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Cooperative Breeding (cooperative + breeding)
Selected AbstractsCooperative Breeding and Group Structure in the Lake Tanganyika Cichlid Neolamprologus savoryiETHOLOGY, Issue 11 2005Dik Heg As yet, cooperative breeding has been described only for some fish species. However, evidence is accumulating that it is widespread among Lake Tanganyika cichlids. We studied the cooperative breeding system of the substrate breeding cichlid Neolamprologus savoryi. Breeding groups typically consisted of a large breeding male with one to four breeding females and three to 33 helpers (mean group size: 14.3 members). Group size was significantly related to breeding male and female body sizes, and larger males had more breeding females and larger sized male helpers. The size of the largest female in the group was positively related to the number and sizes of secondary breeding females and female helpers. In case of multiple breeding females, these females usually divided the group's territory into sub-territories, each with its own helpers (subgroups). Interspersed between groups, independent fish were detected defending an individual shelter (4.4% of all fish). In 9% of the groups no breeding female was present. All group members participated in territory defence and maintenance, and showed submissive behaviours to larger group members. As expected, the level of between-subgroup conflicts was high compared with the level of within-subgroup conflicts. We compare these results with data available from other cooperatively breeding fishes. [source] Reproductive success and helper effects in the cooperatively breeding grey-crowned babblerJOURNAL OF ZOOLOGY, Issue 3 2007C. J. Blackmore Abstract Cooperative breeding, where some individuals help to raise offspring that are not their own, is a relatively rare social system in birds. We studied the breeding biology of a declining cooperative breeder, the grey-crowned babbler Pomatostomus temporalis, with the aim of isolating the social factors that affect its reproductive success. Most breeding pairs were assisted by philopatric offspring, although pairs could breed successfully without helpers. Females laid up to four clutches (usually three eggs per clutch) per season. Male (but not female) helpers increased the number of young fledged from individual nests and the likelihood of re-nesting, resulting in higher seasonal fledgling production. Helper effects on brood size and fledgling production were greater in the second year of the study, which was also characterized by higher nest failure. This suggests that helpers enhance reproduction more in poor conditions. Our study demonstrates the interacting effects of social and ecological factors on reproductive success, and that retention of offspring is not always beneficial for the breeders in cooperative species. [source] Cooperative Breeding and Group Structure in the Lake Tanganyika Cichlid Neolamprologus savoryiETHOLOGY, Issue 11 2005Dik Heg As yet, cooperative breeding has been described only for some fish species. However, evidence is accumulating that it is widespread among Lake Tanganyika cichlids. We studied the cooperative breeding system of the substrate breeding cichlid Neolamprologus savoryi. Breeding groups typically consisted of a large breeding male with one to four breeding females and three to 33 helpers (mean group size: 14.3 members). Group size was significantly related to breeding male and female body sizes, and larger males had more breeding females and larger sized male helpers. The size of the largest female in the group was positively related to the number and sizes of secondary breeding females and female helpers. In case of multiple breeding females, these females usually divided the group's territory into sub-territories, each with its own helpers (subgroups). Interspersed between groups, independent fish were detected defending an individual shelter (4.4% of all fish). In 9% of the groups no breeding female was present. All group members participated in territory defence and maintenance, and showed submissive behaviours to larger group members. As expected, the level of between-subgroup conflicts was high compared with the level of within-subgroup conflicts. We compare these results with data available from other cooperatively breeding fishes. [source] How helpers help: disentangling ecological confounds from the benefits of cooperative breedingJOURNAL OF ANIMAL ECOLOGY, Issue 3 2008JONATHAN WRIGHT Evolutionary explanations for helping in cooperative breeding systems usually require a positive effect of helping on the fitness of the breeders being assisted. However, such helper effects have proven surprisingly difficult to quantify. Cockburn et al. (this issue) apply detailed statistical analyses to long-term field data on the enigmatic superb fairy-wren. They show that it is possible to disentangle the complex web of ecological and evolutionary interactions that confound so many studies. Whilst fairy-wren helpers may not increase nest productivity, they do increase future survival of breeding females. This study points the way for future statistical explorations of long-term data in other cooperative birds and mammals. [source] Group breeding dramatically increases reproductive success of yearling but not older female scrubwrens: a model for cooperatively breeding birds?JOURNAL OF ANIMAL ECOLOGY, Issue 3 2001Robert D. Magrath Summary 1,Many studies of cooperatively breeding birds have found no effect of group size on reproductive success, contrary to predictions of most adaptive hypotheses. A model is proposed for variation in group-size effects: group size has a reduced effect on success when conditions for breeding are good, such as in good environmental conditions or in groups with older breeders. This hypothesis is tested with a case study of white-browed scrubwrens Sericornis frontalis and a review of the literature. 2,The scrubwren is a cooperatively breeding passerine with male helpers. Previous analyses revealed no effect of group size on reproductive success, but those analyses were restricted to groups with older females (Magrath & Yezerinac 1997). Here 7 years' data are used to contrast the effect of group size on reproductive success for yearling and older females. 3,Yearling females breeding in groups had more than double the seasonal reproductive success than those breeding in pairs, even after controlling for territory quality. However, group size still had no effect on the reproductive success of older females. Yearling females tended to survive better in groups, but older females tended to survive better in pairs, emphasizing this pattern. 4,Yearlings breeding in pairs were more likely to be found on poor-quality territories than those breeding in groups, exaggerating the already-strong effect of group size on yearling success. Older females were not affected significantly by territory quality. 5,Group size, territory quality and female age affected different components of seasonal reproductive success. Group size increased the success of individual nesting attempts, while both territory quality and female age affected the length of the breeding season, and thus the number of breeding attempts. 6,A sample of the literature on cooperative breeders shows that group size has a larger effect on reproductive success in poorer conditions, caused either by younger, inexperienced breeders or poorer environmental conditions. Scrubwrens therefore illustrate a widespread pattern, which provides an explanation for much of the variation in group-size effects among and within species. Clearly single estimates of group-size effects for species can be inadequate to test ideas about the evolution of cooperative breeding. [source] | ||||||||||