Interspecific interactions disrupted by roads

Roads have pervasive impacts on wildlife, including habitat loss and fragmentation, road mortality, habitat pollution and increased human use of habitats surrounding them. However, the effects of roads on interspecific interactions are less understood. Here we provide a synthesis of the existing literature on how species interactions may be disrupted by roads, identify knowledge gaps, and suggest avenues for future research and conservation management. We conducted a systematic search using the Web of Science database for each species interaction (predation, competition, mutualism, parasitism, commensalism and amensalism). These searches yielded 2144 articles, of which 195 were relevant to our topic. Most of these studies focused on predation (50%) or competition (24%), and less frequently on mutualism (17%) or, parasitism (9%). We found no studies on commensalism or amensalism. Studies were biased towards mammals from high-income countries, with most conducted in the USA (34%) or Canada (18%). Our literature review identified several patterns. First, roads disrupt predator-prey relationships, usually with negative impacts on prey populations. Second, new disturbed habitats created in road corridors often benefit more competitive species, such as invasive species, although some native or endangered species can also thrive there. Third, roads degrade mutualistic interactions like seed dispersal and pollination. Fourth, roads can increase parasitism rates, although the intensity of the alteration is species specific. To reduce the negative impacts of roads on interspecific interactions, we suggest the following management actions: (i) verges should be as wide and heterogenous as possible, as this increases microhabitat diversity, thus enhancing ecosystem services like pollination and seed dispersal; (ii) combining different mowing regimes can increase the complexity of the habitat corridor, enabling it to act as a habitat for more species; (iii) the use of de-icing salts should be gradually reduced and replaced with less harmful products or maintenance practices; (iv) wildlife passes should be implemented in groups to reduce animal concentrations inside them; (v) periodic removal of carcasses from the road to reduce the use of this resource by wildlife; and (vi) implementation of traffic-calming schemes could enhance interspecific interactions like pollination and avoid disruption of predator-prey relationships.

Human Disturbance Affects Dung Beetle Assemblages in French Guiana Forests

French Guiana forests are threatened by increasing human activity such as infrastructure development, facilitating access to the forest and, therefore, logging, mining, farming and hunting. To highlight the impact of human pressure on the forest fauna, dung beetle assemblage was analyzed near Saint-Georges-de-l’Oyapock and compared with other sites in French Guiana, considering the distance to the main city and forest cover loss as proxies of human activities. Hill numbers and beta diversity were calculated. Non-metric multidimensional scaling and redundancy analyses were carried out to disentangle the effect of the distance to the nearest city and forest cover loss as proxies of human pressure, but also temperature and rainfall as proxies of climatic variations on dung beetle assemblage. Species richness increased significantly with the distance to the nearest city and decreasing forest cover loss. Assemblage structure varied among sites mainly with distance to the nearest city but also with rainfall. It varied also with forest cover loss, but not significantly. This study showed that human disturbances and climatic conditions, even if represented by proxies, affected dung beetle assemblage structures in French Guiana forests.

Arboreal camera trap reveals the frequent occurrence of a frugivore-carnivore in neotropical nutmeg trees

Arboreal and flying frugivorous animals represent primary dispersers in the Neotropics. Studies suggest a possible compensation for the loss of large species by smaller ones with expanding rampant anthropogenic pressures and declining populations of larger frugivores. However, studies on seed dispersal by frugivores vertebrates generally focus on the diurnal, terrestrial, canopy, and flying species, with the nocturnal canopy ones being less studied. Setting camera traps high in the canopy of fruiting nutmeg trees revealed for the first time the high frequency of the kinkajou (Potos flavus, Schreber, 1774, Procyonidae), an overlooked nocturnal frugivore species (Order Carnivora) in the Guianas. The diversity of the fruit species consumed by the kinkajou calls for considering it as an important seed disperser. The overlap of the size of seeds dispersed by frugivores observed in nutmeg trees suggests that the small (2-5 kg) kinkajou may compensate for the loss of large (5-10 kg) frugivorous vertebrates in the canopy. Camera traps visualise how the kinkajou is adapted to forage in the nutmeg tree crown and grab the fruit. Such information is vital for conservation because compensation of seed dispersal by small frugivores is crucial in increasing anthropogenic stressors.