Social and Population Dynamics of Yellow-Bellied Marmots: Results from Long-Term Research

Armitage, Kenneth B.

doi:10.1146/annurev.es.22.110191.002115

Cited by 162 publications

(112 citation statements)

References 79 publications

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“…Two different processes affect matrilineal number and size: matrilineal size increases when daughters are retained in their natal group and number of matrilines increases because of immigration and the fission of large matrilines (14,15,17,18). Fission of large matrilines is much more important than immigration in those habitat patches that typically support more than one matriline (16). The rank order of sites for survivorship is not significantly correlated (r s ϭ 0.426, 0.1 Ͼ P Ͼ 0.05) with the rank order of sites for R o , which suggests that resources and social organization act somewhat differently on these two measures of fitness.…”

Section: Resultsmentioning

confidence: 91%

“…Social factors affecting fitness include competition between matrilines and cooperative and competitive behavior within matrilines. Between matriline competition may be expressed by infanticide (13), agonistic behavior (14), and reproductive suppression (4,15); competitive behavior within matrilines includes agonistic behavior directed toward close kin (15,16) and reproductive suppression of daughters by their mothers (4). Cooperative behavior is expressed as amicable social interactions; i.e., allogrooming and greeting (16), and by defense of home range against conspecific intruders (4).…”

Section: Methodsmentioning

confidence: 99%

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Social enhancement of fitness in yellow-bellied marmots

Armitage

Schwartz

2000

Proc. Natl. Acad. Sci. U.S.A.

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The yellow-bellied marmot (Marmota flaviventris) is a social, ground-dwelling squirrel that lives either individually or in kin groups of from two to five adult females. Philopatry and daughter recruitment lead to the formation and persistence of matrilines at habitat sites. By using 37 years of demographic data for 12 habitat sites, we could determine long-term trends in the effects of group size on two measures of fitness, survivorship and net reproductive rate, which otherwise are obscured by annual fluctuations in these measures. Both size and number of matrilines varied among sites and survivorship and net reproductive rate varied among sites and among matriline sizes. The role of social organization was explored further by examining the effect of matriline size, averaged over all years and sites, on fitness. For both survivorship and net reproductive rate the relationship with matriline size was curvilinear. Fitness increased with the increase in matriline size and then decreased in the largest groups. Decreased fitness in matrilines of four or five was associated with agonistic behavior, a large number of 2-year-old females in the social group, and reproductive suppression. There is no evidence that females acted to increase their fitness by increasing indirect fitness; i.e., by assisting relatives, but attempted to increase direct fitness. Direct fitness increased when mortality and fission of large matrilines reduced group size and the surviving females increased reproduction. Because sociality in mammals is potentially costly due to intraspecific competition, parasite transmission, or suppressed reproduction (1), sociality must enhance inclusive fitness directly through the production of offspring and possibly indirectly through the production of nondescendant relatives when compared with nonsocial conspecifics. However, in many societies, sociality is associated with reproductive skew; a few individuals do all or most of the breeding (2). Reproductive skew may be associated with a trade-off between reproduction and survival. For example, highly social species of marmots, such as Marmota olympus and M. vancouverensis, which do not reproduce before age 3, have higher survival at ages 1-4 than the less social M. flaviventris, which reproduces at age 2 (3-5). Increased group size is widely associated with reduced per capita reproductive success; e.g., increased social complexity among species of ground-dwelling sciurids is associated with decreased litter size and a smaller proportion of females breeding (6). Among cooperatively breeding species reproduction may be limited to a single female in a group (3, 7), and per capita reproductive success is lower in large coteries than in small coteries of black-tailed prairie dogs (8). In contrast, by using 37 years of field observations, we report that net reproductive rate (R o ), a direct measure of fitness (9), initially increases with increased group size in the yellow-bellied marmot (Marmota flaviventris), then decreases in the largest groups. Furthermore, ...

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Section: Resultsmentioning

confidence: 91%

Section: Methodsmentioning

confidence: 99%

Social enhancement of fitness in yellow-bellied marmots

Armitage

Schwartz

2000

Proc. Natl. Acad. Sci. U.S.A.

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“…Second, we did not take immigration into consideration. Although immigration is rare (Armitage, 2014), it ultimately plays an important role in the replacement of individuals lost to a population (Armitage, 1991). For example, in 1995, a prolonged snowfall caused a substantial population crash (Armitage, 2014), and our baseline non-plasticity model failed to capture the full recovery by the population.…”

Section: Discussionmentioning

confidence: 99%

“…Yellow-bellied marmots hibernate for 7-8 months annually (Armitage, 1991). Thus, they must gain sufficient body mass during their relatively short active season to survive hibernation.…”

Section: Study Speciesmentioning

confidence: 99%

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Can individual variation in phenotypic plasticity enhance population viability?

Maldonado-Chaparro

Read

Blumstein

2017

Ecological Modelling

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a b s t r a c tIn response to climatic and other sources of environmental variation, individuals within a population may adjust their behavioral, morphological or physiological responses to varying environmental conditions through phenotypic plasticity. In seasonal environments, time constraints related to seasonality, as well as variation in climatic factors, may affect body mass growth rates. To cope with the consequences of a harsh period, individuals may, for example, compensate for lost body mass by accelerating their growth rate in the following period. Phenotypically plastic responses like this can, therefore, directly affect body mass, which may affect individual fitness and, ultimately, population dynamics. Here, we use a well-studied population of yellow-bellied marmots, Marmota flaviventris, in Colorado to parametrize and develop an individual-based model (IBM) to investigate how phenotypically plastic responses in body mass growth rate may compensate for an individual's bad start after a harsh period (compensatory growth), and to explore whether individual variation in compensatory growth favors population persistence under less favorable climatic scenarios. A simulation model that allowed marmots with a body mass less than the population's average body mass to compensate their growth provided the best match with observed population sizes, suggesting the importance of trade-offs in population dynamics. We also found that compensatory growth plays an important role in decreasing the probability of extinction under both less favorable colder and random climate scenarios. Our results lead to a deeper understanding of the mechanisms that govern population fluctuations and highlight the importance of quantifying the fitness cost of phenotypically plastic responses.

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