A metapopulation model of social group dynamics and disease applied to Yellowstone wolves

The population structure of social species has important consequences for both their demography and transmission of their pathogens. We develop a metapopulation model that tracks two key components of a species’ social system: average group size and number of groups within a population. While the model is general, we parameterize it to mimic the dynamics of the Yellowstone wolf population and two associated pathogens: sarcoptic mange and canine distemper. In the initial absence of disease, we show that group size is mainly determined by the birth and death rates and the rates at which groups fission to form new groups. The total number of groups is determined by rates of fission and fusion, as well as environmental resources and rates of intergroup aggression. Incorporating pathogens into the models reduces the size of the host population, predominantly by reducing the number of social groups. Average group size responds in more subtle ways: infected groups decrease in size, but uninfected groups may increase when disease reduces the number of groups and thereby reduces intraspecific aggression. Our modeling approach allows for easy calculation of prevalence at multiple scales (within group, across groups, and population level), illustrating that aggregate population-level prevalence can be misleading for group-living species. The model structure is general, can be applied to other social species, and allows for a dynamic assessment of how pathogens can affect social structure and vice versa.

Adaptive Trial Designs in Rheumatology: Report from the OMERACT Special Interest Group

Objective.Adaptive trial design was developed initially for oncology to improve trial efficiency. If optimized for rheumatology, it may improve trial efficiency by reducing sample size and time.Methods.A systematic review assessed design of phase II clinical trials in rheumatoid arthritis.Results.Fifty-six trials were reviewed. Most trials had 4 groups (1 control and 3 intervention), with an average group size of 34 patients. American College of Rheumatology 20 measured at 16 weeks was the most commonly used primary endpoint.Conclusion.The next step is to undertake a systematic review of adaptive designs used in early-phase trials in nonrheumatic conditions.

Group size in social-ecological systems

Cooperation becomes more difficult as a group becomes larger, but it is unclear where it will break down. Here, we study group size within well-functioning social-ecological systems. We consider centuries-old evidence from hundreds of communities in the Alps that harvested common property resources. Results show that the average group size remained remarkably stable over about six centuries, in contrast to a general increase in the regional population. The population more than doubled, but although single groups experienced fluctuations over time, the average group size remained stable. Ecological factors, such as managing forest instead of pasture land, played a minor role in determining group size. The evidence instead indicates that factors related to social interactions had a significant role in determining group size. We discuss possible interpretations of the findings based on constraints in individual cognition and obstacles in collective decision making.

Group size constraints may mask underlying similarities in social structure: a comparison of female elephant societies

We report on female Asian elephant social structure in Nagarahole and Bandipur National Parks (Kabini population), southern India, and examine the role of group size in affecting the outcome of social structure analysis in female elephants, which show high fission-fusion dynamics. Based on five years of data, we found the Kabini association network structured into highly modular communities that we call clans. We then modified the dataset (to obtain the Kabini 500-m dataset) to match sampling methods previously used in a study each of Asian (Uda Walawe) and African savannah (Samburu) elephants, so that network and association statistics could be compared across populations. Measures of association and network structure previously used were more similar amongst the Asian elephant populations compared to Samburu. The Samburu population formed a hierarchically-nested multilevel society whereas the Asian populations did not. However, we found hierarchical clustering levels in all three populations using Louvain community detection. Moreover, the average community sizes obtained through the Louvain method were not significantly different across populations, indicating basic similarities in social structure. Since fission-fusion dynamics allow for community members to form groups of different sizes, we examined the effect of average group size on association and network statistics. Higher average association index and degree, and lower average path length in Samburu compared to the Kabini 500-m dataset were explained by the larger average group size in Samburu. Thus, underlying similarities in the social networks of species showing fission-fusion dynamics may be obscured by differences in average group size.Significance StatementVarious measures of associations and social network analyses have been used to compare social structures of different populations. We studied the social structure of female Asian elephants in a southern Indian population and compared it with those of a Sri Lankan Asian elephant population and an African savannah elephant population. We showed that, while there were social differences between the Asian and African savannah elephant populations using previous methods, there were basic similarities across all three populations using a method of network community detection. This discrepancy across analyses partly stemmed from differences in average group size between populations. Average group size in fission-fusion societies variously affected different association and network statistics, which has implications for inferences about social structure.

Population status, distribution and potential threats of the Blue Bull Boselaphus tragocamelus (Mammalia: Cetartiodactyla: Bovidae) along the Tinau River of Rupandehi District, Nepal

The status and conservation of the Blue Bull Boselaphus tragocamelus is becoming one of the prominent discourses of wildlife research. The study was carried out along the Tinau River at Rupandehi District in western Nepal to ascertain the population status, distribution and potential threats to the Blue Bull. The study was conducted along six transect lines in the forest. A total of 40 Blue Bulls were recorded in different transects. The average group size was five. The average population density was 0.228 Blue Bulls per ha and the sex ratio was 1 male: 3 females. The potential threats of the Blue Bull along the Tinau River were habitat destruction, overgrazing, conflict, flooding and accident.

Further evidence of a context-specific agonistic signal in bottlenose dolphins: the influence of consortships and group size on the pop vocalization

Pops are a low-frequency, pulsed vocalization produced by Indo-Pacific bottlenose dolphins (Tursiopscf.aduncus) in Shark Bay, Western Australia and are often heard when male alliances are consorting or ‘herding’ a female. Previous research indicated that pops produced in this context are an agonistic ‘come-hither’ demand produced by males and directed at female consorts. Here we examine pop occurrence during focal follows on bottlenose dolphin alliances with and without female consorts present. Regression analysis was conducted to determine if pop numbers were higher in the presence of female consorts, and if variables including group size alone and the interaction between presence/absence of a consortship and group size, influenced pop production. While the presence or absence of a consortship significantly affected the number of pops, average group size had no significant effect on pop production. Our research provides further evidence that the pop vocalization plays an important role in consortships.

Status of blue sheep and Himalayan tahr in Dhorpatan Hunting Reserve, Nepal

A survey of blue sheep (Pseudois nayaur) was conducted in six blocks of Dhorpatan Hunting Reserve (DHR), Nepal. A total of 852 blue sheep were recorded in 73 different groups. The average group size was found to be 11.7 individuals. The average population density of blue sheep in the reserve was found to be 1.28 animals per km2. There were 263 rams, 307 ewes, 89 yearlings and 39 lambs. Among the rams, 126 were classified as trophy rams, 92 as medium rams and 45 as young rams. The ratio of trophy rams to other rams was found to be higher than those found in the earlier studies. The mean sex ratio was 86 males per 100 females and the yearling to ewes ratio was 29 per 100 ewes. The survey of Himalayan tahr (Hemitragus jemlahicus) in Sundaha block recorded 53 individuals with 30 males, 14 females, eight yearlings, and one lamb. The results indicated that the existing quota of blue sheep hunting can be safely continued. In case of higher demands, two more quotas can be added to Barse, Dogadi and Sundaha blocks for the next five years (2008-2012). Himalayan tahrs can be hunted in all the blocks. Sundaha block can sustain four while the rest of the blocks can sustain two Himalayan tahrs per year. DOI: http://dx.doi.org/10.3126/banko.v21i1.9060 Banko Janakari, Vol. 21, No. 1 2011; 25-30

Spatial distribution and activities of the estuarine dolphin Sotalia guianensis (van Bénédén, 1864) (Cetacea, Delphinidae) in Pontal Bay, Ilhéus, Bahia, Brazil

We analyzed the influence of time, tide and water depth on the activity and spatial distribution of estuarine dolphins Sotalia guianensis in Pontal Bay, Ilhéus, Brazil. Direct observations were carried out at four fixed points from January to December of 2006. Estuarine dolphins were sighted in 11 out of 12 months and in 30% of 181 sampling periods. The average group size, which was 3.75 ± 1.59 (n = 64), did not vary significantly by month (Kruskal-Wallis, H = 10.6729; p = 0.3836). Infants and adults represented 18 and 82% of the individuals whose age we were able to determine, respectively. Estuarine dolphins were more frequently present than expected in areas deeper than 3 m (regression GLM, z = 3.773; p = 0.0002). The animals were more frequently observed between 7:00 and 8:00 AM and between 3:00 and 5:00 PM (X² = 83.815; p < 0.0001). Their presence in the bay tripled between the fourth hour of the flood and high tide, remaining elevated during the ebb tide (X² = 22.152; p = 0.02). The tide also influenced the animals' feeding and travelling direction, mainly toward the open see during the flood and to the back of the bay during others stages. Further studies are necessary to analyze the influence of the hydrographic characteristics of Pontal Bay on the spatio-temporal distribution of estuarine dolphins and their prey.

Relationship between group size and feeding success of cattle egrets (Bubulcus ibis) in the central Free State

Regardless of habitat or time of day, cattle egrets feeding independently of hosts generally occurring larger groups than those feeding in close association with ungulates. The average group size of three individuals feeding in association with hosts stays remarkably constant with regard to divergent situations. Based on the type of habitat and the grazing speed of the host concerned, cattle egrets achieve the highest feeding success (number of prey items) with the least energy inputs (number of paces) in association with cattle, and to a lesser extent with the closely related buffalo. Compared to solitary birds, cattle egrets feeding in groups experience without exceptional higher feeding success. Results of feeding experiments, as well as the exceptional occurrence of so-called feeding lines, confirm the phenomenon that the feeding success of cattle egrets correlates closely with the size of the feeding group.

Social and Play Behavior in a Wild Eastern Coyote, Canis latrans, Pack

I had close and consistent observations of a wild eastern Coyote pack (Canis latrans) from January 2000 to August 2007. During this time, I obtained 3156 radio-locations on a specific radio-collared breeding male (“Sill”) and observed him and/or members of his pack on 375 occasions. The average group size = 3.0 ± 2.3 (SD) Coyotes with 1.9 ± 1.2 (SD) being adults and 1.1 ± 1.9 being pups. Maximal group size involved 12 Coyotes (9 pups, 3 adults). During these observations, Coyotes most often behaved in a friendly manner toward each other as indicated by 80 of my observations involving play between pups, and 15 involving play among adult Coyotes. On the evening of 6 July 2007 I observed the breeding male (>8 yr old), his mate (>5 yr old), one of their full-sized probable yearlings, and five pups playing intensely for 33 minutes. This paper details social and play behavior from this pack, especially from the 6 July 2007 observation.