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1.
Theory predicts that frequent dyadic association should promote cooperation through kin selection or social tolerance. Here
we test the hypothesis that sex differences in the strength and stability of association preferences among free-ranging chimpanzees
conform to sex differences in cooperative behavior. Using long-term data from the Kanyawara chimpanzee (Pan troglodytes schweinfurthii) community (Kibale National Park, Uganda), we calculated indices of intra-sexual dyadic association over a 10-year period.
We found that (1) male–male dyads had significantly stronger association indices than female–female dyads, (2) the pattern
of association preferences in both sexes changed little over the entire study period, and (3) when comparing periods with
different alpha males, changes in association strength were more frequent among males. These results demonstrate that both
the strength and stability of association patterns are important components of social relationships. Male chimpanzees, which
are characterized by frequent cooperation, had association preferences that were both strong and stable, suggesting that forming
long-term bonds is an important dominance strategy. However, the fact that male association patterns were sensitive to upheaval
in the male dominance hierarchy suggests that males also take advantage of a changing social climate when choosing association
partners. By contrast, the overall strength of female associations was relatively weak. Female association preferences were
equally stable as males’; however, this reflected a dyad’s tendency to be found in the same party rather than to associate
closely within that party. Therefore, in this community, female association patterns appear to be more a consequence of individual
ranging behavior rather than a correlate of cooperation. 相似文献
2.
While many theories exist on the evolution of the sexual swelling signal in female primates, the significance of the very large and variable swellings found in some catarrhine primates is still debated. As suggested by Pagel [(1994) Anim Behav 47:1333–1341], these exaggerated and costly signals have the potential to provide information about differential female reproductive quality to males. While Domb [(2000) Department of Anthropology, Harvard University, Cambridge] and Domb and Pagel [(2001) Nature 410:204–206] propose that swellings serve to reliably indicate between-female fitness differences, we hypothesize that they may indicate current reproductive cycle quality, within or between females. This study examines the between-cycle relationship between ovarian function, gauged via fecal steroid analysis, and absolute size of sexual swellings, yielded through photogrammetric methods. Fourteen cycles from eight captive, group-living chimpanzees (Pan troglodytes) exhibited considerable variability both in ovarian steroid levels and maximum sexual swelling size. Nearly all measures of a female's maximal swelling in a cycle correlated with early follicular and early luteal estradiol averages and the duration of luteal progesterone elevation. Swelling area was also correlated with late follicular estradiol. Given past evidence that such measures of ovarian function predict conceptive success, these data strongly suggest that swellings could convey information to competing males about the fecundability of a potential mate.Communicated by C. Nunn 相似文献
3.
Most social primates live in cohesive groups, so travel paths inevitably reflect compromise: decision processes of individuals
are obscured. The fission–fusion social organisation of the chimpanzee, however, allows an individual's movements to be investigated
independently. We followed 15 chimpanzees (eight male and seven female) through the relatively flat forest of Budongo, Uganda,
plotting the path of each individual over periods of 1–3 days. Chimpanzee movement was parsed into phases ending with halts
of more than 20 min, during which individuals fed, rested or engaged in social activities. Males, lactating or pregnant females
and sexually receptive females all travelled similar average distances between halts, at similar speeds and along similarly
direct beeline paths. Compared to lactating or pregnant females, males did travel for a significantly longer time each day
and halted more often, but the most striking sex differences appeared in the organisation of movement phases into a day's
path. After a halt, males tended to continue in the same direction as before. Lactating or pregnant females showed no such
strategy and often retraced the preceding phase, returning to previously visited food patches. We suggest that female chimpanzee
movements approximate an optimal solution to feeding requirements, whereas the paths of males allow integration of foraging
with territorial defence. The ‘continually moving forwards’ strategy of males enables them to monitor their territory boundaries—border
checking—whilst foraging, generally avoiding the explicit boundary patrols observed at other chimpanzee study sites. 相似文献
4.
Ivo H. Machatschke Barbara E. Bauer Cornelia Schrauf John Dittami Bernard Wallner 《Behavioral ecology and sociobiology》2008,62(8):1341-1350
Polygynous mating systems can inflict considerable costs on males, often causing the emergence of alternative mating strategies
to ensure reproductive success. These strategies can lead to different morphs of color, size, or behavior. The present work
was done on guinea pigs, a polygynous rodent species. Some males can show a reduced readiness for conflict, perhaps employing
an alternative mating strategy. To test this hypothesis, a two-stage experiment was set up, with males (N = 16) and females (N = 16) initially living in isosexual groups. Visual and olfactory contact was possible through a wire mesh. Male agonistic
behavior was observed for 15 days, confirming the existence of less-conflict-involved (LCI, N = 7) and more-conflict-involved males (MCI, N = 9). Significant differences were found for a conditional parameter, body mass, and a morphometric one, testis width: LCI
consistently surpassed MCI. Hormonally, cortisol was comparable, while testosterone was distinctly higher in MCI. Next, males
and females were joined and observed for further 24 days. Males initially lost weight but reached original mass towards the
end of the experiment. Testis width patterns were similar. Again, LCI had higher body mass. Cortisol was comparable, but testosterone
release 3 days after merging was significantly higher in LCI. Behaviorally, LCI exhibited significantly less male–male aggression
and more socio-sexual behavior than MCI. The former were more successful, with 57% capable of accessing females, in contrast
to 11% of MCI. The existence of two distinct behavioral phenotypes in guinea pig males suggests that different reproductive
strategies may exist in this species. 相似文献
5.
A common explanation for hunting in groups is that doing so yields a greater per capita caloric benefit than hunting solitarily.
This is logical for social carnivores, which rely exclusively on meat for energy, but arguably not for omnivores, which obtain
calories from either plant or animal matter. The common chimpanzee, Pan troglodytes, is one of the few true omnivores that regularly hunts in groups. Studies to date have yielded conflicting data regarding
the payoffs of group hunting in chimpanzees. Here, we interpret chimpanzee hunting patterns using a new approach. In contrast
to the classical assumption that hunting with others maximizes per capita caloric intake, we propose that group hunting is
favored because it maximizes an individual’s likelihood of obtaining important micronutrients that may be found in small quantities
of meat. We describe a mathematical model demonstrating that group hunting may evolve when individuals can obtain micronutrients
more frequently by hunting in groups than by hunting solitarily, provided that group size is below a certain threshold. Twenty
five years of data from Gombe National Park, Tanzania are consistent with this prediction. We propose that our ‘meat-scrap’
hypothesis is a unifying approach that may explain group hunting by chimpanzees and other social omnivores. 相似文献
6.
Territoriality should lead to strict dominance, as territory holders typically control access to resources and exclude others
from their use. In feeding territories, dominance should be reflected in foraging success and ultimately in reproduction differences;
however, these successive links have rarely been made explicit. Therefore, we investigated a population of brown skuas Catharacta antarctica lonnbergi, in which only part of the breeding population occupied feeding territories within penguin colonies. We identified the dominance
hierarchy and determined the foraging success of the participants in fights for access to penguin carcasses within the territories.
Furthermore, we monitored offspring growth from parents with and without feeding territories. Our results indicated a clear
dominance hierarchy with territorial birds in their own territory dominating over territorial breeders from other territories,
non-territorial breeders and non-breeding birds. However, territory owners could not completely exclude others from access
to food. Foraging success was positively related to dominance scores: The dominant territory owners received 63% of a carcass,
whereas non-territorial pairs could get less than 10%. The link between foraging success and offspring development was less
clear: Although male chicks of non-territorial parents suffered from lower growth rates and, thus, delayed fledging, there
were no such differences in female chicks. Territoriality in skuas did not imply a complete occupation of food, but guaranteed
optimal growth conditions for offspring. Non-territorial individuals were forced to search for alternative resources, and
the restricted access to the preferred food resulted in inferior conditions for offspring development, making this foraging
strategy less rewarding. 相似文献
7.
Most studies suggest that during times of nutritional stress, an animal faced with two foraging choices should follow a risk-prone
strategy, choosing the option with highest payoff variance. This “scarcity/risk” hypothesis was developed to account for the
foraging patterns of small animals with high metabolic rates susceptible to the threat of starvation. In this paper, we propose
that animals should also be risk-prone when their diet quality is particularly high, far exceeding that which is needed to
survive. Under these circumstances, the costs of experiencing a low or negative payoff can easily be recouped. We suggest
that large-bodied omnivores are most likely to adopt this “abundance/risk” strategy. We investigate this question among wild
chimpanzees (Pan troglodytes) that choose between a risk-averse strategy of feeding on plant material and a risk-prone strategy of hunting red colobus
monkeys. Using 14 years of data on the Kanyawara chimpanzees of Kibale National Park, Uganda, we find strong evidence that
chimpanzees follow the “abundance/risk” strategy. Both hunting rate (hunts/100 observation hours) and the probability of hunting
upon encountering red colobus monkeys were positively correlated with seasonal consumption of ripe drupe fruits, a class of
preferred food associated with elevated reproductive performance by females. Critically, these results remained statistically
significant after controlling for the potentially confounding effects of male chimpanzee party size and the presence of sexually
receptive females. These findings suggest that the relationship between risk-sensitive foraging and diet quality depends upon
the daily probability of starvation, the number of alternative foraging strategies, and the degree to which diet quality satisfies
an animal’s nutritional requirements. 相似文献
8.
The influence of abiotic factors on the establishment and success of invasive species is often difficult to determine for
most marine ecosystems. However, examining this relationship is critical for predicting the spread of invasive species and
predicting which habitats will be most vulnerable to invasion. Here we examine the mortality and physiological sensitivity
to salinity of adult colonies of the colonial ascidians Botryllus schlosseri and Botrylloides violaceus. Adult colonies of each species were exposed to abrupt changes in salinity (5, 10, 15, 20, 25, 30 psu) in the laboratory.
Salinity ranges used in the laboratory corresponded with those of the field distributions of B. violaceus and B. schlosseri in the Great Bay Estuary, NH. Heart rate was used as a proxy for health to assess the condition of individual colonies. Heart
rates were monitored daily for approximately 2 weeks. Results revealed that both species experienced 100% mortality after
1 day at 5 psu and that their heart rates declined with decreasing salinity. Heart rates of B. schlosseri remained consistent between 15 and 30 psu and slowed at 10 psu. Heart rates of B. violaceus remained constant between 20 and 30 psu, but slowed at 15 psu. These laboratory results corresponded to the distribution
of these species in estuaries, indicating salinity is a key factor in the distribution and dominance of B. schlosseri and B. violaceus among coastal and estuarine sites. Furthermore, physiological differences to salinity were found between colonies of B. schlosseri in the Venetian Lagoon and colonies in Portsmouth Harbor, suggesting adaptation to environmental variables. 相似文献
9.
Morphological and behavioural traits can serve as anti-predator defence either by reducing detection or recognition risks,
or by thwarting initiated attacks. The latter defence is secondary and often involves a ‘startle display’ comprising a sudden
release of signals targeting more than one sensory modality. A suggested candidate for employing a multimodal defence is the
peacock butterfly, Inachis io, which, by wing-flicking suddenly, produces sonic and ultrasonic sounds and displays four large eyespots when attacked. The
eyespots make small birds retreat, but whether the sounds produced thwart predator attacks is largely unknown. Peacocks hibernate
as adults in dark wintering sites and employ their secondary defence upon encounter with small rodent predators during this
period. In this study, we staged predator–prey encounters in complete darkness in the laboratory between wild mice, Apodemus flavicollis and Apodemus sylvaticus, and peacocks which had their sound production intact or disabled. Results show that mice were more likely to flee from sound-producing
butterflies than from butterflies which had their sound production disabled. Our study presents experimental evidence that
the peacock butterfly truly employs a multimodal defence with different traits targeting different predator groups; the eyespots
target birds and the sound production targets small rodent predators. 相似文献
10.
The genetic population structures of Atlantic northern bluefin tuna ( Thunnus thynnus thynnus) and albacore ( T. alalunga) were examined using allozyme analysis. A total of 822 Atlantic northern bluefin tuna from 18 different samples (16 Mediterranean, 1 East Atlantic, 1 West Atlantic) and 188 albacore from 5 samples (4 Mediterranean, 1 East Atlantic) were surveyed for genetic variation in 37 loci. Polymorphism and heterozygosity reveal a moderate level of genetic variability, with only two highly polymorphic loci in both Atlantic northern bluefin tuna ( FH* and SOD- 1*) and albacore ( GPI- 3* and XDH*). The level of population differentiation found for Atlantic northern bluefin tuna and albacore fits the pattern that has generally been observed in tunas, with genetic differences on a broad rather than a more local scale. For Atlantic northern bluefin tuna, no spatial or temporal genetic heterogeneity was observed within the Mediterranean Sea or between the East Atlantic and Mediterranean, indicating the existence of a single genetic grouping on the eastern side of the Atlantic Ocean. Very limited genetic differentiation was found between West Atlantic and East Atlantic/Mediterranean northern bluefin tuna, mainly due to an inversion of SOD- 1* allele frequencies. Regarding albacore, no genetic heterogeneity was observed within the Mediterranean Sea or between Mediterranean and Azores samples, suggesting the existence of a single gene pool in this area. 相似文献
11.
To balance advantages and disadvantages of group living, some species have fission-fusion social systems in which members of the same group form frequently changing subgroups. This allows flexible responses of group size to external conditions while at the same time retaining group stability. In chimpanzees, subgroup (party) size and composition depend mainly on the presence of receptive females, food availability and the activity of the party. Here we analyse the extent to which fission-fusion parameters are influenced by changes of demographic variables like community size and composition. Data were collected from a habituated West African chimpanzee community (Taï forest, Côte dIvoire) over 10 years, during which total community size decreased from 51 to 21, and the number of adult males decreased from 9 to 2. Taï chimpanzees are highly gregarious, as they spend more than 80% of their time with unrelated conspecifics. With decreasing community size, party size, party duration and male-female association increased. Neither activity nor the presence of receptive females or feeding competition could explain the observed changes in grouping patterns. Thus, the decrease in community size led to an increase of party cohesion and also enhanced cohesiveness between the sexes, while general sociality remained unchanged. Therefore, our data support the notion that small communities are more cohesive and have a less flexible fission-fusion system.Communicated by D. Watts 相似文献
12.
The immunocompetence handicap hypothesis (ICHH) suggests that dominance signals are costly because their development is controlled by testosterone, which is immunosuppressive. Signal control therefore links an increased disease risk with a high quality signal. The chest bib of the house sparrow, Passer domesticus, is a signal known to be related to dominance and under control of testosterone levels. We experimentally manipulated testosterone in male sparrows during the breeding season and again independently during the post-breeding period to test whether variation in levels of testosterone could cause variation in levels of immunocompetence. There was no effect of testosterone manipulation on the cell-mediated response of birds to phytohaemagglutinin injection, nor did testosterone levels appear to affect either white blood cell ratios or red blood cell counts. In contrast, both breeding season and post-breeding season testosterone levels had significant effects upon the humoral response of the birds to sheep red blood cell injections. However, whilst testosterone during the breeding season appeared to act immunosuppressively, the role of post-breeding levels is less clear. In concordance with a previous study, there was an indication that corticosterone is involved in mediating the immunosuppressive effects of testosterone. The strength of the secondary humoral response and the cell-mediated response were negatively related suggesting the possibility of a trade-off between the different arms of the immune system. These results provide some support for the ICHH as a mechanism promoting the evolution of costly badges of status, although the results question whether the immunosuppressive cost can be mediated by testosterone at the time of badge development.Communicated by W.A.Searcy 相似文献
13.
This study devised a staging system for, and monitored, the gonad development of the limpet species Patella vulgata and Patella ulyssiponensis on the South West coast of Ireland using histological techniques. Maturation began in the males of both species in January
and in the females it began in March. There was no statistical difference in gonad development between sexes and between species.
Spawning in the male P. vulgata occurred from September to December 2003 and in September and October 2004. In female P. vulgata spawning occurred from October to December 2003, no spawning of females was observed in 2004. In male P. ulyssiponensis spawning occurred in November and December 2003 and from September 2004 to December 2004. Spawning was observed from November
2003 to January 2004 and in September 2004 in female P. ulyssiponensis. Sex ratios also varied between the species and between months sampled. Nevertheless more males were observed in both species. 相似文献
14.
Akiko Matsumoto-Oda Miya Hamai Hitosige Hayaki Kazuhiko Hosaka Kevin D. Hunt Eiiti Kasuya Kenji Kawanaka John C. Mitani Hiroyuki Takasaki Yukio Takahata 《Behavioral ecology and sociobiology》2007,61(5):661-668
Although estrous synchrony has been reported in a number of mammalian species, most often among primates, methodological and
analytical problems make it difficult to interpret these results. We developed a novel estrous synchrony index and employed
a randomization procedure to analyze long-term observations of female chimpanzee (Pan troglodytes schweinfurthii) estrous cycles at the Mahale Mountains National Park, Tanzania. Our results revealed that female chimpanzees at Mahale avoid
synchronizing their estrous periods with each other. We also found that birthrates decreased as the breeding sex ratio increased.
We suggest that estrous asynchrony decreases female–female competition for mates. Asynchrony may also reduce the potential
for male sexual coercion by nonpreferred mating partners. 相似文献
15.
Life-history features of the sympatric amphipods Themisto pacifica and T. japonica in the western North Pacific were analyzed based on seasonal field samples collected from July 1996 through July 1998, and data from laboratory rearing experiments. T. pacfica occurred throughout the year, with populations peaking from spring to summer. In contrast, T. japonica were rare from autumn to early winter, but became abundant in late winter to spring. Mature T. pacifica females and juveniles occurred together throughout the year, indicating year-round reproduction. Mature T. japonica females were observed only in spring, and juveniles occurred irregularly in small numbers, suggesting limited, early-spring reproduction in this study area. Size composition analysis of T. pacifica identified a total of eight cohorts over the 2 years of the study. Due to the smaller sample size and rarity of mature females (>9.6 mm) and males (>7.1 mm), cohort analyses of T. japonica were not comparable. Laboratory rearing of specimens at 2°C, 5°C, 8°C and 12°C revealed that a linear equation best expressed body length growth by T. pacifica, while a logistic equation best expressed body length growth by T. japoncia. Combining these laboratory-derived growth patterns with maturity sizes of wild specimens, the minimum and maximum generation times of females at a temperature range of 2–12°C were computed as 32 days (12°C) and 224 days (2°C), respectively, for T. pacifica, and 66 days (12°C) and 358 days (2°C), respectively, for T. japonica. The numbers of eggs or juveniles in females marsupia increased with female body length and ranged from 23 to 64 for T. pacifica and from 152 to 601 for T. japonica. Taking into account the number of mature female instars, lifetime fecundities were estimated as 342 eggs for T. pacifica and 1195 eggs for T. japonica. Possible mechanisms for the coexistence of these two amphipods in the Oyashio region are also discussed.Communicated by O. Kinne, Oldendorf/Luhe 相似文献
16.
The genetic structure and phylogeography of the brown seaweed Sargassum horneri/filicinum complex in Japan were studied based on the mitochondrial cox3 haplotype. The cox3 haplotypes found were divided into three clades in a statistical parsimony network, among which there were large numbers
of steps. Contrary to the reported large amount of drifting S. horneri along the Japanese coast, the three clades were dividedly distributed on the Japanese coast: the northern Pacific, the central
Pacific, and western Japan. The western Japan S. horneri had haplotypes that were phylogenetically closer to those of S. filicinum than to the northern and central Pacific S. horneri populations. The S. filicinum populations were included within the western Japan clade and grouped together with the S. horneri samples from western Japan. Taken together with the unstable morphological diagnosis, this result suggests that S. filicinum should be reduced into a synonymy of S. horneri. The TMRCA analysis suggested that the divergence time of each clade may go back to the last interglacial period and a skyline
plot suggested that the last glacial maximum had only a small effect on the population size of S. horneri. The geographic subdivision of the three groups, in spite of a large amount of drifting mats, suggests a limited contribution
of drifting mats to gene flow on a large geographic scale. On a small geographic scale, a small number of haplotypes were
shared between S. horneri-type and S. filicinum-type populations. This result suggests that populations of these two types are partially, though not completely, isolated
from each other, possibly by selfing in S. filicinum-type populations or by a difference in peak reproduction. 相似文献
17.
18.
The mantle of the pearl oyster Pinctada fucata was adopted for the proliferation profile study in our work and a proliferation hot spot was found in the outer epithelia
of mantle central zone using the BrdU immunohistochemistry method. This result contradicts the previous research that the
mantle has numerous growth centers all over the mantle epithelium, with the same proliferation activity throughout the whole
mantle outer epithelial cells. This is the first report on the different proliferation features on the whole mantle where
Alcian Blue/PAS staining analysis and ultrastructural observation with the aid of transmission electron microscope (TEM) demonstrated
distinct features of the epithelium in four different regions of the mantle. Results from the present investigation displayed
that in the outer epithelium of the marginal zone in mantle outer fold, organelles such as mitochondria and endoplasmic reticulum
(ER) were well-developed and double membrane bounded vesicles were present; in the outer epithelia of mantle central zone,
stem-like cells with a high ratio of nucleus to cytoplasm and comparatively undeveloped organelles were detected. Together
with the observations of the cell proliferation profile of different regions of the mantle, a hypothetic model for the proliferation
and differentiation of the pearl oyster’s mantle is proposed: there exists a proliferation “hot spot” in the outer epithelial
cells of central zone and the proliferation ability decreases progressively from this “hot spot” towards the marginal zone;
the whole mantle’s differentiation occurs continuously with its growth and the direction is from the proliferation ‘hot spot’
(central zone) towards the marginal zone. Furthermore, another interesting result was found when the proliferation rate was
investigated together with the tidal rhythm: the proliferation activity was found to be closely correlated with the tidal
rhythm, indicating that the mantle outer epithelia’s proliferation rhythm might be the impetus of the shell’s daily growth
bands. 相似文献
19.
Among the diverse patterns of energy allocation to the offspring of gastropods, the presence of egg capsules to protect embryos
is common. Females of the edible snail Zidona
dufresnei attach egg capsules to hard substrates in shallow Argentine Patagonian waters (40°45′S, 64°56′W) during spring-summer. Embryonic
development takes about 30 days at 22°C. In this study, three likely capsule predator species and the marks left by each on
egg capsule walls were identified in laboratory experiments in February 2010. Abundances of predators and egg capsules with
evidence of predation were assessed in the field in the summers of 2010 and 2011. Under laboratory conditions (N = 10 replicates per treatment and control), the predation rate by the chiton Chaetopleura
isabellei was the highest (up to 90%), followed by the gastropod Tegula
patagonica and the crab Neohelice
granulata (~20% each). Nearly 60% of 41 capsules found in the field showed signs of predation. According to the marks identified in
the laboratory, C. isabellei was responsible for 79% of this predation, and T. patagonica for the rest. Predation appears to be important during the encapsulated early life and could be an agent for selecting for
resistant capsule walls and a relatively shorter development time. 相似文献