Inducing captive bats to self-feed is an essential procedure to maintain individuals under laboratory conditions for long periods of time, as it is difficult for bats that emit constant frequency calls to feed on non-fluttering prey. Here, we evaluated a new technique to induce self-feeding in captive bats by repeatedly training them to pick up mealworms from a feeding table in a cage (called “learning”). To determine the effectiveness of the training for long-term maintenance, captive bats were assigned to the following three feeding treatments: (1) learning, (2) sound-absorbing, in which the sound-absorbing material on the feeding table was covered to increase the efficiency of detecting mealworms, and (3) hand-feeding, the control treatment. The survival rates and the acclimation period of the bats were compared among the three treatments. In addition, for the “learning” treatment, the effect of capturing seasons, namely summer and winter, on the survival rate and the acclimation period of the bats were also analyzed. Learning showed a higher survival rate and an earlier acclimation period than the other two treatments. Furthermore, bats captured during their hibernation period showed a lower survival rate and a longer acclimation period than those captured during their active period. Our new training technique was, thus, effective for inducing bats to self-feed, but the season during which the bats are captured should be considered for its application.
The bats, distributed on Tokunoshima Island (T) and Amami-Oshima Island (A), were investigated using mist nets, harp traps, dead-leaf traps, and bat detectors. The body size of Murina ryukyuana was significantly larger on T than on A. The adults roosted individually during the active season, and frequently switched their day-roosts. The maximum movement between day-roosts ranged from 25 to 178 m, which was recorded by radio-tracking. The maximum maternal colony size was 16 and was maintained till November. The number of Myotis yanbarensis was less on T, perhaps because of their low capturing rate. The population of Rhinolophus cornutus orii was also lower on T, potentially due to the lower number of caves. Miniopterus fuscus flew widely at night on both T and A. Myotis macrodactylus was found at only one area on T, but three areas on A. Pipistrellus abramus were found in the urban areas of both T and A. Pteropus dasymallus was found on T. Tadarida sp. foraged extensively on both T and A, but its nests (rock cliffs) were only found on A. Two echolocation call types were found on T and two others on A, which are different from those of the above identified species.
To understand how medium to large mammals in forest environments utilize wallows, which are shallow depressions containing water that are formed by the wallowing of large mammals, camera traps were set up at six sites in eastern Tanzawa, Kanagawa. A total of 12 species were recorded over the 29 months from June 2015 to October 2017. The four most abundant species, which accounted for 88.2% of the photographs captured, were Cervus nippon, Sus scrofa, Nyctereutes procyonoides, and Meles anakuma. The most frequently observed behaviors of the four species were as follows. Cervus nippon males wallowed to appeal to females during the rut, but females visited the wallows only to drink. Sus scrofa regularly visited the sites to wallow in the mud. The two carnivorous species (Nyctereutes procyonoides and Meles anakuma)visited the wallows during the spring when they foraged for aquatic life. In addition to revealing that Cervus nippon males and females utilize the wallows for different purposes, a positive correlation was observed between the sodium concentration of the water and the frequency of female visits. These findings suggest that the wallows are used as saltlicks by Cervus nippon and as foraging sites by carnivores, suggesting that the wallows are an important habitat for forest mammals.
Recently in Japan, camera traps have been used for wildlife monitoring. Modern camera traps operate at a high-performance, thus, over thousands of images can be obtained. Ultimately, this can cause a disadvantage, as checking a large quantity of images is extremely laborious for researchers. This study attempted to decrease the labor involved with the use of the latest technology of image classification, “deep learning”, to recognize the presence of animals, animal species, and the number of heads automatically. Over 110,000 annotated images taken by camera traps were used for constructing our model. In this study, the sika deer (Cervus nippon), wild boar (Sus scrofa), Japanese serow (Capricornis crispus), and Asian black bear (Ursus thibetanus) were targeted. For animal recognition, our model achieved a 15.7% false-positive rate whilst maintaining a 99% true-positive rate. This drastically reduces the quantity of images that researchers must scan through to 43.3% of the original value. When an image of one of the four target species was input, our model successfully returned each species 79.6%, 76.4%, 82.1%, and 76.6% of the time as top-hit category, respectively. For the animal count, when images containing animals were input, each target species reached an accuracy of 91.9%, 84.4%, 91.6%, and 86.4%, respectively. These results suggest that deep learning in camera trap analysis can be a useful tool for reducing the labor cost.
We examined the dental root anomalies in 99 skulls of feral raccoons, Procyon lotor, collected from Nagoya City and the Higashimikawa region of Aichi Prefecture and Higashimatsuyama City of Saitama Prefecture, Japan. Extra roots and root fusion were both observed in the permanent cheek teeth: extra roots were common in P2/P2, P3, and M2, and root fusion was common in P2 and M2/M2. Extra roots were observed in the individuals from the Aichi and Saitama Prefectures, but the frequency was significantly higher (P < 0.001) in the Aichi Prefecture (Nagoya City: 90.9%, Higashimikawa region: 72.2%) than in the Saitama Prefecture (Higashimatsuyama City: 6.7%). Root fusion was only observed in the individuals from the Aichi Prefecture, and the frequency was slightly higher in Nagoya City (33.3%) than that in the Higashimikawa region (22.2%). These findings suggest that a local difference exists between the Aichi and Saitama Prefectures in the incidences of extra roots and root fusion. High incidence of the individuals with extra roots and/or root fusion from the Aichi Prefecture is explainable because the population was founded by a small number of individuals with these dental root anomalies.
Because the opportunity to obtain morphological information of whales is generally limited, analyses are sometimes conducted using insufficient sample sizes. In this study, the possibility of improving the accuracy of adult killer whale (Orcinus orca) sex prediction was evaluated statistically and from a practical viewpoint using sex discrimination rules with traditional linear discriminant analysis (LDA) and Random Forests (RF) machine learning algorithms. Eighteen cranial measurements from six female and six male adult killer whales (Orcinus orca) were collected in the west coast of Japan and analyzed. Simulation results using an independent test dataset and leave-one-out cross-validation suggested that LDA classifiers with variable selection generated overfitting rules. In contrast, RF classifiers suppressed overfitting in the development of classification rules from a small number of samples, and thereby constructed highly accurate sex prediction classification rules. Therefore, RF is more effective than LDA in solving the small sample size (SSS) problem in cranial measurements, as it reduced the risk of overestimation, and improved accuracy.
Predation on the Siberian flying squirrel (Pteromys volans) by the Ural owl (Strix uralensis) was investigated in a forest in Abashiri City, Hokkaido. We collected 163 owl pellets during the winters of 2008–2017 and analyzed 150 pellets out of them. During two of the winters (2009–2010 and 2015–2016), we detected the remains of 21 and 23 individual Siberian flying squirrels, respectively. There were annual fluctuations in the observation rate of owls (observed day/ survey day), ranging from 0% to 26.9%, and in the number of nests of the flying squirrel, ranging from 6 to 25 nests. During a winter, the owl observation rate was particularly high, and in the following year squirrel tree nest numbers decreased. Another year, the number of squirrels remains in owl pellets declined, and the number of squirrel tree nests increased in subsequent years. These results may indicate that owl predation affected the flying squirrel population.
In Mikura Island, Japan, feral cats (Felis silvestris catus) recently caused serious impacts by predation on streaked shearwaters (Calonectris leucomelas) that were breeding on this island. The population of the invasive rats, Black rat (Rattus rattus) and Norway rat (R. norvegicus) has increased on this island. It is important to understand the ecology of the invasive rats because they have become an alternative prey for feral cats and could possibly be the mesopredator in this ecosystem. However, there is no sufficient information on the ecology of these rats on this island. In this study, we established 8 trap lines across the island in 2017 and conducted a survey by capturing the rats in September, when shearwaters stayed on this island for reproduction, and in December, when shearwaters were absent. In September, Norway rats were captured mainly at low-altitude areas, whereas black rats were captured on a wide altitudinal range. In December, Norway rats occurred at both low- and high-altitude areas, whereas the number of black rats was lower at all trap line locations. Distribution and captured number per 100 trap-nights (CPUE) of these two rats changed spatially and temporally, and the pattern of changes was different between the two species. These results suggest that the two invasive rats have different ecological roles on Mikura Island.
Corral traps, which have a high capture efficiency, mobility, and level of safety, are required for capturing sika deer (Cervus nippon). We developed two types of small corral traps (1.8 × 4.4 m), one with an analog scale (AN) and the other with a digital weighing machine (DI). These traps were used to capture free-range sika deer from January to March, 2015, and January to February, 2016, in a natural forest of Hokkaido, Japan. A total of 17 deer (6 female adults, 8 female fawns, and 3 male fawns) were captured via the small corral traps during 10 trapping occasions. We captured multiple deer simultaneously 7 out of the 10 times. The efficiency of the AN was 0.136–0.167 deer per trap-day, while that of the DI was 0.444 deer per trap-day. The mortality of the deer captured during the study period was 0%. The labor required for setting-up the AN was 7 hours by two/three workers, whereas that for the DI required 10 hours by three workers. During the severe winter season, the 12 V batteries that were used worked effectively for more than 6 days below freezing point.