Japanese walnut (Juglans mandshurica) is commonly infested by the larvae of the Indian meal moth (Plodia interpunctella). Japanese squirrels (Sciurus lis) that mainly feed on walnuts could increase their foraging efficiency if they could discern healthy or insect-damaged walnuts before they crush to feed on or transport them. In this study, we experimentally examined how Japanese squirrels and sympatric raccoon dogs (Nyctereutes procyonoides) deal with two types of walnuts (infested or healthy), in Okutama, Tokyo. We found that squirrels selected healthy nuts at a significantly higher rate at the beginning of contact and abandoned insect-damaged nuts quicker than raccoon dogs. The behavioral patterns of squirrels were significantly different according to the type of walnut they started to touch, while those of raccoon dogs did not differ regardless of the type. It is likely that squirrels can change their behavior according to the type of the walnut before and during picking up the nut, unlike raccoon dogs, thereby reducing the risk of feeding on, transporting, and storing insect-damaged nuts found on the forest floor. In comparison, raccoon dogs do not discriminate between a healthy nut and an insect-damaged nut.

The behavioral pattern of sika deer, Cervus nippon, can be affected by various factors such as vegetation, season, body weight, and age. To clarify the differences in the behavior of sika deer in Nara Park, Japan, among seasons and size classes (including infant-yearlings, adult females, young males, and adult males), we conducted a route census method during daytime (9:00–16:00). The ratio of grass and litter feeding to body size decreased as the body size increased, but the ratio of feeding on human fed food (i.e., deer cracker) to body size increased as body size increased. Thus, it may have been necessary to compete with other sika deer to obtain human-fed food. The seasonal change in behavioral patterns varied according to size class. When zoysia grass grew, sika deer of all size classes generally fed on zoysia grass. In autumn, sika deer fed on litter, when fallen leaves and acorns were available, but the starting time was delayed for young and adult males. Young and adult males also had increased mating behavior in the mating period around October. In January and February, when it is coldest, all size class deer tended to sit or rest, avoiding active behavior.

Hair morphology such as hair length and width, medulla width, and external morphology of scales and medulla were examined to establish the identification key of hairs of two species of Soricidae and four species of Muridae for the purpose of food habit analysis of alien carnivores on Okinawajima Island. All species had straight guard hair, and three murid species had one more type of guard hair. Only one type of under hair was observed in common to all species. The straight guard hairs were divided at 10 mm of an average hair length. They could be classified to species level based on the structure of the scale and the medulla. The other type of guard hair observed in the three murid species was identified by hair length and width. Furthermore, the three species could also be identified by the external morphology and the structure of medulla. Based on these characteristics, we created an identification key using hair morphology for six species. This study clarified that guard hair is suitable for species identification. Although it is difficult to identify species using only one characteristic, a comprehensive assessment makes identification possible.

Small mammals were surveyed in the north central region of the Ina Mountains and around the summit of Mt. Oikeyama in the Akaishi Mountain Range, central Honshu, Japan. In total, 17 adult individuals of either Eothenomys smithii, Apodemus speciosus, or A. argenteus, were collected from the Hinoki plantations (1,090–1,120 m altitude) in the former, and 15 adult individuals of either Dymecodon pilirostris, Urtorichus talpoides, E. smithii, Microtus montebelli, A. speciosus, or A. argenteus were collected from the subalpine coniferous forests and larch plantations (1,750–1,820 m altitude) in the latter. The distributions of these species considering previous studies, closely related species in nearby mountainous areas, and present records of each species seem to occur according to not only vegetation and altitudes but also artificial factors such as plantations, or colonization histories depending on geographical features in these areas.

Four fruit bat specimens, dating back to the Taisho to the early Showa era, were found in high schools in the Ehime Prefecture. They had been collected from the Ogasawara Islands or Ryukyu Islands, far from the Japanese mainland. These specimens, which were stored in high school as educational materials for science (natural history), are important for understanding the past distribution channel of wild animals and people’s attitudes toward living things at that time. Today, these poorly preserved specimens are no longer needed at schools and are likely to be discarded in the near future. Because some of the specimens collected from the late Meiji to the early Showa era have special academic value, urgent systematic collection of the specimens by museums or researchers is needed.

On September 17, 2019, we captured a completely white pelage long-clawed shrew, Sorex unguiculatus Dobson, 1890, in Kushiro wetland in Hokkaido, Japan. The shrew was captured in a pit-fall trap set for the investigation of amphibians. The shrew was found dead. The color of the fur and skin suggested that it was an oculocutaneous albino. The present specimen is the first official record of oculocutaneous albinism in S. unguiculatus. The specimen is preserved in the Kushiro City Museum, Japan.

We evaluated the green areas in Tokyo as potential habitats for Japanese badgers (Meles anakuma) based on previously reported home range size. We identified green areas from a vegetation map (2000–2011) and used them as candidates for potential habitat availability. We then determined the proportion of these continuous green areas that exceeded the viable minimum home range size required by Japanese badgers. From previous studies, the minimum size required by females was 5.2 ha. We also used 30.0 ha according to a habitat suitability index. For males, the maximum size in suburban Tokyo’s Satoyama landscape is 72.1 ha, and up to 407.1 ha in the mountainous Nagano area. Our analysis showed that the mean size of Tokyo’s green areas decreased from west (natural/suburban habitat) to east (urban habitat); indeed, 88.9% of the entire green areas in Tokyo were in the western region. We found 17 continuous green areas covering 72.1 to 407.1 ha in the western and central region, i.e., the range likely to be large enough to support Japanese badgers, and only two green areas exceeded 407.1 ha. In the eastern region, there were only two green areas covering 72.1 to 407.1 ha, and no green areas ≥407.1 ha. Our study suggests that the reason why badgers are known to occur in western and central, but not eastern Tokyo, is likely due to a lack of available continuous habitat in this eastern region.

Predation of domestic cats (Felis silvestris catus) on native species is a global issue of concern for biodiversity conservation. Their impact on insular birds is known to be tremendous. However, studies on Japanese islands are still limited. A domestic cat catching an endangered Izu thrush (Turdus celaenops) was recorded by a camera trap on Mikura Island, Japan. A photo and a video of a domestic cat holding the Izu thrush was taken at 20:21 on July 24, 2018. The video showed that the Izu thrush was alive because it repeatedly opened and closed its bill. The video also showed that the bird was a chick because of the characteristic chick feathers. These results suggest that the domestic cat attacked a breeding nest of the Izu thrush. In addition, camera traps recorded cats carrying other species, such as streaked shearwater (Calonectris leucomelas). To obtain more evidence of cats killing native birds, further studies such as scat analysis are needed. Since free-ranging cats are reportedly present in most of the areas where the Izu thrush is distributed, the edification for appropriate cat owning and the removal of free-ranging individuals are needed to protect native birds.

In May and July 2019, two white killer whales were observed in the Nemuro Strait off Shiretoko Peninsula, Hokkaido. The first was presumed to be a mature male, and the second was a female or an immature male. When compared to previously reported pictures of white killer whales from the waters around the North Pacific, neither individual matched the characteristics of known individuals. Although it was not possible to determine whether these two animals were albino or leucism, all visible areas that would be black on a normal color type were white on these individuals. Since there have been no reports of such white killer whales off the coast of Japan, these two are considered to be the first records in Japan.

The topic of macroevolution of mammals has recently been disputed by paleontologists and molecular biologists, specifically in regards to the dispersal timing of crown Placentalia (crown Eutheria) and placental orders around the Cretaceous/Paleogene (K/Pg) boundary (ca. 66 Ma). Except Monotremata, there is no positive fossil evidence that Marsupialia (crown Metatheria) and Placentalia existed in the Mesozoic. Current fossil records from Cenozoic localities indicate that the oldest species included in the placental orders appeared at the beginning of the Paleocene (ca. 60–50 Ma). This strongly supports the explosive divergence model, which claims that crown placentals evolved immediately after the K/Pg boundary. However, this hypothesis is criticized primarily because the interval of diversification after the K/Pg boundary is too short in terms of molecular evolution of mammals. A plausible model that agrees with both paleontological and molecular phylogenetic studies explains that major crown clades of placentals (e.g., Xenarthra and Laurasiatheria) originated in the Late Cretaceous and then ordinal groups dispersed in the early Paleocene.

In this article, the recent progress in molecular phylogenetics of placental mammals and eutherians was reviewed. It was established that the eutherians consisted of three major clades: Afrotheria, Xenarthra, and Boreotheria, which corresponded to Africa, South America, and the ancient northern continent, Laurasia. This finding suggested that vicariance due to the breakup of the supercontinent played an important role in the evolution of eutherians. Furthermore, the time-tree analyses of molecular data showed that oversea dispersals also played an important role. The recent accumulation of abundant genome data allowed us to infer not only the phylogeny but also the life history traits of common ancestors. An application of the new method detected a post K-Pg nocturnal bottleneck, where all ancestral lineages of extant eutherians were nocturnal just before the Eocene-Oligocene transition at 33.9 mya.

In recent years, studies on wild animals have advanced with a technique termed “Bio-logging,” which uses data loggers that are attached to animals to measure parameters that are normally difficult to observe directly. Bio-logging was first used to study the basic diving physiology of marine mammals. Currently, its application has been expanded to the measurement of an array of diverse parameters, including depth, swimming velocity, acceleration, geomagnetic field, horizontal location, sound, heart rate, and to record videos. In this article, we summarize studies conducted on the diving physiology, behavioral ecology, and biomechanics of marine mammals using bio-logging technology. In recent years, bio-logging has been used for the investigation of animal ecology, oceanographic observation, and the management of livestock and pets. In this article, we present these latter cases, and discuss the future development of bio-logging.

The development of analytical methods in recent years has made it possible to conduct biochemical analysis of trace substances in samples collected outdoors. One such method involves a hormone, which is a physiologically active substance with ultra-trace elements. Therefore, it has become possible to extract hormones from samples containing various contaminants, including excreta, and monitor trace concentrations. The primary analytical method applied in recent years is the enzyme immunoassay; however, other methods such as radioimmunoassay, liquid chromatography/mass spectrometry, and immunochromatography are also used. The author assessed the physiological state of animals using another method: near infrared spectroscopy. This paper introduces the development of the estrus diagnosis method using near-infrared spectrum analysis of urine and the potential for fecal near-infrared spectrum analysis. In the final section, the paper introduces an immunochromatography method applicable at room temperature (e.g. 25°C) and a simplified stress checker with feces by using a smartphone app.

Next-generation sequencing (NGS) is a novel, massive, parallel DNA sequencing technology developed in the latter half of the 2000s. Thanks to the massive parallel sequencing of multiple samples and production of unprecedented data abundance, it has great potential to contribute to mammalogy, especially to evolution, ecology, and taxonomy of mammals. Despite being a decade since the development of this technology, it has not fully been applied to the research of Japanese mammalogists. In this paper, by briefly describing several NGS methods available to study wild mammals as well as introducing recent applications and progress, we show that now is the time to broadly expand Japanese mammalogy with this breakthrough in genome technology not only in the field of basic science, but also applied science, including the conservation and management of wild mammals.

In recent years, cases of unintentional capture of non-target species such as bears, Japanese serow, and medium-sized mammals by both box and snare traps set for sika deer and wild boar seems to be increasing in Japan. The strong promotion of the wild boar control program by the government, the expansion of classical swine fever among wild boar, increasingly inexperienced trappers, and range expansions of sika deer and wild boar in the northern part of Honshu Island may also be driving this phenomenon. The detriments of unintentional capture are: 1) impact on ecosystem, 2) decline in capture efficiency (CPUE), 3) risks to hunters and hikers, 4) increase in cost for governmental oversight agencies, 5) decrease in capture motivation of trappers, and 6) animal welfare.

Two tasks are thus equally urgent: reducing unintentional captures of non-target species, and controlling population levels of both sika deer and wild boar. As a bottom-up strategy, it is necessary to elucidate the occurrence mechanism of the unintentional captures and to develop a process to reduce them. As a top-down strategy, it is necessary to establish an information-gathering system for unintentional capture at the national level to monitor the situation in real time. Legal action will also be required to some extent.

Capture of sika deer (Cervus nippon) and wild boar (Sus scrofa) is promoted broadly in Japan. However, there are concerns about the increasing occurrence of unintentional capture of non-targeted species and its negative impact on the wild population of these species. It is necessary to prevent such capture and to appropriately address cases of its occurrence. In this paper, we review the laws, acts, and plans to investigate whether regulations or policies for preventing unintentional capture and addressing such incidences were described in these laws, acts, and plans. We found that regulations and policies on preventing unintentional capture and addressing its occurrence are described in the regulations, guidelines, and plans, and that most of them are established for bear species. Prohibiting the use of cable restraint traps could be an option to avoid unintentional capture. However, since it is necessary to promote capture of deer and boar, there is a need to prevent unintentional capture, attempt to release unintentionally captured individuals while minimizing damage to the individuals, and collaborative actions across disciplines. To this end, it is necessary to address the occurrence of unintentional capture, taking into consideration the local situations, by precisely assessing such occurrences and devising and implementing strategies to prevent such occurrences.

In Japan, in parallel with the policy of improving sika deer (Cervus nippon) capture, there has been an increase in the number of traps and their share in capture. The number of catches by trap type is rarely documented. It is presumed that the use of foot snare traps is high, as they are cheaper than box traps and enclosure traps and can be set by one person. Tallying the number of catches per capture tool is a subject for future study. Capture by foot snare traps tightens the foot with a wire rope. This method often has a long elapsed time before killing or releasing, causes individual damage and stress, and is problematic in terms of animal welfare. In addition, foot snare traps are hidden along animal trails; therefore, the capture of animals other than sika deer, especially large animals such as bears, serows, and wild boars cannot be avoided. Even if reporting on unintentional capture is required to understand the actual situation, accurate reporting cannot be expected until at least those standards that are not subject to punishment are clarified. Technical improvements are needed to reduce the damage and stress associated with trapping and to avoid unintentional capture. It is also necessary to develop sika deer population management strategies that do not depend on foot snare traps.

Effective wild boar management involves damage control, habitat management, and population control. In particular, population control is essential in total management, and it is enhanced in later years. In the case of using traps with bait, the risk of capturing non-targeted species increases, because the habitat of wild boar and other mammals overlaps occasionally around the forest edge. In addition, the area with an increased need for wild boar management is the same as the area where depopulation and aging have advanced. Therefore, in these areas, it is important to perform both labor saving for the capture of target species and risk reduction for non-targeted species capture by using ICT traps and educating bearers of culling.

Using data collected from various cases of unintentional capture of Asian black bears (Ursus thibetanus) across six prefectures in the western region of Japan, we analyzed and assessed animal welfare issues, possible impact on bear populations, risks involved through hunters and hikers, and effect of government budget constraints associated with the release of bears in remote areas.

This paper reports on the status of the permitted animal capture system in Komoro city, Nagano prefecture, and the current status of Japanese serow (Capricornis crispus) miscapture that occurs as a consequence of permitted capturing activities. In Komoro city, permitted capture work that had been carried out by hunting associations has been taken over by government administration, and administrative staff have begun releasing miscaptured Japanese serows. This change made it possible to clarify the circumstances of such miscapture, which were not well understood. After beginning to identify individual miscaptured Japanese serows with ear tags from April 2016, it was found out that 68 individuals had been miscaptured in 44 months (170 times in total). One was dead when it was found, and two died the day after release from complications of being trapped. 35 individuals were miscaptured several times, up to 14 miscaptures for the most-recaptured individual. Since many individuals were injured by traps, it is necessary to find capture methods that do not cause miscapture, to construct capturing systems under which miscaptured individuals can be released soon, and to establish and disseminate safe release methods that do not cause injury to both the releasing staff and Japanese serows. In addition, further study of miscapture of Japanese serows is required.

The number of culled sika deer (Cervus nippon) and wild boar (Sus scrofa) by snare traps has recently been increasing all over Japan. Coincidently with culling, many cases of unintentional capture of non-target mammals have also been reported. Details about unintentional capture of non-target animals are still unknown, because in Japan there is no obligation to report unintentional captures under the Wildlife Protection and Hunting Management Law.

In Komoro-city, Nagano, the municipal wildlife management system was recently reorganized and the municipal office has begun collecting data on the unintentional capturing of non-target mammals. These data revealed that 29.9–53.0% of all captured animals in 2015–2018 were non-target species. Among these were multiple medium-sized mammals—especially carnivores such as raccoon dogs (Nyctereutes procyonoides), foxes (Vulpes vulpes), and others—and most were killed after being captured by snare traps. We obtained information on the damage caused by the traps to the individual animals in various areas, and found their injuries were extensive. We must recognize the danger snare traps present to non-target species by unintentionally causing serious damage to these animals, discuss how to improve capture of target species by the snare traps, and design more scientifically and ethically sound wildlife management systems.