Mammal Study

We examined the morphology of the male genitalia of six Muridae and five Cricetidae in the Muroidea focusing on the medial and lateral bacular mounds, as well as their ossification patterns to discuss the diversity and the movement mechanism of the trident structure. All examined species possessed a medial bacular mound and two lateral bacular mounds, which collectively formed a trident structure. In the Muridae species, the medial bacular mound was ossified or consisted of cartilage, while the lateral bacular mounds were composed of soft tissue. By contrast, both the medial and lateral bacular mounds were ossified in the Cricetidae species. Among the Muridae species, the medial bacular mound was well developed, and the lateral bacular mounds were small in Mus and Micromys species while the medial bacular mound was highly developed, and the lateral bacular mounds were developed in Apodemus speciosus. Different combinations of developmental characteristics of the medial and lateral bacular mounds produced variation in the glans penis morphology. Histological examination of A. speciosus and Craseomys rufocanus suggested that the movement of the lateral bacular mounds was driven by blood flowing into the cavernous space, and the movement increases the cross-sectional area of the glans penis.

A female pantropical spotted dolphin (Stenella attenuata) successfully mated with a mature male in captivity on April 13, 2017. This mating event was followed by an evaluation of the plasma progesterone concentration, appetite, and rectum temperature of the dolphin during pregnancy. We recorded the progesterone profiles during pregnancy, the gestation period, and the parturition events. The progesterone level (ng/mL) ranged between 0.7 and 133.4 (n = 27), and the average was 45.1 (SD = 38.5). Immediately after mating, extremely high progesterone levels were observed, which showed a decreasing trend towards the parturition day. The gestation period was 352 days. On the morning of the parturition day on March 31, the female displayed symptoms such as a drop in rectal temperature by approximately 1°C and reduced appetite. The time from the first observation of vaginal discharge to the fluke's appearance was 5.5 hr, while the subsequent period until birth was 4 hr in length. The time from parturition to the first successful nursing was approximately 4 hr, while the time from the nursing to the placental passage was less than 1 hr. To the best of our knowledge, this is the first report on the pregnancy period of pantropical spotted dolphins in captivity.

In this study, we aimed to determine the daily activity patterns and seasonal activity variations of the Eurasian lynx in different habitats (forests and open lands) in a geographical region where there are relatively few data on its ecological characteristics. Survey effort totaled 10 102 camera trap days, with 24 camera trap stations covering an area of approximately 650 km². Our results showed no significant differences in the habitat preference of the lynx throughout the entire study area or between seasons. The crepuscular and nocturnal activity preferences of the lynx were similar to those of the wolf, red fox, and the European hare. The lynx's daily activity pattern peaked during 20:00–22:00 and 04:00–06:00 hours, and did not show significant variation between seasons. Kernel density estimation was used in order to reveal the temporal overlap of other carnivore and herbivore species with the lynx. The highest temporal overlap (coefficient of overlapping: 0.90) was seen with the European hare. Our findings also indicated higher temporal overlaps with the wolf, red fox, wild boar, and brown bear, and lower overlaps with the red deer, Southwest Asian badger, and Martes spp., which improved understanding of their interactions and co-existence with the lynx.

The taxonomy and phylogeny of the subgenus Mus, the Eurasian lineage of the genus Mus, remain unresolved, even for the house mouse (Mus musculus). While the subgenus is diverse in Asia, few studies cover both its morphology and molecular phylogeny. We re-examined 70 specimens identified as M. cervicolor that were collected from central Nepal in 1968 and 1975 and are currently deposited in the Hokkaido University Natural History Museum. To compare morphological features, we examined skull geometric morphometrics and body coloration, and performed a phylogenetic analysis of the mitochondrial cytochrome b gene sequences of representative specimens. The specimens were most likely either M. booduga or M. musculus. The best morphological characteristics for distinguishing the two species were the nasal length ratio, which was high and low, respectively. Mus booduga was found to inhabit altitudes lower than 1000 m and have light ventral fur, while M. musculus inhabited various altitudes up to 3000 m and had variable fur color depending on the altitude. We also discuss the taxonomic status of the fawn-colored mouse M. cervicolor.

Dental anomalies in the greater Japanese shrew mole Urotrichus talpoides Temminck, 1841 (Eulipotyphla: Talpidae) were examined, based on 1001 specimens. We followed the dental formula of U. talpoides I 2/1, C 1/1, P 4/3, M 3/3 = 36, which is adopted by the most recent Japanese researchers, and found dental anomalies in 17 specimens involving 12 instances of absent tooth, four of extra tooth, and one of connate tooth. Of these, the following dental anomalies are reported in U. talpoides for the first time: extra tooth posterior to the upper canine (C¹), extra tooth posterior to the upper second premolar (P²), extra teeth on the inner sides of the upper fourth premolars (P⁴), and connate tooth on the lower canine (C1). The most frequently observed dental anomaly was the absent tooth on C¹ (52.9%), whereas the others were not common (< 11.8%). Our results indicate that dental anomalies in U. talpoides in Urotrichini possess the different pattern from those in species in Scalopini and Talpini. On the other hand, alternative hypothesis of dental formula I 3/2, C 1/1, P 3/2, M 3/3 = 36 explains the observed anomaly pattern in line with the general trend of dental anomalies in Talpini and Scalopini.

The generic name of the humpback whale, Megaptera was named after their forelimb, which means a “large wing”. New whale remains (specimen number: OMNH-QV 60) including the right scapula, humerus, and radius from the Namba Formation, Holocene in Osaka, Japan is reported as a humpback whale, Megaptera novaeangliae based on diagnoses of the species; having reduced acromion and coracoid processes of the scapula, and long humerus and radius. The body length of the individual can be estimated as 13 m based on the proportion between forelimb elements and body length. It suggests that OMNH-QV 60 is adult. The specimen is a certain record of Megaptera novaeangliae from Holocene sediments in Japan with size estimation.

Bangladesh holds 191 km² semi-evergreen northeastern (NE) forests where systematic camera-trapping has never been carried out. An effort of 587 trap nights in Satchari National Park, a NE forest, revealed ten carnivores, two ungulates, two primates, two rodents, and one treeshrew (12 threatened in Bangladesh; of which three globally threatened; dhole and northern treeshrew were new discoveries). Pairwise circadian homogeneity, coefficient of temporal overlap ( ), and spatial cooccurrence pattern were measured. High values ( > 0.75) were noted in 36 pairwise comparisons, and positive spatial association (Pgt < 0.05) in five. Anthropogenic activities overlapped with diurnal species (0.65 ≤ 1 ≤ 0.88) but stood dissimilar (P < 0.05 in the Mardia-Watson-Wheeler test) except for yellow-throated marten–livestock movement (1 = 0.70). Although species-specific dietary or temporal preference explains the observed associations, low detection of the jungle cat (2) compared to the leopard cat (56), absence of the fishing cat, homogenous activity (P > 0.05) in yellow-throated marten–crab-eating mongoose (1 = 0.83) and rhesus macaque–pig-tailed macaque (4 = 0.93) pairs need further research. These insights are remarkable as NE forests, the western cusp of the Indo-Burma biodiversity hotspot, are contrarily deemed ‘empty’, receiving least scientific investments.

Hibernation (denning) is an important aspect of the life history of Asian black bears (Ursus thibetanus), and denning chronology can be influenced by biotic and abiotic factors. We investigated activity patterns during the pre-denning period of Asian black bears using statistical process control in combination with activity sensors to quantitatively identify a marked reduction in activity from 2006 to 2017 in the Ashio–Nikko Mountains, Japan. Pre-denning activities were detected in 29 of 35 cases (83%), with an average duration of 2.7 ± 1.7 days, which is one to three days shorter than the duration for brown bears (U. arctos). The effect of bear's age, sex, and the abundance of hard mast on the duration of pre-denning were not significant.