The effect of age, environment and management on social contact patterns in sheep

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordSocial structures of group-living farm animals can have important implications for animal welfare and productivity. Understanding which factors can have an effect on social behaviour is thus important in order to develop the best management strategies in livestock industries. Here, we studied the social network structure of a flock of 84 Poll Dorset ewes and collecting dyadic associations data through the use of proximity sensors during two study periods. First, we analysed the social structure of ewes at a group-level, by analysing the community structure, and at individual-level, by determining whether the ewes showed social differentiation in their association patterns. Second, we measured for the contribution of genetic relatedness, age, weight, reproductive status and previous management sub grouping on social associations to test for homophily effects. Lastly, we evaluated whether social clustering was influenced by the stocking density of individuals in a field, and by weather parameters, through the use of two climatic indices, the Temperature-Humidity Index (THI) and the Wind Chill Index (WCI). Our results showed that the pairwise associations between ewes are not-random and highly heterogeneous, both in total time spent in contact and in contacts duration. There was no evidence that ewes were subdivided into social communities, and at individual level, they showed markedly differentiated social relationships, demonstrating preferences in social ties. However, the factors that influenced the preferred social interactions between individuals changed over time. In the first study period ewes tended to maintain the social bonds formed in previous management sub grouping, most likely due to a social familiarization resulting from repeated interactions with the same individuals. In the second study period similarity in age influenced the strength of associations among ewes. We found no significant influence of reproductive status, weight (as an indicator of body size) and genetic relatedness on proximity associations in either study period. Moreover, our results showed the tendency of the ewes to form social clusters varied in relation to animals’ density, and Wind Chill Index (WCI). The identification of conditions that modify the social behaviour of sheep is critically important in order to implement management and productivity strategies and our results highlight how flock social structure can change depending on environmental and social contextsBiotechnology & Biological Sciences Research Council (BBSRC

Association networks and social temporal dynamics in ewes and lambs

This is the final version. Available on open access from Elsevier via the DOI in this recordSheep are highly social domesticated animals that evolved to live in large and structured groups. As in other group-living species, individuals differ in the level of association they have with others, and these associations often result in lasting and stable social bonds. However, there are substantial gaps in our knowledge of the temporal social dynamics in sheep, and how their social bonds vary in relation to environmental changes. Here, we aimed to assess the social relationships between ewes and lambs, collecting dyadic associations data of 41 ewes and 55 lambs through the use of proximity loggers on a commercial farm. We computed association indices between each pair of animals to estimate the proportion of time any two individuals associated. We first generated an aggregated network of the whole 13-day observation period, and we compared the values of association indices between different types of dyads (i.e., lamb-mother, lamb-ewe non-mother, lambs littermates, lambs non-littermates, ewe-ewe). We generated aggregated contact networks on a daily scale to compare the ego-networks of individuals obtained in successive time windows to determine how stable social associations were over time. As would be expected, the highest values of association indices were found in dyads formed by dams and lambs (0.17±0.11) and by lambs of the same litter (0.32±0.09). Both single-born and twin-born lambs showed high association values with their dams (single-born: 0.24±0.11; twin-born: 0.1±0.05), although twin-born lambs had stronger associations with their littermates compared with those with their mothers (p-value < 0.001). At a temporal level, the flock exhibited periods of high network stability at the beginning and at the end of the study period. However, periods of social instability occurred one-two days after management interventions, such as changes in field size. These transitory periods of social instability were driven by changes in the association patterns of ewes and single born lambs. In contrast, the ego-networks of twin-born lambs remained relatively stable, supported by strong association levels between twins. Thus, the social instability of the social network was not a global one, but some parts of the network remained stable while others underwent important changes. Our study represents a first step to track social associations within an ewe-lamb group using proximity tags and advances our understanding of the social organisation of sheep. We highlight the importance of detecting social network instability as a consequence of different types of perturbations in order to identify the presence of social rearrangements.Biotechnology & Biological Sciences Research Council (BBSRC)CRT Foundatio

High-resolution contact networks of free-ranging domestic dogs Canis familiaris and implications for transmission of infection

This is the final version. Available on open access from Public Library of Science via the DOI in this recordData Availability: All data and code supporting these analyses are available on Dryad doi:10.5061/dryad.7v62484.Contact patterns strongly influence the dynamics of disease transmission in both human and non-human animal populations. Domestic dogs Canis familiaris are a social species and are a reservoir for several zoonotic infections, yet few studies have empirically determined contact patterns within dog populations. Using high-resolution proximity logging technology, we characterised the contact networks of free-ranging domestic dogs from two settlements (n = 108 dogs, covering >80 % of the population in each settlement) in rural Chad. We used these data to simulate the transmission of an infection comparable to rabies and investigated the effects of including observed contact heterogeneities on epidemic outcomes. We found that dog contact networks displayed considerable heterogeneity, particularly in the duration of contacts and that the network had communities that were highly correlated with household membership. Simulations using observed contact networks had smaller epidemic sizes than those that assumed random mixing, demonstrating the unsuitability of homogenous mixing models in predicting epidemic outcomes. When contact heterogeneities were included in simulations, the network position of the individual initially infected had an important effect on epidemic outcomes. The risk of an epidemic occurring was best predicted by the initially infected individual’s ranked degree, while epidemic size was best predicted by the individual’s ranked eigenvector centrality. For dogs in one settlement, we found that ranked eigenvector centrality was correlated with range size. Our results demonstrate that observed heterogeneities in contacts are important for the prediction of epidemiological outcomes in free-ranging domestic dogs. We show that individuals presenting a higher risk for disease transmission can be identified by their network position and provide evidence that observable traits hold potential for informing targeted disease management strategies.Carter Cente

Spatial and temporal variation in proximity networks of commercial dairy cattle in Great Britain

This is the final version. Available on open access from Elsevier via the DOI in this recordThe nature of contacts between hosts can be important in facilitating or impeding the spread of pathogens within a population. Networks constructed from contacts between hosts allow examination of how individual variation might influence the spread of infections. Studying the contact networks of livestock species managed under different conditions can additionally provide insight into their influence on these contact structures. We collected high-resolution proximity and GPS location data from nine groups of domestic cattle (mean group size = 85) in seven dairy herds employing a range of grazing and housing regimes. Networks were constructed from cattle contacts (defined by proximity) aggregated by different temporal windows (2 h, 24 h, and approximately 1 week) and by location within the farm. Networks of contacts aggregated over the whole study were highly saturated but dividing contacts by space and time revealed substantial variation in cattle interactions. Cows showed statistically significant variation in the frequency of their contacts and in the number of cows with which they were in contact. When cows were in buildings, compared to being on pasture, contact durations were longer and cows contacted more other cows. A small number of cows showed evidence of consistent relationships but the majority of cattle did not. In one group where management allowed free access to all farm areas, cows showed asynchronous space use and, while at pasture, contacted fewer other cows and showed substantially greater between-individual variation in contacts than other groups. We highlight the degree to which variations in management (e.g. grazing access, milking routine) substantially alter cattle contact patterns, with potentially major implications for infection transmission and social interactions. In particular, where individual cows have free choice of their environment, the resulting contact networks may have a less-risky structure that could reduce the likelihood of direct transmission of infections.Biotechnology and Biological Sciences Research Council (BBSRC)Animal and Plant Health AgencyFondazione CR