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523 results for “Sheep”

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dryad36/100

Different proxies, different stories? Imperfect correlations and different determinants of fitness in bighorn sheep

Measuring individual fitness empirically is required to assess selective pressures and predict evolutionary changes in nature. There is, however, little consensus on how fitness should be empirically estimated. As fitness proxies vary in their underlying assumptions, their relative sensitivity to individual, environmental, and demographic factors may also vary. Here, using a long-term study, we aimed at identifying the determinants of individual fitness in bighorn sheep (Ovis canadensis) using seven fitness proxies. Specifically, we compared four-lifetime fitness proxies: lifetime breeding success, lifetime reproductive success, individual growth rate, and individual contribution to population growth, and three multi-generational proxies: number of granddaughters, individual descendance in the next generation, and relative genetic contribution to the next generation. We found that all proxies were positively correlated, but the magnitude of the correlations varied substantially. Longevity was the main determinant of most fitness proxies. Individual fitness calculated over more than one generation was also affected by population density and growth rate. Because they are affected by contrasting factors, our study suggests that different fitness proxies should not be used interchangeably as they may convey different information about selective pressures and lead to divergent evolutionary predictions. Uncovering the mechanisms underlying variation in individual fitness and improving our ability to predict evolutionary change might require the use of several, rather than one, proxy of individual fitness.

opencc-zeroDec 2022View details →

dryad36/100

Data from: Population connectivity patterns of genetic diversity, immune responses and exposure to infectious pneumonia in a metapopulation of desert bighorn sheep

Habitat fragmentation is an important driver of biodiversity loss and can be remediated through management actions aimed at maintenance of natural connectivity in metapopulations. Connectivity may protect populations from infectious diseases by preserving immunogenetic diversity and disease resistance. However, connectivity could exacerbate the risk of infectious disease spread across vulnerable populations. We tracked the spread of a novel strain of Mycoplasma ovipneumoniae in a metapopulation of desert bighorn sheep (Ovis canadensis nelsoni) in the Mojave desert to investigate how variation in connectivity among populations influenced disease outcomes. M. ovipneumoniae was detected throughout the metapopulation, indicating that the relative isolation of many of these populations did not protect them from pathogen invasion. However, we show that connectivity among bighorn sheep populations was correlated with higher immunogenetic diversity, a protective immune response and lower disease prevalence. Variation in protective immunity predicted infection risk in individual bighorn sheep and was associated with heterozygosity at genetic loci linked to adaptive and innate immune signalling. Together, these findings may indicate that population connectivity maintains immunogenetic diversity in bighorn sheep populations in this system and has direct effects on immune responses in individual bighorn sheep and their susceptibility to infection by a deadly pathogen. Our study suggests that the genetic benefits of population connectivity could outweigh the risk of infectious disease spread and supports conservation management that maintains natural connectivity in metapopulations.

opencc-zeroJan 2023View details →

dryad36/100

Correlates of early reproduction and apparent fitness consequences in male Soay sheep

Life history trade-offs are ubiquitous across species and place constraints on the timing of life history events, including the optimal age at first reproduction. However, studies on lifetime breeding success of male mammals are rare due to sex-biased dispersal and the requirement for genetic paternity inferences. We studied the correlates and apparent fitness consequences of early-life reproduction among males in a free-living population of Soay sheep (Ovis aries) on St Kilda, Scotland. We investigated the factors associated with early breeding success and the apparent consequences of early success for survival and future reproduction. We used genetic paternity inferences, population data and individual morphology measurements collected over 30 years. We found that individuals born in years with low-density population size had the highest early-life breeding success, and singletons were more likely to be successful than twins. Individuals that bred successfully at seven months were more likely to survive their first winter. For individuals that survived their first winter, early breeding success was not associated with later breeding success. Since individual heterogeneity affects breeding success, we believe that variation in individual quality masks costs of early reproduction in this population. Our findings provide no evidence for selection for delayed age at reproduction in male Soay sheep.

opencc-zeroApr 2023View details →

dryad36/100

Individual-plant selectivity by sheep in drylands scales-up at plant population level and controls the forage supply and its accessibility

Diet selectivity by domestic herbivores controls plant community structure and dynamics and may induce rangeland degradation, particularly in drylands. However, management decisions frequently ignore herbivore selectivity. Here, we studied how grass morphology controls sheep selectivity for individual plants, and how this selectivity interacts with grazing intensity to determine population plant-size distributions and the forage supply. In Patagonian steppes, we manipulated the plant morphology (size and standing-dead proportion) of three dominant grass species differentially preferred by sheep for four years. Then, we evaluated how these morphological alterations affected intra- and inter-specific preference patterns. We also evaluated how grazing intensity (ungrazed, moderate grazing, and intensive grazing) affected the plant-size distribution of the three species, the forage supply, and its accessibility. For the highly preferred species, herbivores selected plants that were either naturally or experimentally short, with low proportion of standing-dead biomass. In contrast, morphological changes did not alter the within-species selectivity of the least preferred species. Grazing intensity strongly changed the population plant-size distribution of preferred species in ways that resembled the experimental manipulations of morphology. Moderate grazing showed the greatest morphological heterogeneity among individuals. When integrating the green biomass of forage species' individuals at ecosystem level, we found that the forage supply was the highest in ungrazed sites and decreased as grazing intensity increased. However, considering the dissuading effect of the standing-dead proportion of plants, the accessible forage was the highest under moderate grazing. Synthesis and applications. Our findings (i) showed that, within preferred species, sheep selectivity at individual-plant level is controlled by morphological characteristics that determine accessibility to green high-quality biomass. This effect was as important as that of species identity; (ii) empirically proved plant-animal positive feedback at individual level; and (iii) revealed how the individual-plant selectivity scales-up at population level and controls the forage supply, but also its accessibility. Our complementary approach generates critical knowledge for developing management practices to control key forage species defoliation and to adjust the grazing pressure to the offer of accessible forage, avoiding the common carrying capacity overestimation. These aspects are essential for sustainable production in grazed drylands.

opencc-zeroMay 2023View details →

dryad36/100

Data from: Fission-fusion dynamics in sheep: The influence of resource distribution and temporal activity patterns

Fission-fusion events, i.e. changes to the size and composition of animal social groups, are a mechanism to adjust the social environment in response to short-term changes in the cost-benefit ratio of group living. Furthermore, the time and location of fission-fusion events provide insight into the underlying drivers of these dynamics. Here, we describe a method for identifying group membership over time and for extracting fission-fusion events from animal tracking data. We applied this method to high-resolution GPS data of free-ranging sheep (Ovis aries). Group size was highest during times when sheep typically rest (mid-day and at night), and when anti-predator benefits of grouping are high while costs of competition are low. Consistent with this, fission and fusion frequencies were highest during early morning and late evening, suggesting that social restructuring occurs during periods of high activity. However, fission and fusion events were not more frequent near food patches and water resources when adjusted for overall space use. This suggests a limited role of resource competition. Our results elucidate the dynamics of grouping in response to social and ecological drivers, and we provide a tool for investigating these dynamics in other species.

opencc-zeroJul 2023View details →

dryad36/100

Supplementary material from: ZooMS confirms geometric morphometrics species identification of ancient sheep and goat

Geometric morphometrics can effectively distinguish isolated third lower molars of present-day sheep and goat, but its applicability to archaeological specimens has yet to be established. Using a modern reference collection of 743 sheep and goats and a 2D-landmark-based geometric morphometric (GMM) protocol, this study aimed to morphometrically identify 109 archaeological specimens, used as case studies, dating from the Late Neolithic to the modern period/era. These morphometric identifications were then compared to molecular identifications via collagen peptide mass fingerprinting, known as Zooarcheology by Mass Spectrometry (ZooMS). ZooMS confirmed the morphometric identifications for 104 specimens, with the five misidentified specimens all morphometrically identified as goat. Modern sheep and goats have larger teeth and distinct shapes compared to their archaeological counterparts, suggesting strong differences between archaeological and modern specimens potentially linked with recent breed improvement or geographic origin of the specimens. In addition, for both species, some of the archaeological dental morphologies do not match with any of our modern references. This study validates the applicability of geometric morphometrics for identifying isolated archaeological sheep and goat teeth. It represents a stepping stone for future, non-destructive, bioarchaeological studies of the two species.

opencc-zeroDec 2022View details →

zenodo36/100

Textiles: Lynyaev, "Wolves and Sheep"

The 3D model presents a digital reconstruction of historical textile materials for a theatrical costume for Mikhail Lynyaev in the play "Wolves and Sheep" (1875) by A.N. Ostrovsky. The authors used 2D scanning to capture the look of the surfaces, post processed the images in PixPlant, generated texture maps in Photoshop and put those on the 3D models in SubstancePainter. The authors of the 3D model are Aleksei Moskvin and Mariia Moskvina (Saint Petersburg State University of Industrial Technologies and Design). The authors thank prof. Victor Kuzmichev (Ivanovo State Polytechnic University) for providing data required for digitization of textiles. The actual costume that can be seen in the photo was made by faculty members and students of Ivanovo State Polytechnic University. Please contact us if you require seamless textures. The cloth 3D model by atomov is available at Turbosquid. DOI: 10.13140/RG.2.2.33377.99681 Source: Objaverse 1.0 / Sketchfab

opencc-byAug 2022View details →

dryad36/100