Fecal and blood concentration of estradiol-17β(E₂) and progesterone(P₄) were measured in 2 female, adult Japanese red foxes (Vulpes vulpes japonica) kept in a zoo. As the result, the blood E₂ level recognized the peak only 1 time in January, and it rapidly decreased afterwards. Blood and fecal P₄ level increased rapidly in conjunction with blood E₂ level, and maintained relatively high level for about 2 months after a sharp peak and gradually decreasing. The swelling of the vulva would be recognized in the end of January in which there was the rise in blood E₂ value, and it continued for about 1 week. In addition, the swelling of the mammary gland would be observed in the end of February, and the depilation around the mammary gland would be observed in the beginning of March. After that, secretion of milk-like liquid was observed. From the hormonal dynamics, it was confirmed that the Japanese red foxes had the same characteristics as other canids such as that it was monoestrus and that the luteal phase continued as in the pregnancy regardless of pregnancy and non-pregnancy. In addition, from the latter half of the P₄ level rise period, behavior similar to pseudopregnancy seen in dogs was observed, suggesting that pseudopregnancy may also be seen in Japanese red foxes. On the significance of the pseudopregnancy of foxes, the relevance to the helpers in rearing cubs was considered.

Sterilization using radiation has been widely employed to control insect pests. The effectiveness of the method relies on preventing the production of viable offspring after copulation. In this study, we attempted to produce sterile male lizards using this method. Swinhoe’s tree lizards (Diploderma swinhonis) are native to Taiwan and are regarded as an invasive alien species in Japan. We irradiated male lizards captured in Miyazaki Prefecture, Japan, with γ-rays and examined whether irradiation induced permanent sterility. The lizards were irradiated with 5, 10, and 15 Gy as air-absorbed doses and were dissected one month after irradiation. Two additional groups were prepared; one group was dissected at three months after a single dose of 10 Gy, and the other group was dissected at four months following two doses of 10 Gy. All lizards were euthanized and their testes were removed to evaluate the histological change of testes. Testicular atrophy and damage to spermatogenic epithelium were observed in all lizards at one month after irradiation. However, the regeneration of spermatogenic epithelium was observed in lizards that were kept for more than three months, and permanent sterility could not be induced. The mortality rate for lizards irradiated with 15 Gy was high, suggesting high-dose irradiation is unsuitable for sterilizing this species. Compared to lizards that were irradiated once, the spermatogenic epithelium of lizards that were irradiated twice did not regenerate, indicating that repeated irradiation is effective for inducing permanent sterility in this species.

Elephant endotheliotropic herpesvirus （EEHV）, which is recognized as the cause of fatal hemorrhagic disease in young Asian elephants, has caused many deaths in human managed and wild elephants worldwide and has become the leading cause of death in Asian elephants in the last 20 years. To date, researchers from around the world have been working to protect Asian elephants from EEHV, which is naturally hosted by elephants and infected latently like other herpesviruses. It causes fatal hemorrhagic disease in young elephants when blood levels of the virus rise abnormally for some reason. Although the response to treatment after the onset of the disease is poor and effective treatment has not yet been established, aggressive treatment in the early stages of the disease has been shown to improve the survival rate. Therefore, early diagnosis and early treatment by establishing a routine inspection system are required in Asian elephant managers.

Capybara （Hydrochoerus hydrochaeris） kept at an animal exhibition facility presented anorexia and wobble of hind limbs, and died. Blood test showed anemia and hyperproteinemia. Gross necropsy examination revealed swelling heart and kidneys, and a free mass in the uterus. Histopathological examination demonstrated infiltration of plasmacytoid tumor cells into heart, liver, kidneys, and adrenal glands. The mass in the uterus was diagnosed as a leiomyoma composed of spindle-shaped cells. Based on these findings, the case was considered to have died due to plasma cell neoplasm and uterine necrosis caused by uterine fibroid.

Trematodes of the genus Dicrocoelium are one of the most common parasites of ruminant animals, but their lifecycles are unclear in Japan; however, sporocysts of D. chinensis were found for the first time in this country. In this study, snail survey was carried out at a location of high-level infection of sika deer in Gifu Prefecture, Honshu Island in autumn. The authors in that study found immature sporocysts in the hepatopancreas of the land snail Aegista vulgivaga, and identified as D. chinensis based on DNA barcoding. The result indicated that this snail has potential as the first intermediate host of D. chinensis at this location, and suggested that A. vulgivaga is important for the control of dicrocoeliasis in livestock in Japan. This manuscript provides the background and summary of research described in Waki et al..