bluuebunny/crossref_metadata_2025_split huggingface dataset:
Foraging Strategies of American White Pelicans
Authors: McMahon Blair F. , Evans Roger M. 
Published: April 2008

AbstractForaging strategies employed by American white pelicans were studied at a riverine site in Manitoba, Canada, during the breeding season in 1985 and 1986. Six strategies were identified during both diurnal and nocturnal foraging periods. Sit-and-wait was the least common strategy (four instances). Mobile individuals were common but had low rates of bill dipping and prey capture, as did relatively rare and uncoordinated aggregations. A degree of flock coordination occurred in following flocks, characterized by foragers following one after the other, with occasional synchronization of bill dipping among flock members. The largest number of pelicans foraged within more or less circular groups called nuclei. Synchronous bill dipping and apparent herding of prey towards shore were common within nuclei. The most highly coordinated strategy, semicircles, involved small numbers of foragers (2 to 30 birds) that maintained their positions relative to one another, usually in a semicircle but sometimes moving to a closed circular pattern. The greatest degree of synchronized bill dipping occurred in semicircles. Small inter-bird distances and synchronized bill dipping in nuclei and semicircles may enhance their effectiveness in driving or herding clumped fish prey. Foraging strategies could be arranged along a continuum based on degree of coordination, ranging from mobile individuals, then uncoordinated aggregations, through increasing degrees of coordination in following, nuclei, and semicircles. Along this continuum, prey size and capture rats were greatest for the more highly coordinated strategies, while less coordinated strategies appeared to be involved primarily in searching. Switching among strategies fit along the same continuum, with a tendency to switch from less to more coordinated strategies when prey were located and to return to less coordinated search when capture rates declined. Video analysis of captures within large nuclei and observations of positional shifts among foragers in nuclei and following flocks indicated that all individuals within a coordinated group potentially benefited from the presence of others, supporting the view that coordinated foraging strategies in this species are examples of true cooperative foraging. The range of strategies, and interplay among them, appear to provide the American white pelican with a highly effective group foraging system for harvesting mobile, clumped fish prey.
Effects of Primary Imprinting On the Subsequent Development of Secondary Filial Attachments in the Chick
Authors: DE VOS Gerrit J. , VAN KAMPEN Hendrik S. 
Published: April 2008

Abstract
This study reinvestigates the effects of primary imprinting of chicks with either a naturalistic stimulus or an artificial object on subsequent imprinting with artificial objects. Initial experience with a live chick (group C) or a yellow cylinder (group Y) had differential effects on the development of a secondary filial attachment in chicks. In chicks of both groups, growth of attachment to the novel imprinting object manifested itself rather abruptly, but the change in response to the novel object occurred later in C- than in Y-chicks. There was no difference between the groups in the outcome of secondary imprinting: chicks in groups C and Y eventually became equally strongly attached to their novel imprinting stimulus, and when exposed to a third object, chicks in both groups imprinted equally well on this object. Thus, (1) initial imprinting on a naturalistic stimulus postponed, but did not block secondary imprinting on an artificial object, and (2) within the lengths of exposure used, the capacity to form new filial attachments was not limited, contrary to the prediction of the competitive exclusion model for imprinting. Secondary imprinting was delayed for a longer time when chicks were exposed to the novel imprinting stimulus in an unfamiliar environment. This indicates that induction of fear in chicks interfered with the occurrence of secondary imprinting. This effect may havc contributed to the difference between groups C and Y in the length of delay of secondary imprinting. Possibly, separation from the first stimulus and exposure to the second stimulus was more fearful to C-chicks than to Y-chicks. Introduction Imprinting was originally described by LORENZ (1935, 1937) as an irreversible process. This does not necessarily mean that a young animal cannot form secondary filial attachments after having been imprinted on a
Operational Sex Ratios in Seahorses
Authors: Vincent Amanda C.J. 
Published: April 2008

AbstractContrary to all expectations based on their male pregnancy, recent work shows that seahorses exhibit conventional sex roles in mating competition: male seahorses compete more to obtain eggs than females do to give their eggs away. This suggests that the operational sex ratio (OSR: the relative number of males and females available to mate) might be male-biased despite the length and limitations of male pregnancy. I here report a study of a laboratory population of the Sri Lankan seahorse Hippocampus fuscus. The OSR amongst mated seahorses is unbiased because males and females effectively have equal reproductive rates, although some evidence suggests that a female may have limited potential for a higher reproductive rate than her partner. In contrast, the OSR among mate-seeking seahorses is male-biased, because unmated (empty) males can prepare to mate more quickly and can remain ready to mate for longer than can unmated females. Thus, the OSR is male-biased in exactly that segment of the population which should compete for mates. These findings are compatible with the sexually monogamous mating pattern of many seahorse species.
The Development of Communication in Preterm Infant-Mother Dyads
Authors: van BEEK Y. , Hopkins B. , Hoeksma J.B. 
Published: April 2008

Abstract
The present study examines the effects of gestational age and birthweight status on the development of infant and maternal behaviour as well as the (mutual) predictability between partners during face-to-face interaction at 6, 12 and 18 weeks of corrected age. Subjects are healthy fullterm infants (N = 6) and three groups of healthy preterm infants: small-for-gestational age (N = 6), and appropriate for gestational age, the latter being born after a pregnancy duration of less than 32 weeks (N = 6) or between 32 and 34 weeks (N = 6). Using dyadic sequential analyses, based on log-linear modelling and information statistics, for each individual infant-mother pair at each age, the effect of both partners on the behaviour of the other was quantified, while accounting for autocorrelational effects. In the majority of cases the interactions could be labelled as showing 'bidirectionality', particularly at 18 weeks. Mothers were more likely to be influenced by the previous behaviour of the infants than vice versa. No group differences were apparent in the way mothers were influenced by their infants. However, the small-for-gestational age preterm infants were less likely to be influenced by maternal behaviour, particularly at 6 and 12 weeks of age. A lower variability was the most common finding in infants who were not predictable from the previous behaviour of the mother. At 6 and 12 weeks they were less expressive and more often showed a monotonous behavioural pattern in which 'looking at mother's face without positive expressions' was shown during most of the interaction. As this lack of variability was more often found in SGA preterm infants, they were less predictable from their mother's behaviour than the fullterm and AGA preterm infants. These data suggest that having a low birthweight for gestational age may be a risk factor for a lack of 'bidirectionality' during early mother-infant interaction.
Female Preference for Nests With Eggs Is Based On the Presence of the Eggs Themselves
Authors: Kraak Sarah B.M. , Groothuis Ton G.G. 
Published: April 2008

Abstract
In many fish species of which males care for eggs in a nest, including Aidablennius sphynx, females prefer to mate with males that already guard eggs. In this paper we present two aquarium experiments with this Mediterranean blenny to determine whether the females actually use the presence of eggs as a cue or depend on male display behaviour signalling the presence of eggs. In experiment 1 the test-female was presented with two nests, one with eggs and one without eggs, and only one male in a closed container between the two nests. This male only served to stimulate the female. In all tests females preferred to lay eggs in the nest already containing eggs. This shows that females of this species can base their choice on the presence of the eggs alone. In experiment 2 the test-female was presented with two males in nests of which only one had eggs. Transparent partitions deprived the female of the opportunity to inspect the nest contents. The male with and the male without eggs did not differ in time spent displaying towards the female, and the female did not show a preference for either male, based on visual cues or odours. After removal of the partitions the female visited both nests. The nest she visited first was equally likely to be the nest without eggs as the nest with eggs. In contrast, the female finally deposited eggs preferentially in the nest with eggs. We conclude that in this experiment females did not base their preference for males with eggs on male behaviour, but on the nest contents after inspection. This does not exclude an influence of male behaviour under other conditions. Furthermore, females generally deposit their eggs adjacent to as many as possible of the eggs already present, suggesting that females can localize and possibly estimate the amount of eggs already present.
Can Young Chimpanzees (Pan Troglodytes) Imitate Arbitrary Actions? Hayes & Hayes (1952) Revisited
Authors: Custance Deborah M. , Whiten Andrew , Bard Kim A. 
Published: April 2008

Abstract
Contrary to recent scepticism, systematic use of an experimental approach suggested by HAYES & HAYES (1952) shows that chimpanzees can imitate novel actions. Two chimpanzees imitated 13 and 17 novel arbitrary gestures, respectively. They were first taught to reproduce 15 gestures on the command, "Do this!", and then presented with 48 novel items. Using a rigourous coding system, two independent observers correctly identified a significant number of the chimpanzees' imitations (p < 0.0001). We conclude that after a period of tuition chimpanzees can go on to imitate arbitrary actions, providing evidence of a basic cognitive capacity for perspective-taking and cross-modal matching.
Male and Female Partner Preferences in a Captive Wolf Pack (Canis Lupus) : Specificity Versus Spread of Sexual Attention
Authors: Derix Ruud R.W.M. , Van Hooff Jan A.R.A.M. 
Published: April 2008

AbstractStrong pair-bonding is typical for canids. In wolf packs consisting of several adult males and females, sexual interests may clash during the mating season. We expect that not only dominance-subordinance relationships but also partner preferences play a prominent role in the establishment of pair bonds in wolves. The objective of our study is to disentangle male and female components in the establishment of sexual relationships, and, in particular, the influence of partner preferences. A first-approach model suggests that males will attempt to maximize the number of fertilizations, whereas females will be selective in partner choice. We therefore determined behavioural measures of partner preference for each sex; namely 'Following sexually' in males and 'Presenting actively' in females. Matings corresponded more to the male than the female preferences. Males initiated courtship, whereas females influenced pair-bonding more by proceptive behaviour and by the rejection of male courtship. Whereas the dominant males focused more on one preferred female at a time, and might eventually switch and direct their preference to another female, the dominant females, and particularly the alpha female, spread their sexual interests over several males and associate with more than one male at a time. The ultimate reason for this might be that, in this way, a female promotes care-giving towards herself and her offspring by creating a 'paternity illusion' in those males.
Intraspecific Systematics of Gasterosteus Aculeatus Populations: Implications for Behavioral Ecology
Authors: Bell Michael A. 
Published: April 2008

AbstractThe threespine stickleback is widespread in diverse coastal marine and freshwater habitats of the Holarctic. Extensive information on its behavior and evolution provide an exceptional background for behavioral ecology. The behavioral phenotype links studies of proximate and ultimate (evolutionary) causes of behavior. Analyses of the ultimate causes of behavior should be placed in a phylogenetic context. There have been four phases of interpretation of phenotypic variation in threespine stickleback: (1) taxonomic, (2) dispersalist-neutralist, (3) adaptationist, and (4) adaptationist-phylogenetic. Gasterosteus aculeatus should be treated as a highly variable species complex. Phylogenetic inferences based on geographical location and allozyme and nucleotide variation facilitate discrimination between ancestry and local adaptation as ultimate causes of phenotypic variation among populations. The phylogeny of threespine stickleback populations and the use of phylogenetic information to analyze causation of pelvic girdle variation among populations are reviewed. Criteria for selection of populations and behavioral traits for comparative studies are discussed.
Role of the Three-Spined Stickleback Gasterosteus Aculeatus L. in the Food Ecology of the Spoonbill Platalea Leucorodia
Authors: Kemper Jan H. 
Published: April 2008

AbstractIn a five year study (1985-1989), the importance of the three-spined stickleback, Gasterosteus aculeatus to the spoonbill, Platalea leucorodia was elucidated. Both species migrate from distant areas to meet in polder areas as prey and predator, in the Netherlands. In the spring, spoonbills fly all the way from Afrika and the south of Spain to breed in colonies. As long as juvenile spoonbills are not able to fly, the demand for food is high, and the supply from the foraging areas is of vital importance. The availability of food in the foraging areas around one of the major spoonbill colonies was studied. Different food situations (prey items, prey density) were judged by means of the average food intake rate. Food situations in which prey items weigh over 2 gram, turned out to be most favourable. Prcy density was of less importance. Anadromous three-spined sticklebacks, migrate from the sea in the spring to breed in shallow ditches and back waters. Their body weight is about 2.5 gram which makes it an excellent prey for the spoonbill. Unfortunately, in the last decades, it has become very hard for the anadromous stickleback to migrate into polder areas. Modernisation of agriculture has led to a situation in which open connections between channels and polder area have disappeared. The presumed benefit of the anadromous stickleback for the spoonbill, was tested, by transporting 1,000 kilogram of anadromous sticklebacks to a polder area. The impact on the spoonbills was studied in a two year period. Since there was a distinct effect on the spoonbill, it was decided to design a fish ladder to enable anadromous sticklebacks to enter the polder again. The concept was tested in 1988. In 1989 a permanent construction was built.
A Causal Ethological Analysis of the Courtship Behaviour of an Insect (the Parasitic Wasp Nasonia Vitripennis, Hym., Pteromalidae)
Authors: Jachmann F. , van den ASSEM J. 
Published: April 2008

Abstract
We focus on the causal organization of courtship behaviour of an insect, i.c. that of the pteromalid wasp Nasonia vitripennis, a parasite of the pupae of various flies. We observe uninterrupted displays of male Nasonia, and analyse temporal structures in order to infer causal relations between display elements. These relations are put to a test by manipulations: displays are interrupted at pre-defined points, or re-started after pauses of various durations, or specific motor patterns are prevented from being executed. The results are summarized in Fig. 13, in which we outline the structure of the underlying organization. The main conclusion is that the performance of courtship is a self-inhibiting process in which head-nodding behaviour (a component of the display) appears to play a key role. Inhibitive effects deteriorate during pauses in between displays (in a non-linear way), but also - albeit less extensively - in periods of non-nodding, during the display itself. We discuss the issue of similar or different principles of organization in courtship behaviour of insects and vertebrates. Although a common basis cannot be excluded, we have to leave open a more definite conclusion for the time being.
Form and Function of Habituation and Sensitization of Male Courtship in the Three-Spined Stickleback (Gasterosteus Aculeatus L.)
Authors: Peeke Harman V.S. , Figler Michael H. 
Published: April 2008

Abstract
A model female stickleback presented to a territorial male with a nest usually results in the male courting the model with a series of zigzag movements followed by a leading to the nest entrance. Following such a display, a live gravid female might follow, enter the nest, spawn and leave permitting the male to fertilize the eggs. Frequently, however, the female is not ready to spawn, and the male continues to court until, at some point, he ceases courting that female at least for a short period of time and directs his attention to another female. We propose that mechanisms involved in the modulation of this behavior may include habituation and sensitization in a way that is analogous to that apparently involved in territorial aggression and predation. This study demonstrates that habituation and sensitization do influence the behavioral decrement and reinstatement respectively of male courtship of a female model, and it may be that the stickleback uses habituation as one means of curtailing courtship towards unresponsive females, thus conserving energy and permitting redeployment of attention to other, possibly more responsive, females.
Dominance, Daily Activity and Winter Survival in Willow Tits: Detrimental Cost of Long Working Hours?
Authors: Lahti Kimmo , Koivula Kari , Orell Markku 
Published: April 2008

Abstract
Predation risk can vary both in space and in time. Dawn and dusk may present greater risk to diurnal birds, since their vision is not well adapted to dimness and both nocturnal and diurnal predators may be active at these times. If the birds are not time-limited, selection should favour activity patterns where crepuscular activity is avoided. Individuals in dominance-structured groups may differ in their time-limitation. The roost-entering and emerging times of willow tits (Parus montanus) spending the winter in flocks with a social hierarchy were examined. In early winter, dominants initiated their daily activities later and roosted earlier than subordinate individuals. As a result, the duration of roosting was longer for dominants than for subordinates. By the next breeding season, significantly more subordinates than dominants had disappeared (presumably died), and the individuals which disappeared had the longest days. There were no sex differences in daily activity in early winter, but in late winter, males emerged earlier in the morning than females. A feeding experiment revealed that the birds were restricted by food availability: the fed birds reduced their roosting period less than simultaneous controls. The greater change in the controls is understandable, because the days grew longer (and the roosting period thus shorter) during the experiment. We suggest that the longest active birds were forced to extend their day in order to obtain sufficient food, which perhaps resulted in greater mortality through predation.
Artificial Visual Obstruction, Antipredator Vigilance, and Predator Detection in the Thirteen-Lined Ground Squirrel (Spermophilus Tridecemlineatus)
Authors: Arenz Cody L. , Leger Daniel W. 
Published: April 2008

AbstractAntipredator vigilance behaviour is affected by a number of variables, but studies reporting experimental manipulation of visual obstructions are generally lacking in the literature. We examined the individual antipredator behaviour of free-ranging thirteen-lined ground squirrels in 7 city parks in Lincoln, Nebraska, USA as they fed on peanut butter within small plexiglass boxes. Boxes differed in the position and amount of visual occlusion for a squirrel feeding in it: opaque, clear, opaque-sides, and opaque-top (also opaque on the end). We experimentally controlled environmental and contextual variables that have been identified as affecting vigilance behaviour. We filmed 38 ground squirrels as they fed in the boxes, and the results indicate that ground squirrels treat lateral occlusion as functionally identical to complete occlusion. Additionally, there were no significant differences in the squirrels' behaviours in the clear versus the opaque-top box. In 35 approach tests, a person walked toward individual ground squirrels as they foraged in one of the 4 box types. The distance at which the squirrels reacted did not differ among the 4 box types. The results of these two experiments suggest that thirteen-lined ground squirrels compensate for visual occlusion, primarily through increased withdrawals coupled with low-level vigilance postures and that the position of visual occlusion can be of greater importance than the absolute amount of occlusion.
The Larval Development of a Fresh-Water Prawn, Palaemonetes Zariquieyi Sollaud, 1939 (Decapoda, Palaemonidae), Reared in the Laboratory
Authors: Guerao G. 
Published: April 2008

AbstractThe larval development of the fresh-water prawn Palaemonetes zariquieyi Sollaud, 1939 is described and illustrated in detail. Egg and larval sizes are given. Three larval and one postlarval stages are distinguished, and their characteristics are compared with those of Palaemonetes species.
Aquaria Experiments On Habitat Choice of Littoral Shrimps of the Faroe Islands
Authors: Berggren Matz 
Published: April 2008

AbstractAn experiment was performed in habitat choice of littoral shrimps from the Faroe Islands. All shrimps were collected in the algal zone, where they have different choice of habitat. This experiment shows that some species of shrimps have a very significant habitat choice under light conditions (Eualus gaimardii, Hippolyte varians and Lebbeus polaris). Between Hippolyte varians and Eualus pusiolus, competition in habitat selection may take place among 'Leaf-like' red algae. During dark most shrimps move around and do not stay at any specific habitat.
Biometry of Decapod Crustaceans in the Cantabrian Sea
Authors: Rodríguez-Marín Enrique 
Published: April 2008

AbstractIn this paper the biometric relationships between the different body parts of decapods are described, allowing the reconstruction of size and biomass (weight) of each sample from its hard parts (chelae and cephalothorax). The usefulness of this study lies in the interpretation of the feeding habits of demersal fish which feed on decapod crustaceans, since the slow digestion of hard skeletons of Decapods gives rise to the appearance of numerous hard parts in fish stomach contents.