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1.
A. Treves 《Behavioral ecology and sociobiology》2001,50(1):61-71
At least three general categories of environmental pressure - predation, resource distribution, and demographics - shape the costs and benefits of group-living for animals. Among the demographic factors that influence individual survival and reproduction, the composition of social groups can play an important role. Census data drawn from 26 populations of howler monkeys (Alouatta spp.) were used to determine if the composition of groups explained variation in their reproductive performance. Each group's reproductive performance was estimated by calculating the difference between the observed number of immatures and the number expected from its population average. Of four group structure variables tested, only one - the residual of the adult and subadult sex ratio - was a consistent correlate of reproductive performance across the howler monkey populations. Groups with a greater proportion of adult and subadult males contained more juveniles than expected from the population average. I propose that the survival or retention of immatures within howler monkey groups depends in part on the behavior of resident males. Of particular importance, the relative proportions of resident males and females were more informative than the absolute number of males or females. On this basis, I evaluate the possible role of males in protection from predation, conspecific aggression, and resource competition. The techniques used here can also be used to forecast major changes in demographic structure within populations. 相似文献
2.
The number of adult males in a bisexual primate group is thought to be determined mainly by the defensibility of mating access to the females. However, among primates, small groups sometimes contain several adult male. We evaluate the hypothesis that high predation risk may lead to greater male representation in primate groups, independent of the effect of group size. Male primates are known to be more vigilant than females, and may also be better at detecting potential predators. A comparative test was done using arboreal folivores in three continents, howler monkeys in the Neotropics, colobus monkeys in Africa and langurs in South and Southeast Asia. Howlers and colobus are exposed to predation by large monkey-eating eagles, whereas the langurs are not. We conducted regression analyses on group composition data of single populations and on mean group compositions among populations, and found that the arboreal langurs basically live in groups with only a single adult males whereas groups of howler and colobus monkeys of comparable size have multiple adult males (Fig. 3). Thus, the hypothesis was supported. Several alternative hypotheses do not account for this pattern. 相似文献
3.
Vigilance often decreases with increasing group size, due to lower predation risk or greater scramble competition for food.
A group size effect on vigilance is seldom seen in primates, perhaps because scanning and feeding often occur simultaneously
or because the distinction between routine and induced vigilance has not been investigated. We analyzed feeding and resting
observations separately while distinguishing between routine and induced scans in four groups of wild ursine colobus monkeys
(Colobus vellerosus) experiencing scramble competition for food and infanticide risk. We used linear mixed-effect models to test the effect of
group size, age–sex class, number of neighbors, number of adult male neighbors, and height in the canopy on scanning rates
(vigilance) with and without evident conspecific threat. Food type was also examined in the feeding models. Perceived predation
risk affected vigilance more than scramble competition for food and infanticide risk. Routine and induced vigilance were greatest
at lower canopy heights during feeding and resting and increased when individuals had fewer neighbors while resting. A group
size effect was found on induced vigilance while resting, but scanning increased with group size, which probably indicates
visual monitoring of conspecifics. Scanning rates decreased while feeding on foods that required extensive manipulation. This
supports the idea that vigilance is relatively cost free for upright feeders when eating food that requires little manipulation,
a common feature of folivore diets. In the presence of threatening conspecific males, close proximity to resident males decreased
individual vigilance, demonstrating the defensive role of these males in the group. 相似文献
4.
Predictions of the model of van Schaik (1989) of female-bonding in primates are tested by systematically comparing the ecology,
level of within-group contest competition for food (WGC), and patterns of social behaviour found in two contrasting baboon
populations. Significant differences were found in food distribution (percentage of the diet from clumped sources), feeding
supplant rates and grooming patterns. In accord with the model, the tendencies of females to affiliate and form coalitions
with one another, and to be philopatric, were strongest where ecological conditions promoted WGC. Group fission in the population
with strong WGC was “horizontal” with respect to female dominance rank, and associated with female-female aggression during
a period of elevated feeding competition. In contrast, where WGC was low, females’ grooming was focused on adult males rather
than other females. Recent evidence suggests that group fission here is initiated by males, tends to result in the formation
of one-male groups, and is not related to feeding competition but to male-male competition for mates. An ecological model
of baboon social structure is presented which incorporates the effects of female-female competition, male-male competition,
and predation pressure. The model potentially accounts for wide variability in group size, group structure and social relationships
within the genus Papio. Socio-ecological convergence between common baboons and hamadryas baboons, however, may be limited in some respects by phylogenetic
inertia.
Received: 22 April 1994/Accepted after revision: 9 December 1995 相似文献
5.
Crickets can autotomize a limb in order to evade predation; however, this autotomy compromises their escape speed and, therefore,
their ability to avoid subsequent predation events. We recorded two measures of predator-avoidance behaviour in field crickets
(Gryllus bimaculatus) exposed to varying levels of predation threat, with the most extreme level leading to autotomy of a limb. Our first measure
of caution was time to emergence from cover, which was affected by perceived predation treatment, with both autotomized males
and females being significantly more cautious than intact individuals. For males (but not females), the presence of a calling
conspecific encouraged earlier emergence. Our second measure of caution was alteration of male calling behaviour. Autotomized
males remained silent for significantly longer time after disturbance than intact males, but there was no difference in call
rate once they had resumed calling, suggesting that behavioural changes were not merely a result of injury response but a
controlled modification of behaviour as a result of autotomy. These data suggest that autotomy in field crickets results in
altered calling behaviour, which was not significantly altered with different acoustic environments. 相似文献
6.
Tradeoffs between courtship, fighting, and antipredatory behavior by a lizard, Eumeces laticeps 总被引:4,自引:0,他引:4
W. E. Cooper Jr. 《Behavioral ecology and sociobiology》1999,47(1-2):54-59
Male fitness in many species depends strongly on social behaviors needed to obtain fertilizations and prevent loss of fertilizations
to other males, but courtship, copulation, and fighting may incur increased risk of predation. When demands for reproductive
and antipredatory behaviors conflict, fitness may be maximized by accepting some degree of risk to enhance reproductive success.
To examine such tradeoffs, I introduced tethered conspecific males or females to adult male broad-headed skinks, Eumeces laticeps, in the field and observed how close they allowed a simulated predator (me) to approach before fleeing, or their latency
to approach an introduced female located at different distances from the predator. When conspecific males were introduced,
isolated and mate-guarding males initiated agonistic behaviors and permitted closer approach than control males, and mate-guarding
males permitted closer approach than isolated males. When females were introduced, both isolated and mate-guarding males courted
the introduced females and isolated males permitted closer approach than did mate-guarding males. These results for introduced
males and females suggest that increasing risk was accepted when reproductive benefits were greater. Latency for isolated
males to approach a conspecific female was greater when the predator was closer to the female, further suggesting sensitivity
to predation risk during a reproductive opportunity. Relationships between reproductive and antipredatory behaviors have been
studied much less than those between feeding and antipredatory behaviors, but this study indicates that animals balance increased
risk of predation with the opportunity to perform several reproductively important behaviors.
Received: 5 March 1999 / Received in revised form: 15 July 1999 / Accepted: 25 July 1999 相似文献
7.
In facultatively eusocial hover wasps, some females leave their natal nests while others choose to stay and become helpers.
We tested whether the decisions of 126 newly emerged females to stay or leave depended on group size: the number of females
already resident on their natal nests. We predicted that females would be less likely to stay in larger groups, where the
benefits of helping are probably smaller and there is a smaller chance of inheriting the dominant position. We also predicted
that unrelated females would be less likely to join larger groups. We manipulated group size by removing residents from nests.
Newly emerged females disappeared from their natal nests at a rate of 2.5% per day, but did not disappear from manipulated
nests at higher rates than controls. Experimentally reducing group size also did not increase the frequency of joiners. Newly
emerged females disappeared at twice the rate of older subordinate females, suggesting the existence of a `leaving window'
early in life. One problem is the difficulty of distinguishing between leaving and death.
Received: 7 July 1998 / Accepted after revision: 25 October 1998 相似文献
8.
Because agonistic behaviour can increase an individual's risk of predation, natural selection should favour individuals that modify their behaviour in the face of predation hazard in ways that maximise fitness. We investigated experimentally the effects of an increase in the apparent risk of predation on male-male competition within mixed-sex shoals of the Trinidadian guppy (Poecilia reticulata). We show that males engaged in significantly fewer aggressive interactions with conspecific males in the presence of a fish predator. However, they continued to court and attempt copulations with females at the same rate irrespective of the level of predation risk. In comparison, under predation hazard, female guppies were less responsive sexually and avoided fewer male copulation attempts. Such predator-mediated changes in male-male agonistic interactions and female sexual responsiveness towards males have important implications for the mode and intensity of sexual selection within populations. 相似文献
9.
Romy Steenbeek Ruben C. Piek Marleen van Buul Jan A. R. A. M. van Hooff 《Behavioral ecology and sociobiology》1999,45(2):137-150
This study examines vigilance as a behavioural indicator of the importance of infanticide risk by comparing the infanticide
avoidance hypothesis with the predation avoidance and mate defence hypotheses for wild Thomas's langurs (Presbytis thomasi) in Sumatra. We found that all individuals were more vigilant in situations of high predation risk, i.e. lower in the trees
and in the absence of neighbours. Females were also more vigilant on the periphery of the group. However, there were variations
in vigilance levels that could not be accounted for by the predation avoidance hypothesis. Males without infants showed higher
levels of vigilance in areas of home range overlap than in non-overlap areas during the early phase of their tenure, strongly
suggesting mate defence. In these areas of home range overlap where Thomas's langur groups can interact, males may attack
females and infants, and so the infanticide risk for males and females with infants is likely to be high in these areas. Only
females with infants, but not males with infants or females without infants, showed higher vigilance levels in overlap areas
than in non-overlap areas; in addition, in overlap areas, females with an infant were more vigilant than females without an
infant, while this was not the case in non-overlap areas. Both females and males with infants were more vigilant high in the
trees than at medium heights in overlap areas but not elsewhere. These findings can only be explained by the infanticide avoidance
hypothesis. In contrast to predator attacks, infanticidal male attacks come from high in the canopy, and only occur in overlap
areas. There was a significant sex difference in vigilance, but males were only more vigilant than females without an infant,
and not more vigilant than females with an infant. We conclude that vigilance varied mainly in relation to the risk of predation
and infanticide. Mate competition only played a role for males during the early phase of their tenure. Predation risk seems
to offer the best explanation for vigilance for all individuals in the absence of infants. Both predation risk and infanticide
risk played a role for females and males with infants.
Received: 4 April 1998 / Accepted after revision: 6 September 1998 相似文献
10.
Gilberto Pasinelli Mathis Müller Michael Schaub Lukas Jenni 《Behavioral ecology and sociobiology》2007,61(7):1061-1074
Studies of animal breeding dispersal have often focused on possible causes, whereas its adaptive significance has received
less attention. Using an information-theoretic approach, we assessed predictions of four hypotheses relating to causes and
consequences of breeding dispersal in a migratory passerine, the red-backed shrike Lanius collurio. As predicted by the reproductive performance hypothesis, probability of breeding dispersal in females (though not in males)
decreased with increasing annual average number of fledglings produced in the past year, but there was no association with
conspecific reproductive performance in either sex. The site choice hypothesis, stating that individuals disperse to improve
breeding site quality, received support in males only, as dispersal probability was positively associated to a measure indicating
low territory quality. The social constraints hypothesis, referring to dispersal in relation to intraspecific interactions,
received little support in either sex. The predation risk hypothesis was hardly supported either. Consequences of dispersal
were marginal in both sexes because neither fledgling production in females, nor territory quality in males improved after
dispersal. In addition, males settled on territories closer to the forest edge than those occupied predispersal, which is
opposite to the prediction of the predation risk hypothesis. We conclude that own reproductive success was the major factor
determining dispersal behavior in females, whereas territory quality and possibly predation risk were most important in males.
Overall, breeding dispersal appeared not to be adaptive in this dense population inhabiting an optimal habitat. 相似文献
11.
In several vertebrate taxa, males and females differ in the proportions of time they individually devote to vigilance, commonly
attributed to sex differences in intra-specific competition or in absolute energy requirements. However, an effect of sex
on collective vigilance is less often studied (and therefore rarely predicted), despite being relevant to any consideration
of the adaptiveness of mixed- vs single-sex grouping. Controlling for group size, we studied the effect of sex on vigilance
in the sexually dimorphic eastern grey kangaroo Macropus giganteus, analysing vigilance at two structural levels: individual vigilance and the group’s collective vigilance. Knowing that group
members in this species tend to synchronise their bouts of vigilance, we tested (for the first time) whether sex affects the
degree of synchrony between group members. We found that females were individually more vigilant than males and that their
vigilance rate was unaffected by the presence of males. Collective vigilance did not differ between female-only and mixed-sex
groups of the same size. Vigilance in mixed-sex groups was neither more nor less synchronous than in single-sex groups of
females, and the presence of males seemed not to affect the degree of synchrony between females. Sixty-six percent of vigilant
acts were unique (performed when no other kangaroo was alert), and only about one unique vigilant act in every three induced
a collective wave of vigilance. The proportions of vigilant acts that were unique were 60% for females but only 46% for males.
However, the sexes differed little in the rates at which their unique vigilant acts were copied. This limited study shows
that the differences in vigilance between male and female kangaroos had no discernible effect upon collective vigilance. 相似文献
12.
Javier delBarco-Trillo M. E. McPhee Robert E. Johnston 《Behavioral ecology and sociobiology》2010,64(8):1247-1253
When females mate with a heterospecific male, they do not usually produce viable offspring. Thus, there is a selective pressure
for females to avoid interspecific mating. In many species, females innately avoid heterospecific males; females can also
imprint on their parents to avoid later sexual interactions with heterospecific males. However, it was previously unknown
whether adult females can learn to discriminate against heterospecific males. We tested the hypothesis that adult females
previously unable to avoid interspecific mating learn to avoid such mating after being exposed to heterospecific males. Syrian
hamster (Mesocricetus auratus) females not previously exposed to Turkish hamster (Mesocricetus brandti) males can discriminate between odors of conspecific and heterospecific males, but they mate with either type of male. However,
when we exposed adult females to both a conspecific male and a heterospecific male through wire-mesh barriers for 8 days,
and then paired them sequentially with the two males, females were more receptive to conspecific males and more aggressive
to heterospecific males. When females were paired with the heterospecific male first and the conspecific male second, no female
was receptive and all were aggressive to heterospecific males. When females were paired with the conspecific male first, only
43% of females were then aggressive toward the heterospecific male. That is, interactions with conspecific males may decrease
a female’s ability to properly avoid heterospecific males. Our study clearly shows for the first time that females can learn
during adulthood to avoid interspecific mating just by being exposed to stimuli from heterospecific males. 相似文献
13.
Summary Preference by females for choosing mates at male aggregations has been hypothesized as the primary selective pressure favoring the formation of leks, but alternative hypotheses account for lek formation without invoking female preference. Observational studies to determine whether male mating success increases with lek size, as predicted under the female preference hypothesis, have produced inconsistent results, possibly due to covariation of lek size with other variables or to male-male or intersexual conflict over lek size. We tested whether females prefer larger leks in a field experiment with ruffs (Philomachus pugnax), a lekking sandpiper, in which male group size, composition, and location were controlled. Wild females chose the larger of two adjacent groups often enough such that males in larger groups had significantly higher per capita rates of female visitation (Table 3). Such behavior would probably lead to higher per male mating rates at larger leks, which is generally considered a necessary condition for female choice to select for lek display (Fig. 2). Lek size in nature will reflect both female preference for larger leks and competition among males, which may favor smaller lek size. All else being equal, however, female ruffs preferred to visit larger groups strongly enough to maintain lekking by males. 相似文献
14.
Using data from 23 populations of Indian langurs (Presbytis entellus), we show that the proportion of one-male groups is a function of the males’ ability to defend groups of females, as predicted
by the monopolisation model of Emlen and Oring (1977). However, we show that in addition to the number of females in the group
and their reproductive synchrony, home range size is also a factor, probably because it affects a male’s willingness to search
for other groups. These variables in turn are shown to be functions of environmental parameters (rainfall volume and seasonality,
and mean ambient temperature) which probably act via the density of resources and refuges in habitats.
Received: 3 March 1994 / Accepted after revision: 24 June 1996 相似文献
15.
T. R. Pope 《Behavioral ecology and sociobiology》2000,48(4):253-267
Evaluation of evolutionary mechanisms proposed to promote cooperative behavior depends on the relative influence of the behavior
on the reproductive success of individuals, the reproductive success of the group in which they interact behaviorally, and
the degree of gene correlation among cooperators. The genetic relationship within cooperative coalitions of female red howler
monkeys was examined for three populations with different densities and growth rates. Patterns of gene correlation change
within coalitions is documented using data from the mitochondrial and nuclear genomes, and long-term census monitoring. Differences
in fecundity and infant survivorship within and between groups of unrelated (rˉ=0) and related (rˉ≥ 0.25) females are compared. Females that emigrate from their natal groups form coalitions with other migrant females. These
coalitions attempt to establish a territory and, once successful in producing offspring, exclude other females from feeding
resources. Females in these coalitions had different mtDNA haplotypes and a genetically estimated mean r of 0, supporting demographic data on emigration patterns indicating that these females rarely have the opportunity to form
coalitions with kin. Patterns of recruitment and rate of matriline development within social groups supported behavioral data
indicating that females actively attempt to promote their own matriline as breeders over that of other females, and that some
matrilines are more successful at this than others. Mean r among females was significantly higher in coalitions established as social groups for several generations (rˉ=0.44). In these groups, females all shared the same mtDNA haplotype, and mtDNA haplotype divergence was significantly higher
between than within groups. Females in coalitions with kin had significantly higher reproductive success than females in unrelated
coalitions in all populations. This difference was not a function of coalition size, number of males, socionomic sex ratio,
or primiparity, although anecdotal evidence suggests that allomothering may compensate for inept new mothers in related coalitions
more often than in unrelated ones. Differences in territory quality could not be ruled out as a potential causal factor in
the saturated populations, but were unlikely in the low-density, growing population. There were substantial differences among
long-established coalitions in overall reproductive output in all three populations, and this was significantly correlated
with the number of breeding females. Increase in coalition size was a function of both group age and the behavioral tolerance
among females. Regardless of the underlying reasons for the patterns observed, reproductive success clearly increases with
degree of gene correlation among females within cooperative coalitions, and coalitions that recruit more daughters produce
more offspring. The nature of the cooperative relationship among group females directly influences both of these outcomes.
This is associated with substantial genetic differentiation among social groups within populations, creating conditions in
which genetic tendencies towards cooperative behavior can become tightly associated with group reproductive success.
Received: 15 September 1999 / Revised: 27 April 2000 / Accepted: 27 May 2000 相似文献
16.
The effects of gregarine parasites,body size,and time of day on spermatophore production and sexual selection in field crickets 总被引:3,自引:0,他引:3
Marlene Zuk 《Behavioral ecology and sociobiology》1987,21(1):65-72
Summary In laboratory experiments measuring the rate of spermatophore production in the field crickets Gryllus veletis and G. pennsylvanicus by confining single males with a conspecific female, 0–10 spermatophores were produced by each male within 24 h. The number of spermatophores produced was unrelated to a male's body size, but was significantly negatively correlated with the natural levels of gregarines, a protozoan gut parasite, in the males. Spermatophore production in the laboratory peaked between 0600 and 1000 h, as did the proportion of courtship songs given by male crickets in the field, suggesting that mating may occur more frequently in the morning. When single males were placed in jars with two conspecific females, 49% transferred spermatophores to both females, whereas 51% of males only gave spermatophores to one of the females. The results support the hypothesis that parasites are important in sexual selection, and are used to propose a new interpretation of post-copulatory guarding in crickets. 相似文献
17.
Olivia Gregorio Emma L. Berdan Genevieve M. Kozak Rebecca C. Fuller 《Behavioral ecology and sociobiology》2012,66(10):1429-1436
Reinforcement occurs when reduced hybrid fitness leads to the evolution of a stronger prezygotic isolation. Populations sympatric with closely related species, where hybridization occurs, are predicted to have stronger mate preferences than allopatric populations. The reinforcement of male mate preference is thought to be rarer than the reinforcement of female preference, but this inference may be biased by the lack of studies on male preference. We tested male mate preferences from sympatric and allopatric populations of two closely related species of killifish: Lucania goodei and Lucania parva. We found that sympatric males had greater preferences for conspecific females than allopatric males. Furthermore, conspecific preferences in allopatric populations were weakest when these populations were geographically distant (>50?km) from those of heterospecifics. Our data suggest that reinforcement has contributed to male conspecific preference and speciation in Lucania. 相似文献
18.
Summary Populations of the Trinidad guppy range from areas with high levels of predation by other species of fish to areas with little or no piscine predation. Previous studies have shown that variation among populations in male coloration can be explained by a balance between female preference for brighter males and natural selection against bright males. High levels of male courtship activity may also increase both predation risk and mating success. Therefore, in high-predation areas, females that mate with males that court frequently as well as those that choose bright males would presumably produce male offspring with low survivorship. Consistent with this variation in natural selection, we observed that females from high-predation populations were less likely to choose bright and frequently courting males than females from low-predation populations. This result supports the hypothesis that female preference is evolving as a character genetically correlated with the preferred male character, in which case higher levels of natural selection acting against the male character should be related to lower levels of female preference. 相似文献
19.
Ebensperger LA Sobrero R Quirici V Castro RA Tolhuysen LO Vargas F Burger JR Quispe R Villavicencio CP Vásquez RA Hayes LD 《Behavioral ecology and sociobiology》2012,66(2):261-274
Intraspecific variation in sociality is thought to reflect a trade-off between current fitness benefits and costs that emerge from individuals' decision to join or leave groups. Since those benefits and costs may be influenced by ecological conditions, ecological variation remains a major, ultimate cause of intraspecific variation in sociality. Intraspecific comparisons of mammalian sociality across populations facing different environmental conditions have not provided a consistent relationship between ecological variation and group-living. Thus, we studied two populations of the communally rearing rodent Octodon degus to determine how co-variation between sociality and ecology supports alternative ecological causes of group living. In particular, we examined how variables linked to predation risk, thermal conditions, burrowing costs, and food availability predicted temporal and population variation in sociality. Our study revealed population and temporal variation in total group size and group composition that covaried with population and yearly differences in ecology. In particular, predation risk and burrowing costs are supported as drivers of this social variation in degus. Thermal differences, food quantity and quality were not significant predictors of social group size. In contrast to between populations, social variation within populations was largely uncoupled from ecological differences. 相似文献
20.
The number of males in primate social groups: a comparative test of the socioecological model 总被引:2,自引:2,他引:0
Charles L. Nunn 《Behavioral ecology and sociobiology》1999,46(1):1-13
As applied to polygynous mammals, the socioecological model assumes that environmental risks and resources determine the
spatial and temporal distribution of females, which then sets male strategies for monopolizing fertile matings. The effects
of female spatial distribution (i.e., female number) and temporal overlap (female mating synchrony) have been examined in
comparative studies of primates, but the relative influence of these two factors on male monopolization potential (the number
of males) remains unclear. One particular problem is that female synchrony is more difficult to estimate than female number.
This paper uses multivariate statistical methods and three independent estimates of female synchrony to assess the roles of
spatial and temporal effects in the context of a phylogenetically corrected dataset. These analyses are based on sensitivity
analyses involving a total of four phylogenies, with two sets of branch length estimates for each tree, and one nonphylogenetic
analysis in which species values are used (because male behavior may represent a facultative response to the distribution
of females). The results show: (1) that breeding seasonality predicts male number (statistically significant in six out of
nine sensitivity tests); (2) that expected female overlap, after controlling for female group size using residuals, also accounts
for the number of males in primate groups (significant in eight out of nine tests), and (3) that actual estimates of female
mating synchrony predict male number, again after correcting for female group size (significant in five out of nine tests).
Nonsignificant results are in the predicted direction, and female group size is significant in all statistical tests. These
analyses therefore demonstrate an independent influence of female temporal overlap on male monopolization strategies in mammalian
social systems.
Received: 24 July 1998 / Received in revised form: 5 February 1999 / Accepted: 7 February 1999 相似文献