Dissertação de Mestrado Integrado em Medicina Veterinária ; The Sumatran rhinoceros (Dicerorhinus sumatrensis) is on the verge of extinction. Once found throughout Southeast Asia, it stands now with less than 100 individuals scattered mainly in three national parks in Sumatra. The IZW-Berlin has been collaborating with BORA/SWD through the use of advanced imaging and assisted reproduction techniques in wild-caught Bornean rhinoceroses (D. s. harrissoni) held at the BRS. Ultrasonographic examinations and reproductive procedures conducted between 2005 and 2015 in 2 male and 3 female rhinoceroses were retrospectively analysed in order to infer on reproductive condition and its evolution, outcome of procedures and impact of interventions. Furthermore, the study aimed at developing a detailed description of ultrasonographic findings and identify evidence to further elucidate on the estrous cycle of the species. A total of 17 working visits were included in the descriptive analysis with 56 reproductive assessments by ultrasonography, 8 semen collections by electroejaculation, 10 hormonal treatments, 1 artificial insemination, 5 oocyte collections, 3 intracytoplasmic sperm injections, 4 techniques for the removal of endometrial cysts and 1 hydrosalpinx aspiration. The detailed description of findings provides new technical information on numerous anatomical structures of both males and females, and constitutes the first report of various procedures in the species. Notably, several hypotheses are considered and put forward for future investigation. Results revealed that no animal suffered negative consequences from the repeated and sometimes invasive interventions. While the older female was found to have entered early reproductive senescence, the two young females were reproductively active but showed a severely impaired reproductive tract, namely affected by endometrial cystic hyperplasia and uterine leiomyomas. These findings were associated to the phenomenon of asymmetric reproductive ageing and a presumptive ...