bluuebunny/crossref_metadata_2025_split huggingface dataset:
Is there any interspecific competition between dwarf crocodiles (Osteolaemus tetraspis) and Nile monitors (Varanus niloticus ornatus) in the swamps of central Africa? A study from south‐eastern Nigeria
Authors: Luiselli L. , Akani G. C. , Capizzi D. 
Published: February 2006

AbstractAspects of coexistence between the dwarf crocodile Osteolaemus tetraspis and the Nile monitor lizard Varanus niloticus were studied in swamp rain forests of south‐eastern Nigeria, central Africa. Crocodiles were significantly smaller than monitor lizards. There was no significant sexual size dimorphism in the examined sample of Varanus, whereas the female size exceeded the male size in Osteolaemus. The food niche breadth was narrower in young than in adults of both species, and V. niloticus showed a narrower niche breadth than O. tetraspis. Crabs constituted the main prey type category for both species, whereas vertebrates were more rarely preyed upon. The diet composition of males and females was similar in V. niloticus, but it was different in O. tetraspis. The general diet composition of the two species was similar (78.2% of overlap), and even the habitats where these two species were found were similar. These interspecific similarities suggest that O. tetraspis and V. niloticus could be potential competitors in the freshwater ecosystems of the Nigerian rainforest. However, it is suggested that the main prey type for these species (crabs) is not limited in the environment, which may minimize interspecific competition. Interference competition can also occur between these species, as suggested by one case of direct predation of the one species (V. niloticus) towards the other species (O. tetraspis). A case of cannibalism was observed in V. niloticus. This could indicate that intraspecific competition can be important for regulating the dynamics of monitor populations in the rainforests of south‐eastern Nigeria.
Decalcification of vulvar operculum and mating in the ocypodid crab Ilyoplax pusilla
Authors: Henmi Y. , Murai M. 
Published: February 2006

AbstractIn the mating system of Ilyoplax pusilla, wandering females respond to courting, burrow‐holding males that wave their chelipeds and enter their burrows. They pair in plugged burrows where mating occurs. Female I. pusilla spawned within 3 days of pairing, after which the male left. The opercula of females became decalcified, before, or more often after, pairing. Decalcification normally follows responsiveness to male courtship, but it is not necessary to produce female receptive behaviour, and pairing with a male in his burrow is not essential to evoke decalcification. After spawning, the numbers of calcified females gradually increased, and most ovigerous females were recalcified before larval release. The percentage of decalcified, single, non‐ovigerous females in the population peaked near the full and new moons. The peak percentage of decalcified, non‐ovigerous, paired females occurred 2 days later than that of decalcified, single, non‐ovigerous females. Decalcified females did not always enter male burrows for mating. Some females remained in their own burrows and laid eggs fertilized with stored sperm. Spawning with stored sperm may be an adaptation to avoid the risk of predation and it enables females, not evicted by neighbouring males, to reproduce.
Variation in spermathecal morphology and amount of sperm stored in populations of the simultaneously hermaphroditic land snail Arianta arbustorum
Authors: Baminger Helmut , Haase Martin 
Published: February 2006

AbstractThe morphology of the sperm storage organ (spermatheca) may influence the outcome of sperm competition in a variety of invertebrate species. Simultaneously hermaphroditic pulmonates show considerable inter‐ and intraspecific variation in the structure of the spermatheca. The morphological variation in the spermatheca (number of spermathecal tubules and tubule length) and the amount of sperm stored in the tubules in 115 individuals of the simultaneously hermaphroditic land snail Arianta arbustorum (L.) from six natural populations in the Eastern Alps (Gesäuse, Austria) was examined. The populations differed in snail density, therefore in the number of potential mating partners (range: 0.9–39.8 individuals/m2) and thus in the sperm competition risk. The number of spermathecal tubules ranged from two to nine. However, the six populations did not differ in either the mean number of spermathecal tubules, the length of the main tubule (range 0.9–3.4 mm), or in the cumulative length of the tubules (range 1.5–7.8 mm). The number of tubules and tubule length were not correlated with either shell height and shell breadth or with population density. The amount of sperm stored in the spermathecal tubules was estimated. Individuals from different populations did not differ in the amount of sperm stored, and the amount of sperm stored was not correlated with population density. Results indicate that the risk of sperm competition does not affect the complexity of the spermatheca (number of spermathecal tubules) in this snail. However, the possibility that individuals in high‐density populations store sperm from more different mating partners than those in low‐density populations remains to be examined.
The effect of parental age and experimentally manipulated brood size on the foraging effort and breeding performance of great skuas (Catharacta skua)
Authors: Ratcliffe N. , Furness R. W. 
Published: February 2006

AbstractWe examined the effect of a brood‐size manipulation on the foraging effort and chick rearing of known‐age great skuas Catharacta skua. Young birds were expected to refrain from increasing reproductive effort and opt for a strategy of brood reduction, while old birds were expected to increase effort and rear more young. Increasing brood size led to an increase in foraging effort and brood neglect. Enlarged broods had a lower mean survival rate, but similar growth rates to one‐ and two‐chick broods. Parents increased foraging effort to maintain chick growth rates at the expense of brood defence. This was associated with higher conspecific predation of enlarged broods. Foraging effort and chick feeding rate decreased with adult age. Younger adults increased foraging time in an attempt to satisfy the nutritional demands of the chicks, while older birds maintained a similar effort for all brood sizes. Younger adults achieved a lower fledging success despite their higher provisioning rates. Younger birds synchronized foraging and guarding duties less well, and so left the chicks unattended more often than older birds. As a consequence, their chicks suffered higher levels of conspecific predation. Defence of chicks through pair co‐ordination and aggression was thus an important component of successful breeding for great skuas.
Demography and population dynamics of the lacertid lizard Podarcis bocagei in north‐west Spain
Authors: Galán Pedro 
Published: February 2006

AbstractThe demography and life‐history traits of a population of the lacertid lizard Podarcis bocagei in north‐west Spain were investigated. Most of the conclusions presented are based on mark–recapture studies carried out over a 2‐year period. Reproductive characteristics are similar to those reported for other temperate‐climate lacertids. Clutch size, egg size and hatchling size (snout–vent length, SVL) are all positively correlated with the mother's SVL. Only large females lay more than one clutch per year. Growth rate is highest in young animals and declines gradually with age. In both sexes, sexual maturity is reached between the ages of 1 and 2 years. Again in both sexes, the probability of survival was fairly constant over the lifespan. Considering the study period as a whole, there was no significant between‐sex difference in survival probability. Among adults, the probability of survival was higher in winter than during other periods, but the differences were not statistically significant. The individuals of the study population are sedentary, making only short movements even when periods of up to 2 years are considered (the mean distance moved between marking and recapturing 18–24 months later was 15.7 m, maximum 45.6 m). On average, immature individuals move further than adults, and adult males move further than adult females. Estimated population density (all individuals) dropped from 1574 ha‐1 during the winter of 1989/90 to 1327 ha‐1 during the winter of 1990/91. The decline in population density over the study period was also reflected in the estimated net replacement rate for the population (0.85, i.e. considerably less than one), and is probably attributable to colonization of the study site by plants (reducing suitability as a habitat for P. bocagei). Estimated mean generation time was 2.09 years.
The proboscis of tapirs (Mammalia: Perissodactyla): a case study in novel narial anatomy
Authors: Witmer Lawrence M. , Sampson Scott D. , Solounias Nikos 
Published: February 2006

AbstractThe trunk‐like proboscis of tapirs provides a prime case study in the evolution of anatomical novelty. Morphological study of this unique structure was undertaken employing several specimens and a combination of analytical techniques: gross anatomical dissection, radiographic imaging and histological sectioning. Evolution of the proboscis of tapirs entailed wholesale transformation of the narial apparatus and facial architecture relative to perissodactyl outgroups. This transformation involved retraction and reduction of the bony and cartilaginous facial skeleton, such that several structures present in outgroups are completely absent in tapirs, including cartilages surrounding the nasal vestibule (e.g. alar and medial accessory cartilages, rostral portion of the nasal septum) and associated musculature (dilatator naris apicalis, lateralis nasi pars ventralis). At the same time, soft tissues surrounding the upper lip and nose became elaborated to form a mobile, fleshy proboscis. Several key facial muscles (e.g. levator labii superioris, levator nasolabialis, caninus, lateralis nasi) have been co‐opted to function in movement of the proboscis. The nasal vestibule is expanded and occupies approximately 75% of the nasal cavity. Vestibular expansion has compressed and simplified caudal components of the nasal cavity (e.g. reduction of dorsal and middle nasal conchae, loss of plica recta and plica basalis). The airway has become dorsally arched causing the ventral conchal complex to become inclined relative to the long axis of the skull. A few anatomical enigmas remain, such as the complicated maxilloturbinate that rostrally contacts the nasal septum and vomeronasal organ. Similarly, the meatal diverticulum, despite being both ancient and anatomically complex, has no obvious functional significance; it is clear that it is not homologous to the nasal diverticulum of horses and other equids. The reduction of the osseocartilaginous portion of the proboscis, coupled with expansion of the muscular and connective tissue components, has resulted in an organ that is best interpreted as a muscular hydrostat.
Group dynamics of humpback dolphins (Sousa chinensis) in the Algoa Bay region, South Africa
Authors: Karczmarski Leszek 
Published: February 2006

AbstractGroup dynamics of humpback dolphins Sousa chinensis inhabiting the Algoa Bay region on the south Eastern Cape coast of South Africa, were investigated by means of boat‐based photo‐identification surveys undertaken between May 1991 and May 1994. Groups of humpback dolphins varied in size from three to 24 animals (x̄= seven), with adults representing almost two‐thirds of the group members. Births occurred predominantly in summer. Some females, however, may also cycle outside of the apparent summer breeding season, perhaps indicating a secondary winter season. Circumstantial evidence suggests a minimum of a 3‐year calving interval. Maternal care lasts at least 3–4 years, but female–calf separation is seemingly not related to the female's next pregnancy. Humpback dolphins displayed varying degrees of residence/fidelity to Algoa Bay. Although a few individuals may possibly be classified as ‘resident’, most dolphins were infrequent visitors in the Bay and seem to be transient. The social system of humpback dolphins appears to be fluid with only casual and short‐lasting affiliations. Strong bonds between individuals other than mothers and calves are uncommon. Lack of consistency in the group membership appears to be the general pattern. The weak site fidelity and possibly extensive long‐range movement of the majority of dolphins may contribute to the dynamic nature of humpback dolphin groups. There is probably some form of segregation between sex and/or age classes among humpback dolphins in Eastern Cape waters. The nature and extent of this segregation, however, is not yet sufficiently understood. It is likely that the degree of site fidelity displayed by female humpback dolphins is related to their reproductive stage and increases during the nursing period. Mate‐searching behaviour of male humpback dolphins is the most likely reproductive strategy of the species.
Phylogenetic and taxonomical relationships of the eight species in the melanogaster subgroup of the genus Drosophila (Sophophora) based on the electrophoretic mobility of the major chorion proteins and the eggshell ultrastructure
Authors: Kalantzi‐Makri Maria C. , Trougakos Ioannis P. , Tafas Triantafyllos P. , Sourdis John , Margaritis Lukas H. 
Published: February 2006

AbstractThe eight species of the melanogaster species subgroup of the genus Drosophila were compared to each other with respect to: (a) the electrophoretic mobility of the major chorion proteins under SDS–PAGE; (b) the overall eggshell ultrastructure. The phylogenetic tree obtained using the first criterion showed that the eight species are divided into three clusters that contain the species of the melanogaster complex (D. melanogaster, D. sechellia, D. mauritiana and D. simulans), the two species of the yakuba complex (D. yakuba and D. teissieri) and the erecta complex species (D. erecta and D. orena). This clustering is in agreement to the generally accepted phylogeny of the subgroup based on exclusive criteria. The eggshell ultrastructure of the species at the main body of the egg revealed that the phylogenetically closely related species exhibit similar eggshell structure. We conclude that the criteria applied in this study could be eventually used in groups with unknown phylogeny to trace the phylogenetic relationships of the species.
Dry season camps of flying‐foxes (Pteropus spp.) in Kakadu World Heritage Area, north Australia
Authors: Tidemann Christopher R. , Vardon Michael J. , Loughland Ronald A. , Brocklehurst Peter J. 
Published: February 2006

AbstractWe investigated camps of black Pteropus alecto and red flying‐fox P. scapulatus in the early dry season of 1992 (April–June) in Kakadu National Park, a World Heritage Area in the wet‐dry tropics of north Australia. Fifteen camp‐sites were located and two types of camps were defined: main camps containing > 1000 animals and a significant component of young (P. alecto, n= 4; P. scapulatus, n= 2) and satellite camps of lesser size (P. alecto, n= 9; P. scapulatus, n= 3). The two species shared three camp‐sites. All camps were in dense riparian vegetation (fresh and saltwater mangroves, paperbark forests, closed forest and bamboo), overhanging or adjacent to water inhabited by crocodiles, that would provide a protected microclimate and protection from predators. All camps were within 5 km or less of one or more unoccupied sites that were indistinguishable in landform or vegetation from camp‐sites. In Kakadu NP riparian vegetation makes up about 6% of the park and is a non‐limiting resource for flying‐fox roosting. We propose that the initial colonization of camp‐sites is essentially random when roost vegetation is non‐limiting and that factors such as predation by humans, cyclones and fires determine the persistence and size of camps at the local level. At a broader temporal and spatial scale, interaction between the seasonal availability of forage and reproductive cycles is known to influence the location, size and structure of Pteropus camps. We advance the hypothesis that colonies of flying‐foxes could be moved to new camp‐sites, a strategy that would facilitate resolution of the frequently problematic management of these animals.
Courtship and mating in Empis (Xanthempis) trigramma Meig., E. tessellata F. and E. (Polyblepharis) opaca F. (Diptera: Empididae) and the possible implications of ‘cheating’ behaviour
Authors: Preston‐Mafham Kenneth G. 
Published: February 2006

AbstractThe courtship and mating behaviour of three empidid flies Empis trigramma, E. tessellata and E. opaca are described. In E. trigramma the male appears to use his complex genitalia to introduce a liquid ‘gift’ into the female's abdomen during copulation. This ‘gift’ is subsequently discharged and imbibed by the female. Such male ‘gifts’ may constitute a direct investment in their offspring, as females do not seem to acquire significant nutritional input from other sources. Males of E. opaca and E. tessellata present a ‘gift’ to the female, in the form of a dead insect, before mating takes place. Females will not mate with males which do not present a gift. Gifts presented during the period of sexual activity also appear to make a substantial contribution to female ovarian development. Some males seek to ‘cheat’ by presenting substitute gifts in the form of the fluff‐bearing seeds of willows. In E. opaca such ‘cheats’ enjoyed a low rate of reproductive success, compared with males presenting food gifts. ‘Cheating’ appears to be an alternative mating tactic for males of this species.
Parental and predatory behaviour of Scytodes sp., an araneophagic spitting spider (Araneae: Scytodidae) from the Philippines
Authors: Li Daiqin , Jackson Robert R. , Barrion Alberto T. 
Published: February 2006

AbstractParental care, especially as it relates to our understanding of sociality, is a topic that has received considerable recent attention in research on spiders (Aviles, 1997). Predatory strategies, including foraging decisions, prey preferences and predatory versatility, have also been emphasized in the recent literature. The present paper is concerned with both of these areas, parental care and predatory strategies. Scytodes sp. indet. is a versatile predator that captures prey either in its web or away from webs, and prey capture may be either by ambush or by active pursuit regardless of whether in the presence and absence of webs. The web is a sparsely woven sheet across a concave upper leaf surface, with a three‐dimensional tubular nest linked to the sheet via a small opening. Leaves may be green and living or brown and dead. In the field, a wide range of insects and spiders is taken, but jumping spiders (Salticidae) are the dominant prey. Predatory attacks are by spitting, with large prey being spat at repeatedly before being subdued. After spitting, the scytodid wraps prey in silk before feeding. Eggs are enclosed in a silk egg sac. The female uses her chelicerae to hold her eggs until hatching. After hatching, there is an extended mother–offspring association, with juveniles tending to remain in their mother's web until after the third moult. Females take prey to their juveniles and either feed alongside the juveniles or leave the juveniles to feed alone.
Demography, sociospatial behaviour and genetics of feral pigs (Sus scrofa) in a semi‐arid environment
Authors: Gabor Timothy M. , Hellgren Eric C. , Van Den Bussche Ronald A. , Silvy Nova J. 
Published: February 2006

AbstractWe examined demographics, dispersal, sex‐related behaviour, group structure, and genetic similarities of female feral pigs Sus scrofa on the Chaparral Wildlife Management Area in southern Texas from June 1993 to December 1995. Cumulative and seasonal ranges and core areas were calculated for 18 female pigs representing three distinct sounders. Simultaneous pairs of radio locations were used to assess behavioural associations among pigs, and DNA fingerprinting was used to determine genetic similarity. Behavioural and spatial associations largely corresponded to genetic relationships. Similarity of behavioural dendrograms to genetic dendrograms indicated that genetic relationships of feral pigs played a role in observed population structure. A single discrepancy between genetic and behavioural dendrograms suggested two animals dispersed to an adjacent sounder. Also, one sounder appeared to have been created by fission from a larger, adjacent sounder. Factors that are important keys in understanding the association between genetics and behaviour of feral pigs include dispersal, climate, habitat quality, population densities, and sex‐related behaviour.
Scaling of mammalian long bones: small and large mammals compared
Authors: Christiansen Per 
Published: February 2006

AbstractLong bones from a taxonomically diverse assemblage of extant terrestrial mammals, spanning more than three orders of magnitude in body mass, have been measured in order to evaluate earlier models proposed for limb allometry as a means of physically coping with increased body size in large species. Linear regression models are unable to explain long bone scaling across a large size range of mammals, as differential scaling is present in large and small species and smaller species tend to approach geometric similarity to a considerably greater extent than larger species. Attempting to explain the morphology of the appendicular skeleton across the large size range of terrestrial Mammalia by means of a standard power function will probably inevitably lead to oversimplification, concealing underlying adaptations for coping with increased size. These include differences in limb posture, decrease in locomotory potential and greater duty factors during fast locomotion in large animals compared to anatomically similar smaller forms, and differential scaling of the appendicular skeleton in small and large mammals.
The distribution of play behaviour among Australian marsupials
Authors: Byers John A. 
Published: February 2006

AbstractThe distribution of play behaviour among the Australian marsupial families was surveyed. The rate of play in each species observed was categorized on a three‐point scale: 1 – no play observed or reported; 2 – play rudimentary; 3 – play common. Common play occurred in the larger‐bodied Dasyuridae, in Myrmecobiius, in Vombatidae, and in all Macropodoidea. In all other marsupials, play was rudimentary or absent. Categorical rate of play was not correlated with body mass or with metabolic rate but was correlated with relative brain mass. The distribution of play in Australian marsupials supported the hypothesis that play acts to modify brain development.