Group Fission Research Articles

裂变到重组：云南大学院系调整与西南边疆高教格局塑造

In the early 1950s, Yunnan University undertook departmental adjustments and expansions in alignment with national strategic directives. This involved relocating disciplines related to national defense, industrial development, and the national economy to regions such as Sichuan, Chongqing, and Guizhou, allowing for the independent development of disciplines that capitalized on Yunnan’s strengths in minerals, medicine, agriculture, and forestry. These efforts aimed to optimize the structure and capabilities of universities in the southwestern region and Yunnan Province while facilitating the rapid growth of specialized talent cultivation. This was achieved through comprehensive transfers, partial involvement in group fission, and the reorganization for independent development. As Yunnan University contributed to the emergence of a new higher education landscape in the southwestern frontier and Yunnan Province, it encountered phases of single-track development and a decline in humanities education during specific historical periods.

A novel methodological approach for group classification during fission of a semi-free-ranging group of Japanese macaques (Macaca fuscata).

The self-initiated split of a social group, known as fission, is a challenge faced by many group-living animals. The study of group fission and the social restructuring process in real time provides insights into the mechanism of this biologically important process. Previous studies on fission in Japanese macaques (Macaca fuscata) assigned individuals to newly reorganized groups mainly using behavioral observations and group attendance records based on periods before or after fission itself. Here, we present a novel framework for group classification during the process of fission that uses quantifiable behavioral variables and statistical analyses. The framework was tested on a group fission process at Affenberg Landskron (Austria), a park that housed around 160 semi-free-ranging Japanese macaques. The behavioral data were collected for 26 days during fission. We analyzed three behavioral developments recurrent in fissions in Japanese macaques, that is, independence of behavior, participation in group movements, and separation of nomadic ranges. These analyses were combined to assign individuals to different groups. Our study resulted in one main group (N = 33), one subgroup (N = 36) and 56 individuals whose group membership was still undefined. The demographic characteristics of these newly formed groups were comparable with those of fissioned groups in wild populations. Furthermore, we found that these newly forming groups showed early social dynamics of fission five months before group level movements, that is: grouping based on spatial proximity and spatial withdrawal of the subgroup to the periphery. These results underline the validity of our novel framework to study social dynamics in Japanese macaques during the process of fission. It represents an important addition to existing methods, and we recommend testing its scope in other primate societies.

Process of Japanese macaque group fission at Arashiyama and the influences of maternal kin relations and social relations between adult males and females on it.

In 1986, the Japanese macaques of Arashiyama B group fissioned into Arashiyama E and F groups through the following process. In December 1985, the death of the beta male triggered aggressive interactions among the adult males of B group, leading to a decline in the ranks of two mid-ranked males. Several females started to gather around these two males, formed a stable subgroup (here called the female cluster), and spatially distanced themselves from other group members (main group). Some of these females had mating relations with these two males in previous mating seasons. After the end of the 1985-86 mating season, agonistic interactions occurred frequently between the female cluster and main group. Eventually, two independent groups were established. The females within the 4th degrees of matrilineal consanguinity tended to belong to the same group, but no such tendency occurred in those dyads separated by the 5th or more degrees. After the completion of group fission, mating occurred only a few times between E and F group members. In 1986, when the group fission was in progress, the birth rate of both branch groups declined, and infant mortality increased in E group. After 1987, the birth rate recovered in both branch groups although infant mortality remained high.

An intentional cohesion call in male chimpanzees of Budongo Forest

Many social animals travel in cohesive groups but some species, including chimpanzees, form flexible fission–fusion systems where individuals have some control over group cohesion and proximity to others. Here, we explored how male chimpanzees of the Sonso community of Budongo Forest, Uganda, use communication signals during resting, a context where the likelihood of group fission is high due to forthcoming travel. We focused on a context-specific vocalisation, the ‘rest hoo’, to investigate its function and determine whether it is produced intentionally. We found that this call was typically given towards the end of typical silent resting bouts, i.e., the period when individuals need to decide whether to continue travelling after a brief stop-over or to start a prolonged resting bout. Subjects rested longer after producing ‘rest hoos’ and their resting time increased with the number of calls produced. They also rested longer if their calls were answered. Furthermore, focal subjects’ resting time was prolonged after hearing others’ ‘rest hoos’. Subjects called more when with top proximity partners and in small parties and rested longer if a top proximity partner called. We also found an interaction effect between rank and grooming activity, with high-ranking males with a high grooming index calling less frequently than other males, suggesting that vocal communication may serve as a cohesion strategy alternative to tactile-based bonding. We discuss these different patterns and conclude that chimpanzee ‘rest hoos’ meet key criteria for intentional signalling. We suggest that ‘rest hoos’ are produced to prolong resting bouts with desired partners, which may function to increase social cohesion.

Better baboon break-ups: collective decision theory of complex social network fissions.

Many social groups are made up of complex social networks in which each individual associates with a distinct subset of its groupmates. If social groups become larger over time, competition often leads to a permanent group fission. During such fissions, complex social networks present a collective decision problem and a multidimensional optimization problem: it is advantageous for each individual to remain with their closest allies after a fission, but impossible for every individual to do so. Here, we develop computational algorithms designed to simulate group fissions in a network-theoretic framework. We focus on three fission algorithms (democracy, community and despotism) that fall on a spectrum from a democratic to a dictatorial collective decision. We parameterize our social networks with data from wild baboons (Papio cynocephalus) and compare our simulated fissions with actual baboon fission events. We find that the democracy and community algorithms (egalitarian decisions where each individual influences the outcome) better maintain social networks during simulated fissions than despotic decisions (driven primarily by a single individual). We also find that egalitarian decisions are better at predicting the observed individual-level outcomes of observed fissions, although the observed fissions often disturbed their social networks more than the simulated egalitarian fissions.

Aggregation, status competition and levelling mechanisms in prehistoric Chulmun, Korea

This article discusses the aggregation and dispersion of the Chulmun hunter-gatherers (c. 8000–1500 bce) in prehistoric Korea. The following observations are made from settlement datasets. First, large numbers of houses do not necessarily imply aggregation, as they can be palimpsests of dwelling structures from different phases. Second, aggregation settlements were segmented and contained multiple discrete subunits. Individual residential clusters typically had fewer than 60 inhabitants. Third, there are some indications of social hierarchy in nucleated settlements such as Unseo-dong. Fourth, despite some evidence of emergent elites and social differentiation, social complexity did not intensify over the long run. Levelling mechanisms (e.g. group fission) were in operation and they suppressed the institutionalization of social hierarchy.

On the Use of Chromium Coating for Inner-Side Fuel Cladding Protection: Thickness Identification Based on Fission Fragments Implantation and Damage Profile

Inner-side coatings have been proposed as a complementary solution within the accident tolerant fuel (ATF) framework, to provide enhanced protection for the nuclear fuel cladding. Unlike external surface, the degradation of irradiated internal cladding surface has not been studied extensively. Fission fragments produced during the fission of nuclear fuel is one of the key players in this degradation. This study aimed to estimate the minimum thickness of the thin chromium film, required to protect the inner side of the nuclear fuel cladding. The approach used is based on a set of calculations, of Ion ranges and damage profiles, for a group fission fragments, using the TRIM code. The calculation results were verified by comparison with the experimental data associated with the phenomena of the inner cladding degradation of thermo-releasing elements. The recommended minimum thickness for such a film was found to be 9 microns. Calculations also showed that chromium metal has a greater stopping power compared to the zirconium-based alloy E110, which indicates an increased ability of chromium to withstand exposure to energetic fission fragments during reactor operation.

Collective decision-making appears more egalitarian in populations where group fission costs are higher.

Collective decision-making is predicted to be more egalitarian in conditions where the costs of group fission are higher. Here, we ask whether Trinidadian guppies (Poecilia reticulata) living in high or low predation environments, and thereby facing differential group fission costs, make collective decisions in line with this prediction. Using a classic decision-making scenario, we found that fish from high predation environments switched their positions within groups more frequently than fish from low predation environments. Because the relative positions individuals adopt in moving groups can influence their contribution towards group decisions, increased positional switching appears to support the prediction of more evenly distributed decision-making in populations where group fission costs are higher. In an agent-based model, we further identified that more frequent, asynchronous updating of individuals' positions could explain increased positional switching, as was observed in fish from high predation environments. Our results are consistent with theoretical predictions about the structure of collective decision-making and the adaptability of social decision-rules in the face of different environmental contexts.

Successional loss of two key food tree species best explains decline in group size of Panamanian howler monkeys (Alouatta palliata)

AbstractNegative impacts of discrete, short‐term disturbances to wildlife populations are well‐documented. The consequences of more gradual environmental change are less apparent and harder to study because they play out over longer periods and are often indirect in their action. Yet, they can drive the decline of wildlife populations even in seemingly pristine and currently well‐protected habitats. One such environmental change is a successional shift in a community's species composition as it regenerates from disturbance caused by past human land use. Early and middle successional tree species often provide key foods to folivores and frugivores, but the abundance of these resources drops as the forest matures, with adverse repercussions for these consumers. Our 44‐year record (1974–2018) of howler monkey (Alouatta palliata) group sizes and demographic composition from Barro Colorado Island, Panama, a protected reserve, documents an example of this phenomenon. After 70 years of relative stability, the mean size of howler monkey groups exhibited a marked decline, beginning in 2003. This downward trajectory in group size has continued through the most recent census in 2018. The composition of howler groups also changed significantly during the study period, with the patterns of decline differing among age/sex classes. There is no evidence that these changes were caused by increased rates of emigration, group fission, predation, parasitism, or disease. Rather, they are best explained by an island‐wide, succession‐driven decline in the densities of two species of free‐standing fig trees, Ficus yoponensis and F. insipida, which together were providing ~36% of BCI howlers’ annual diet.Abstract in Spanish is available with online material.

Divergence in gut microbial communities mirrors a social group fission event in a black-and-white colobus monkey (Colobus vellerosus).

Host behavior and social factors have increasingly been implicated in structuring the composition of gut microbial communities. In social animals, distinct microbial communities characterize different social groups across a variety of taxa, although little longitudinal research has been conducted that demonstrates how this divergence occurs. Our study addresses this question by characterizing the gut microbial composition of an African Old World monkey, the black-and-white colobus (Colobus vellerosus), before and after a social group fission event. Gut microbial taxonomic composition of these monkeys was profiled using the V-4 hypervariable region of the bacterial 16S ribosomal RNA gene, and pairwise-relatedness values were calculated for all individuals using 17 short tandem repeat loci and partial pedigree information. The two social groups in this study were found to harbor distinct microbial signatures after the fission event from which they emerged, while these communities were not divergent in the same individuals before this event. Three genera were found to differ in abundance between the two new social groups: Parabacteroides, Coprococcus, and Porphyromonadaceae. Additionally, although this fission happened partially along lines of relatedness, relatedness did not structure the differences that we found. Taken together, this study suggests that distinct gut microbial profiles can emerge in social groups in <1 year and recommends further work into more finely mapping the timescales, causes, and potentially adaptive effects of this recurring trend toward distinct group microbial signatures.

Both familiarity and kinship influence odour discrimination by females in a highly social African ground squirrel

Kin recognition can be important in species where inbreeding avoidance or nepotism (favouritism towards kin) rely on identifying kin, particularly in species with alloparental care. The mechanisms that facilitate kin discrimination, where recognition is determined through cues that correlate with relatedness, usually include either prior association (familiarity) or phenotype matching or both. Odour is an important cue used in a number of mammalian species to discern kin, particularly the ground-dwelling squirrels. Cape ground squirrels, Xerus inauris, are a cooperative-breeding species, living in tight-knit family groups. However, group fission, promiscuity and the large home ranges of breeding males result in a high variance in relatedness both within and among social groups, making them a good species to investigate kin discrimination. We examined whether females are capable of discriminating between the odours of familiar versus unfamiliar females that varied in their relatedness to the focal female using odour experiments. Overall, the average duration of sniffing of the odours of familiar and unfamiliar females did not differ. Similarly, females did not adjust their sniff duration relative to the degree of relatedness of familiar females. However, females appeared to discriminate by the degree of relatedness of unfamiliar (stranger) females, spending longer sniffing odours from females that were not related to them. Thus, females were capable of discriminating the degree of relatedness from odour but they did not do so within their family group. We conclude that Cape ground squirrels are able to discriminate kin. However, whether females in this facultative cooperative breeder use the degree of relatedness in direct social interactions and nepotistic behaviours remains to be investigated.

Self‐Organized Fission‐Fusion Control Algorithm for Flocking Systems Based on Intermittent Selective Interaction

In nature, gregarious animals, insects, or bacteria usually exhibit paradoxical behaviors in the form of group fission and fusion, which exerts an important influence on group’s pattern formation, information transfer, and epidemiology. However, the fission‐fusion dynamics have received little attention compared to other flocking behavior. In this paper, an intermittent selective interaction based control algorithm for the self‐organized fission‐fusion behavior of flocking system is proposed, which bridges the gap between the two conflicting behaviors in a unified fashion. Specifically, a hybrid velocity coordination strategy that includes both the egalitarian and selective interactions is proposed, where the egalitarian interaction is to maintain the flock’s order and achieve the fusion behavior while the selective interaction strategy is for the response to external stimulus information and generates the fission behavior. Numerical simulations demonstrate that the proposed control algorithm can realize the self‐organized fission‐fusion behavior of flocking system under a unified framework. The influences of the main control parameters on the performance of the fission‐fusion behavior are also discussed. In particular, the trade‐off parameter α balances the exploration (fission) and exploitation (fusion) behaviors of flocking system and significantly enhances its movement flexibility and environmental adaptivity.

Dusky dolphin group dynamics and association patterns in Península Valdés, Argentina

AbstractWe inspected dusky dolphin (Lagenorhynchus obscurus) group dynamics in Golfo Nuevo and found differences in social organization between cold and warm seasons. Surveys were conducted onboard a research vessel, from which we collected behavioral observations and group fission‐fusion data from 2001 to 2008; we also collected photo‐identification data from 2004 to 2012. To analyze association patterns, we calculated half‐weight association index (HWI) and social differentiation (S). We conducted a Monte Carlo permutation test to determine whether observed association patterns were significantly different from random association using a compiled version of SOCPROG 2.7. Group fission and fusion dynamics depended on group behavior, the main activity after the groups' fusion was feeding, and they never fission before socializing. The social structure of dusky dolphins included long‐term preferred companions in the cold season; during the warm season, there were no preferred companions. This seasonal difference in social structure could be related to an accompanying shift in foraging behaviors that appears to be driven by changes in prey availability. If so, then a loosening of bonds among individuals during the warm season, when prey is more available, would reflect these social structure changes.

Landscape knowledge is an important driver of the fission dynamics of an alpine ungulate

Collective movement decisions are often based on personal and conspecific knowledge. In fission–fusion animal societies, individuals rarely have the same level of information about their environment, with knowledge being a reflection of past individual and collective decisions. Knowledge of the environment is particularly essential in heterogeneous landscapes, where resources may vary in space and time. Indeed, landscape heterogeneity, a product of the quantity and configuration of resources as well as predators and competitors, is the basis of both individual and collective movement decisions. We assessed individual movement decisions of an alpine ungulate as a function of landscape knowledge and landscape heterogeneity. We hypothesized that individuals would base their decisions on previous information in areas they know well, especially in highly heterogeneous landscapes. These individual decisions would have consequences for the collective movement decisions of groups. To test this hypothesis, we used GPS collars to monitor the movements of ∼45% of the individuals (N = 28) of a small population of woodland caribou, Rangifer tarandus caribou, between 2013 and 2016. We assessed the fission probability of caribou dyads (N = 3681, from 172 dyad combinations) in relation to landscape knowledge, landscape heterogeneity and social bonds between dyad members. The probability of group fission was influenced by the interaction between the variables describing landscape knowledge of dyadic members and social bonds. The probability of group fission and the influence of habitat or social bonds on fission probability increased with landscape knowledge. In familiar landscapes, individuals were more likely to stay with conspecifics if they shared a strong social bond or if they were in preferential habitat. Such fine adjustments in movement and social decisions demonstrated the importance of the information held by conspecifics when occupying unfamiliar areas. By staying with conspecifics, individuals could gain access to high-quality resources without the energetic cost of locating such resources.

Social structure as a strategy to mitigate the costs of group living: a comparison of gelada and guereza monkeys

In mammals, and especially primates, group size and social complexity are typically correlated. However, we have no general explanation why this is so. I suggest that the answer may lie in one of the costs of group living: mammalian reproductive endocrinology is extremely sensitive to stress, and forms one of the hidden costs of living in groups. Fertility declines with group size widely across the social mammals, including primates, and will ultimately place a constraint on group size. However, some species seem to have been able to mitigate this cost by forming bonded relationships that reduce the impact of experienced aggression, even if rates of aggression remain high. The downside is that they reduce network connectivity and hence risk fragmenting the group by providing fracture lines for group fission. To explore this, I compare network indices and fertility patterns across the same range of group sizes for two species of Old World monkeys, Colobus guereza and Theropithecus gelada: the former relatively unsocial, the latter intensely social with frequent use of grooming-based alliances. Compared to those of the guereza, gelada social networks lose density more slowly, maintain connectedness more effectively and are less likely to fragment as they increase in size. Although fertility declines with group size in both species, in gelada the impact of this effect is deferred to larger group sizes. The differences in fertility and network structure both predict the very different maximum group sizes typical of these two species, as well as the typical sizes at which their groups undergo fission. This finding may explain aspects of wider mammalian sociality.

The Dynamics of Group Fission

We present and test a simple model of a process by which a cohesive collection of individuals splits apart. We propose that, faced with a possible splintering issue, the natural cohesion mechanism that would typically unite the group and allow for a consistent set of decisions on an issue instead serves to drive the group apart, creating factions. Notably, this “divisive effect” is proportionally larger than the original divisiveness of the issue itself; we propose that this amplification effect is the mechanism by which group fission may be understood in various settings. We find the functional forms of this effect in the case of a well-mixed population, and explore several important extensions to the model, including structured populations on networks. Finally, we discuss the model in the context of published data on political partisanship.

Modeling the lowest-cost splitting of a herd of cows by optimizing a cost function.

Animals live in groups to defend against predation and to obtain food. However, for some animals-especially ones that spend long periods of time feeding-there are costs if a group chooses to move on before their nutritional needs are satisfied. If the conflict between feeding and keeping up with a group becomes too large, it may be advantageous for some groups of animals to split into subgroups with similar nutritional needs. We model the costs and benefits of splitting in a herd of cows using a cost function that quantifies individual variation in hunger, desire to lie down, and predation risk. We model the costs associated with hunger and lying desire as the standard deviations of individuals within a group, and we model predation risk as an inverse exponential function of the group size. We minimize the cost function over all plausible groups that can arise from a given herd and study the dynamics of group splitting. We examine how the cow dynamics and cost function depend on the parameters in the model and consider two biologically-motivated examples: (1) group switching and group fission in a herd of relatively homogeneous cows, and (2) a herd with an equal number of adult males (larger animals) and adult females (smaller animals).

Social implications of fission in wild Formosan macaques at Mount Longevity, Taiwan

Group fission in non-human primates has long been proposed to result from interactions between ecological and social factors. Several studies have documented possible causes for group fission, but its proximate causes and ultimate adaptive values are not yet fully understood. We have examined the existing hypotheses on fission from long-term demographic data of Formosan macaques inhabiting the lowland rainforest at Mt Longevity, Taiwan. Five cases of fission occurred in four social groups. We have recorded two types of fission: one involving the separation of a high-ranking adult male and multiple adult females, the other initiated by adult females from main groups. Five adult females immigrated and emigrated a few times between the main and branch groups (oscillation) in three fission events. Data presented in this study are consistent with the prediction that low-ranking females split from main groups when their fitness costs increase due to ecological pressure or population growth. However, their reproductive success may decrease after fission due to a high rate of intra-group competition. Nevertheless, it is beneficial for males to be involved in fission since this increases reproductive benefits by decreasing the sex ratio in small newly formed groups.

Increased Exploration Capacity Promotes Group Fission in Gregarious Foraging Herbivores.

Many gregarious species display rapid fission-fusion dynamics with individuals frequently leaving their groups to reunite or to form new ones soon after. The adaptive value of such ephemeral associations might reflect a frequent tilt in the balance between the costs and benefits of maintaining group cohesion. The lack of information on the short-term advantages of group fission, however, hampers our understanding of group dynamics. We investigated the effect of group fission on area-restricted search, a search tactic that is commonly used when food distribution is spatially autocorrelated. Specifically, we determine if roe deer (Capreolus capreolus) improve key aspects of their extensive search mode immediately after fission. We found that groups indeed moved faster and farther over time immediately after than before fission. This gain was highest for the smallest group that resulted from fission, which was more likely to include the fission’s initiator. Sex of group members further mediated the immediate gain in search capacity, as post-fission groups moved away at farthest rate when they were only comprised of males. Our study suggests that social conflicts during the extensive search mode can promote group fission and, as such, can be a key determinant of group fission-fusion dynamics that are commonly observed in gregarious herbivores.

The archaeological landscape of Late Prehispanic mixed foraging and cultivation economy (Sierras of Córdoba, Argentina)

A short review of current data regarding the landscape use in the Sierras of Córdoba Late Prehispanic Period (ca. 1500–300BP) is presented in this article. Resulting expectation about residential mobility and subsistence are analyzed in light of new evidence and interpretative framework. The lack of substantial middens, few evidences of year-round residence and the low investment in farming fields support the inadequacies of the assumption that the agriculture led to the sudden dependence of crops and to the sedentary way of life in pit-house villages. Other archaeological indicators as the intensity of landscape use, the taxonomic richness of food residues, the abundance of projectile point-types and isotopic evidence reinforce these arguments. However, the evidence suggests that the Late Prehispanic peoples showed flexible subsistence and mobility patterns as one of their defining traits, where nuclear families moved around the landscape to take advantage of both agricultural and wild resources as available. Thus, farming was a fluctuating component in a mixed foraging and cultivation economy where wild animals and plants were intensively exploited through seasonal co-residential group fission–fusion mechanisms that follow the pre-existing Middle Holocene forager lifeways. Nevertheless, many variables can affect this equation, including regional population densities, social boundaries or annual variation in foraging opportunities and a mosaic of strategies combination is also predicted.