Mammal Study

Several statistical models have recently been developed to estimate animal density using camera trappings without individual animal recognition. However, most models assume that detection by camera traps of animals passing a specific area of the camera view is perfect. A recently developed REST model ( Nakashima et al. 2018 ; Journal of Applied Ecology 55: 735–744) also depends on the trapping rates and staying times within a specific area. We tested whether commercial camera traps provided unbiased estimates of these parameters by conducting an experimental trial using a domestic dog in a city park in Japan. Additionally, we tested the effects of camera angle on the estimation of these parameters using the Bushnell camera. The Bushnell camera captured the dog 96% of the time, while the Ltl-Acorn camera missed about half of his passes. The staying time was underestimated by 4% using the Bushnell and overestimated by 25% using the Ltl-Acorn camera. The bias in density estimation was < 10% using the Bushnell camera. Camera angle did not affect detection probability, while the downward-angled cameras underestimated staying time due to the delayed trigger. We hope to share the results with manufacturers to make camera traps more suitable for animal density estimation.

Self-sustained populations of captive red panda were challenged by low reproductive success rate. Defining the different types of testicular cell and increasing the knowledge of male fertility was critical for the improvement of reproductive efficiency in red panda captive populations. Here, we firstly report the histological structure in red panda testes at various ages. Besides, our data also showed that markers for red panda testicular cells including ITGA6, PLZF, THY1, VASA, DAZL, GATA4, VASA, and αSMA were expressed in adult testis tissue. To further examine the localizations of ITGA6, VASA, VIM, and αSMA, the immunohistochemical analysis was performed and the result showed the typical staining patterns of undifferentiated spermatogonia, multiple types of germ cells, Sertoli cells, and peritubular myoid cells (PMCs), respectively. For the testicular tissue digestion, two-step enzyme digestion was used to obtain the cell suspension. The red panda Sertoli cells, expressing Sertoli cell marker VIM, were cultured and conserved in this study, which can be used for red panda Sertoli cell establishment and as the feeder cells for red panda spermatogonial stem cells (SSCs) growing.

In this study, we examined a genetic variation of killer whales, Orcinus orca, from off the coast of Hokkaido, Japan, by sequencing the D-loop and cytochrome b (Cyt-b) regions of the mitochondrial genome. Three D-loop and two Cyt-b haplotypes were identified from eight skin biopsies. These five haplotypes had been previously deposited at GenBank and the International Nucleotide Sequence Database Collaboration (INSDC). Two D-loop and one Cyt-b haplotypes were consistent with the marine mammal-eating “Transient” ecotype previously reported in Japanese waters. One D-loop and one Cyt-b haplotypes were identified as the fish-eating “Resident” or “Offshore” ecotype that is the first record of this ecotype in Japanese waters. Our study showed that different ecotypes exist in Japanese waters, contributing to the conservation and management of killer whales.

The feeding behaviours of the Sulawesi babirusa (Babyrousa celebensis) in terms of its preference to eat the mesocarp, or husk, of immature coconuts (Cocos nucifera) and the feeding marks on leftover coconuts were observed. Additionally, to explore the physicochemical factors behind this preference, a comparative study was conducted on the basal and apical parts of the coconut mesocarp. The breaking load, macronutrient content, and volatile compounds were examined. The findings were as follows: 1) Babirusas always sniffed the cut surface of the coconut before eating. They then scooped out the basal part of the mesocarp where the fibres are more visibly scarce with their mandibular incisors and ate more than 7.6 times the surface area at this end than at the apical end. 2) The preferred basal part of the immature mesocarp had a lower breaking load. 3) The gas chromatography-mass spectrophotometry (GC-MS) chromatogram of the basal sample showed larger peak areas for 2-methylbutanal and 3-methylbutanal. In conclusion, the babirusa preferred the basal part of the immature coconut mesocarp, and the preferred basal part had distinctive features in terms of hardness and volatile profile, which is probably characterised by the presence of 2-methylbutanal and 3-methylbutanal.

The sika deer population on Yakushima Island exhibits high genetic diversity despite the small size of the island. We hypothesized that the high genetic diversity of the population had been maintained by the population structure, which included several subpopulations among which gene flow was limited. To test this hypothesis, we analyzed the spatial genetic structure of the population using 12 microsatellite loci. Two and four subpopulations were detected by STRUCTURE (stN and stS) and GENELAND (glN, glE, glS, and glW) software, respectively. The basic genetic structure assigned by STRUCTURE was supported by GENELAND, while stN and stS were further separated into two subpopulations (glN and glE; glS and glW, respectively) by GENELAND. All pairwise genetic differentiations between the two and four subpopulations were significant. These results demonstrated that the Yakushima population was structured into genetically distinct subpopulations. Although the location of the western boundary between stN and stS corresponded with a large river, no landscape or biological feature could be identified for the eastern boundary. We discussed the relationships between the genetic structure and management units designed by the local government and concluded that the Yakushima population should be managed based on their spatial population structures considering multiple time scales.

Quercus acorns and coniferous cones are the main food sources for tree squirrels, and the chemical contents of seeds, such as tannins and terpenes, are predicted to affect the squirrels' food preference. The tolerance of squirrels to chemical contents may vary between species that have evolved in different environments. The consumption of artificial food containing tannic acids or terpenes were compared between the endemic Sciurus lis and two alien species, S. vulgaris and Callosciurus erythraeus. Sciurus lis ate foods containing up to 4% tannic acid, whereas S. vulgaris and C. erythraeus ate foods containing 8% tannic acid. Sciurus lis and S. vulgaris could eat food containing a high concentration of terpenes (up to 0.3% α-pinene and 2% limonene), whereas the food consumption by C. erythraeus decreased drastically with increasing terpene concentrations. The two alien squirrels are highly resistant to tannins and thus the acorns of most Quercus species may be available for them. Sciurus lis exhibits a lower tolerance to tannins, but can consume foods with high concentrations of terpenes, suggesting a strong adaptation to coniferous forests, but not to Quercus forests. More attention must be paid to conserving suitable habitats for S. lis, an endemic relict species.

Native sika deer (Cervus nippon) had not been observed in and around Sasebo City, Nagasaki Prefecture, Kyushu, Japan. However, deer have recently been confirmed in this area, and the number of individuals and the range have been expanding, causing damage to forestry and natural vegetation. Although the origin of these deer is unknown, it may be derived from Formosan sika deer (C. n. taiouanus), which is listed as an invasive alien species in Japan. There is concern about hybridization between this subspecies and the native Japanese sika deer. In the present study, we used genetic methods to assess the current status of the deer in the Sasebo area of Nagasaki Prefecture, particularly its origin and hybridization. Our study showed that the deer did not originate from Formosan sika deer, and we found no evidence of hybridization. The deer in the Sasebo area were found to have a haplotype included in the southern Japanese sika deer lineage. The current study was unable to identify the specific origin of the deer due to limitations in PCR-RFLP and mitochondrial DNA sequencing analysis.

Infanticide, the intentional killing of conspecific infants, has been observed widely in mammals, including squirrels. Several ground squirrels revealed this behavioral anomaly, yet no report has been published on the flying squirrels. We report an observation of killing an infant of the particolored flying squirrel (Hylopetes alboniger) by a conspecific adult intruder in Satchari National Park of northeast Bangladesh. Among the several adaptive explanations for infanticide, our observations point to sexual selection in males that confers a competitive advantage by making females receptive. However, the resource competition hypothesis, where the intruder's offsprings gain access to resources as a result of the infanticide cannot be ruled out. Extensive studies are needed to document the extent of infanticide in flying squirrels and their adaptive significance.