bluuebunny/crossref_metadata_2025 huggingface dataset:
Bed-site selection by European roe deer (Capreolus capreolus) in southern Norway during winter
Authors: Mysterud Atle , Østbye Eivind
Published: July 2008

Roe deer (Capreolus capreolus) beds were located by tracking in snow in the Lier valley in southern Norway during the winter of 1992–1993. Roe deer preferred to bed down below heavy canopy cover in order to derive thermal and possibly other benefits, whereas they fed in areas with little or no canopy cover. This led to the use of "forage beds" with little cover close to feeding areas and "cover beds" with heavy canopy cover farther away. The duration of the bedding period and temperature influenced the decision of the roe deer as to whether to leave the feeding area before bedding down. Bedding down in open habitat required more ground cover for protection against the wind, so wind was probably a significant factor in the operative temperature. Roe deer preferred to bed on microtopographic "tops," and animals in groups bedded down 2–4 m apart. This was interpreted as an antipredator strategy.
Annual variation in survival and reproduction of the primitively eusocial sweat beeHalictus ligatus(Hymenoptera: Halictidae)
Authors: Richards Miriam H. , Packer Laurence
Published: July 2008

We studied a nesting aggregation of the primitively eusocial sweat bee Halictus ligatus near Victoria in southern Ontario during the summers of 1984, 1990, and 1991. Differences in local weather patterns from year to year had marked effects on bee demography and behaviour, belying previous conclusions about "typical" social organization in this aggregation. In 1990, comparatively cool, rainy weather resulted in high nest-failure and low brood-survival rates, while in 1984 and 1991, relatively dry, warm weather had the opposite effect. In 1984 and 1990, spring nest initiation was synchronous and the emergence periods of the first (worker) and second (reproductive) broods were temporally distinct. In 1991, exceedingly warm spring weather caused asynchrony in the timing of nest initiation, accelerated brood and colony development, and continuous brood production. In 1984 and 1990, a few males were produced in the first brood but most were produced in the second brood several weeks later. In 1991, continuous brood production meant that production of males represented the transition between production of workers and of gynes (second-brood females). Patterns of demographic and social variation exhibited by H. ligatus at Victoria parallel those observed on a continent-wide geographic scale. This suggests that primitively eusocial sweat bees maintain a variety of reproductive options, adjusting their social behaviour in response to local environmental conditions.
Demography of a high-density coyote population
Authors: Windberg Lamar A.
Published: July 2008

The demography of a lightly exploited population of coyotes (Canis latrans) in Webb County, Texas, which has had historically high densities, was described from 1976 to 1986. The population fluctuated at high abundance, except for a decline in 1981–1982 following an epizootic of canine parvovirus. Sex ratios were even. Population natality was low, as only 39% of females had viable fetuses. Natality of yearlings (1.5–2.0 years) was lower and more variable than among adults (≥2.5 years). Juvenile (0.8 year) females rarely ovulated. A comparison among 33 radiotelemetered females in 1985 indicated that only territorial adults produced viable fetuses. The proportion of juveniles in spring averaged 0.34. Indices of juvenile survival from birth to the following spring varied from 0.09 to 0.73. Annual survival rates of adults (0.64–0.73) were high and constant. The annual population growth rate (spring to spring) was correlated positively with prey abundance in the preceding winter and negatively with coyote abundance at the beginning of each annual period. Although failure to ovulate and juvenile mortality were identified as key factors in annual variation in population loss, variability in natality among yearlings was identified as the demographic variable associated with relative abundance of coyotes and prey. Body condition of coyotes, as indexed by body mass and internal fat, was not poorer during years of low prey abundance. Interactions between social organization and food availability were implicated in regulation of the lightly exploited high-density population.
Familiarity and shoal cohesion in fathead minnows (Pimephales promelas): implications for antipredator behaviour
Authors: Chivers Douglas P. , Brown Grant E. , Smith R. Jan F.
Published: July 2008

We exposed groups of four fathead minnows (Pimephales promelas) that were familiar to each other and had been taken from naturally occurring shoals, and groups of four fish unfamiliar to each other, taken from four separate shoals, to either chemical stimuli from pike or a model fish predator (northern pike, Esox lucius). In response to both chemical stimuli from pike and the pike model, minnows from familiar groups showed greater shoal cohesion than those from unfamiliar groups. Tighter shoal cohesion should result in a higher probability of surviving an encounter with a predator. Fish in familiar shoals also exhibited more dashing, a known antipredator response, than those in unfamiliar groups. In addition, groups of familiar fish showed less freezing behaviour than unfamiliar groups. In response to the model fish predator, familiar shoals exhibited a greater number of predator inspections, and the number of inspectors per inspection visit was greater, than those in unfamiliar groups. These results suggest that preferential shoaling with familiar conspecifics leads to an increase in cooperative antipredator behaviour and may thereby lower a minnow's risk of predation.
Pneumocystis cariniiin arvicoline rodents: seasonal, interspecific, and geographic differences
Authors: Laakkonen J. , Soveri T. , Henttonen H. , Niemimaa J.
Published: July 2008

We studied the seasonal prevalence of Pneumocystis carinii in Microtus agrestis (n = 289, two locations), Clethrionomys glareolus (n = 37), and Myopus schisticolor (n = 31) in southern and central Finland, in C. glareolus (n = 406) and Microtus oeconomus (n = 167) in Finnish Lapland, and in Lemmus lemmus (n = 35) in a fall sample in northern Norway. All material came from populations at peak and declining densities. The highest prevalence of P. carinii in M. agrestis in both locations in southern and central Finland was observed in November (30 and 10%). Two M. oeconomus were infected with P. carinii. No individual of the other species examined was positive for P. carinii. The prevalence and intensity of P. carinii infection in M. agrestis fed experimental low-protein diets were similar to those found in the field material.
The digestive tract and digestive function in the North American porcupine and beaver
Authors: Vispo Conrad , Hume Ian D.
Published: July 2008

The morphology and function of the digestive tract of the largely arboreal porcupine (Erethizon dorsatum) and the semiaquatic beaver (Castor canadensis) were compared in relation to the similarly woody winter diet of these animals. Digesta particle sizes and Ca concentrations were consistently greater along the digestive tract of the beaver than along that of the porcupine. The small intestine of the beaver is 70% longer than that of the porcupine (P < 0.05 by ANCOVA). Both rodents are hind-gut fermenters and there was selective retention of small digesta particles (< 45 μm) in the cecum of both species. Hind-gut fermentation is confined to the cecum in the porcupine, but in the beaver the cecum and proximal colon function together as a fermentation chamber; the two anatomies appear to yield similar amounts of energy from the volatile fatty acids produced by fermentation, equivalent to 18–19% of the basal metabolic rate. A longer distal colon in the porcupine (P < 0.01 by ANCOVA) is related to greater resorption of water than in the beaver; dry matter content of the digesta increased from 13% in the cecum to 40% in the distal colon of the porcupine (P < 0.001 by ANOVA), but only from 20 to 33% in the beaver (P < 0.01 by ANOVA). High levels of Na accumulate in the porcupine cecum, presumably as a result of effective Na-conservation mechanisms.
Individual variation in nursing vocalizations of Hawaiian monk seal pups,Monachus schauinslandi(Phocidae, Pinnipedia), and lack of maternal recognition
Authors: Job Damon A. , Boness Daryl J. , Francis John M.
Published: July 2008

Vocalizations of individual Hawaiian monk seal pups, Monachus schauinslandi, do not have unique attributes that enable females to recognize their own offspring. Despite low aggregation density during pupping, aggressive encounters are common between females with pups. Fostering is prevalent and may reflect confusion over the identity of pups following aggressive encounters between females. All pup vocalizations were simple in structure and contained true harmonics. The coefficients of variation revealed considerable variance in vocalization structure within pups. Controlling for age, multivariate analyses of variance revealed significant differences among pups in vocalization attributes. Significant developmental changes occurred in vocalization structure for some pups but not for others. Discriminant function analysis suggested that it would be difficult for females to distinguish between the vocalizations of pups. The results of experiments conducted in the field showed that females did not discriminate between filial and alien pups by voice. In addition, females tended not to foster pups that had vocalizations similar to those of their own offspring. Thus, females seem to be unable to recognize their pups by voice. The apparent lack of vocal recognition of pups may contribute to the high frequency of fostering in this species.
Does fluctuating asymmetry reflect the importance of traits in little brown bats (Myotis lucifugus)?
Authors: Gummer David L. , Brigham R. Mark
Published: July 2008

Small random deviations from perfect bilateral symmetry define fluctuating asymmetry, and these deviations reflect an individual's inability to genetically control the development of a particular trait. Natural selection should act to minimize fluctuating asymmetry in traits that are most functionally important to an organism. Temperate-zone bats forage in flight and therefore symmetry of wing bones should be very important to fitness. Bats use their hind limbs only for hanging in roosts, therefore asymmetry in the main leg bone, the tibia, should not be as significant to a bat's fitness. We predicted that there would be less fluctuating asymmetry in the forearms than in the tibia. We measured the forearms and tibias of 119 little brown bats (Myotis lucifugus), and as predicted, forearm length did show less fluctuating asymmetry than tibia length. This result supports the hypothesis that traits can be ranked in order of functional importance according to the degree of fluctuating asymmetry found for each.
Critical thermal maxima of coho salmon (Oncorhynchus kisutch) fry under field and laboratory acclimation regimes
Authors: Konecki John T. , Woody Carol A. , Quinn Thomas P.
Published: July 2008

Juvenile coho salmon (Oncorhynchus kisutch) from three populations in Washington State were captured in the field and tested for critical thermal maximum (CTM). Tolerances varied among the populations (mean CTMs were 28.21, 29.13, and 29.23 °C) and exceeded published data from some laboratory tests. The population from a relatively cool stream had a lower CTM than the two populations from warmer streams. However, after the salmon had been in the laboratory for 3 months under constant, common temperature regimes, the CTMs no longer differed, indicating that the population-specific differences resulted from different acclimation regimes rather than from genetic adaptation.
Predation of Adélie penguins (Pygoscelis adeliae) by leopard seals (Hydrurga leptonyx) in Prydz Bay, Antarctica
Authors: Rogers T. , Bryden M. M.
Published: July 2008

The behaviour of leopard seals, Hydrurga leptonyx, feeding on Adélie penguins, Pygoscelis adeliae, was investigated between November 1993 and January 1994 in Prydz Bay, Antarctica. The seals were distributed along the fast-ice edge in locations where departing penguins congregated. Five different hunting techniques were observed, four of which were used through most of the summer. Individual leopard seals favoured specific hunting techniques. Hitherto, penguin hunting was believed to be carried out primarily by a few male seals; in this study, however, the predation observed involved many different individuals of both sexes. It is estimated that six leopard seals feeding in this area over a period of 120 days would consume 2.7% of the adult penguin population.
Habitat features associated with predation of New England cottontails: What scale is appropriate?
Authors: Brown Anne L. , Litvaitis John A.
Published: July 2008

We examined habitat features at several spatial scales that were associated with predation of New England cottontails (Sylvilagus transitionalis) by mammalian carnivores. The fate (killed or survived) of marked cottontails was compared with the characteristics of the habitat patch they occupied and composition of the surrounding landscape. The perimeter-to-area ratio of an occupied patch, the amount of disturbed habitat within 0.5 km of a patch, and the amount of coniferous forest within 1 km of a patch were greater for killed rabbits than for those that survived. The amount of water within 1 km and an index of landscape evenness were greater for rabbits that survived. Habitat features in the vicinity of patches occupied by cottontails apparently influenced the distribution and movements of carnivores. Characteristics of patches likely influenced rabbit exposure and predator success. We propose that predation of cottontails was a multiscaled process. Landscape composition (ca. 250 km2) influenced the relative abundance of predators. The distribution of predators within a landscape was a function of the distribution of life requisites (multiple patches, ca. 250 ha). Predators then selected a patch in which to forage on the basis of its relative productivity compared with adjacent patches. Finally, once a predator entered a patch, the vulnerability of a resident cottontail was dependent on the site (ca. 250 m2) occupied by the rabbit. This hierarchical approach may help resolve the current debate on the risk of predation in fragmented landscapes.
The influence of age and access to females on dominance in captive male brown-headed cowbirds (Molothrus ater)
Authors: Teather Kevin L. , Weatherhead Patrick J.
Published: July 2008

Pairs of captive male brown-headed cowbirds (Molothrus ater) housed with a female formed clear dominance relationships, and when an older male was housed with a yearling male, the adult was usually dominant. When the dominant male was removed to allow the subordinate male exclusive access to the female for 2 days, the subordinate became dominant in 5 of 19 (26.3%) trials when the males were placed together again. However, in 1 of 10 control trials, the subordinate male became dominant without having access to a female for 48 h, which suggests that access to a female was not the only reason for such status switches. Subordinate yearlings were as likely as subordinate adults to reverse their status. Size did not distinguish dominant from subordinate males or individuals that changed status from those that did not. However, subordinate males that became dominant displayed more when alone with the female than males that remained subordinate.
Body temperature and growth of nestling Northwestern Crows, Corvus caurinus
Authors: Verbeek Nicolaas A. M.
Published: July 2008

Nestling Northwestern Crows (Corvus caurinus) cannot maintain a steady body temperature on their own at hatching. The temperature of 1-day-old nestlings within 1 min after they were removed from the nest, but kept together and exposed to a mean ambient temperature of 10.6 °C, fell to 34.3 °C, but remained at 40–41 °C after 17 days of age. A steady improvement in thermogenesis was also apparent in single nestlings at the end of 21 min of exposure to ambient temperature, rising from 19 °C on day 1 to 40.6 °C on day 22. Adult females provide the heat that the young initially cannot provide for themselves, but at day 15, females essentially stop brooding to participate fully in gathering food. For the young, the cessation of daytime brooding coincides approximately with the eruption of feathers from their sheaths, the attainment of effective endothermy, the start of maximum daily growth rate of the feathers, and the point of inflection of the growth curve.
Epizootiology of the reindeer nose bot fly,Cephenemyia trompe(Modeer) (Diptera: Oestridae), in reindeer,Rangifer tarandus(L.), in Norway
Authors: Nilssen Arne C. , Haugerud Rolf E.
Published: July 2008

First-instar larvae of the reindeer nose bot fly, Cephenemyia trompe (Modeer) (Diptera: Oestridae), were sampled with a rinsing and sieving technique from 571 semidomesticated reindeer, Rangifer tarandus (L.), from different districts in northern Norway in the infection years 1983, 1984, 1985, 1987, and 1988, and from 44 wild reindeer from southern Norway (infection year 1983). This is the first comprehensive epizootiological study of this parasite from Fennoscandia. The first instar was found between 10 September to 25 May, the second instar from 11 February to 17 May, and the third instar from 3 April to 28 June. Old third-instar larvae were sometimes found trapped in the sinuses of the host. The overall prevalence of infection was 65.2% (range 6.7 – 100%) and the abundance (= relative density) was 11.53 (range 6.7 – 62.7). Individual intensities ranged from 0 to 221. There were significant differences in abundance between some districts and years. Distance and timing of the spring migration of the host are thought to be the major factors causing variability in infection levels between districts, whereas the summer climate during infection greatly influenced the differences between years. The frequency distribution was highly overdispersed (aggregated) and could adequately be described by the negative binomial model (overall parameter, k = 0.29, range 0.03 – 2.64). Heterogeneity in host behaviour during infestation is hypothesized to create this parasite distribution. Two measures of aggregation, Morisita's index of aggregation (IM) and1/k, decreased with larval burden, indicating that factors restricting parasite numbers (negative feedback) start to operate at high infection levels.
Phylogeny of the Euhirudinea: Independent evolution of blood feeding by leeches?
Authors: Siddall Mark E. , Burreson Eugene M.
Published: July 2008

The phylogenetic relationships of leeches were investigated by examining 22 species representative of the 10 euhirudinean familes in a cladistic analysis. Forty-five characters relating to internal and external morphology as well as cocoon deposition characteristics were used. Polarization of character states was accomplished using Acanthobdella peledina as the sister-taxon to the Euhirudinea. Two equally parsimonious solutions resulted. One was chosen as a preferred tree on the basis of defensible character state transformations. Previous speculations as to evolutionary branching patterns are largely consistent with the results obtained by cladistic analysis. Similarly, contemporary taxonomic groupings of leeches into higher taxonomic categories were found to be largely consistent with monophyletic groups identified in the analysis. The family Piscicolidae was found to be paraphyletic; elevating the constituent piscicolid subfamilies to the level of family is proposed. The origin of sanguivory as a life-history mode was investigated by optimizing this characteristic on the phylogenetic hypothesis, indicating the possibility of at least two origins of blood-feeding in the evolutionary history of leeches, depending largely on how the feeding biology of acanthobdellids is interpreted. Sanguivory is seen to have been lost at least twice.
Adjustment of basking postures in the high-altitude Iberian rock lizard (Lacerta monticola)
Authors: Martín Jose , López Pilar , Carrascal Luis M. , Salvador Alfredo
Published: July 2008

We studied the relationships between thermoregulatory basking postures and heating rates in the Iberian rock lizard (Lacerta monticola). Heating rates were high when body size was small, the substrate temperature was high, and the angle of incidence of the sun's rays was high (i.e., the rays were perpendicular to the lizard's body). However, heating rates were not related to the compass orientation of lizard's body axis to the sun (perpendicular versus in line with the sun). In the field, the slopes of the body axis of basking individuals were higher during the early morning. However, neither the cardinal orientation of a lizard's body axis to the sun nor the frequency of flattening varied during the morning. Postural adjustments to select an adequate angle of incidence of the sun's rays on the dorsal part of the body suggest that this behaviour might enhance absorption of solar radiation.
Effect of size-dependent muskrat (Ondatra zibethica) predation on the spatial distribution of a freshwater clam, Anodonta piscinalis Nilsson (Unionidae, Bivalvia)
Authors: Jokela Jukka , Mutikainen Pia
Published: July 2008

We studied the effect of central-place foraging by muskrats on the spatial distribution of freshwater clam Anodonta piscinalis. We also analysed the prey-size preference of muskrats. We collected A. piscinalis shells from four muskrat middens representing different prey populations and sampled the clam populations quantitatively. Muskrats had clear effects on the spatial distribution of the clams. At all study sites the area close to shore had no clams. The width of the empty area was correlated with the number of shells found in the muskrat midden. The density of clams decreased and their mean size increased with the distance from muskrat midden at two of the sites. Muskrats did not prey on clams smaller than 50 mm. Muskrats preferred 60- to 70-mm clams at three of the sites and 85- to 90-mm clams at the fourth. In an analysis conducted using ages, a selection gradient on the growth rate of clams was found for three of the study populations. However, spatial refuge from predation and inconsistency of selection may slow down or counterbalance the evolutionary response to predation.
Seasonal changes in gut morphology of the striped field mouse (Apodemus agrarius)
Authors: Borkowska Anetta
Published: July 2008

I studied seasonal changes in length and wet mass of the digestive tract and area of the mucosal surface of the small intestine in wild adult striped field mice (Apodemus agrarius). The length and mass of the gut varied with season in males but not females. The mucosal surface area of the small intestine was highly correlated with seasonal variations in the size of the alimentary tract. Changes in the surface area of the mucosa depended on changes in both villus size and the number of villi per unit area. The area of the intestinal mucosa varied during the year in both females and males, but unexpectedly, the mucosal surface area in females was significantly larger than in males only in autumn. Because gut size decreased toward late autumn, I suggest that late autumn was not a stressful period (i.e., because of low temperature or poor-quality food) for wild field mice. The decrease in gut parameters may have been an effect of declining metabolic requirements and completion of reproduction in late autumn.
Population differences in the schooling behaviour of the Trinidad guppy,Poecilia reticulata: adaptation or constraint?
Authors: Seghers Benoni H. , Magurran Anne E.
Published: July 2008

Populations of the guppy Poecilia reticulata in Trinidad vary markedly in their tendency to school. In many cases this variation in behaviour can be attributed to variation in the predation regime: guppies that co-occur with the pike cichlid, Crenicichla alta, spend more time schooling and form larger schools than their counterparts from low-risk habitats. However, the association between schooling tendency and predation risk is not ubiquitous. In this paper we document the behaviour of guppies from populations in two Trinidad drainages. Guppies from the (Lower) Aripo River (in the Caroni drainage) display well-coordinated schooling behaviour irrespective of whether they are observed in the wild or raised under standard conditions in the laboratory. By comparison, Oropuche River guppies (from the Oropuche drainage) show only a weak schooling tendency. The contrast between the two populations is apparent even in newborn guppies. As pike cichlids are abundant at both sites it seems unlikely that reduced predation risk can account for the weaker schooling of the Oropuche River fish. The behavioural differences in the two drainages are paralleled by considerable genetic divergence and we therefore consider the possibility of phylogenetic constraints on the evolution of schooling.
Sodium balance in ruffed grouse as influenced by sodium levels and plant secondary metabolites in quaking aspen
Authors: Jakubas Walter J. , Guglielmo Christopher G. , Vispo Conrad , Karasov William H.
Published: July 2008

Forages in boreal ecosystems are often deficient in sodium for mammalian herbivores. Moreover, consumption of various plant secondary metabolites has been associated with negative sodium balance in mammals. Neither of these issues has been investigated in birds, which differ from mammals in their ion-exchange processes and postrenal absorption of urine. Our objectives were to determine if ruffed grouse (Bonasa umbellus) can maintain sodium balance on quaking aspen (Populus tremuloides) flower buds, an important winter food, and to determine if the buds' primary plant secondary metabolite (coniferyl benzoate) further compromises a bird's sodium balance. Captive ruffed grouse were fed either aspen buds (0.063 mg∙g−1 sodium) or a formulated diet having different concentrations of coniferyl benzoate in no-choice feeding trials. Sodium excretion did not change in response to coniferyl benzoate intake or acid load from detoxication processes; however, birds were marginally in negative sodium balance (P = 0.035; −5.06 ± 2.05 mg∙kg−1∙d−1) when feeding on aspen buds. Sodium levels in the feces from free-ranging grouse (0.050 ± 0.0 mg∙g−1) and in their winter foods (0.065 mg∙g−1) indicated that these birds likely maintained sodium balance. We estimated that free-ranging ruffed grouse may need as little as 7 mg∙kg−1∙d−1 of sodium to maintain sodium balance, which is lower than the minimum sodium requirements for poultry and mammals.
Exploring territory quality in the North American red squirrel through removal experiments
Authors: Larsen Karl W. , Boutin Stan
Published: July 2008

If territory quality affects the fitness of its holder, then relatively unsuccessful individuals should relocate if given the opportunity to appropriate a higher quality territory. Relocation by these animals, however, may be prevented by habitat saturation, poor competitive ability, or the costs of relocating. We conducted two removal studies that created numerous territory vacancies in a population of the North American red squirrel (Tamiasciurus hudsonicus), thus providing favourable conditions for relocation. In both experiments, we tested whether nonbreeding females were more likely to relocate than breeding females, presumably because they (the nonbreeders) occupied relatively poor-quality territories. In our first experiment we permanently removed most of the squirrels from a study site and monitored the relative proportions of the remaining nonbreeding and breeding females that relocated. In our second experiment we monitored the response of squirrels to vacant territories that had been previously held by nonbreeding and breeding females, as well as by males. We also monitored the behaviour of squirrels that did not hold territories (dispersing offspring), as these individuals would not experience the same costs of relocation as adults. Our experiments showed that neither category of female was likely to relocate, regardless of the type of territory available. Both residents and dispersing offspring displayed no biases towards vacant territories that previously belonged to nonbreeding or breeding females or to males. Relocation does not appear to be a strategy for a female in this system to increase her reproductive opportunities. This suggests that either territory quality is inconsequential or the costs of relocation are prohibitive. Dispersing offspring also may be unable to select certain territories because of the premium placed on acquiring a territory, regardless of its quality.
Radiotelemetry error: location error method compared with error polygons and confidence ellipses
Authors: Zimmerman John W. , Powell Roger A.
Published: July 2008

We assert that researchers should use statistics derived from the linear distances between actual and estimated locations of test transmitters to estimate location error in radiotelemetry data. We call this approach the location error method. We used the distribution of such linear distances from a test data set from a study on black bears (Ursus americanus) in the mountains of North Carolina to predict error statistics for another test data set. We then compared the predicted with the actual error statistics. We also predicted error statistics for the second test data set using the error polygon method and Lenth's maximum likelihood estimator method. Linear and areal predictions of error using the location error method closely matched actual error in the second data set. The 90% confidence area calculated from test data contained 90% of the actual locations. The linear error measures taken from the error polygon method averaged twice the length of the 90% confidence distances generated from test data, and the 90% error polygons actually contained 95% of the true locations. The 95% confidence ellipse of Lenth's maximum likelihood estimator method [Formula: see text] was also a poor indicator of the precision of the actual location errors (95th percentile = 187 ha). Investigators should use bearing analysis on known locations only to find and correct biases in the bearing data prior to triangulation.
Urban pigeon populations: stability, home range, and the effect of removing individuals
Authors: Sol Daniel , Senar Joan Carles
Published: July 2008

The population stability and home ranges of rock doves (Columba livia var.) were investigated by means of surveys and monitoring of marked individuals. We also studied the population response to removal of animals. Pigeons used small home ranges, and there was very little exchange between adjacent populations despite their proximity. Individual day attendance at the home range was not bimodal, so individuals cannot be divided into regular and sporadic visitors. The number of individuals remained very stable during the 5 months of the study. Pigeons did not show any group cohesion, but individuals simply used the same small area. The consequence of the removal experiments was a rapid immigration of individuals from areas where no control was exerted, supporting the hypothesis that compensatory changes in dispersal are probably the main mechanism of pigeons' response to external perturbations. The rapid response after control and the disappearance of marked pigeons over time indicate the existence of some sampling movements of individuals between alternative sites. Redistribution of pigeons after the creation of a population vacuum would be in accordance with current models of habitat selection.
Reproduction, preweaning survival, and survival of adult sea otters at Kodiak Island, Alaska
Authors: Monson Daniel H. , DeGange Anthony R.
Published: July 2008

Radiotelemetry methods were used to examine the demographic characteristics of sea otters inhabiting the leading edge of an expanding population on Kodiak Island, Alaska. Fifteen male and 30 female sea otters were instrumented and followed from 1986 to 1990. Twenty-one percent of females were sexually mature (had pupped) at age 2, 57% by age 3, 88% by age 4, and 100% by age 5. Fifteen females produced 26 pups, an overall reproduction rate of 94% for mature females. The reproduction rate was 17, 45, 66, and 100% for 2-, 3-, 4-, and 5-year-olds, respectively. Eighty-five percent of observed pups survived to weaning (120 days), and the percentage of pups weaned ranged from 34% for pups of 2-year-olds to 100% for pups of 5-year-olds. At least three of four known pup losses occurred within a month of parturition. The mean pup dependency period for weaned pups was 153 days and the mean gestation period was 218 days. No synchrony in pupping activity was observed. Mean annual survival of adults was high. Estimates of survival ranged from 89 to 96% for females and 86 to 91% for males. Human harvest was the primary source of known mortality of adults. Our estimates of reproductive rates and survival of adults are at the high end of those reported for sea otters, but preweaning survival stands out as being particularly high. Abundant food resources and the availability of protected water presumably contributed to the high reproductive success observed in this recently established sea otter population.
Gill structure of a fish from an alkaline lake: effect of short-term exposure to neutral conditions
Authors: Laurent Pierre , Maina J. N. , Bergman Harold L. , Narahara Annie , Walsh Patrick J. , Wood Chris M.
Published: July 2008

The morphology and morphometry of the gills of Oreochromis alcalicus grahami, a unique ureogenic teleost that lives in the alkaline environment of Lake Magadi, Kenya (pH 10, [Formula: see text], temperature 30 – 40 °C) were examined by transmission electron, scanning electron and light microscopy. Fish were examined in normal Lake Magadi water and 2 – 3 or 24 h after transfer to Lake Magadi water neutralized to pH 7 with HCl (i.e., [Formula: see text] replaced with Cl−), a treatment that caused severe reductions in urea excretion and O2uptake, internal acidosis, and ionoregulatory disturbance. In Lake Magadi water, the organization of the filament epithelium of the gill was similar to that of sea water teleosts. Indeed, chloride cells were located at the bottom of pits bordered by overlying pavement cells and flanked by typical accessory cells. Total numbers of chloride cells remained unchanged after transfer to pH 7, but after 2 – 3 h, many were covered by pavement cells, restricting their communication with the external milieu. At 24 h, this trend was reversed, an observation indicative of a reactivation of chloride cells. Mucous cells were located at maximum density on the trailing edge of the filament; most of them were empty after 24 h at pH 7. The harmonic mean thickness of the lamellar epithelium (blood-to-water diffusion pathway) was very small and not altered by acute or longer term exposure to pH 7. A model of alterations in ion and acid – base transport accompanying the morphological changes is presented.
Status of the Hawaiian monk seal (Monachus schauinslandi) population
Authors: Gilmartin W. G. , Eberhardt L. L.
Published: July 2008

Restoration of the Hawaiian monk seal (Monachus schauinslandi) population to its former abundance poses a number of problems in managing a complex system. Sharp differences in history and current trend exist among the six major pupping sites. A severely unbalanced adult sex ratio has resulted in deaths from "mobbing" of estrus females at two sites. Some unknown factor apparently severely reduced the numbers of females at three of the sites and thus produced the observed excess of males. Sex ratios subsequently decreased, but losses of adult females continue at two sites. A simple model indicates that sex ratios at the two sites where mobbing is a problem would require more than 10 years to approach an equilibrium value. Data on trends from counts are compared with estimates from reproduction and survival rates and agree closely except at one site (Kure Atoll), where introductions of young females have been made.
Differences in age structure among field cricket populations (Orthoptera; Gryllidae): possible influence of a sex-biased parasitoid
Authors: Murray Anne-Marie , Cade William H.
Published: July 2008

This study examined age structure in adult populations of three species of field cricket, Gryllus veletis, G. pennsylvanicus, and G. integer. Adults were aged by counting growth layers in cross sections of tibiae. The study species differ in several life-history traits including the likelihood of parasitism by Ormia ochracea, a tachinid that orients to calling males. Gryllus integer is parasitized whereas G. veletis and G. pennsylvanicus are not. Such differences between the species should result in different age patterns. Data from field collections demonstrated that adult G. veletis and G. pennsylvanicus had similar maximum life-spans of about 4 weeks, and males were similar in age or slightly older than females. The maximum age for female G. integer was also about 4 weeks, but few males > 20 days old were encountered. Moreover, male G. integer were significantly younger than females in five out of six samples. This pattern in G. integer, evident in 2 successive years, could be consistent with sex-biased mortality by Ormia ochracea. The results are discussed in relation to differential longevities and the intensity of sexual selection on male mating behaviour.
Diel activity patterns of lake chubs and other fishes in a temperate stream
Authors: Reebs S. G. , Boudreau L. , Hardie P. , Cunjak R. A.
Published: July 2008

Baited and unbaited minnow traps were set in Catamaran Brook and the Little Southwest Miramichi River, New Brunswick, and checked every 4 h to determine the diel activity pattern of four species of stream-dwelling fish (threespine stickleback (Gasterosteus aculeatus), juvenile white sucker (Catostomus commersoni), blacknose dace (Rhinichthys atratulus), and lake chub (Couesius plumbeus)). Secondary goals were to determine whether the presence of bait inside minnow traps affected the diel patterns of captures and to compare patterns of lake chub captures in minnow traps with movement through a nearby fish-counting fence. All fish except lake chubs were diurnal, although strict diurnality was less obvious when bait was present in the traps. Lake chubs, which are normally diurnal in the laboratory, were captured mostly near dawn or dusk in unbaited traps, throughout the day in baited traps, and mostly at night at the fish-counting fence. We infer that chubs are active mostly at dawn or dusk, except (i) when strong food cues are present, in which case their activity may extend into the day, and (ii) during the spawning migration, when they move mostly at night. Relative inactivity by chubs during the day may be caused by the presence of piscivorous birds such as kingfishers and common mergansers, whose hunting efficiency may be higher under brighter light.
Influence de la température d'incubation sur le rapport mâle: femelle chez l'atipa, Hoplosternum littorale Hancock (1828)
Authors: Hostache Gérard , Pascal Michel , Tessier Christian
Published: July 2008

Sixteen batches of eggs collected immediately after spawning from five atipa (Hoplosternum littorale, (Hancock, 1828), Siluriformes, Callichthyidae) nests have been incubated at temperatures ranging from 22.5 to 32 °C. After a growing period of 8 months allowing all the fishes to express totally all secondary sexual characteristics, the sex of 9756 fishes was determined. The sexing criteria based on the color and length of the first ray of the pectoral fins are very reliable, and may lead to an error for only 0.3% of the fishes. For the 16 batches, the male sex ratio (ratio between the number of males and the total number of fishes) varies from 46.4 to 98.5% and is always greater than 50% with one exception. An overall analysis of the results shows no marked correlation (r2 = 0.312) between the proportions of males and the thermic conditions during incubation of eggs. But within each set of eggs from the same nest, this ratio systematically increases with increasing temperatures. The very low probability (0.0015) of such an event in the 15 batches of eggs from four independent nests suggests both a strong influence of the incubation temperature on the final proportion of males, and an important parental effect on the thermosensitivity of the offspring. The analysis shows clearly that a differential mortality between the sexes cannot account for the shifts towards such high proportions of males in the sex ratios. Thermosensitivity would be expressed early in this species, in the 3 days following spawning. The validity of these experimental results with regard to the natural environment as well as the potential adaptative advantage of such a mechanism for the species are discussed.
New taxa of Rhagidiidae (Acari: Prostigmata) from North America. Part IIIA. Genus Rhagidia Thorell: the gigas species-group
Authors: Zacharda Miloslav
Published: July 2008

Three new species of rhagidiid mites, Rhagidia breviseta, n.sp., R. parvilobata n.sp., and R. distisolenidiata n.sp., from the Nearctic region are described. Their interspecific relationships are discussed and two new species-groups, gigas and quadrisolenidiata, are defined.
Home ranges of female cunner, Tautogolabrus adspersus (Labridae), as determined by ultrasonic telemetry
Authors: Bradbury Carole , Green John M. , Bruce-Lockhart Michael
Published: July 2008

A fixed hydrophone array tracking system was used to study the use of space by sexually mature female cunner, Tautogolabrus adspersus (Walbaum, 1792). Ultrasonic transmitters attached externally through the dorsal musculature of eight females ranging in length from 194 to 250 mm provided 107 days of tracking data. Home-range areas varied from 300 to 2353 m2. Females utilized space disproportionately within their home-range boundaries, spending 60% of the time in 24–32% of their home-range area. Home ranges were significantly larger in the afternoon than in the morning and exhibited significant seasonal variation in size. Home-range size was not influenced by the state of the tide, and percent cloud cover and seawater temperature, individually, accounted for < 3.3% of the variance in home-range sizes. Changing energy requirements associated with spawning and overwintering torpor appeared to play a more important role than reproductive behaviour per se in determining home-range size.
Humpback whales (Megaptera novaeangliae) in Hervey Bay, Queensland: behaviour and responses to whale-watching vessels
Authors: Corkeron Peter J.
Published: July 2008

The effects of the presence of vessels on the behaviour of humpback whales (Megaptera novaeangliae) was studied in Hervey Bay, Queensland, where southward-migrating whales are the focus of a commercial whale-watching industry. The behaviour of whales was observed from a small yacht under sail. Rates of occurrence of units of behaviour for entire pods were obtained from continuous sampling of pods. Pods without calves showed lower rates of behaviour generally when vessels were within 300 m of them. Pods both with and without calves were more likely to dive rather than slip under when vessels were within 300 m. Hybrid multidimensional scaling of rates of behaviours of pods indicated differences between suites of behaviours exhibited by pods when vessels were within 300 m of them and when they were not. Classification of the patterns of occurrence of behaviours demonstrated that for pods both with and without calves, different units of behaviour tended to occur together when vessels were within 300 m and when they were not. Whale watching offers a nonlethal commercial use of whales, but in Hervey Bay, whale watching affects the behaviour of whales, which, although migrating, can be involved in breeding ground activities. Whether the short-term behavioural changes described here are accompanied by longer term avoidance of Hervey Bay by humpback whales as they migrate south remains to be determined.
Occurrence and behaviour of transient killer whales: seasonal and pod-specific variability, foraging behaviour, and prey handling
Authors: Baird Robin W. , Dill Lawrence M.
Published: July 2008

We studied the occurrence and behaviour of so-called transient killer whales (Orcinus orca) around southern Vancouver Island from 1986 to 1993. Occurrence and behaviour varied seasonally and among pods; some pods foraged almost entirely in open water and were recorded in the study area throughout the year, while others spent much of their time foraging around pinniped haulouts and other nearshore sites, and used the study area primarily during the harbour seal (Phoca vitulina) weaning–postweaning period. Overall use of the area was greatest during that period, and energy intake at that time was significantly greater than at other times of the year, probably because of the high encounter rates and ease of capture of harbour seal pups. Multipod groups of transients were frequently observed, as has been reported for "residents," but associations were biased towards those between pods that exhibited similar foraging tactics. Despite the occurrence of transients and residents within several kilometres of each other on nine occasions, mixed groups were never observed and transients appeared to avoid residents. Combined with previous studies on behavioural, ecological, and morphological differences, such avoidance behaviour supports the supposition that these populations are reproductively isolated.
Survival rates of radio-collared female polar bears and their dependent young
Authors: Amstrup S. C. , Durner G. M.
Published: July 2008

Polar bears (Ursus maritimus) are hunted throughout most of their range. In addition to hunting, polar bears of the Beaufort Sea region are exposed to mineral and hydrocarbon extraction and related human activities such as shipping, road building, and seismic testing. As human populations increase and demands for polar bears and other arctic resources escalate, reliable estimates of survivorship of polar bears are needed to predict and manage the impacts of those activities. We used the Kaplan–Meier model to estimate annual survival (with 95% confidence intervals) for radio-collared female polar bears and their dependent young that were followed during a 12-year study in the Alaskan Beaufort Sea. Survival of adult female polar bears was higher than had been previously thought: Ŝ = 0.969 (range 0.952–0.983). If human-caused mortalities were deleted, the computed survival rate was 0.996 (0.990–1.002). Survival of young from den exit to weaning was 0.676 (0.634–0.701). Survival during the second year of life, 0.860 (0.751–0.903), was substantially higher than during the first year, 0.651 (0.610–0.675). Shooting by local hunters accounted for 85% of the documented deaths of adult female polar bears. Conversely, 90% of documented losses of young accompanying radio-collared females were not directly caused by humans. Deaths of dependent young were independent of litter size (P = 0.36), indicating that parental investment in single cubs was not different from investment in litters of two or more. Precise estimates of the survival of independent juveniles and adult males still need to be developed.