Group dynamics and local population density dependence of group size in the Pyrenean chamois, Rupicapra pyrenaica

2008 ◽  
Vol 75 (2) ◽  
pp. 361-369 ◽  
Author(s):  
Dominique Pépin ◽  
Jean-François Gerard
Keyword(s):  
Population Density ◽  
Density Dependence ◽  
Group Size ◽  
Group Dynamics ◽  
Local Population ◽  
Rupicapra Pyrenaica ◽  
Pyrenean Chamois

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 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.

The spatial dynamics of White-browed Babbler groups in a fragmented agricultural landscape

2002 ◽  
Vol 8 (4) ◽  
pp. 271 ◽  
Author(s):  
Peter G. Cale
Keyword(s):  
Home Range ◽  
Breeding Season ◽  
Group Dynamics ◽  
Agricultural Landscape ◽  
Local Population ◽  
Breeding Site ◽  
Home Ranges ◽  
Effective Population ◽  
Study Sites ◽  
Group Movements

White-browed Babbler Pomatostomus superciliosus groups occupying linear strips of vegetation had breeding territories that were smaller in area and had longer linear dimensions than those occupying patches. A group's non-breeding home range was larger than its breeding territory. Groups occupying linear/patch home ranges expanded the linear extent and area of their home ranges more than those within other home range configurations. Some groups moved during the non-breeding season and this was more likely to occur if the group occupied a remnant with a low abundance of invertebrates during summer. Some groups that moved returned prior to the next breeding season, but the majority were never seen again. New groups moved into the study sites and established in vacant home ranges. This suggests that those groups that left the study sites may have established new home ranges elsewhere. Breeding site fidelity was lower in groups that had failed in previous breeding attempts. Therefore, group movements were influenced by the feeding and breeding quality of the habitat. However, the configuration of the local population also influenced group movements with those groups on the edge of a local population being more likely to move than those in the interior. New groups were formed by two processes; group dispersal, where groups generally filled a vacant home range, and group budding, which involved the splitting of a large group. Group dispersal maintained group densities while group budding increased the density of groups in a local population. These two processes were common, producing localized fluctuations in the density of groups. Since babbler groups contain only one breeding pair, changes in group density represent changes in effective population size. Therefore, group dynamics may be important to the persistence of local populations of White-browed Babblers, especially in landscapes that have suffered from habitat loss and fragmentation.

scholarly journals Changing Land Use and Population Density Are Degrading Water Quality in the Lower Mekong Basin

Water ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 1948
Author(s):  
Flavia Tromboni ◽  
Thomas E. Dilts ◽  
Sarah E. Null ◽  
Sapana Lohani ◽  
Peng Bun Ngor ◽  
...  
Keyword(s):  
Water Quality ◽  
Land Use ◽  
Population Density ◽  
Local Population ◽  
Reference Conditions ◽  
Mekong River ◽  
Land Use Impacts ◽  
Wet Season ◽  
Mekong Basin ◽  
Lower Mekong Basin

Establishing reference conditions in rivers is important to understand environmental change and protect ecosystem integrity. Ranked third globally for fish biodiversity, the Mekong River has the world’s largest inland fishery providing livelihoods, food security, and protein to the local population. It is therefore of paramount importance to maintain the water quality and biotic integrity of this ecosystem. We analyzed land use impacts on water quality constituents (TSS, TN, TP, DO, NO3−, NH4+, PO43−) in the Lower Mekong Basin. We then used a best-model regression approach with anthropogenic land-use as independent variables and water quality parameters as the dependent variables, to define reference conditions in the absence of human activities (corresponding to the intercept value). From 2000–2017, the population and the percentage of crop, rice, and plantation land cover increased, while there was a decrease in upland forest and flooded forest. Agriculture, urbanization, and population density were associated with decreasing water quality health in the Lower Mekong Basin. In several sites, Thailand and Laos had higher TN, NO3−, and NH4+ concentrations compared to reference conditions, while Cambodia had higher TP values than reference conditions, showing water quality degradation. TSS was higher than reference conditions in the dry season in Cambodia, but was lower than reference values in the wet season in Thailand and Laos. This study shows how deforestation from agriculture conversion and increasing urbanization pressure causes water quality decline in the Lower Mekong Basin, and provides a first characterization of reference water quality conditions for the Lower Mekong River and its tributaries.

scholarly journals Increasing water temperatures exacerbate the potential for density dependence in juvenile steelhead

2018 ◽  
Vol 75 (6) ◽  
pp. 897-907 ◽  
Author(s):  
Knut Marius Myrvold ◽  
Brian Patrick Kennedy
Keyword(s):  
Density Dependence ◽  
Water Temperature ◽  
Positive Relationship ◽  
Local Population ◽  
Negative Relationship ◽  
Skewed Distribution ◽  
Energetic Cost ◽  
Size Distributions ◽  
Local Densities ◽  
A1b Scenario

We studied the potential effects of predicted climate change on the energetic demands of juvenile steelhead (Oncorhynchus mykiss) and their consequences for local population size and structure in Idaho, USA. Projected increases in water temperature incurred on average a 10% higher energetic cost by 2040 (range 7.0%–12.5% among study reaches in the watershed) and a 16% increase (range 8.5%–21.3%) by 2080 following the A1B scenario. The predicted increase in energetic cost was largest in the coolest stream reaches, where the proportional increases in energetic cost exceed that of temperature. Energetically, and in absence of increases in food supply, local densities were consequently expected to decline. We examined which factors best described the shape of current size distributions to explore future size distributions as temperatures increase. Mass distribution skewness was best explained by local biomass (positive relationship) and water temperature (negative relationship). The results suggest that local steelhead cohorts will approach a platykurtic, slightly negatively skewed distribution with increasing temperatures and demonstrate that temperature can exacerbate demographic density dependence in fish populations.

scholarly journals Instantaneous areal population density of entire Atlantic cod and herring spawning groups and group size distribution relative to total spawning population

2018 ◽  
Vol 20 (2) ◽  
pp. 201-213 ◽  
Author(s):  
Nicholas C. Makris ◽  
Olav Rune Godø ◽  
Dong Hoon Yi ◽  
Gavin J. Macaulay ◽  
Ankita D. Jain ◽  
...  
Keyword(s):  
Population Density ◽  
Size Distribution ◽  
Group Size ◽  
Atlantic Cod ◽  
Group Size Distribution

Adjustment of fecundity and sex ratio in response to social environments in a haplodiploid mite

2022 ◽  
Author(s):  
Nuwan Weerawansha ◽  
Qiao Wang ◽  
Xiong Zhao He
Keyword(s):  
Population Density ◽  
Sex Ratio ◽  
Population Size ◽  
Local Population ◽  
Female Offspring ◽  
Social Environments ◽  
Positive Interaction ◽  
Offspring Sex Ratio ◽  
Offspring Sex ◽  
Large Populations

Animals can adjust reproductive strategies in favour of corporation or competition in response to local population size and density, the two key factors of social environments. However, previous studies usually focus on either population size or density but ignore their interactions. Using a haplodiploid spider mite, Tetranychus ludeni Zacher, we carried out a factorial experiment in the laboratory to examine how ovipositing females adjust their fecundity and offspring sex ratio during their early reproductive life under various population size and density. We reveal that females laid significantly more eggs with increasing population size and significantly fewer eggs with increasing population density. This suggests that large populations favour cooperation between individuals and dense populations increase competition. We demonstrate a significant negative interaction of population size and density that resulted in significantly fewer eggs laid in the large and dense populations. Furthermore, we show that females significantly skewed the offspring sex ratio towards female-biased in small populations to reduce the local mate competition among their sons. However, population density incurred no significant impact on offspring sex ratio, while the significant positive interaction of population size and density significantly increased the proportion of female offspring in the large and dense populations, which will minimise food or space competition as females usually disperse after mating at crowded conditions. These results also suggest that population density affecting sex allocation in T. ludeni is intercorrelated with population size. This study provides evidence that animals can manipulate their reproductive output and adjust offspring sex ratio in response to various social environments, and the interactions of different socio-environmental factors may play significant roles.

Density-Dependent Population Growth

2020 ◽  
pp. 29-46
Author(s):  
Michael J. Fogarty ◽  
Jeremy S. Collie
Keyword(s):  
Population Density ◽  
Population Growth ◽  
Density Dependence ◽  
Multiple Equilibria ◽  
Dynamical Behavior ◽  
Logistic Growth ◽  
Density Dependent ◽  
Per Capita ◽  
Discrete Time Models ◽  
Complex Dynamical Behavior

The observation that no population can grow indefinitely and that most populations persist on ecological timescales implies that mechanisms of population regulation exist. Feedback mechanisms include competition for limited resources, cannibalism, and predation rates that vary with density. Density dependence occurs when per capita birth or death rates depend on population density. Density dependence is compensatory when the population growth rate decreases with population density and depensatory when it increases. The logistic model incorporates density dependence as a simple linear function. A population exhibiting logistic growth will reach a stable population size. Non-linear density-dependent terms can give rise to multiple equilibria. With discrete time models or time delays in density-dependent regulation, the approach to equilibrium may not be smooth—complex dynamical behavior is possible. Density-dependent feedback processes can compensate, up to a point, for natural and anthropogenic disturbances; beyond this point a population will collapse.

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