Adaptive Lévy Walks in Foraging Fallow Deer

Background: Lévy flights are random walks, the step lengths of which come from probability distributions with heavy power-law tails, such that clusters of short steps are connected by rare long steps. Lévy walks maximise search efficiency of mobile foragers. Recently, several studies raised some concerns about the reliability of the statistical analysis used in previous analyses. Further, it is unclear whether Lévy walks represent adaptive strategies or emergent properties determined by the interaction between foragers and resource distribution. Thus two fundamental questions still need to be addressed: the presence of Lévy walks in the wild and whether or not they represent a form of adaptive behaviour. Methodology/Principal Findings: We studied 235 paths of solitary and clustered (i.e. foraging in group) fallow deer (Dama dama), exploiting the same pasture. We used maximum likelihood estimation for discriminating between a power-tailed distribution and the exponential alternative and rank/frequency plots to discriminate between Lévy walks and composite Brownian walks. We showed that solitary deer perform Lévy searches, while clustered animals did not adopt that strategy. Conclusion/Significance: Our demonstration of the presence of Lévy walks is, at our knowledge, the first available which adopts up-to-date statistical methodologies in a terrestrial mammal. Comparing solitary and clustered deer, we concluded that the Lévy walks of solitary deer represent an adaptation maximising encounter rates with forage resources and not a

Words apart: Standardizing forestry terms and definitions across European biodiversity studies

Forest biodiversity studies conducted across Europe use a multitude of forestry terms, often inconsistently. This hinders the comparability across studies and makes the assessment of the impacts of forest management on biodiversity highly context-dependent. Recent attempts to standardize forestry and stand description terminology mostly used a top-down approach that did not account for the perspectives and approaches of forest biodiversity experts. This work aims to establish common standards for silvicultural and vegetation definitions, creating a shared conceptual framework for a consistent study on the effects of forest management on biodiversity. We have identified both strengths and weaknesses of the silvicultural and vegetation information provided in forest biodiversity studies. While quantitative data on forest biomass and dominant tree species are frequently included, information on silvicultural activities and vegetation composition is often lacking, shallow, or based on broad and heterogeneous classifications. We discuss the existing classifications and their use in European forest biodiversity studies through a novel bottom-up and top-driven review process, and ultimately propose a common framework. This will enhance the comparability of forest biodiversity studies in Europe, and puts the basis for effective implementation and monitoring of sustainable forest management policies. The standards here proposed are potentially adaptable and applicable to other geographical areas and could be extended to other forest interventions. Forest management Multi-taxon Terminology Silviculture Data harmonizationpublishedVersio

Step by step: reconstruction of terrestrial animal movement paths by dead-reckoning

Background: Research on wild animal ecology is increasingly employing GPS telemetry in order to determine animal movement. However, GPS systems record position intermittently, providing no information on latent position or track tortuosity. High frequency GPS have high power requirements, which necessitates large batteries (often effectively precluding their use on small animals) or reduced deployment duration. Dead-reckoning is an alternative approach which has the potential to ‘fill in the gaps’ between less resolute forms of telemetry without incurring the power costs. However, although this method has been used in aquatic environments, no explicit demonstration of terrestrial dead-reckoning has been presented.Results: We perform a simple validation experiment to assess the rate of error accumulation in terrestrial dead-reckoning. In addition, examples of successful implementation of dead-reckoning are given using data from the domestic dog Canus lupus, horse Equus ferus, cow Bos taurus and wild badger Meles meles.Conclusions: This study documents how terrestrial dead-reckoning can be undertaken, describing derivation of heading from tri-axial accelerometer and tri-axial magnetometer data, correction for hard and soft iron distortions on the magnetometer output, and presenting a novel correction procedure to marry dead-reckoned paths to ground-truthed positions. This study is the first explicit demonstration of terrestrial dead-reckoning, which provides a workable method of deriving the paths of animals on a step-by-step scale. The wider implications of this method for the understanding of animal movement ecology are discussed

Un équilibre forêt-cervidés en évolution permanente : la nécessité d'une gestion adaptative

National audienceL'équilibre forêt-cervidés, ou sylvo-cynégétique, est défini par le Code de l'environnement comme le fait de rendre compatibles, d'une part, la présence durable d'une faune sauvage riche et variée et, d'autre part, la pérennité et la rentabilité économique des activités sylvicoles. La traduction opérationnelle de cette notion a donné lieu à de nombreux débats ; la difficulté est l'intégration des différentes dimensions concernées : écologique, économique et humaine. Sur le plan écologique, la population animale et le milieu qu'elle utilise évoluent tous deux en interactions. L'ensemble de ces évolutions implique que le niveau d'équilibre forêt-cervidés va lui aussi fluctuer au cours du temps. Sur les plans économique et humain, la question de l'équilibre forêt-cervidés intéresse une grande diversité d'acteurs, dont les implications varient en fonction des enjeux locaux : chasseurs, forestiers, agriculteurs, naturalistes, élus locaux, utilisateurs de la forêt... Ces acteurs ont des profils et des préoccupations diverses. A cela s'ajoute une méconnaissance des activités ou contraintes des autres acteurs, qui complique les discussions avec ces personnes. Les constats précédents impliquent donc d'avoir une gestion de l'équilibre qui réponde à deux exigences : (a) permettre des ajustements réguliers selon les évolutions constatées sur le plan écologique, (b) reposer sur une concertation entre les acteurs concernés. Sur ce point, le modèle de la gestion adaptative remplit ces deux critères. D'une part, il prévoit une évaluation des effets des actions de gestion ; il permet ainsi d'apprendre des expériences passées et dans notre cas, de s'adapter aux évolutions du couple population-milieu. D'autre part, la gestion adaptative repose sur la collaboration et la concertation ; elle requiert donc des acteurs motivés ainsi qu'une écoute, une compréhension mutuelle et un consensus entre ces acteurs. La gestion adaptative est un processus cyclique, organisé en étapes, dont les principales sont : -la définition d'objectifs partagés par l'ensemble des acteurs impliqués, -le partage et la synthèse des connaissances scientifiques, techniques et tacites, -la définition de scénarios de gestion, en cohérence avec les étapes précédentes, -la mise en oeuvre des scénarios et le suivi de leurs effets, -l'évaluation et le retour d'expérience auprès des parties prenantes, voire du grand public. A l'issue de ces étapes, un nouveau cycle débute, avec une redéfinition éventuelle des objectifs de gestion. Chacune des étapes citées est indispensable au bon fonctionnement de la gestion. Plus particulièrement, la définition des objectifs est l'élément central car elle va orienter l'ensemble de la gestion. Cependant, elle est souvent simplifiée à la seule détermination de niveaux de prélèvements par la chasse, alors qu'elle pourrait également inclure, par exemple, des objectifs relatifs à la qualité de la chasse ou au renouvellement des peuplements forestiers

Using basic plant traits to predict ungulate seed dispersal potential

International audienceHabitat fragmentation contributes to the decline of plant species by decreasing gene flow among populations. Restoring connectivity among habitat patches is therefore a major issue for plant conservation. However, deciding where to focus restoration efforts requires identifying suitable dispersers for each target plant species. We collected data from the literature on wild and domesticated ungulates, known to be effective seed dispersers, and on the plants they dispersed in Europe via epi- and/or endozoochory. We performed a systematic literature review to identify plant and animal traits relevant for seed dispersal. We first modeled the relationships between epi- or endozoochory and a priori selected plant traits (diaspore releasing height, length, shape and morphology, and habitat openness). The differences we underlined between the two dispersal mechanisms justified splitting our analyses accordingly. Then, for each dispersal mechanism, we asked whether basic plant traits could be used to predict specific traits of ungulates as endozoochorous or epizoochorous seed dispersers. We modeled the relationships between a priori selected ungulate traits for epizoochory (habitat openness, shoulder height, hair curliness, and hair length) and for endozoochory (habitat openness, body mass, feeding type and digestive system) and plant traits. Plant habitat openness and diaspore morphology were the predictors that most often explained differences among ungulates for epizoochory, whereas plant habitat openness and diaspore releasing height most often explained differences for endozoochory. Our trait-based predictive models can help improve our ability to propose more precise management decisions for the conservation of plant populations worldwide by taking into account ungulate dispersers

Seed dispersal by temperate ungulates: Revisiting "foliage is the fruit"

International audienceBackground/Question/Methods When we talk about fruits, we generally think of the fleshy, juicy structures frugivorous birds, bats or primates feed upon, mostly in tropical ecosystems. Indeed, the fruit is the reward the plant offers to the animal that disperses its seeds. But, if we move back to temperate ecosystems, the structures that contain the seeds are generally dry, inconspicuous fruits like achenes or capsules. In his well-known paper, D.H. Janzen (1984) proposed that the reward for the large generalist herbivore dispersers in this case was actually the nutrient-rich foliage surrounding the dry fruits; the “vegetative portions […] function ecologically as an attractive fruit”. This led to the “Foliage is the Fruit” hypothesis. To revisit this hypothesis and its associated predictions, we present recent results obtained from our long-term research program on long-distance seed dispersal by large herbivores (greenhouse germination tests, feeding experiments …) and from data collected in the literature and compiled in two recent meta-analyses (Albert et al. 2015a, b). We developed an approach based on the traits of the plants being dispersed, the sympatric herbivorous ungulates (Cervus elaphus, Capreolus capreolus and Sus scrofa) studied, and their interactions. Results/Conclusions We addressed and confirmed 8 out of the 10 initial predictions proposed by Janzen. As expected, we found that large herbivorous ungulates select the most nitrophilous plants. One other key factor we investigated is the position of the fruit on the plant (“seed releasing height” in trait databases) in relation to animal shoulder height. We also found that the fruits and associated seeds dispersed by the three ungulates mainly belonged to plants from open habitats (grasslands, scrublands …) and that their light, rounded seeds persisted in the long-term in the soil seed bank. The plants consumed mainly corresponded to plants present in the preferred feeding habitats of the three ungulates. Most of the fruits and seeds that clung to animal fur either came from open habitats or from nitrophilous plants; this pattern confirms that nutrient-rich foliage leads to a higher encounter rate between plant reproductive parts and the animal body. We suggest considering this latter assertion as an extension of the “Foliage is the Fruit” hypothesis

Rewilding expérimental améliore la composition fonctionnelle des prairies et l'utilisation de l'habitat des pollinisateurs

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Rewilding expérimental améliore la composition fonctionnelle et l'utilisation de l'habitat des pollinisateurs d'une prairie

International audience1. Semi-natural grasslands are rich in biodiversity and thus important habitats for conservation, yet they are experiencing rapid declines due to agricultural intensification and abandonment. Promoting a more diverse mammalian herbivore community, including large and megaherbivores, may result in positive cascade effects for biodiversity and ecosystem functioning. Therefore, reintroducing an ecologically functional substitute of an extinct large herbivore could mitigate current biodiversity declines and foster semi-natural grassland conservation. 2. To test this hypothesis, we set up a 3-year rewilding experiment where 12 feral horses were introduced in three 10-hectare enclosure replicates (four horses per enclosure). We used community-weighted mean plant functional traits to elucidate plant community changes induced by grazing through time. We also investigated the effects of this experimental treatment on insect pollinated plants and on pollinator habitat use. 3. The grassland community exerted a mixed tolerance/avoidance response to grazing. This resulted in plant functional compositional changes which favoured prostrate plant species with higher specific leaf area, characteristic of ruderal communities. 4. Plant species richness was higher in grazed compared to ungrazed areas. Butterfly and bumblebee habitat use, as well as feeding and resting activities were also higher in grazed areas. Moreover, the number of pollinators increased with plant species richness. 5. Synthesis and applications. This study demonstrates that, to enhance the diversity of a given herbivore community with ecological replacements of extinct wild horses can have significant effects on the functional composition of grasslands. It can also mitigate plant species declines, in particular bee-dependent plants, and boost pollinator habitat use. Novel management alternatives are urgently needed to reverse the negative effect of land abandonment in European agricultural landscapes. Thus, rewilding interventions with large mammalian herbivores may offset current biodiversity declines by maintaining important functional links between plants and pollinators in grassland ecosystems