scholarly journals Breaking down population density into different components to better understand its spatial variation

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Mickaël Jacquier ◽  
Jean-Michel Vandel ◽  
François Léger ◽  
Jeanne Duhayer ◽  
Sylvia Pardonnet ◽  
...  
Keyword(s):  
Population Density ◽  
Spatial Variation ◽  
Group Size ◽  
Social Group ◽  
Local Population ◽  
Group Living ◽  
Density Variation ◽  
Genetic Identification ◽  
Population Densities ◽  
Living Species

Abstract Background Population size and densities are key parameters in both fundamental and applied ecology, as they affect population resilience to density-dependent processes, habitat changes and stochastic events. Efficient management measures or species conservation programs thus require accurate estimates of local population densities across time and space, especially for continuously distributed species. For social species living in groups, population density depends on different components, namely the number of groups and the group size, for which relative variations in space may originate from different environmental factors. Whether resulting spatial variations in density are mostly triggered by one component or the other remains poorly known. Here, we aimed at determining the magnitude of the spatial variation in population densities of a social, group-living species, i.e. the European badger Meles meles, in 13 different sites of around 50 km2 across France, to decipher whether sett density, group size or proportion of occupied sett variation is the main factor explaining density variation. Besides the intrinsic factors of density variation, we also assessed whether habitat characteristics such as habitat fragmentation, urbanisation, and resource availability, drove both the spatial variation of density components and local population densities. Results We proposed a new standardised approach combining use of multiple methods, namely distance sampling for estimating the density of occupied sett clusters, i.e. group density, and camera and hair trapping for genetic identification to determine the mean social group size. The density of adult badgers was on average 3.8 per km2 (range 1.7–7.9 per km2) and was positively correlated with the density of sett clusters. The density of adult badgers per site was less related to the social group size or to the proportion of occupied sett clusters. Landscape fragmentation also explained the spatial variation of adult badger density, with highly fragmented landscapes supporting lower adult densities. Density components were linked differently to environmental variables. Conclusions These results underline the need to break down population density estimates into several components in group-living species to better understand the pattern of temporal and spatial variation in population density, as different components may vary due to different ecological factors.

Variability in Grouping in the Eastern Grey Kangaroo, Macropus giganteus I. Group Density and Group Size

1984 ◽  
Vol 11 (3) ◽  
pp. 423 ◽  
Author(s):  
CJ Southwell
Keyword(s):  
Seasonal Variation ◽  
Population Density ◽  
Group Size ◽  
Spatial Dispersion ◽  
Population Densities ◽  
Forest Habitat ◽  
Open Forest ◽  
Grey Kangaroo ◽  
Group Density ◽  
The Relationship

The effects of season, population density and habitat on group density and group size in the eastern grey kangaroo were examined. In an open forest habitat, both group density and group size increased significantly with population density, but no seasonal variation was detected for either parameter. The relationship with population density was logarithmic for group density and exponential for group size. In a tall shrubland habitat both group density and group size increased with population density, but the range of population densities sampled was too narrow for the nature of the relationships to be determined. Group density was significantly higher, and group size significantly lower, in the tall shrubland than in the open forest. Possible reasons for this difference in spatial dispersion between habitats are discussed.

scholarly journals The effect of boldness on decision-making in barnacle geese is group-size-dependent

2010 ◽  
Vol 278 (1714) ◽  
pp. 2018-2024 ◽  
Author(s):  
Ralf H. J. M. Kurvers ◽  
Vena M. A. P. Adamczyk ◽  
Sipke E. van Wieren ◽  
Herbert H. T. Prins
Keyword(s):  
Decision Making ◽  
Group Size ◽  
Group Living ◽  
Decision Making Process ◽  
Central Question ◽  
Size Dependent ◽  
Collective Decisions ◽  
Living Species ◽  
Barnacle Geese

In group-living species, decisions made by individuals may result in collective behaviours. A central question in understanding collective behaviours is how individual variation in phenotype affects collective behaviours. However, how the personality of individuals affects collective decisions in groups remains poorly understood. Here, we investigated the role of boldness on the decision-making process in different-sized groups of barnacle geese. Naive barnacle geese, differing in boldness score, were introduced in a labyrinth in groups with either one or three informed demonstrators. The demonstrators possessed information about the route through the labyrinth. In pairs, the probability of choosing a route prior to the informed demonstrator increased with increasing boldness score: bolder individuals decided more often for themselves where to go compared with shyer individuals, whereas shyer individuals waited more often for the demonstrators to decide and followed this information. In groups of four individuals, however, there was no effect of boldness on decision-making, suggesting that individual differences were less important with increasing group size. Our experimental results show that personality is important in collective decisions in pairs of barnacle geese, and suggest that bolder individuals have a greater influence over the outcome of decisions in groups.

scholarly journals Optimal group size in a highly social mammal

2015 ◽  
Vol 112 (48) ◽  
pp. 14882-14887 ◽  
Author(s):  
A. Catherine Markham ◽  
Laurence R. Gesquiere ◽  
Susan C. Alberts ◽  
Jeanne Altmann
Keyword(s):  
Home Range ◽  
Group Size ◽  
Group Living ◽  
Space Use ◽  
Papio Cynocephalus ◽  
Group Competition ◽  
Daily Travel Distance ◽  
Living Species ◽  
Important Trait ◽  
Constraints Model

Group size is an important trait of social animals, affecting how individuals allocate time and use space, and influencing both an individual’s fitness and the collective, cooperative behaviors of the group as a whole. Here we tested predictions motivated by the ecological constraints model of group size, examining the effects of group size on ranging patterns and adult female glucocorticoid (stress hormone) concentrations in five social groups of wild baboons (Papio cynocephalus) over an 11-y period. Strikingly, we found evidence that intermediate-sized groups have energetically optimal space-use strategies; both large and small groups experience ranging disadvantages, in contrast to the commonly reported positive linear relationship between group size and home range area and daily travel distance, which depict a disadvantage only in large groups. Specifically, we observed a U-shaped relationship between group size and home range area, average daily distance traveled, evenness of space use within the home range, and glucocorticoid concentrations. We propose that a likely explanation for these U-shaped patterns is that large, socially dominant groups are constrained by within-group competition, whereas small, socially subordinate groups are constrained by between-group competition and predation pressures. Overall, our results provide testable hypotheses for evaluating group-size constraints in other group-living species, in which the costs of intra- and intergroup competition vary as a function of group size.

How Much Does Social Group Size Influence Golden Marmot Vigilance?

Behaviour ◽  
1996 ◽  
Vol 133 (15-16) ◽  
pp. 1133-1151 ◽  
Author(s):  
Daniel T. Blumstein
Keyword(s):  
Size Effect ◽  
Group Size ◽  
Size Effects ◽  
Social Group ◽  
Group Living ◽  
Relative Importance ◽  
Net Benefit ◽  
Significant Group ◽  
Group Size Effect ◽  
Variation Explained

AbstractA commonly cited benefit of group living is the ability for individuals to reduce the time devoted to scanning for predators with increasing group size - the 'group size effect'. Interestingly, most studies reporting a group size effect have focused on documenting a significant group size effect and did not discuss the relative 'importance' of group size. One way to study the relative importance of group size is to calculate the amount of variation in vigilance explained by group size. I studied effects of social group size on golden marmot (Marmota caudata aurea) vigilance in two ways. First, I estimated the overall amount of time marmots were vigilant during their morning active periods. Second, I estimated the amount of time marmots were vigilant specifically while foraging. Analyses statistically controlled for several factors that have been suggested to confound the study of group size effects. While marmots were active, only 14% of the variation in vigilance was explained by social group size. For foraging marmots, even less variation (about 6%) was explained by social group size. The amount of variation explained by social group size in golden marmots is considerably less that reported in several studies of other species where explained variation was reported or could be estimated from data. Some of the discrepancy between variation explained in this and other studies may stem from my focus on social group size which appears to explain less variation than the more commonly studied foraging aggregation size. However, species differ in the amount of time they devote to foraging and therefore vary in the magnitude of net benefit from group size effects. Future comparative work will be required to rigorously study the relationship between amount of time foraging and the magnitude of group size effects.

Contrasts in body size and growth suggest that high population density results in faster pace of life in Damaraland mole-rats (Fukomys damarensis)

2018 ◽  
Vol 96 (8) ◽  
pp. 920-927 ◽  
Author(s):  
K.T. Finn ◽  
D.M. Parker ◽  
N.C. Bennett ◽  
M. Zöttl
Keyword(s):  
Body Size ◽  
Population Density ◽  
Litter Size ◽  
Group Size ◽  
Growth Rates ◽  
High Population ◽  
Low Density ◽  
High Population Density ◽  
Population Densities ◽  
Study Sites

We studied the correlates of population density and body size, growth rates, litter size, and group size in Damaraland mole-rats (Fukomys damarensis (Ogilby, 1838)) at two study sites with contrasting population densities. Group size, litter size, and the probability of recapture were independent of study site. However, body size differed between the two study sites, suggesting that population density may affect life-history traits in social mole-rats. At the low-density site (0.13 groups/ha), individuals were significantly larger and subordinate males showed higher growth rates than at the high-density site (0.41 groups/ha), which may indicate that high population density in subterranean rodents enhances pace of life. The larger size of nonreproductive individuals at the low-density site could adapt individuals at lower population densities to larger dispersal distances.

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.

Affiliations, aggressions and an adoption: Male–male relationships in wild bonobos

2018 ◽  
Author(s):  
Martin Surbeck ◽  
Gottfried Hohmann
Keyword(s):  
Close Relationships ◽  
Group Living ◽  
Mate Competition ◽  
Male Group ◽  
Cooperative Hunting ◽  
Sexual Behaviours ◽  
Study Population ◽  
Living Species ◽  
The Way

The nature of the relationships between males is a characteristic trait of many multi-male group living species with implications for the individuals. In our study population of bonobos, certain male dyads exhibit clear preferences for ranging in the same party and sitting in proximity. These preferences are not reflected in the frequency of aggression towards each other and only to some extent in their affiliative and socio-sexual behaviours. While bonobo males at LuiKotale clearly do not benefit from close relationships in the way chimpanzee males do (cooperative hunting, territorial patrol, mate competition), some relationships might result from close associations between their mothers. In some particular situations, these male relationships can be very important as in the case of an orphan adopted by his older maternal brother. La nature des relations entre mâles est un trait caractéristique de plusieurs groupes qui ont plusieurs mâles, avec des implications au niveau d’individus. Dans notre étude des populations de bonobos, certains dyades mâles montrent une préférence à aller dans le même groupe et s’asseoir proche l’un de l’autre. Cette préférence n’est pas reflétée dans la fréquence d’agression entre eux et est seulement lié, à degrés, à leur comportements socio-sexuels et d’appartenance. Tandis que les mâles bonobos à LuiKotale ne profitent pas de leur fortes relations comme les chimpanzés mâles (chasse coopérative, patrouille territoriale, compétition pour compagnon), ils peuvent aider leur partenaires à supporter le stress de la vie en groupe et peuvent en conséquence contribuer au bien-être des individus. Quelques proches associations entre les mâles peuvent provenir d’associations entre leurs mères. Dans quelques situations particulières, ces relations mâles prouvent leur importance comme dans le cas d’un orphelin adopté par son grand frère maternel.

Sign in / Sign up

Export Citation Format

Share Document