INTRODUCTION AND OBJECTIVES

Ultrasonography was used as early as the 1950s to characterise soft tissues in humans, and today is used routinely in human and veterinary medicine in the areas of ophthalmology, cardiology, neurology, nephrology, gynaecology and andrology, obstetrics, organ transplantation, oncology, orthopaedics and dermatology. It is somewhat surprising then that ultrasonography has received so little attention in zoo and wildlife medicine (see review, Hildebrandt & Göritz, 1998). Furthermore, although the number of investigations has increased recently, the focus remains on mammals (69%) with less emphasis on reptiles (19%), birds (12%), fish and amphibians (<1%) (Göritz, 1996).

Reproduction in many zoo-held animals is poor, and infertility caused by physiological disorders or mismanagement prohibits creating selfsustaining populations. Because of limited knowledge of species' reproductive anatomy and physiology, techniques to determine sex, sexual maturity, reproductive tract morphology, the reproductive cycle itself and gestation and foetal growth are critical to successful ex situ reproduction and management. This is an exciting time because ultrasonography is finally finding a niche in the study and management of rare wildlife species. Since 1993 we have conducted thousands of ultrasound examinations in more than 100 species, often in collaboration with reproductive biologists, theriogenologists and pathologists. The aim of this chapter is to describe some of our experiences in the use of ultrasonography as a powerful tool for assessing reproductive fitness of captive and free-living wildlife species.