Body size of large herbivores is a crucial life history variable influencing individual fitness‐related traits. While the importance of this parameter in determining temporal trends in population dynamics is well established, much less information is available on spatial variation in body size at a local infra‐population scale. The relatively recent increase in landscape fragmentation over the last century has lead to substantial spatial heterogeneity in habitat quality across much of the modern agricultural landscape. In this paper, we analyse variation in body mass and size of roe deer inhabiting a heterogeneous agricultural landscape characterised by a variable degree of woodland fragmentation. We predicted that body mass should vary in relation to the degree of access to cultivated meadows and crops providing high quality diet supplements. In support of our prediction, roe deer body mass increased along a gradient of habitat fragmentation, with the heaviest deer occurring in the most open sectors and the lightest in the strict forest environment. These spatial differences were particularly pronounced for juveniles, reaching >3 kg (ca 20% of total body mass) between the two extremes of this gradient, and likely have a marked impact on individual fates. We also found that levels of both nitrogen and phosphorous were higher in deer faecal samples in the more open sectors compared to the forest environment, suggesting that the spatial patterns in body mass could be linked to the availability of high quality feeding habitat provided by the cultivated agricultural plain. Finally, we found that adults in the forest sector were ca 1 kg lighter for a given body size than their counterparts in the more open sectors, suggesting that access to nutrient rich foods allowed deer to accumulate substantial fat reserves, which is unusual for roe deer, with likely knock‐on effects for demographic traits and, hence, population dynamics.
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Most forests in Europe are patchily distributed within the agricultural landscape. Therefore, forest biogeochemistry in Europe cannot be understood without considering the connectivity of nutrient cycles between forest patches and fertilized cropland. In this paper, we quantified the role of roe deer, the most widespread wild ungulate in Europe, as a vector of nitrogen and phosphorus from fertilized fields to forest patches, in a typical agricultural landscape of southwestern Europe. We derived a model of nutrient transfer from a data set on deer density, landscape‐use by individual deer, and nutrient content in feces. The model shows that the magnitude of nutrient transfer is highly sensitive to the proportion of forest patches within the landscape, and to the way deer use the landscape to feed and defecate. Hence, the magnitude of nutrient transfer varies substantially across the landscape. Locally, deer may significantly fertilize the forest, transferring the equivalent of almost 20% of the atmospheric deposition of nitrogen, and the equivalent of 0.13% of the total stock of phosphorus from cropland to forest patches each year. These inputs may markedly influence the biogeochemistry of forests in the long run, and the nitrogen to phosphorus ratio available to trees and forest plants. These results highlight the significant, but, heterogeneous, role of wild ungulates in forest biogeochemistry across Europe.
Dispersal is a key process in metapopulation dynamics as it conditions species’ spatial responses to gradients of abiotic and biotic conditions and triggers individual and gene flows. In the numerous plants that are dispersed through seed consumption by herbivores (endozoochory), the distance and effectiveness of dispersal is determined by the combined effects of seed retention time in the vector’s digestive system, the spatial extent of its movements, and the ability of the seeds to germinate once released. Estimating these three parameters from experimental data is therefore crucial to calibrate mechanistic metacommunity models of plant–herbivore interactions. In this study, we jointly estimated the retention time and germination probability of six herbaceous plants transported by roe deer (Capreolus capreolus), red deer (Cervus elaphus), and wild boar (Sus scrofa) through feeding experiments and a Bayesian dynamic model. Retention time was longer in the nonruminant wild boar (>36 h) than in the two ruminant species (roe deer: 18–36 h, red deer: 3–36 h). In the two ruminants, but not in wild boar, small and round seeds were excreted faster than large ones. Low germination probabilities of the excreted seeds reflected the high cost imposed by endozoochory on plant survival. Trait-mediated variations in retention time and germination probability among animal and plant species may impact plant dispersal distances and interact with biotic and abiotic conditions at the release site to shape the spatial patterns of dispersed plant species.
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