The Experts below are selected from a list of 1566 Experts worldwide ranked by ideXlab platform
Ute Radespiel - One of the best experts on this subject based on the ideXlab platform.
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contest versus Scramble Competition for mates the composition and spatial structure of a population of gray mouse lemurs microcebus murinus in north west madagascar
Primates, 2001Co-Authors: Ute Radespiel, Petra Ehresmann, Elke ZimmermannAbstract:The modes of intrasexual Competition interacting in many dispersed societies of nocturnal solitary foragers are still poorly understood. In this study we investigate the spatial structure within a free-living population of gray mouse lemurs (Microcebus murinus) in order to test for the first time the predictions from two contrasting models of male intrasexual Competition on the population level. The contest Competition model predicts an uneven distribution of the sexes in a population nucleus with a female biased sex ratio in the center and a male biased sex ratio in the periphery. In contrast the Scramble Competition model predicts males and females being distributed evenly throughout their habitat with a constant sex ratio. Nine capture/recapture periods within three consecutive mating seasons revealed a continuous male biased sex ratio in the adult population with even trapping rates for the sexes. The male biased sex ratio could either be explained with postnatal female biased mortality or with a male biased natal sex ratio. This male biased sex ratio was apparent in all parts of the study site, indicating that the population was not subdivided into a female biased core and a male biased periphery. Furthermore, the majority of adult males have been captured at the same site as or in vicinity to females. Consequently, a large proportion of males had spatial access to females during the mating season. No signs of monopolization of females by certain dominant males could be detected. These data support the predictions from the Scramble Competition model and the concept of a promiscuous mating system for this species.
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sociality in the gray mouse lemur microcebus murinus in northwestern madagascar
American Journal of Primatology, 2000Co-Authors: Ute RadespielAbstract:The mating system and social organization of the gray mouse lemur (Microcebus murinus) was investigated in two three-month field studies (covering a period before, during, and after the first mating season) in Ampijoroa, northwestern Madagascar. The spatial and temporal distribution of the sexes within a population was studied using mark/recapture techniques and radiotelemetry to assess possible contest or Scramble Competition between the males. Sociality was inferred from the occurrence and probability of nocturnal social encounters, the temporal stability of daily sleeping groups, and nocturnal ranging patterns of co-sleepers. Males and females were evenly distributed in the study area within a network of highly overlapping home ranges. No indications were found for the spatial monopolization of the females by certain dominant males. Males and females had spatial access to several potential mates; the mating system is therefore characterized as a multi-male/multi-female system. Male home range sizes increased during the first mating season, which was interpreted as an indicator for Scramble Competition between the males. Competitive mate searching, sperm Competition, and temporary mate guarding as well as female mate choice are suggested as the most probable reproductive strategies. Over the course of the study the animals lived continually within the study area, and most females formed stable individualized sleeping associations. Females that slept together shared a higher percentage of their home range than did females that slept at different sites. It is suggested that this network of social relationships should be described as a dispersed but individualized neighborhood.
Colin A Chapman - One of the best experts on this subject based on the ideXlab platform.
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red colobus monkeys display alternative behavioral responses to the costs of Scramble Competition
Behavioral Ecology, 2008Co-Authors: Tamaini V Snaith, Colin A ChapmanAbstract:Food Competition is an expected cost of group living. It is therefore puzzling that there is little evidence for Competition among group-living folivorous monkeys, for example, daily travel distance does not seem to increase with group size. It is even more puzzling that folivores do not form larger groups despite this apparent lack of food Competition. This has become known as the folivore paradox, and to date, there is no broadly accepted theoretical solution. However, there have been no multigroup studies that have controlled for the potentially confounding effects of variation in habitat quality. We studied 9 groups of red colobus monkeys (Procolobus rufomitratus) in Kibale National Park, Uganda, and controlled for spatial and temporal variation in food availability. We found that larger groups occupied larger home ranges than smaller groups and that group size was related to increased foraging effort (longer daily travel distance), increased group spread, and reduced female reproductive success. Our results also suggest that monkeys in larger groups spent more time feeding and less time engaged in social behavior. These results suggest that folivorous red colobus monkeys experience within-group Scramble Competition and possess a suite of behavioral responses that may mitigate the cost of Competition and represent adaptations for group living. The results offer insight into the folivore paradox and the evolutionary ecology of group size.
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towards an ecological solution to the folivore paradox patch depletion as an indicator of within group Scramble Competition in red colobus monkeys piliocolobus tephrosceles
Behavioral Ecology and Sociobiology, 2005Co-Authors: Tamaini V Snaith, Colin A ChapmanAbstract:A number of socioecological models assume that within-group food Competition is either weak or absent among folivorous primates. This assumption is made because their food resources are presumed to be superabundant and evenly dispersed. However, recent evidence increasingly suggests that folivore group size is food-limited, that the primates prefer patchily distributed high-quality foods, and display some of the expected responses to within-group Scramble Competition. To investigate this apparent contradiction between theoretical models and recent empirical data, we examined the foraging behaviour of red colobus monkeys (Piliocolobus tephrosceles) in Kibale National Park, Uganda. We found that red colobus monkeys foraged in a manner that suggests they deplete patches of preferred foods: intake rate slowed significantly during patch occupancy while movement rate, an index of foraging effort, increased. Furthermore, patch occupancy was related to the size of the feeding group and the size of the patch. These results suggest that within-group Scramble Competition occurs, may limit folivore group size, and should be considered in models of folivore behavioural ecology.
Nicola Saino - One of the best experts on this subject based on the ideXlab platform.
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fine tuned modulation of competitive behaviour according to kinship in barn swallow nestlings
Proceedings of The Royal Society B: Biological Sciences, 2009Co-Authors: Giuseppe Boncoraglio, Manuela Caprioli, Nicola SainoAbstract:Kin selection theory predicts that, in species where progeny members compete for limiting parental care, individual offspring should be more prone to monopolize parental resources as their genetic relatedness to brood competitors decreases. Mixed parentage among broodmates may arise as a consequence, for example, of extra-pair fertilization or brood parasitism events. In this experimental study of barn swallows (Hirundo rustica), we reciprocally partially cross-fostered hatchlings between broods and compared the behaviour of pairs of related and unrelated broodmates in a competitive context, both under normal food provisioning regime and after mild food deprivation. We found that Scramble Competition for food mediated by visual and vocal solicitation displays (begging) is inversely related to relatedness among competitors, independent of their level of satiation. Nestlings may modulate their competitive behaviour according to vocal cues that vary with their origin and allow kin recognition. We also uncover direct fitness costs to both parents and offspring arising from mixed parentage in a brood, in terms of increased parental workload and reduced survival of the nestlings. Such previously neglected costs may select for reduced frequency of extra-pair fertilizations and brood parasitism in species with extensive parental care.
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sex related asymmetry in competitive ability of sexually monomorphic barn swallow nestlings
Behavioral Ecology and Sociobiology, 2008Co-Authors: Giuseppe Boncoraglio, Roberta Martinelli, Nicola SainoAbstract:In diverse taxa, offspring solicit parental care using complex displays, which may evolve as reliable signals of condition or as mechanisms to manipulate parental investment. Differential sex allocation may therefore result from adaptive parental decisions or sex-related variation in competitive ability or because of sex-related asymmetries in kin selection. Under normal food provisioning, female barn swallow (Hirundo rustica) nestlings begged more loudly but did not receive more food than male nestlings. After food deprivation, begging call loudness of males but not females increased. Begging loudness positively predicted the number of feedings received by the nestlings, and males gained more mass than females after food deprivation. Male nestlings are more severely affected by chronic food reduction and may therefore accrue a larger benefit compared to females by increasing their food intake under short-term conditions of food scarcity. These results suggest that either females do not increase begging intensity to favour male broodmates which are more vulnerable to prolonged food stress, or that males prevail in Scramble Competition despite being similar in size to females.
Jeffrey E Lane - One of the best experts on this subject based on the ideXlab platform.
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energetic costs of male reproduction in a Scramble Competition mating system
Journal of Animal Ecology, 2010Co-Authors: Jeffrey E Lane, Stan Boutin, John R Speakman, Murray M HumphriesAbstract:Summary 1. The assumption that the primary limitations on reproductive success differ between the sexes is inherent in traditional sexual selection theory. Although the energy that can be allocated to reproduction is assumed to be the main limitation to females, the ability to attract and defend oestrous females is assumed to be the primary limitation to males. 2. Estimates of the energetic costs of reproduction in male mammals are, however, limited and have largely been obtained from sexually dimorphic species exhibiting female defence mating systems. These studies often reveal that the energetic cost of male reproduction is similar to or even exceeds that of females, and therefore challenge long-held assumptions of inter-sexual reproductive limitations, but their generality is little known. 3. We coupled measurements of energy expenditure with detailed behavioural observations of reproductive male North American red squirrels (Tamiasciurus hudsonicus). This species displays minimal sexual dimorphism and exhibits a Scramble Competition mating system, under which sexual selection favours enhanced mate searching effort by males. 4. We conducted the study over 2 years characterized by a substantial variation in upcoming natural food availability and across two study populations that experienced either natural food abundance or an ad libitum food-supplementation to investigate the influence of resource availability on male reproductive energy expenditure. 5. Under natural conditions, mean energy expenditure of males across the 2 years was high, approximating that of females during lactation. Furthermore, in the anticipation of high upcoming natural food availability and resultant offspring survival, expenditure approximately doubled (from 290 ± 7 to 579 ± 73 kJ day−1). When current food availability (and consequently the density of receptive females) was experimentally elevated, males displayed the highest levels of energy expenditure we recorded (873 ± 98 kJ day−1). 6. Our results provide compelling evidence that the energy available for reproductive allocation places a strong limitation on reproduction in male North American red squirrels and contribute to previous work suggesting that high and limiting energetic costs of male reproduction may be a general feature of mammalian reproduction.
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sexually selected behaviour red squirrel males search for reproductive success
Journal of Animal Ecology, 2009Co-Authors: Jeffrey E Lane, Stan Boutin, Melissa R Gunn, David W ColtmanAbstract:1. Differential male reproductive success is commonplace in mammals and frequently attributed to variation in morphological traits that provide individuals with a competitive advantage in female defence mating systems. Other mammalian mating systems, however, have received comparatively little attention and correlates of male reproductive success in them are less well understood. 2. We studied a free-ranging population of North American red squirrels (Tamiasciurus hudsonicus Erxleben) exhibiting year-round individual territoriality. Males must temporarily vacate their territories to locate spatially dispersed receptive females, thereby setting the stage for a Scramble Competition mating system. 3. We predicted that both male annual mating success (measured as the number of females copulated with) and annual reproductive success (measured as the number of offspring sired) would be positively correlated with both search ability (measured as the number of oestrous females located over the mating season) and effort (measured as mating season home range size), generating directional sexual selection on these two metrics. 4. Mating season home ranges of males showed, on average, an almost 10-fold increase relative to those measured during the nonmating season, while those of females showed a more moderate twofold increase and both annual mating and reproductive success of males was positively correlated with search ability and search effort. 5. The spatial dispersion of females, resulting from the strict territorial social structure of red squirrels, gave rise to a predicted Scramble Competition mating system. Furthermore, the strength of sexual selection on behavioural traits in this mating system equalled previous estimates for morphological traits in female defence mating systems.
Rogelio Maciasordonez - One of the best experts on this subject based on the ideXlab platform.
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males but not females perform strategic mate searching movements between host plants in a leaf beetle with Scramble Competition polygyny
Ecology and Evolution, 2018Co-Authors: Danilo G Muniz, Martha L Baena, Rogelio Maciasordonez, Glauco MachadoAbstract:Mate searching is assumed to be performed mostly by males, but when females benefit from multiple mating or are under risk of failing to mate, they may also perform mate searching. This is especially important in Scramble Competition polygynies, in which mate searching is the main mechanism of mate Competition. Typically, more mobile individuals are expected to achieve higher mating success because mobility increases their probability of finding mates. If we assume individual movements are mainly explained by mate searching in Scramble Competition polygynies, we can investigate searching strategies by asking when individuals should leave their location and where they should go. We hypothesize that individuals will leave their locations when mating opportunities are scarce and will seek spatially close sites with better mating opportunities. We tested these hypotheses for males and females of Leptinotarsa undecimlineata, a leaf beetle with Scramble Competition polygyny in which both sexes are promiscuous. Individuals mate and feed exclusively on Solanum plants, and thus, individual movements can be described as switches between plants. Females were less likely than males to leave isolated plants, and both males and females moved preferentially to neighboring plants. Males were more likely to leave when the local number of females was low, and the number of males was high. They moved to plants with more females, a behavior consistent with a mate searching strategy. Females were more likely to move to plants with fewer males and many females, a behavior consistent with male harassment avoidance. Strategic movement is widely considered in foraging context, but seldom in a mate searching context. Considering that selection to minimize searching costs, maximize mating success, and minimize harassment may be ubiquitous in nature, we argue that strategic movements by mate searching individuals are likely to occur in many species.
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mobility and mating frequency in the Scramble Competition polygyny of a chrysomelid beetle
Behavioral Ecology, 2015Co-Authors: Martha L Baena, Rogelio MaciasordonezAbstract:In Scramble Competition polygyny, male and female mobility may be under strong selection as a result of fitness effects of searching for reproductive resources such as mates, oviposition sites, or resources for egg production. We analyzed the relationship between mating frequency, mobility, and body size in males and females of the chrysomelid beetle Leptinotarsa undecimlineata. We obtained a detailed data set of movement and mating frequency of an entire population (1037 adults) over a full reproductive season using individual tagging and direct behavioral observations. Unlike previous studies, we found a negative relationship between mobility and mating success for both sexes. Size was positively correlated to mating frequency in females, but negatively in males. High male mobility may be the result, and not a cause, of low mating success in Scramble mating polygynies where rejected or displaced males switch plants more often searching for mating opportunities. More mobile females may be looking for Competition-free oviposition substrate and thus experiencing fewer sexual encounters.
