Vertebrate scavenger guild composition and utilization of carrion in an East Asian temperate forest

Abstract

Scavenging is a common feeding behavior by many species that plays an important role in ecosystem stability and function while also providing ecosystem services. Despite its importance, facultative scavenging on large animal carcasses has generally been overlooked in Asian temperate forest ecosystems. The aim of this study was to determine the composition and feeding behavior of the facultative scavenger guild as it relates to sika deer (Cervus nippon) carcasses in Japanese forests. There are no obligate scavengers or large predators that kill adult ungulates, but humans fill the role of large predators by culling deer for population management. We documented nine vertebrate species scavenging on deer carcasses and found that mammals were more frequent scavengers than birds and also fed for longer durations. This result suggests that there is a facultative scavenger guild composed mainly of mammals in our forest ecosystem and that carcass utilization by birds was restricted to only forest species. Raccoon dogs (Nyctereutes procyonoides) and Asian black bears (Ursus thibetanus) were the most frequent scavenger species and also fed for longer durations than other scavengers. There were significant seasonal differences in scavenging by Asian black bear, Japanese marten (Martes melampus), and mountain hawk‐eagle (Nisaetus nipalensis), suggesting the availability of other food resources may alter facultative scavenging by each species. Our results support that scavenging is widespread in this system and likely has important functions including building links in the food web.

Not avian but mammalian scavengers efficiently consume carcasses under heavy snowfall conditions: a case from northern Japan

“…However, if avian scavengers can subsequently detect resources possibly by using clues on the snow surface left by mammalian scavengers such as tracks and digging, they are likely to hold doggedly onto resources. This notion could be supported by the fact that, although the time spent feeding per visit by avian species is less than half of that of mammals during non-snowy seasons (Inagaki et al 2020), the current findings exactly showed an opposite trend (Fig. 3).…”

“…Black bears potentially have a greater impact on regional scavenger communities by monopolizing most available carcasses (Allen et al 2014(Allen et al , 2015. Although we should refrain from discussing the influence of the presence/ absence of black bears on scavenger communities due to the lack of year-round carcass monitoring in the study area, we would like to highlight that no significant changes in feeding behaviors of the leading scavengers (i.e., raccoon dogs and martens), such as an increase in visit frequency and time spent feeding during winters, were observed, at least compared to the results of Inagaki et al (2020). This might be because, instead of being relieved of severe competition with black bears during winters, the mesocarnivores were compelled to face an increase in thermoregulatory costs and movement costs stemming from cold and snow, which strictly restrict their activity budgets, as is obviously shown in co-occurring mammals (e.g., Japanese macaque; Enari 2014).…”

“…Notably, even during nonsnowy seasons, the visit frequency of avian scavengers is originally limited in cool-temperate forests of Japan where dense vegetation with a closed canopy is common. In fact, Inagaki et al (2020) reported that less than half of sika deer carcasses were consumed by avian scavengers during the summer (i.e., 40.0%, n = 20) and fall (45.5%, n = 22). Although canopy openness improves during winter due to defoliation, the current experiments showed even lower values (i.e., 20%).…”

“…During non-snowy seasons, black bears are expected to join the scavenger guild as a dominant player in cool-temperate forests (Inagaki et al 2020), presumably including our study area. Black bears potentially have a greater impact on regional scavenger communities by monopolizing most available carcasses (Allen et al 2014(Allen et al , 2015.…”

Timing of fruiting rather than topography determines the direction of vertical seed dispersal by mammals and birds

“…In the three mountains, fauna of frugivorous mammals and birds are relatively wellpreserved (1,29,37,(39)(40)(41). For example, all of the representative intermediate-sized frugivorous mammals in Japan [red fox (Vulpes vulpes), Japanese badger (Meles anakuma, previously known as a subspecies of Meles meles), raccoon dog (Nyctereutes procyonoides), and Japanese marten (Martes melampus)] are present.…”