Individual differences in the behavior of juvenile yellow-bellied marmots

Summary Yellow-bellied marmots express considerable individuality as measured by behavior in a maze, mirror-image stimulation (MIS), and social behavior in the field. Maze behavior discriminated between residents and dispersers; residents explored the maze more widely than did dispersers. Males could not be distinguished from females nor survivors from non-survivors by their maze behavior. A group of six yearling females was established to examine the relationship between individual behavioral phenotypes (as determined by MIS) and social behavior in the field. This experiment provided a situation in which social behavior was not influenced by age, sex, or reproduction (female yearlings are non-reproductive). The number of social interactions per individual ranged from 25 to 69. The number of observed interactions per individual differend significantly from the expected for greeting, allogrooming, total amicable, play, and total social interactions. Rankings of greeting, total amicable, and total interactions were directly correlated with rankings on the avoidance axis; play was inversely correlated with the approach axis. These results suggest that marmots have individual behavioral phenotypes that are expressed in their social interactions with their conspecifics.     

Kinship,reproductive strategies and social dynamics of yellow-bellied marmots

Summary Social behavior of yellow-bellied marmots was observed for three years in colonies where kinship was known and for one year in a high elevation colony where harems were contiguous. Social dynamics of yellow-bellied marmots is dependent on kinship, group composition, and age-sex classes. This pattern is a consequence of the reproductive strategies of males and females. Females behave cohesively toward sisters or daughters, but not with sons and agonistically toward other females. Males generally behave amicably toward females and agonistically toward males, including their sons. Thus, reproductive strategies limit nepotism. This behavior is consistent with a population process in which sons typically disperse as yearlings. At least some of the variation in the expected patterns of social behaviors is attributable to individual differences. Because male and female reproductive strategies differ, a marmot population consists of two social subsystems. The female unit is the closely-related kin group which may also be a burrow group. The male unit is a harem which usually consists of two or more competing female kin groups.     

Proximate causes of natal dispersal in female yellow-bellied marmots, Marmota flaviventris

We investigated factors influencing natal dispersal in 231 female yearling yellow-bellied marmots (Marmota flaviventris) using comprehensive analysis of 10 years (1983-1993) of radiotelemetry and 37 years (1963-1999) of capture-mark-recapture data. Only individuals whose dispersal status was verified, primarily by radiotelemetry, were considered. Univariate analyses revealed that six of the 24 variables we studied significantly influenced dispersal: dispersal was less likely when the mother was present, amicable behavior with the mother and play behavior were more frequent, and spatial overlap was greater with the mother, with matriline females, and with other yearling females. Using both univariate and multivariate analyses, we tested several hypotheses proposed as proximate causes of dispersal. We rejected inbreeding avoidance, population density, body size, social intolerance, and kin competition as factors influencing dispersal. Instead, our results indicate that kin cooperation, expressed via cohesive behaviors and with a focus on the mother, influenced dispersal by promoting philopatry. Kin cooperation may be an underappreciated factor influencing dispersal in both social and nonsocial species.     

Spatiotemporal variation in survival rates: implications for population dynamics of yellow-bellied marmots

Spatiotemporal variation in age-specific survival rates can profoundly influence population dynamics, but few studies of vertebrates have thoroughly investigated both spatial and temporal variability in age-specific survival rates. We used 28 years (1976-2003) of capture-mark-recapture (CMR) data from 17 locations to parameterize an age-structured Cormack-Jolly-Seber model, and investigated spatial and temporal variation in age-specific annual survival rates of yellow-bellied marmots (Marmota flaviventris). Survival rates varied both spatially and temporally, with survival of younger animals exhibiting the highest degree of variation. Juvenile survival rates varied from 0.52 +/- 0.05 to 0.78 +/- 0.10 among sites and from 0.15 +/- 0.14 to 0.89 +/- 0.06 over time. Adult survival rates varied from 0.62 +/- 0.09 to 0.80 +/- 0.03 among sites, but did not vary significantly over time. We used reverse-time CMR models to estimate the realized population growth rate (lamda), and to investigate the influence of the observed variation in age-specific survival rates on lamda. The realized growth rate of the population closely covaried with, and was significantly influenced by, spatiotemporal variation in juvenile survival rate. High variability in juvenile survival rates over space and time clearly influenced the dynamics of our study population and is also likely to be an important determinant of the spatiotemporal variation in the population dynamics of other mammals with similar life history characteristics.     

Extra-pair paternity in alpine marmots, <Emphasis Type="Italic">Marmota marmota</Emphasis>: genetic quality and genetic diversity effects

Assuming that a male’s genetic characteristics affect those of his offspring, extra-pair copulation has been hypothesized to increase heterozygosity of the progeny—the “genetic compatibility” hypothesis—and the genetic diversity within litters—the “genetic diversity” hypothesis. We tested these two hypotheses in the alpine marmot (Marmota marmota), a socially monogamous mammal showing a high rate of extra-pair paternity (EPP). In a first step, we tested the assumption that a male’s genetic characteristics (heterozygosity and genetic similarity to the female) affect those of his offspring. Genetic similarity between parents influenced offspring heterozygosity, offspring genetic similarity to their mother, and litter genetic diversity. The father’s heterozygosity also influenced litter genetic diversity but did not affect offspring heterozygosity. Hence, heterozygosity seems not to be heritable in the alpine marmot. In a second step, we compared genetic characteristics of extra-pair young (EPY) and within-pair young (WPY). EPY were less genetically similar to their mother but not more heterozygous than WPY. EPY siblings were also less genetically similar than their WPY half siblings. Finally, the presence of EPY promoted genetic diversity within the litter. Thus, our data support both the “genetic compatibility” and the “genetic diversity” hypotheses. We discuss further investigations needed to determine the primary causes of EPP in this species.     

Foraging patterns of yellow-bellied marmosts: role of kinship and individual variability

Summary Two colonies of yellow-bellied marmots (Marmota flaviventris) at an elevation of 2900 m in Colorado were studied to elucidate the role of various behavioral and ecological factors as determinants of spatial foraging patterns. The locations of known individuals were periodically recorded. These locality data were plotted as three-dimensional block diagrams, the peak heights representing the frequency of observation. Predation risk and vegetation distribution influenced the location of foraging areas; kinship was an important factor in the determination of the amount of foraging area shared between individual marmots. Spatial overlap tended to be greater among close kin, but this was modified by individual behavioral characteristics, reproductive state, the existence of separate burrow systems within a colony, and the age of the animal. Mothers and juveniles, and littermates as young and resident yearlings, had nearly identical foraging areas.     

Social dynamics of juvenile marmots: Role of kinship and individual variability

Summary A population of eight juvenile female yellow-bellied marmots (Marmota flaviventris) was introduced into a marmot locality from which all other marmots were removed. Social interactions were monitored in the field and the individual behavioral profile of each animal was determined by mirror image stimulation. Social interactions were unequally distributed among the eight juveniles. Neither body size nor kinship were significantly related to frequencies of social interactions. Social interactions were significantly related to individual differences.     

Behavioral ecology of the neotropical termite-hunting ant Pachycondyla (= Termitopone) marginata: colony founding,group-raiding and migratory patterns

This study provides the first detailed field account of colony founding, group-raiding and migratory habits in the neotropical termite-hunting ant rPachycondyla marginata, in a semi-deciduous forest in south-east Brazil. New colonies can originate by haplometrosis, pleometrosis, or colony fission. Incipient colonies with multiple foundresses persisted longer in the field, and most excavated nests contained more than one dealated female. A total of 202 group raids by P. marginata were registered, and in all cases the raided termite species was Neocapritermes opacus. Nearly 20% of the workers within a colony engage with raiding activity. Colonies of P. marginata hunt for termites approximately every 2–3 weeks, and group-raids may last for more than 24 h. Target termite nests are up to 38 m from the ant colony, and occasionally two nests are simultaneously raided by one ant colony. Raiding ants carry 1 or 2 paralysed prey, and nearly 1600 termites can be captured during a 9-h raid. Migration by P. marginata colonies lasted over 2 days and covered distances of 2-97 m (n = 48). Average residence time at a given location was 150 days. Three basic migratory patterns were noted: colony fission (only part of the colony moves), long-distance migrations, and short-distance migrations. Both raiding and migratory activities appeared to be strongly affected by seasonal factors. The group raiding and migratory patterns of P. marginata are compared with other ant taxa with similar habits. It is concluded that P. marginata presents a rudimentary form of the so-called army ant behavior, which is highly developed in the subfamilies Dorylinae and Ecitoninae. The extremely specialized diet of P. marginata and the associated high costs of migration are features likely to prevent it from evolving a full army ant life pattern.     

Mate guarding and gallivanting by male hoary marmots (Marmota caligata)

Summary Seven years data on the vernal behavior of hoarty marmots, Marmota caligata, suggest that males engage in a two-part reproductive strategy, which consists of guarding their mates against possible copulation with additional males, and also gallivanting — wandering about in search of additional reproductive opportunities for themselves. Data are presented which support seven predictions derived from the assumption that mate guarding and gallivanting are parts of a reproductive strategy by male marmots.     

Behavioral response races, predator-prey shell games, ecology of fear, and patch use of pumas and their ungulate prey

The predator-prey shell game predicts random movement of prey across the landscape, whereas the behavioral response race and landscape of fear models predict that there should be a negative relationship between the spatial distribution of a predator and its behaviorally active prey. Additionally, prey have imperfect information on the whereabouts of their predator, which the predator should incorporate in its patch use strategy. I used a one-predator-one-prey system, puma (Puma concolor)-mule deer (Odocoileus hemionus) to test the following predictions regarding predator-prey distribution and patch use by the predator. (1) Pumas will spend more time in high prey risk/low prey use habitat types, while deer will spend their time in low-risk habitats. Pumas should (2) select large forage patches more often, (3) remain in large patches longer, and (4) revisit individual large patches more often than individual smaller ones. I tested these predictions with an extensive telemetry data set collected over 16 years in a study area of patchy forested habitat. When active, pumas spent significantly less time in open areas of low intrinsic predation risk than did deer. Pumas used large patches more than expected, revisited individual large patches significantly more often than smaller ones, and stayed significantly longer in larger patches than in smaller ones. The results supported the prediction of a negative relationship in the spatial distribution of a predator and its prey and indicated that the predator is incorporating the prey's imperfect information about its presence. These results indicate a behavioral complexity on the landscape scale that can have far-reaching impacts on predator-prey interactions.     

The influence of reproductive status on foraging by hoary marmots (Marmota caligata)

Summary Predictions were made and tested, comparing the foraging behavior of reproductive (rf) and nonreproductive (nrf) female hoary marmots, with the following findings: In June, no differences occur between rf's and nrf's, regarding daytime foraging. However, rf's forage more in the evening and during inclement weather, suggesting that greater nutritional needs and higher reproductive value select for the assumption of more risk while foraging. These differences disappear by August, when nutritional needs and reproductive values of rf's and nrf's are comparable. Finally, rf's reduce their near-burrow foraging relative to nrf's, which minimizes competition with their own young.     

试论生态学的一门分支学科:环境耐性生态学

针对目前对生态学的学科分支情况,及生态学的发展趋势和环境灾害的启示,提出了"环境耐性生态学"这一生态学的分支学科.初步明确了这一分支学科的概念,提出了它的3个研究层次的研究框架,即耐性特征、耐性规律及提高耐性的方法与途径,指出了它的核心思想是:把自然环境看成是具有"生命"的系统,有一定的耐性能力和自我恢复能力,也具有自然免疫的特征和能力.同时,指出了当前急需确定的3个生态环境耐性指标,即容许侵蚀量、容许施肥量和容许承载量.     

Zooplankton feeding ecology

Extracts of 19 of 24 species of sponge collected from Queensland. Australia, inhibited the growth of test microorganisms in in-vitro assays. A similar result has been obtained by earlier workers for extracts of species of sponge obtained from temperate waters. Some of the extracts, including extracts of Thorecta vasiforis, Arenochalina mirabilis and Acanthella kleutha, showed activity against bacterial strains that was comparable with that exhibited by penicillin G and streptomycin against these strains. Gram-positive bacteria were expecially sensitive to many extracts. Little activity was exhibited by any extract against four species of fungi tested. Some of the extracts were markedly toxic to one or more of the test organisms (a fish, a crustacean and a hydroid) used, but no clear pattern linking toxicity to these organisms with antimicrobial properties of the extracts emerged. In general, there bas a negative correlation between antimicrobial activity and surface-fouling, raising the possibility of using freedom from surface-fouling as an indicator of antimicrobial activity. Four of five encrusting species from the undersides of coral boulders showed antimicrobial activity. This study confirmed the value of using methanol-toluene extracts in field-based screening programmes, but emphasised the need to use additional extracting media such as methylene chloride in order to augment the number of antimicrobial compounds detected. There are indications that antimicrobial activity may be widespread in the order Dictyoceratida, in the order Verongida and in the order Axinellida, but sporadic in other orders of Porifera.     

Submarine daylight and ecology

The different parameters acting upon daylight before it reaches underwater organisms are discussed. Methods for measuring these parameters are reviewed, and lightsensing units equipped with hemispherical collectors and possessing a narrow spectral sensitivity band are recommended for use in marine biology. A new formula relating Secchi-disk readings to attenuation coefficients is proposed. A method is suggested which makes it possible to calculate the yearly amount of radiant energy reaching an underwater station. Possible sources of error are surveyed.     

Feeding ecology ofLeitoscoloplos fragilis

The present study examines the effects of density ofLeitoscoloplos fragilis and of fine sediment on benthic microalgal abundance and production in laboratory microcosms, and the effects of fine sediment on diffusive transport of ammonia. Microcosms having different densities ofLeitoscoloplos fragilis (Verrill, 1873) were determined in sediment collected from one of two field stations (each containing a different amount of fine particles <125 m) from Cape Henlopen, Delaware, USA, in August 1986. The worms were acclimated in a recirculating seawater system for two months prior to experiments. Chlorophylla concentrations were highest in sediments with less fine particles (<125 m). Benthic diatom production, total microbenthic metabolic activity, and concentrations of pore-water ammonia were higher in sediment microcosms containing high densities of worms.L. fragilis grew more in microcosms containing less fine particles and higher worm densities. The upward flux of ammonia across the sediment-water interface was higher in sediments with less fine particles. A greater abundance of fine particles in these sediments impedes the upward flux of ammonia to surface and nearsurface diatoms. The coupling between population density and diatom production, which can be altered by fine-particle abundance could control the distribution and stability of populations ofL. fragilis.     

Self-organized spatial patterns of vegetation in alpine grasslands

There is increased interest in vegetation spatial pattern as an indicator of transition shifts following catastrophes. Much, however, remains unknown about the mechanisms that underlie spatial pattern formations. In this study, we examined how the spatial heterogeneity of species distributions in the grasslands of the Central Pyrenees and Middle Atlas Mountains is associated with plant species diversity and the importance of self-organizing processes in the control of pattern formations. In the grasslands of the Central Pyrenees and Middle Atlas, the spatial heterogeneity of species distributions increased along a habitat degradation gradient defined by an increase in bare soil. In Central Pyrenees grasslands, however, the increase in heterogeneity was associated with self-organizing bare soil formations, rather than the self-organizing distribution of plant species. In Middle Atlas grasslands, the increased heterogeneity of species spatial distributions was a consequence of the self-organizing capacity of the composing species; the increase in bare soil was randomly distributed. In the more heavily grazed grasslands (Middle Atlas), but not in the more lightly grazed and better preserved ecosystem (Central Pyrenees), plant species richness and diversity declined significantly with an increase in grazing pressure because fewer species were able to colonize empty space. On the contrary, the colonization of bare soil by new species increased the diversity and spatial organization of new colonizing species in Central Pyrenees grassland.     

Landscape ecology of the Dutch coast

This paper is a summary and elaboration of an earlier publication in Dutch on the compilation of a landscape-ecological map, scale 1 : 50 000, of the Dutch coast. It is argued that such an integrated map is the best basis for the conservation and management of the coastal dunes and salt marshes. It may be combined with local more detailed vegetation maps, some examples of which are mentioned in the context of management. The Dutch North Sea coast is a ca. 350 km long chain of sandy beaches and sand dunes, from only 100 m to more than 10 km wide. On sheltered stretches of dune coasts along estuaries in the Southwest and on the Wadden Sea islands, salt marshes have developed. The small-scale gradient structure of the beach-dune-salt marsh complex is emphasized.