scholarly journals Individual and collective encoding of risk in animal groups

2019 ◽  
Vol 116 (41) ◽  
pp. 20556-20561 ◽  
Author(s):  
Matthew M. G. Sosna ◽  
Colin R. Twomey ◽  
Joseph Bak-Coleman ◽  
Winnie Poel ◽  
Bryan C. Daniels ◽  
...  
Keyword(s):  
Perceived Risk ◽  
Structural Connectivity ◽  
Group Living ◽  
Natural World ◽  
Social Cues ◽  
Animal Groups ◽  
Fish Schools ◽  
Individual Fitness ◽  
Increased Sensitivity ◽  
Context Dependent

The need to make fast decisions under risky and uncertain conditions is a widespread problem in the natural world. While there has been extensive work on how individual organisms dynamically modify their behavior to respond appropriately to changing environmental conditions (and how this is encoded in the brain), we know remarkably little about the corresponding aspects of collective information processing in animal groups. For example, many groups appear to show increased “sensitivity” in the presence of perceived threat, as evidenced by the increased frequency and magnitude of repeated cascading waves of behavioral change often observed in fish schools and bird flocks under such circumstances. How such context-dependent changes in collective sensitivity are mediated, however, is unknown. Here we address this question using schooling fish as a model system, focusing on 2 nonexclusive hypotheses: 1) that changes in collective responsiveness result from changes in how individuals respond to social cues (i.e., changes to the properties of the “nodes” in the social network), and 2) that they result from changes made to the structural connectivity of the network itself (i.e., the computation is encoded in the “edges” of the network). We find that despite the fact that perceived risk increases the probability for individuals to initiate an alarm, the context-dependent change in collective sensitivity predominantly results not from changes in how individuals respond to social cues, but instead from how individuals modify the spatial structure, and correspondingly the topology of the network of interactions, within the group. Risk is thus encoded as a collective property, emphasizing that in group-living species individual fitness can depend strongly on coupling between scales of behavioral organization.

scholarly journals Family feud: permanent group splitting in a highly philopatric mammal, the killer whale (Orcinus orca)

2021 ◽  
Vol 75 (3) ◽  
Author(s):  
Eva H. Stredulinsky ◽  
Chris T. Darimont ◽  
Lance Barrett-Lennard ◽  
Graeme M. Ellis ◽  
John K. B. Ford
Keyword(s):  
Killer Whale ◽  
Group Structure ◽  
Group Living ◽  
Orcinus Orca ◽  
Learning Approaches ◽  
Killer Whales ◽  
Internal Factors ◽  
Individual Fitness ◽  
Leadership Experience

Abstract For animals that tend to remain with their natal group rather than individually disperse, group sizes may become too large to benefit individual fitness. In such cases, group splitting (or fission) allows philopatric animals to form more optimal group sizes without sacrificing all familiar social relationships. Although permanent group splitting is observed in many mammals, it occurs relatively infrequently. Here, we use combined generalized modeling and machine learning approaches to provide a comprehensive examination of group splitting in a population of killer whales (Orcinus orca) that occurred over three decades. Fission occurred both along and across maternal lines, where animals dispersed in parallel with their closest maternal kin. Group splitting was more common: (1) in larger natal groups, (2) when the common maternal ancestor was no longer alive, and (3) among groups with greater substructuring. The death of a matriarch did not appear to immediately trigger splitting. Our data suggest intragroup competition for food, leadership experience and kinship are important factors that influence group splitting in this population. Our approach provides a foundation for future studies to examine the dynamics and consequences of matrilineal fission in killer whales and other taxa. Significance statement Group living among mammals often involves long-term social affiliation, strengthened by kinship and cooperative behaviours. As such, changes in group membership may have significant consequences for individuals’ fitness and a population’s genetic structure. Permanent group splitting is a complex and relatively rare phenomenon that has yet to be examined in detail in killer whales. In the context of a growing population, in which offspring of both sexes remain with their mothers for life, we provide the first in-depth examination of group splitting in killer whales, where splitting occurs both along and across maternal lines. We also undertake the first comprehensive assessment of how killer whale intragroup cohesion is influenced by both external and internal factors, including group structure, population and group demography, and resource abundance.

Brain structural connectivity and context-dependent extinction memory

Hippocampus ◽  
2017 ◽  
Vol 27 (8) ◽  
pp. 883-889 ◽  
Author(s):  
Andrea Hermann ◽  
Rudolf Stark ◽  
Carlo R. Blecker ◽  
Mohammed R. Milad ◽  
Christian J. Merz
Keyword(s):  
Structural Connectivity ◽  
Extinction Memory ◽  
Context Dependent

scholarly journals Does a Simple Cope's Rule Mechanism Overlook Predators?

2007 ◽  
Vol 2007 ◽  
pp. 1-2
Author(s):  
Vincenzo Penteriani ◽  
Robert Kenward
Keyword(s):  
Large Body ◽  
General Increase ◽  
Predator Species ◽  
Animal Groups ◽  
Individual Fitness ◽  
Large Size ◽  
High Fitness ◽  
Body Sizes ◽  
Cope’S Rule

The Cope’s rule predicts a tendency for species to evolve towards an increase in size. Recently, it has been suggested that such a tendency is due to the fact that large body sizes provide a general increase in individual fitness. Here we highlight evidence that predator species do not always fit the large-size = high-fitness mechanism for Cope’s rule. Given the specific requirements of predators and the complexity of prey-predator relationships, any analysis that does not take into account all animal groups may overlook a significant portion of evolutive trends. Generalisations may not be possible regardless of taxa.

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 Effect of relative social rank within a social hierarchy on neural activation in response to familiar or unfamiliar social signals

2020 ◽  
Author(s):  
Won Lee ◽  
Hollie N. Dowd ◽  
Cyrus Nikain ◽  
Madeleine F. Dwortz ◽  
Eilene D. Yang ◽  
...  
Keyword(s):  
Social Status ◽  
Social Rank ◽  
Group Living ◽  
Brain Regions ◽  
Social Cues ◽  
Neural Activation ◽  
Social Signals ◽  
Subordinate Male ◽  
Male Urine ◽  
The Social

AbstractCompetent social functioning of group-living species relies on the ability of individuals to detect and utilize conspecific social cues to guide behavior. Previous studies have identified numerous brain regions involved in processing these external cues, collectively referred to as the Social Decision-Making Network. However, how the brain encodes social information with respect to an individual’s social status has not been thoroughly examined. In mice, cues about an individual’s identity, including social status, are conveyed through urinary proteins. In this study, we assessed the neural cFos immunoreactivity in dominant and subordinate male mice exposed to familiar and unfamiliar dominant and subordinate male urine. The posteroventral medial amygdala was the only brain region that responded exclusively to dominant compared to subordinate male urine. In all other brain regions, including the VMH, PMv, and vlPAG, activity is modulated by a combination of odor familiarity and the social status of both the urine donor and the subject receiving the cue. We show that dominant subjects exhibit robust differential activity across different types of cues compared to subordinate subjects, suggesting that individuals perceive social cues differently depending on social experience. These data inform further investigation of neurobiological mechanisms underlying social-status related brain differences and behavior.

scholarly journals Role of sociality in the response of killer whales to an additive mortality event

2019 ◽  
pp. 201817174 ◽  
Author(s):  
Marine Busson ◽  
Matthieu Authier ◽  
Christophe Barbraud ◽  
Paul Tixier ◽  
Ryan R. Reisinger ◽  
...  
Keyword(s):  
Social Structure ◽  
Social Groups ◽  
Group Living ◽  
Foraging Success ◽  
Killer Whales ◽  
Negative Effects ◽  
Mortality Event ◽  
Individual Fitness ◽  
Fishing Vessels ◽  
Additive Mortality

In highly social top predators, group living is an ecological strategy that enhances individual fitness, primarily through increased foraging success. Additive mortality events across multiple social groups in populations may affect the social structure, and therefore the fitness, of surviving individuals. This hypothesis was examined in a killer whale (Orcinus orca) population that experienced a 7-y period of severe additive mortality due to lethal interactions with illegal fishing vessels. Using both social and demographic analyses conducted on a unique long-term dataset encompassing periods before, during, and after this event, results indicated a decrease in both the number and the mean strength of associations of surviving individuals during the additive mortality period. A positive significant correlation between association strength and apparent survival suggested that the fitness of surviving individuals was impacted by the additive mortality event. After this event, individuals responded to the loss of relatives in their social groups by associating with a greater number of other social groups, likely to maintain a functional group size that maximized their foraging success. However, these associations were loose; individuals did not reassociate in highly stable social groups, and their survival remained low years after the mortality event. These findings demonstrate how the disruption of social structure in killer whales may lead to prolonged negative effects of demographic stress beyond an additive mortality event. More importantly, this study shows that sociality has a key role in the resilience of populations to human-induced mortality; this has major implications for the conservation of highly social and long-lived species.

scholarly journals Kin selection in Columbian ground squirrels ( Urocitellus columbianus ): littermate kin provide individual fitness benefits

2009 ◽  
Vol 277 (1684) ◽  
pp. 989-994 ◽  
Author(s):  
Vincent A. Viblanc ◽  
Coline M. Arnaud ◽  
F. Stephen Dobson ◽  
Jan O. Murie
Keyword(s):  
Kin Selection ◽  
Large Body ◽  
Group Living ◽  
Ground Squirrels ◽  
Evolution Of Cooperation ◽  
Major Life ◽  
Individual Fitness ◽  
Evolution Of Sociality ◽  
Fitness Benefits ◽  
Columbian Ground Squirrels

Since W. D. Hamilton's seminal work on the evolution of sociality, a large body of research has accumulated on how kin selection might explain the evolution of cooperation in many group-living species. Our study examined the evolutionary basis of philopatry and cooperation; specifically, whether individuals benefit from the presence of close kin. We applied an individual fitness approach to a 16-year study of Columbian ground squirrels ( Urocitellus columbianus ) to investigate potential causal paths by which the presence of kin might act on individual fitness. Our results indicate that individual fitness benefits resulted from associations of philopatric female kin, and support the hypothesis that increased tolerance of proximity of kin is a proximate mechanism for these benefits. The major life-history influence of kin on individual fitness was through improved reproductive success, and this benefit may have been owing to philopatric settlement of kin that were recognized through familiarization in the natal burrow. Thus, we demonstrated an evolutionary basis necessary for ongoing kin-selected cooperation in Columbian ground squirrels, though the mechanism of familiarity may determine which kin individuals benefit from cooperative behaviours.

scholarly journals Evidence for varying social strategies across the day in chacma baboons

2014 ◽  
Vol 10 (7) ◽  
pp. 20140249 ◽  
Author(s):  
Claudia Sick ◽  
Alecia J. Carter ◽  
Harry H. Marshall ◽  
Leslie A. Knapp ◽  
Torben Dabelsteen ◽  
...  
Keyword(s):  
Social Relationships ◽  
Group Living ◽  
Social Strategies ◽  
Market Theory ◽  
Papio Ursinus ◽  
Individual Fitness ◽  
Biological Market Theory ◽  
Chacma Baboons ◽  
Short Time ◽  
Biological Market

Strong social bonds can make an important contribution to individual fitness, but we still have only a limited understanding of the temporal period relevant to the adjustment of social relationships. While there is growing recognition of the importance of strong bonds that persist for years, social relationships can also vary over weeks and months, suggesting that social strategies may be optimized over shorter timescales. Using biological market theory as a framework, we explore whether temporal variation in the benefits of social relationships might be sufficient to generate daily adjustments of social strategies in wild baboons. Data on grooming, one measure of social relationships, were collected from 60 chacma baboons ( Papio ursinus ) across two troops over a six month period. Our analyses suggest that social strategies can show diurnal variation, with subordinates preferentially grooming more dominant individuals earlier in the day compared with later in the day. These findings indicate that group-living animals may optimize certain elements of their social strategies over relatively short time periods.

scholarly journals Oil palm cultivation critically affects sociality in a threatened Malaysian primate

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Anna Holzner ◽  
Krishna N. Balasubramaniam ◽  
Brigitte M. Weiß ◽  
Nadine Ruppert ◽  
Anja Widdig
Keyword(s):  
Social Interactions ◽  
Oil Palm ◽  
Group Living ◽  
Anthropogenic Landscapes ◽  
Habitat Alterations ◽  
Individual Fitness ◽  
Social Network Structure ◽  
Animal Populations ◽  
Survival Studies ◽  
Species Adaptability

AbstractHuman-induced habitat alterations globally threaten animal populations, often evoking complex behavioural responses in wildlife. This may be particularly dramatic when negatively affecting social behaviour, which fundamentally determines individual fitness and offspring survival in group-living animals. Here, we provide first evidence for significant behavioural modifications in sociality of southern pig-tailed macaques visiting Malaysian oil palm plantations in search of food despite elevated predation risk. Specifically, we found critical reductions of key positive social interactions but higher rates of aggression in the plantation interior compared to the plantation edge (i.e. plantation areas bordering the forest) and the forest. At the plantation edge, affiliation even increased compared to the forest, while central positions in the macaques' social network structure shifted from high-ranking adult females and immatures to low-ranking individuals. Further, plantations also affected mother–infant relationships, with macaque mothers being more protective in the open plantation environment. We suggest that although primates can temporarily persist in human-altered habitats, their ability to permanently adapt requires the presence of close-by forest and comes with a trade-off in sociality, potentially hampering individual fitness and infant survival. Studies like ours remain critical for understanding species’ adaptability to anthropogenic landscapes, which may ultimately contribute to facilitating their coexistence with humans and preserving biodiversity.

Do songbirds attend to song categories when selecting breeding habitat? A case study with a wood warbler

Behaviour ◽  
2017 ◽  
Vol 154 (11) ◽  
pp. 1123-1144 ◽  
Author(s):  
Janice K. Kelly ◽  
Michael P. Ward
Keyword(s):  
Habitat Selection ◽  
Social Cues ◽  
Breeding Habitat ◽  
Yellow Warbler ◽  
Individual Fitness ◽  
First Category ◽  
Different Types ◽  
Yellow Warblers ◽  
Second Category

Breeding habitat selection strongly affects reproduction and individual fitness. Among birds, using social cues from conspecifics to select habitat is widespread, but how different types of conspecific social cues influence breeding habitat selection remains less understood. We conducted a playback experiment evaluating if the yellow warbler (Setophaga petechia), a species with two song categories linked to pairing status, uses categories differently when selecting breeding habitat. We hypothesized that yellow warblers use second-category singing mode, which is mostly sung by paired males, over first-category singing mode for habitat selection, as successfully paired males should indicate higher-quality habitat. We broadcast yellow warbler first-category singing mode, second-category singing mode, and silent controls at sites in Illinois. Yellow warblers were more abundant at sites treated with second-category singing mode compared other sites. Our results demonstrate that yellow warblers use social cues informing successful pairing over other types of social cues to select breeding habitat.

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