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1.
In temperate-zone birds, testosterone (T) influences male behavior during the breeding season. The elevation of plasma levels of T to a breeding baseline is necessary for basic reproductive behaviors, but it is still unclear whether variation in T levels above this critical threshold influences the intensity of these behaviors. Such a relationship between T and sexually selected traits is a critical assumption of the immunocompetence handicap hypothesis. We here experimentally elevated T levels in blue-tit males above the natural mean (T-males) during the period of nest building and egg laying, without manipulating hormone levels during chick feeding. T-males neither interacted more often with other males, nor did they respond more aggressively to a dummy intruder, compared to males with control implants. T-males did not guard their social mates more closely, but they were more likely to interact with potential extra-pair mates. Females mated to T-males did not change their behavior during egg laying and the treatment did not significantly affect male and female feeding rates. Despite this, nests of T-males produced larger and heavier fledglings in one study year. Our observations suggest that T levels above the natural mean during the mating period do not increase aggressive or territorial behavior in male blue tits. However, if females perceived T-males as high-quality mating partners, superior offspring development in nests of T-males might be caused by higher maternal investment. Hence, male behaviors involved in mate attraction may have been influenced by T levels above the natural mean.Communicated by R. Gibson 相似文献
2.
Juliana Valencia Elena Solís Gabriele Sorci Carlos de la Cruz 《Behavioral ecology and sociobiology》2006,60(3):399-404
In cooperatively breeding species, helpers may contribute to the success of the brood by increasing the number of independent offspring, but also, they may affect offspring condition and, hence, their survival and recruitment into the breeding population. This second type of benefits is rarely included in theoretical models or assessed in field studies. Immune response is a good proxy of individual quality and fitness, and there is good evidence that the performance of the immune system of chicks during the nestling phase is related to their chances of survival and future reproduction. However, no study has so far explored whether helpers at the nest might contribute to enhance immune functioning of nestlings in species with a cooperative breeding system. Here we investigate this issue in the azure-winged magpie (Cyanopica cyanus) and found for the first time a positive correlation between the number of helpers at nest and the cell-mediated immune response of nestlings. This effect was not explained by a general improvement of body condition of chicks because it was independent of individual variation in body mass or tarsus length. Our results suggest that helping can have subtle effects on the quality of offspring that may influence their survival and future reproduction. 相似文献
3.
James P. Higham Michael Heistermann Dario Maestripieri 《Behavioral ecology and sociobiology》2013,67(1):19-30
Social status primarily determines male mammalian reproductive success, and hypotheses on the endocrinology of dominance have stimulated unprecedented investigation of its costs and benefits. Under the challenge hypothesis, male testosterone levels rise according to competitive need, while the social stress hypothesis predicts glucocorticoid (GC) rises in high-ranking individuals during social unrest. Periods of social instability in group-living primates, primarily in baboons, provide evidence for both hypotheses, but data on social instability in seasonally breeding species with marked social despotism but lower reproductive skew are lacking. We tested these hypotheses in seasonally breeding rhesus macaques on Cayo Santiago, Puerto Rico. We documented male fecal GC and androgen levels over a 10-month period in relation to rank, age, natal status, and group tenure length, including during a socially unstable period in which coalitions of lower ranked males attacked higher ranked males. Androgen, but not GC, levels rose during the mating season; older males had lower birth season levels but underwent a greater inter-season rise than younger males. Neither endocrine measure was related to rank except during social instability, when higher ranked individuals had higher and more variable levels of both. High-ranking male targets had the highest GC levels of all males when targeted and also had high and variable GC and androgen levels across the instability period. Our results provide evidence for both the challenge and social stress hypotheses. 相似文献
4.
Allison C. Alberts Jeffrey M. Lemm Andrew M. Perry Lisa A. Morici John A. Phillips 《Behavioral ecology and sociobiology》2002,51(4):324-335
In small, insular populations, behavioral patterns that lead to increased variance in individual reproductive success can
accelerate loss of genetic variation. Over a 1-year period, we documented behavior and hormone levels in a breeding group
of adult Cuban iguanas (Cyclura
nubila) at Guantánamo Bay. Male dominance was associated with body and head size, display behavior, testosterone levels, home-range
size, and proximity to females. Based on their success in agonistic encounters, we ranked males in a linear dominance hierarchy.
During the subsequent breeding season, we conducted a removal experiment in which the five highest-ranking males were temporarily
relocated from the study site. Although we were unable to assess reproductive success directly, previously lower-ranking males
assumed control of vacated territories, won more fights, and increased their proximity to females in the absence of the dominant
males. When it results in greater mating opportunities for otherwise socially suppressed individuals, temporary alteration
of local social structure may help limit erosion of genetic variation in small, insular populations.
Electronic Publication 相似文献
5.
Kathleen E. Hunt Thomas P. Hahn John C. Wingfield 《Behavioral ecology and sociobiology》1999,45(5):360-369
In males of socially monogamous birds, plasma testosterone (T) typically declines to low levels during the parental phase.
Studies on multiple-brooded species indicate that high T may be incompatible with high-quality paternal care. The length of
the breeding season may affect the costs and benefits of high T and its effect on paternal care. We studied the effect of
experimentally elevated T on paternal care in a single-brooded species with a short breeding season, the Lapland longspur
(Calcarius lapponicus). We monitored T levels and parental behavior in 16 males with subcutaneous T implants, 14 males with empty implants, and
14 unimplanted males. We videotaped nests when nestlings were 2–3 days old and again at 4–5 days. T males with 2- to 3-day-old
young visited nests and fed young less often than control males, and the mates of the T males compensated with elevated visits
and feedings. However, when nestlings were 4–5 days old, T males visited their nests at normal rates – though feeding movements
remained below normal – and T females visited and fed at normal rates. Nestling mass and nest success were similar in both
groups. Overall, high T suppresses paternal care in Lapland longspur males. The partial improvement of paternal care when
nestlings are older, despite high T, may be related to the short 6-week breeding season of this arctic species, and the consequently
reduced benefits of sexual behavior late in the breeding season.
Received: 2 February 1998 / Accepted after revision: 2 November 1998 相似文献
6.
Lindsey Swierk Sean P. Graham Tracy Langkilde 《Behavioral ecology and sociobiology》2014,68(11):1761-1768
Iteroparous species maximize lifetime reproductive fitness by balancing current and future reproductive investments. In order to maximize fitness in the face of social or environmental heterogeneity, individuals of the same species may vary in whether they prioritize current reproductive opportunity or sacrifice immediate reproduction in order to prioritize survival and future reproductive potential. Glucocorticoid (GC) secretion plays an important role in mediating this trade-off by promoting behavioral and physiological responses associated with survival, often at the expense of nonessential (e.g., reproductive) functions. We used wood frogs (Lithobates sylvaticus [Rana sylvatica]) to test whether males and females differed in their (a) physiological response (plasma corticosterone [CORT] concentration) to standardized handling stress—a proxy for predation threat—and (b) performance of reproductive behaviors that may enhance their conspicuousness to predators. We also tested whether levels of male competition influenced sex differences in these factors, as more intense competition may require males to devote more time to risky reproductive behaviors. We found that females had lower baseline CORT but exhibited a significantly greater CORT response to a stressor and spent less time performing potentially risky behavior (surface floating) than did males. These sex differences were consistent across different levels of male mating competition. Our results reveal that during breeding, males and females may differentially respond to stressors and perform risk-prone behaviors, despite facing the same extreme breeding constraints, providing new insight into the survival-reproduction trade-off of explosively breeding species. 相似文献
7.
In the cooperatively breeding red-cockaded woodpecker (Picoides borealis), male helpers are subordinate to male breeders and do not mate with females, even when unrelated to the breeding female
within their group or through extra-group matings, yet exhibit reproductive hormone profiles similar to those of breeders.
We investigated whether reproduction might be suppressed in helper males via high levels of the stress hormone corticosterone.
We also examined effects of group size and season on corticosterone levels by comparing baseline and maximal plasma levels
of corticosterone between helper males and breeding males, and among helper males and breeders of both sexes living in groups
of different sizes throughout the reproductive cycle. We also measured plasma levels of estrogen, progesterone, and testosterone
to examine other potential hormonal differences between helpers and breeders. Male status did not explain variation in any
hormones; therefore, our data do not support the hypothesis that helper males are reproductively suppressed via corticosterone
or the other hormones investigated. However, the presence of two or more helper males in a group tended to reduce baseline
corticosterone in breeding and helper males, but not breeding females, suggesting that helper males reduce parental effort
of other male group members. Seasonally, maximal corticosterone peaked during the nestling provisioning phase for breeding
and helper males, but not breeder females, suggesting that males show an increased response to stressors posing a potential
threat to survival of offspring. 相似文献
8.
Is helping a beneficial learning experience for red-cockaded woodpecker (Picoides borealis) helpers?
Several hypotheses have been suggested to explain the evolution and maintenance of helping behavior in cooperatively breeding
birds, one of which we investigated in the red-cockaded woodpecker (Picoides borealis). Helping may provide a learning experience that improves reproductive success once the helper becomes a breeder. We used
data collected from a population of red-cockaded woodpeckers in the Sandhills of North Carolina to compare the reproductive
success of 2-year-old breeders that were helpers at age 1 (helping experience) to those that were floaters or solitary males
at age 1 (no helping experience). Reproductive success of the two groups was similar, indicating that helping provides no
experience useful in reproduction. We reject the learning experience hypothesis as an explanation for the maintenance of helping
behavior in red-cockaded woodpeckers.
Received: 29 July 1996 / Accepted after revision: 27 April 1997 相似文献
9.
Anne Peters Lee B. Astheimer Andrew Cockburn 《Behavioral ecology and sociobiology》2001,50(6):519-527
Superb fairy-wrens are cooperatively breeding birds that combine stable, socially monogamous pair bonds and high levels of paternal care, with extreme levels of extra-pair mating and high levels of sexual competition. Our aim was to determine which testosterone correlates would prevail in such a life history that combines features that are conventionally associated with divergent hormone profiles. Unlike the situation in other species with monogamous pair bonds and high levels of paternal care, testosterone was elevated for a very long period of several months. During breeding there was a broad peak in testosterone followed by a gradual decline: this resembles the profile found in polygynous and promiscuous species. We found that three factors correlated with testosterone: development of the sexually selected nuptial plumage, social status and extra-group mating opportunities. Testosterone started increasing months prior to breeding, when the males that are later preferred as extra-group sires develop their nuptial plumage. Although these males did not have higher testosterone levels during breeding, they sustained high testosterone for much longer, and this might lend reliability to this sexual signal. Dominant males in groups had higher testosterone than pair-dwelling males and subordinate helpers. This was not due to differences in age, reproductive capability or mating opportunities, but was presumably associated with the assertion of dominance. In contrast to findings in other species, male testosterone level was not correlated with whether the resident female was fertile or had dependent nestlings. However, testosterone was strongly correlated with the total number of fertile females in the population, and hence with the opportunities for extra-group mating. 相似文献
10.
Testosterone and the allocation of reproductive effort in male house finches (Carpodacus mexicanus) 总被引:9,自引:1,他引:8
Testosterone has been proposed to serve as the mediator that controls the relative effort that an individual male bird will
devote to mating effort versus parental effort. Here, we demonstrate a testosterone-influenced trade-off between parental
and mating efforts in male house finches. Male house finches with experimentally elevated testosterone fed nestlings at a
significantly lower rate, but sang at a higher rate than males without manipulated testosterone levels. Females mated to testosterone-implanted
males fed nestlings at a significantly higher rate than females mated to males without testosterone implants, resulting in
similar feeding rates for both treated and untreated pairs. The effects of testosterone on male house finches, however, were
not as dramatic as the effects of testosterone observed in some other socially monogamous species of birds. Because extra-pair
copulations are uncommon in house finches and males provide substantial amounts of parental care, these more modest effects
may be due to differences in how the allocation of reproductive effort affects the costs and benefits of different reproductive
behaviors.
Received: 6 June 2000 / Accepted: 17 July 2000 相似文献
11.
Julia Ostner Peter Kappeler Michael Heistermann 《Behavioral ecology and sociobiology》2008,62(4):627-638
Intense reproductive competition and social instability are assumed to increase concentrations of glucocorticoids and androgens
in vertebrates, as a means of coping with these challenges. In seasonally breeding redfronted lemurs (Eulemur fulvus rufus), the mating and the birth season and the associated increased male competition are predicted to pose such reproductive challenges.
In this paper, we investigate seasonal variation in hormone excretion in male redfronted lemurs, and examine whether this
variation is associated with social or ecological factors. Although dominance status has been shown to affect individual stress
levels across many taxa, we predicted no rank-related differences in glucocorticoids for redfronted lemurs because relatively
equal costs are associated with both high and low rank positions (based on patterns of rank acquisition/maintenance and threats
toward subordinates). Over a 14-month period, we collected behavioral data (1843 focal hours) and 617 fecal samples from 13
redfronted lemur males in Kirindy Forest/Madagascar. We found no general rank-related pattern of testosterone or glucocorticoid
excretion in this species. Both hormones were excreted at significantly higher levels during the mating and the birth season,
despite social stability during both periods. The elevated mating season levels may be explained by increased within-group
reproductive competition during this time and are in line with previous studies of other seasonally reproducing primates.
For the birth season increase, we propose that the predictable risk of infanticide in this highly seasonal species affects
male gonadal and adrenal endocrine activity. We evaluate alternative social and ecological factors influencing the production
of both hormone classes and conclude based on our preliminary investigations that none of them can account for the observed
pattern. 相似文献
12.
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
13.
Carotenoid-based ornaments (many yellow–orange–red colourations) may signal the genetic or parental quality of the bearer. Thus, their expression could influence the amount of resources/energy that the mate will invest in the production of offspring, thereby optimising its reproductive fitness. The differential allocation hypothesis (DAH) predicts that females mated with more attractive males should lay more and better eggs. This has been explored only in few bird species with carotenoid-based traits. We tested this hypothesis in the red-legged partridge (Alectoris rufa), a gallinacean with very variable laying capacity. Both sexes display carotenoid-based ornamentation that gradually fades throughout the laying period. Here, the redness of beak and eye rings of captive males was intensified after mating by means of paint. The proportion of females that laid eggs did not differ between treatments. Amongst laying females, those mated with colour-enhanced males (experimental females) tended to lay earlier and produced significantly more eggs than controls, but of similar quality (egg mass and composition). We additionally investigated whether male attractiveness influenced egg components depending on the clutch size and laying sequence. The testosterone level in eggs from experimental females was positively related to the laying order, whereas control eggs did not show any trend. Our results provided mixed support for the DAH, but nevertheless revealed that female red-legged partridges may adjust their breeding investment according to male carotenoid-based ornamentation. 相似文献
14.
15.
D. K. Brockman Patricia L. Whitten Alison F. Richard Benjamin Benander 《Behavioral ecology and sociobiology》2001,49(2-3):117-127
Previous research suggests that although reproduction and testicular function in wild sifaka (Propithecus verreauxi) are highly seasonal, birth season elevations in fecal testosterone (T) in transferring males indicate that social factors
may be as important as climatic factors in regulating reproductive function in sifaka. This paper examines the relationship
of male dispersal and social status to the patterning of birth season aggression and testicular function in P. verreauxi at Beza Mahafaly Special Reserve, Madagascar. Behavioral and hormonal data were collected from a total of 38 adult males,
15 residing in seven stable groups and 23 living in eight unstable groups, yielding 186 fecal samples and 493 focal animal
hours of observation. The results suggest that birth season elevations in fecal testosterone are the consequence of social
disruption resulting from male movements between groups and the particular responses of individual males to dispersal events.
Hormonal responses to dispersal events appear to precede behavioral responses and occasionally register reactions not concomitantly
evident in the behavioral response, and may be predictive of future events. Hormonal reactions occurred primarily in resident
alpha males, suggesting that they differ in their assessment of destabilizing influences, perhaps due to different reproductive
opportunities and/or investment. These findings are important for the new insights they provide into the role of androgens
in mediating male dispersal, life history, and reproductive strategies, and suggest that investigations of androgen-behavior
interactions in free-ranging populations can be a powerful new tool for assessing the contextual and motivational basis of
social behavior.
Received: 22 November 1999 / Revised: 27 April 2000 / Accepted: 15 October 2000 相似文献
16.
A. P. Møller L. Z. Garamszegi D. Gil S. Hurtrez-Boussès M. Eens 《Behavioral ecology and sociobiology》2005,58(6):534-544
Circulating levels of testosterone in adults have mainly evolved as a consequence of selection on males for increased levels, while levels of circulating testosterone in females may be an indirect consequence of selection on males. A review of the literature revealed that intense directional selection for high levels of circulating testosterone in birds is likely to be mainly due to direct selection on males. A comparative study of testosterone levels in birds revealed a strong positive relationship between peak testosterone levels in adult females and peak levels in males. The slope of this relationship was significantly less than unity, implying that the testosterone levels in females have been reduced in species with high levels in males. An analysis of the order of evolutionary events suggested that peak concentration of testosterone in females changed after peak concentrations of testosterone in males. Females in colonial species of birds had significantly higher circulating peak testosterone levels compared to females of solitary species, and relative levels after controlling for the effects of peak levels in males were also larger, suggesting that any costs of high testosterone levels in females are particularly likely in colonial birds. Direct selection on male circulating testosterone levels may increase the costs that females incur from high testosterone titers. For example, high female levels may negatively affect ovulation and laying and may also affect the levels of testosterone that females deposit in their eggs and hence the exposure of pre- and post-hatching offspring to testosterone. This in turn may affect not only offspring behavior, but also offspring development and the trade-offs between growth, development of immune function, and behavior in offspring. 相似文献
17.
Extra-pair paternity (EPP) is a common feature of the mating systems of many birds. The rate of EPP may vary between species, races and populations. A comparison of extra-group paternity (EGP) rates was made between two races of a group-living passerine, the Australian magpie (Gymnorhina tibicen), to determine if similar mating systems were being employed. The two populations had similar social structure, but differed in group size and dispersal. It was predicted that dispersal differences would have a profound effect on the rate of EGP between the populations, as the population with the lower rate of dispersal and higher chance of breeding with a close relative would engage in EGPs more frequently. Eight microsatellite loci were used to determine parentage in the white-backed Australian magpie (G. t. tyrannica). The rate of EGP was found to be 44%. Dispersal rates were estimated from observational data. Over half of the juvenile magpie cohort from the previous breeding season left the territorial group. These results contrast sharply with the results found by other researchers in a population of western Australian magpies (G. t. dorsalis). In this population, 82% EGP is recorded and dispersal of juveniles is close to nil. The results indicate that dispersal rate is a potentially important predictor of rates of extra-group fertilisations between populations of this species, and suggest that females maximise their reproductive output by avoiding breeding with close kin.Communicated by M. Soler 相似文献
18.
Anne-Mathilde Thierry Sophie Brajon Marion Spée Thierry Raclot 《Behavioral ecology and sociobiology》2014,68(5):721-732
Glucocorticoid hormones (GCs) are important mediators of physiological and behavioral responses to stress. While many studies have evaluated the environmental, behavioral, or physiological correlates of GCs and their effects on reproductive performances, further work is needed to clarify the relationship between GCs and fitness. Assessing the effects of increased GC levels on specific behaviors of breeding animals should improve our understanding of how GCs affect parental care. In this experimental study, we measured the effects of an experimental increase in corticosterone (CORT, the main avian GC) levels on the behavior of free-living male Adélie penguins (Pygoscelis adeliae) within the colony, their reproductive output, and the indirect consequences of both on the behavior of their partners. We show that increased CORT levels in males decreased their foraging time at sea while increased their attendance at the nest, although their attentiveness toward the nest itself decreased. In addition, treated males spent more time on comfort behaviors (e.g., preening), vocalizing, and engaging in positive social interactions relative to controls. Treatment further affected the behavior of their partners, but not chick begging and feeding rates. Penguins with increased CORT levels also exhibited decreased reproductive output. Previous studies of Adélie penguins in different life history stages and environmental conditions suggest that the consequences of CORT treatment on reproductive performance are context-dependent. In addition to the potential delay in the effects of increased CORT levels on reproduction, this context dependence should be taken into account when studying the behavior of free-living animals in relation to stress-inducing situations. 相似文献
19.
Julie K. Desjardins Kelly A. Stiver John L. Fitzpatrick Nicole Milligan Glen J. Van Der Kraak Sigal Balshine 《Behavioral ecology and sociobiology》2008,62(5):785-794
Among taxonomically widespread cooperatively breeding vertebrates, those with non-breeding helpers-at-the-nest provide an
excellent opportunity to understand the proximate mechanisms underlying care and allocare. In this study, we examined androgen
levels in relation to care behavior in a cooperatively breeding cichlid fish, Neolamprologus pulcher, from Lake Tanganyika. We concentrated on androgens, as these hormones have been linked to the defense behavior, and the
defense of young is a common form of parental care in fishes. N. pulcher dominant female breeders performed the most care and also displayed the highest levels of plasma testosterone (T) compared
with other individuals within the social group. We also found that dominant male breeders provided a similar amount of care
as did the subordinate helpers, but breeding males had the highest levels of 11-ketotestosterone (11KT), an important androgen
in fish. Breeders had higher levels of both androgens (T and 11KT) compared to helpers. There was a weak but significant positive correlation between T levels and the frequency of
care regardless of sex and status. Our results suggest that androgens may promote defense of young and are in contrast to
the commonly reported trade-off between androgen and parental care. 相似文献
20.
In temperate passerines, increased testosterone (T) levels during breeding mediate male aggressive and mating behaviour. If individual variability in T levels is reflected in behavioural differences during mating, males with higher T might gain higher reproductive success. This can be tested experimentally by elevating T levels. However, high exogenous T levels are known to have negative effects on male sperm production. This may reduce male fitness, particularly if sperm competition is intense. We experimentally elevated T levels in breeding blue tit males to investigate how T levels above the natural mean influence male reproductive success. Contrary to most—if not all—previous experimental manipulations of T levels in birds, we restricted the treatment with exogenous T to the time when females were fertile and T levels were naturally high in males. In blue tits, extra-pair paternity is an important component of male reproductive success, and its frequency is likely influenced by androgen-mediated behaviours such as mate attraction and aggression towards other males. Here we show that T-males were equally likely to become cuckolded and did not gain more extra-pair paternity than control males. Cuckolded T-males, however, lost more paternity than control males. We discuss the possibility that this is caused by negative effects of T treatment on sperm production.Communicated by M. Webster 相似文献