Monitoring of the Reproductive Cycle in Captive-Bred Female Boa constrictor: Preliminary Ultrasound Observations

SIMPLE SUMMARY: In recent years, reptiles have become increasingly popular pets. The growing interest in snakes has led to an increase in captive-bred ophidians, and the Boa constrictor is one of the most common reptiles bred in captivity. These snakes can be found in tropical South America, as well as some islands in the Caribbean. With the exception of one subspecies, the Boa constrictor is now included in Appendix II of the Convention on International Trade of Endangered Species (C.I.T.E.S.). In order to achieve the proper management of boas in captivity, it is essential to have in-depth knowledge on the reproduction of this species and to identify minimally invasive methods for a correct monitoring of the reproductive cycle and gestation, guaranteeing the animal’s welfare. Currently, ultrasonography is the most common technique used in veterinary medicine for evaluating reproductive activity in both mammals and reptiles. In this regard, knowledge of the Boa constrictor is rather scarce. A group of captive-bred female boa constrictors were monitored by ultrasound over an entire breeding season. Results suggest that this technique allows an accurate monitoring of the captive female boas’ reproductive cycle, as well as a precise control of the embryos’ development and viability. ABSTRACT: The Boa constrictor is one of the most common reptiles bred in captivity. To achieve a successful breeding season, thorough knowledge of the females’ reproductive activity is necessary. In this regard, information on the Boa constrictor is still rather scarce. The aim of the present study was to monitor the ovarian activity and the embryonic development of boas by ultrasound. We performed brief scans on thirty non-anaesthetized snakes using a portable ultrasound system and a 7.5–10 MHz linear array transducer (Esaote MyLab™ Classic). Ultrasound features, dimensions, and echogenicity of the preovulatory and postovulatory follicles were determined. As gestation progresses, the postovulatory follicle size increases, and the embryonic silhouette becomes increasingly recognizable. During the second month after ovulation, by using color Doppler, early embryos’ heart activity could be evaluated. It is possible to highlight vascular connections between the mother and the membrane covering the embryonic structures. Ultrasound also allows one to identify follicular regression or slugs (nonfertilized eggs) early. The present study suggests that ultrasound could be an excellent noninvasive technique to evaluate the reproductive activity of Boa constrictor, allowing us to precisely identify the correct time for mating, monitor embryo development and viability, and allow the early diagnosis of follicular regression.