Reliability of macaques as seed dispersers

Seed dispersal is an ecological process crucial for forest regeneration and recruitment. To date, most studies on frugivore seed dispersal have used the seed dispersal effectiveness framework and have documented seed-handling mechanisms, dispersal distances and the effect of seed handling on germination. In contrast, there has been no exploration of "disperser reliability" which is essential to determine if a frugivore is an effective disperser only in particular regions/years/seasons or across a range of spatio-temporal scales. In this paper, we propose a practical framework to assess the spatial reliability of frugivores as seed dispersers. We suggest that a frugivore genus would be a reliable disperser of certain plant families/genera if: (a) fruits of these plant families/genera are represented in the diets of most of the species of that frugivore, (b) these are consumed by the frugivore genus across different kinds of habitats, and (c) these fruits feature among the yearly staples and preferred fruits in the diets of the frugivore genus. Using this framework, we reviewed frugivory by the genus Macaca across Asia to assess its spatial reliability as seed dispersers. We found that the macaques dispersed the seeds of 11 plant families and five plant genera including at least 82 species across habitats. Differences in fruit consumption/preference between different groups of macaques were driven by variation in plant community composition across habitats. We posit that it is essential to maintain viable populations of macaques across their range and keep human interventions at a minimum to ensure that they continue to reliably disperse the seeds of a broad range of plant species in the Anthropocene. We further suggest that this framework be used for assessing the spatial reliability of other taxonomic groups as seed dispersers.

Endozoochorous seed dispersal by Japanese macaques (Macaca fuscata): Effects of temporal variation in ranging and seed characteristics on seed shadows

Variation in seed shadows generated by frugivores is caused by daily, seasonal, and inter-annual variation in ranging, as well as inter-specific variability in gut passage times according to seed characteristics. We studied the extent to which seed weight, specific gravity, and daily (morning, afternoon, and evening) and inter-annual (2004 vs. 2005) variation in ranging affected seed shadows generated by wild Japanese macaques (Macaca fuscata) in northern Japan. The macaques ingested fleshy fruits of 11 species during the two year study period; Viburnum dilatatum (Caprifoliaceae: heavier seeds with higher specific gravity) and Rosa multiflora (Rosaceae: lighter seeds with lower specific gravity) were eaten frequently in both years. The travel distances of macaques after feeding on V. dilatatum and R. multiflora fruits were estimated by combining feeding locations and ranging patterns measured in the field with gut passage times of model seeds in captive animals. Median travel distances after fruit feeding were 431 (quantile range: 277-654) and 478 m (265-646), respectively, with a maximum of 1,261 m. Neither year nor time of day affected travel distances. The gut passage time of model V. dilatatum seeds was longer than that of model R. multiflora seed, but this did not affect dispersal distances. Seed shadows for both species over 2 years showed unimodal distribution (peak: 101-500 m) and more than 90%, 20%, and 3% of ingested seeds were estimated to be dispersed >100, >500, and >1000 m, respectively, the longest known distances among macaque species. R. multiflora seeds tended to be dispersed further in 2004 than 2005, but V. dilatatum seeds were not, implying that inter-annual variations in ranging pattern due to the distribution and abundance of nut fruiting could affect dispersal distance.

Seeds Recovered from the Droppings at Latrines of the Raccoon Dog (Nyctereutes procyonoides viverrinus): The Possibility of Seed Dispersal

Medium-sized carnivorous mammals are important seed dispersers of fleshy fruits. The raccoon dog (Nyctereutes procyonoides viverrinus) often feeds on fleshy fruits and forms latrines. This behavior may potentially lead to seed dispersal. To determine if this is the case, we studied 1) seed recovery in the droppings of raccoon dogs, and 2) the transportation of seeds between habitats using plastic markers in a western suburb of Tokyo, Japan. In total, 32,473 seeds of 50 plant taxa were recovered from 120 raccoon dog droppings during a year, and 95.7% of the seeds were found to be those of fleshy fruits. The species most frequently recovered were the eurya (Eurya japonica, 52.6%), the brambles (Rubus spp., 17.4%), and the black night shade (Solanum nigrum, 16.0%). A total of 7,412 plastic markers were embedded in baits at 14 bait plots and were recovered in the feces of the raccoon dogs at 22 latrines. The "transportation rates" were calculated in 50-m distance classes and found that most seeds (43.5%) were deposited within 50 m from the bait point, suggesting very short seed dispersal distances. Inter-habitat transportation was observed: 64.9% of the retrieved markers deposited in the forest were transported to other places within the forest. In contrast, almost all of the markers (99.4%) deposited in the open site were transported within the same habitat. These findings suggest that the seeds of forest plants bearing berries can be dispersed out of the forest to open areas by raccoon dogs.