scholarly journals Mother knows best: maternal egg-clutch size predicts larval group size in pine sawflies (genus Neodiprion)

2019 ◽  
Author(s):  
John W. Terbot ◽  
Catherine R. Linnen
Keyword(s):  
Clutch Size ◽  
Group Size ◽  
Oviposition Behavior ◽  
Phylogenetic Signal ◽  
Strong Predictor ◽  
Group Living ◽  
Theoretical Work ◽  
Pine Sawfly ◽  
Antagonistic Coevolution ◽  
Larval Group

AbstractEvolutionary conflicts are pervasive in nature and have the potential to drive antagonistic coevolution of conflict-related traits. However, when such conflicts are weak or idiosyncratic, phenotypic signatures of coevolutionary arms races may be absent. Here, we ask whether variation in group-living traits among pine-sawfly species in the genus Neodiprion is consistent with a history of parent-offspring conflict. To address this question, we compile data on adult female clutch size, larval aggregation behavior, and larval group size for a monophyletic group of 19 eastern North American Neodiprion species from field observations, laboratory assays, and published descriptions. We then evaluate the extent to which each trait exhibits phylogenetic signal and, based on these results, examine correlations between group-size traits both with and without phylogenetic correction. Although female oviposition behavior and larval grouping behavior varies among species and variation in these traits is decoupled from phylogeny, we find no evidence of antagonistic coevolution between these traits. Furthermore, while larvae are physically capable of dispersal, female clutch size is a strong predictor of larval colony size, indicating that larvae do not substantially alter initial group size after hatching. Thus, although theoretical work demonstrates the potential for parent-offspring conflict over group size in animals that lack parental care, our data suggest that this type of conflict is not likely to be a long-term driver of phenotypic evolution.

Subjective Fear Dilutes as Group Size Increases

2020 ◽  
Author(s):  
dean mobbs ◽  
Ellen Tedeschi ◽  
Anastasia Buyalskaya ◽  
Brian Silston
Keyword(s):  
Group Size ◽  
Real World ◽  
Survival Benefit ◽  
Group Living ◽  
External Factors ◽  
Threat Perception ◽  
Perception Of Threat ◽  
Threat Level ◽  
Internal States ◽  
Risk Dilution

According to Hamilton’s Selfish Herd Theory, a crucial survival benefit of group living is that it provides a ‘risk dilution’ function against predation. Despite a large literature on group living benefits in animals, few studies have been conducted on how group size alters subjective fear or threat perception in humans, and on what factors drive preferences for being in groups when facing threats. We conducted seven experiments (N=3,838) to test (A) if the presence of others decreases perception of threat under a variety of conditions. In studies 1 to 3, we experimentally manipulated group size in hypothetical and real-world situations, to show that fear responses decreased as group size increased. In studies 4 to 7 we again used a combination of hypothetical, virtual and real-world decisions to test (B) how internal states (e.g. anxiety) and external factors (e.g. threat level, availability of help) affected participants’ preference for groups. Participants consistently chose larger groups when threat and anxiety were high. Overall, our findings show that group size provides a salient signal of protection and safety.

scholarly journals Reproductive suppression in female cooperatively breeding cichlids

2008 ◽  
Vol 4 (6) ◽  
pp. 606-609 ◽  
Author(s):  
Dik Heg
Keyword(s):  
Clutch Size ◽  
Group Living ◽  
Egg Laying ◽  
Alloparental Care ◽  
Large Female ◽  
Egg Mass ◽  
Small Female ◽  
Reproductive Suppression ◽  
Cooperatively Breeding ◽  
Female Subordinate

Suppression by dominants of female subordinate reproduction has been found in many vertebrate social groups, but has rarely been shown experimentally. Here experimental evidence is provided for reproductive suppression in the group-living Lake Tanganyika cichlid Neolamprologus pulcher . Within groups of three unrelated females, suppression was due to medium- and small-sized females laying less frequently compared with large females, and compared with medium females in control pairs. Clutch size and average egg mass of all females depended on body size, but not on rank. In a second step, a large female was removed from the group and a very small female was added to keep the group size constant. The medium females immediately seized the dominant breeding position in the group and started to reproduce as frequently as control pairs, whereas clutch size and egg mass did not change. These results show that female subordinate cichlids are reproductively capable, but apparently suppressed with respect to egg laying. Nevertheless, some reproduction is tolerated, possibly to ensure continued alloparental care by subordinate females.

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 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.

scholarly journals Catch the wave: prairie dogs assess neighbours’ awareness using contagious displays

2014 ◽  
Vol 281 (1777) ◽  
pp. 20132153 ◽  
Author(s):  
James F. Hare ◽  
Kevin L. Campbell ◽  
Robert W. Senkiw
Keyword(s):  
Theory Of Mind ◽  
Real Time ◽  
Group Size ◽  
Social Information ◽  
Group Living ◽  
Cynomys Ludovicianus ◽  
Prairie Dogs ◽  
Social Awareness ◽  
Prairie Dog ◽  
Active Probing

The jump–yip display of black-tailed prairie dogs ( Cynomys ludovicianus ) is contagious, spreading through a prairie dog town as ‘the wave’ through a stadium. Because contagious communication in primates serves to assess conspecific social awareness, we investigated whether instigators of jump–yip bouts adjusted their behaviour relative to the response of conspecifics recruited to display bouts. Increased responsiveness of neighbouring town members resulted in bout initiators devoting a significantly greater proportion of time to active foraging. Contagious jump–yips thus function to assess neighbours’ alertness, soliciting social information to assess effective conspecific group size in real time and reveal active probing of conspecific awareness consistent with theory of mind in these group-living rodents.

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.

ROW-TYPE OVIPOSITION IN NEODIPRION SAWFLIES AS EXEMPLIFIED BY THE EUROPEAN PINE SAWFLY, N. SERTIFER (GEOFF.)

1959 ◽  
Vol 37 (3) ◽  
pp. 267-281 ◽  
Author(s):  
A. W. Ghent
Keyword(s):  
Oviposition Behavior ◽  
The Other ◽  
Leg Length ◽  
Forward Movement ◽  
Pine Sawfly ◽  
Leg Movement ◽  
European Pine Sawfly ◽  
Antennal Movement ◽  
Leg Movements

Many Neodiprion sawflies lay their eggs in a row in small pockets cut into the edges of the mature needles of various pines. These rows of eggs are remarkable for the regularity of the spacing between successive egg pockets. The regularity of egg spacing by N. sertifer is shown to arise from a stereotyped pattern of leg movements during the shift between the sites of successive egg pockets. Spacing is effected by two sets of leg movements, in each of which the three pairs of legs move forward in order from back to front. While the effective forward movement of all legs is the same, the total forward movement of the metathoracic legs is greater than that of the other legs by an amount equal to the length of an egg pocket. The metathoracic legs retrace their steps by this length as the initial incision for each new egg pocket is cut, evidently providing the force by which this incision is made. The grip-points of the legs are on the needle edge opposite to that receiving eggs, so that the wider the needle, the greater the proportion of leg length required to reach across it, and the smaller the proportion of leg movement reflected in the spacing between eggs. In this way egg spacing varies inversely with needle width. Observations on copulation, antennal movement, and related oviposition behavior are included.

scholarly journals The Infertility Trap: The Fertility Costs of Group-Living in Mammalian Social Evolution

2021 ◽  
Vol 9 ◽  
Author(s):  
Robin I. M. Dunbar ◽  
Susanne Shultz
Keyword(s):  
Group Size ◽  
Social Evolution ◽  
Low Cost ◽  
Social Groups ◽  
Group Living ◽  
The Other ◽  
Risk Averse ◽  
Limit Group ◽  
Grouping Patterns ◽  
Environmental Demands

Mammal social groups vary considerably in size from single individuals to very large herds. In some taxa, these groups are extremely stable, with at least some individuals being members of the same group throughout their lives; in other taxa, groups are unstable, with membership changing by the day. We argue that this variability in grouping patterns reflects a tradeoff between group size as a solution to environmental demands and the costs created by stress-induced infertility (creating an infertility trap). These costs are so steep that, all else equal, they will limit group size in mammals to ∼15 individuals. A species will only be able to live in larger groups if it evolves strategies that mitigate these costs. We suggest that mammals have opted for one of two solutions. One option (fission-fusion herding) is low cost but high risk; the other (bonded social groups) is risk-averse, but costly in terms of cognitive requirements.

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 The role of familiarity in signaller–receiver interactions

2018 ◽  
Vol 15 (149) ◽  
pp. 20180568
Author(s):  
Wei Ji Ma ◽  
James P. Higham
Keyword(s):  
Animal Communication ◽  
Individual Recognition ◽  
Full Range ◽  
Group Living ◽  
Theoretical Work ◽  
Bayesian Decision ◽  
Theoretical Evidence ◽  
Behavioural Biology ◽  
Decision Making Model

In animal communication, individuals of species exhibiting individual recognition of conspecifics with whom they have repeated interactions, receive signals not only from unfamiliar conspecifics, but also from individuals with whom they have prior experience. Empirical evidence suggests that familiarity with a specific signaller aids receivers in interpreting that signaller's signals, but there has been little theoretical work on this effect. Here, we develop a Bayesian decision-making model and apply it to the well-studied systems of primate ovulation signals. We compare the siring probability of learner males versus non-learner males, based on variation in their assessment of the best time to mate and mate-guard females. We compare males of different dominance ranks, and vary the number of females, and their cycle synchrony. We find strong fitness advantages for learners, which manifest very quickly. Receivers do not have to see the full range of a signaller's signals in order to start gaining familiarity benefits. Reproductive asynchrony and increasing the number of females both enhance learning advantages. We provide theoretical evidence for a strong advantage to specific learning of a signaller's range of signals in signalling systems. Our results have broad implications, not only for understanding communication, but in elucidating additional fitness benefits to group-living, the evolution of individual recognition, and other characteristics of animal behavioural biology.

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