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1.
Secondary sexual characters often provide indicators of a male’s resistance to infectious diseases to rivals and potential
mates, but it is unclear why. It is often suggested that males honestly signal their health due to energetic and other physiological
trade-offs between investing into secondary sexual traits vs resistance to infectious diseases. Our aim was to determine whether
such a trade-off exists using wild-derived male house mice (Mus domesticus). We exposed male mice to female scent, a manipulation that induces elevations in testosterone concentration and the expression
of a variety of testosterone-mediated secondary sexual traits, and tested whether this sexual stimulation impaired the males’
ability to resolve or cope with an experimental infection (Salmonella enterica). We kept the males on a controlled diet to prevent them from compensating by eating more food. We found that sexually stimulated
males were able to control bacterial growth as effectively as sham-stimulated controls; however, to do so, they lost more
body mass during infection compared to the controls. In contrast, we found no evidence that sexual stimulation reduced the
body mass of uninfected male mice. These results indicate that males’ responses to female odor are not immunosuppressive per
se, yet they increase the energetic costs of controlling infection. Our findings support the idea that there is a physiological
trade-off between secondary sexual signaling vs resistance to infectious diseases and suggest that studies using only immunocompetence
assays might fail to detect such energetic trade-offs.
We dedicate this paper to the late Professor Chris Barnard who conducted pioneering research on this topic. 相似文献
2.
Correlating seabird movements with ocean winds: linking satellite telemetry with ocean scatterometry
Satellite telemetry studies of the movements of seabirds are now common and have revealed impressive flight capabilities and extensive distributions among individuals and species at sea. Linking seabird movements with environmental conditions over vast expanses of the world’s open ocean, however, remains difficult. Seabirds of the order Procellariiformes (e.g., petrels, albatrosses, and shearwaters) depend largely on wind and wave energy for efficient flight. We present a new method for quantifying the movements of far-ranging seabirds in relation to ocean winds measured by the SeaWinds scatterometer onboard the QuikSCAT satellite. We apply vector correlation (as defined by Crosby et al. in J Atm Ocean Tech 10:355–367, 1993) to evaluate how the trajectories (ground speed and direction) for five procellariiform seabirds outfitted with satellite transmitters are related to ocean winds. Individual seabirds (Sooty Shearwater, Pink-footed Shearwater, Hawaiian Petrel, Grey-faced Petrel, and Black-footed Albatross) all traveled predominantly with oblique, isotropic crossing to quartering tail-winds (i.e., 105–165° in relation to birds’ trajectory). For all five seabirds, entire track line trajectories were significantly correlated with co-located winds. Greatest correlations along 8-day path segments were related to wind patterns during birds’ directed, long-range migration (Sooty Shearwater) as well as movements associated with mega-scale meteorological phenomena, including Pacific Basin anticyclones (Hawaiian Petrel, Grey-faced Petrel) and eastward-propagating north Pacific cyclones (Black-footed Albatross). Wind strength and direction are important factors related to the overall movements that delineate the distribution of petrels at sea. We suggest that vector correlation can be used to quantify movements for any marine vertebrate when tracking and environmental data (winds or currents) are of sufficient quality and sample size. Vector correlation coefficients can then be used to assess population—or species-specific variability and used to test specific hypotheses related to how animal movements are associated with fluid environments. 相似文献
3.
Antonia Köhler Philipp Hildenbrand Elke Schleucher Rüdiger Riesch Lenin Arias-Rodriguez Bruno Streit Martin Plath 《Behavioral ecology and sociobiology》2011,65(8):1513-1523
Sexual harassment by males has the potential to affect almost any aspect of female behavior and life history. Using Atlantic
mollies (Poecilia mexicana) as a model—a species in which males do not court but almost constantly try to forcefully mate with females—we asked whether
and how male harassment influences (a) females’ time budgets and (b) feeding rates (e.g., through frequent flight from male
approaches), and (c) whether metabolic rates are increased as a response to stress. Field observations in a natural P. mexicana population revealed that males (average feeding rate 15%) spent far less time feeding than females (60%), and clearly traded
off frequent pursuit of females with foraging. Most importantly, females’ feeding times were dramatically reduced when being
pursued by a harassing male. Also in standardized lab experiments, females spent significantly less time feeding when accompanied
by a male as compared to being in the presence of another female. This effect was also observed when partner fish (male or
female) were presented only visually, but could not interact physically with the focal female. It seems, therefore, that females
increase vigilance when a harassing male is around, which keeps them from feeding even before males actually approach them.
Based on the latter result, we asked whether a stress-induced increase in metabolic rates would be discernible. We measured
oxygen consumption and gill ventilation frequencies (opercular rates) of females in different social contexts (alone, with
another female, or a male). The predicted, strong body mass dependency of both physiological parameters was uncovered, but
no evidence for an effect of social context was detected. We argue that male harassment represents such a constant (but non-lethal)
stressor for poeciliid females that their metabolic stress responses have adapted to this through habituation. 相似文献
4.
Tsuyoshi Takeuchi 《Behavioral ecology and sociobiology》2011,65(8):1559-1566
Male butterflies compete over mating territories via aerial interactions. It has often been suggested that flight performance,
and thus flight-related traits, would play an important role in butterflies’ contest resolution; however, most studies have
not demonstrated a clear relationship between these traits and territory ownership in butterflies. Males of the satyrine butterfly
Lethe diana compete over territories via linear chases, a behavior that is uncommon among butterflies: rather, contests of most butterfly
species consist of circling flights. In the present study, some morphological and physiological traits of L. diana were compared between territory owners and intruders to search for traits correlated with resource holding power (RHP). Territory
owners had higher flight-muscle ratio (FMR) and were heavier than intruders, indicating that flight performance plays a key
role in their contest resolution. Contest duration was not affected by the owners’ FMR or body mass, and thus I obtained no
evidence supporting the hypothesis that contestants assess their relative RHP before making a decision to retreat. I speculate
that the fact that these traits had an effect on territorial status in L. diana was a result of the characteristics of the contest behavior of this butterfly. During their contests, males L. diana fly faster in their linear flights than males of most other butterflies, which engage in slower circling flights. Therefore,
males of L. diana probably need higher flight performance capabilities in order to win their contests. 相似文献
5.
Sonja E. Koski 《Behavioral ecology and sociobiology》2011,65(11):2161-2174
Animals of many species show consistency in behaviour across time and contexts that differs from other individuals' behaviour
in the same population. Such ‘personality’ affects fitness and has therefore become an increasingly relevant research topic
in biology. However, consistent variation in social behaviour is understudied. In socially living species, behaviour occurs
in a social environment and social interactions have a significant influence on individual fitness. This study addressed personality
in social behaviour of 75 captive chimpanzees in three zoos by coding observed behaviour. Fifteen behavioural variables were
significantly repeatable (range 0.21–0.93) in at least two of the three zoos. The behaviours showed considerable long-term
stability across 3 years, which did not differ from the short-term repeatability. The repeatable behaviours were then analysed
with factor analyses. They formed five independent factors, three of which consisted of social traits and were labelled ‘sociability’,
‘positive affect’ and ‘equitability’. The two non-social behaviour factors were labelled ‘anxiety’ and ‘activity’. The factor
scores were analysed for sex and population differences. Males had higher factor scores in all traits except ‘sociability’.
The factor scores differed also between the zoos, implying considerable external effects in trait expression. The results
show that chimpanzees show personality in a broad range of social and non-social behaviours. The study highlights the importance
of assessing personality in the social behaviour, especially in cohesive social species, as only then can we understand the
consequences of personality in socially living species. 相似文献
6.
In many species, the ability to evade predators is known to be periodically impaired by increased weight loads due to feeding
and reproduction. Not only may extra weight reduce escape speed, but feeding and mating can also make the prey more noticeable
to visually hunting predators. A number of butterfly species mate for hours, and if a mating couple is disturbed, one of the
butterflies is responsible for flying, whereas its partner remains still. This study investigated the ability of male Pieris napi butterflies to fly while mating, with the prediction that mate carrying impairs flight ability compared to single flying
males and that males with relatively high flight muscle ratios (FMR; male thorax mass/male + female body mass) will have better
flight performance in copula. Our results clearly show that whereas single males always take off at steep angles and fly upwards,
couples invariably have a negative take-off angle and rarely gain height. Moreover, landing height of the couples is positively
associated with higher FMR. Hence, male flight ability when in copula is positively associated with a high relative thorax
mass. Butterfly pairs may thus be at greater risk of predation as a consequence of their impaired flight ability, especially
couples with critically low FMRs (<16%). 相似文献
7.
Adjustment of parental effort to manipulated foraging ability in a pelagic seabird,the thin-billed prion Pachyptila belcheri 总被引:6,自引:0,他引:6
Henri Weimerskirch Olivier Chastel Luc Ackermann 《Behavioral ecology and sociobiology》1995,36(1):11-16
An experiment was designed to examine in a long-lived seabird, the thin-billed prion (Pachyptila belcheri), how adults adjust their food provisioning strategy when their foraging abilities are reduced and when the chick's needs are increased. To reduce the foraging abilities of adults we impaired their flying ability by removing some flight feathers (handicapped), and to increase the food needs of the chick one parent was retained (single). Birds made either short foraging trips lasting 1–3 days, or long trips lasting 5–9 days. Control birds alternated long and short trips whereas single birds or handicapped birds made several successive short trips and thereafter a long trip. In each treatment, food loads tended to be heavier after long trips than after short trips, and single birds tended to bring heavier loads than control or handicapped birds. Birds in the three treatments lost similar amounts of mass after short trips and gained similar amounts of mass after long trips. However, the mass of handicapped birds declined through the experiment, while that of control and single birds remained stable. Although the proportion of chicks that died during the experiment was similar among the three treatments, the chicks fledged by a single bird were lighter than those in control nests. The results of the experiment suggest that thin-billed prions adjust their breeding effort differently to decreased flying ability or increased food demand by the chick. Single birds increase foraging effort without allowing their condition to deteriorate. Conversely, handicapped birds are unable to maintain their body condition while sustaining the chick at the same rate as control birds. It is suggested that in this long-lived seabird, adults probably adjust their breeding effort so that they do not incur the risk of an increased mortality, this risk being monitored by the body condition. 相似文献
8.
The non-random movement patterns of foraging bees are believed to increase their search efficiency. These patterns may be
innate, or they may be learned through the bees’ early foraging experience. To identify the innate components of foraging
rules, we characterized the flight of naive bumblebees, foraging on a non-patchy “field” of randomly scattered artificial
flowers with three color displays. The flowers were randomly mixed and all three flower types offered equal nectar volumes.
Visited flowers were refilled with probability 0.5. Flight distances, flight durations and nectar probing durations were determined
and related to the bees’ recent experiences. The naive bees exhibited area-restricted search behavior, i.e., flew shorter
distances following visits to rewarding flowers than after visits to empty flowers. Additionally, flight distances during
flower-type transitions were longer than flight distances between flowers of the same type. The two movement rules operated
together: flight distances were longest for flights between flower types following non-rewarding visits, shortest for within-type
flights following rewarding visits. An increase in flight displacement during flower-type shifts was also observed in a second
experiment, in which all three types were always rewarding. In this experiment, flower-type shifts were also accompanied by
an increase in flight duration. Possible relationships between flight distances, flight durations and flower-type choice are
discussed.
Received: 20 November 1995/Accepted after revision: 10 May 1996 相似文献
9.
Melanie Schubert Carsten Schradin Heiko G. Rödel Neville Pillay David O. Ribble 《Behavioral ecology and sociobiology》2009,64(2):257-264
Mate guarding is predicted to be one of the driving forces for the evolution of monogamy, but supporting evidence in free-living
mammals is rare. The goals of our study were three-pronged. First, we tested if mate guarding, measured as intrapair distance,
occurs as a behavioral tactic in round-eared sengis (Macroscelides proboscideus), a socially monogamous species lacking paternal care and in which females breed asynchronously, producing 2–3 litters during
an 8-month long breeding season. Second, we determined if mate guarding involves costs which we identified as changes in male
body mass. Third, we investigated whether variation in individual investment in mate guarding depended on the males’ body
mass and the number of neighboring males. Field data were collected in a semidesert in South Africa using radio-tracking,
trapping, and direct observations during three successive breeding seasons. Mate guarding strongly depended on the females’
reproductive state, and all males started to guard their mates prior to and during estrus, as exemplified by reduced intrapair
distance. Mate guarding incurred costs: overall, males lost about 5% of body mass. Male body mass loss and initial body mass
were negatively related to the intensity of precopulatory mate guarding. Furthermore, during estrus intrapair distance was
inversely correlated with the number of neighboring males. The results show that mate guarding is the predominant male tactic
in round-eared sengis. However, since mate guarding imposed costs, males may balance benefits and costs associated with guarding
by varying their effort in relation to their physical capabilities and the competitive environment. 相似文献
10.
Management of fat reserves in tufted titmice (Parus bicolor ): evidence against a trade-off with food hoards 总被引:2,自引:0,他引:2
Caching species can manage their energy supply by adjusting body fat, number of caches, or both. It has been hypothesized
that because body fat has a higher fitness cost than caches, small food-hoarding birds respond to increased starvation risk
by increasing the number of their caches rather than their fat load. This hypothesis predicts that when birds cannot cache
they should compensate for the loss of external energy storage by (1) shifting the time of their daily body mass accumulation
toward earlier in the day and (2) increasing the overall level of their fat reserves. During the winter of 1995–1996, we tested
these predictions with a caching species, the tufted titmouse (Parus bicolor). Each of six experimental birds was fed a diet of uncachable sunflower seed powder for 6 days, preceded and followed by
6-day control periods during which they were fed cachable sunflower seeds. The daily pattern of body mass gain was unaffected
by the opportunity to cache. Furthermore, when unable to cache, the birds did not increase either their mean daily body mass,
body mass in the middle of the day, or evening body mass compared to the two control periods. These results argue against
the hypothesis of a trade-off between fat reserves and food caches in tufted titmice, and suggest that fat reserves are managed
independently of external food caches.
Received: 9 April 1997 / Accepted after revision: 30 August 1997 相似文献
11.
Theoretical models predict that parents should adjust the amount of care both to their own and their partner’s body condition.
In most biparental species, parental duties are switched repeatedly allowing for repeated mutual adjustment of the amount
of care. In the mouthbrooding cichlid Eretmodus cyanostictus, terms are switched only once with females taking the first share. The timing of the shift of the clutch between mates strongly
determines both partners’ brooding period and thereby their parental investment. Females signal their readiness to transfer
the young several days before the male finally takes them, suggesting sexual conflict over the timing of the shift. In a lab
experiment, we reduced the body condition of either the female or the male of a pair to test whether energy reserves affect
the timing of the shift and whether female signalling behaviour depends on energetic state. Males with a lowered condition
took the young later and incubated for a shorter period, which prolonged the incubation time of their female partners. When
female condition was lowered, female and male incubation durations remained unchanged, although females signalled their readiness
to shift more intensely. Our results suggest that males adjust their parental investment to own energy reserves but are unresponsive
to their mate’s condition. Females appear to carry the entire costs for the male’s adjustment of care. We propose that intrinsic
asymmetries in the scope for mutual adjustment of parental investment and the costs of negotiation crucially influence solutions
of the conflict between sexes over care. 相似文献
12.
Vitor H. Paiva Pedro Geraldes Iván Ramírez Ana Meirinho Stefan Garthe Jaime A. Ramos 《Marine Biology》2010,157(6):1385-1399
Many breeding seabird species are central-place foragers and constrained to find productive prey patches within their foraging
ranges. We assessed how different populations of a pelagic seabird species, the Cory’s shearwater Calonectris diomedea, breeding in oceanic and neritic conditions, cope with these constraints in the North Atlantic, during both incubation and
chick-rearing periods. We analysed 237 foraging trips to study the movements and oceanographic characteristics of foraging
habitats of seven different populations of Cory’s shearwaters. Generally, oceanic populations exhibited higher foraging effort,
by travelling more time and to more distant areas, and larger home ranges and feeding areas, than the neritic population (i.e.
breeding on an island within the Portuguese continental platform). On their short trips (i.e. ≤4 days), birds from the different
populations fed mostly in shallower waters around the colony. During long trips (i.e. ≥5 days), feeding areas of both oceanic
and neritic populations were characterized by high concentration values of chlorophyll-a, low sea-surface temperature and shallower habitats, with oceanic populations of the Azores exploiting areas north of the
islands over known seamounts and frontal regions. Birds from other oceanic population (Selvagens) also exploited the African
continental shelf system on their long trips. The home ranges of the different populations overlapped widely, but there was
a general spatial segregation in terms of the core feeding areas at the population level. Core feeding areas and areas of
foraging overlap between different populations should be important to inform conservation management measures, such as the
definition of Marine Important Bird Areas for seabirds over the North Atlantic. 相似文献
13.
Martin Philippe-Lesaffre Martin Thibault Stephane Caut Karen Bourgeois Tristan Berr Andreas Ravache Eric Vidal Franck Courchamp Elsa Bonnaud 《Conservation biology》2023,37(3):e14042
Seabirds have been particularly affected by invasive non-native species, which has led to the implementation of numerous eradication campaigns for the conservation of these keystone and highly vulnerable species. Although the benefits of eradication of invasive non-native species for seabird conservation have been demonstrated, the recovery kinetics of different seabird populations on islands after eradication remains poorly evaluated. We conducted long-term monitoring of the number of breeding pairs of seven seabird species on a small atoll, Surprise Island, New Caledonia (southwestern tropical Pacific). Marine avifauna of the island were surveyed yearly 4 years before to 4 years after rodent eradication (conducted in 2005), and we conducted multiple one-time surveys from ∼10 years before and ∼15 years after eradication. We sought to determine how different seabird species responded to the eradication of invasive rodents in an insular environment. Three species responded positively (two- to 10-fold increase in population size) to eradication with differences in lag time and sensitivity. The number of breeding pairs increased (effect sizes = 0.49–0.95 and 0.35–0.52) for two species over 4 years post-eradication due to immigration. One species had a longer (at least 5 years) response time than all others; breeding pairs increased for over 10 years after eradication. Long-term sampling was necessary to observe the responses of the seabird populations on the island because of the delayed response of a species to eradication not visible in the first years after eradication. Our results confirmed the positive effects of eradication of invasive non-native species on seabirds and emphasize the importance of mid- and long-term pre- and posteradication surveys to decipher the mechanisms of seabird recovery and confirm the benefits of eradication for conservation purposes. 相似文献
14.
Ø. Holand R. B. Weladji K. H. Røed H. Gjøstein J. Kumpula J.-M. Gaillard M. E. Smith M. Nieminen 《Behavioral ecology and sociobiology》2006,59(5):682-688
The manipulation of the sex ratio and age structure in many managed ungulate populations calls for a better understanding
of their potential consequences on females’ condition and behavior during rut. During 1996–2002, we manipulated the male age
structure and male percentage (nine treatments during 7 years) within an experimental herd of semidomestic reindeer (Rangifer tarandus) and investigated their influence on both the body mass change and the behavior of females during rut. On average, the females
lost body mass (−0.95±SE 0.18 kg) during rut, which we contend to reflect somatic costs. The females’ losses increased as
the percentage of male decreased, but this was certainly ascribed to one treatment with high male percentage (27.7%) as compared
to the others (ranging from 3.9 to 12.2%). Female losses were highest for treatments including both young and adult males
as compared to only adult or only young males, and higher for treatments including only young compared to only adult males.
This is supported by (1) the higher female harassment frequency when females are exposed to only young or a mixture of young
and adult males as compared to only adults, (2) the higher female harassment frequency by young males as compared to adults
in the mixed treatments, and (3) the reduced females’ feeding activity in treatments including both young and adult males.
We conclude that the male age structure during rut will influence the females’ behavior and mass change and may have implications
for females’ life history and for population dynamics. 相似文献
15.
The contents of free amino acids (FAA) and total protein, together with growth and gut-content, of turbot (Scophthalmus maximus L.) larvae reared at 14, 18 and 22 °C were studied from first-feeding to approximately 140 effective day-degrees post hatch
(Deff
∘). Artemia franciscana nauplii and two species of rotifers were used as prey. Protein content accounted for about 42 and 26% of dry body mass in
the A. franciscana nauplii and the rotifers, respectively. The FAA pool constituted 5.6 and 4.8% of the total amino acids in the same animals.
The dry body mass of turbot larvae was exponentially related to Deff
∘. Protein and FAA contents were linearly related to dry body mass, and were independent of rearing temperature between 14
and 18 °C. At the end of the experiment, however, turbot larvae at 22 °C had lower gut content values, retarded growth rates,
and decreased FAA contents and concentrations. Thus, at this high temperature, turbot larvae seem unable to catch and ingest
sufficient prey, or to sustain an amino acid assimilation rate from the intestine sufficient to meet metabolic demands.
Received: 2 January 1997 / Accepted: 25 September 1998 相似文献
16.
Tug-of-war over reproduction in a cooperatively breeding cichlid 总被引:1,自引:0,他引:1
In group-living animals, dominants may suppress subordinate reproduction directly and indirectly, thereby skewing reproduction
in their favour. In this study, we show experimentally that this ability (‘power’) is influenced by resource distribution
and the body size difference between unrelated dominants and subordinates in the cichlid Neolamprologus pulcher. Reproduction was strongly skewed towards the dominant female, due to these females producing more and larger clutches and
those clutches surviving egg eating better than those of subordinate females, but was not so when subordinates defended a
patch. If breeding shelters were provided in two patches, subordinate females were more likely to exclusively defend a patch
against the dominant female and breed, compared to when the same breeding resource was provided in one patch. Relatively large
subordinate females were more likely to defend a patch and reproduce. Females also directly interfered with each other’s reproduction
by eating the competitors’ eggs, at which dominants were more successful. Although dominant females benefited from subordinate
females due to alloparental care and an increase in egg mass, they also showed costs due to reduced growth in the presence
of subordinates. The results support the view that the dominant’s power to control subordinate reproduction determines reproductive
partitioning, in agreement with the predictions from tug-of-war models of reproductive skew. 相似文献
17.
Joan Navarro Maite Louzao José Manuel Igual Daniel Oro Antonio Delgado José Manuel Arcos Meritxell Genovart Keith A. Hobson Manuela G. Forero 《Marine Biology》2009,156(12):2571-2578
Pelagic seabirds obtain food from oceans where the availability of their prey changes rapidly both seasonally and spatially.
Here, we investigated changes in the trophic habits of the critically endangered Balearic shearwater (Puffinus mauretanicus) through the breeding season and tested for dietary differences between sexes and age classes. We analysed δ15N and δ13C values in blood of adults during the pre-incubation, incubation and chick-rearing periods and of their chicks. Using a two-isotope
mixing model, we estimated dietary contributions based on isotope values from potential prey species which included small
pelagic species available naturally and demersal fish species available only from trawling discards. Balearic shearwaters
showed clear isotopic and dietary variation through the breeding season. During pre-incubation, breeding adults appeared to
exploit demersal fish, whereas during the incubation and chick-rearing period, they fed mainly on pelagic anchovies (Engraulis encrasicolus) and pilchards (Sardina pilchardus). Similarly, chicks were fed mainly with anchovies, a resource with a high energetic value. This variation in the dietary
habits of adult shearwaters during the breeding season was probably related to both natural and fishery-induced seasonal changes
in the availability of potential prey species within their main feeding grounds. However, changes in the nutritional requirements
of the shearwaters could also play an important role. Indeed, diet differed between sexes during pre-incubation: females fed
less on trawling discards and more on small pelagic fish than males. This sexual segregation in diet could be the consequence
of higher nutritional requirements of females during this period. Our study reveals the differential importance of both trawling
discards and small pelagic fish species for a pelagic seabird depending on the breeding period and illustrates the importance
of considering the entire breeding season when making inferences about the importance of specific prey in seabird dietary
studies. 相似文献
18.
External devices on penguins: how important is shape? 总被引:4,自引:0,他引:4
Many researchers use external recording or transmitting devices to elucidate the marine ecology of fish, mammals and birds. Deleterious effects of these instruments on the parameters researchers wish to measure are hardly ever discussed in the literature. Research has shown that, in penguins, volume and cross-sectional area of instruments negatively correlate with swimming speed. dive depth and breeding success, and that device colour affects bird behaviour. Here, a large (200 g, cross-sectional area 2100 mm2) streamlined device was attached to the lower back of Adélie penguins (Pygoscelis adeliae on Ardley Island, South Shetland Island in 1992) and its effects on bird swimming speed and energetics were measured in a water canal in Antarctica. Although the device was 10.5% of penguin cross-sectional area, swimming speed was reduced by only 8.3% and mean power input increased by only 5.6% while swimming. Although our streamlined device was five times more voluminous than one of our older units, the effect on swimming energetics could be reduced by 87%. 相似文献
19.
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