bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of landscape type and extensive management on use of motorway roadsides by small mammals
Authors: Meunier Francis D , Corbin Johanna , Verheyden Christophe , Jouventin Pierre
Published: April 2011

We compared the relative abundances of small mammals along extensively managed motorway roadsides (with a narrow mown strip adjacent to the roadway) in three distinct landscapes (garrigue, pine plantation, and intensive farmland), to evaluate the relative effects of management and landscape traversed on roadside small-mammal populations. In each landscape, the landscape matrix (adjacent habitats), the mown strip, and the intervening unmown strip of roadside were sampled using snap traps. The roadside communities differed from those of landscape matrices, both in the relative abundances of individual species and in the proportion of each species captured. Species richness was greater on roadsides than in cropland and pine plantations, but there was no difference in the garrigue landscape. However, this greater richness was due to species that were rarely caught. The three dominant species (93.7% of captures), greater white-toothed shrew (Crocidura russula), wood mouse (Apodemus sylvaticus), and common vole (Microtus arvalis), were generally more abundant on roadsides than in the landscape matrices, especially in the unmown strip in the case of the first two species. Voles showed seasonal variation, being more abundant in mown strips at the population peak. The ecotone attributes of extensively managed motorway roadsides seem to be favourable to most small-mammal species, regardless of the landscape matrix.
Lake pH and aluminum concentration: consequences for developmental stability of the water strider Rheumatobates rileyi (Hemiptera: Gerridae)
Authors: Drover S , Leung B , Forbes M R , Mallory M L , McNicol D K
Published: April 2011

Lake acidity and metal contamination are environmental stresses that negatively affect many aquatic organisms in lakes in eastern Canada. Developmental stability, as indexed by fluctuating asymmetry (FA), is a putative cost-effective measure of environmental stress. In this study, we measured FA of the water strider Rheumatobates rileyi (L.) in lakes in the Sudbury area in relation to lake acidity (pH) and aluminum concentration. We did this to test the prediction that water striders inhabiting degraded lakes (low pH or high Al concentration) would exhibit decreased developmental stability (increased FA) compared with water striders from circumneutral lakes. As predicted we found that Al concentration (corrected for pH) was positively related to the average FA of samples. Contrary to expectation we found that pH (corrected for Al concentration) was also positively related to FA; thus, for a given Al concentration, more acid lakes had more symmetrical water striders than expected. We discuss the importance of our findings in relation to the use of FA as an index of environmental stress, for both water striders and other organisms.
How do body and paired-fin positions affect the ability of three teleost fishes to maneuver around bends?
Authors: Schrank Amy J , Webb Paul W , Mayberry Sarah
Published: April 2011

Deep-bodied fishes with an acanthopterygian fin distribution are traditionally considered more maneuverable than fishes with a fusiform body and less derived fin positions. One measure of fish maneuverability is the ability to make yawing turns. Goldfish (Carassius auratus), silver dollars (Metynnis hypsauchen), and angelfish (Pterophyllum scalare) were induced to swim through narrow tubes bent at angles of 0°, 45°, 90°, 135°, and 180°. These three species represent a range of body form and fin position from goldfish (fusiform body and less derived ventral placement of the paired fins) through silver dollar (deep body and the same fin positions as goldfish) to the acanthopterygian angelfish (deep body and lateral pectoral fins). The minimum width of tubes through which the fish could pass a bend increased with angle for all species and among species in the order goldfish < silver dollar < angelfish. Goldfish were consistently faster than angelfish, reflecting the routine use of body and caudal fin swimming, while angelfish routinely used median- and paired-fin swimming. Greater body depth and anterolateral pectoral fin positions were not associated with greater maneuverability. Goldfish were most adept at making yawing turns in confined spaces and in such circumstances were most maneuverable.
Identification of local populations of Lake Biwa catfish Silurus biwaensis in Japan on the basis of δ13C and δ15N analyses
Authors: Takai Noriyuki , Sakamoto Wataru
Published: April 2011

Carbon and nitrogen stable isotope ratios were used to examine the mixing of adult Lake Biwa catfish, Silurus biwaensis, in different areas of the lake and to identify the local populations. The isotopic signatures of its prey, the bluegill, Lepomis macrochirus, were also examined as indicators of each local food web. We analyzed 141 Lake Biwa catfish and 60 bluegills captured in the lake. The differences in δ13C values indicated that the two groups of catfish captured in the northern- and the southern-most spawning areas did not mix with each other frequently and were thus identified as local populations. The catfish captured in the mid-eastern area, where no spawning ground was found, were considered to be a group of migrators from the southernmost area, not a local population. These results are consistent with those obtained using ultrasonic tracking. It was therefore clearly demonstrated that stable isotope analysis is useful for identifying local populations of aquatic animals.
Volar adhesive pads of the feathertail glider, Acrobates pygmaeus (Marsupialia; Acrobatidae)
Authors: Rosenberg Herbert I , Rose Robert
Published: April 2011

The feathertail glider (Acrobates pygmaeus) is a mouse-sized marsupial that can cling to and run on smooth vertical panes of glass. To understand this remarkable ability, a comparative histological study of pads on the volar surface of the pes and manus of four species of marsupials was completed. Acrobates pygmaeus and Cercartetus concinnus have well-developed volar pads that consist of epidermal ridge - sweat gland complexes. Such pads are less developed in Tarsipes rostratus and are not externally visible in Sminthopsis crassicaudata. In addition to its possible role in capillary adhesion, the epidermal ridge - sweat gland complex of A. pygmaeus has a unique epidermal histo-architecture. Here, the stratum corneum consists of horizontal rows of cell remnants that do not become flattened or adpressed to form a stratified squamous epithelium. It is proposed that the tall stratum corneum resists shear and compression that develop when the feathertail glider completes a glide.
Regulation of incubation behavior in Black Brant
Authors: Eichholz Michael W , Sedinger James S
Published: April 2011

We assessed the influence of climatic, environmental, and biological factors on nest attentiveness of female Black Brant (Branta bernicla nigricans). Within females, nest attentiveness varied significantly with time of day, rainfall, ambient temperature, incubation day, and (incubation day)2. We examined variation among females in individual investment in reproduction by comparing the amounts of nutrients invested in the clutch with those invested in incubation. We compared nest attentiveness with the amount of nutrient reserves available to test the hypothesis that a trade-off exists between nutrient investment in eggs and investment in incubation. Among females, nest attentiveness was lower in 1992 (mean = 82%) than in 1993 (mean = 87%) and increased with clutch volume and mass. Our results show that environmental conditions influence incubation behavior in Black Brant. We detected a trade-off between investment in eggs and nest attentiveness, but the results are also consistent with the hypothesis that females vary in individual quality and this variation influences egg production as well as incubation.
Measurement of sulfate uptake and loss in the freshwater bivalveDreissena polymorphausing a semi-microassay
Authors: Dietz Thomas H , Byrne Roger A
Published: April 2011

Pondwater-acclimated Dreissena polymorpha maintained a sulfate concentration of about 2-3 mmol/L in the hemolymph. Sulfate was accumulated from the medium by a mechanism that was inhibited by diisothiocyanatostilbene disulfonic acid. The clearance of polyethylene glycol (PEG) injected into the hemolymph of D. polymorpha was 2-3 mL/(g dry tissue·h) and provided an estimate of the renal filtration rate in pondwater-acclimated animals. The clearance of sulfate injected into pondwater-acclimated D. polymorpha was about 20% of the PEG clearance, suggesting that the sulfate was being reabsorbed by the kidney. Abolishing the osmotic gradient by acclimating D. polymorpha to 10% seawater reduced PEG clearance to 0.3 mL/(g dry tissue·h). Sulfate clearance in animals acclimated to 10% seawater was similar to PEG clearance. Thus, D. polymorpha conserved sulfate when acclimated to the low-sulfate pond water, but not when acclimated to the more sulfate-rich 10% seawater medium.
Bioelectrical impedance analysis as a means of estimating total body water in grey seals
Authors: Bowen W Don , Beck Carrie A , Iverson Sara J
Published: April 2011

Estimates of total body water (TBW) play an important role in studies of body composition and energetics in mammals. We evaluated bioelectrical impedance analysis (BIA) as a means of rapidly and inexpensively estimating TBW in 38 grey seals (Halichoerus grypus). Twenty-two males and 16 females, representing the range of body sizes in the population, were studied at Sable Island, Nova Scotia. Seals were chemically immobilized with Telazol during BIA measurement. TBW was determined by dilution of tritiated water. The mean difference in duplicate BIA measurements did not differ significantly from zero. BIA-measured resistance accounted for 83% of the variation in TBW over a range of body masses from 38.5 to 294 kg. Bioelectrical conductor volume (length2/resistance) accounted for 97% of the variation in TBW. Average error in predicting TBW was +0.10% for a validation set of nine animals, but errors in predicting TBW of individual seals were up to 25%. Our results indicate that BIA measurements can be a valuable adjunct to the use of isotope dilution for estimating TBW in chemically immobilized grey seals; however, individual estimates may be associated with varying degrees of error.
Behavioral evidence for recognition of parasitized hosts by superparasitizing Pimpla nipponica (Hymenoptera: Ichneumonidae)
Authors: Ueno Takatoshi
Published: April 2011

Adaptive superparasitism theory is based on the assumption that a female parasitoid superparasitizes not because she fails to recognize prior parasitism of a host but because she decides to do so to increase her fitness. This theory suggests that recognition of prior parasitism is always advantageous, but it does not necessarily result in rejection of a parasitized host. The solitary parasitoid Pimpla nipponica Uchida readily superparasitizes when unparasitized hosts are scarce. Tests were conducted to examine whether P. nipponica positively superparasitized, even after it recognized prior parasitism. Direct observations of its oviposition behavior revealed that P. nipponica responded differently to unparasitized and parasitized hosts when ovipositing. The female drilled into parasitized hosts repeatedly to find a suitable egg-allocation site in the hosts. Also, the female probed parasitized hosts repeatedly with its ovipositor inserted in the hosts. These repeated drilling and probing actions were seldom observed on unparasitized hosts. Repeated drilling and probing actions were not associated with larvicide because no larva of the first female was killed by a superparasitizing female. The results indicated that superparasitism in P. nipponica did not result from a failure to recognize a host being parasitized, but resulted from its positive decision to superparasitize.
Relationship between hepatic deiodination of thyroxine and early oocyte development in rainbow trout, Oncorhynchus mykiss
Authors: Ruby Sylvia M , Eales J Geoffrey
Published: April 2011

We examined the relationship between five stages of ovarian growth and development and hepatic microsomal thyroxine (T4) deiodinating activity in rainbow trout, Oncorhynchus mykiss, held in the laboratory at 11.5°C. Thyroxine outer-ring deiodination (T4ORD) activity, which forms biologically active 3,5,3'-triiodothyronine (T3), was low when the gonadosomatic index (GSI = (ovary mass X 100) / body mass) was below 0.2 (stage I, previtellogenesis), but rose sharply between GSI values of 0.2 and 0.3 (stage II), when oocyte Balbiani activity, RNA synthesis, and endogenous vitellogenesis were maximal. Hepatic T4ORD activity was again low during exogenous vitellogenesis at GSI values of 0.3-12, which correspond to stages III-V. Hepatic T4 inner-ring deiodination (T4IRD), which forms biologically inactive 3,3',5'-triiodothyronine, was detected only at stage II. Plasma T3 concentrations were significantly higher at stage II than at stage IV (primary yolk globule formation). Our data indicate changes in systemic thyroidal status at stage II and are consistent with a role for T3 in early oogenesis in trout. Enhanced hepatic T3 production at the late Balbiani stage may be required for oocyte development.
Baculum and testes of the hooded seal (Cystophora cristata): growth and size-scaling and their relationships to sexual selection
Authors: Miller Edward H , Jones Ian L , Stenson Garry B
Published: April 2011

Growth and size-scaling of the baculum and testes in the moderately polygynous hooded seal (Cystophora cristata) were studied using 107 specimens of known age (1 month to 28 years) from the northwestern Atlantic. Bacular growth was rapid between 2 and 5 years of age: length increased 150% and "density" (i.e., mass/length) increased 8-fold and mass 20-fold. Growth continued throughout life. In large, old (>14 years) males, the baculum averaged 20.7 cm in length, 2.1 g/cm in density, and 44.4 g in mass. Bacular length increased relative to body length until seals were about 5 years of age, after which it averaged 8.2%. Testicular growth continued until the seals were about 12 years of age. Testes from breeding males >12 years old averaged 11.2 cm in length, 4.6 cm in width, and 138 g in mass; length averaged 4.9% of body length. In males 2-5 years of age, bacular and testicular sizes were positively allometric relative to body length; in older males, bacular mass and density were positively allometric, and bacular length and testicular size isometric, relative to body length. Bacular size was mostly positively allometric relative to testicular size (bacular length exhibited some isometry). Compared with that of the related and ecologically similar harp seal (Pagophilus groenlandicus), which is presumed to have a promiscuous mating system, the baculum of the hooded seal was structurally simpler and grew more quickly but reached a relatively smaller size in adults (8.2 vs. 9.9% of body length). Relative testicular length was also smaller (4.9 vs. 5.7% of body length) and bacular density lower (2.1 vs. 2.8 g/cm) than in the harp seal. These observations suggest that intra- or inter-sexual competition via copulation is weaker in the hooded seal.
Taxonomy of Venezuelan white-tailed deer (Odocoileus, Cervidae, Mammalia), based on cranial and mandibular traits
Authors: Molina Misael , Molinari Jesús
Published: April 2011

North and South American white-tailed deer are deemed to be a single species, Odocoileus virginianus. We used principal components and cluster analyses to compare crania and mandibles of Venezuelan and North American forms. We found that (1) Venezuelan and North American Odocoileus differ greatly from each other; (2) differentiation of groups within Venezuela exceeds that within North America; (3) the most divergent Venezuelan Odocoileus are those from Margarita Island and the Mérida Andean highlands; (4) the Margaritan Odocoileus does not differ in mandibular shape from its lowland congeners, but differs appreciably from other Venezuelan Odocoileus in having smaller mandibles and in cranial-mandibular characters; (5) the Mérida Andean Odocoileus contrasts markedly with other Venezuelan congeners in mandibular shape and cranial characters; (6) the remaining Venezuelan Odocoileus constitute a single group; (7) within this group, individuals from the Caribbean coast have larger mandibles and differ in some cranial characters. Thus, we propose that (a) Venezuelan and other Neotropical Odocoileus are not conspecific with O. virginianus; (b) Margaritan and Andean forms are distinct species: Odocoileus margaritae and Odocoileus lasiotis, respectively; (c) the remaining Venezuelan forms must be included within one species, Odocoileus cariacou; (d) Caribbean coast Odocoileus may represent an undescribed subspecies of O. cariacou.
Assimilation efficiency of prey in the Hawaiian monk seal (Monachus schauinslandi)
Authors: Goodman-Lowe Gwen D , Carpenter James R , Atkinson Shannon
Published: April 2011

Assimilation efficiency, digestive efficiency, metabolizable energy, and nitrogen retention in three captive adult male Hawaiian monk seals (Monachus schauinslandi) were measured with the indigestible marker chromic oxide for four experimental diets: a control diet of herring (Clupea harengus) and three test diets consisting of flagtail (Kuhlia sandvicensis), squid (Loligo sp.), and lobster (Panulirus marginatus), each of which was used in combination with herring. The addition of all three test prey to herring decreased the digestibility of gross energy by a mean of 3.58 ± 3.89%. Assimilation efficiency of gross energy was 96.1 ± 4.0% for herring, 73.8 ± 6.8% for flagtail, and 94.1 ± 5.7% for squid, but could not be determined for lobster. Digestive efficiency and metabolizable energy of the diets examined were high (4602.2 ± 247.1 and 4062.5 ± 178.4 kcal/d, respectively; 1 kcal = 4.18 kJ) and were positively correlated with the amount of gross energy ingested. Nitrogen retention was highest for the squid-herring diet (33.2 ± 1.2 g·d-1) followed by the lobster-herring diet (11.5 ± 3.3 g·d-1), the flagtail-herring diet (6.0 ± 0.0 g·d-1), and the herring (control) diet (-5.7 ± 1.6 g·d-1). This study indicates that prey which are both higher in protein and lower in fat than herring provide greater metabolizable energy for productive functions in Hawaiian monk seals.
The effects of supplemental perch sites on avian predation and demography of vole populations
Authors: Wolff Jerry O , Fox Tiffany , Skillen Robert R , Wang Guiming
Published: April 2011

We erected supplemental perches to evaluate their effectiveness in attracting perching raptors and to determine if an increase in raptor visitation could affect vole demography. Our model experimental system consisted of six 0.2-ha enclosures containing gray-tailed vole, Microtus canicaudus. The availability of supplemental perch sites had no effect on northern harriers, Circus cyaneus, but resulted in an 11-fold increase in visitation by American kestrels, Falco sparverius. This increased predation pressure did not affect vole population size, growth rate, or adult survival. However, juvenile recruitment and the proportion of reproductive females were lower in treatment sites than in control sites. Male voles had smaller home ranges and were less active than expected, which may have been an avoidance response to predation risk. High densities of voles, adequate cover in treatment sites, and good foraging areas with less cover in surrounding habitat may have negated the effects of the availability of supplemental perch sites. We conclude that adding perches can increase raptor visitation substantially but may have little effect on high-density vole populations.
Habitat selectivity of Clemmys guttata in central Ontario
Authors: Haxton Tim , Berrill Michael
Published: April 2011

A radiotelemetry study was conducted on spotted turtles, Clemmys guttata, in central Ontario from 28 April 1994 through 30 October 1995 to ascertain their habitat selection and requirements. Six turtles were tracked during 1994 and nine during 1995. During the active season, from just after emergence from hibernation in spring until late summer, marshes were primarily selected. As the season progressed, turtles shifted from marshes to predominantly bogs. Hibernation was exclusively in bogs. Spotted turtles displayed high fidelity to and were gregarious in hibernacula.
Hatching asynchrony and food stress in Ring-billed Gulls: an experimental study
Authors: Hébert Percy N , McNeil Raymond
Published: April 2011

We examined predictions derived from three hypotheses (hurry-up, peak-load reduction, and brood reduction) regarding the adaptive significance of hatching asynchrony. The study was conducted, in 1991 and 1992, in a colony of Ring-billed Gulls (Larus delawarensis) on l'île de la Couvée, Montréal, Québec, Canada. The hypotheses were examined by comparing the mass and size of 18- to 20-day-old chicks from broods that hatched asynchronously (unmanipulated) and synchronously (manipulated). We also compared feeding rates and fledging success between asynchronous and synchronous broods. Also, in 1992, a sample of asynchronous and synchronous broods was experimentally food stressed by providing them with an additional chick when the oldest resident chick was 4 or 5 days old. Consistent with the hurry-up hypothesis, hatch spreads were significantly shorter in 1991 when the mean clutch initiation date was significantly earlier compared with 1992. Also consistent with the hypothesis, hatch spreads increased significantly through the breeding season. In agreement with the peak-load-reduction hypothesis, feeding rates were significantly lower in asynchronous broods compared with synchronous broods. Contrary to the hypothesis, however, the feeding rate was similar for food-stressed asynchronous and food-stressed synchronous broods. As predicted by the brood-reduction hypothesis, survivorship was higher for first-hatched chicks in asynchronous broods compared with chicks in synchronous broods. Total brood loss as a result of starvation tended to occur less often in asynchronous broods compared with synchronous broods. Likewise, fledging success was higher in asynchronous broods compared with synchronous broods. However, contrary to the brood-reduction hypothesis, survival rate of first-hatched chicks, total brood loss, and fledging success were similar in food-stressed asynchronous and synchronous broods. The above results indicate that several benefits accure to Ring-billed Gulls from hatching asynchrony.
Seasonal oscillation in shore attendance and transience of New Zealand fur seals
Authors: Bradshaw Corey JA , Lalas Chris , Perriman Lyndon , Harcourt Robert G , Best Hugh , Davis Lloyd S
Published: April 2011

The New Zealand fur seal (Arctocephalus forsteri) appears to show regular shore attendance in the form of seasonal oscillations. This phenomenon should be quantified to properly interpret counts of fur seals >1 year old (i.e., non-pups). Here we test the predictability of peaks in the annual shore-attendance oscillation on Otago Peninsula using an autoregressive sine model and >2 years of intensive survey data. We predicted that the peak in fur seal numbers ashore would lie between 14 January - 4 April (1996) and 8 January - 2 April (1997), although this low predictability is undesirable when attempts are made to monitor population trends. Estimating population size from counts of non-pups also requires knowledge of the rate of turnover of individuals. Therefore, we tested the hypothesis that tagged animals from other colonies are immigrants to Otago Peninsula. With sightings on Otago Peninsula of fur seals tagged elsewhere in New Zealand, we used a Monte Carlo approach to simulate the expected frequency of single and multiple sightings of individuals. We found that the observed frequency of multiple sightings was significantly less than predicted by the model (P < 0.0001), indicating that tagged animals were transients. We also discovered that the sex ratio of tagged animals varied with breeding colony of origin (G1= 52.07, P < 0.0001), suggesting that the impetus for emigration differs among colonies. We concur with the view that counting pups is the only way to estimate the relative abundance of New Zealand fur seals. In addition, we showed that counts of non-pups cannot be used to estimate population size because an unknown proportion of individuals is transient. However, counting of pups does not address the issue of estimating relative abundance for locations with large numbers of nonbreeding individuals and few or no breeders. With few or no pups it is impossible to estimate relative abundance using counts of pups.
Chemical alarm signals in wild Trinidadian guppies (Poecilia reticulata)
Authors: Brown Grant E , Godin Jean-Guy J
Published: April 2011

We investigated the presence and possible function of chemical alarm signals (alarm pheromones) in wild Trinidadian guppies (Poecilia reticulata) using laboratory, trapping, and direct field observational methods. In laboratory experiments, female guppies from a population exposed to high predation significantly increased their shoaling, dashing, and freezing behaviours and significantly reduced area use when exposed to the skin extract of sympatric female guppies. When exposed to the skin extract of females from a low-predation population, female guppies from a high-predation population exhibited significant, though smaller, increases in antipredator behaviour. No significant differences in antipredator behaviours were noted when females were exposed to swordtail (Xiphophorus helleri) skin extract, which lacks any known alarm pheromone. We conducted two field experiments to confirm these laboratory results. In a trapping experiment, significantly more guppies were caught in funnel traps labelled with distilled water than in paired traps labelled with sympatric guppy skin extract. In a final experiment, a realistic model of a natural predator (pike cichlid, Crenicichla alta), paired with either sympatric guppy skin extract or distilled water, was presented to groups of free-ranging guppies in pools of a high-predation river. Significantly fewer guppies were observed within a 50-cm radius of the predator model and significantly fewer guppies inspected the model when it was paired with guppy skin extract versus distilled water. Taken together, our results strongly suggest the presence of a chemical alarm signal (alarm pheromone) in the Trinidadian guppy, establish the validity of laboratory and trapping studies in the investigation of chemical alarm signalling, and demonstrate that alarm pheromones may function to mediate predation risk under natural conditions in the guppy.
Environmental influences on geographic variation in body size of western bobcats
Authors: Wigginton John D , Dobson F Stephen
Published: April 2011

Hypotheses that explain geographic variation in body size were examined using cranial measurements of 950 bobcats (Lynx rufus) from western North America. Bobcats were divided into 25 geographic localities of similar habitats and landform (based on ecoregions). Principal component analyses were used to derive a single estimate of size from scores on the first principal component. Males and females were examined separately, because they were significantly dimorphic in body size and because sex and locality exhibited a significant interaction. We expected that female body size would best reflect environmental influences, because male size may be influenced by sexual selection. We found significant geographic variation in bobcat body size, with about 44% of the variation in males and 47% of the variation in females accounted for by comparison among the localities. We also found that variation in body size was associated with Bergmann's rule, as indicated by significant multiple regression of body size of males (R2 = 0.426) and females (R2 = 0.480) on latitude and elevation. Using correlation and regression analyses, we examined the association of body size with selected environmental variables that represent the classical physiological explanation of Bergmann's rule, James' moisture-humidity modification of Bergmann's rule, Rosenzweig's productivity hypothesis, and Boyce's seasonality hypothesis. Only the productivity hypothesis was not supported. The relative strengths of associations suggested, however, that James' modification was better supported than the classical explanation for Bergmann's rule. Path analyses permitted further discrimination of hypotheses, and only the seasonality hypothesis received significant support. As expected, this support was only evident for females. Path analysis may provide a tool for evaluating relative strengths of competing but correlated explanations of geographic variation.
Validation of incubation duration as an index of the sex ratio of hatchling sea turtles
Authors: Mrosovsky N , Baptistotte Cecília , Godfrey Matthew H
Published: April 2011

One method of estimating the sex ratio of hatchling sea turtles is to use the incubation duration. Long and short durations imply low and high temperatures, respectively. In turtle species whose sex is determined by temperature, males are produced at low temperatures and females at high temperatures. This study assesses the validity of using incubation duration to estimate the sex ratio. Samples of hatchling loggerhead turtles (Caretta caretta) were collected from nests with known incubation durations, and sex was ascertained by means of histology. The sex ratio of groups of nests determined by histology was compared with that predicted from previous relationships between incubation duration and sex ratio. For conditions causing relatively long or relatively short incubation durations, the sex ratio could be predicted with considerable accuracy. For conditions causing durations nearer to the pivotal duration (that which gives 50% of each sex), predictions could be off by 10%, depending on the distribution of incubation durations, but it was still possible to determine whether ratios were highly skewed or approximately balanced. Estimating sex ratios of hatchling sea turtles from incubation durations is simple, cheap, and can be used retrospectively.
Predation and breeding success in roseate terns (Sterna dougallii)
Authors: Whittam Rebecca M , Leonard Marty L
Published: April 2011

Predation limits the breeding success of many colonial seabirds and is a major factor in the decline of a number of marine bird species. The goal of our study was to determine how predation affects the breeding success of threatened roseate terns (Sterna dougallii) nesting on Country Island, Nova Scotia, Canada. This site is one of only three Canadian breeding colonies and the first to be systematically studied. Forty-five pairs of roseate terns, 330 pairs of arctic terns (Sterna paradisaea), and 130 pairs of common terns (Sterna hirundo) nested at this colony in 1996. Predation was the most important source of egg and chick mortality for roseate terns on Country Island. Twenty-four percent (18/75 eggs) of roseate tern eggs were depredated, presumably by corvids, while 77% (24/31 chicks) of roseate tern chicks were depredated by gulls. Overall, roseate terns at this site produced a maximum of 0.11 fledglings per nest. Roseate terns abandoned Country Island in 1997, presumably because of predation in 1996. We discuss the implications of our results for the long-term survival and management of the Canadian roseate tern population.
Drinking behaviour inAnolis carolinensis(Voigt, 1837) andOplurus cuvieri(Gray, 1831) (Reptilia: Iguania: Iguanidae)
Authors: Wagemans F , Chardon M , Gasc J -P , Renous S , Bels V L
Published: April 2011

The aim of this study is to describe the drinking mechanism in two iguanid species, Anolis carolinensis and Oplurus cuvieri. Both live in varied ecological environments where water may be either very abundant or exceedingly scarce. Anolis carolinensis is an arboreal species of the southern United States; in its environment, water is constantly available in drops or small reservoirs. Oplurus cuvieri lives in northwestern Madagascar, enduring very dry and very wet seasons and high insolation. In the dry season, few pools of water or dewdrops remain available. Light and X-ray filming of drinking revealed that the two species almost always use similar mechanisms to introduce water into the buccal cavity. During immersion, the tongue is used to collect water and push it from the front to the back of the buccal cavity. During emersion, water reaches the esophagus, mainly as a result of gravity. In A. carolinensis, this mechanism is used regardless of the amount of water available. In O. cuvieri, the role of the tongue is less important when water is abundant. In similar conditions, therefore, the two species of Iguania use similar mechanisms for collecting and swallowing water. This drinking mechanism has been observed in Lacerta viridis in the sister-group Scleroglossa.
Latitudinal variation in locomotor activity rhythm in adult Drosophila ananassae
Authors: Joshi Dilip S
Published: April 2011

The parameters of the circadian rhythm of adult locomotor activity in strains of Drosophila ananassae originating between 6° and 34°N were variable and latitude-dependent. Two representative southern strains became active before sunrise, but one representative northern strain began activity after sunrise in nature. During entrainment to a 12 h light (L) : 12 h dark (D) cycle in the laboratory, the southern strains showed two peaks of activity, at the beginning and end of photophase, whereas the northern strains showed a single uninterrupted activity peak starting about 3 h after the lights-on. Among the strains, the phase angle difference (Ψ) during entrainment to 12 h L : 12 h D varied by about 5 h, the period of free-running rhythm(τ) in constant darkness by 3 h, the duration of the activity phase (α) by 7 h, and the duration of the resting phase (ρ) by 10 h. Lower latitude was correlated with an early Ψ (r = 0.977), a short τ (r = 0.975), a prolonged α (r = -0.995), a short ρ (r = 0.995) and a large α/ρ ratio (r = -0.963).
Effects of a late snowstorm and rain on survival and reproductive success in Columbian ground squirrels (Spermophilus columbianus)
Authors: Neuhaus Peter , Bennett Ron , Hubbs Anne
Published: April 2011

Body mass changes, reproductive success, and mortality were studied in Columbian ground squirrels (Spermophilus columbianus) in southern Alberta from 1994 to 1996. Spring weather conditions varied widely between years: 1994 was a dry, warm spring, 1995 was extremely rainy, and in 1996 a major snowstorm during the first 2 weeks of May stopped foraging by ground squirrels during the latter part of their mating season. We predicted that adverse weather conditions during the mating season in general, and this snowstorm specifically, would influence reproductive success and survival. Mass changes during the first 2 weeks of May varied from year to year and reflected major differences in spring weather. Female reproductive success was highest in 1994 and lowest in 1996. In 1996, we observed a higher mass loss during the first 2 weeks of May in females that subsequently did not wean a litter than in those that did. Weaning success was higher for females that mated after the snowstorm than for those that mated before or during the snowstorm. The mortality rate during mating in 1996 was higher in males than in females and was higher than in 1994 or 1995 for both sexes. Overall weaning success of females was highest in 1994 and lowest in 1996. We concluded that the energetic costs of mating can lead to a high mortality rate for males and low reproductive success for females.
Body-size comparisons of alpine- and forest-wintering woodland caribou herds in the Yukon
Authors: Kuzyk Gerald W , Dehn Michael M , Farnell Richard S
Published: April 2011

Information from radiotelemetry studies has shown that woodland caribou (Rangifer tarandus caribou) living in the snow-shadow region of the southwest part of the Yukon spend part of the winter in the subalpine and alpine zones. Other woodland caribou living in areas with high snowfall in central and eastern Yukon have traditional winter ranges in forested lowlands. We theorize that selective forces exerted by the wintering environments will have induced differences in caribou body characteristics, and we test the hypothesis that woodland caribou that winter in the alpine zone are phenotypically different from those wintering in forested environments. We compared five physical measurements from 382 female woodland caribou in 11 Yukon herds. Our results indicate a significant (14 cm) difference in shoulder height between forest- and alpine-wintering groups, but provide no support for the hypothesis that the difference is due to snow depth. There were no significant differences in other body measurements or in body proportions. It is also unlikely that the difference in shoulder height is due to winter nutrition, since body condition scores did not differ between forest- and alpine-wintering groups. We discuss seasonal nutrition, predation, and migration as alternative explanations for our results.
Geographic variations in life-history characteristics of white-spotted charr (Salvelinus leucomaenis)
Authors: Yamamoto Shoichiro , Morita Kentaro , Goto Akira
Published: April 2011

Breeding-population structure, age and size at maturity, age and size at smolting, and riverine growth rate were investigated for three populations of white-spotted charr (Salvelinus leucomaenis) in the Nairo, Haraki, and Takahara rivers in Japan. The breeding populations in the Nairo and Haraki rivers on Hokkaido Island exhibited size polymorphism, comprising smaller mature parr and larger migrants. On the other hand, the population in the Takahara River on central Honshu Island showed a monomorphic structure, being composed of mature parr only. Maturation at the parr stage was positively associated with body size. The patterns of length-specific maturation ratios in the three rivers were similar, although females matured at a larger size than males. Smolt sizes differed between the polymorphic populations in the Nairo and Haraki rivers, but size relationships between the sexes were similar in the two populations. The incidence of smolts of a given length within populations was much higher in the northern Nairo River population than in the more southerly Haraki River population. These observations indicate that among-population variation in the structure of white-spotted charr populations might be related to differences in the relative proportions of mature parr and smolts in the population. We suggest that the relative difference in size thresholds between smolting and maturation determines the relative incidence of mature parr and smolts, both within and among populations and between the sexes, which in turn regulates the breeding-population structure.
Spontaneous and induced metamorphosis in the American brook lamprey, Lampetra appendix
Authors: Holmes John A , Chu Helen , Khanam Syeda A , Manzon Richard G , Youson John H
Published: April 2011

We described the seven stages of spontaneous metamorphosis in the American brook lamprey (Lampetra appendix) and assessed the importance of size as a determinant of spontaneous and induced metamorphosis. Serum concentrations of the thyroid hormones (TH) thyroxine (T4) and triiodothyronine (T3) were measured in metamorphosing and nonmetamorphosing L. appendix. The sequence of stages in metamorphosis and changes in the relative lengths of most body regions were consistent with data reported for other lamprey species. However, premetamorphic and metamorphosing L. appendix in the early stages of metamorphosis (1-3) were much larger in size (at least 155 mm and 5.40 g) than has been observed for other lamprey species. Serum concentrations of T4 and T3 were high by the end of the larval period and declined significantly by stage 2 of metamorphosis. Larvae greater than or equal to 130 mm in length were treated with either potassium perchlorate (KClO4; 0.01 and 0.05%) or 10 mg/L propylthiouracil (PTU; 0.0001%) for 117 days from September to January to determine if metamorphosis could be induced by these goitrogens. Both concentrations of KClO4 successfully induced metamorphosis in L. appendix, but the incidence of metamorphosis (62%) was much lower than reported in sea lampreys (98%) of comparable size. Serum concentrations of T4 and T3 declined by 64-76 and 93-96% relative to control values, respectively, in metamorphosing and nonmetamorphosing L. appendix treated with KClO4. PTU elicited declines of 55% for T4 and 80% for T3, but only one animal metamorphosed. Based on these data, we conclude that a decline in serum TH levels is necessary for metamorphosis in L. appendix, but not sufficient by itself to trigger the process.
Mitochondrial and microsatellite DNA analyses of harbour seal population structure in the northeast Pacific Ocean
Authors: Burg Theresa M , Trites Andrew W , Smith Michael J
Published: April 2011

The genetic diversity and population structure of harbour seals (Phoca vitulina richardsi) along the coasts of British Columbia and parts of Alaska were investigated using both mitochondrial DNA (mtDNA) and nuclear DNA. A 475-bp fragment of the mitochondrial control region was amplified and sequenced from 128 animals. Sixty variable sites defined 72 mtDNA haplotypes with pairwise nucleotide differences as high as 5%. Fifty-eight haplotypes were represented by a single individual, and shared haplotypes were generally restricted to a small geographic range. Phylogenetic reconstruction revealed two distinct populations comprising (i) southern British Columbia and (ii) northern British Columbia - southeast Alaska. Furthermore, the order of the clades suggests that the Pacific Ocean was colonized at least twice, 670 000 and 380 000 years ago. Haplotypes from the first invasion are restricted to a small number of seals around southern Vancouver Island. Analyses of five polymorphic microsatellite loci showed significant differences between the populations of southern British Columbia and northern British Columbia - Alaska. Migration rates for males based on microsatellite data (3-22 seals/generation) were higher than those obtained for females from mtDNA data (0.3 females/generation). Combining all the DNA data collected to date suggests that there are at least three populations of harbour seals in the Pacific composed of seals from (i) Japan, Russia, Alaska, and northern British Columbia, (ii) southern British Columbia and Puget Sound, Washington, and (iii) the outer coasts of Washington, Oregon, and California. The data do not support the existence of two subspecies of harbour seals in the Pacific Ocean.
Developmental costs of male sexual traits in the water strider Rheumatobates rileyi
Authors: Westlake Kathleen P , Rowe Locke
Published: April 2011

Natural selection is thought to impose costs on sexually selected traits and thereby constrain their evolutionary modification. Where sexually selected traits involve increases in size or structural elaboration, development of the traits may be costly. Males of some species in the water strider genus Rheumatobates have dramatically elaborated antennae and legs. In a pair of experiments on Rheumatobates rileyi, we tested the hypothesis that in males, the development rate is decreased and mortality increased relative to unelaborated females during the final instar, when these traits were substantially developed. In the first experiment, we reared individual larvae through to adult that were brought into the laboratory during the third, fourth, and fifth (final) instars. The development rate was reduced and the mortality increased during the final intermolt period in males relative to females. The effect on development rate was highly significant, but the effect on mortality was not. Notably, there was no effect of sex on the duration of the fourth instar, when male modifications are not expressed. In a second experiment, 4 potentially cannibalistic adults were included with fifth-instar larvae. We found no effect of potential cannibals on either development rate or mortality of instars. However, as in the first experiment, the development rate was significantly reduced in males relative to females. Mortality of males was also higher than that of females, although this effect was not significant. Meta-analysis of all our mortality results indicate that mortality of developing fifth-instars was higher in males than in females. Our results are consistent with the hypothesis that development of elaborate sexual traits in male R. rileyi is costly.
Field metabolic rate of wild turkeys in winter
Authors: Coup R N , Pekins P J
Published: April 2011

We investigated the winter bioenergetics of eastern wild turkeys (Meleagris gallopavo sylvestris) by measuring standard metabolic rate (SMR) and existence metabolism (EM) of captive turkeys and field metabolic rate (FMR) of free-ranging turkeys. Mean SMR and EM were 0.511 ± 0.040 mL O2·g-1·h-1 and 499.7 ± 17.7 kJ·kg body mass-0.734·d-1 (mean ± SE) as measured by indirect respirometry and food consumption, respectively. FMR was measured with doubly labeled water and was 10.5% higher in juvenile (0.976 ± 0.039 L CO2·kg-0.734·h-1) than adult turkeys (0.883 ± 0.034 L CO2·kg-0.734·h-1); their FMR:SMR ratios were 1.74 and 1.58, respectively. Juvenile turkeys weighed less and had less body fat (13.5%) than adults (18.9%). Mean FMR was lowest in 1996, when ground forage was unavailable and weather was more windy and cold than in 1995, when ground forage was available and the turkeys' activity and range were greater. Turkeys reduced FMR in 1996 by restricting movement and range, and using proximate shelter and supplemental food. We predict that juvenile turkeys are at an energetic disadvantage when food availability is restricted because of their higher FMR, lower body and fat masses, and higher activity costs than adults.
Huemul (Hippocamelus bisulcus) sociality at a periglacial site: sexual aggregation and habitat effects on group size
Authors: Frid Alejandro
Published: April 2011

I studied social organisation of the huemul (Hippocamelus bisulcus), an Andean deer, during spring in coastal Chile. Analyses are based on individually recognised adults without young of the year. Deer that were not alone generally joined groups containing both sexes, and the proportion of time individuals spent in mixed-sex groups increased with the individual's mean group size. The absence of sexual segregation during spring is unusual among sexually dimorphic ungulates, and possibly reflected little variability in food distribution and (or) sex-specific predation pressure. Group sizes of individuals observed on multiple days increased strongly with distance from rocky slopes, and this relationship appeared to be unaffected by food distribution. These results suggest that the risk of predation, probably from cougars (Felis concolor) and (or) human hunters with dogs (Canis familiaris), is lower on rocky slopes than in valley-bottom habitats. Group sizes of individuals seen only once, however, were independent of distance from rocky slopes, possibly because these individuals were transients that did not integrate into the social structure of resident deer. The effect of rocky slopes on group sizes of individuals observed on multiple days is more characteristic of mountain Caprinae than of deer. The huemul is endangered, and its extinction could represent a substantial loss in the behavioural diversity of the Cervidae.