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

Hiroto Enari,Haruka S. Enari

doi:10.1007/s42991-020-00097-9

Abstract

Interest in trophic interactions and ecosystem functions derived from carcass consumption by scavengers has been increasing. Here, we conducted the first evaluation of scavenging processes in an ecosystem with heavy snow, located in northern Japan, which is characterized by the limitations of visual and odor cues to detect carcasses. In this study, we verified the behavioral traits and assemblage compositions of avian and mammalian scavengers, which consumed six different carcass types buried in snow. We measured the visits of scavengers using camera traps between 2010 and 2020. The total scavenger richness observed was relatively low (only 12 species) compared to warmer biomes. We observed seven avian scavenger species, but their visit frequencies were extremely low compared with those of nocturnal mammalian scavengers, such as raccoon dogs (Nyctereutes procyonoides) and martens (Martes melampus), which were able to detect carcasses more rapidly and frequently. Our findings imply that large snow piles significantly prevent avian scavengers from detecting carcasses. In contrast, the snow piles could protect carcasses from the freezing air and ensure the occurrence of a basal level of microbial decomposition, possibly leading to carcass decomposition. This probably results in carcasses still providing odor cues for mammalian scavengers with heightened sense of smell. Moreover, considering the high carcass consumption rate (91.3% of full-body carcass; n = 23) and short carcass detection times (approximately 90 h) observed, it is possible that scavenging in heavy snowfall conditions has become systematically integrated into the foraging tactics of many mammalian scavengers.

Highlights

Carcass consumption by scavengers has become a popular topic for research, in an attempt to better understand the function of scavenging in ecosystems, such as accelerating nutrient cycling and modifying disease spreading (Mateo-Tomás et al 2017), and an overview of local ecosystem processes (DeVault et al 2003; Moleón et al 2014; Sebastián-González et al 2020)
Based on the photos of scavengers, we calculated the following: (1) day/night-time visit frequency, (2) time spent feeding per visit, (3) initial detection time, (4) consumption rate, (5) consumption time, and (6) carcass selectivity
There were meaningful differences in the consumption time among carcass types (ANOVA, F5, 32 = 2.21, p = 0.08; effect size η2 = 0.26), and the longest consumption time was observed in carcasses of macaques and raccoon dogs, which were completely consumed within 3–4 weeks

Summary

Introduction

Carcass consumption by scavengers has become a popular topic for research, in an attempt to better understand the function of scavenging in ecosystems, such as accelerating nutrient cycling and modifying disease spreading (Mateo-Tomás et al 2017), and an overview of local ecosystem processes (DeVault et al 2003; Moleón et al 2014; Sebastián-González et al 2020). There have been some attempts to prove the consumption process of mammalian carcasses in the temperate forests of Japan, which have shown that raccoon dogs (Nyctereutes procyonoides) and Asian black bears (Ursus thibetanus) are the most efficient vertebrate scavengers (Inagaki et al 2020), whereas invertebrate scavengers, such as burying beetles (Nicrophorus spp.), functionally compensate for this process when vertebrate scavengers are limited (Sugiura and Hayashi 2018). Note that these consumption patterns were observed during non-snowy seasons (i.e., summer or fall). These networks could be markedly characterized by the heavy reliance on vertebrate scavengers influenced by behavioral suppression associated with severe winter environments (Huggard 1993; Selva et al 2003, 2005) but hardly at all on invertebrates and microbes, which could promote carcass consumption in warmer seasons, especially under dense vegetation which prevents vertebrates from accessing the carcasses (Smith et al 2017)

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Discussion

Conclusion