Microhabitat use by rodent species in a central Brazilian cerrado

We analysed microhabitat use by the rodents Calomys tener, Necromys lasiurus and Thalpomys lasiotis and the factors that may influence their abundances in “murundu” grasslands (open fields with termite mounds) at Aguas Emendadas Ecological Station, Planaltina, Federal District, Brazil. Two grids with 100 sampling points were established and traps were placed at each intersection of the grid, where five microhabitat variables were also measured. Rodents were trapped from June through October 2008. Microhabitat explained 21% of the variation in community structure, with grass density and the number of termite mounds explaining most of the variation. Necromys lasiurus was most often captured in areas with dense grasses, whereas T. lasiotis and C. tener were most often in areas less dense with grasses.     

Aggressive behaviours and correlates of dominance in Purple Sandpipers Calidris maritima at a communal winter roost

Aggression and the competitive ability of individual Purple Sandpipers were studied at a communal winter roost in northeast England. Aggression was most intense in high winds and more frequent in moderate breezes than when wind speeds were high or low. Higher wind speeds resulted in a drop in aggression rate, as birds had to face into the wind to maintain their balance. The ability of an individual to secure a sheltered roost position was related to its size and sex, larger individuals being dominant over those smaller than themselves. Purple Sandpipers exhibit reversed sexual size dimorphism and females were thus dominant over males. There was also weak evidence that adults were dominant over first-winter birds. The importance of size and sex in determining dominance at the roost is discussed in relation to the evolution of reversed sexual size dimorphism in Purple Sandpipers and similar shorebirds.     

Microhabitat use by Blennius fluviatilis in the Río Matarraña, Spain

SUMMARY.

• 1 Microhabitat use by Blennius fluviatilis in the Río Matarraña, Spain, varied significantly among dates during a 19-month study. Most temporal variation, however, was attributable to changes in microhabitat availability.
• 2 B. fluviatilis demonstrated non-random use of available microhabitats during each sampling period, and generally occupied deeper microhabitats with higher average current velocities dominated by rubblegravel substrates.
• 3 B. fluviatilis also demonstrated non-random use of available nest sites; males generally nested under the largest available pieces of rubble, in areas with less gravel or sand. Water column depth influenced nest site use in two of four study areas.
• 4 We found few microhabitat differences between spawning and nonspawning periods, or between males and females. In addition, microhabitat use was similar among B. fluviatilis size-groups.
• 5 Although B. fluviatilis often were over-represented in deeper, erosional areas, blennies necessarily inhabited a wide range of microhabitats because average current velocities and water depths fluctuated greatly during the study. Tolerance of a broad range of environmental conditions may contribute to the species' persistence in habitats that exhibit extreme seasonal changes in discharge such as the Matarraña.

     

Class structure and social reproduction in new Spain/Mexico

Conclusions These regional histories are not presented as an end in themselves, but as a way to transcend the theoretical and conceptual impasse of debates such as the one over the capitalist or non-capitalist nature of colonial institutions. Spanish conquest brought a unity — political, economic, ideological — to Latin America. Preconquest social formations became part of a system of merchant capital, the Spanish empire, and the Catholic church, but the local/regional response to these forces was not uniform. As Kay points out, there is a fundamental flaw in the dependency argument:... these [dependency] economists have made an important discovery. In contradistinction to the classic Marxist view that capital breaks down all pre-capitalist modes of production and creates a world in its own image, i.e., developed world; they have shown that capital despite its corrosive effects, has bolstered up archaic political and economic forms through a series of alliances with powerful elements in pre-capitalist orders .The dependency argument requires an analysis of how capitalist penetration occurs, but this same argument can be applied to Kay's discussion of merchant capital. As one reviewer has noted, it is a theory of superimposition, not penetration . Here, I propose one possible solution, namely, the examination of class structures and social reproduction.Class structure sets the limits and possibilities through which merchant capital can operate . In the three regions examined, diferent forms of surplus extraction, and, hence, different class structures, occurred: labor service developed in the Yucatan; coerced trade was extracted in Oaxaca; and wage labor was combined with debt peonage in northern Mexico. These various forms imposed different limits on how the initial economic crisis and demographic collapse under colonialism were resolved in each of the three regions. In the crisis of the 17th century, areas such as Oaxaca and the Yucatan could revert to self-sufficiency, but in the northern mining districts great hardships and depopulation occurred as markets for hacienda products declined along with silver production .Similarly, regional responses to economic recovery and reintegration depended upon their particular class structures. In the Yucatan, attempts to produce new crops — sugar and henequen — during the 19th century led to factional disputes among the elites and the rebellion of the Indian work force. In Oaxaca, increased cochineal production homogenized the Indian social formation with famine, depopulation, and occasional rebellion in the monoculture areas — the result when trade was disrupted or when the price of cochineal fell. As in the Yucatan, a dependent merchant capitalist elite was a source of factionalism in the nascent bourgeoisie in Oaxaca. In northern Mexico, the integration of mining, manufacturing, and agriculture in the Bajio resulted in an independent regional economy which freed itself from Mexico City's mercantile capital in the late 18th century . These differences reveal how unevenly merchant capital penetrates and how it can produce centrifugal forces within the same national or regional economy.Social reproduction is also important, it broadens the range of the inquiry from simple biological/demographic reproduction, to the reproduction of social/class relations; the reproduction and accumulation of capital. Too often demography is either reified into a simple cause, or neglected altogether. This expanded explanation of social reproduction begins a theoretical process linking demography, social relations, and capital accumulation . In each region, the problem of a declining population was met, not simply at the level of demographic reproduction, but at the level of social relations as well.The regional shifts in reproduction patterns are important. Regional differences can be characterized into two broad types: one, which includes the Yucatan, Oaxaca and the remaining Indian highland areas, retains Indian communities as labor reserves; the other, including the Bajio and the northern mining districts, formed estates and attracted wage laborers from such labor reserves into new social relations, though, in fact, the two types were often combined and should be considered only as analytic isolates. Demographic shifts in these two types, viewed as part of an expanded notion of social reproduction, can ground an analysis of their inter-relationship and their relation, in turn, to larger political economic systems.Alone, the concept of labor shortage is an unsatisfactory explanation of the 17th century in New Spain. Labor was available for the colonization of the northern mining districts precisely during the disastrous declines in population, and the mining industry actually experienced a boom in the early part of the era . This underscores one vital point: laws of population are not independent of the economy .The growth of New Spain during the colonial period is not reducible to the two-stage Malthusian agrarian-economic cycle of feudal societies. Rather, it is tied to the demands of an unevenly developed mercantile, and later capitalist system, but this issue must be developed elsewhere. It is precisely these differences in social reproduction that can become a way to measure the process of penetration under merchant capital. For example, highland Indian villages have been conceived as isolated labor reserves, and many anthropologists have taken isolated to mean static and unchanging. The highlands, however, experienced drastic shifts throughout the colonial period. Population shifts can be traced to increased demand for certain products, such as cochineal in Oaxaca, or labor, as on the sugar plantations in the Yucatan. Shifts in demand can turn a population surplus into a shortage without any apparent change in the demographic situation.Regarding social reproduction, the way in which merchant capital extracts surplus from areas, such as the highlands, affects demographic reproduction. Recent studies of the development of coffee plantations in the Mexican highlands have shown that this is accompanied by an increase in both population and fertility rates . In the Yucatan, conditions forced married workers to take their families to work in the fields with them . It is also possible that the repartimiento encouraged high fertility rates . In short, many of the present capitalist complaints about overpopulation or a population explosion can be attributed to the development of capitalist exploitation in these areas.What is obvious from the above discussion is the need for a theory which does not homogenize regional differences, or turn them into static, geographic areas. Analytic concepts such as class, social reproduction and merchant capital need refinement, but in the light of concrete case studies, rather than through formalized theory. Capitalist penetration from the prehistoric phase of primitive accumulation to the present remains a problem for analysis through a method recognising regional differences in class and social reproduction. It is this method which lies at the heart of a dialectical and critical anthropology.Timothy C. Parrish is a doctoral candidate in anthropology at the Graduate Faculty, New School for Social Research, New York.

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Microhabitat use and feeding strategies of the Pied Flycatcher and the Willow Warbler in their West-African winter quarters compared with resident species

Salewski, V. 2000. Microhabitat use and feeding strategies of the Pied Flycatcher and the Willow Warbler in their West-African winter quarters compared with resident species. Ostrich 71 (1 & 2): 191–193.

Habitat choice, microhabitat and foraging behaviour of the palaearctic Pied Flycatcher and Willow Warbler are described in their West-African wintering areas and are compared with those of resident species. The migrants were more flexible in habitat choice and foraging techniques, but in general did not feed in more open habitat.     

Dispersal patterns, social structure and mortality of wolves living in agricultural habitats in Spain

Wolf Canis lupus dispersal, social structure and mortality have been extensively studied in natural and semi-natural areas of North America and northern Europe but have never been assessed in agricultural areas. From 1997 to 2004, 14 wolves (11 in a wolf-saturated area and three in a low-density area) were radio-collared with long-lasting transmitters in a Spanish agricultural area containing a high-human-population density, a dense network of roads and a shortage of wild ungulates. The wolves mainly feed on an overabundance of livestock carrion. Nine wolves (one of them, three times) dispersed during the study period. The mean age and distance of natal dispersal were 24.8 months and 32 km. The natal dispersal period was much longer in wolves radio-collared in the saturated area (mean >14.6 months) than in the low-density area (<1 month). All three of the dispersers living in the low-density area, and two of the six dispersers in the saturated area settled and bred during the study. The average tenure of six breeders was 4.5 years. The radio-collared wolves spent 72% of the monitoring time living in packs and the rest living in pairs, as dispersers or as peripheral wolves, but the percentage of loners was much higher in the saturated (33.5%) than in the low density (1.6%) areas. The overall annual mortality was 18% (lower than in most populations studied in less modified habitats), but lone wolves had a significantly higher mortality than members of packs and pairs. Nine wolves died during the study, none of them due to natural causes. In general, our results are very similar to those obtained in less modified habitats, except for the dispersal distance, which was much shorter than in other studies. We suggest that barriers and habitat constraints may reduce dispersal distances in our study area.     

Microhabitat preference and vertical use of space by patas monkeys (Erythrocebus patas) in relation to predation risk and habitat structure

Habitat structure can be important in determining habitat preference of animals because it is often closely linked to factors that affect survival and reproduction, such as food availability and predation risk. Here we examine the ways in which microhabitat structure and predation risk affect the habitat preference of wild patas monkeys (Erythrocebus patas). Patas monkeys in Kenya are typically restricted to Acacia drepanolobium habitat, but within our study group's home range, there are two distinct microhabitats, one with taller trees ('tall microhabitat') and one with apparently perennially shorter trees ('short microhabitat'). Examination of ranging behavior indicates that the patas monkeys preferred the tall microhabitat. In the tall microhabitat, focal animals climbed into trees that were significantly taller than average, indicating that they preferred tall trees. Female patas monkeys spent more time scanning from tall trees than from short trees and detected predators only from taller than average trees, based on alarm call data. Their use of tall trees may have decreased their predation risk by increasing their ability to detect predators. We found no evidence of increased food availability or reduced predator presence in the tall microhabitat that could contribute to the monkeys' preference for the tall microhabitat.     

Microhabitat use and interspecific associations of introduced topmouth gudgeon Pseudorasbora parva and native fishes in a small stream

To address a lack of information on topmouth gudgeon Pseudorasbora parva introduced to watercourses, the microhabitat use of this non-native cyprinid and co-existing native species was assessed in a small stream located in southern England. Overall, microhabitat use was size-structured and significant associations were observed between topmouth gudgeon and native species, including brown trout Salmo trutta , chub Leuciscus cephalus , European bullhead Cottus gobio and stone loach Barbatula barbatula . Significant associations with environmental variables, however, were more frequent in native species than in topmouth gudgeon. Topmouth gudgeon demonstrated few habitat preferences, which were weak and limited to small specimens, emphasizing the species broad, plastic breadth of microhabitat use. This is expected to facilitate the species' successful invasion of novel aquatic systems.     

Genetic population structure, queen supersedure and social polymorphism in a social Hymenoptera

In social insects, the emergence of multiple queening is linked to changes in a suite of traits such as the reproductive life span of queens, mating patterns and population structure. We investigated queen turnover, colony longevity, spatial distribution patterns and genetic differentiation in a population of the socially polymorphic ant Formica fusca. Genetic differentiation between the social forms was absent, and mating patterns were similar in the two forms. The spatial distribution of single- and multi-queen colonies indicated an absence of colony reproduction by budding in both colony types. However, the rate of queen supersedure was high in multi-queen colonies and absent in single-queen ones. The social structure of colonies remained stable across years, but colony mortality did not differ between the two social forms. These results imply that differences between social types may appear and persist also in sympatry, and that these differences may occur in some traits, but not others, despite the presence of homogenizing gene flow.     

Changes in miombo woodland structure under different land tenure and use systems in central Zambia

Aim Population pressure and communal land ownership are often perceived as serious threats to forest conservation in savanna woodlands of central and southern Africa. I aimed at testing the hypothesis that the rate of miombo woodland recovery after clearing and re‐growth structure are determined by land tenure and use. Location Miombo woodland under customary, leasehold, forest reserve and national park on ten permanent and temporary sites was studied in central Zambia. Two sites were in mature woodland and eight sites were in re‐growth miombo ranging in age from 1 to 30 years. Methods I enumerated and measured girth at breast height (1.3 m above ground) of trees/stems in sixty‐four 20 × 10 m plots in 1982, 1986 and 2000 at six sites and annually from 1990 to 2001 at four sites to determine stem density and status (live, dead or cut) and wood biomass. A total of 239 trees were cut, wood biomass measured and the data used to develop equations for estimating wood biomass on study plots. Distance between each study site and the nearest human settlement was estimated during each sampling period using aerial photographs, topographical maps and the global positioning system. Results Land tenure was responsible for significant differences in stem density, wood biomass and rate of biomass accumulation in re‐growth following clearing of mature miombo woodland. Although stem density was highest on customary land, wood biomass and accumulation rate were lowest. The highest biomass was on plots in forest reserves, with intermediate values for leasehold and national park. Fire was responsible for tree mortality at all the study sites and its impact was highest at a site in a national park. Sites close to human settlements had the highest density of cut stems but this activity did not significantly reduce wood biomass. Rate of woodland recovery was higher on sites cleared in the 1970s than on sites cleared in the 1990s, irrespective of age of re‐growth. The development of the first, second and third re‐growths following successive woodland clearing in 1972, 1981 and 1990, respectively, was not significantly different, except for stem density which was highest in the second re‐growth. Analysis of interactions between five land tenure and use factors (independent variables) and re‐growth structure revealed that 52% (P=0.0000) of the variation in stem density was because of re‐growth age and decade in which the woodland was cleared while distance to human settlements and age of re‐growth explained 42% (P=0.0000) of the variation in wood biomass. Individually, distance to human settlements explained 25% (P=0.0000) of the variation in wood biomass accumulation rate. Conclusion The results supported the hypothesis that rate of miombo woodland recovery and structure were influenced by land tenure and use. However, analysis of interactions between factors revealed that use related factors (i.e. decade in which woodland was cleared and distance to human settlements) and re‐growth related factors (age and type of re‐growth) were more important than land tenure per se in explaining variation in miombo recovery. The conclusion from these results is that regulation of land use is more important than change in land tenure to the proper management of miombo woodland.     

Goshawk predation during winter, spring and summer in a boreal forest area of central Sweden

Predation by goshawks was studied in a central Swedish boreal forest area. Data were collected in winter (January–February) 1977-81 by tracking radio-tagged goshawks, and in the breeding season (April–July) by collecting prey remains at the nest. In the breeding season birds dominated the prey, amounting to 86% of prey number and 91% of prey biomass. Wood pigeon Columba palumbus , black grouse Tetrao tetrix , hooded crow Corvus corone cornix and jay Garrulus glandarius accounted for more than 50% of the prey animals, whereas capercaillie Tetrao urogallus and black grouse accounted for more than 50% of prey biomass. There was no functional response to black grouse density fluctuations. Every year goshawks killed significantly more females than males of both capercaillie and black grouse, due to high vulnerability of the grouse hens while laying and incubating. It was estimated that during spring and early summer goshawk predation removed 25% of the female, and 14% of the male black grouse population. In winter squirrel was the dominating prey, both in terms of number (79%) and weight (56%). The proportion of squirrel in the diet was equally high both in winters of low and high squirrel density. The high proportion of squirrel in the winterdiet, as compared to the breeding season, is believed to be due to squirrels having to accept an increased predation risk in winter, in order to feed efficiently enough.     

Matter transfer and land use by cattle in a dehesa ecosystem of Central Spain

The transfer of matter by cattle in a dehesa patureland in Central Spain has been quantified by mapping the distribution of dung and different types of cattle behaviour in several areas distinguished by their geomorphological position, vegetation structure and management regime.Cattle show a clear preference for feeding and dung depositing in the low parts of the estate. This leads to an increase in the productivity and a rapid recycling of nutrients in the pasture communities of these areas. Comparing the relative importance of both processes in each vegetational unit, dung accumulation is greater in the higher zones, while in the lower areas biomass consumption is more important. This means that movement of matter by cattle tends to favour the higher ground, in a contrary direction to the downward leaching of nutrients and related processes. In the studied dehesa, this phenomena represents an exploitation factor of the lowland areas, which maintains productive pasture communities more immature in successional terms, by the higher woodland areas, less grazed and with low turnover. This result supports claims made in other studies that animal activity — assessed in our case by the relative impacts of herbivory and dung depositions — connect adjacent ecosystems and thus tends to improve the net energy balance of the more successionally mature part of the system.Livestock movements differ in their spatial pattern during different periods of the year: dispersing in spring and becoming more concentrated and predictable during winter. The clear seasonal differences of herbaceous production in Mediterranean climates and the management activities (basically ploughing, tree pruning and fodder supply) are the main causes of this pattern.Abbreviations PI= Preference Index     

Composition and structure of a large online social network in The Netherlands

Limitations in data collection have long been an obstacle in research on friendship networks. Most earlier studies use either a sample of ego-networks, or complete network data on a relatively small group (e.g., a single organization). The rise of online social networking services such as Friendster and Facebook, however, provides researchers with opportunities to study friendship networks on a much larger scale. This study uses complete network data from Hyves, a popular online social networking service in The Netherlands, comprising over eight million members and over 400 million online friendship relations. In the first study of its kind for The Netherlands, I examine the structure of this network in terms of the degree distribution, characteristic path length, clustering, and degree assortativity. Results indicate that this network shares features of other large complex networks, but also deviates in other respects. In addition, a comparison with other online social networks shows that these networks show remarkable similarities.     

Pike and red swamp crayfish: a new case on predator-prey relationship between aliens in central Spain

Pike in the Ruidera Lakes (central Spain) chiefly ate the recently introduced crayfish Procambarus clarkii . It was the dominant prey in occurrence, number and biomass for every size class and season. Likewise, number (up to 27) and total weight of ingested crayfish were directly related with pike size. The principal prey fish were all introduced species (except the endangered Blennius fluviatilis ), most native species having disappeared since pike were introduced in 1953. (c) 1996 The Fisheries Society of the British Isles     

Riparian disturbance and community structure of a Quercus-Ulmus forest in central Japan

Population structure and ecological characteristics of component species of a riparian Ulmus-Quercus forest in central Japan were analyzed with special reference to riparian disturbance regime. Though the dbh distribution of the whole community was L-shaped, those of several component tree populations had several modes, suggesting intermittent regeneration periods in the past. Correlation of spatial distributions among tree populations and subpopulations showed 6 major groups reflecting riparian disturbances in the past and different establishment patterns among species. A cluster of small-sized tree populations (Salix sachalinensis, Alnus hirsuta and Populus maximowiczii <30 cm dbh) were distributed on the lower terrace along the active river channel, while large-sized subpopulations (dbh 60 cm) of Quercus crispula and Ulumus davidiana var. japonica occurred on the higher terrace. The Phellodendron amurense population also occurred on the higher terrace in small clumps though the trees were small (less than 55 cm dbh). Subpopulations of intermediate-sized individuals (30 dbh < 60 cm) of Q. crispula and U. davidiana var. japonica, together with Betula and Acer spp. populations occurred on the intermediate terrace. Dendrochronological analyses indicated that the large and intermediate-sized tree groups were established about 330 and 90 years ago, respectively, while the small-sized tree group established about 35 years ago. A survey of historical disturbances showed that these periods of establishment of the former two groups almost coincided with the historically major floods occurring in 1662 and 1902. However, the disturbance that resulted in the establishment of the youngest group could not be precisely identified. Thus, the forest is a mosaic of three differently-aged patches, which is closely related to the frequency and scale of riparian disturbances. Longevity of trees and the preferred conditions for seed germination and/or seedling establishment were particularly important for the guild structure in this forest community.     

Diversity,structure and dynamics of a gallery forest in central Brazil

The structure and dynamics of approximately 64 ha of undisturbed gallery forest were studied over six years. Trees from 31 cm gbh (c. 10 cm dbh) were measured every three years from 1985. They were in 151 (10×20 m) permanent plots in the Gama forest in the Federal District of Brazil. Natural regeneration (individuals under 31 cm gbh) was measured in subplots (of 2×2 m, 5×5 m and 10×10 m) within the 200 m² plots. The total tree flora (gbh31 cm) consisted of 93 species, 81 genera and 44 families in 1985. The Leguminosae, Myrtaceae and Rubiaceae were the families richest in number of species. Most individuals and species were under 45 cm diameter and 20 m high while the maximum diameter per species ranged from 30 to 95 cm. The density structure of trees and natural regeneration was similar, in which the densities of c. 80% of the species represented less than 1% of the total density. The periodic mean annual diameter increment for trees from 10 cm dbh, was c. 0.25 cm/year. Variability was high with coefficients of variation c. 100% or more. The Gama community may maintain tree diversity and structure in undisturbed conditions. Regeneration of c. 80% of the species was found in the establishing phase (poles); the diameter structure was typical of native forests with the number of individuals decreasing with increasing size classes and showing little change over the six years; recruitment compensated for the mortality of most of the abundant species. The soils in Gama gallery forest were dystrophic with high aluminium content. Multivariate analysis suggested the stream, natural gaps and edges as the main causes of floristic differentiation at the community level.     

Integrated archaeobotanical research into vegetation management and land use in El Llano de la Horca (Santorcaz, Madrid, central Spain)

This paper presents an integrated archaeobotanical analysis carried out at the site known as “El Llano de la Horca”, a Bronze and Late Iron Age (3rd–1st century b.c.) Carpetanian settlement in central Spain (3600?±?80 b.p.). Pollen and spore analysis indicates an open landscape dominated by the herb taxa Asteraceae, Chenopodiaceae and Poaceae with an important representation of Glomus. The combination of pollen and charcoal studies also reveals the presence of Pinus sylvestris-nigra, P. pinaster-pinea, Juniperus thurifera, Quercus faginea, Q. ilex and Q. suber as the main trees used. Occurrences of Alnus, Corylus, Fraxinus and Juglans suggest the existence of water courses nearby. The archaeobotanical data is correlated with the geographical setting and archaeological context. The evolution of settlement patterns in central Spain, as well as the economy of other Carpetanian sites, is also considered to evaluate how this territory was managed for its vegetational resources since the Bronze Age (BA). Changes are expected as a consequence of different socio-economic factors at this site, especially when the settlement became an important Carpetanian oppidum. The combined results demonstrate a subsistence system based on cereal agriculture, in which naked wheat was dominant, together with some hulled barley and some erratic occurrences of hulled wheat. Furthermore, livestock breeding and metalwork activities seem to have resulted in a significant loss of woodland in order to clear land for crop fields and cattle grazing to cope with the needs of the growing Carpetanian community.     

Spinner dolphins in a remote Hawaiian atoll: social grouping and population structure

Spinner dolphins (Stenella longirostris) commonly use inshoreisland and atoll habitats for daytime rest and social interactionsand forage over deep waters at night. In Hawaii, they occurthroughout the archipelago. We applied photoidentification mark-recapturetechniques to study the population structure of spinner dolphinsassociated with remote Midway Atoll, far-western Hawaii. AtMidway, spinner dolphins live in stable bisexually bonded societiesof long-term associates, with strong geographic fidelity, noobvious fission-fusion, and limited contacts with other populations.Their large cohesive groups change little over time and arebehaviorally/socially discrete from other spinner dolphin groups.This social pattern differs considerably from the fluid fission-fusionmodel proposed previously for spinner dolphins associated witha large island habitat in the main Hawaiian Archipelago. Thesedifferences correspond to geographic separation and habitatvariation. While in the main islands there are several daytimeresting places available at each island habitat; in far-westernHawaii, areas of suitable habitat are limited and separatedby large stretches of open pelagic waters with potentially highrisk of shark predation. We hypothesize that with deepwaterfood resources in close proximity and other atolls relativelyfar away for easy (day-to-day) access, it is energetically morebeneficial in the remote Hawaiian atolls to remain "at home"than to travel to other atolls, so there is stability insteadof variability; there is no fission-fusion effect. Thus, thegeographic isolation and small size of remote atolls triggera process in which the fluidity of the fission-fusion spinnerdolphin society is replaced with long-term group fidelity andsocial stability.     

Carryover effects associated with winter location affect fitness, social status, and population dynamics in a long-distance migrant

We used observations of individually marked female black brant geese (Branta bernicla nigricans; brant) at three wintering lagoons on the Pacific coast of Baja California-Laguna San Ignacio (LSI), Laguna Ojo de Liebre (LOL), and Bahía San Quintín (BSQ)-and the Tutakoke River breeding colony in Alaska to assess hypotheses about carryover effects on breeding and distribution of individuals among wintering areas. We estimated transition probabilities from wintering locations to breeding and nonbreeding by using multistratum robust-design capture-mark-recapture models. We also examined the effect of breeding on migration to wintering areas to assess the hypothesis that individuals in family groups occupied higher-quality wintering locations. We used 4,538 unique female brant in our analysis of the relationship between winter location and breeding probability. All competitive models of breeding probability contained additive effects of wintering location and the 1997-1998 El Ni?o-Southern Oscillation (ENSO) event on probability of breeding. Probability of breeding in non-ENSO years was [Formula: see text], [Formula: see text], and [Formula: see text] for females wintering at BSQ, LOL, and LSI, respectively. After the 1997-1998 ENSO event, breeding probability was between 2% (BSQ) and 38% (LOL) lower than in other years. Individuals that bred had the highest probability of migrating the next fall to the wintering area producing the highest probability of breeding.     

A study on the social structure and dispersal patterns of hamadryas baboons living in a commensal group at Taif,Saudi Arabia

Three levels of hamadryas social structure—the one male unit (OMU), the band, and the troop—have been observed at all sites studied, but a fourth—the clan—has been observed at only one site, Erer-Gota, Ethiopia, during a longitudinal check of the dispersion of identified individuals. The clan is important since it appears to provide the basis for male philopatry, although comparative data is needed from other sites to confirm this. We studied a huge commensal group of hamadryas baboons (over 600 animals) in Saudi Arabia. We put ear tags on baboons between 1998 and 2004 and analyzed social structure, relying on the interactions of these tagged animals by focusing especially on their dispersal patterns from OMUs. OMU membership tended to be looser than that of the Ethiopian hamadryas. Females tended to shift between OMUs on an individual basis in our study group, whereas the collapse of an OMU was a major occasion of adult female transfer in Ethiopia. We found neither stable bands (a “band” in our study group was defined as a regional assemblage of OMUs) nor clans that lasted for several years. Some OMUs moved and transferred into neighboring areas over both the short and long term. Further, some post-adolescent males appeared to move out of the study area. The ratio of adult females in an OMU in our study group was larger than for any other documented study site, and this may be the reason for enhanced female transfer between OMUs. A large proportion of the adolescent females showed no clear membership to OMUs, and no “initial units” (commonly observed in Ethiopia) were discernible. The ease with which young males acquired adult females at the study site must have disrupted the formation of a clan, a “male-bonded society.”