scholarly journals The Goldilocks Effect: Female geladas in mid-sized groups have higher fitness

2018 ◽  
Author(s):  
Elizabeth Tinsley Johnson ◽  
Noah Snyder-Mackler ◽  
Amy Lu ◽  
Thore J. Bergman ◽  
Jacinta C. Beehner
Keyword(s):  
Group Size ◽  
Size Variation ◽  
Group Living ◽  
Mortality Rates ◽  
Female Mortality ◽  
Individual Fitness ◽  
The Cost ◽  
Large Groups ◽  
The Relationship ◽  
Insight Into

AbstractThe cost-to-benefit ratio of group-living is thought to vary with group size: individuals in “optimal” groups should have higher fitness than individuals in groups that are too large or small. However, the relationship between group size and individual fitness has been difficult to establish, a gap we address here in the gelada. We demonstrate group size effects on the production of surviving offspring and on female mortality rates, which are largely explained by group-size variation in infanticide risk and foraging competition. We also identify a mechanism by which females may alter group size: in large groups, females groomed with less than half of their group, increasing the likelihood of fissions. Our findings provide insight into how and why group size shapes fitness in long-lived species.

scholarly journals The Goldilocks effect: female geladas in mid-sized groups have higher fitness

2021 ◽  
Vol 288 (1952) ◽  
pp. 20210820
Author(s):  
Elizabeth Tinsley Johnson ◽  
Jacob A. Feder ◽  
Thore J. Bergman ◽  
Amy Lu ◽  
Noah Snyder-Mackler ◽  
...  
Keyword(s):  
Group Size ◽  
Reproductive Performance ◽  
Demographic Data ◽  
Group Living ◽  
Cost Benefit ◽  
Individual Fitness ◽  
Cost Benefit Ratio ◽  
Reproductive Rates ◽  
The Cost ◽  
The Relationship

The cost–benefit ratio of group living is thought to vary with group size: individuals in ‘optimally sized’ groups should have higher fitness than individuals in groups that are either too large or too small. However, the relationship between group size and individual fitness has been difficult to establish for long-lived species where the number of groups studied is typically quite low. Here, we present evidence for optimal group size that maximizes female fitness in a population of geladas ( Theropithecus gelada ). Drawing on 14 years of demographic data, we found that females in small groups experienced the highest death rates, while females in mid-sized groups exhibited the highest reproductive performance. This group size effect on female reproductive performance was largely explained by variation in infant mortality (and, in particular, by infanticide from immigrant males) but not by variation in reproductive rates. Taken together, females in mid-sized groups are projected to attain optimal fitness due to conspecific infanticide and, potentially, predation. Our findings provide insight into how and why group size shapes fitness in long-lived species.

scholarly journals Fisheries-induced selection against schooling behaviour in marine fishes

2020 ◽  
Vol 287 (1935) ◽  
pp. 20201752
Author(s):  
Ana Sofia Guerra ◽  
Albert B. Kao ◽  
Douglas J. McCauley ◽  
Andrew M. Berdahl
Keyword(s):  
Group Size ◽  
Group Living ◽  
Natural Environments ◽  
Fishing Pressure ◽  
Target Groups ◽  
Individual Level ◽  
Common Strategy ◽  
Schooling Behaviour ◽  
Large Groups ◽  
The Relationship

Group living is a common strategy used by fishes to improve their fitness. While sociality is associated with many benefits in natural environments, including predator avoidance, this behaviour may be maladaptive in the Anthropocene. Humans have become the dominant predator in many marine systems, with modern fishing gear developed to specifically target groups of schooling species. Therefore, ironically, behavioural strategies which evolved to avoid non-human predators may now actually make certain fish more vulnerable to predation by humans. Here, we use an individual-based model to explore the evolution of fish schooling behaviour in a range of environments, including natural and human-dominated predation conditions. In our model, individual fish may leave or join groups depending on their group-size preferences, but their experienced group size is also a function of the preferences of others in the population. Our model predicts that industrial fishing selects against individual-level behaviours that produce large groups. However, the relationship between fishing pressure and sociality is nonlinear, and we observe discontinuities and hysteresis as fishing pressure is increased or decreased. Our results suggest that industrial fishing practices could be altering fishes’ tendency to school, and that social behaviour should be added to the list of traits subject to fishery-induced evolution.

The relationship of social vocalizations to surface behavior and aggression in the Hawaiian humpback whale (Megaptera novaeangliae)

1986 ◽  
Vol 64 (10) ◽  
pp. 2075-2080 ◽  
Author(s):  
Gregory K. Silber
Keyword(s):  
Surface Activity ◽  
Group Size ◽  
Social Dominance ◽  
Humpback Whale ◽  
Megaptera Novaeangliae ◽  
Adult Males ◽  
Surface Behavior ◽  
Relationship Of ◽  
Large Groups ◽  
The Relationship

Humpback whale (Megaptera novaeangliae) social vocalizations (nonsong sounds) were clearly related to whale group size and surface activity. Social sounds occurred almost exclusively in groups containing three or more whales and were rarely heard near single whales, pairs, or cow–calf groups. Large groups (3 to 20 individuals) vocalized at an overall mean rate of 43.1 ± 55.52 sounds per whale/h. Group size changed frequently and a dramatic increase in vocalization rate resulted when a new whale entered a group. Large groups engaged in flurries of surface activity, such as breaching, flipper- and tail-slapping, and underwater bubbling. Aggressive encounters resulted from male–male interaction. Social sounds probably acted to demonstrate aggression or agitation as adult males competed for temporary social dominance within the group and for proximity to the female. Likewise, visual displays may have been used as threats in close quarters and were apparently produced in conjunction with sounds to convey levels of aggression. Although other studies suggested that surface activity increased with group size, I found a negative correlation between activity and group size, both in the group as a whole and per individual. In contrast, social vocalizations per group increased with group size while the vocalization rate per individual did not vary significantly with increasing group size.

scholarly journals The relationships between feeding-group size and feeding rate vary from positive to negative with characteristics of food items in wild Japanese macaques (Macaca fuscata)

Behaviour ◽  
2013 ◽  
Vol 150 (2) ◽  
pp. 175-197 ◽  
Author(s):  
N. Kazahari ◽  
Y. Tsuji ◽  
N. Agetsuma
Keyword(s):  
Group Size ◽  
Feeding Rate ◽  
Group Living ◽  
Japanese Macaques ◽  
Food Density ◽  
Food Items ◽  
Feeding Group ◽  
Negative Impacts ◽  
The Relationship ◽  
Negative Relationships

To understand the costs and benefits of group-living, it is important to clarify the impacts of other individuals on foraging success. Previous studies on group-living primates have focused on the relationship between feeding-group size and feeding rate in food patches, and have exhibited inconsistent results, showing positive, neutral, or negative relationships. The relationship realized will depend on the balance of positive and negative impacts of co-feeding on feeding rate. The intensity of negative impacts (i.e., feeding competition) may vary with some characteristics of food items such as (1) patch size, (2) within-patch food density, (3) within-patch distribution pattern of food, (4) the abundance and (5) distribution pattern of within-habitat food trees, and (6) the relative energy content among available food items. Thus, the balance of positive and negative impacts of co-feeding, and ultimately the relationship between feeding-group size and feeding rate, is expected to change with characteristics of food items. In this study of wild Japanese macaques (Macaca fuscata), the relationship between feeding-group size and feeding rate, and the above six characteristics of 12 main food items were assessed over six seasons. Positive, neutral, or negative relationships between feeding-group size and feeding rate were detected among these food items. Positive relationships were consistently associated with within-patch food density; higher food density within food patches was likely to lead to positive relationships. Thus, various relationships between feeding-group size and feeding rate should be attributed to these specific characteristics of food items, which alter the degree of feeding competition.

scholarly journals Research groups: how big should they be?

2015 ◽  
Author(s):  
Isabelle Cook ◽  
Sam Grange ◽  
Adam Eyre-Walker
Keyword(s):  
Impact Factor ◽  
Group Size ◽  
The United Kingdom ◽  
Average Group ◽  
Using Data ◽  
Number Of Publications ◽  
Number Of Citations ◽  
The Impact ◽  
Large Groups ◽  
The Relationship

We have investigated the relationship between research group size and productivity in the life sciences in the United Kingdom using data from 398 principle investigators (PIs). We show that the number of publications increases linearly with group size, but that the slope is modest relative to the intercept, and that the relationship explains little of the variance in productivity. A comparison of the slope and intercept suggests that PIs contribute on average 5-times more productivity than an average group member and using multiple regression we estimate that post-doctoral researchers are approximately 3–times more productive than PhD students. We also find that the impact factor and the number of citations are both non-linearly related to group size such that there is a maximum. However, the relationships explain little of the variance and the curvatures are shallow so the impact factor and the number of citations do not greatly depend upon group size. The intercept is large relative to curvature suggesting that the PI is largely responsible for the impact factor and the number of citations from their group. Surprisingly we find this non-linear relationship for post-docs, but for PhD students we observe a slight but significant decrease in the impact factor. The results have important implications for the funding of research. Given a set number of Pis there is no evidence of diminishing returns in terms of the number of papers published and only a very weak cost to very large groups in terms of where those papers are published and the number of citations they receive. However, the results do suggest that it might be more productive to invest in new permanent members of faculty rather than additional post-docs and PhD students.

Production, behaviour and welfare of growing pigs as influenced by drinker allocation and group size

1998 ◽  
Vol 1998 ◽  
pp. 114-114
Author(s):  
S. P. Turner ◽  
S. A. Edwards
Keyword(s):  
Group Size ◽  
Empirical Investigation ◽  
Growing Pigs ◽  
Production Performance ◽  
Light Weight ◽  
Large White ◽  
Commercial Grower ◽  
Heavy Medium ◽  
Large Groups ◽  
The Relationship

The requirement for water of growing pigs in large groups has been neglected. Current MAFF recommendations suggest one nipple drinker per 10 pigs, while farmers have often used a ratio of 1 per 20 animals. Neither approach is based on empirical investigation. The relationship between group size and the number of drinking points can not be assumed to be linear. The aim was to assess group size and the two conflicting ratios of drinkers for their effect on welfare, as measured by production performance, drinking and social behaviour.A total of 640 Large White x Landrace growing pigs (start weight 36kg) were housed in a fully slatted commercial grower house for five weeks. Four replicates were used and each animal was assigned to 1 of 4 treatments in a 2 x 2 factorial design of two group sizes (20 vs 60) and two ratios of nipple drinkers to pigs (1:10 vs 1:20). The groups of 20 comprised of pigs from 3 different pens, while 9 pens contributed to the groups of 60. The floor space per pig was maintained constant across treatments. Nine focal pigs (three each of heavy, medium and light weight) were selected from each pen.

Bearded saki socioecology: affiliative male–male interactions in large, free-ranging primate groups in Suriname

Behaviour ◽  
2014 ◽  
Vol 151 (4) ◽  
pp. 493-533 ◽  
Author(s):  
Tremaine Gregory ◽  
Marilyn A. Norconk
Keyword(s):  
Group Size ◽  
Group Living ◽  
Wet Season ◽  
Social Patterns ◽  
Continuous Forest ◽  
Chiropotes Sagulatus ◽  
Free Ranging ◽  
Bearded Sakis ◽  
First Time ◽  
Large Groups

Bearded sakis (Chiropotes spp.) are among the least known primates in the world, particularly with regard to their social organization. However, extremely large and variable group size and growing evidence for affiliative relationships among males, make them a fascinating subject for studies of male–male tolerance and the evolution of large groups. During a 13-month study of free ranging Guianan bearded sakis (Chiropotes sagulatus) in continuous forest in Suriname, we documented variation in group size seasonally and social behaviour, particularly among males. We found that group size was smaller and more variable in the long dry season than the short wet season, perhaps in response to changes in resource availability. We found clear evidence of affiliative male–male relationships, with males being more social than females (89.2% of events involved one male versus 15.6% that involved one female) and typically socializing with other males (68.7% of events involved 2 or more males). We also found no evidence of hierarchical relationships between males (complete absence of agonistic interactions), and we documented unique male-affiliative behaviours and temporary all-male subgroups for the first time. To investigate potential explanations of male tolerance, we compared bearded saki social patterns to other multi-male group living primates (Ateline and Pan spp.). We found similarities with Brachyteles that suggest high intergroup mating competition and scramble competition for mates within groups.

scholarly journals Ecogeography of group size suggests differences in drivers of sociality among cooperatively breeding fairywrens

2022 ◽  
Author(s):  
Allison E. Johnson ◽  
Joseph F. Welklin ◽  
Ian R. Hoppe ◽  
Daizaburo Shizuka
Keyword(s):  
Social Systems ◽  
Group Living ◽  
Cost Of Reproduction ◽  
Harsh Environments ◽  
Costs And Benefits ◽  
Resource Defense ◽  
Social Variation ◽  
Cooperatively Breeding ◽  
The Cost ◽  
Insight Into

Cooperatively breeding species exhibit a range of social behaviors associated with different costs and benefits to group-living, often in association with different environmental conditions. For example, species in which collective-care of offspring reduces the cost of reproduction are more common in harsh environments (true cooperative breeding), while species that collectively defend resources are present in benign environments (family-living). Here, we examine whether environment also shapes sociality within cooperatively-breeding species. We illustrate that Purple-backed Fairywrens, which primarily gain intrinsic, or collective-care benefits, have larger groups in hot, dry environments and smaller groups in cool, wet environments, whereas Superb Fairywrens which primarily gain extrinsic, or resource defense benefits, exhibit the opposite trend. We suggest differences in the costs and benefits of sociality contribute to these opposing ecogeographic patterns, demonstrating that comparisons of intraspecific patterns of social variation across species can provide insight into how ecology shapes transitions between social systems.

Production, behaviour and welfare of growing pigs as influenced by drinker allocation and group size

1998 ◽  
Vol 1998 ◽  
pp. 114-114 ◽  
Author(s):  
S. P. Turner ◽  
S. A. Edwards
Keyword(s):  
Group Size ◽  
Empirical Investigation ◽  
Growing Pigs ◽  
Production Performance ◽  
Light Weight ◽  
Large White ◽  
Commercial Grower ◽  
Heavy Medium ◽  
Large Groups ◽  
The Relationship

The requirement for water of growing pigs in large groups has been neglected. Current MAFF recommendations suggest one nipple drinker per 10 pigs, while farmers have often used a ratio of 1 per 20 animals. Neither approach is based on empirical investigation. The relationship between group size and the number of drinking points can not be assumed to be linear. The aim was to assess group size and the two conflicting ratios of drinkers for their effect on welfare, as measured by production performance, drinking and social behaviour.A total of 640 Large White x Landrace growing pigs (start weight 36kg) were housed in a fully slatted commercial grower house for five weeks. Four replicates were used and each animal was assigned to 1 of 4 treatments in a 2 x 2 factorial design of two group sizes (20 vs 60) and two ratios of nipple drinkers to pigs (1:10 vs 1:20). The groups of 20 comprised of pigs from 3 different pens, while 9 pens contributed to the groups of 60. The floor space per pig was maintained constant across treatments. Nine focal pigs (three each of heavy, medium and light weight) were selected from each pen.

scholarly journals Research groups: how big should they be?

2015 ◽  
Author(s):  
Isabelle Cook ◽  
Sam Grange ◽  
Adam Eyre-Walker
Keyword(s):  
Impact Factor ◽  
Group Size ◽  
The United Kingdom ◽  
Average Group ◽  
Using Data ◽  
Number Of Publications ◽  
Number Of Citations ◽  
The Impact ◽  
Large Groups ◽  
The Relationship

We have investigated the relationship between research group size and productivity in the life sciences in the United Kingdom using data from 398 principle investigators (PIs). We show that the number of publications increases linearly with group size, but that the slope is modest relative to the intercept, and that the relationship explains little of the variance in productivity. A comparison of the slope and intercept suggests that PIs contribute on average 5-times more productivity than an average group member and using multiple regression we estimate that post-doctoral researchers are approximately 3–times more productive than PhD students. We also find that the impact factor and the number of citations are both non-linearly related to group size such that there is a maximum. However, the relationships explain little of the variance and the curvatures are shallow so the impact factor and the number of citations do not greatly depend upon group size. The intercept is large relative to curvature suggesting that the PI is largely responsible for the impact factor and the number of citations from their group. Surprisingly we find this non-linear relationship for post-docs, but for PhD students we observe a slight but significant decrease in the impact factor. The results have important implications for the funding of research. Given a set number of Pis there is no evidence of diminishing returns in terms of the number of papers published and only a very weak cost to very large groups in terms of where those papers are published and the number of citations they receive. However, the results do suggest that it might be more productive to invest in new permanent members of faculty rather than additional post-docs and PhD students.

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