Christophe Baltzinger

Prey-predator interactions in the wild are spectacular. Common reported cases come from ground-dwelling animals, in open areas and by daylight. Here, we report, for the first time, a sequence with the nocturnal arboreal kinkajou ( Potos flavus ), being followed ca. 20 minutes apart by one of its predators, the puma ( Puma concolor ), 33 m aboveground in a rainforest in French Guiana.

The functional roles of herbivores and carnivores in ecosystems have been relatively well studied: both can shape ecosystems through strong direct and indirect top‐down controls on other guilds. By contrast, the role omnivores play has been rarely explored, even though their diet spans several trophic levels and potentially has numerous effects on ecosystems through trophic and non‐trophic interactions. To gain a better understanding of the potential ecosystemic role of omnivore trophic and non‐trophic interactions, we performed a literature review on bears (Ursidae): a specific group of terrestrial omnivores. We submitted equation searches on the Web of Science for each type of interaction and omnivorous bear species. We kept 411 references highlighting a wide range of trophic and non‐trophic interactions in various ecosystems. Our review sheds light on the large number, diversity, and significance of these interactions. Moreover, we highlight a great variability of interactions among bear species but also across ecosystems for a given bear species. Beyond bears, our review shows that omnivores play a pivotal role in ecosystem functioning, not only through the strong interactions they have with a reduced set of other species but also through multiple weaker interactions with a diversity of taxa at different trophic levels. We therefore suggest that omnivores can be considered keystone species, and in any case, are worthwhile conservation targets, even though further studies are needed.

Frugivorous vertebrates, as seed dispersers and predators, play critical roles in forest ecosystem dynamics. Understanding their responses to human disturbances is essential for assessing ecosystem functioning and guiding conservation programs. Using 60 camera traps at nutmeg trees ( Virola kwatae and V. michelii , Myristicaceae), we monitored terrestrial and arboreal frugivores across three forest sites in French Guiana submitted to various human disturbances: a protected mature forest (least disturbed), a formerly exploited forest (intermediately disturbed), and a forest near a road subject to current hunting and logging (most disturbed). We assessed diversity, taxonomic composition and assemblage structure, while comparing visitation rates among sites. Richness remained consistent across all sites, with 19–20 species detected in the canopy and 14–16 in the understory. However, visitation rates significantly varied among sites. Specifically, terrestrial visitation rates decreased as disturbance levels increased (from 232.5 ± 53.7 individuals/100 trap‐days at the protected site to 87.2 ± 11.2 at the most disturbed site). Conversely, arboreal visitation rates tended to increase with increasing disturbances (from 43.5 ± 12.5 at the protected site to 80.3 ± 16 at the most disturbed site). In the canopy, the most disturbed site showed higher visits of kinkajous ( Potos flavus ) and golden‐handed tamarins ( Saguinus midas ). The understory at this same site had significantly lower visitation rates of “sensitive” species (those with low reproductive rates or targeted by hunters), such as white‐lipped peccaries ( Tayassu pecari ) and gray‐winged trumpeters ( Psophia crepitans ). In the canopy, site identity, tree diameter, fruit availability and canopy cover were significant predictors of assemblage composition. By contrast, none of the measured micro‐habitat variables contributed to the structure of the terrestrial assemblage, site identity being the single significant predictor. These findings underscore the importance of considering species‐specific responses and site disturbance histories, and highlight the value of protected and restoration areas in maintaining functional assemblages in tropical forests.

Animal-mediated seed dispersal is a key ecological process linking plant populations, community dynamics and ecosystem functioning. Yet, despite decades of research on disperser traits, animal sociality - a fundamental source of behavioural variation - has been largely overlooked. Variation in group size and composition shapes individual space use, feeding decisions, activity budgets and interindividual interactions, the behavioural mechanisms that determine whether, where and how seeds are dispersed. However, the consequences of animal sociality for seed dispersal remain largely unexplored. Our systematic literature review identified only eight studies that explicitly quantified the effects of group living on vertebrate-mediated seed dispersal. We elaborate on how sociality can influence every stage of seed dispersal, from seed load and transfer to release, with cascading consequences for seed dispersal effectiveness and plant recruitment. We propose a conceptual framework linking social organisation to the behavioural mechanisms underlying seed dispersal and identify key research directions for integrating animal sociality into seed dispersal ecology.

Knowledge of which animal clades and dispersal mechanisms contribute to seed dispersal is critical for understanding the ecology and evolution of plant communities. However, a broad understanding is limited by a focus on single clades and mechanisms. Here, we analyzed a Europe‐wide multi‐clade seed dispersal dataset with interactions among 447 animal species and 1901 plant species via four dispersal mechanisms: endozoochory (ingestion followed by egestion), epizoochory (external attachment), synzoochory (actively carried by vertebrates), and myrmecochory (dispersal by ants). We aimed to (1) characterize the relative importance of animal dispersal clades and biotic dispersal mechanisms; (2) evaluate links among clades and mechanisms; (3) compare dispersal of dry‐ and fleshy‐fruited diaspores; and (4) evaluate the predictive power of seed dispersal syndromes with empirical data on observed dispersal mechanisms. This revealed that endozoochory by birds and mammals encompasses 90% of plant–animal interaction records. Mammal species tend to have more plants depending upon their dispersal services; however, due to the larger diversity of bird species, more plants depend upon the cumulative services of birds (followed by mammals, insects, and reptiles). Plants with fleshy fruits comprise only 15% of all plant species dispersed by animals but had more animal partners per plant species than plants with dry fruits. Fleshy‐fruited plant species were more specifically selected by dispersers, while selection of dry‐fruited plants depended more on their relative abundance. Different animal clades tend to disperse plant species via different mechanisms. Endozoochory is the most recorded interaction for birds, mammals, and reptiles. Epizoochory is almost exclusively carried out by mammals, with a negligible role of birds, insects, and reptiles. Synzoochory is performed chiefly by ants (via myrmecochory), followed by birds and then mammals. Predicting vector importance by assigning dispersal syndromes based on diaspore traits (including endozoochorous, epizoochorous, synzoochorous, and myrmecochorous syndromes) only moderately predicted empirically observed dispersal mechanisms. Animals disperse many more species than inferred from diaspore traits, including plants with abiotic syndromes and plants without clearly visible morphological traits. Our results suggest that different animal clades perform complementary dispersal services via multiple mechanisms to plant species with fleshy as well as dry fruits.

Summary: Seed dispersal is critical for long‐term ecosystem resilience. However, excessive compartmentalisation of research into particular disperser guilds (e.g. birds) hampers our understanding of their relative contributions to overall seed dispersal, risking erroneous conclusions and overlooking key information gaps. Here, we evaluate how information about over 11 000 interactions between 1902 plant and 455 animal species in Europe accumulated over 400 years, and estimate information completeness across disperser guilds, plant types, and dispersal mechanisms (endozoochory, epizoochory, synzoochory, and myrmecochory). Information regarding the plants dispersed by each group of animals ranges from 27% to 79% sample coverage, with birds of prey (27%), ants (28%), and rodents (31%) particularly understudied. Most research focussed on fleshy‐fruited plants rather than dry‐fruited plants, and most on internal dispersal as the mechanism (endozoochory). Interestingly, scientists' perceptions of what are the most neglected disperser guilds do not correlate with our sample coverage estimates, showing an inability of the scientific community to identify information gaps. We urge researchers to bridge research silos and to study overlooked guilds, mechanisms, and plant types. Implementing community‐level synthesis studies that integrate data across guilds is essential for accurately predicting ecosystem responses to global change and developing effective conservation strategies.

Across Europe, wild ungulates’ populations are increasing, affecting their habitats and vegetation by its massive consumption, notably through browsing. This altered vegetation may impact other plant consumers (herbivores and omnivores) that depend upon the same resources at certain times of the year for vegetative parts or fruits. This potential competition may be detrimental for small and fragile populations. In this study, we investigated the plant-based diet overlap between the red deer, a large and hunted ungulate, the brown bear, a large and protected omnivore and the capercaillie, an elusive and threatened bird, all in the Pyrenees, using a fecal metabarcoding-based approach. Among the plant genera identified, 68% were shared between red deer and at least one of the other two threatened species. We highlighted a high overlap of consumed plant genera between red deer and brown bear (0.66) but also between brown bear and capercaillie (0.57) and red deer and capercaillie (0.45). This was mainly driven by fleshy-fruited plants including Rubus and Vaccinium, whereas dry-fruited woody plants were rather consumed by the capercaillie and various forbs and grasses by the red deer and the brown bear. Moreover, the red deer consumed a high diversity of plants per faeces, whereas the brown bear displayed the most diverse plant diet. The browsing by red deer of Vaccinium may reduce this key resource for brown bear and capercaillie potentially impacting their body mass or reproduction. Our study invites further investigation into the effect of ungulates on other megafauna populations.

Animal‐mediated seed dispersal is a key process in plant population dynamics, species distribution and ecosystem functioning. As long‐distance dispersal agents, ungulates help to maintain native plant populations facing abiotic changes in their habitat and habitat fragmentation or habitat loss. However, they also contribute to the spread of exotic species. Most ungulates live in groups, whose dynamics depend on the social status, personality, sex, age and body size of its different members. But how ungulate sociality affects zoochory remains largely unknown. We designed our experiment with sheep to test the effect of age composition on epizoochorous dispersal. Ewe lambs have stronger social links and respond more strongly to stress than adult ewes, therefore showing higher group cohesion. First, we expected that the more frequent interactions among ewe–lambs would shorten diaspore retention times and dispersal distances as ewe–lamb proportion increases. Second, diaspore exchange should be higher with increasing ewe–lamb proportion. We monitored groups of six domestic sheep Ovis aries (Romane breed) individuals with different age ratios, replicated four times: respectively, 0/6, 2/4, 4/2 and 6/0 adult ewes to ewe lambs. We attached five cocklebur Xanthium strumarium diaspores, colour‐coded for each animal, to the fur on each individual flank, 10 in total. We traced each diaspore fate during six‐hour sessions where we recorded movements, physical interactions among individuals and individual behaviour resulting in diaspore detachment or exchange. As expected, we found shorter retention times and dispersal distances and more diaspore exchanges as the proportion of ewe–lamb increases in the groups. Shaking, then scratching were the main behaviours leading to diaspore loss. Non‐intentional contacts between individuals were the most frequent interactions associated with diaspore exchange. We encourage further research on the effect of group living, be it group size or composition, on the different phases of epizoochorous dispersal.

A challenge in continuous cover forestry is converting even-aged stands to uneven-aged stands, which can be achieved by managing advanced regeneration through selective thinning. Thinning increases light and reduces competition, but its effects on oak seedling growth depend on thinning intensity, direction, understory vegetation, and browsing pressure. Here, we conducted a three-year experiment (2016-2019) in central France, applying thinning with varying intensities ( 7-30 % of the initial basal area) within an 18 m radius around 217 sessile oak (Quercus petraea (Matt.) Liebl.) seedlings in fenced and unfenced plots. We monitored seedling height growth, understory vegetation, and browsing impacts. Results showed that south-side thinning uniquely influenced seedling growth, with positive effects only above a threshold of understory vegetation cover and for taller seedlings. Browsing exclusion further enhanced growth. Understory vegetation cover remained unaffected by thinning, possibly due to drought conditions. These findings suggest that targeted south-side thinning, combined with assessing seedling height and understory competition, can improve oak regeneration, but forest managers should consider climatic conditions and may need complementary understory interventions to optimize outcomes.