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1.
Amando Bautista Esmeralda García-Torres Margarita Martínez-Gómez Robyn Hudson 《Behavioral ecology and sociobiology》2008,62(3):331-339
Competition among mammalian siblings for scarce resources can be severe. Whereas research to date has focused on competition
for the mother’s milk, the young of many (particularly altricial) species might also be expected to compete for thermally
favorable positions within the nest, den, or litter huddle. We investigated this in newborn pups of the European rabbit Oryctolagus cuniculus, a species in which the altricial young are not brooded by the mother, and in which competition for milk is severe. In eight
unculled litters (N = 86 pups) of a domestic chinchilla strain, we calculated huddling indexes for individual pups on postnatal days 2–5 as a
measure of the degree of insulation they received from littermates. Pups maintained almost constant physical contact with
the litter huddle. They performed brief but frequent rooting and climbing behaviors, which usually improved their huddling
index, interspersed with longer periods of quiescence during which their huddling index declined. As expected, we found a
significant positive relation between pups’ mean huddling index and body temperature. Unexpectedly, however, we did not find
a relation between huddling index and pups’ birth weight, survival, milk intake, or efficiency of converting milk to body
mass. We conclude that rather than competing for thermally advantageous positions within the huddle newborn rabbits share
out thermally advantageous positions as they move in a continual dynamic flow through it. Thus, in newborn rabbits, competition
for the mother’s milk exists alongside mutual “cooperative” benefits of littermate presence.
This contribution is part of the special issue “Sibling competition and cooperation in mammals” (guest editors: Robyn Hudson
and Fritz Trillmich). 相似文献
2.
An organism’s pattern of development can have important long-term fitness effects. In species where the sexes differ in size
or other phenotypic traits, they may also have different optimal developmental rates. This influences both parental sex allocation
strategies and susceptibility of the sexes to early developmental conditions. However, sex differences in developmental rate
and vulnerability to environment during the embryonic period are not well understood. In birds, sibling competition and hatching
asynchrony may select for accelerated embryonic development of the last offspring in order to reduce their competitive disadvantage
after hatching. They may advance their hatching in response to vocal stimuli by the older siblings. It is, however, unclear
whether this flexibility in developmental rates is sex specific. In this study, we experimentally manipulated between-embryo
contact and tested whether this affected the pre-natal developmental rate and post-hatching performance of male and female
offspring from last-laid eggs in the herring gull. Post-hatching performance was measured both in competitive and non-competitive
situations. Among young incubated in isolation, males hatched faster than females, but both sexes fledged in similar, relatively
good condition. Among young incubated with normal between-embryo contact, hatching time did not differ between sexes, but
males fledged in poorer condition than females, regardless of whether they were reared singly or in a brood. These results
suggest that male and female offspring differ in their ability to mitigate the costs of hatching asynchrony. 相似文献
3.
Discrimination of different social companions in spectacled parrotlets (Forpus conspicillatus): evidence for individual vocal recognition 总被引:1,自引:0,他引:1
Ralf Wanker Jasmin Apcin Bert Jennerjahn Birte Waibel 《Behavioral ecology and sociobiology》1998,43(3):197-202
Individual recognition is generally assumed to be a prerequisite for establishing and maintaining a complex social system.
Indeed, there is good evidence that highly social species have complex systems of vocal communication with individual recognition
by acoustic cues. In this study, we provide experimental evidence that vocal class and individual recognition is present in
a non-passerine bird, the spectacled parrotlet (Forpus conspicillatus). Spectacled parrotlets live in a complex system of social relationships. Soon after fledging, the young establish close
sibling relationships which are important for successful socialization, pairing and reproduction. In a series of playback
experiments we tested if spectacled parrotlets use contact calls for vocal recognition. The results showed that spectacled
parrotlets discriminate between the contact calls of different social categories. Adult birds preferred to respond to the
contact calls of their mates. Subadult individuals recognized the contact calls of their siblings. During the period of pair
bond formation, the affiliative contacts to the siblings decrease, but the parrotlets continue to respond to the calls of
their siblings. This is the first evidence that vocal sibling recognition might outlast the period of strong sibling interaction
and extends into the period of pair bond formation. In cases of mate loss or divorce, the acoustic contact to their siblings
might facilitate the re-establishment of close sibling relationships.
Received: 29 October 1997 / Accepted after revision: 5 April 1998 相似文献
4.
Behavioural research on domestic pigs has included parent–offspring conflict, sibling competition, and the use of signals
which influence resource allocation. In this paper, we review key sow–piglet behavioural studies and discuss their relevance
to resource allocation theory. Sibling competition begins in the uterus and continues after birth, as piglets compete directly
for access to the sow’s teats. This competition is made more severe by a unique dentition, which newborn piglets use to lacerate
the faces of siblings during teat disputes. Competition often leads to the death of some littermates, especially those of
low birth weight. Piglets also compete indirectly for milk, apparently by stimulating milk production at the teats that they
habitually use at the expense of milk production by other teats. The complex nursing behavior of the sow appears designed
to prevent the more vigorous piglets from monopolizing the milk. Sows give vocal signals which both attract piglets to suckle
and synchronize their behavior during nursing episodes. Piglets give loud vocal signals when separated from the sow; calls
which vary in intensity and appear to be honest signals of need. Udder massage by piglets may also serve as an honest signal
of need. Parent–offspring conflict has been demonstrated experimentally in pigs. Specifically, when given the opportunity
to control contact with their piglets, sows nurse less frequently, provide less milk, and lose less weight during lactation
than sows that cannot control their level of contact. Because of this interesting natural history and because they are so
amenable to experimentation, domestic pigs provide a rich system for testing ideas drawn from resource allocation theory.
This contribution is part of the special issue “Sibling competition and cooperation in mammals” (guest editors: Robyn Hudson
and Fritz Trillmich). 相似文献
5.
Parent–offspring conflict theory is well supported by theoretical arguments. However, empirical observations are often difficult to interpret and have contradicted one of its most appealing predictions that parent and offspring should disagree over killing of nest or littermates. We present the first examples of deadly conflict between siblings of different cohorts. In Galápagos fur seals (Arctocephalus galapagoensis) and sea lions (Zalophus wollebaeki), mothers often wean their single offspring at 2 years. This leads to a situation where up to 23% of all pups are born while the older sibling is still being nursed. Younger siblings are disadvantaged by being born lighter than neonates without older still dependent siblings. Pups born while an older sib is still dependent grow less in early life (fur seal) and suffer increased early mortality (both species) through direct aggression or scramble competition with the older sibling. This effect is much stronger in years of high sea surface temperature (El Niño) indicating low marine productivity and if the older offspring is a male. In both species, mothers interfere aggressively in this conflict by defending the younger offspring. In years of El Niño, intense resistance to maternal aggression by the older offspring happens frequently in the fur seal. Such resistance against weaning can induce maternal neglect of the newborn. Given substantial year to year variation in offspring growth, maternal aggression forces weaning in the older sibling only if it has reached sufficient size to support itself by foraging. In Galápagos fur seals, pups with older siblings can either represent insurance against loss of older offspring or extra reproductive value. 相似文献
6.
The influence of genetic relatedness on the individual performance (e.g. growth, development) of animals is often tied to
agonistic or cooperative behaviors among conspecifics, and studies of the effects of kinship have produced mixed results.
To explore genetic relatedness independent of these behaviors, we investigated the effects of kinship on the growth of the
kelp perch Brachyistius frenatus, a live-bearing, planktivorous marine reef fish that is capable of only limited dispersal. Although juveniles occur in aggregations
and compete for food resources, they do not exhibit overt aggressive or cooperative behavioral interactions. We hypothesized
that under competition and in the absence of these behaviors, sibling and non-sibling groups of juvenile B. frenatus raised at the same densities in the field would not differ in average growth, but that siblings would exhibit lower variation
in growth, simply due to genetic similarities in inherent growth rates. Pregnant, female kelp perch were collected and placed
in cages until parturition was complete. Groups of young, recently born from the same mother or from different mothers, were
then raised in the field for 9 wk. Our results revealed that average growth rates were similar between sibling and non-sibling
treatments. While variation in growth increased initially in non-siblings, siblings showed little such variation. This divergence,
however, was not consistent over the duration of the experiment, and variation in the growth of siblings ultimately converged
with that of non-siblings. Effects of genetic relatedness would be most likely to manifest themselves early after birth, before
environmental factors exert their influence, and this may explain the initial separation but eventual convergence in variation
in growth between sibling and non-sibling treatments. For B. frenatus and other organisms that will encounter relatives and compete for resources without overt behavioral interactions, the degree
of kinship may play a minor role in the demography of local populations.
Received: 26 January 1998 / Accepted: 30 September 1998 相似文献
7.
Over the past 1000 years New Zealand has lost 40–50% of its bird species, and over half of these extinctions are attributable to predation by introduced mammals. Populations of many extant forest bird species continue to be depredated by mammals, especially rats, possums, and mustelids. The management history of New Zealand's forests over the past 50 years presents a unique opportunity because a varied program of mammalian predator control has created a replicated management experiment. We conducted a meta-analysis of population-level responses of forest birds to different levels of mammal control recorded across New Zealand. We collected data from 32 uniquely treated sites and 20 extant bird species representing a total of 247 population responses to 3 intensities of invasive mammal control (zero, low, and high). The treatments varied from eradication of invasive mammals via ground-based techniques to periodic suppression of mammals via aerially sown toxin. We modeled population-level responses of birds according to key life history attributes to determine the biological processes that influence species’ responses to management. Large endemic species, such as the Kaka (Nestor meridionalis) and New Zealand Pigeon (Hemiphaga novaeseelandiae), responded positively at the population level to mammal control in 61 of 77 cases for species ≥20 g compared with 31 positive responses from 78 cases for species <20 g. The Fantail (Rhipidura fuliginosa) and Grey Warbler (Gerygone igata), both shallow endemic species, and 4 nonendemic species (Blackbird [Turdus merula], Chaffinch [Fringilla coelebs], Dunnock [Prunella modularis], and Silvereye [Zosterops lateralis]) that arrived in New Zealand in the last 200 years tended to have slight negative or neutral responses to mammal control (59 of 77 cases). Our results suggest that large, deeply endemic forest birds, especially cavity nesters, are most at risk of further decline in the absence of mammal control and, conversely suggest that 6 species apparently tolerate the presence of invasive mammals and may be sensitive to competition from larger endemic birds. 相似文献
8.
Joachim G. Frommen Marion Mehlis Christina Brendler Theo C. M. Bakker 《Behavioral ecology and sociobiology》2007,61(4):533-539
Shoaling with familiar kin is a well-known phenomenon. It has been described both for adult and for fry of three-spined sticklebacks
(Gasterosteus aculeatus). However, evidence of preference for kin independent of familiarity is scarce. Furthermore, inbreeding effects have not
been studied for shoaling preferences and there is a lack of studies about changes in individuals’ ability to recognise kin
during different phases of life history. We gave inbred and outbred, nonreproductive sticklebacks of different age the choice
to shoal with a group of familiar siblings vs unfamiliar non-siblings and with unfamiliar siblings vs unfamiliar non-siblings.
Subadult sticklebacks preferred to shoal with familiar kin over unfamiliar non-kin, but inbred and outbred individuals had
similar preferences. When given the choice between unfamiliar siblings and unfamiliar non-sibs, adult outbred fish preferred
the shoal of kin, while inbred fish behaved indifferently. Body characteristics of the group such as body mass, standard length
and condition of its members did not significantly explain the shoaling preferences for kin. Thus, sticklebacks were capable
of recognising familiar and unfamiliar kin. The latter capability was lost by inbreeding. 相似文献
9.
Asymmetric sibling competition, which occurs when some siblings hatch as stronger competitors than others, is an important component of avian reproductive strategies. Here, we report two experiments on the burying beetle Nicrophorus vespilloides investigating how parents might influence the outcome of asymmetric sibling competition. In this species, as in altricial birds, different-aged offspring compete for resources provided by the parents. However, unlike altricial birds, offspring depend only partially on their parents for resources, and parents adjust the brood size directly through filial cannibalism. In the first experiment, we compared the growth and survivorship of different-aged offspring when parents could and could not influence asymmetric sibling competition. In the second experiment, we recorded behavioral interactions between different-aged offspring and parents. We found that senior offspring (early-hatched) grew faster than juniors (late-hatched) when parents were present and could influence the outcome of sibling competition, whereas seniors and juniors grew at similar rates when parents were removed. Thus, seniors benefited more than did juniors when the offspring could obtain resources by begging from the female parent. There was no difference in the survivorship of seniors and juniors. We also found that seniors and juniors spent a similar amount of time feeding from female parents, but juniors spent more time begging and were less effective at begging than seniors. Interestingly, juniors spent more time begging only as long as seniors also begged, suggesting that juniors adjusted their begging effort in response to direct competition against seniors for resources provided by parents. Our study provides novel insights into the ecological significance of asymmetric sibling competition by showing that asymmetric sibling competition took place when parents were present and offspring could obtain resources by begging. In contrast, we found no evidence of asymmetric sibling competition when parents were absent and offspring obtained resources solely by self-feeding. 相似文献
10.
Provisioning rules and chick competition in asynchronously hatching common terns (Sterna hirundo) 总被引:2,自引:0,他引:2
Tasha E. Smith Marty L. Leonard Barry D. Smith 《Behavioral ecology and sociobiology》2005,58(5):456-465
Interactions between nestling birds and their parents are models for examining parent–offspring communication and sibling competition. Most studies have focused on species where young are restricted to a nest. However, offspring of many species are mobile and fed by parents for an extended period post-hatch. These chicks mobility may provide an opportunity to examine the role of signalling and physical competition on parental feeding decisions. We examined parental provisioning rules in relation to offspring behaviour and hatching order (i.e., competitive ability) in a species with mobile young, the common tern. We determined that about 95% of feedings were directed to the first chick to reach the parent when it landed with food. We developed a probabilistic model to predict the likelihood of a chick reaching the parent first, and thus receiving food. Our model showed that begging intensity, feeding history, and the interaction between begging intensity and relative proximity to the parent best predicted which chick would arrive first. Increased begging was associated with arriving first significantly more when a chick was relatively further from the parent than when it was closer than its siblings. Independently of these factors, larger, earlier-hatched chicks were more likely to be fed than smaller, later-hatched chicks. Additional analyses showed that parents landed closer to more intensively begging chicks, however, increased begging did not explain the advantage of earlier-hatched chicks because begging intensity did not vary with hatching order. Instead, earlier-hatched chicks were more likely to outrun later-hatched siblings and reach the parent first. 相似文献
11.
Sibling aggression, hatching asynchrony, and nestling mortality in the black kite (Milvus migrans) 总被引:3,自引:0,他引:3
Javier Viñuela 《Behavioral ecology and sociobiology》1999,45(1):33-45
In siblicidal species, hatching asynchrony could act to reduce sibling rivalry or promote the death of last-hatched chicks.
The pattern of hatching asynchrony was experimentally altered in the black kite Milvus migrans. Hatching asynchrony in control broods was intermediate between those of experimentally synchronised and asynchronised broods.
Sibling aggression and wounds on the chicks were more commonly observed early in the nestling period and in synchronous nests.
Serious injuries were observed on last-hatched chicks in asynchronous nests, as were observations of intimidated or crushed
chicks. Sibling aggression was related to food abundance, but some chicks died at an early age in nests with abundant food
(cainism). Cainism was more commonly found in asynchronous nests. For species with facultative siblicide, moderate hatching
asynchrony could be a compromise between reducing sibling rivalry and avoiding large size differences between sibs that would
result in cainism. Female black kites preferentially fed the smallest chicks and exhibited behaviours to reduce sibling aggression,
contrary to observations in other siblicidal species. In a highly opportunistic forager such as the black kite, a strategy
may exist to protract the life of all the chicks in the brood, waiting for unpredictable situations of food overabundance.
This would induce the appearance of a parent-offspring conflict over brood reduction, reflected in the existence of a possible
anticipated response by some of the chicks (cainism) and in the appearance of special behaviours by the parents to selectively
feed smaller chicks or reduce sibling aggression. In this facultatively siblicidal species, cainism does not seem to be the
final stage of an evolutionary trend favouring the raising of high-quality chicks, but a manifestation of a parent-offspring
conflict over brood size.
Received: 9 March 1998 / Accepted after revision: 8 August 1998 相似文献
12.
Summary A laboratory study on the ontogeny of social behavior in pikas (Ochotona princeps), an alpine lagomorph, was conducted to determine the role of early relationships between adult females and young and among siblings in the development of territorial and dispersal behaviors. Sex differences during development were examined because field studies have reported greater dispersal distances in young females than young males. At birth, females were significantly heavier than males. There were no sex differences in nursing frequency until after the 2nd week of age, when males initiated more nursing attempts than females. By the end of the weaning period (weeks 5 and 6), adult females became non-interactive with young, but aggression of young toward littermates and the mother increased until the eighth week. At this time, young males outweighed their sibling females. Young were dominant over their mothers by the age of 5 weeks, and young males were dominant over their sibling females.Sex differences were observed in aggression, scent-marking, exploratory activity, and submissive vocalizations, with higher rates in young males, except for submissive vocalizations, which were higher in females (Table 2). Vocalizations and scent-marking behavior increased over time, and were positively correlated with interaction rates.These data support the hypothesis that female young disperse farther than male young largely as the result of unsuccessful competition with male siblings for available territories close to the birthplance. A dispersal strategy for pkkas is proposed. 相似文献
13.
Environmental salinity is important in defining Brachionus plicatilis sibling species distributions. However, while salinity influences distributions, sibling species often co-exist. Three different mechanisms potentially account for the partial co-occurrence of sibling species: (1) siblings have differing salinity tolerances that partially overlap; (2) siblings physiological tolerances may be commonly broad, but relatively small differences in tolerances differentiate distributions via interactions e.g. competition; or (3) siblings distributions may be influenced by physical factors other than salinity. Here, we assess the extent of salinity tolerance in three B. plicatilis sibling species (B. plicatilis 6TUR, B. plicatilis IOM and B. rotundiformis 6TOS) by measuring population growth rate (μ, day−1) and egg development time in response to salinity (5–60‰) and salinity fluctuations (≤ Δ40‰). Sibling species were identified by analysis of the mitochondrial COI gene, and salinity responses were compared by regression analysis. Responses differed significantly between siblings, although the broad trends were similar. Positive growth occurred at all salinities, and highest growth rates ranged between 0.93 and 1.08 day−1 at 16–18‰. Rapid changes in salinity reduced growth rates, but net mortality occurred only in one treatment (100% mortality on transfer from 10 to 40‰). Egg development time was largely invariant with salinity except for B. plicatilis IOM and where rotifers were transferred from 30 to 60‰. We indicate that several siblings are similarly euryhaline and tolerate salinity fluctuations. Undoubtedly, wide tolerances in B. plicatilis are adaptations to ephemeral and seasonally variable habitats. Given common broad salinity tolerances, it is unlikely that the differential distributions of sibling species are a direct result of physiological constraints. Instead, we illustrate using a simple model that subtle differences in physiological tolerances may have important impacts on interactions between sibling species, which may in turn influence distributions. 相似文献
14.
Kin recognition in the common lizard 总被引:4,自引:0,他引:4
Jean Paul Léna Michelle de Fraipont Jean Paul Léna 《Behavioral ecology and sociobiology》1998,42(5):341-347
The ability to recognize parents has never been reported in species in which parents do not provide care to their young;
in such species, only sibling recognition has been found. However, there may be several advantages of parent recognition,
even in the absence of parental care. We investigated the ability of neonates to recognize olfactory cues from both their
mother and siblings in the common lizard, Lacerta vivipara, a species without parental care. Juveniles from 264 gravid females were reared for 2 days either with their mother, with
another female, or separated from all other adults. Juveniles from some families were split into two or three groups so that
each juvenile was unfamiliar with a subset of its siblings. After 2 days, we offered the juveniles a choice of two nocturnal
shelters: one containing a lizard odor and the other without odor. The response to the odor of an unrelated and unfamiliar
adult was influenced by both the sex of the adult and the sex of the juvenile. Juveniles of both sexes recognized the odor
of their mother whether they were familiar with her or not (pre-natal determinism). Juveniles recognized familiar but not
unfamiliar siblings (post-natal determinism). In the wild, spatial association with kin declines shortly after birth. Thus,
recognition of the mother is likely to have biological relevance. Recognition of the mother may reduce competition and/or
enhance juvenile establishment.
Received: 15 May 1997 / Accepted after revision: 29 December 1997 相似文献
15.
Few studies have investigated the long-term fitness consequences of nestling size hierarchies in altricial birds. In this
study, we investigated whether or not the size rank order of siblings influences subsequent breeding success in the little
egret, Egretta garzetta. From a marking program allowing individual recognition of wild birds, we obtained data on the breeding success of 56 pairs
comprising individuals for which the size rank order was known. The breeding success in these pairs was positively influenced
by the age of the marked bird but negatively affected by the laying date of the pair and the size rank order of the marked
individual. There was also a significant difference between breeding colonies. We suggest two main hypotheses for a link between
size rank order of individuals and their breeding success and we discuss our results in relation to current hypotheses on
the adaptive value of hatching asynchrony.
Received: 10 August 1998 / Accepted after revision: 13 December 1998 相似文献
16.
We investigated the fledging probability of oystercatcher, Haematopus ostralegus, chicks as a function of hatching order, brood size, territory quality and food availability. Sibling dominance was related
to the hatching order in both low- (’leapfrogs’) and high-quality (’residents’) territories. Differences in hatchling mass
might have aided the establishment of a dominance hierarchy, since breeders produced small late eggs and hatchlings. These
mass differences were most pronounced in leapfrogs, and in large broods in years with lower food availability (’poor’ years).
Late hatchlings fledged less often and with lower body masses compared to early hatchlings in all situations. Leapfrogs produced
smaller broods and hatched their broods more asynchronously in poor years than leapfrogs breeding in years with more available
food (’good’ years) and residents breeding in both poor and good years. Large brood sizes resulted in lower survival of hatchlings
in poor years. These results favour the ’brood reduction’ hypothesis. However, contrary to the expectations of this hypothesis,
hatching order also affected fledging success in residents. Moreover, large brood size resulted in higher survival of hatchlings
in good years, particularly in residents. Thus, although large broods experienced losses due to sibling competition in some
years, they nevertheless consistently produced more fledglings per brood in all years, both as leapfrogs and residents. We
believe this effect is due to parental quality correlating with initial brood size. Most leapfrogs, at best, fledged one chick
successfully each year, losing chicks due to starvation. Nevertheless, leapfrog broods were reduced in size after hatching
significantly less quickly than resident broods. These results suggest that breeders lay and hatch insurance eggs to compensate
for unpredictable losses due to the high predation rates on both nests (ca 50%) and chicks (ca 90%), in accordance with the
’nest failure’ hypothesis.
Received: 14 February 2000 / Revised: 27 September 2000 / Accepted: 10 June 2000 相似文献
17.
Paula A. White 《Behavioral ecology and sociobiology》2008,62(3):377-361
Among spotted hyenas, Crocuta crocuta, neonatal aggression in twins is a well-known phenomenon and serves to establish intra-litter dominance soon after birth.
As the stronger more aggressive cub presumably attains dominance over its twin, intra-litter dominance presents mothers with
an ideal opportunity to assess individual cub fitness and, thereafter, to selectively favor one cub over the other. This study
quantified maternal response to sibling conflict in 26 sets of twins born to 16 wild-living females to determine whether mothers
of different social ranks exhibited favoritism towards sons or daughters, or in the case of same-sex twins, the dominant or
subordinate cub. Maternal response to sibling conflict did not vary with litter sex composition, suggesting that mothers do
not favor offspring of one sex over the other. All mothers intervened when their cubs fought and sometimes punished their
cubs. Higher-ranking mothers more often punished both cubs, while lower-ranking mothers were more selective and punished the
dominant cub. Where sibling aggression was most extreme, rather than favor the dominant sibling, mothers of all ranks made
concessions to the subordinate cub that included procuring private nursing bouts for the subordinate and temporarily housing
twins in separate dens, presumably to decrease sibling conflict. These findings represent a complex example of parent–offspring
conflict and support both the insurance cub hypothesis and resource tracking hypothesis that mothers endeavor to keep all
offspring alive for as long as possible in the event that the dominant sibling dies or that resources provide for the rearing
of twins.
This contribution is part of the special issue “Sibling competition and cooperation in mammals” (guest editors: Robyn Hudson
and Fritz Trillmich). 相似文献
18.
Birth sex ratios in toque macaques and other mammals: integrating the effects of maternal condition and competition 总被引:2,自引:0,他引:2
Wolfgang P. J. Dittus 《Behavioral ecology and sociobiology》1998,44(3):149-160
Mammalian life histories suggest that maternal body condition and social dominance (a measure of resource-holding potential)
influence the physical and social development of offspring, and thereby their reproductive success. Predictably, a mother
should produce that sex of offspring which contributes most to her fitness (as measured by the number of her grandchildren)
and that she is best able to raise within the constraints imposed by her condition, social rank, and environment. Such combined
effects were investigated by monitoring variations in body condition (weight) and behavior of female toque macaques, Macaca sinica of Sri Lanka, in a changing forest environment over 18 years. Maternal rank, by itself, had no influence on offspring sex,
but did affect maternal body condition. The combined effects of rank and condition indicated the following: mothers in robust
condition bore more sons, whereas those in moderate condition bore more daughters, but both effects were expressed most strongly
among mothers of high rank. Where the consequences of low rank were felt most acutely, as shown by poor condition, mothers
underproduced daughters. Environmental quality directly influenced rank and condition interactions, and thus sex ratios. These
relationships, and data from other mammals suggest an empirically and theoretically consistent pattern of sex allocation in
mammals. New predictions integrate effects, proposed by Trivers and Willard, that are rooted in male mate competition, which
is universal among polygynous mammals, with those of local resource competition (and/or female reproductive competition),
which are not universal and differ in intensity between the socioecologies and local environments of different species.
Received: 30 May 1998 / Accepted after revision: 29 August 1998 相似文献
19.
When eggs hatch asynchronously, offspring arising from last-hatched eggs often exhibit a competitive disadvantage compared
with their older, larger nestmates. Strong sibling competition might result in a pattern of resource allocation favoring larger
nestlings, but active food allocation towards smaller offspring may compensate for the negative effects of asynchronous hatching.
We examined patterns of resource allocation by green-rumped parrotlet parents to small and large broods under control and
food-supplemented conditions. There was no difference between parents and among brood sizes in visit rate or number of feeds
delivered, although females spent marginally more time in the nest than males. Both male and female parents preferentially
fed offspring that had a higher begging effort than the remainder of the brood. Mean begging levels did not differ between
small and large broods, but smaller offspring begged more than their older nestmates in large broods. Male parents fed small
offspring less often in both brood sizes. Female parents fed offspring evenly in small broods, while in large broods they
fed smaller offspring more frequently, with the exception of the very last hatched individual. These data suggest male parrotlets
exhibit a feeding preference for larger offspring—possibly arising from the outcome of sibling competition—but that females
practice active food allocation, particularly in larger brood sizes. These differential patterns of resource allocation between
the sexes are consistent with other studies of parrots and may reflect some level of female compensation for the limitations
imposed on smaller offspring by hatching asynchrony. 相似文献
20.
Lactation is the most energy-intense period in the life of a female mammal. This can cause severe conflict between mother
and offspring over the duration of lactation but also between siblings over the amount of milk each pup gets from its mother.
Thus, competitive interactions between siblings are expected, and competition is likely to increase with litter size, particularly
in species where the number of offspring exceeds the number of teats. We studied sibling competition in the domestic guinea
pig (Cavia aperea f. porcellus), which has two teats, but frequently bears litters of up to five pups. By cross-fostering we created non-competition (control)
litters with two pups and competition litters with four pups and observed nursing behaviour on days 5, 10, 15 and 20 postpartum.
Pups of larger litters had lower growth rates, indicating increased competition among siblings in these litters. Pups of larger
litters had to wait longer for access to a teat and spent less time suckling than pups of smaller litters but ate more solid
food instead. Additionally, we manipulated the individual short-term need of pups by separating half of the pups of each litter
for 2 h from their mothers before observation. Within a litter, hungry pups achieved access to milk faster and spent more
time suckling than non-hungry pups. Pups competed mostly by scramble competition. Aggressive interactions occurred only in
large litters. Pups of large litters had higher cortisol levels than pups in small litters. These effects decreased with age
as pups became increasingly independent of maternal milk. Pup behaviour appears to fit better with models of scramble competition
than with those of honest signalling.
This contribution is part of the special issue “Sibling competition and cooperation in mammals” (guest editors: Robyn Hudson
and Fritz Trillmich). 相似文献