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.

The mating system of an animal population or species refers to the general behavioral strategies that are used by males and females to obtain mates, and include mate acquisition and the number of mates obtained by an individual (Emlen & Oring, 1977). Mating systems and strategies across animals are driven by parental care, social and ecological environment, and the strength of sexual selection, which is determined by male-male competition for females and female mate choice (Shuster, 2009;Shuster & Wade, 2003).

Arboreal feeding signs are among several field indicators of the use of tree crowns by the Asiatic black bear (Ursus thibetanus) to sit and eat fruit; however, it is unclear which factors influence this sign formation in hard mast species. Here, we investigated the influence of seed production by individual trees and at a regional scale by major hard mast species on the detection of arboreal feeding signs. For 7 years, we quantitatively assessed seed production by 374–481 trees each year of three dominant hard mast species (Quercus crispula, Quercus serrata and Castanea crenata) in the Ashio‐Nikko Mountains of central Japan and checked for the presence or absence of arboreal feeding signs in these trees. We estimated individual tree energy values and regional mast energy values across these three species and evaluated the influence of each factor on the detection probability of arboreal feeding signs. Arboreal feeding signs were more likely in individual trees with larger mast energy values and during poor mast years. There was no difference among species in the relative importance of individual tree energy or regional mast energy. Interaction of factors was also detected: the magnitude of the positive effect of individual tree energy on the detection of arboreal feeding signs was larger in poorer mast years, and the negative effect of regional mast energy was more conspicuous in the case of trees with greater mast energy. Thus, bears may maximize their feeding efficiency on hard mast in various ways, depending on regional mast availability; during poor mast years, bears are more likely to climb trees with higher individual tree energy values and leave arboreal feeding signs. Arboreal feeding signs cannot be used as an indicator of bear density unless both individual tree energy and regional mast energy values are monitored.

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Energy balance (i.e., energy intake minus energy expenditure) is an essential factor when evaluating an animal's nutritional state. We aimed to identify periods of the year that are most important for Asian black bears (Ursus thibetanus) in terms of energy balance. We estimated bears’ daily energy balance by estimating energy intake based on the energy content (kcal/g) of major food items, their average ingestion rate (g/min), and daily feeding time (min) and by estimating energy expenditure using an equation for the costs of resting, traveling, and feeding based on behavioral data of 34 bears fitted with GPS collars in central Japan. Because food habits of bears change seasonally, we estimated daily energy balance for each month. And, because bears change their feeding behavior depending on the availability of hard mast, we made separate estimations for years of good and poor mast conditions during autumn. We identified major food items from fecal analysis and calculated the gross energy content per unit for each item. Based on direct observation of bears feeding over 10 yr, we measured ingestion rates of the major food items; Quercus crispula acorns on the tree had the highest ingestion rate, whereas the values of other items did not show notable characteristics. The variability of energy expenditure rose moderately in good mast years, except for males. On the other hand, there was a bimodal pattern of energy intake and energy balance, declining from May to July, rising again from August to October, and declining in November. The peak of energy intake and energy balance was larger in good mast years than in poor mast years only for females, whereas the cumulative energy balance in good mast years was larger than in poor mast years for both sexes. After poor mast years, the cumulative energy balance of males becomes negative in February, during hibernation, and did not exceed zero until August, even if they could start feeding in May. Thus, further longitudinal studies that examine cumulative energy balance, rather than energy balance alone, are necessary to clarify the seasonal change in the nutritional state of Asian black bears.