The Influence of Group Size and Habitat on Reproductive Success in the Superb Fairy-wren Malurus cyaneus

1992 ◽  
Vol 92 (4) ◽  
pp. 238-243 ◽  
Author(s):  
Raymond C. Nias ◽  
Hugh A. Ford
Keyword(s):  
Reproductive Success ◽  
Group Size ◽  
Malurus Cyaneus

scholarly journals Fitness of breeders in social Damaraland mole-rats is independent of group size

2021 ◽  
Author(s):  
Jack Thorley ◽  
Hanna Bensch ◽  
Kyle Finn ◽  
Tim Clutton-Brock ◽  
Markus Zöttl
Keyword(s):  
Reproductive Success ◽  
Group Size ◽  
Survival Rates ◽  
Group Living ◽  
Adult Survival ◽  
High Survival ◽  
Successful Reproduction ◽  
Related Group ◽  
Group Members ◽  
Using Data

Damaraland mole-rats (Fukomys damarensis) are usually viewed as an obligatorily group living eusocial species in which successful reproduction is dependent on reproductive altruism of closely related group members. However, the reproductive ecology of social mole-rats in their natural environment remains poorly understood and it is unclear to what extent successful reproduction is dependent on assistance from other group members. Using data from a 7-year field study of marked individuals, we show that, after dispersal from their natal group, individuals typically settled alone in new burrow systems where they enjoyed high survival rates, and often remained in good body condition for several years before finding a mate. Unlike most other eusocial or singular cooperative breeders, we found that Damaraland mole-rats reproduced successfully in pairs without helpers and experimentally formed pairs had the same reproductive success as larger established groups. Overall there was only a weak increase in reproductive success with increasing group size and no effect of group size on adult survival rates across the population. Juveniles in large groups grew faster early in life but their growth rates declined subsequently so that they eventually plateaued at a lower maximum body mass than juveniles from small groups. Taken together, our data suggest that the fitness benefits of group living to breeders are small and we suggest that extended philopatry in Damaraland mole-rats has evolved because of the high costs and constraints of dispersal rather than because of strong indirect benefits accrued through cooperative behaviour.

scholarly journals Factors influencing male affiliation and coalitions in a species with male dispersal and intense male–male competition, Colobus vellerosus

Behaviour ◽  
2014 ◽  
Vol 151 (7) ◽  
pp. 1045-1066 ◽  
Author(s):  
Julie A. Teichroeb ◽  
Eva C. Wikberg ◽  
Nelson Ting ◽  
Pascale Sicotte
Keyword(s):  
Reproductive Success ◽  
Group Size ◽  
Species Interactions ◽  
Male Competition ◽  
Adult Males ◽  
Cooperative Relationships ◽  
Colobus Vellerosus ◽  
Male Dispersal ◽  
Factors Influencing ◽  
High Level

Male Colobus vellerosus compete intensely for access to females, which sometimes leads to mortal wounding. Yet, males often form cooperative relationships to overtake prime-aged males and immigrate into bisexual groups. We investigated the factors that predicted the presence of coalitions and affiliative relationships among males in this species. Interactions among males in 292 dyads from six groups were examined from 2004 to 2010 at Boabeng-Fiema, Ghana. Affiliation rates among males were higher and aggression rates lower when one or both males in the dyad were subadult, compared to adult male dyads. Affiliation rates tended to be higher among males that were kin but no other aspect of male relationships predicted affiliation. Coalitions among males were rarely observed and primarily occurred in the context of joint defense against extra-group males (93.5% of events). Adult males were more likely to provide coalitionary support than subadults and coalitions occurred significantly more often when both males were high ranking, since these males probably benefited most in terms of reproductive success from excluding extra-group males. Rank-changing and leveling coalitions among low-ranking males appear to be quite rare or absent in C. vellerosus. The costs of these types of coalitions may be too high or male group size too small on average for these types of coalitions to have been selected for. The overall low rates of affiliation and coalitions among male C. vellerosus are likely influenced by male-biased dispersal and the high level of male–male competition.

scholarly journals Limited and fitness-neutral effects of resource heterogeneity on sociality in a communally rearing rodent

2016 ◽  
Vol 97 (4) ◽  
pp. 1125-1135 ◽  
Author(s):  
Luis A. Ebensperger ◽  
Felipe Pérez de Arce ◽  
Sebastian Abades ◽  
Loren D. Hayes
Keyword(s):  
Reproductive Success ◽  
Spatial Heterogeneity ◽  
Group Size ◽  
Territory Size ◽  
Resource Heterogeneity ◽  
Access To Resources ◽  
Resource Dispersion ◽  
Resource Dispersion Hypothesis ◽  
Per Capita ◽  
Los Grupos

Abstract Contrasting scenarios have been proposed to explain how resource heterogeneity influences group living or sociality. First, sociality may result from individuals in larger groups attaining net fitness benefits by monopolizing access to resources (“resource-defense” hypothesis). Second, sociality may be the fitness-neutral outcome of multiple individuals using a territory with sufficient resources to sustain a group of conspecifics (“resource-dispersion” hypothesis). While previous studies have tended to support the resource-dispersion hypothesis, these analyses have typically examined only 1 or a few predictions, making it difficult to distinguish between the 2 alternatives. We conducted a 4-year field study of Octodon degus to quantify the effects of spatial heterogeneity in food and refuge distributions on group size and 2 components of reproductive success (per capita number of offspring, offspring survival) in this plural breeding and communal rearing rodent. We found only a small effect of heterogeneity of food resources on group size; the effect food resource distribution on group territory size varied across years. Group size did not vary with spatial variation in group territory size and quality. Importantly, there was no covariation between group size and quality of an individual’s territory (i.e., a measure of individual access to resources), or between this measure of territory quality and reproductive success, implying no resource-based benefits to social degus. Overall, our results were more consistent with fitness-neutral relationships among spatial heterogeneity of resources, sociality, and territory size. The resource-dispersion hypothesis, however, did not provide a complete explanation for degu socioecology. Se han propuesto distintas hipótesis para explicar cómo la heterogeneidad de los recursos afecta la vida en grupos, o sociabilidad. Esta puede surgir en situaciones donde individuos en grupos grandes se benefician al monopolizar el acceso a recursos (hipótesis de defensa de recursos). Por otra parte, la vida en grupos también puede ser el resultado neutro (en términos de adecuación) de individuos que comparten un territorio con recursos suficientes (hipótesis de dispersión de recursos). Aunque algunos estudios previos han validado la hipótesis de dispersión de recursos, estos solo han evaluado un número limitado de las predicciones de esta hipótesis, lo que ha dificultado distinguir entre esta y otras hipótesis alternativas. Durante un estudio de 4 años cuantificamos los efectos de la heterogeneidad espacial de alimento y distribución de refugios sobre el tamaño de grupo y dos componentes del éxito reproductivo (número per cápita de crías, supervivencia de las crías) en Octodon degus. Se registraron efectos relativamente pequeños de la heterogeneidad espacial del alimento sobre el tamaño de grupo, y variables entre años sobre el tamaño del territorio de cada grupo. El tamaño de grupo no fue afectado por la variación espacial en el tamaño y calidad del territorio de los grupos. No se registró co-variación entre el tamaño de los grupos y la calidad del territorio de cada individuo (una medida individual del acceso a recursos), o entre la calidad del territorio individual y el éxito reproductivo, lo que sugiere ausencia de beneficios derivados del uso social de recursos en degus. En general, los resultados fueron más consistentes con un escenario de efectos neutros de la heterogeneidad espacial de recursos sobre la sociabilidad. Sin embargo, la hipótesis de dispersión de recursos no explicó el conjunto de efectos (o su ausencia) asociados a la socioecología del degu.

scholarly journals High temperatures drive offspring mortality in a cooperatively breeding bird

2020 ◽  
Author(s):  
Amanda R. Bourne ◽  
Susan J. Cunningham ◽  
Claire N. Spottiswoode ◽  
Amanda R. Ridley
Keyword(s):  
Climate Change ◽  
Reproductive Success ◽  
Group Size ◽  
High Temperatures ◽  
Environmental Conditions ◽  
Cooperative Breeding ◽  
Evolution Of Cooperation ◽  
Daily Maximum ◽  
Unexpected Result ◽  
Development Stages

AbstractAn improved understanding of life history responses to current environmental variability is required to predict species-specific responses to anthopogenic climate change. Previous research has suggested that cooperation in social groups may buffer individuals against some of the negative effects of unpredictable climates. We use a 15-year dataset on a cooperative-breeding arid-zone bird, the southern pied babbler Turdoides bicolor, to test i) whether environmental conditions and group size correlate with survival of young during three development stages (egg, nestling, fledgling), and ii) whether group size mitigates the impacts of adverse environmental conditions on reproductive success. Exposure to high mean daily maximum temperatures (mean Tmax) during early development was associated with reduced survival probabilities of young in all three development stages. No young survived when mean Tmax > 38°C across all group sizes. Low reproductive success at high temperatures has broad implications for recruitment and population persistence in avian communities given the rapid pace of advancing climate change. That impacts of high temperatures were not moderated by group size, a somewhat unexpected result given prevailing theories around the influence of environmental uncertainty on the evolution of cooperation, suggests that cooperative breeding strategies are unlikely to be advantageous in the face of rapid anthropogenic climate change.

Reproductive success increases with group size in cooperative carrion crows, Corvus corone corone

2008 ◽  
Vol 75 (2) ◽  
pp. 403-416 ◽  
Author(s):  
Daniela Canestrari ◽  
José M. Marcos ◽  
Vittorio Baglione
Keyword(s):  
Reproductive Success ◽  
Group Size ◽  
Corvus Corone
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