bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cyprinid prey remains in otter Lutra lutra faeces: some words of caution
Authors: Carss D. N. , Nelson K. C. 
Published: February 2006

AbstractThis study investigates errors associated with the recovery of cyprinid remains in otter Lutra lutra spraints. Cyprinid fishes (Cyprinidae – the carps) comprise the largest family of freshwater fishes in the world with around 2000 known species. They form the major group of freshwater fishes in Europe with a total of 80 species, 16 of which occur in Britain (Winfield & Nelson, 1991). These fishes are commonly taken by otters Lutra lutra throughout the predator's geographical range, their prevalence in the diet apparently varying in relation to their abundance. No more than three species are commonly recorded as otter prey in Britain, Ireland, and Scandinavia (e.g. Wise, Linn & Kennedy, 1981; Kyne, Smal & Fairley, 1989; Erlinge, 1967, respectively), while at least five are in eastern Poland and southern Spain (e.g. Brzezinski, Jedrzejewski & Jedrzejewska, 1993; Lopez‐Nieves & Hernando, 1984, respectively). These fishes offer an opportunity to investigate otter prey selection on relatively complex prey communities (cf. Carss et al., 1998) as they form mixed‐species assemblages (Winfield & Nelson, 1991). However, Carss (1995) concluded that if studies of otter feeding ecology were to become more than mere lists of prey items, there was an urgent need to quantify current spraint analysis techniques and their associated errors more rigorously than before. This is undoubtedly true for studies which attempt to determine the species‐ and size‐composition of cyprinids in the diet of otters.
Polymorphism, mating preferences and sexual selection in the Arctic skua
Authors: Phillips R. A. , Furness R. W. 
Published: February 2006

AbstractThe intensive study of the Arctic skua (Stercorarius parasiticus) population on Fair Isle has provided an example of the maintenance of a stable polymorphism by sexual selection in conjunction with assortative mating (O'Donald, 1983). We tested several of O'Donald's hypotheses using data collected from the large colony of Arctic skuas on Foula. There was some evidence for assortative mating of the phenotypes but this did not confer any short‐term fitness advantage. In contrast to the situation on Fair Isle, we found little indication that sexual selection took place for dark males since no differences in timing of breeding or productivity were evident between the two male phenotypes in new partnerships. Nor could we detect variation in adult body size, body condition, or any life‐history characteristic between melanic and pale birds of either sex. Many of the selection pressures documented on Fair Isle appear to be absent at the neighbouring Foula, despite a fair degree of gene flow between these colonies. The frequency of pale adults on Foula and in Shetland as a whole has declined since the 1970s, indicating that currently directional selection may be favouring the melanic phenotypes at the southern end of the breeding range.
Maternal investment and factors affecting offspring size in polar bears (Ursus maritimus)
Authors: Derocher A. E. , Stirling I. 
Published: February 2006

AbstractWe examined data on live‐captured polar bears (Ursus maritimus) from western Hudson Bay relative to differential maternal investment and facultative sex ratio theory. In spring, shortly after den emergence, we found no differences in mass or body length of cubs in litters of one or two. In triplet litters captured in spring, male cubs were larger than females in both mass and body length, possibly due to sibling competition for limited maternal resources. In cubs captured during autumn, sex‐based differences in mass and body length were found only in litters of one with males larger than females. Yearling males captured in autumn were heavier and longer than females in litters of one and two. In twin litters of one male and one female cub in spring and autumn, we found no differences in mass or body length. Except singleton female cubs in spring and female and male triplets in spring, cub and yearling mass were correlated with maternal mass. Mothers with singletons in spring were more likely to have male cubs but, in general, there was little evidence to suggest that mass or age of mothers influenced offspring sex. Litter size, maternal mass, and maternal age all influenced cub and yearling size, but offspring sex was less important. Results suggest that female polar bears do not normally invest differentially between offspring of different sexes except in triplet litters in spring.
The male reproductive cycle of three species of Australian vespertilionid bat
Authors: Hosken D. J. , Blackberry M. A. , Stewart T. B. , Stucki A. F. 
Published: February 2006

AbstractThe male reproductive cycles of three species of vespertilionid bat (Nyctophilus geoffroyi, N. major and Vespadelus regulus) are described. Descriptions are based on the degree of testicular and cauda epididymal development estimated from field captures, and for N. geoffroyi, on histological examination of fixed specimens and assays of their testicular testosterone concentrations. All species were found to undergo a dissociated pattern of reproduction; the activity of the testes and accessory glands of reproduction were asynchronous. Spermatogenesis occurred in summer/early autumn (December–March) and testes generally regressed before mating began in autumn (March–May). Spermatozoa were stored in the cauda epididymides during the mating period. Leydig cells of N. geoffroyi involuted prior to mating but the prostate gland remained enlarged and secretory during winter (June–August), regressing in late spring (November). Testicular testosterone concentrations were greatest when Leydig cells were maximally enlarged, and concentrations were low during the mating period. The reproductive cycle of all species apparently involved asynchrony between primary and secondary sexual function, which is typical of vespertilionid bats inhabiting temperate latitudes. As mating occurs when sperm stores cannot be replenished, selection for prudent sperm allocation may be expected.
Effects of density and weather on survival of bighorn sheep lambs (Ovis canadensis)
Authors: Portier C. , Festa‐Bianchet M. , Gaillard J.‐M. , Jorgenson J. T. , Yoccoz N. G. 
Published: February 2006

AbstractDensity‐dependence in juvenile survival may be difficult to detect if survival is also affected by density‐independent factors. We investigated the relationships among weather parameters, population density, and lamb survival of bighorn sheep with long‐term data from a marked population where we manipulated population density. We distinguished neonatal survival and winter survival. Density interacted with weather variables to affect neonatal survival; spring and winter temperatures had a positive effect on neonatal survival only when population density was high. Neonatal survival was positively affected by spring precipitation independently of population density. Winter survival was positively correlated with temperature and precipitation during the previous spring, negatively correlated with density, and independent of winter temperature or snowfall. The effect of weather on lamb winter survival did not vary with density. Bighorn lambs are well adapted to harsh winter weather, but spring weather influenced survival of lambs at birth and during the subsequent winter, possibly through its effects on forage availability. Our study clearly demonstrates density‐dependence in lamb survival. Some of the effects of weather on lamb survival are density‐independent, others are mediated by an interaction with population density.
Optimal choice of foraging depth in divers
Authors: Mori Yoshihisa 
Published: February 2006

AbstractWhen prey availability depends on water depth, a diver should choose an optimal depth for foraging. A model that predicts the optimal foraging depth for a diver is presented in this paper. General predictions derived from the model are: (1) optimal foraging depth is always shallower than the depth at which prey density is the highest, even if the depth of the highest prey density is within easy reach; (2) a larger diver should make deeper and longer dives and stay longer on the surface than smaller divers for optimal foraging; (3) foraging efficiency of larger divers is not always greater than smaller divers, although the larger divers forage at the depth of higher prey density. These predictions, derived from the model, are consistent with the comparative studies of diving behaviour in marine birds.
Deferred seasonal increase in testes weight under poor nutritional conditions in a sub‐Antarctic population of rabbits (Oryctolagus cuniculus)
Authors: Boussès P. , Chapuis J.‐L. 
Published: February 2006

AbstractThe annual cycle of testes weight of adult male rabbits (Oryctolagus cuniculus) was studied in three populations on the sub‐Antarctic Kerguelen archipelago during 1984–85. This study was completed in April 1987 with an analysis of differences in diet quality between populations, assessed by the proportion of nitrogen and lignin in stomach contents. A marked annual cycle of testes weight was observed in all populations, with a rapid fall in testes weight from February to March. As in most rabbit populations studied elsewhere, testes growth resumed immediately in two populations (called Morne and Molloy). In contrast, testes growth was deferred by five to six months in the third population (Armor), subject to harsher environmental conditions. Moreover, a larger proportion of the Armor males had inactive testes during the reproductive season. The diet of the Armor population was characterized by low nitrogen and high lignin content, suggesting poor‐quality diet as an immediate cause of deferred testes growth. We propose that reduced testes size during adverse conditions might be adaptive by increasing survival probability through reduction of basal metabolism and limitation of agonistic and reproductive activities, behaviours which are costly in terms of high energetic expenditure. However, at the population level, the timing of the breeding season was not related to the cycle of male testes weight and thus seems to depend on females' condition.
A new species of Prosorhochmus (Hoplonemertea, Monostilifera) from the Chafarinas Islands (western Mediterranean)
Authors: Frutos I. , Montalvo S. , Junoy J. 
Published: February 2006

AbstractA viviparous hoplonemertean, Prosorhochmus chafarinensissp. nov., is described from the Chafarinas Islands (western Mediterranean). The species lives in the low eulittoral under the encrusting alga Lithophyllum lichenoides. Prosorhochmus chafarinensis is compared and contrasted in detail with the other valid members of the genus, P. claparedii from European waters, P. americanus from South Carolina, and P. adriatica from Italy.
The influence of molar occlusal surface area on the voluntary intake, digestion, chewing behaviour and diet selection of red deer (Cervus elaphus)
Authors: Pérez‐Barbería F. J. , Gordon I. J. 
Published: February 2006

AbstractThe loss of tooth effectiveness due to molar wear has been proposed as an important cause of mortality in ungulate populations. Voluntary intakes, digestibility, mean retention times, chewing behaviour (during eating and rumination), and diet selection (physical selection: short vs long particles in hay; and botanical selection: leaf vs stem) were compared in two groups of female red deer (Cervus elaphus) which differed in molar occlusal surface area, in order to test the hypothesis that behavioural and physiological mechanisms can be used to maintain assimilation efficiency in the presence of low functional tooth effectiveness. The group with lower values for first lower molar occlusal surface area (OSA) corrected for body weight had lower voluntary food intakes (P= 0.0126). The low OSA group had a greater number of chews per g DM of food ingested (P= 0.0167), a greater time spent chewing (P= 0.0476) but a lower number of chews per min than did those with a high OSA (P= 0.0484). The total number of chews per day was similar for both groups (P= 0.2011). The number of ruminating chews per day was less for the low OSA group (P= 0.0377). The group with low OSA values had a larger average particle size in their faeces (P= 0.0346). No differences were detected between groups in the physical or botanical composition of the diet selected (P= 0.3030, P= 0.3056, respectively) or in total digestibility and mean retention times (P= 0.1357, P= 0.3464, respectively). As a consequence of the lower voluntary intake the low OSA group had a lower digestible dry matter intake (P= 0.0170). This study supports the view that intake modification and the time invested in chewing during eating are the main mechanisms used to compensate for reduced chewing effectiveness associated with changes in tooth morphology, although the compensation is not total.
Morphological and genetic differentiation of Patella granularis (Gastropoda: Patellidae): recognition of two sibling species along the coast of southern Africa
Authors: Ridgway Tyrone M. , Stewart Barbara A. , Branch George M. , Hodgson Alan N. 
Published: February 2006

AbstractMorphological and isozyme variations between 13 populations of the species hitherto named Patella granularis were investigated to see whether differences in shell structure between the west coast versus the south and east coasts of southern Africa are supported by other morphological features or by genetic differences. The shells showed a definite decrease in size from west to east, but this is correlated with productivity and is of no diagnostic use in distinguishing between populations. Discriminant functions analysis based on shell morphometrics failed to separate populations from the three coastal regions. Shells from the northern east coast do, however, have shell nodules with a dark pigmentation, distinctly separating them from those further south and west. No differences in radular or soft part morphology were detected between the populations, but the four northernmost populations on the east coast have a significantly shorter Z looping of the gut than the other populations along the coast. Significant microstructural differences in the sperm were also detected between these two groups of populations. Electrophoretic analysis of 16 enzyme loci failed to detect any significant differences between the west and south coast populations, but revealed a genetic identity (Nei) of 0.528 as well as four diagnostic alleles between the four northernmost populations from the east coast compared with those to the south and west. The two genetically distinct forms occurred sympatrically at one of the study sites on the east coast (Coffee Bay). It was concluded the two groupings were sufficiently different to warrant the recognition of a separate species, which is centred in KwaZulu‐Natal on the east coast and extends south to Coffee Bay, from where it is replaced by P. granularis. There is, however, no evidence at all that the west coast populations are in any way separable from the remaining populations of P. granularis on the south coast.
Variation in the onset of incubation in the pied flycatcher (Ficedula hypoleuca): fitness consequences and constraints
Authors: Potti Jaime 
Published: February 2006

AbstractReproductive correlates and fitness consequences (survival, recruitment) of variation in the incubation onset of pied flycatchers (Ficedula hypoleuca) were studied across 4 years in a southern European population, where between 36 and 89% of the females started to incubate with the penultimate egg or earlier. Females started to incubate up to 3 days before completing their clutches, this being accompanied by hatching spread. Females who advanced incubation before completing the clutch tended to be in better condition and to lay larger clutches than those that postponed incubation until the clutch was complete. Although laying date had no effect on onset of incubation, the effect of clutch size was much more marked when the influence of laying date on clutch size was controlled. Females who started to incubate earlier fledged more young than females delaying incubation but their higher fledgling success was unrelated to recruitment. Females starting to incubate with the last egg had fewer fledglings but of larger size, higher mass, and in better condition than females who advanced the incubation. Female survival to the next breeding season did not differ between those that started incubation before clutch completion and those that did not do so, but an advanced onset of incubation by females was related to higher mortality of their pair mates. Females that increased the size of the clutch with respect to the previous year tended to incubate their eggs earlier, while those whose clutch size did not change or was lower started incubation at about the same stage they did the year before. This trend was apparently influenced by improvements in body condition. Clutch size may constrain onset of incubation through environmental or genetic correlations, which are likely to be mediated by hormones. It is proposed that, in this population, an early onset of incubation in pied flycatchers does not affect reproductive fitness in most circumstances.
Spatial organization of mountain gazelles Gazella gazella reintroduced to central Arabia
Authors: Dunham Kevin M. 
Published: February 2006

AbstractCaptive‐born mountain gazelles (Gazella gazella), including 28 radio‐collared and 54 tagged animals, were freed in Hawtah Reserve, Saudi Arabia, during 1991–95. The size (as minimum‐area convex polygons) and spatial distribution of their individual ranges were determined from daytime radiotracking and sightings. Some adult males were territorial and territorial fidelity was >94%. Territories were maintained year‐round and were arranged linearly along the wadi floor. Initially, the size of territories decreased as their density increased, but after density stabilized, median territory area was 0.6 km2. The ranges of up to four released females were centred on each territory and female core areas were arranged in clusters along the wadi. Female ranges became smaller as the density of territories increased. After females had dispersed, their annual range averaged about 1 km2 during both 1993 and 1994 in wadis without domestic livestock and where, consequently, plant standing crop was high. Where camels foraged and plant standing crop was low, female ranges averaged 4.6 and 1.6 km2 during these two years. Some females shifted their core area, and their annual range was twice as large. The range area of non‐territorial males averaged 6.7 km2 and extensively overlapped the ranges of other bachelors. Bachelor males occasionally passed through territories, but some wadi sections were used often by bachelors and seldom by females. The size and spatial distribution of gazelle ranges did not change seasonally, despite the temporal variation in rainfall. Runoff concentrated in wadis and the consistent food supply there allowed gazelles to occupy small ranges, even though annual rainfall was low (<150 mm).
Feeding ecology of the neotropical river otter Lontra longicaudis in an Atlantic Forest stream, south‐eastern Brazil
Authors: Pardini Renata 
Published: February 2006

AbstractThe feeding habits of the neotropical river otter Lontra longicaudis were studied in a headwater stream of the Atlantic Forest, south‐eastern Brazil, for 17 months. The otters fed mainly on fish (93% of the scats), but invertebrates were also frequent items in the diet (78.9% of the scats), as observed for the same species in lentic habitats and for other species of Lontra as well. It is suggested that the high proportion of invertebrates in the diet in comparison to Lutra is related to differences in the dentition of the two genera. The observed seasonal variation in the diet of L. longicaudis was probably a result of fluctuations in the abundance of a main prey item, a megalopteran larva (Corydalus sp.). Prey selection, regarded as differences between rates of predation and relative abundance of food items, was demonstrated for the two most important groups of otter prey: fish and crustaceans. Although they are able to capture mobile prey, otters seem to prefer feeding on prey showing lower escape ability – among fish they select armoured catfish, and among crustaceans they select crabs.
The early life of Sepia officinalis, and the contrast with that of Octopus vulgaris (Cephalopoda)
Authors: Nixon Marion , Mangold Katharina 
Published: February 2006

AbstractThe egg and hatchling of Sepia officinalis L. is relatively large, compared with those of other cephalopods. We review the information on growth, chromatophores, behaviour, prey capture, colour and body patterns of this sepiid, for correlation with changes in morphology and development of its central nervous system. We compare the early life of S. officinalis with that of the common octopod, Octopus vulgaris, Cuvier 1797. Sepia officinalis is initially benthopelagic but subsequently is mostly benthic in habit. Octopus vulgaris enters the plankton immediately after hatching and spends several weeks there before it settles to a life spent mostly on the bottom.
Reproduction and productivity of white‐lipped and collared peccaries in the Peruvian Amazon
Authors: Gottdenker Nicole , Bodmer Richard E. 
Published: February 2006

AbstractWhite‐lipped peccaries (Tayassu pecari) and collared peccaries (Tayassu tajacu) are common ungulates of Amazonia that are integral to the ecosystem and are important sources of meat for local people. Information on the reproduction and productivity of peccaries is essential for implementing management practices that conserve peccary populations over short and long time‐scales. This paper examines the reproductive biology of white‐lipped and collared peccaries in the northeastern Peruvian Amazon in and around the Tamshiyacu‐Tahuayo Community Reserve. Skulls and reproductive tracts of white‐lipped and collared peccary were examined from hunted samples collected by local people, as part of a participatory wildlife management programme. In this Amazonian site both white‐lipped and collared peccaries were in follicular and luteal stages year round. Similarly, conceptions, births and pregnancies were aseasonal for both species. Of white‐lipped peccary females, 32.4% were pregnant (n= 219 adult females examined) compared with 46% of collared peccary females (n= 89 adult females examined). Overall, gross productivity was 0.53 foetuses/adult female for white‐lipped peccaries and 0.89 foetuses/adult female for collared peccaries. Gross fecundity (number of female young produced/number of adult females) was 0.26 for white‐lipped peccaries and 0.37 for collared peccaries. The estimated parturition–conception interval was 250 days (192–331 at the 90% confidence interval) for white‐lipped peccaries and 129 days (80–205 at the 90% confidence interval) for collared peccaries. This study shows that reproductive productivity of white‐lipped peccary is lower than collared peccary in the northeastern Peruvian Amazon. This difference in reproductive productivity has implications for management strategies, and suggests that white‐lipped peccaries are more susceptible to the effects of hunting than collared peccaries.