Mammal Study

Although counting cementum annuli of lower incisor is a reliable method for age estimation in cervids, it inevitably involves the destruction of specimens. Here we studied the relationship between cranial suture closure patterns and age to test the possibility of cranial suture closure as a non-destructive age indicator in sika deer (Cervus nippon) specimens from Kinkazan Island, Japan, for which extensive life records were available. A strong positive relationship between the sum of suture closure level scores and age was found. We found that this relationship was even stronger than the relationship between age and the crown height of the first molar, which is frequently used for non-destructive age determination. Our study highlights the potential of cranial suture closure as an alternative valid tool for age estimation.

We investigated the genetic structure among populations of the Ryukyu wild boar (Sus scrofa riukiuanus) on Tokunoshima Island by analyzing DNA from modern and archaeological samples. Four and two mtDNA haplotypes were found in the modern and archaeological samples, respectively. One haplotype was shared between the modern and archaeological samples. Of the seven haplotypes, four were only found on Tokunoshima. These haplotypes were genetically close to each other and classified as those from the Ryukyu wild boars. This genetic similarity between modern and archaeological samples suggests that these four haplotypes originated from Tokunoshima. The chronology of the archaeological samples suggests that the genetic structure of the wild boar population on Tokunoshima has been maintained for over 1000 years. The representative glucosephosphate isomerase-processed pseudogene (GPIP) allele for the modern population on Tokunoshima was GPIP*3a and was found in a Ryukyu wild boar in a previous study. We detected three modern individuals that were genetically distinct from the Ryukyu wild boars based on mtDNA and GPIP analyses. They all had a different combination of the mtDNA haplotype and GPIP allele from each other. Our results indicate that gene flow events from pigs to wild boars have occurred on Tokunoshima.

Deer can strongly affect other species as a keystone species. The intensity of their herbivory impact on forest vegetation is suggested to be affected by not only deer density but also by other environmental factors such as landscape components. Especially, artificial grasslands such as pastures and meadows possibility affect deer impact on forest vegetation by altering deer foraging behavior. Therefore, we aimed to clarify the effect of presence/absence of artificial grasslands on impact by sika deer (Cervus nippon) on forest vegetation. We compared the occurrence of debarking and the coverage of understory vegetation in two adjacent regions under similar deer density with and without artificial grasslands in Yamanashi Prefecture, Japan. The occurrence probability of debarking was more severe in forests in abundant artificial grassland region than in no artificial grasslands region despite considering the effects of deer density, tree size, and tree species. In contrast, the coverage of understory vegetation was high in abundant artificial grassland region than in no artificial grassland region despite considering the effects of light condition, vegetation type, and deer density. In conclusion, artificial grasslands modify deer impact on forest vegetation by increasing the occurrence probability of debarking but decreasing the browsing pressure on understory vegetation.

Dental microwear texture analysis (DMTA) can be used to quantitatively evaluate tooth surface roughness and has been used to distinguish herbivorous ungulates according to interspecific dietary differences among grazers, browsers, and mixed feeders. Moreover, DMTA has been applied among local populations with intraspecific dietary variation. In general, the tooth surfaces of grazing species/populations are rough, whereas those of browsing species/populations are smooth. Whether DMTA can be used to detect dietary differences among sympatric species is of interest. In the present study, we aimed to use DMTA to explore interspecific differences in diet between two ruminants in Japan—the sika deer and Japanese serow in Nagano Prefecture. We found significant differences in surface roughness parameters between deer and serow. The tooth surfaces of the deer were more undulated with parallel scratches, whereas those of the serow were smoother with pits. These results indicate that the deer consumed abrasive graminoids more frequently than the serow, which is in accordance with previous dietary analyses. However, the two species did not segregate dichotomously but showed a huge overlap in DMTA parameters, implying dietary overlap. The present study shows the potential of DMTA to clarify the foraging ecology of sympatric ruminants from skeletal specimens.

Human-sun bear conflict may negatively affect human properties and long-term survival of the sun bear. These conflicts become a major problem for conservation of the sun bear. Understanding what factors cause human-bear conflict remains poorly understood. Studies of conflict extent through identifying affected areas while accessing their level of risk are a prelude to reduce wildlife conflict issues. In this research, the Maximum Entropy (MaxEnt) algorithm was applied to predict potential conflict areas of the Malayan sun bear (Helarctos malayanus) in Peninsular Malaysia and identify the key factors shaping conflict distribution. The 233 spatially disperse conflicted sun bears were analysed in relation to 11 predictor variables. The risk model demonstrated that approximately 1% of Peninsular Malaysia was comprised of high potential conflict area, while good, moderate, and least potential conflict areas constituted 2%, 5%, and 25%, respectively. The predictive model with an AUC value of 0.92 indicated that the crop areas adjacent to the forest edge and with high precipitation were significantly influenced on sun bear conflicts. This study provides useful tools for identifying potential conflict hotspots and highlights the significance of proper landscape planning to improve the mitigation of human-sun bear conflict and conservation efforts throughout Peninsular Malaysia.

Studies on odontocetes (e.g., porpoises) have revealed that these animals may adaptively use vision. The present study examined the contributions of vision to the approaching behavior of the harbor porpoise (Phocoena phocoena). When a porpoise approached a target, the time-to-contact perceived by the animal and its trajectory with a visual impediment condition were compared with those in the control (no impediment) condition. The results suggested that approaching behavior to a stationary target was guided by the animal's evaluation of time-to-contact (τ), maintaining the time derivative of τ () at a constant value. A porpoise with visual deprivation exhibited grater τ value and a longer evaluation time before contact than a porpoise that was not blindfolded in the task of reaching for the target. Furthermore, the porpoise with a visual impediment changed its swimming trajectory toward a target less than the control, which appeared to adaptively adjust its approaching trajectory. These findings imply that the use of vision aided echolocation and enables precise control and alteration of the trajectory during the approach. The present study has implications for adaptive use of vision during approaching behavior in the harbor porpoise.

Otters are thought to be extinct in Japan, although they were widely distributed there until the early 20th century. Records of otters on Tsushima Islands, located between Kyushu and the Korean Peninsula, were found only in two sources from about 1735 and 1809, and there has been no evidence of their existence since the middle of 19th century until now. We set infrared trail cameras to monitor the Tsushima leopard cat on the northern island of Tsushima. Otter(s) were recorded by these cameras four times, on February 6 and July 16, 2017 in the Tanohama area and on October 1 and 3, 2017 in the Sago area of the island. This is the first record of an otter in Japan since the last record was made in Kochi Prefecture in 1979. The otters recorded on the islands could not be identified to species level based on the footage feed from the trail cameras. Based on historical information about otters in Tsushima and the surrounding areas, the origin of the otters is thought to have been natural dispersal from the Korean Peninsula, the nearest habitat of the Eurasian otter.