scholarly journals Variable fledging age according to group size: trade-offs in a cooperatively breeding bird

2007 ◽  
Vol 3 (6) ◽  
pp. 624-627 ◽  
Author(s):  
N.J Raihani ◽  
A.R Ridley
Keyword(s):  
Group Size ◽  
Group Living ◽  
Breeding Bird ◽  
Communal Roost ◽  
Trade Offs ◽  
Efficient Detection ◽  
Risk Of Predation ◽  
Cooperatively Breeding ◽  
Individual Survival ◽  
Dilution Effects

Group living can provide individuals with several benefits, including cooperative vigilance and lower predation rates. Individuals in larger groups may be less vulnerable to predation due to dilution effects, efficient detection or greater ability to repel predators. Individuals in smaller groups may consequently employ alternative behavioural tactics to compensate for their greater vulnerability to predators. Here, we describe how pied babbler ( Turdoides bicolor ) fledging age varies with group size and the associated risk of nestling predation. Nestling predation is highest in smaller groups, but there is no effect of group size on fledgling predation. Consequently, small groups fledge young earlier, thereby reducing the risk of predation. However, there is a cost to this behaviour as younger fledglings are less mobile than older fledglings: they move shorter distances and are less likely to successfully reach the communal roost tree. The optimal age to fledge young appears to depend on the trade-off between reduced nestling predation and increased fledgling mobility. We suggest that such trade-offs may be common in species where group size critically affects individual survival and reproductive success.

scholarly journals Vigilance behavior of pyrenean chamois Rupicapra pyrenaica pyrenaica: Effect of sex and position in the herd

2010 ◽  
Vol 56 (2) ◽  
pp. 232-237 ◽  
Author(s):  
Antoni Dalmau ◽  
Alfred Ferret ◽  
Xavier Manteca
Keyword(s):  
Social Interactions ◽  
Group Size ◽  
Group Living ◽  
Advantages And Disadvantages ◽  
Rupicapra Pyrenaica ◽  
Vigilance Behavior ◽  
Focal Animal ◽  
Risk Of Predation ◽  
Pyrenean Chamois ◽  
Optimal Group Size

Abstract The Pyrenean chamois Rupicapra pyrenaica pyrenaica is a mountain-dwelling ungulate with an extensive presence in open areas. Optimal group size results from the trade off between advantages (a reduction in the risk of predation) and disadvantages (competition between members of the herd) of group living. In addition, advantages and disadvantages of group living may vary depending on the position of each individual within the herd. Our objective was to study the effect of central vs. peripheral position in the herd on feeding and vigilance behavior in male and female Pyrenean chamois and to ascertain if a group size effect existed. We used focal animal sampling and recorded social interactions when a focal animal was involved. With males, vigilance rate was higher in the central part of the group than at the periphery, probably due to a higher density of animals in the central part of the herd and a higher probability of being disturbed by conspecifics. With females, vigilance rate did not differ according to position in the herd. Females spent more time feeding than males, and males showed a higher frequency of the vigilance behavior than females. We did not observe a clear relationship between group size and vigilance behavior. The differences in vigilance behavior might be due to social interactions.

Grouping patterns in warthogs, Phacochoerus africanus: is communal care of young enough to explain sociality?

Behaviour ◽  
2010 ◽  
Vol 147 (1) ◽  
pp. 1-18 ◽  
Author(s):  
Mary Peacock ◽  
Angela White ◽  
Elissa Cameron
Keyword(s):  
Group Composition ◽  
Group Living ◽  
Living Will ◽  
Lifetime Reproductive Success ◽  
Adult Males ◽  
Trade Offs ◽  
Cooperatively Breeding ◽  
Phacochoerus Africanus ◽  
Time Of Year ◽  
Communal Rearing

AbstractGroup-living will evolve when individuals increase their lifetime reproductive success by joining with other individuals. In cooperatively breeding societies, individuals living in a group will participate in the communal rearing of young. Several factors can influence the evolutionary trade-offs of grouping and it is often unclear whether cooperative breeding is advantageous or is simply a by-product of selection acting on grouping behaviour. We used sightings of 1318 warthogs in 711 groups to investigate whether the advantages of sociality in the warthog differ depending on an individual's age, sex, reproductive state, or the time of year. Adult males only formed temporary associations with other individuals indicating that participation in a group was not advantageous. In contrast, yearlings were almost inevitably found in groups, regardless of their sex or time of year, suggesting any costs to sociality were outweighed by the benefits. Grouping in adult female warthogs was complex; adult females were more likely to form groups in the presence of juveniles and when juveniles were at their most vulnerable stage indicating that sociality in females could be partially explained by the benefits of communal care of young. However, other factors influenced female cooperation including group composition and the time of year.

scholarly journals Compensatory and additive helper effects in the cooperatively breeding Seychelles warbler (Acrocephalus sechellensis)

2018 ◽  
Author(s):  
Lotte A. van Boheemen ◽  
Martijn Hammers ◽  
Sjouke A. Kingma ◽  
David S. Richardson ◽  
Terry Burke ◽  
...  
Keyword(s):  
Group Size ◽  
Food Availability ◽  
Dominant Male ◽  
List Type ◽  
Territory Quality ◽  
Trade Offs ◽  
Cooperatively Breeding ◽  
Helping Behaviour ◽  
Seychelles Warbler ◽  
The Impact

ABSTRACTIn cooperatively breeding species, helper aid may affect dominant breeders’ investment trade-offs between current and future reproduction. By compensating for the care provided by helpers, breeders can reduce the costs of reproduction and improve chances of survival. Also, helper care can be additive to that of dominants, resulting in higher success of the current brood.However, the influence of helpers on offspring care itself may be the by-product of group size and territory quality. Therefore to make conclusive inferences about causation of additive and compensatory care as a result of helpper serequires disentangling the impact of helping from other factors determining parental investment.In this study, we use 20 years of offspring provisioning data to investigate the effect of helping on breeder and overall offspring provisioning rates in the facultative cooperatively breeding Seychelles warbler (Acrocephalus sechellensis). Our extensive dataset allowed us to effectively control for the effects of living in a larger group and in territories with higher food availability.We show compensatory and additive care in response to helper aid. Helpers lightened the provisioning load of the dominant male and female and increased the total provisioning to the nestlings. This was irrespective of group size or territory quality (food availability).Our results illustrate how multiple benefits of helping behaviour can simultaneously be fundamental to the evolutionary maintenance of cooperative behaviour.

scholarly journals Nest predation predicts infanticide in a cooperatively breeding bird

2019 ◽  
Vol 15 (8) ◽  
pp. 20190314
Author(s):  
Yi-Ru Cheng ◽  
Dustin R. Rubenstein ◽  
Sheng-Feng Shen
Keyword(s):  
Nest Predation ◽  
Social Conflict ◽  
Alternative Hypothesis ◽  
Group Living ◽  
Breeding Birds ◽  
Breeding Bird ◽  
Parental Response ◽  
Cooperatively Breeding ◽  
Alternative Hypotheses ◽  
Living Species

In cooperatively breeding species, social conflict is typically assumed to underlie destructive behaviours like infanticide. However, an untested alternative hypothesis in birds is that infanticide in the form of egg tossing may simply be a parental response to partial nest predation representing a life-history trade-off. We examined egg tossing behaviour in the colonial and cooperatively breeding grey-capped social weaver ( Pseudonigrita arnaudi ), a plural breeder in which pairs nest separately, often in the same tree. Using infrared nest cameras, we found that 78% of the tossing events from 2012 to 2017 were committed by parents, suggesting that social conflict is unlikely to be the main reason underlying egg tossing in this species. Instead, reductions in clutch size due to both natural and experimentally simulated predation induced parental egg tossing. Our study suggests that destructive behaviour in cooperatively breeding birds can be shaped by a variety of mechanisms beyond social conflict and that alternative hypotheses must be considered when studying the adaptive significance of infanticide in group-living species.

scholarly journals Effect of group size and reproductive status on faecal glucocorticoid concentration and vigilance in a free-ranging population of Przewalski’s gazelle

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Ruoshuang Liu ◽  
Jianbin Shi ◽  
Dingzhen Liu ◽  
Shikui Dong ◽  
Yu Zhang ◽  
...  
Keyword(s):  
Group Size ◽  
Group Living ◽  
Reproductive Status ◽  
Qinghai Lake ◽  
Management Measures ◽  
Antipredator Responses ◽  
Individual Survival ◽  
High Level ◽  
Free Ranging ◽  
Procapra Przewalskii

Abstract Elevated glucocorticoid (GC) concentration and increased vigilance are two common responses to predation risk in mammals. Chronic high-level GC concentration and vigilance occur at the expense of other life maintenance and reproduction activities, reflecting a trade-off between individual survival and future fecundity. Przewalski’s gazelle (Procapra przewalskii) is a group-living ungulate endemic to the high-altitude Qinghai Lake region of China. Group-size effect on gazelle vigilance has been examined, yet little is known about how their GC concentration is affected by group size or reproductive status. In this study, we examined the effect of group size and reproductive status on faecal glucocorticoid metabolite (FGM) concentrations and individual vigilance during different stages of the reproduction cycle (i.e. non-breeding, lambing and rutting) in free-ranging adult female Przewalski’s gazelles. Group size did not influence FGMs significantly, but mean vigilance duration increased with group size. The gazelles’ FGMs and vigilance peaked in lambing season. FGMs showed no difference between rutting season and non-reproductive season, but vigilance was lowest in the rutting season. FGMs correlated with vigilance frequency and vigilance duration. Antipredator responses of female Przewalski’s gazelles appear to change with reproductive status but not with group size in free-ranging females. Management measures should be taken in the lambing season to minimize stress on mother gazelles.

scholarly journals Habitat fragmentation shapes natal dispersal and sociality in an Afrotropical cooperative breeder

2020 ◽  
Vol 287 (1941) ◽  
pp. 20202428
Author(s):  
Laurence Cousseau ◽  
Martijn Hammers ◽  
Dries Van de Loock ◽  
Beate Apfelbeck ◽  
Mwangi Githiru ◽  
...  
Keyword(s):  
Habitat Fragmentation ◽  
Large Scale ◽  
Cloud Forest ◽  
Anthropogenic Activity ◽  
Habitat Isolation ◽  
Breeding Bird ◽  
Fragmented Forest ◽  
Continuous Forest ◽  
Trade Offs ◽  
Cooperatively Breeding

It remains poorly understood how effects of anthropogenic activity, such as large-scale habitat fragmentation, impact sociality in animals. In cooperatively breeding species, groups are mostly formed through delayed offspring dispersal, and habitat fragmentation can affect this process in two opposite directions. Increased habitat isolation may increase dispersal costs, promoting delayed dispersal. Alternatively, reduced patch size and quality may decrease benefits of philopatry, promoting dispersal. Here, we test both predictions in a cooperatively breeding bird (placid greenbul, Phyllastrephus placidus ) from an Afrotropical cloud forest archipelago. Males born in fragmented forest dispersed about 1 year earlier than those born in continuous forest. Contrary to females, males also started to reproduce earlier and mostly settled within their natal patch. Females only rarely delayed their dispersal for more than 1 year, both in fragmented and continuous forests. Our results suggest that early male dispersal and reproduction is jointly driven by a decrease in the value of the natal territory and an increase in local breeding opportunities in fragmented forest. While plasticity in dispersal strategies of cooperative breeders in response to anthropogenic change is believed to optimize reproduction-survival trade-offs, to what extent it shapes the ability of species to respond to rapid environmental change remains to be studied.

scholarly journals The fitness consequences of kin-biased dispersal in a cooperatively breeding bird

2015 ◽  
Vol 11 (7) ◽  
pp. 20150336 ◽  
Author(s):  
Lea Pollack ◽  
Dustin R. Rubenstein
Keyword(s):  
Social Rank ◽  
Group Living ◽  
Breeding Bird ◽  
Direct Benefits ◽  
Fitness Consequences ◽  
Cooperatively Breeding ◽  
Potential Benefits ◽  
Indirect Fitness ◽  
Living Species

Cooperative alliances among kin may not only lead to indirect fitness benefits for group-living species, but can also provide direct benefits through access to mates or higher social rank. However, the immigrant sex in most species loses any potential benefits of living with kin unless immigrants disperse together or recruit relatives into the group in subsequent years. To look for evidence of small subgroups of related immigrants within social groups (kin substructure), we used microsatellites to assess relatedness between immigrant females of the cooperatively breeding superb starling, Lamprotornis superbus. We determined how timing of immigration led to kin subgroup formation and if being part of one influenced female fitness. Although mean relatedness in groups was higher for males than females, 26% of immigrant females were part of a kin subgroup with a sister. These immigrant sibships formed through kin recruitment across years more often than through coalitions immigrating together in the same year. Furthermore, females were more likely to breed when part of a kin subgroup than when alone, suggesting that female siblings form alliances that may positively influence their fitness. Ultimately, kin substructure should be considered when determining the role of relatedness in the evolution of animal societies.

scholarly journals Hot droughts compromise interannual survival across all group sizes in a cooperatively breeding bird

2020 ◽  
Author(s):  
Amanda R. Bourne ◽  
Susan J. Cunningham ◽  
Claire N. Spottiswoode ◽  
Amanda R. Ridley
Keyword(s):  
Climate Change ◽  
Group Size ◽  
Climatic Conditions ◽  
Breeding Bird ◽  
Body Mass Change ◽  
Species Vulnerability ◽  
Animal Populations ◽  
Cooperatively Breeding ◽  
Dry Conditions ◽  
The Impact

AbstractIncreasingly harsh and unpredictable climate regimes are affecting animal populations around the world as climate change advances. One relatively unexplored aspect of species vulnerability to climate change is whether and to what extent responses to environmental stressors might be mitigated by variation in group size in social species. We used a 15-year dataset for a cooperatively-breeding bird, the southern pied babbler Turdoides bicolor, to determine the impact of temperature, rainfall, and group size on body mass change and interannual survival in both juveniles and adults. Hot and dry conditions were associated with reduced juvenile growth, mass loss in adults, and compromised survival between years in both juveniles (−86%) and adults (−60%). Individuals across all group sizes experienced similar effects of climatic conditions. Larger group sizes may not buffer individual group members against the impacts of hot and dry conditions, which are expected to increase in frequency and severity in future.

scholarly journals Unique allometry of group size and collective brain mass in humans and primates relative to other mammals

2019 ◽  
Author(s):  
Marcus J. Hamilton ◽  
Robert S. Walker
Keyword(s):  
Social Networks ◽  
Body Size ◽  
Group Size ◽  
Brain Size ◽  
Social Groups ◽  
Group Living ◽  
Null Model ◽  
Mammalian Brain ◽  
Brain Mass ◽  
Trade Offs

AbstractGroup living is common in mammals, particularly in primates and humans. Across species, groups are social networks where co-residing members exchange information and balance trade-offs between competition and cooperation for space, resources, and reproductive opportunities. From a macroecological perspective, species-specific group sizes are ultimately constrained by body size, population density, and the environmental supply rate of home ranges. Here, we derive an allometric null model for group size in mammals based on individual energy demands and ecological constraints. Using Bayesian phylogenetic mixed models we show that primates exhibit unique allometries relative to other mammals. Moreover, as large-bodied primates, human hunter-gatherers have among the largest social groups of any mammal. We then explore the consequences of this unique social allometry by considering how mammalian brain size scales up in social groups that differ in size across mammals. We show similarly unique allometries in what we term the collective brain mass of social groups in primates relative to all other mammals. These results show that for a given body size primates have both larger brains and larger social networks than other mammals. Consequently, proportionally larger primate brains interact in proportionally larger social networks with important consequences for group cognition. We suggest that the size, scale, and complexity of human social networks in the 21st century have deep evolutionary roots in primate ecology and mammalian brain allometry.

Acorn woodpeckers vocally discriminate current and former group members from nongroup members

2020 ◽  
Vol 31 (5) ◽  
pp. 1120-1128 ◽  
Author(s):  
Michael A Pardo ◽  
Casey E Hayes ◽  
Eric L Walters ◽  
Walter D Koenig
Keyword(s):  
Social Relationships ◽  
Group Living ◽  
Current Group ◽  
Breeding Bird ◽  
Cooperatively Breeding ◽  
Melanerpes Formicivorus ◽  
Group Members ◽  
Valuable Relationships ◽  
Acorn Woodpeckers

Abstract In species with long-term social relationships, the ability to recognize individuals after extended separation and the ability to discriminate between former social affiliates that have died and those that have left the group but may return are likely to be beneficial. Few studies, however, have investigated whether animals can make these discriminations. We presented acorn woodpeckers (Melanerpes formicivorus), a group-living, cooperatively breeding bird, with playbacks of current group members, former group members still living nearby, former group members that had died or left the study area, and familiar nongroup members. Subjects responded more quickly to the calls of nongroup members than to the calls of current group members or former group members still living in the study area but did not discriminate between nongroup members and former group members that had died or disappeared. This suggests that acorn woodpeckers can vocally recognize both current group members and former group members that have dispersed to nearby groups and that they either forget former group members that no longer live in the vicinity or classify them differently from former group members that still live nearby. This study suggests an important role for vocal recognition in maintaining valuable relationships with social affiliates postdispersal.

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