly to prey chemicals sampled lingually, but ambush foragers do not. Much recent research has been devoted to assessing differential responses to food and nonfood chemicals (i.e., food-chemical discrimination) by omnivorous and herbivorous species and determining whether correlated evolution has occurred between plant diet and plant-chemical discrimination. We conducted experimental studies of food-chemical discrimination by two species of teiid lizards, the omnivorous Cnemidophorus murinus and the actively foraging insectivorous Ameiva ameiva. The omnivore distinguished both prey and plant chemicals from control substances. The insectivore exhibited prey-chemical, but not plant-chemical, discrimination, as indicated by tongue-flicking and biting. A comparative analysis using concentrated-changes tests showed that correlated evolution has occurred between plant consumption and plant-chemical discrimination in a major lizard taxon, Lacertiformes. These results extend and strengthen previous findings of similar correlated evolution to a new group and add to a growing database indicating that omnivorous lizards use chemical cues to assess both prey and plant foods.
Diving behaviour of narwhals (Monodon monoceros) at two coastal localities in the Canadian High Arctic
Authors: Laidre Kristin L , Heide-Jørgensen Mads Peter , Dietz Rune
Published: November 2002

In August 1999 and 2000, four suction-cup-attached timedepth recorders (TDRs) were deployed and retrieved from narwhals (Monodon monoceros) in Tremblay Sound, Baffin Island, and Creswell Bay, Somerset Island, Nunavut, Canada. The TDRs remained on the whales for between 12 and 33 h and collected 64.5 h of dive data. Mean dive depths ranged from 20.8 m (SD = 14.8 m) to 50.8 m (SD = 43.8 m) and mean dive durations ranged from 3.4 min (SD = 1.6 min) to 4.9 min (SD = 4.5 min). There appeared to be individual differences in dive parameters both within a region and between regions. Three of the whales made short, shallow dives, while another whale made dives twice as deep and twice as long. One whale had maximum dive durations (>20 min) that exceeded predicted aerobic dive limits for narwhals. There was a strong relationship between maximum dive depth and duration for all whales (p < 0.0001). Narwhals spent between 30.3 and 52.9% of their time at depths <5 m and the range of correction factors for availability bias was 1.93.3. Satellite-linked TDRs were simultaneously deployed on the whales at both localities. Dive data collected using the two methods were compared and good agreement between the methods was obtained.
Barking up the wrong tree: climbing performance of rat snakes and its implications for depredation of avian nests
Authors: Mullin Stephen J , Cooper Robert J
Published: November 2002

Nest depredation is the leading cause of nest failure in NeotropicalNearctic migratory birds, which are of interest because of their declining populations. In a recent study in a bottomland hardwood forest, Acadian Flycatchers (Empidonax virescens) experienced higher nest success in Nuttall oak (Quercus nuttallii), a tree species with relatively smooth bark at maturity. To determine if variation in bark-surface irregularities may influence the ability of a predator species to access the contents of avian nests, we examined the climbing abilities of rat snakes (Elaphe obsoleta) on trees having three different bark types. None of the subjects was able to ascend large Nuttall oaks in the absence of vines; with vines present, subjects still required more time to climb Nuttall oaks than to climb other species. A few of the subjects successfully climbed smaller Nuttall oaks lacking vines, but ascent time was longer and climbing behavior was modified from that observed in the other trials. Our results indicate that the likelihood of nest predation by rat snakes decreases in this forest when birds nest in trees with smooth bark and without vines. Investigators need to consider differences among nest substrates that are important to both the prey and the predator.
Experimental demonstration of a behavioural modification in a cyprinid fish, Rutilus rutilus (L.), induced by a parasite, Ligula intestinalis (L.)
Authors: Loot Géraldine , Aulagnier Stéphane , Lek Sovan , Thomas Frédéric , Guégan Jean-François
Published: November 2002

Behavioural changes in parasitized hosts have been experimentally investigated by comparing the swimming behaviour of roach, Rutilus rutilus, infected by the tapeworm Ligula intestinalis with that of uninfected roach when they were exposed to the same overhead heron stimulus. Before the stimulus was presented, infected fish swam close to the surface and uninfected fish were preferentially found near the bottom of the tank. The stimulus clearly induced a change in the vertical distribution of infected fish only. On the other hand, infected roach were less active than un infected fish before, during, and after the stimulus was presented. Proximate mechanisms of these behavioural changes are discussed. These behavioural differences, i.e., roach surfacing, swimming, and response to stimulus, probably favour the predation of infected roach by avian predators.
Vitamin E status and the dynamics of its transfer between mother and pup during lactation in grey seals (Halichoerus grypus)
Authors: Debier C , Pomeroy P P , Baret P V , Mignolet E , Larondelle Y
Published: November 2002

Concentrations of vitamin E, a powerful antioxidant, were measured in milk and serum of 18 grey seal (Halichoerus grypus) mothers and in the serum of their pups sampled up to 6 times between parturition and weaning on the Isle of May, Scotland, in 1998 and 2000. The vitamin E concentration in colostrum (89.4 ± 22.5 mg/kg milk; mean ± SD) was 4.5 times greater than that in later milk (20.9 ± 5.0 mg/kg milk). It then remained constant until the end of lactation. The decline in concentration of vitamin E in grey seal milk corresponded to a drop in the vitamin E concentration in mothers' serum between parturition (14.0 ± 4.8 mg/L serum) and the second half of the lactation period during which the serum vitamin E concentration remained stable (9.6 ± 3.2 mg/L serum). Circulating vitamin E concentrations varied significantly among mothers but there was no relationship with mother's age. Despite these differences between mothers, individuals produced milk with very similar vitamin E concentrations. The vitamin E concentration in grey seal pups' serum was low at birth (lowest concentration 3.1 mg/L serum) but increased sharply to a peak around days 13 (31.2 ± 5.2 mg/L serum). It then fell, before stabilizing until the end of lactation (21.1 ± 4.5 mg/L serum), reflecting the changes reported in the milk.
Foraging behaviour of Atlantic cod (Gadus morhua) larvae in relation to prey concentration
Authors: Puvanendran V , Leader L L , Brown J A
Published: November 2002

In spite of a tremendous amount of research on Atlantic cod (Gadus morhua) larvae, no information is available on the development of foraging behaviour over an extended period. We investigated the ontogeny of foraging behaviour of Atlantic cod larvae exposed to different prey concentrations from hatching to metamorphosis. The objective of this work was to determine if their foraging behaviour is influenced by prey concentration. Rotifers and (or) Artemia sp. were used as prey at concentrations of 0, 500, 1000, 2000, and 4000/L. During behavioural observations, which were carried out twice a week, foraging behaviour and activity of cod larvae were quantified. Larvae were sampled once a week and standard length and gut fullness were recorded. Larvae reared at concentrations of 1000 and 2000 prey/L swam significantly more but foraged (quantified by capture success) significantly less than the larvae reared at 4000 prey/L. Larvae reared at 4000 prey/L performed more orientations towards prey than larvae reared at all lower prey concentrations and the time spent per orientation increased from day 2 at all prey concentrations but declined as the larvae grew. However, this decline occurred earlier in larvae reared at 4000 prey/L than in larvae reared at other prey concentrations, and larvae reared at 4000 prey/L spent the shortest time per orientation at day 27 compared with day 34. Larvae reared at 4000 prey/L showed significantly higher success in capturing prey than larvae reared at all lower prey concentrations. After day 13 post hatch, larvae reared at 4000 prey/L were significantly greater in length than larvae reared at all other prey concentrations. Larvae reared at 0, 500, and 1000 prey/L did not survive beyond 11, 15, and 32 days, respectively, indicating that fewer than 2000 prey/L may not be adequate to keep cod larvae alive during intensive rearing. Our results suggest that the foraging behaviour of Atlantic cod larvae is influenced by prey concentration.
Foraging by Humboldt penguins (Spheniscus humboldti) during the chick-rearing period: general patterns, sex differences, and recommendations to reduce incidental catches in fishing nets
Authors: Taylor Sabrina S , Leonard Marty L , Boness Daryl J , Majluf Patricia
Published: November 2002

We studied the foraging behaviour of endangered Humboldt penguins (Spheniscus humboldti) to examine general foraging patterns, sex differences in foraging behaviour, and the reasons for incidental catches in fishing nets. Humboldt penguins foraged diurnally and typically made short, shallow dives within 30 m of the surface. Males and females made overnight (lasting 25.8 ± 3.4 h; mean ± SD) and day (10.4 ± 2.0 h) trips when they departed the colony to forage. Overnight trips were more common (68.2% of all trips) and were associated with a significantly greater amount of foraging time. Males dived to greater maximum depths than females but did not differ in other diving parameters, including foraging time, foraging effort, and proportions of day and overnight trips made. Adults may maintain their body condition during chick rearing by making a mixture of overnight and day trips. The two foraging periods observed during overnight trips may function to feed both the adults and the chicks, whereas the single period observed during day trips may function to accommodate the rate of provisioning required by the chicks. We suggest that both males and females would be protected from incidental catches in fishing nets if commercial fisheries avoided setting surface nets at night and setting nets between 0 and 30 m depth during the day in areas where penguins forage and transit.
Use of forest maps versus field surveys to measure summer habitat selection and sexual segregation in northern white-tailed deer
Authors: Lesage Louis , Crête Michel , Huot Jean , Ouellet Jean-Pierre
Published: November 2002

We used data derived from forest maps and ground surveys to study habitat preferences and sexual segregation in two populations of northern white-tailed deer (Odocoileus virginianus) living at low density in southeastern Quebec. Based on the reproductive-strategy hypothesis invoked to explain sexual segregation, we predicted that females would select habitat with denser cover than males did throughout the growing season, but that this tendency would decline with fawn maturation. Deer of both populations and sexes avoided agricultural lands; one population preferred regenerating clearcuts and disturbed conifer stands (balsam fir and spruce), whereas the other preferred undisturbed cedar stands. Based on map analyses we did not detect sexual segregation. Field surveys revealed that deer did not select forest stands at random and that habitat preferences differed by sex. Early in the growing season, both sexes tended to use mid-successional, dense stands, whereas males progressively used younger, more open stands later in the season. Detecting habitat preferences of forest mammals may require fine-scale details that are unavailable on maps derived from aerial photographs.
Parental care patterns and energetics of smallmouth bass (Micropterus dolomieu) and largemouth bass (Micropterus salmoides) monitored with activity transmitters
Authors: Cooke Steven J , Philipp David P , Weatherhead Patrick J
Published: November 2002

Male smallmouth bass (Micropterus dolomieu) and largemouth bass (Micropterus salmoides) care for their offspring from fertilization until the offspring disperse after becoming capable of avoiding predators. We used activity transmitters to monitor round-the-clock parental activity of both species throughout the nesting period, coupled with direct observational data collected while snorkeling, to determine whether nocturnal behaviour varied similarly to diurnal behaviour. In general, nesting males of both species were equally active during day and night, developmental-stage-specific patterns being evident during both periods. Consistent with theory, parental males of both species exhibited elevated levels of burst swimming (indicative of chasing nest predators) early in the nesting period. Unlike male smallmouth bass, however, male largemouth bass showed no decline in overall activity and energy expenditure in the later nesting stages as predicted from the greater mobility and dispersion of their broods, although burst-swimming activity decreased. Activity of nesting fish was approximately double that of non-nesting conspecifics, causing an increase in respiration rates of fish, estimated using a bioenergetics model. The results of our study suggest that physiological telemetry devices which provide both behavioural and energetic information enhance the study of parental care activity in centrarchid fishes, and may be equally useful in a variety of other taxa.
Do amphibians follow Bergmann's rule?
Authors: Ashton Kyle G
Published: November 2002

It is not clear whether Bergmann's rule, larger size within species in cooler areas, holds for any group of ectotherms. Data are presented and used to test whether amphibians show body-size patterns that follow Bergmann's rule. Available data with respect to latitude and elevation suggest that amphibians in general follow Bergmann's rule, with 23 of 34 species showing a larger body size at higher latitudes or elevations and an overall grand mean correlation coefficient of +0.35 for size with latitude or elevation. Salamanders show body-size patterns consistent with the overall trend, with 13 of 18 species having a larger body size at higher latitudes or elevations and a grand mean correlation coefficient of +0.42 for size with latitude or elevation. Anurans show a weaker trend towards concordance with Bergmann's rule with respect to latitude and elevation (10 of 16 species), but the grand mean correlation coefficient is significantly positive (+0.31). The relationship between body size and environmental temperature is less clear. Overall, amphibians show weak concordance with Bergmann's rule (9 of 16 species). The results of the only two studies of salamanders are consistent with Bergmann's rule; however, data for anurans show no trend (7 of 14 species in accordance). Thus, while salamanders appear to follow Bergmann's rule, any trends in anurans are tentative.
Male mate choice and male-male competition coexist in the humpback whale (Megaptera novaeangliae)
Authors: Craig Alison S , Herman Louis M , Pack Adam A
Published: November 2002

Male humpback whales (Megaptera novaeangliae) outnumber females on the winter grounds and compete physically for proximity to females. Analyses of identification photographs collected in Hawai'i from 1976 through 1995 and scan samples collected in 1998 showed that (i) reproductive potential (calving rate) for the following winter was greater for females without a calf than females with a calf, (ii) females without a calf were less likely to be found alone and more likely to be found in large pods than females with a calf, (iii) individual females were found in larger pods when without a calf than when with a calf, (iv) the probability of females with a calf being escorted by one or more males increased as the reproductive season progressed, and (v) head lunges occurred more commonly in all-adult pods than in pods containing a calf. We concluded that male humpback whales associate preferentially with females with high reproductive potential, that the attractiveness of individual females varies with their status (with a calf versus without a calf), that males become progressively less choosy over the course of the reproductive season as females without a calf become increasingly rare on the winter grounds, and that males expend more energy in competition over females without a calf than females with a calf.
Rates of increase in age-structured populations: a lesson from the European harbour seals
Authors: Härkönen Tero , Harding Karin C , Heide-Jørgensen Mads-Peter
Published: November 2002

Behavioural differences among population segments coupled with the transient dynamics of perturbed population structures lead to severely biased estimates of the intrinsic rates of increase in natural populations. This phenomenon is expected to occur in most populations that are structured by age, sex, state, or rank. The 1988 epizootic in European harbour seals (Phoca vitulina) perturbed the population composition radically. Detailed documentation of mass mortality, 20 years of population surveys, and data on age- and sex-specific behaviour were used to quantify biases in the observed rate of increase (λobs.), which in many areas substantially exceeded the "maximum rate of increase". This is serious, since λobs. is a key parameter, for example, in estimating potential biological removal or modelling population dynamics. For populations where the underlying age and sex composition is unknown, we suggest that data on fecundity and survival rates be used to find the upper theoretical rate of population increase. We found that the intrinsic rates of increase (λ1) in populations of true seals with even sex ratios and stable age structures cannot exceed 13% per year (λ1max. = 1.13). Frequently reported larger values are indicative of nonstable population structures or populations affected by migrations.
Intertidal zonation and seasonality of the marine hydroidDynamena pumila(Cnidaria: Hydrozoa)
Authors: Henry Lea-Anne
Published: November 2002

The vertical zonation and temporal dynamics of the marine hydroid Dynamena pumila were assessed across a wave-exposure gradient on five rocky shores in the Bay of Fundy, Atlantic Canada. Hydroid abundance and occupancy (i.e., percentage occurrence in a quadrat) were measured in 0.25-m2quadrats at eight vertical elevations for each site over four consecutive seasons. Hydroid abundance and occupancy were highly correlated (R2= 0.877). Estimates of hydroid fertility (percentage of sexually reproductive colonies) and size (stem height and number of branches) were obtained in five quadrats at every elevation over the four seasons. Abundance peaked at about 37.562.5% of the mean tidal range, with maximum abundance at the site with moderate wave exposure. Abundance peaked during the summer and dropped dramatically over the winter, particularly at the more wave-exposed sites. Winter ice scour and unfavourable environmental conditions reduced hydroid abundance, fertility, and size during the winter. This study demonstrates dramatic shifts in the distribution, fertility, and size of a marine hydroid. The importance of wave action, ice scour, and seasonal changes in environmental conditions is highlighted to emphasize their roles in regulating intertidal hydroid communities on boreal rocky shores.
Reproductive success in wood bison (Bison bison athabascae) established using molecular techniques
Authors: Wilson Gregory A , Olson Wes , Strobeck Curtis
Published: November 2002

In this study, we used 21 microsatellite loci to establish the reproductive success of the wood bison (Bison bison athabascae) population at Elk Island National Park, Alberta, Canada. Wood bison are considered threatened in Canada, and this population is currently used to found new populations. Despite the low levels of genetic variation in this population, we were able to establish paternity in 253 and maternity in 295 of the 317 calves born in Elk Island National Park over the 4-year study period. Roughly 40% of the mature males were reproductively successful each year. Mature males produced a mean of 3.8 offspring over the study period, with a range of 024. Each year, approximately 5070% of the cows produced calves, with a mean of 2.7 over the study period. Multiple linear regressions were performed to determine the effects of age, mass, heterozygosity, prior success, and the year of conception on male and female reproductive success. Only mass and prior success were useful in predicting male reproductive success. Female reproductive success depended on age, mass, and prior success and was also affected by environmental differences between years. No evidence was found for inbreeding avoidance in wood bison.