Abstract

There is a lack of reproductive information regarding the endangered Bornean earless monitor (Lanthanotus borneensis), including on how to determine its sex. The objective of this study was to identify sex in a zoo population of 10 healthy Bornean earless monitors as well as define the ultrasonographic appearance of sexually mature female ovaries. Morphometrics of this population, including snout–vent length, tail length, head length, head width, head height, length of the dentary, dentary height, and lower jaw width were recorded. In addition, coelomic ultrasounds under manual restraint were performed. Total follicles per animal (7.55 ± 2.06, mean ± SD), follicular volume (0.32 ± 0.20 cm³), and type of follicles (hypoechoic, vitellogenic, and laminar) were recorded for each female in the study population. Although morphometrics were not useful in determining sex, ultrasound was a reliable, noninvasive method for this species. In addition, baseline measurements regarding their ovarian morphology were determined that may be useful for future breeding and health assessments for this endangered species.