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Conspecifics
Kinds of Conspecifics Terms modified by Conspecifics Selected AbstractsFASTER FERTILIZATION RATE IN CONSPECIFIC VERSUS HETEROSPECIFIC MATINGS IN HOUSE MICEEVOLUTION, Issue 1 2009Matthew D. Dean Barriers to gene flow can arise at any stage in the reproductive sequence. Most studies of reproductive isolation focus on premating or postzygotic phenotypes, leaving the importance of differences in fertilization rate overlooked. Two closely related species of house mice, Mus domesticus and M. musculus, form a narrow hybrid zone in Europe, suggesting that one or more isolating factors operate in the face of ongoing gene flow. Here, we test for differences in fertilization rate using laboratory matings as well as in vitro sperm competition assays. In noncompetitive matings, we show that fertilization occurs significantly faster in conspecific versus heterospecific matings and that this difference arises after mating and before zygotes form. To further explore the mechanisms underlying this conspecific advantage, we used competitive in vitro assays to isolate gamete interactions. Surprisingly, we discovered that M. musculus sperm consistently outcompeted M. domesticus sperm regardless of which species donated ova. These results suggest that in vivo fertilization rate is mediated by interactions between sperm, the internal female environment, and/or contributions from male seminal fluid. We discuss the implications of faster conspecific fertilization in terms of reproductive isolation among these two naturally hybridizing species. [source] Developmental experience alters information coding in auditory midbrain and forebrain neuronsDEVELOPMENTAL NEUROBIOLOGY, Issue 4 2010Sarah M.N. Woolley Abstract In songbirds, species identity and developmental experience shape vocal behavior and behavioral responses to vocalizations. The interaction of species identity and developmental experience may also shape the coding properties of sensory neurons. We tested whether responses of auditory midbrain and forebrain neurons to songs differed between species and between groups of conspecific birds with different developmental exposure to song. We also compared responses of individual neurons to conspecific and heterospecific songs. Zebra and Bengalese finches that were raised and tutored by conspecific birds, and zebra finches that were cross-tutored by Bengalese finches were studied. Single-unit responses to zebra and Bengalese finch songs were recorded and analyzed by calculating mutual information (MI), response reliability, mean spike rate, fluctuations in time-varying spike rate, distributions of time-varying spike rates, and neural discrimination of individual songs. MI quantifies a response's capacity to encode information about a stimulus. In midbrain and forebrain neurons, MI was significantly higher in normal zebra finch neurons than in Bengalese finch and cross-tutored zebra finch neurons, but not between Bengalese finch and cross-tutored zebra finch neurons. Information rate differences were largely due to spike rate differences. MI did not differ between responses to conspecific and heterospecific songs. Therefore, neurons from normal zebra finches encoded more information about songs than did neurons from other birds, but conspecific and heterospecific songs were encoded equally. Neural discrimination of songs and MI were highly correlated. Results demonstrate that developmental exposure to vocalizations shapes the information coding properties of songbird auditory neurons. © 2009 Wiley Periodicals, Inc. Develop Neurobiol 70: 235,252, 2010. [source] The hippocampus and caudomedial neostriatum show selective responsiveness to conspecific song in the female zebra finchDEVELOPMENTAL NEUROBIOLOGY, Issue 1 2002David J. Bailey Abstract The perception of song is vital to the reproductive success of both male and female songbirds. Several neural structures underlying this perception have been identified by examining expression of immediate early genes (IEGs) following the presentation of conspecific or heterospecific song. In the few avian species investigated, areas outside of the circuit for song production contain neurons that are active following song presentation, specifically the caudal hyperstriatum ventrale (cHV) and caudomedial neostriatum (NCM). While studied in detail in the male zebra finch, IEG responses in these neural substrates involved in song perception have not been quantified in females. Therefore, adult female zebra finches were presented with zebra finch song, nonzebra finch song, randomly generated tones, or silence for 30 min. One hour later they were sacrificed, and their brains removed, sectioned, and immunocytochemically processed for FOS expression. Animals exposed to zebra finch song had a significantly higher density of FOS-immunoreactive cells in the NCM than those presented with other songs, tones, or silence. Neuronal activation in the cHV was equivalent in birds that heard zebra finch and non-zebra finch song, expression that was higher than that observed in the groups that heard no song. Interestingly, the hippocampus (HP) and adjacent parahippocampal area (AHP) were activated in a manner comparable to the NCM. These results suggest a general role for the cHV in song perception and a more specific role for the NCM and HP/AHP in facilitating recognition of and responsiveness to species-specific song in female zebra finches. © 2002 Wiley Periodicals, Inc. J Neurobiol 52: 43,51, 2002 [source] In uniparental Phodopus sungorus, new mothers, and fathers present during the birth of their offspring, are the only hamsters that readily consume fresh placentaDEVELOPMENTAL PSYCHOBIOLOGY, Issue 7 2006Jennifer K. Gregg Abstract Placentophagia is common among parturient female mammals but non-parturient females generally refuse placenta. Biparental male dwarf hamsters (Phodopus campbelli) readily consume placenta. The present study quantified placentophagia and liver acceptance in the closely related Siberian hamster P. sungorus in which males do not participate in the birth and are not responsive to a displaced pup. Sexually naïve P. sungorus males and females refused both placenta and liver (all groups <10%). Reproductive females specifically consumed placenta on the day before (G17), and the day of, parturition (G18) (>80%). Males rejected both tissues on G17 and accepted placenta soon after the birth (G18) (80%) only if they were present during the birth. Palatability of the placenta was not responsible for the species difference as P. campbelli accepted P. sungorus placenta. Results are consistent with a neophobic reaction to both placenta (conspecific or heterospecific) and liver as P. sungorus also rejected P. campbelli placenta. © 2006 Wiley Periodicals, Inc. Dev Psychobiol 48: 528,536, 2006. [source] Maternal and littermate deprivation disrupts maternal behavior and social-learning of food preference in adulthood: Tactile stimulation, nest odor, and social rearing prevent these effectsDEVELOPMENTAL PSYCHOBIOLOGY, Issue 3 2006Angel I. Melo Abstract Maternal and littermate (social) separation, through artificial rearing (AR), disrupts the development of subsequent maternal behavior and social learning in rats. The addition of maternal-licking-like stimulation during AR, partially reverses some of these effects. However, little is know about the role of social stimuli from littermates and nest odors during the preweaning period, in the development of the adult maternal behavior and social learning. The purpose of this study was to examine the effects of peer- and peer-and-odor rearing on the development of maternal behavior and social learning in rats. Female pups were reared with mothers (mother reared,MR) or without mothers (AR) from postnatal day (PND) 3. AR rats received three different treatments: (1) AR-CONTROL group received minimal tactile stimulation, (2) AR-ODOR females received exposure to maternal nest material inside the AR-isolation-cup environment, (3) AR-SOCIAL group was reared in the cup with maternal nest material and a conspecific of the same-age and same-sex and received additional tactile stimulation. MR females were reared by their mothers in the nest and with conspecifics. In adulthood, rats were tested for maternal behavior towards their own pups and in a social learning task. Results confirm our previous report that AR impairs performance of maternal behavior and the development of a social food preference. Furthermore, social cues from a littermate, in combination with tactile stimulation and the nest odor, reversed the negative effects of complete isolation (AR-CONTROL) on some of the above behaviors. Exposure to the odor alone also had effects on some of these olfactory-mediated behaviors. These studies indicate that social stimulation from littermates during the preweaning period, in combination with odor from the nest and tactile stimulation, contributes to the development of affiliative behaviors. © 2006 Wiley Periodicals, Inc. Dev Psyshobiol 48: 209,219, 2006. [source] Complete maternal deprivation affects social, but not spatial, learning in adult ratsDEVELOPMENTAL PSYCHOBIOLOGY, Issue 3 2003F. Lévy Abstract The effects of maternal deprivation on learning of social and spatial tasks were investigated in female adult rats. Pups were reared artificially and received "lickinglike" tactile stimulation (AR animals) or were reared with their mothers (MR animals). In adulthood, subjects were tested on paradigms of spatial learning and on paradigms involving learning of social cues. Results showed that maternal deprivation did not affect performance on spatial learning, but it did impair performance on the three social learning tasks. The AR animals made no distinction between a new and a previously presented juvenile conspecific. AR animals also responded less rapidly than MR animals at test for maternal behavior 2 weeks after a postpartum experience with pups. Finally, AR animals did not develop a preference for a food previously eaten by a familiar conspecific whereas MR animals did. This study indicates that animals reared without mother and siblings show no deficits in spatial tasks while showing consistent deficits in learning involving social interactions. © 2003 Wiley Periodicals, Inc. Dev Psychobiol 43: 177,191, 2003. [source] Maternally separated rats show deficits in maternal care in adulthoodDEVELOPMENTAL PSYCHOBIOLOGY, Issue 1 2001Vedran Lovic Abstract Although there is considerable research on the phenomenology, neuroendocrinology, neuroanatomy, and sensory control of maternal behavior, little is known about the influences of early postnatal and postweaning experiences on the development of maternal behavior. The purpose of this study was to assess how early life separation from the mother rat affects development of the offspring's juvenile and adult maternal behavior. From postnatal Days 1 to 17, 3 female rats within each litter were separated (SEP) from the mother and the rest of the litter for 5 hr daily while 3 of their sisters were not maternally separated (NSEP). On postnatal Day 21, all subjects were weaned and randomly assigned to one of three juvenile conditions. One female from both SEP and NSEP groups was either isolated (I), given a social conspecific (S), or given 1- to 4-day-old pups (P) for 5 consecutive days. Maternal behavior of SEP and NSEP animals was assessed and recorded on each of the 5 days. Once all animals reached adulthood, they were mated, gave birth, and were assessed for their maternal behavior. We found that the effects of maternal separation on juvenile maternal-like behaviors were minimal. On the other hand, maternal separation reduced adult maternal licking and crouching over pups. In addition, there was a significant interaction between postnatal and juvenile experience on maternal crouching in maternal animals. These results are discussed in terms of the variety of possible behavioral, endocrine, and neurochemical mechanisms that mediate the effects of early life experiences on adult maternal behavior. © 2001 John Wiley & Sons, Inc. Dev Psychobiol 39: 19,33, 2001 [source] A morphological reappraisal of Tubifex blanchardi Vejdovský, 1891 (Clitellata: Tubificidae)ACTA ZOOLOGICA, Issue 2 2009Roberto Marotta Abstract Tubifex blanchardi Vejdovský, 1891 is a freshwater tubificid, often living in sympatry with Tubifex tubifex (Müller 1774). Although considered from its discovery as a species on its own, its biological status is debated. During the early seventies T. blanchardi was reduced to a mere form of T. tubifex, as a particular case of polymorphism in chaetal pattern. Using classical histological techniques, microdissections of portions of the male genital apparatus and phalloidin staining of dissected copulatory organs we investigated 163 mixed individuals of T. blanchardi and T. tubifex belonging to sympatric populations from the Lambro River (Milan, Northern Italy). The internal morphology of T. blanchardi is described for the first time. Our results show that T. tubifex and T. blanchardi differ in several characters concerning both their external and internal morphology, and in the fine organization of their copulatory organs. Several independent character sets support the separation of T. blanchardi from T. tubifex, suggesting that it is an independent species. This study also supports the idea that T. blanchardi and T. bergi (Hrab,, 1935), another species closely related to T. tubifex, are not conspecific. The observed morphological differences between allopatric populations of T. tubifex are discussed. [source] Neighbour-regulated mortality: the influence of positive and negative density dependence on tree populations in species-rich tropical forestsECOLOGY LETTERS, Issue 8 2003Halton A. Peters Abstract Density-dependent mortality has long been posited as a possible mechanism for the regulation of tropical forest tree density. Despite numerous experimental and phenomenological investigations, the extent to which such mechanisms operate in tropical forests remains unresolved because the demographical signature of density dependence has rarely been found in extensive investigations of established trees. This study used an individual-based demographical approach to investigate the role of conspecific and heterospecific neighbourhood crowding on tree mortality in a Panamanian and a Malayan tropical forest. More than 80% of the species investigated at each site were found to exhibit density-dependent mortality. Furthermore, most of these species showed patterns of mortality consistent with the Janzen,Connell hypothesis and the rarely explored hypothesis of species herd protection. This study presents some of the first evidence of species herd protection operating in tree communities. [source] Behaviourally structured populations persist longer under harsh environmental conditionsECOLOGY LETTERS, Issue 5 2003Sergei V. Petrovskii Abstract The factors and mechanisms that enhance population persistence in a fragmented habitat and/or under harsh environmental conditions are of significant current interest. We consider the dynamics of a population in an isolated habitat surrounded by an unfavourable environment subject to different behavioural responses between the individuals. We assume that there are two responses available: one of them is aggression in its extreme form, the other is its contrary when an individual takes flight in order to avoid any contact with its conspecific. We show that a behaviourally structured population consisting of individuals with fixed behavioural responses is intrinsically less prone to extinction under harsh environmental condition than a population where the individuals can ,choose' between the two given behaviours. We also show that, contrary to an intuitively expected negative impact of aggression on population persistence, the optimal conditions for population persistence are reached when a considerable proportion of the individuals exhibit aggressive behaviour. [source] Brood size reduction in Nicrophorus vespilloides after usurpation of carrion from Nicrophorus quadripunctatus (Coleoptera: Silphidae)ENTOMOLOGICAL SCIENCE, Issue 3 2004Seizi SUZUKI Abstract Burying beetles bury small vertebrate carcasses, which become food for their larvae. They sometimes usurp carcasses occupied and buried by other beetles. Brood sizes of intraspecific and interspecific intruders were examined using Nicrophorus quadripunctatus as the resident. The brood sizes of usurpers were not reduced relative to control brood sizes when the usurper was conspecific, but were reduced when the usurper was heterospecific (N. vespilloides). [source] Biting Behavior, Aggression, and SeizuresEPILEPSIA, Issue 5 2005Carlo Alberto Tassinari Summary:,Purpose: To describe the semiologic features of aggressive behaviors observed in human epileptic seizures with particular reference to the act of biting a conspecific. Methods: We analyzed the biting behavior (BB) and other aggressive gestures occurring in a group of 11 patients retrospectively selected from >1,000 patients subjected to video-EEG/SEEG monitoring for presurgical evaluation of drug-resistant seizures. Results: Patients displaying BB showed (a) a male sex predominance, (b) heterogeneous etiologies and lesion locations, and (c) seizures involving the frontotemporal regions of both hemispheres. The act of biting was a rapid motor action, lasting ,600 ms, occurring in the context of strong emotional arousal, fear, and anger, with various bodily gestures with aggressive connotation. BB was mainly a "reflexive" behavior, in that biting acts were evoked (both during and after seizures) by actions of people in close contact with the patient. The sole intrusion of the examiner's hand in the space near the patient's face was effective in triggering BB. Rarely, self-directed or object-directed biting acts were not triggered by external stimuli. Intracranial data (SEEG) obtained in one subject showed that the amygdala/hippocampal region plus the orbitomedial prefrontal cortex had to be involved by ictal activity to observe BB. Conclusions: Anatomic and electrophysiologic data in our patients suggest that a model of dual,temporal and frontal,dysfunction could account for the occurrence of ictal/postictal BB. Behavioral data suggest also that BB and related aggressive gestures can be considered as the emergence of instinctive behaviors with an adaptative significance of defense of the peripersonal space. [source] Male and Female Meadow Voles, Microtus pennsylvanicus, Differ in Their Responses to Heterospecific/Conspecific Over-MarksETHOLOGY, Issue 9 2010Christian T. Vlautin Voles use runways, paths, and trails that may also be used by rabbits and mink. These shared areas could contain the scent marks of conspecifics and heterospecifics. Thus, it is likely that the scent marks of heterospecifics may overlap or be overlapped by those of voles, forming over-marks. Much is known about how voles respond to over-marks of two different conspecifics. However, we do not know how they would respond to an opposite-sex conspecific whose scent marks are in an over-mark with the scent marks of predator or the scent marks of a non-predator heterospecifics. We tested the hypothesis that meadow voles, Microtus pennsylvanicus, differ in their response to the scent mark of the opposite-sex conspecific if the scent mark was overlapped by that of a mink, a vole predator, or rabbit, a vole non-predator. We found that female but not male voles showed a preference for the scent marks of the opposite-sex conspecifics that were part of the mink-vole over-mark when compared to those of opposite-sex conspecifics that were not part of the over-mark. This preference by female voles was independent of whether the male vole was the top-scent donor or bottom-scent donor of the over-mark. Male and female voles showed no preference between the scent marks of the opposite-sex conspecifics whose marks were part of or not part of the rabbit-vole over-mark. Sex differences in the manner that meadow voles respond to rabbit-vole and mink-vole over-marks are discussed. [source] Naked Mole-Rat is Sensitive to Social Hierarchy Encoded in Antiphonal VocalizationETHOLOGY, Issue 9 2009Shigeto Yosida The maintenance of social relationships is critical for group-dwelling species. Social animals often exhibit behaviors such as antiphonal vocalizations that reduce conflict and maintain affiliations. Naked mole-rats (Heterocephalus glaber) have a complex hierarchical society comparable to that of bees and ants. They are also known for their extensive vocal repertoire, which may have evolved in the absence of visual cues. The most frequent vocalization used by naked mole-rats is the soft chirp (SC). It has an antiphonal nature and may function in rank identification and in maintaining affiliations. Relative body weight differences, which are directly related to social rank, are positively correlated with SC emission rates. SCs are elicited from either physical touch or the SC of another conspecific, and other cues might contribute to SC utterance. In the current study, we examined whether an SC alone was able to elicit SC responses. Specifically, we presented artificial SC-like sounds and determined whether the response rate was modulated by the acoustic properties of the stimulus. An analysis of response latency revealed that animals responded to the audio stimuli, and a single audio stimulus could elicit responses from two animals. Thus, antiphony in naked mole-rats may occur among three or more animals. We also found that animals were able to discriminate the acoustic properties of the stimulus and responded more frequently to audio stimuli resembling SCs from large animals than to those resembling SCs from small animals. Therefore, naked mole-rats may be able to judge social relationships (dominant or subordinate) based solely on SCs. The constraints of subterranean habitats and increased social complexity may have led to the evolution of this communication system. [source] The Smell of New Competitors: The Response of American Mink, Mustela vison, to the Odours of Otter, Lutra lutra and Polecat, M. putoriusETHOLOGY, Issue 5 2009Lauren A. Harrington We tested the response of wild American mink (an established alien species in the UK), to the odours of unfamiliar mink, European polecat and Eurasian otter. Polecats are similar in size and habits to mink, otters are larger than mink and a dominant competitor; both are native to the UK and both were absent during the original colonization by mink but are now undergoing natural population recoveries. The response of mink to experimental odours was assessed by counting the numbers of tracks (footprints) on rafts treated with anal gland secretions, and compared with response to a control raft, on two rivers in the Upper Thames valley, UK. Remote video showed that the number of tracks was positively correlated with the time that mink spent investigating an odour. We found that mink were attracted to the odours of both unfamiliar mink and polecats. There was little evidence that mink avoided the odour of otters. We suggest that, during an encounter with a polecat, mink may behave much as they would to a conspecific. We infer from the response of mink to the odour of otters, that, if mink do avoid otters, the mechanism of avoidance is likely to be complex, situation-dependent and perhaps affected by prior experience. [source] Emergence and Consequences of Division of Labor in Associations of Normally Solitary Sweat BeesETHOLOGY, Issue 4 2009C. Tate Holbrook Division of labor is a pervasive feature of animal societies, but little is known about the causes or consequences of division of labor in non-eusocial cooperative groups. We tested whether division of labor self-organizes in an incipient social system: artificially induced nesting associations of the normally solitary sweat bee Lasioglossum (Ctenonomia) NDA-1 (Hymenoptera: Halictidae). We quantified task performance and construction output by females nesting either alone or with a conspecific. Within pairs, a division of labor repeatedly arose in which one individual specialized on excavation and pushing/tamping while her nestmate guarded the nest entrance. Task specialization could not be attributed to variation in overall activity, and the degree of behavioral differentiation was greater than would be expected due to random variation, indicating that division of labor was an emergent phenomenon generated in part by social dynamics. Excavation specialists did not incur a survival cost, in contrast to previous findings for ant foundress associations. Paired individuals performed more per capita guarding, and pairs collectively excavated deeper nests than single bees , potential early advantages of social nesting in halictine bees. [source] Female Attraction to Conspecific Chemical Cues in the Palmate Newt Triturus helveticusETHOLOGY, Issue 8 2005Jean Secondi Although chemosignals are largely used in sexual communication in urodeles, olfactometer studies in newts provided contrasting results about the sex specificity of female behavioural responses. Because long-range sexual advertisement is believed to be costly, some species might restrain this activity to close interactions with conspecifics. We tested chemical-mediated sexual attraction in female palmate newt (Triturus helveticus) by measuring the attraction to male and female odours in a linear water olfactometer. Unexpectedly, females were attracted towards conspecifics regardless of sex. They did not show attraction towards Limnaea stagnalis, a common sympatric aquatic gastropod. These results do not support the use of long-range male sexual signalling in the palmate newt. Instead, conspecific attraction is likely to promote aggregation of males and females in breeding ponds. Observations in the field and in the laboratory tend to support the aggregative behaviour of this species. We discuss the possible function of conspecific attraction in this context. Heading towards any conspecific would increase the probability of finding potential mates. Chemical cues do not need to be sex-specific at that stage so that long-range sexual advertisement might be unnecessary. This work emphasizes the need for studies investigating the evolutionary relationships between sexual signalling systems and population-distribution patterns. [source] Memory of Social Partners in Hermit Crab DominanceETHOLOGY, Issue 3 2005Francesca Gherardi We investigated the possibility that invertebrates recognize conspecific individuals by studying dominance relationships in the long-clawed hermit crab, Pagurus longicarpus. We conducted three sets of laboratory experiments to define the time limits for acquiring and maintaining memory of an individual opponent. The results reveal two characteristics that make individual recognition in this species different from standard associative learning tasks. Firstly, crabs do not require training over many repeated trials; rather, they show evidence of recognition after a single 30-min exposure to a stimulus animal. Secondly, memory lasts for up to 4 d of isolation without reinforcement. A third interesting feature of individual recognition in this species is that familiar opponents are recognized even before the formation of a stable hierarchical rank. That is, recognition seems to be relatively independent of repeated wins (rewards) or losses (punishments) in a dominance hierarchy. The experimental protocol allowed us to show that this species is able to classify conspecifics into two ,heterogeneous subgroups', i.e. familiar vs. unfamiliar individuals, but not to discriminate one individual of a group from every other conspecific from ,a unique set of cues defining that individual'. In other words, we demonstrated a ,binary', and not a ,true', individual recognition. However, 1 d of interactions with different crabs did not erase the memory of a former rival, suggesting that P. longicarpus uses a system of social partner discrimination more refined than previously shown. [source] Population and Species Divergence of Chemical Cues that Influence Male Recognition of Females in Desmognathine SalamandersETHOLOGY, Issue 7 2003Paul Verrell Growing evidence indicates that males may be more discriminating of mating partners than often has been assumed. In the North American Ocoee dusky salamander, Desmognathus ocoee (Plethodontidae: Desmognathinae), sexual incompatibility among conspecific populations is high in encounters staged in the laboratory, at least in part because males fail to recognize ,other' females as appropriate targets for courtship. I used Y-mazes to test the hypothesis that males of D. ocoee discriminate between substrate-borne chemical cues produced by ,own' (homotypic) and ,other' (heterotypic) females. Males of four populations discriminated in favor of substrates soiled by homotypic females over clean (control) substrates (expt 1), suggesting that females produce chemical cues of sociosexual significance to males. Furthermore, males from these populations discriminated in favor of substrates soiled by homotypic females vs. substrates soiled by heterotypic females (expt 2), both conspecific and heterospecific (D. carolinensis and D. orestes). Thus, differences among populations and species in female chemical cues appear to affect the chemotactic responses of males. I suggest that, together with differences in behavioral signals and responses exhibited during courtship, differences in female chemical cues likely contribute to sexual incompatibility among populations and taxa of desmognathine salamanders. [source] Foraging Behaviour of Subordinate Great Tits (Parus major).ETHOLOGY, Issue 10 2001Can Morphology Reduce the Cost of Subordination? This paper studies the magnitude of the behavioural shift, from forage standing to forage hanging, of subordinate great tits (Parus major) in two different social contexts: feeding solitarily vs. feeding with a dominant conspecific. The aim is to test the hypothesis that differences in morphological design provide subordinates with varying abilities to reduce the presumed costs of subordination. We find that different subordinate individuals change the foraging behaviour, occupying a different niche when an intra-specific competitor is present. Morphology linked to sexual dimorphism, specifically body mass, is the factor responsible for the different magnitudes of change. Lighter subordinates can remain longer than heavier ones at the feeding patch without interrupting their foraging. Thereby, the former reduce the costs of being subordinate more than the latter. Among subordinates, females are lighter than males; they also spend more time feeding in the presence of a dominant conspecific than males do. No differences are found between age categories. We find no relationship between tarsus length and individual ecological plasticity. Our results support the idea that the ecological plasticity due to morphological differences is a mechanism that allows subordinate individuals to overcome costs associated with subordination. [source] The Effects of Social Experience on Aggressive Behavior in the Green Anole Lizard (Anolis carolinensis)ETHOLOGY, Issue 9 2001Eun-Jin Yang To understand how context-specific aggression emerges from past experience, we examined how consecutive aggressive encounters influence aggressive behavior and stress responses of male green anole lizards (Anolis carolinensis). Animals were shown a video clip featuring an aggressively displaying conspecific male, which provoked aggressive responding, while control animals viewed a neutral video. After 5 d of interaction with the videos, both the subject and control groups were presented with a live conspecific. As a non-invasive assay of stress responses, we measured changes in body color and eyespot darkness, two features known to be strongly correlated with titers of stress hormones. Our results demonstrate that experience increased aggression in male anoles, but that increases in aggression to a repeated stimulus were transient. Tests with a novel conspecific indicate that the experienced animals remained aggressive when presented with novel stimuli. Although there were differences in the morphological indicators of the stress response between experimental and control groups during video presentations, there were no differences when presented with novel conspecifics. These data indicate that experience-dependent differences were not mediated by differences in the ,stressfulness' of aggressive interaction, as thought to be the case for animals in chronic subordinate/dominant dyads. We suggest that habituation and reinforcement interact to promote aggressive responding and to restrict it to novel individuals. Such context specificity is a hallmark of natural patterns of aggression in territorial species. [source] Learned Recognition of Intraspecific Predators in Larval Long-Toed Salamanders Ambystoma macrodactylumETHOLOGY, Issue 6 2001Erica L. Wildy The ability of prey to detect predators and respond accordingly is critical to their survival. The use of chemical cues by animals in predator detection has been widely documented. In many cases, predator recognition is facilitated by the release of alarm cues from conspecific victims. Alarm cues elicit anti-predator behavior in many species, which can reduce their risk of being attacked. It has been previously demonstrated that adult long-toed salamanders, Ambystoma macrodactylum, exhibit an alarm response to chemical cues from injured conspecifics. However, whether this response exists in the larval stage of this species and whether it is an innate or a learned condition is unknown. In the current study, we examined the alarm response of naïve (i.e. lab-reared) larval long-toed salamanders. We conducted a series of behavioral trials during which we quantified the level of activity and spatial avoidance of hungry and satiated focal larvae to water conditioned by an injured conspecific, a cannibal that had recently been fed a conspecific or a non-cannibal that was recently fed a diet of Tubifex worms. Focal larvae neither reduced their activity nor spatially avoided the area of the stimulus in either treatment when satiated, and exhibited increased activity towards the cannibal stimulus when hungry. We regard this latter behavior as a feeding response. Together these results suggest that an anti-predator response to injured conspecifics and to cannibalistic conspecifics is absent in naïve larvae. Previous studies have shown that experienced wild captured salamanders do show a response to cannibalistic conspecifics. Therefore, we conducted an additional experiment examining whether larvae can learn to exhibit anti-predator behavior in response to cues from cannibalized conspecifics. We exposed larvae to visual, chemical and tactile cues of stimulus animals that were actively foraging on conspecifics (experienced) or a diet of Tubifex (naïve treatment). In subsequent behavioral treatments, experienced larvae significantly reduced their activity compared to naive larvae in response to chemical cues of cannibals that had recently consumed conspecifics. We suggest that this behavior is a response to alarm cues released by consumed conspecifics that may have labeled the cannibal. Furthermore, over time, interactions with cannibals may cause potential prey larvae to learn to avoid cannibals regardless of their recent diet. [source] Avoidance of Chemical Alarm Cues Released from Autotomized Tails of Ravine Salamanders (Plethodon richmondi)ETHOLOGY, Issue 4 2001Jeffery A. Hucko The ability of animals to detect and avoid areas containing chemical alarm cues from conspecifics is well documented in aquatic species. The ability to detect chemical alarm cues in terrestrial organisms has not been tested until recently. In this study, we tested the ability of the ravine salamander (Plethodon richmondi) to detect and avoid areas containing chemicals released from the autotomized tails of conspecifics and sympatric zigzag salamanders (P. dorsalis). We also ascertained whether any avoidance response could be attributed to the size or sex of the animal. Our results suggest that ravine salamanders avoid substrates containing odors released from the autotomized tails of conspecifics, but not of heterospecific salamanders and that this response occurs independent of the size and/or sex of the animal. By avoiding areas where a conspecific has recently been injured, an organism could reduce its chances of encountering a predator and thus increase its chances of survival. [source] Development of Species Preferences in Two Hamsters, Phodopus campbelli and Phodopus sungorus: Effects of Cross-FosteringETHOLOGY, Issue 3 2001Nina YU. Experiments were conducted to investigate species-specific preferences in two closely related species of hamsters, Phodopus campbelli and Phodopus sungorus. Male hamsters that were raised with conspecifics spent more time investigating an anaesthetized conspecific male than a heterospecific male, and also spent more time investigating odours of conspecifics than those of heterospecifics (midventral gland, urine, and saccular secretion). Cross-fostered P. sungorus males reversed their normal preferences, spending more time investigating stimuli (anaesthetized males and all three odours) of the foster species. Cross-fostered P. campbelli males also investigated an anaesthetized male of the foster species more than a male of their own species, but did not show a preference for odours alone. Social experience during the 15 d immediately following weaning also influenced these preferences. If exposures during and after nesting were to heterospecifics the preference for heterospecifics was strengthened; if either period of experience was with a conspecific, this eliminated the preference for heterospecifics in P. sungorus but did not influence the lack of a preference in P. campbelli. Thus, early experience during both the nestling stage and the 15 d after weaning influenced responses to species-typical cues in both species, but it had a more pronounced effect in P. sungorus. [source] Olfactory Communication and Neighbor Recognition in Giant Kangaroo RatsETHOLOGY, Issue 2 2001Heather Gardner Murdock We hypothesized that olfactory communication facilitates neighbor recognition in the giant kangaroo rat, Dipodomys ingens, and is therefore influential in coordinating social interactions in this solitary, desert rodent. We tested whether (i) D. ingens can discriminate between odors of same- and opposite-sex conspecifics; and (ii) the kangaroo rats exhibit scent preferences based on familiarity. In habituation-discrimination tests, we found that both genders distinguish differences between the scent of individuals of the same- and opposite-sex. In olfactory preference tests, both males and females spent significantly more time investigating the scent of their familiar cagemate than the scent of an unfamiliar conspecific. Giant kangaroo rats may be able to recognize familiar neighbors from olfactory cues, thus supporting a hypothesis of neighbor recognition. Neighbor recognition may be an important mechanism of social interactions in this endangered species. [source] Meadow Voles (Microtus pennsylvanicus) and Prairie Voles (M. ochrogaster) Differ in Their Responses to Over-Marks from Opposite- and Same-Sex ConspecificsETHOLOGY, Issue 11 2000Raymond L. Woodward Jr Over-marking occurs when one individual deposits its scent mark on the scent mark of a conspecific. Previous studies have shown that meadow voles (Microtus pennsylvanicus) and prairie voles (M. ochrogaster) that were exposed to an over-mark of two same-sex conspecifics, later responded similarly to the top-scent mark but differed in their response to the bottom-scent mark. In the present study, we examined the responses of meadow voles and prairie voles to same-sex and mixed-sex over-marks to ascertain whether their responses reflect the different tactics which males and females in promiscuous (meadow voles) and monogamous (prairie voles) species use to attract opposite-sex conspecifics and to compete with same-sex conspecifics. Males and females of both species spent more time investigating the mark of the top-scent donor than that of the bottom-scent donor of an over-mark. Meadow voles exposed to a mixed-sex over-mark spent more time investigating the mark of the opposite-sex conspecific independently of whether it was from the top- or bottom-scent donor. In contrast, prairie voles spent more time investigating the mark of the opposite-sex donor if it was from the top-scent donor. These results suggest that: (i) over-marking serves a competitive function; (ii) the scent marks of individuals attract multiple mates in promiscuous species such as the meadow vole; and (iii) the scent marks of individuals establish and maintain pair bonds between familiar opposite-sex conspecifics in monogamous species such as the prairie vole. [source] Neuronal substrates of gaze following in monkeysEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2009Simone Kamphuis Abstract Human and non-human primates follow the gaze of their respective conspecific to identify objects of common interest. Whereas humans rely on eye-gaze for such purposes, monkeys preferentially use head-gaze information. Functional magnetic resonance imaging (fMRI) studies have delineated an area in the human superior temporal sulcus (STS), which is specifically activated when subjects actively follow the eye-gaze of others. Similarly, using fMRI, we have identified an analogous region in the monkey's middle STS responding to gaze following. Hence, although humans and monkeys might rely on different directional cues guiding their attention, they seem to deploy a similar and possibly homologous cortical area to follow the gaze of a conspecific. Our results support the idea that the eyes developed a new social function in human evolution, most likely to support cooperative mutual social interactions building on a phylogenetically old STS module for the processing of head cues. [source] SEX CHROMOSOME LINKAGE OF MATE PREFERENCE AND COLOR SIGNAL MAINTAINS ASSORTATIVE MATING BETWEEN INTERBREEDING FINCH MORPHSEVOLUTION, Issue 5 2010Sarah R. Pryke Assortative mating is a key aspect in the speciation process because it is important for both initial divergence and maintenance of distinct species. However, it remains a challenge to explain how assortative mating evolves when diverging populations are undergoing gene flow (e.g., during hybridization). Here I experimentally test how assortative mating is maintained with frequent gene flow between diverged head-color morphs of the Gouldian finch (Erythrura gouldiae). Contrary to the predominant view on the development of sexual preferences in birds, cross-fostered offspring did not imprint on the phenotype of their conspecific (red or black morphs) or heterospecific (Bengalese finch) foster parents. Instead, the mating preferences of F1 and F2 intermorph-hybrids are consistent with inheritance on the Z chromosomes, which are also the location for genes controlling color expression and the genes causing low fitness of intermorph-hybrids. Genetic associations between color signal and preference loci on the sex chromosomes may prevent recombination from breaking down these associations when the morphs interbreed, helping to maintain assortative mating in the face of gene flow. Although sex linkage of reproductively isolating traits is theoretically expected to promote speciation, social and ecological constraints may enforce frequent interbreeding between the morphs, thus preventing complete reproductive isolation. [source] FASTER FERTILIZATION RATE IN CONSPECIFIC VERSUS HETEROSPECIFIC MATINGS IN HOUSE MICEEVOLUTION, Issue 1 2009Matthew D. Dean Barriers to gene flow can arise at any stage in the reproductive sequence. Most studies of reproductive isolation focus on premating or postzygotic phenotypes, leaving the importance of differences in fertilization rate overlooked. Two closely related species of house mice, Mus domesticus and M. musculus, form a narrow hybrid zone in Europe, suggesting that one or more isolating factors operate in the face of ongoing gene flow. Here, we test for differences in fertilization rate using laboratory matings as well as in vitro sperm competition assays. In noncompetitive matings, we show that fertilization occurs significantly faster in conspecific versus heterospecific matings and that this difference arises after mating and before zygotes form. To further explore the mechanisms underlying this conspecific advantage, we used competitive in vitro assays to isolate gamete interactions. Surprisingly, we discovered that M. musculus sperm consistently outcompeted M. domesticus sperm regardless of which species donated ova. These results suggest that in vivo fertilization rate is mediated by interactions between sperm, the internal female environment, and/or contributions from male seminal fluid. We discuss the implications of faster conspecific fertilization in terms of reproductive isolation among these two naturally hybridizing species. [source] CONSPECIFIC SPERM PRECEDENCE IN SISTER SPECIES OF DROSOPHILA WITH OVERLAPPING RANGESEVOLUTION, Issue 4 2004Audrey S. Chang Abstract Barriers to gene flow that act after mating but before fertilization are often overlooked in studies of reproductive isolation. Where species are sympatric, such "cryptic' isolating barriers may be important in maintaining species as distinct entities. Drosophilayakuba and its sister species D. santomea have overlapping ranges on the island of Sao Tome, off the coast of West Africa. Previous studies have shown that the two species are strongly sexually isolated. However, the degree of sexual isolation observed in the laboratory cannot explain the low frequency (,1%) of hybrids observed in nature. This study identifies two "cryptic" isolating barriers that may further reduce gene flow betweenD. yakuba andD. santomea where they are sympatric. First, noncompetitive gametic isolation has evolved between D. yakuba and D. santomea: heterospecific matings between the two species produce significantly fewer offspring than do conspecific matings. Second, conspecific sperm precedence (CSP) occurs when D. yakuba females mate with conspecific and heterospecific males. However, CSP is asymmetrical: D. santomea females do not show patterns of sperm usage consistent with CSP. Drosophila yakuba and D. santomea females also differ with respect to remating propensity after first mating with conspecific males. These results suggest that noncompetitive and competitive gametic isolating barriers may contribute to reproductive isolation between D. yakuba and D. santomea. [source] | ||||||||||||||||||||||||||||||||||||||||||||||