Prey refuges as predator hotspots: ocelot (Leopardus pardalis) attraction to agouti (Dasyprocta punctata) dens

We tested the hypothesis that prey refuges attract predators, leading to elevated predator activity in the vicinity of refuges. We used camera traps to determine whether the spatial activity of a predator, the ocelot (Leopardus pardalis), was biased toward refuge locations of its principal prey, the agouti (Dasyprocta punctata). We radio-tracked agoutis at night to locate active refuges and compared the activity of ocelots between these refuges and surrounding control grid locations. We found that ocelots visited the area near agouti refuges significantly more often and for longer periods of time than control locations, and that they actively investigated the refuge entrances. Both occupied and unoccupied refuges were visited, but the duration of inspection was longer at occupied refuges. As the ocelots could probably not see the agoutis within the refuges, olfaction likely cued foraging ocelots. Two refuges were repeatedly visited by the same ocelots on different days, suggesting spatial memory. Overall, our results suggest that predators can be attracted to prey refuges or refuging prey. The benefits to prey of staying nearby a refuge would thus be counterbalanced by higher likelihoods of predator encounter. This should stimulate prey to use multiple refuges alternatingly and to not enter or exit refuges at times of high predator activity

Topsoil removal in degraded rich fens: Can we force an ecosystem reset?

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Thieving rodents as substitute dispersers of megafaunal seeds

The Neotropics have many plant species that seem to be adapted for seed dispersal by megafauna that went extinct in the late Pleistocene. Given the crucial importance of seed dispersal for plant persistence, it remains a mystery how these plants have survived more than 10,000 y without their mutualist dispersers. Here we present support for the hypothesis that secondary seed dispersal by scatter-hoarding rodents has facilitated the persistence of these large-seeded species. We used miniature radio transmitters to track the dispersal of reputedly megafaunal seeds by Central American agoutis, which scatter-hoard seeds in shallow caches in the soil throughout the forest. We found that seeds were initially cached at mostly short distances and then quickly dug up again. However, rather than eating the recovered seeds, agoutis continued to move and recache the seeds, up to 36 times. Agoutis dispersed an estimated 35% of seeds for >100 m. An estimated 14% of the cached seeds survived to the next year, when a new fruit crop became available to the rodents. Serial video-monitoring of cached seeds revealed that the stepwise dispersal was caused by agoutis repeatedly stealing and recaching each other's buried seeds. Although previous studies suggest that rodents are poor dispersers, we demonstrate that communities of rodents can in fact provide highly effective long-distance seed dispersal. Our findings suggest that thieving scatter-hoarding rodents could substitute for extinct megafaunal seed dispersers of tropical large-seeded trees

Eutrophication triggers contrasting multilevel feedbacks on litter accumulation and decomposition in fens

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Do high iron concentrations in rewetted rich fens hamper restoration?

In this study we address the question of the extent to which iron may be a limiting factor in restoring rich fens in the temperate climate zone of Europe. Rewetted fens that were heavily degraded in the past by draining over a long period, were compared with pristine fens or fens with slightly altered hydrological systems. The chemical composition of peat and of pore water was analysed and related to the composition of the vegetation of the fens. The species composition and chemistry of the topsoil of restored fens differed markedly from that of the other fens, while the chemistry of the pore water from deeper layers showed only minor differences. Multivariate analysis revealed that differences in species composition between both categories were strongly related to the concentration of Fe in the pore water in the topsoil. Restored sites with high iron concentrations in the pore water (> 100 mu mol.L-1) lacked many vascular plants and mosses typical of peat forming fens. Iron and inorganic phosphorus pools in the topsoil of most restored fens were much greater than in the reference fens. A higher soil phosphorus pool originated mainly from the iron-bound fraction. We conclude that these differences are strongly governed by local processes and not by regional differences in climate, which were associated with geographical distribution of the different fens studied. The strong accumulation of iron and phosphorus in restored fens is attributed to a long history of drainage, which enhanced the accumulation of oxidized iron in the topsoil and also lowered the concentrations of calcium, magnesium and sulphur through drainage-caused reoccurring oxidation-reduction and leaching processes. A high iron and associated high phosphorous content appears to be an important and possibly irreversible bottleneck to restoring biodiversity and accumulation of peat with a low degree of humification in degraded fens. If a degraded fen has a low iron content then it is more likely to be restorable

Do high iron concentrations in rewetted rich fens hamper restoration?

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