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1.
Piyamas Nanork Siriwat Wongsiri Benjamin P. Oldroyd 《Behavioral ecology and sociobiology》2007,61(10):1509-1514
Honey bee workers are able to distinguish queen-laid eggs from worker-laid eggs, and remove (‘police’) worker-laid eggs. The
cue that police workers use is as yet unidentified but is likely to be a chemical signal. This signal benefits queens for
it ensures their reproductive monopoly. It also benefits collective workers because it allows them to raise more closely related
queen-laid males than the less-related sons of half sisters. Because both parties benefit from the egg-marking signal, it
should be stable over evolutionary time. We show that Apis mellifera workers can distinguish queen-laid from worker-laid eggs of the dwarf honey bee A. florea, a phylogenetically distant species that diverged from the A. mellifera lineage 6–10 mya. However, A. mellifera workers are unable to distinguish worker-laid eggs of A. cerana, a much more recent divergence (2–3 mya). The apparent change in the egg-marking signal used by A. cerana may be associated with the high rates of ovary activation in this species. 相似文献
2.
Laurent Keller Liselotte Sundström Michel Chapuisat 《Behavioral ecology and sociobiology》1997,41(1):11-15
The relative number of workers and female sexuals fathered by two males mated with a queen were directly assessed using microsatellite
and allozyme markers in field colonies of the ants Formica exsecta and F. truncorum. In both species one of the two males consistently fathered more offspring than the other. There was, however, no evidence
that one male might be particularly successful in fathering a disproportionally high proportion of female sexuals relative
to the proportion of workers. Moreover, in F. exsecta, the proportions of worker pupae and worker adults fathered by each male did not differ significantly between cohorts. The
most likely explanation for this pattern is that females store different amounts of sperm from the two males they mated with.
Received: 10 January 1997 / Accepted after revision: 22 March 1997 相似文献
3.
Effect of female molt stage and sex ratio on courtship behavior of the blue crab Callinectes sapidus
In many species, males and females actively participate in courtship, and the outcome of pre-mating interactions influences
the mating success of both sexes. Female blue crabs, Callinectes sapidus, mate soon after their final molt to maturity; thus female molt stage dictates the timing of mating. In a field experiment,
we manipulated female molt stage and sex ratio to test their effects on the courtship behavior of both sexes, if female behavior
influences the behavior and pairing success of males, and if male courtship influences male pairing-success. Early-molt-stage
females avoided males during courtship, whereas late-molt-stage females sought out males. As a result, males had to pursue
and capture early-molt-stage females whereas males displayed to late-molt-stage females and more easily physically controlled
them. Males sometimes abandoned late-molt-stage females, but this occurred more often when females were abundant. The rate
at which females avoided males was positively correlated with that of males abandoning females, and males that were unsuccessful
at pairing met with higher rates of female resistance than successful males, suggesting that female behavior influences male
pairing-success. Unlike unsuccessful males, successful males more often made the transition between display and maintaining
physical control of the female. At high male sex ratios, males initiated courtship more readily; thus both sexual competition
and female behavior influence male courtship in this species.
Received: 7 July 1996 / Accepted: 10 January 1998 相似文献
4.
The growth rates of the morphologically similar scyllarid lobsters Ibacus peronii (Leach, 1815) and I. chacei (Brown and Holthuis, 1998) are described using data from a tag/recapture study and from tagged lobsters kept in captivity.
Within particular size classes, we found no differences in moult increments between male and female I. peronii nor between male and female I. chacei. Small individuals of both species always had larger moult increments than larger individuals. For I. peronii, females moulted more frequently than males, and smaller size classes moulted more frequently than larger size classes. Female
I. peronii therefore grew more quickly than males and reached their estimated size at sexual maturity (51 mm carapace length) after
∼2 yr. Moulting of I. peronii was seasonal, with most lobsters (96.3%) moulting between October and January. We found no differences in growth rates of
I. peronii at two locations along the east coast of Australia: Coffs Harbour in New South Wales (30°18′S; 153°08′E), and Lakes Entrance
in Victoria (37°53′S; 148°00′E). For I. chacei, we found no differences in the frequency of moulting between males and females and, because we also found no differences
in the moult increments between males and females, the growth rates of both sexes were the same.
Received: 14 August 1999 / Accepted: 20 January 2000 相似文献
5.
A. D. Tucker H. I. McCallum C. J. Limpus K. R. McDonald 《Behavioral ecology and sociobiology》1998,44(2):85-90
We compared natal dispersals of freshwater crocodiles (Crocodylus johnstoni) against the prediction of male dispersal bias for a polygynous mating system. The crocodiles inhabited a linear series of
pools and we calculated the net distances from natal pools to recapture locations some 12–18 years later, at maturity. Philopatry
was assessed in terms of adult social distances. A female social distance was 0.46 pools and a male social distance was 1.0
pool. By these criteria, both sexes showed low levels of philopatry (7–12%). However, individuals of both sexes dispersed
from the natal site long before they were sexually mature. Divergence in dispersal patterns by sex occurred after the maturity
threshold, as males dispersed two to three times farther than females. Intrasexual competition by males is resolved by a size-based
hierarchy. The displacement of small males from local mating access is a probable cause of the longer dispersals undertaken
by males. Competition, rather than inbreeding avoidance, is driving dispersal in this population of freshwater crocodiles.
Received: 8 May 1998 / Accepted after revision: 26 June 1998 相似文献
6.
The host size model, an adaptive model for maternal manipulation of offspring sex ratio, was examined for the parasitoid
wasp Spalangia endius. In a Florida strain, as the model predicts, daughters emerged from larger hosts than sons, but only when mothers received
both small and large hosts simultaneously. The pattern appeared to result from the mother's ovipositional choice and not from
differential mortality of the sexes during development. If sex ratio manipulation is adaptive in the Florida strain, it appears
to be through a benefit to daughters of developing on large hosts rather than through a benefit to sons of developing on small
hosts. Both female and male parasitoids were larger when they developed on larger hosts. For females, developing on a larger
host (1) increased offspring production, except for the largest hosts, (2) increased longevity, (3) lengthened development,
and (4) had no effect on wing loading. For males, development on a larger host had no effect on any measure of male fitness
– mating success, longevity, development duration, or wing loading. In contrast, a strain from India showed no difference
in the size of hosts from which daughters versus sons emerged, although both female and male parasitoids were larger when
they developed on larger hosts. These results together with previous studies of Spalangia reveal no consistent connection between host-size-dependent sex ratio and host-size-dependent parasitoid size among strains
of S. endius or among species of Spalangia.
Received: 28 October 1998 / Received in revised form: 20 May 1999 / Accepted: 30 May 1999 相似文献
7.
The reproductive biology of Antipathes fiordensis Grange, a species endemic to south-western New Zealand, was followed from April 1994 to May 1995. Ten colonies were individually
tagged in Doubtful Sound and sampled on a monthly basis in order to determine their reproductive activity. The fecundity of
each of the five tagged female colonies was determined by estimating the total number of polyps per colony from photographs
of each colony and by planimetry, the proportion of gravid polyps per colony, and the mean number of oocytes per gravid polyp.
In addition, 56 colonies were sampled in March 1995 to estimate the sex ratio, height at sexual maturity, and mean sizes of
females and males. A. fiordensis was found to be a dioecious species which, in the absence of gonads in the polyps, has no obvious external morphological
differences between the sexes. Broadcast spawning of gametes is the likely mode of reproduction. Gametogenesis began in November
1994 and was highly synchronous within and between colonies, with spawning occurring in March 1995. The sex ratio in adults
was 1:1. Colonies reached sexual maturity between the heights of 70 and 105 cm which, based on existing estimates of growth
rate, corresponds to a minimum age for sexual maturity of about 31 yr. The largest oocytes measured ranged from 100 to 140 μm
in size. Female colonies produced between 1.3 and 16.9 million oocytes, with the larger colonies dominating the reproductive
output of the population.
Received: 23 June 1997 / Accepted: 1 August 1997 相似文献
8.
Several aspects of the biology of Bathypolypus sponsalis were studied from 297 individuals (115 males, 180 females and 2 indeterminates) caught in a depth range of 200–800 m depth
in the western Mediterranean Sea. The paper presents data on sizes (length-weight relationships, size-frequency distributions)
and reproduction (sex ratio, maturation, condition), and also analyses of the diet of B. sponsalis from samples taken throughout the year. Length-weight relationships showed that females are heavier than males at the same
mantle length. Although mature individuals were found all year round, the maximum number occurred in spring and summer. Sexual
maturation data revealed that males mature at smaller sizes than females. The gonadosomatic index increased with maturity
in both sexes; the increase was gradual in males, but abrupt in females. The digestive gland index was used as a condition
index and showed a differential behaviour with maturity; it increased gradually in females, but decreased in males. Like other
octopus species, B. sponsalis appears to be an opportunistic predator, feeding on a great variety of preys. Stomach content analysis yielded a total of
19 different prey items belonging to four major groups (Crustacea, Mollusca, Ophiuroidea and Osteichthya). The first three
groups were the more frequent preys, since crustaceans, molluscs and ophiuroids appeared in 76%, 49% and 30% of the stomachs,
respectively. Decapoda Reptantia (among crustaceans) and cephalopods and bivalves (among molluscs) constituted the more abundant
prey items. While the Decapoda Reptantia group was significantly more abundant in stomach contents of females, gastropods
were taken more frequently by males. These differences in diet could reveal females as a more active predators than males.
Received: 5 March 2000 / Accepted: 7 November 2000 相似文献
9.
Glenn T. Crossin Scott G. Hinch Steven J. Cooke David W. Welch Sonia D. Batten David A. Patterson Glen Van Der Kraak J. Mark Shrimpton Anthony P. Farrell 《Marine Biology》2007,152(4):905-918
Adult sockeye salmon (Oncorhynchus nerka, N = 179) from six Fraser River populations (British Columbia) were intercepted in continental shelf waters ∼215 km from the
Fraser River mouth, gastrically implanted with acoustic transmitters, non-lethally biopsied for blood biochemistry, gill Na+,K+-ATPase activity and somatic energy density and then released. Migration behaviour and travel times to the river mouth and
into the river were monitored by underwater telemetry receivers positioned at the river mouth and in the river. Post-release
survival of salmon was excellent, with 84% (N = 150) of fish reaching the furthest receiving station ∼85 km upriver. Fish from Late-summer run populations (Adams and Weaver
Creek) averaged a migration rate of ∼20 km day−1 through the marine area and held at the river mouth and adjacent areas for 7–9 days before entering the river. Summer-run
populations (Birkenhead, Chilko, Horsefly and Stellako) had a migration rate ∼33 km day−1 and held for only 1–3 days. Once in river, similar patterns were observed: Late-run populations migrated at ∼28 km day−1 and Summer-run populations at ∼40 km day−1. From point of release to the river mouth, males migrated faster than females, but once in river migration rates did not
differ between sexes. Among all females, a correlation was discovered between levels of circulating testosterone and river
entry timing. This correlation was not observed among males. Plasma K+, Cl−, glucose, lactate and osmolality were also correlated with entry timing in both sexes. 相似文献
10.
Parental investment, potential reproductive rates, and mating system in the strawberry dart-poison frog, Dendrobates pumilio 总被引:1,自引:0,他引:1
We studied the effect of relative parental investment on potential reproductive rates (PRRs) to explain sex differences in
selectivity and competition in the dart-poison frog Dendrobates pumilio. We recorded the reproductive behavior of this species in a Costa Rican lowland rainforest for almost 6 months. Females spent
more time on parental care than males, and `time out' estimates suggest that PRRs of males are much higher than than those
of females, rendering females the limiting sex in the mating process. Males defended territories that provide suitable calling
sites, space for courtship and oviposition, and prevent interference by competitors. Male mating success was highly variable,
from 0 to 12 matings, and was significantly correlated with calling activity and average perch height, but was independent
of body size and weight. Estimates of opportunity for sexual selection and variation in male mating success are given. The
mating system is polygamous: males and females mated several times with different mates. Females were more selective than
males and may sample males between matings. The discrepancy in PRRs between the sexes due to differences in parental investment
and the prolonged breeding season is sufficient to explain the observed mating pattern i.e., selective females, high variance
in male mating success, and the considerable opportunity for sexual selection.
Received: 9 June 1998 / Received in revised form: 27 March 1999 / Accepted: 3 April 1999 相似文献
11.
Brood sex ratio is dependent on female mating status in polygynous great reed warblers 总被引:2,自引:0,他引:2
Isao Nishiumi 《Behavioral ecology and sociobiology》1998,44(1):9-14
Females capable of adjusting the sex ratio of their offspring should be more fit than females lacking such an ability. In
polygynous birds where breeding success in males is more strongly influenced by body size and/or attractiveness than in females,
females might produce more sons when predicting good conditions or when mating with attractive males. Polygynous great reed
warbler, Acrocephalusarundinaceus, males direct most of their feeding effort to the primary (first-hatching) nest and in these nests increase their feeding
effort in relation to the brood sex ratio (proportion of sons). Therefore, with the expectation of well-nourished sons, we
would predict that females which start breeding first within harems might produce more sons than those which start breeding
later, and in anticipation of sons with good genes, that females mated to polygynous males might produce more sons than females
mated to monogamous males. I took blood samples from hatchlings and determined the sex using DNA markers. The sex ratio of
primary (monogamous and polygynous primary) broods is more male-biased (mean 0.58 males, n = 50) than that of secondary (polygynous secondary and tertiary) broods (mean 0.46, n = 25). Moreover, in the secondary broods with the largest clutch (five eggs), in which offspring are most likely to suffer
food shortage, the sex ratio was distinctively female biased (mean 0.33, n = 10). In the primary broods, sex ratio was correlated to harem size. The results suggest that great reed warbler females
modify the brood sex ratio to produce both well-nourished sons and sons with good genes, but the former effect is probably
stronger than the latter factor.
Received: 11 March 1998 / Accepted after revision: 23 May 1998 相似文献
12.
M. S. Mooring A. A. McKenzie Benjamin L. Hart 《Behavioral ecology and sociobiology》1996,38(4):259-266
The lesser mouse lemur (Microcebus murinus) is a prosimian primate which presents evidence of sex ratio bias of offspring that agrees with the direction of bias predicted
by the local resource competition model for facultative sex ratio adjustment. That is, females overproduced sons when grouped
prior to mating, whereas isolated females exhibited the opposite tendency. In this solitary species, social communication
relies heavily on urinary chemical signals. To test the hypothesis that sex biases induced by social factors may be linked
to urinary cues, isolated females were exposed (n = 76) or not (control group, n = 16) to urinary cues from other reproductively active females from the beginning of the breeding season (induced by long
photoperiod) until oestrus. During that period, females were either continuously (n = 17) or partially (n = 59) exposed to chemosignal stimulation. Females in oestrus were placed in contact with a breeding male and subsequently
isolated until they gave birth. All females entered oestrus but the timing of oestrus was significantly delayed by 1 week
in urine-exposed females. A general depressive effect of long-term urine exposure on fecundity was demonstrated, involving
fewer impregnations, higher abortion frequency and smaller litter sizes. Among females giving birth (n = 55) to a total of 129 young, a significant positive correlation was found between sex ratio bias towards males and the
duration of urine exposure. However, the shift in sex ratio at birth depended on the duration of urine stimulation during
a sensitive period extending from the beginning of the long photoperiod until the beginning of the follicular phase. In the
absence of urinary cues during the sensitive period, females significantly overproduced daughters (32% males of 53 newborn).
As urine exposure increased during the sensitive phase, the proportion of males in litters increased from 54% males (n = 50) in partially urine-exposed females to a significant bias towards males (69.2% of 26 newborn) in totally exposed females.
The biased sex ratio in response to chemical cues did not show consistent relationships with maternal body weight, parity
or litter size. Although the intrinsic mechanisms involved in sex-biased conceptions are not known, chemical cues could interact
with the photoperiodic control of gonadotropin secretions.
Received: 14 January 1995/Accepted after revision: 26 November 1995 相似文献
13.
Sex-specific nest defense in house sparrows (Passer domesticus) varies with badge size of males 总被引:2,自引:0,他引:2
Heinz-Ulrich Reyer Wiltrud Fischer Pascale Steck Thomas Nabulon Philip Kessler 《Behavioral ecology and sociobiology》1998,42(2):93-99
According to indicator models of sexual selection, females can benefit from choosing males with above average epigamic traits,
but empirical evidence for such benefits is scarce. Here, we report results from an experiment with 29 pairs of house sparrows
(Passer domesticus) where the intensity of nest defense against a mounted mustelid predator was related to the size of the black throat and
breast patch (“badge”) in males. Using principal components analysis (PCA), original response variables of both sexes were
reduced to two factors: “Approach” to the predator and “Distant warning”. “Approach”, the more risky behavior, increased from
small- through medium- to large-badged males and decreased in their females. Since large-badged males have a higher certainty
of paternity (i.e. greater benefits from defense) and may be older and more experienced (i.e. incur lower costs), the most
likely explanation for male defense intensity increasing with badge size is an improving benefit/cost ratio. The resulting
optimal response of their females and evolutionarily stable participation in joint parental care is illustrated by a graphical
model. It shows that females would, indeed, benefit directly from choosing large-badged males. This, however, is no proof
of a direct evolutionary tie between badge size and paternal behavior, as assumed by indicator models of sexual selection.
It may simply represent a spurious relationship, originating from the correlation of badge size and defense with confidence
of paternity.
Received: 22 September 1997 / Accepted after revision: 3 November 1997 相似文献
14.
Dorte Bekkevold Jane Frydenberg Jacobus J. Boomsma 《Behavioral ecology and sociobiology》1999,46(2):103-109
Queen mating frequency of the facultatively polygynous ant Acromyrmex echinatior was investigated by analysing genetic variation at an (AG)n repeat microsatellite locus in workers and sexuals of 20 colonies from a single Panamanian population. Thirteen colonies
were found to be monogynous, 5 colonies contained multiple queens, whereas the queen number of 2 colonies remained unresolved.
Microsatellite genotypes indicated that 12 out of 13 queens were inseminated by multiple males (polyandry). The mean queen
mating frequency was 2.53 and the mean genetically effective paternity frequency was 2.23. These values range among the highest
found in ants, and the results are in keeping with the high mating frequencies reported for other species of leafcutter ants.
Consistent skew in the proportional representation of different patrilines within colonies was found, and this remained constant
in two consecutive samples of offspring. Dissections showed that all examined queens from multiple-queen colonies were mated
egg-layers. The mean relatedness value among nestmate workers in polygynous colonies was lower than that for monogynous colonies.
No diploid males were detected in a sample of 70 genotyped males. Worker production of males was detected in one queenless
colony. We discuss our findings in relation to known patterns of multiple maternity and paternity in other eusocial Hymenoptera.
Received: 2 September 1998 / Received in revised form: 3 February 1999 / Accepted: 7 February 1999 相似文献
15.
Eugene S. Morton Bridget J. M. Stutchbury Ioana Chiver 《Behavioral ecology and sociobiology》2010,64(6):947-954
We investigated sexual conflict over parental care in blue-headed vireos (Vireo solitarius) and documented the first example of unvarying unisexual brood desertion in passerines. Females at all nests (N = 24) that were monitored closely near fledgling, deserted their broods on or near the day of fledging leaving males alone
to complete parental care of young. No males deserted. This observational evidence was confirmed with radiotracking of females
(2004, 2007) and both pair members (2008). Radiotracked females began visiting distant males 1–4 days before young left the
nest, subsequently paired with males 355–802 m away, and laid first eggs in new nests less than 5 days after deserting. In
contrast, females suffering nest predation did not desert and renested with the same male. We suggest equal parental care
(nest building, incubation, feeding) in the sexes, genetic monogamy, and an adult sex ratio biased towards males has led to
female control of brood desertion in this species. Unisexual desertion may be more important in altricial birds than generally
realized and we discuss prerequisites to predict its occurrence. One is genetic monogamy, which may be a female tactic that
reduces the likelihood of males evolving counter-adaptations to female desertion. 相似文献
16.
In an experimental set-up, a colony of the stingless bee Melipona fasciata demonstrated its ability to choose the better of two nectar sources. This colony pattern was a result of the following individual
behavioural decisions: continue foraging, abandon the feeder, restart foraging and initiate foraging. Only very rarely did
individuals switch from one feeder to the other. With the first combination of a rich (2.7 M) and a poor (0.8 M) feeder M. fasciata behaved differently from Apis mellifera. Recruitment occurred to both feeders and the poor feeder was not abandoned completely. When the poor feeder was set to 0.4 M,
M. fasciata abandoned the poor feeder rapidly and allocated more foragers to the rich feeder. These patterns were similar to those reported
for A. mellifera with the first combination of feeders. Over a sequence of 4 days, experienced bees increasingly determined the colony patterns,
and the major function of communication between workers became the reactivation of experienced foragers. The foragers modulated
their behaviour not only according to the profitability of the feeder, but also according to previous experience with profitability
switches. Thus, experience and communication together regulated colony foraging behaviour. These findings and the results of studies with honeybees suggest
that M. fasciata and honeybees use similar decision-making mechanisms and only partly different tools.
Received: 21 December 1998 / Accepted: 5 January 1999 相似文献
17.
We examined the mating behaviour of the New Zealand ocypodid crab Macrophthalmus hirtipes in the laboratory between February and June 1998. This species has a discrete breeding season. Mating and moulting were not
linked and only intermoult females with mobile gonopore opercula were attractive to males. Allometry and compatibility of
gonopods and gonopores of different-sized crabs was investigated. Under laboratory conditions, the opercula of intermoult
females remained mobile on average for 11.4 d, but the duration of receptivity did not appear to be under female control.
The operational sex ratio in the laboratory fluctuated greatly, but was always male-dominated. During the period of opercular
mobility, females mated many times with several different males. Matings in the absence of burrows were relatively short (mean
duration = 23 min, max. = 122 min) and the mating behaviour of M. hirtipes lacked courtship and mate-guarding. Males used a search-intercept method to acquire mates, with very low levels of intrasexual
competition. There was no evidence of mate preference in M. hirtipes, and males spent just as long mating with ovigerous females as with non-ovigerous ones. Although M. hirtipes has ventral-type spermathecae, as do several other ocypodid crabs, it is unclear whether this promotes last-male sperm precedence.
The role of burrows in modifying the mating behaviour of M. hirtipes in the field remains to be established.
Received: 7 January 2000 / Accepted: 5 June 2000 相似文献
18.
K. Reinhold 《Behavioral ecology and sociobiology》1996,39(3):189-194
Offspring sex ratio at hatching was examined in the bushcricket Poecilimon veluchianus. Offspring sex ratios varied significantly between females (Fig. 1). Low mortality prior to sex determination established
that this heterogeneity was already present in the primary offspring sex ratio. Sperm age and female age had no influence
on offspring sex ratio (Fig. 2). Male age at copulation, however, correlated significantly with offspring sex ratio (Fig. 3).
There were two types of males: one type produced predominantly daughters when young and an increasing proportion of sons with
age. The other type produced, independent of age, 1:1 offspring sex ratios (Fig. 4). The two types of males seem to occur
in approximately equal numbers. Sex ratio variation (1) may adaptively compensate for local sex ratio biases caused by sex-specific
motility, or (2) it may be adaptive if there is a sex-differential effect of laying date on offspring fitness.
Received: 14 March 1996/Accepted after revision: 24 June 1996 相似文献
19.
Lasioglossum laevissimum was studied in Calgary, Alberta, where it is eusocial with one worker brood. Estimates of relatedness were obtained among various categories of nestmate based upon four polymorphic enzyme loci, two of which exhibited significant levels of linkage disequilibrium. Relatedness estimates among workers and among reproductive brood females were very close to the expected 0.75 value that obtains when nests are headed by one, singly mated queen. However, relatedness between workers and the reproductive brood females they reared was significantly lower than 0.75. A low frequency of orphaning with subsequent monopolisation of oviposition by one worker brood female in orphaned nests may explain these results. Workers were significantly more and queens significantly less closely related to male reproductives than expected if all males were to have resulted from queen-laid eggs. Orphaning and worker-produced males contribute to this result. The sex investment ratio was 1:2.2 in favour of females, in excellent agreement with the predictions based upon relative relatednesses between workers and reproductive brood males and females. Adaptive intercolony variation in investment ratios was detected: the sex ratio was more heavily female-biased in nests in which the relative relatedness asymmetry between workers and reproductive brood was more female-biased. The study species is the most weakly eusocial hymenopteran for which relatedness estimates and sex ratio data are available. With high relatedness among nestmates and a strongly female-biased sex ratio, this study suggests the importance of indirect fitness contributions in the early stages of social evolution.
Correspondence to: L. Packer 相似文献
20.
Both cooperation and conflict between the sexes are commonplace in monogamous mating systems. However, little is known about
how cooperation and competition varies seasonally in monogamous species that maintain permanent territories. We presented
territorial pairs of male and female New Zealand robins (Petroica australis) with a large supply of insect prey at monthly intervals for 2 years. Behavioural observations after food presentation were
then made to quantify seasonal and sexual differences in aggressive interactions over prey, prey acquisition rates, mate provisioning,
offspring provisioning, selfish food hoarding and cache retrieval. Data were used to evaluate sex-specific behavioural strategies
of mediating competition for food. Results showed that males aggressively excluded females from experimental food sources
year-round. Females only accessed food sources when males left them unattended. Consequently, females acquired fewer prey
than males. After controlling for differences in prey acquisition, both sexes consumed similar amounts of prey in the non-breeding
season. Even though males aggressively excluded females from accessing food sources directly, males fed large amounts of prey
to females during the breeding season. Both sexes provisioned young at similar rates. Males cached less prey than females
in the breeding season but more prey than females in the non-breeding season. Females showed similar caching intensities year-round.
Although males tried to defend their hoards, females frequently retrieved male-made caches. Overall, results showed that although
New Zealand robins cooperate to raise offspring during the breeding season, conflict between the sexes occurs year-round.
Males and females display different behavioural strategies to gain access to experimental food sources, which appear to lessen
male–female competition for food and evenly distribute food resources between the sexes. 相似文献