scholarly journals Is group size related to longevity in mammals?

2010 ◽  
Vol 6 (6) ◽  
pp. 736-739 ◽  
Author(s):  
Jason M. Kamilar ◽  
Richard G. Bribiescas ◽  
Brenda J. Bradley
Keyword(s):  
Group Size ◽  
Life History Theory ◽  
Large Species ◽  
Mammal Species ◽  
Significant Group ◽  
Maximum Longevity ◽  
Extrinsic Mortality ◽  
Risk Of Mortality ◽  
Risk Of Predation ◽  
Extrinsic Risk

Life-history theory predicts that reduced extrinsic risk of mortality should increase species longevity over evolutionary time. Increasing group size should reduce an individual's risk of predation, and consequently reduce its extrinsic risk of mortality. Therefore, we should expect a relationship between group size and maximum longevity across species, while controlling for well-known correlates of longevity. We tested this hypothesis using a dataset of 253 mammal species and phylogenetic comparative methods. We found that group size was a poor predictor of maximum longevity across all mammals, as well as within primates and rodents. We found a weak but significant group-size effect on artiodactyl longevity, but in a negative direction. Body mass was consistently the best predictor of maximum longevity, which may be owing to lower predation risk and/or lower basal metabolic rates for large species. Artiodactyls living in large groups may exhibit higher rates of extrinsic mortality because of being more conspicuous to predators in open habitats, resulting in shorter lifespans.

scholarly journals Ecology and mode-of-life explain lifespan variation in birds and mammals

2014 ◽  
Vol 281 (1784) ◽  
pp. 20140298 ◽  
Author(s):  
Kevin Healy ◽  
Thomas Guillerme ◽  
Sive Finlay ◽  
Adam Kane ◽  
Seán B. A. Kelly ◽  
...  
Keyword(s):  
Body Mass ◽  
Life History Theory ◽  
Interspecific Variation ◽  
Activity Period ◽  
Large Species ◽  
Term Survival ◽  
Extrinsic Mortality ◽  
Ecological Selection ◽  
Lifespan Variation ◽  
Mode Of Life

Maximum lifespan in birds and mammals varies strongly with body mass such that large species tend to live longer than smaller species. However, many species live far longer than expected given their body mass. This may reflect interspecific variation in extrinsic mortality, as life-history theory predicts investment in long-term survival is under positive selection when extrinsic mortality is reduced. Here, we investigate how multiple ecological and mode-of-life traits that should reduce extrinsic mortality (including volancy (flight capability), activity period, foraging environment and fossoriality), simultaneously influence lifespan across endotherms. Using novel phylogenetic comparative analyses and to our knowledge, the most species analysed to date ( n = 1368), we show that, over and above the effect of body mass, the most important factor enabling longer lifespan is the ability to fly. Within volant species, lifespan depended upon when (day, night, dusk or dawn), but not where (in the air, in trees or on the ground), species are active. However, the opposite was true for non-volant species, where lifespan correlated positively with both arboreality and fossoriality. Our results highlight that when studying the molecular basis behind cellular processes such as those underlying lifespan, it is important to consider the ecological selection pressures that shaped them over evolutionary time.

Seasonal Habitat Use by Nubian Ibex (Capra Nubiana) Evaluated with Behavioral Indicators

2011 ◽  
Vol 57 (3) ◽  
pp. 223-246 ◽  
Author(s):  
Solomon A. Tadesse ◽  
Burt P. Kotler
Keyword(s):  
Group Size ◽  
Age Structure ◽  
Time Allocation ◽  
Environmental Variables ◽  
Time Budget ◽  
Habitat Type ◽  
Time Budgets ◽  
Behavioral Models ◽  
Risk Of Predation ◽  
Focal Observation

Nubian ibex (Capra nubiana) prefer steep terrain in their landscape to reduce risks of predation and human nuisance disturbances. They also use vigilance and time allocation to manage risk of predation. We studied time budgets and habitat selection of Nubian ibex to: (1) identify the habitat variables to which Nubian ibex were behaviorally responsive; (2) investigate how time budget responses of Nubian ibex were related to season, slope condition, group size, and sex-age structure; and (3) develop behavioral-based models that account for the variations in the behaviors of Nubian ibex across the landscape and seasons.To quantify time budgets, we took regular field observations on focal individuals of Nubian ibex classified according to their habitat, group size, sex, and age. For each focal observation, we quantified environmental variables that were thought to influence the behavioral responses of ibex. Then, we developed behavioral models by correlating the proportion of behaviors measured in focal animal observations to the influential environmental variables. The behaviors of Nubian ibex significantly varied with sex and age structure, season, habitat type, and slope conditions. Adult females are more vigilant than adult male ibex, especially in the spring. This correlates with breeding and nursing activities. Based on the characteristics of the habitat, ibex behave to minimize risks of predation and human nuisance disturbances while maximizing their food intake.

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.

Relationships between group size, feeding time, and agonistic behavior of mountain goats

1985 ◽  
Vol 63 (11) ◽  
pp. 2501-2506 ◽  
Author(s):  
Kenneth L. Risenhoover ◽  
James A. Bailey
Keyword(s):  
Group Size ◽  
Agonistic Behavior ◽  
Alpine Tundra ◽  
Feeding Time ◽  
Oreamnos Americanus ◽  
Movement Rates ◽  
Average Group ◽  
Risk Of Predation ◽  
Mountain Goats ◽  
Average Group Size

Relationships between group size, intragroup spacing, movement rates, foraging behavior, and frequency of agonistic behavior of mountain goats (Oreamnos americanus) using alpine tundra were examined during summer. Feeding time of goats increased with group size to about 12 goats because of a reduction in time devoted to alert behavior. Rates of movement by foraging goats increased with group size, whereas rates of agonistic behavior between goats declined with increased group size. Intragroup spacing declined as group size increased. Nannies and 2-year-old goats were more aggressive than were other sex- or age-classes. Two-year-old goats, yearlings, and billies received more threatening displays than did other classes. In Colorado, nannies with kids form large nursery bands on alpine tundra. This behavior can reduce the risk of predation to individuals while allowing nannies with kids to exploit forage away from precipitous terrain. Average group size may be a useful index to forage abundance and continuity on summer goat range.

Huemul (Hippocamelus bisulcus) sociality at a periglacial site: sexual aggregation and habitat effects on group size

1999 ◽  
Vol 77 (7) ◽  
pp. 1083-1091 ◽  
Author(s):  
Alejandro Frid
Keyword(s):  
Group Size ◽  
Food Distribution ◽  
Sexually Dimorphic ◽  
Valley Bottom ◽  
Felis Concolor ◽  
Hippocamelus Bisulcus ◽  
Risk Of Predation ◽  
The Social ◽  
Young Of The Year ◽  
Behavioural Diversity

I studied social organisation of the huemul (Hippocamelus bisulcus), an Andean deer, during spring in coastal Chile. Analyses are based on individually recognised adults without young of the year. Deer that were not alone generally joined groups containing both sexes, and the proportion of time individuals spent in mixed-sex groups increased with the individual's mean group size. The absence of sexual segregation during spring is unusual among sexually dimorphic ungulates, and possibly reflected little variability in food distribution and (or) sex-specific predation pressure. Group sizes of individuals observed on multiple days increased strongly with distance from rocky slopes, and this relationship appeared to be unaffected by food distribution. These results suggest that the risk of predation, probably from cougars (Felis concolor) and (or) human hunters with dogs (Canis familiaris), is lower on rocky slopes than in valley-bottom habitats. Group sizes of individuals seen only once, however, were independent of distance from rocky slopes, possibly because these individuals were transients that did not integrate into the social structure of resident deer. The effect of rocky slopes on group sizes of individuals observed on multiple days is more characteristic of mountain Caprinae than of deer. The huemul is endangered, and its extinction could represent a substantial loss in the behavioural diversity of the Cervidae.

scholarly journals Towards cancer-aware life-history modelling

2015 ◽  
Vol 370 (1673) ◽  
pp. 20140234 ◽  
Author(s):  
Hanna Kokko ◽  
Michael E. Hochberg
Keyword(s):  
Life History ◽  
Life Histories ◽  
Life History Theory ◽  
Cancer Susceptibility ◽  
Natural Populations ◽  
Sexually Dimorphic ◽  
Adaptive Responses ◽  
Extrinsic Mortality ◽  
Size Evolution ◽  
In The Wild

Studies of body size evolution, and life-history theory in general, are conducted without taking into account cancer as a factor that can end an organism's reproductive lifespan. This reflects a tacit assumption that predation, parasitism and starvation are of overriding importance in the wild. We argue here that even if deaths directly attributable to cancer are a rarity in studies of natural populations, it remains incorrect to infer that cancer has not been of importance in shaping observed life histories. We present first steps towards a cancer-aware life-history theory, by quantifying the decrease in the length of the expected reproductively active lifespan that follows from an attempt to grow larger than conspecific competitors. If all else is equal, a larger organism is more likely to develop cancer, but, importantly, many factors are unlikely to be equal. Variations in extrinsic mortality as well as in the pace of life—larger organisms are often near the slow end of the fast–slow life-history continuum—can make realized cancer incidences more equal across species than what would be observed in the absence of adaptive responses to cancer risk (alleviating the so-called Peto's paradox). We also discuss reasons why patterns across species can differ from within-species predictions. Even if natural selection diminishes cancer susceptibility differences between species, within-species differences can remain. In many sexually dimorphic cases, we predict males to be more cancer-prone than females, forming an understudied component of sexual conflict.

Distance To Cover, Visual Obstructions, and Vigilance in House Sparrows

Behaviour ◽  
1987 ◽  
Vol 102 (3-4) ◽  
pp. 231-237 ◽  
Author(s):  
Steven L. Lima
Keyword(s):  
Group Size ◽  
Passer Domesticus ◽  
Exact Nature ◽  
House Sparrows ◽  
Factors Influencing ◽  
Risk Of Predation ◽  
Protective Cover

AbstractHouse sparrows (Passer domesticus) feeding away from protective cover decrease their level of vigilance as group size increases. In contrast to recent studies, however, their level of vigilance decreases when feeding farther from cover or in the presence of visual obstructions. These apparent discrepancies reflect the potential complexity in the response of vigilance to various aspects of the risk of predation; scanning need not necessarily increase with the risk of predation. Much work as to the exact nature of the factors influencing vigilance remains to be done before we can fully understand its response to various environmental manipulations.

Vigilance and Grouping in the Eastern Gray Kangaroo, Macropus giganteus

1993 ◽  
Vol 41 (4) ◽  
pp. 325 ◽  
Author(s):  
AML Colagross ◽  
A Cockburn
Keyword(s):  
Group Size ◽  
Edge Effect ◽  
Group Formation ◽  
Reproductive Status ◽  
Risk Of Predation ◽  
Vigilance Behaviour ◽  
Reproductive Females ◽  
Group Sex ◽  
Free Ranging ◽  
Number Of Individuals

Group formation may help animals reduce their risk of predation and allow more time for activities other than vigilance against predators. Eastern grey kangaroos, Macropus giganteus, are gregarious and form open-membership groups. Vigilance behaviour of free-ranging kangaroos was observed in relation-to number of individuals within the group, sex and reproductive status of individuals, proximity to cover and position within the group. Our data support the view that kangaroos adjust their behaviour in relation to the risk of predation. Reproductive females, individuals on the periphery of the group and individuals in groups far from cover were most vigilant. Contrary to previous reports, vigilance behaviour was not influenced by group size except through the edge effect-the tendency of the proportion of individuals on the periphery of the group to decline as group size increases.

scholarly journals Faunal complex of the Early Pleistocene Muhkai 2 locality

2021 ◽  
Vol 325 (1) ◽  
pp. 82-90
Author(s):  
M.V. Sablin ◽  
K.Yu. Iltsevich
Keyword(s):  
Natural Environment ◽  
Stone Tools ◽  
Early Pleistocene ◽  
Site Formation ◽  
Large Species ◽  
Faunal Assemblage ◽  
Mammal Species ◽  
Large Mammal ◽  
Small Areas ◽  
Cultural Layers

The Early Pleistocene locality Muhkai 2 was discovered in Central Dagestan, northeastern Caucasus, Russia, in 2006. Archaeological investigations of the site have been directed by Corresponding member of RAS H.A. Amirkhanov (Institute of Archaeology RAS, Moscow). The article presents the results of the study of osteological material from the excavations of 2006–2017. The cultural layers with stone tools and mammal bones are found within stratum of brownish-grey petrified loams with reversed magnetization. We identified 14 large species of mammals, which are indicators for the dating of the faunal assemblage and crucial in identifying the specific characteristics of the natural environment at the time of site formation. Stenon horse and Etruscan wolf dominate the spectrum of species at Muhkai 2. All large mammal species from the site are inhabitants of open and semi-open landscapes and animals indicative of closed biotopes are absent. The biotope appears to have been a dry savannah-steppe with small areas of forest vegetation. The climate at this time was warm and quite arid. Most likely, the animals died here due to natural causes and their carcasses were buried at the bottom of an ancient, slightly saline and shallow, temporary body of water. Data from the theriofauna place the age of the site Muhkai 2 within the chronological range of 2.1–1.77 Mya.

scholarly journals Risk of predation alters resource allocation in Daphnia under food limitation

2019 ◽  
Vol 42 (1) ◽  
pp. 45-56 ◽  
Author(s):  
Sandra Klintworth ◽  
Eric Von Elert
Keyword(s):  
Resource Allocation ◽  
Fatty Acid ◽  
Life History Theory ◽  
Fatty Acid Content ◽  
Food Limitation ◽  
Somatic Growth ◽  
The Body ◽  
Food Quantity ◽  
Risk Of Predation ◽  
Food Concentrations

Abstract Life-history theory predicts that animals adjust their resource allocation to somatic growth or to reproduction to maximize fitness. Resource allocation in Daphnia is known to respond to quantitative food limitation as well as to kairomones released from predators. Here we investigated in a full-factorial design how kairomone from larvae of Chaoborus flavicans, a gape-limited predator, and food quantity (0.5 mg C/L versus 1.5 mg C/L) affect the fatty acid allocation of D. pulex. Low food diminished somatic growth, clutch size and clutch biomass and increased neckteeth formation in response to the kairomone. Low food further led to increased fatty acid amounts per individual egg as well as to increased fatty acid content in eggs and to increased relative fatty acid allocation to reproduction. The latter effect was suppressed by kairomone of Chaoborus, whereas on high food the provision of eggs was further enhanced. We also found that more eicosapentaenoic acid was retained in the body of mothers in the presence of the predator at low food concentrations. These findings indicate that under food limitation and in the presence of kairomone from Chaoborus larvae, Daphnia switches from allocation into current reproduction to investment into future reproductive events.

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