Home About us Contact | |||
Subadult Males (subadult + male)
Selected AbstractsEffects of intensive harvesting on moose reproductionJOURNAL OF APPLIED ECOLOGY, Issue 3 2000Catherine Laurian Summary 1.,It has been hypothesized that a balanced adult sex ratio is necessary for the full participation of ungulate females in reproduction and therefore high productivity. We tested this general hypothesis by combining two complementary approaches. 2.,First, using telemetry (n = 60) and annual aerial censuses between 1995 and 1998, we compared two moose Alces alces populations in Quebec, Canada, one non-harvested and the other subject to intensive sport harvesting from the end of September to mid-October. We tested the following predictions for the harvested population: (i) females increase movements and home ranges during the mating period; (ii) the mating system is modified, with the appearance of groups of one male and many females; (iii) subadult males participate in reproduction; (iv) the mating period extends over two to three oestrus cycles; (v) the calving period extends over several months; and (vi) productivity declines. 3.,Daily movements and home range sizes during the mating period did not differ between harvested and non-harvested populations. Most groups observed were male,female pairs. Subadult males (1·5,2·5 years old) were only observed with females in the harvested population. Mating and calving periods did not differ between populations. The proportion of females that gave birth and the number of calves produced were also comparable in the two populations. 4.,Secondly, we also assessed the existence of a relationship between population productivity and percentage of males in various management units of the province of Quebec that were characterized by a wide range in sex ratios. Contrary to prediction (vi), the number of calves per 100 adult females was not related to the percentage of adult males in the population. 5.,The participation of young adult males (subadults) in reproduction in our harvested population may have compensated for the lower percentage of adult males, and thus productivity was unaffected. We therefore reject the hypothesis that intensive harvesting, at least at the level we observed, affects reproduction and population productivity. 6.,As there are some uncertainties regarding the long-term effects of high hunting pressure, however, managers should favour sex ratios close to levels observed in non-harvested populations. [source] Evaluation of the chondral modeling theory using fe-simulation and numeric shape optimizationJOURNAL OF ANATOMY, Issue 5 2009Jeffrey H. Plochocki Abstract The chondral modeling theory proposes that hydrostatic pressure within articular cartilage regulates joint size, shape, and congruence through regional variations in rates of tissue proliferation. The purpose of this study is to develop a computational model using a nonlinear two-dimensional finite element analysis in conjunction with numeric shape optimization to evaluate the chondral modeling theory. The model employed in this analysis is generated from an MR image of the medial portion of the tibiofemoral joint in a subadult male. Stress-regulated morphological changes are simulated until skeletal maturity and evaluated against the chondral modeling theory. The computed results are found to support the chondral modeling theory. The shape-optimized model exhibits increased joint congruence, broader stress distributions in articular cartilage, and a relative decrease in joint diameter. The results for the computational model correspond well with experimental data and provide valuable insights into the mechanical determinants of joint growth. The model also provides a crucial first step toward developing a comprehensive model that can be employed to test the influence of mechanical variables on joint conformation. [source] A cranial base of Australopithecus robustus from the hanging remnant of Swartkrans, South AfricaAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 4 2006Darryl J. de Ruiter Abstract SKW 18, a partial hominin cranium recovered from the site of Swartkrans, South Africa, in 1968 is described. It is derived from ex situ breccia of the Hanging Remnant of Member 1, dated to approximately 1.5,1.8 Mya. Although partially encased in breccia, it was refit to the facial fragment SK 52 (Clarke 1977 The Cranium of the Swartkrans Hominid SK 847 and Its Relevance to Human Origins, Ph.D. dissertation, University of the Witwatersrand, Johannesburg), producing the composite cranium SKW 18/SK 52. Subsequent preparation revealed the most complete cranial base attributable to the species Australopithecus robustus. SKW 18 suffered weathering and slight postdepositional distortion, but retains considerable anatomical detail. The composite cranium most likely represents a large, subadult male, based on the incomplete fusion of the spheno-occipital synchondrosis; unerupted third molar; pronounced development of muscular insertions; and large teeth. Cranial base measures of SKW 18 expand the range of values previously recorded for A. robustus. SKW 18 provides information on anatomical features not previously visible in this taxon, and expands our knowledge of morphological variability recognizable in the cranial base. Morphological heterogeneity in the development of the prevertebral and nuchal muscular insertions is likely the result of sexual dimorphism in A. robustus, while differences in cranial base angles and the development of the occipital/marginal sinus drainage system cannot be attributed to size dimorphism. Am J Phys Anthropol, 2006. © 2006 Wiley-Liss, Inc. [source] Male mating tactics in spider monkeys: sneaking to competeAMERICAN JOURNAL OF PRIMATOLOGY, Issue 9 2010K. Nicole Gibson Abstract I investigated the mating system and male mating tactics for a population of wild spider monkeys (Ateles belzebuth chamek), to identify the behaviors males used to achieve and maintain access to sexually receptive females, and to examine if some males used more tactics than other males and/or had differential access to females. Results show that the mating system mostly involved scramble competition polygyny and that males used a range of mating tactics and behaviors, previously unreported for spider monkeys. The most unusual feature of spider monkey mating behavior was the secretive nature of copulations,nearly all copulations were clandestine, but a few were in the presence of other group members. Fifteen sexually mature males were observed to copulate 43 times. These data provide the first opportunity to evaluate how female availability influences male,male competition. First, the operational sex ratio was highly skewed toward males because usually only one female was receptive in each community per month. Second, females only mated with a few males in their community in any one mating period, but some females mated over the course of multiple consecutive mating periods, eventually mating with most or all of the males in their community. Across all communities, 9 (21%) of the 43 copulations involved a single male,female partner, 20 (47%) involved four males mating with the same female, and males mated with from one to four different females. Fourteen of the 16 total adult males and 1 subadult male (10 total) copulated. One or two males in each community were successful in monopolizing access to receptive females, and these males did not usually have the highest rates of copulation. In this system, clandestine copulations are one behavioral solution to the complex problem of gaining mating exclusivity and, probably, exercising mate choice. Am. J. Primatol. 72:794,804, 2010. © 2010 Wiley-Liss, Inc. [source] Singing behavior and singing functions of black-crested gibbons (Nomascus concolor jingdongensis) at Mt. Wuliang, central Yunnan, ChinaAMERICAN JOURNAL OF PRIMATOLOGY, Issue 7 2009Peng-Fei Fan Abstract We used data on loud duetted and solo songs collected from one habituated polygynous group of black-crested gibbons (Nomascus concolor jingdongensis) on Mt. Wuliang, Yunnan, to test several hypotheses about the functions of these songs. The major functions proposed for loud gibbon songs include resource defense, mate defense, pairbonding, group cohesion and mate attraction. Duet bouts are generally initiated by adult males, who select the highest trees near to ridges or on steep slopes as singing trees. Such trees facilitate voice transmission and inter-group communication. Singing trees tended to be located near important food patches and sleeping sites, which supports the resource defense hypothesis. The adult male and two adult females always sang interactively, alternating male phrases with the females' stereotyped great calls, to produce the duets, and females rarely produced great calls if they were more than 30,m from the male. The two females usually produced great calls synchronously during the duet, especially when they were close together. These features support both the mate defense and pairbonding hypotheses. The number of great calls and their degree of synchrony transmit information about spatial relationships and possibly pairbond strength to members to neighboring groups and floating animals. During or after the duet bouts, the adult females and juvenile moved toward to the adult male; and group members maintained a close spatial relationship, which supports the group cohesion hypothesis. Other incidents observed suggest a mate competition role for duets. The adult male always sang when the females started duetting with the subadult male. The subadult male sang solo bouts, but they were not more frequent or longer than bouts initiated by the adult male. Although mate attraction is the likely function of subadult solos, it was not convincingly demonstrated. In conclusion, all hypotheses concerning the function of singing are supported by at least some of the data, and none can be excluded. Am. J. Primatol. 71:539,547, 2009. © 2009 Wiley-Liss, Inc. [source] Sex, Rank and Age Differences in the Japanese Macaque (Macaca fuscata yakui) Participation in Inter-Group EncountersETHOLOGY, Issue 5 2005Bonaventura Majolo In many species interactions among group are often characterized by agonistic behaviour. Although animals may participate in inter-group encounters in different ways, depending on their energetic requirements, reproductive tactics, and/or developmental stage, the proximate causes affecting an animal's participation in inter-group encounters are still poorly understood. Indeed, many studies have analysed the behaviour of males and females during inter-group encounters without considering the importance of additional factors (e.g. rank). This study focuses on wild non-provisioned Japanese macaques (Macaca fuscata yakui) living on Yakushima Island, Japan. It aims to determine how monkeys of different sex, age, and rank behave during inter-group encounters and it discusses the implications and consequences of their behaviour on group composition and male dispersal. Males participated significantly more than females in inter-group encounters, by displaying more aggressive or affiliative behaviour. High-ranking and/or adult males were more aggressive than low-ranking and/or subadult males during encounters occurring in the mating season and they also showed more herding behaviour. This trend was not found in inter-group encounters occurring during the non-mating season. Finally, males which then emigrated to new groups were low-ranking and/or subadult individuals. Those males displayed more affiliative behaviour towards foreign males than males which did emigrate. These data indicate that in non-territorial species with male dominance over female and high competition for mating partners males play an active, and often aggressive, role during inter-group encounter while female participation is scarce. Factors such as age, rank and period of the year (in seasonally breeding species) have to be taken into considerations when analysing interactions between groups and their effects on group composition and social behaviour. [source] Host sex and ectoparasites choice: preference for, and higher survival on female hostsJOURNAL OF ANIMAL ECOLOGY, Issue 4 2007PHILIPPE CHRISTE Summary 1Sex differences in levels of parasite infection are a common rule in a wide range of mammals, with males usually more susceptible than females. Sex-specific exposure to parasites, e.g. mediated through distinct modes of social aggregation between and within genders, as well as negative relationships between androgen levels and immune defences are thought to play a major role in this pattern. 2Reproductive female bats live in close association within clusters at maternity roosts, whereas nonbreeding females and males generally occupy solitary roosts. Bats represent therefore an ideal model to study the consequences of sex-specific social and spatial aggregation on parasites' infection strategies. 3We first compared prevalence and parasite intensities in a host,parasite system comprising closely related species of ectoparasitic mites (Spinturnix spp.) and their hosts, five European bat species. We then compared the level of parasitism between juvenile males and females in mixed colonies of greater and lesser mouse-eared bats Myotis myotis and M. blythii. Prevalence was higher in adult females than in adult males stemming from colonial aggregations in all five studied species. Parasite intensity was significantly higher in females in three of the five species studied. No difference in prevalence and mite numbers was found between male and female juveniles in colonial roosts. 4To assess whether observed sex-biased parasitism results from differences in host exposure only, or, alternatively, from an active, selected choice made by the parasite, we performed lab experiments on short-term preferences and long-term survival of parasites on male and female Myotis daubentoni. When confronted with adult males and females, parasites preferentially selected female hosts, whereas no choice differences were observed between adult females and subadult males. Finally, we found significantly higher parasite survival on adult females compared with adult males. 5Our study shows that social and spatial aggregation favours sex-biased parasitism that could be a mere consequence of an active and adaptive parasite choice for the more profitable host. [source] Within-sex density dependence and population dynamics of red squirrels Sciurus vulgarisJOURNAL OF ANIMAL ECOLOGY, Issue 1 2004Luc A. Wauters Summary 1Social organization and dispersal of red squirrels (Sciurus vulgaris L.) differ between sexes, and intrasexual competition is intense. Therefore, we predicted that demographic parameters should be gender-specific: that is density-dependent factors will be more strongly related to density of the same sex than to density of the opposite sex. We studied the relative importance of within- and between-sex density-dependent factors and of density-independent factors (habitat type, food abundance, winter temperature) on different demographic parameters, in two populations in northern Belgium. 2Spring density of males was positively correlated with tree-seed abundance in the previous year, but this was not the case for females. None of the population parameters we measured differed between habitats, indicating that the same density-dependent and density-independent mechanisms prevailed in coniferous and deciduous habitat. 3Within each sex, we found several demographic parameters that were dependent on the densities of the same sex; however, none of these parameters was found to be dependent on the density of the opposite sex. 4Reproductive rate increased with food abundance and decreased with female density. Adult survival of females decreased with female density in autumn,winter, while survival of adult males in spring,summer increased with the size of the previous year's seed crop. 5Immigration rate of males was higher in spring than in autumn, and spring immigration increased with food abundance. Male recruitment rate, in both seasons, increased with food abundance, but was male density dependent. However, spring,summer loss rates also increased when food supplies were good, suggesting that despite high food availability, emigration of juvenile and subadult males increased when intrasexual competition was intense. Recruitment rate of females decreased with increasing female density. After a good seed crop, more subadult females dispersed, but their settlement success (recruitment) was lower at high female density. 6Seed crop size positively affected red squirrel densities through increased reproduction, immigration and adult survival of males, but density-dependent reproduction and within-sex density-dependent recruitment of locally born juveniles and dispersing subadults limit the fluctuations in numbers and regulate densities in winter,early spring, as well as in summer. [source] Effects of intensive harvesting on moose reproductionJOURNAL OF APPLIED ECOLOGY, Issue 3 2000Catherine Laurian Summary 1.,It has been hypothesized that a balanced adult sex ratio is necessary for the full participation of ungulate females in reproduction and therefore high productivity. We tested this general hypothesis by combining two complementary approaches. 2.,First, using telemetry (n = 60) and annual aerial censuses between 1995 and 1998, we compared two moose Alces alces populations in Quebec, Canada, one non-harvested and the other subject to intensive sport harvesting from the end of September to mid-October. We tested the following predictions for the harvested population: (i) females increase movements and home ranges during the mating period; (ii) the mating system is modified, with the appearance of groups of one male and many females; (iii) subadult males participate in reproduction; (iv) the mating period extends over two to three oestrus cycles; (v) the calving period extends over several months; and (vi) productivity declines. 3.,Daily movements and home range sizes during the mating period did not differ between harvested and non-harvested populations. Most groups observed were male,female pairs. Subadult males (1·5,2·5 years old) were only observed with females in the harvested population. Mating and calving periods did not differ between populations. The proportion of females that gave birth and the number of calves produced were also comparable in the two populations. 4.,Secondly, we also assessed the existence of a relationship between population productivity and percentage of males in various management units of the province of Quebec that were characterized by a wide range in sex ratios. Contrary to prediction (vi), the number of calves per 100 adult females was not related to the percentage of adult males in the population. 5.,The participation of young adult males (subadults) in reproduction in our harvested population may have compensated for the lower percentage of adult males, and thus productivity was unaffected. We therefore reject the hypothesis that intensive harvesting, at least at the level we observed, affects reproduction and population productivity. 6.,As there are some uncertainties regarding the long-term effects of high hunting pressure, however, managers should favour sex ratios close to levels observed in non-harvested populations. [source] Hunting differentially affects mixed-sex and bachelor-herds in a gregarious ungulate, the impala (Aepyceros melampus: Bovidae)AFRICAN JOURNAL OF ECOLOGY, Issue 1 2010Christiane Averbeck Abstract We investigated herd-sizes and herd-compositions of Impala (Aepyceros melampus) inside a protected area [Lake Mburo National Park (LMNP) in western Uganda] and the unprotected adjacent ranchland [the Ankole Ranching Scheme (ARS)]. Impala experience intense hunting and poaching in the study area, and poaching is especially strong on the ARS. We found evidence for changes in overall group-sizes in both mixed-sex and pure bachelor herds between areas in and outside LMNP. Mixed-sex herds strongly decreased in size outside the National Park, but bachelor herds even slightly increased in size. While the group-composition of mixed-sex herds was very similar in areas in and outside LMNP, bachelor herds comprised more yearlings and subadult males on the ARS. Our study suggests that effects of hunting and other human nuisance may differ between herd types: mixed herds probably decrease in size because females are more strongly hunted. Around LMNP, impala are usually hunted using nets and spears, thereby increasing the hunters' chance of being injured. Poachers therefore prefer hornless females (and their calves), as it is less dangerous to handle net-caught females than males. As a result, males are less hunted, but increased vigilance and, therefore, reduced aggression among the members of a bachelor herd, may account for the observed increase in herd sizes and changes in group-compositions. Résumé Nous avons étudié la taille et la composition des hardes d'impalas (Aepyceros melampus) dans une aire protégée, le Parc National du Lac Mburo (LMNP) dans l'ouest de l'Ouganda, et dans le ranch adjacent non protégé, le Ankole Ranching Scheme (ARS). Les impalas subissent une chasse et un braconnage intenses dans la région étudiée et le braconnage est particulièrement grave dans l'ARS. Nous avons découvert des preuves de changement de la taille moyenne des groupes, aussi bien dans les hardes mixtes que dans celles composées uniquement de mâles, entre les aires situées dans et en dehors du LMNP. La taille des hardes mixtes diminuait fortement hors du parc national alors que les hardes composées de mâles augmentaient légèrement. Alors que la composition des groupes mixtes était très semblable dans et en dehors de l'aire protégée, les groupes de mâles comprenaient plus de jeunes de l'année et de subadultes dans l'ARS. Notre étude laisse penser que les effets de la chasse et des autres nuisances d'origine humaine pourraient différer selon le type de harde: la taille des hardes mixtes se réduit probablement parce que les femelles sont chassées davantage. Autour du LMNP, les impalas sont d'habitude chassés au moyen de filets et de flèches, ce qui augmente les risques que les chasseurs soient blessés. Les braconniers préfèrent donc les femelles, sans cornes, et leurs jeunes parce qu'il est plus facile de manipuler des femelles prises dans des filets que des mâles. Par conséquent, les mâles sont moins chassés, et une plus grande vigilance et donc une moins forte agression entre les membres d'une harde de mâles peuvent expliquer en partie pourquoi la taille des hardes augmente et la composition des groupes varie. [source] Absence of a dominance hierarchy confirms territorial organization in male bushbuck (Tragelaphus scriptus Pallas, 1766)AFRICAN JOURNAL OF ECOLOGY, Issue 3 2009Torsten Wronski Abstract It has been suggested that all species of spiral-horned antelopes (Tragelaphini) lack territoriality. Furthermore, some authors suggested that bushbuck (Tragelpahus scriptus) males form dominance hierarchies. In this study, we investigated the dominance relationships in two groups of free-ranging bushbuck males in Queen Elizabeth National Park, Uganda. Adult males dominated young-adult bachelors and subadult males, but no distinct dominance relationships were found among adult males. Landau,s index of linearity revealed no linear dominance hierarchy in the study populations. Our results support the idea that adult males are territorial, and overt aggression is directed almost exclusively towards bachelors that challenge territory holders. Résumé On a suggéré que toutes les espèces d'antilopes à cornes spiralées (Tragelaphineae) ne montraient pas de territorialité. Qui plus est, certains auteurs ont suggéré que les mâles Guib harnaché (Tragelaphus scriptus) formaient des hiérarchies par dominance. Dans cette étude, nous avons cherché les relations de dominance dans deux groupes de mâles Guib harnaché vivant en liberté dans le Parc National Queen Elizabeth, en Ouganda. Les mâles adultes dominaient les jeunes mâles célibataires et les mâles sub-adultes, mais on n'a trouvé aucune relation de dominance distincte entre les mâles adultes. L'index de linéarité de Landau n'a révélé aucune hiérarchie linéaire de dominance dans les populations de l'étude. Nos résultats soutiennent l'idée que les mâles adultes sont territoriaux, et toute agression manifeste est dirigée presque exclusivement vers les jeunes célibataires qui défient ceux qui détiennent un territoire. [source] Ecology of the gastrointestinal parasites of Colobus vellerosus at Boabeng-Fiema, Ghana: Possible anthropozoonotic transmissionAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 3 2009Julie A. Teichroeb Abstract Parasite richness and prevalence in wild animals can be used as indicators of population and ecosystem health. In this study, the gastrointestinal parasites of ursine colobus monkeys (Colobus vellerosus) at the Boabeng-Fiema Monkey Sanctuary (BFMS), Ghana, were investigated. BFMS is a sacred grove where monkeys and humans have long lived in relatively peaceful proximity. Fecal samples (n = 109) were collected opportunistically from >27 adult and subadult males in six bisexual groups and one all-male band from July 2004 to August 2005. Using fecal floatation, we detected three protozoans (two Entamoeba sp., Isospora sp.), five nematodes (Ascaris sp., Enterobius sp., Trichuris sp., two strongyle sp.), and one digenean trematode. Using fluorescein labeled antibodies, we detected an additional protozoan (Giardia sp.), and with PCR techniques, we characterized this as G. duodenalis Assemblage B and also identified a protistan (Blastocystis sp., subtype 2). The most prevalent parasite species were G. duodenalis and Trichuris sp. Parasites were more prevalent in the long wet season than the long dry. Parasite prevalence did not vary by age, and average parasite richness did not differ by rank for males whose status remained unchanged. However, males that changed rank tended to show higher average parasite richness when they were lower ranked. Individuals that spent more time near human settlements had a higher prevalence of Isospora sp. that morphologically resembled the human species I. belli. The presence of this parasite and G. duodenalis Assemblage B indicates possible anthropozoonotic and/or zoonotic transmission between humans and colobus monkeys at this site. Am J Phys Anthropol, 2009. © 2009 Wiley-Liss, Inc. [source] |