Endoscopic sexing in turtles and tortoises: 467 cases (2007-2017)

BACKGROUND

This multi-institutional retrospective study evaluated the feasibility and safety of endoscopic sex identification in 467 turtles and tortoises, representing 10 species.

METHODS

Medical records of turtles and tortoises that underwent endoscopic sex identification at the University of Georgia, New England Aquarium and Turtle Conservancy were reviewed for presurgical management, anaesthesia, endoscopic equipment and surgical techniques, endoscopic results and complications.

RESULTS

The majority of animals weighed less than 200 g, were fasted and anaesthetised using an injectable combination of ketamine, dexmedetomidine and morphine or hydromorphone, supplemented by local lidocaine at the prefemoral site. Anaesthetic reversal using atipamezole alone or in combination with naloxone was routine. For uncomplicated procedures, mean total anaesthesia, surgery and recovery times were 22, 4 and 18 minutes, respectively. All animals were placed in lateral recumbency for a prefemoral endoscopic approach to the coelom using a rigid telescope and sterile fluid infusion to visualise the gonads. Sex identification was definitive in 99.4% (n = 464) of the animals. Iatrogenic bladder perforation was the most common complication (n = 5), which necessitated extended anaesthesia and surgical time for repair. Only a single anaesthetic-related death was reported, which was associated with human error and drug overdose.

CONCLUSIONS

This is the first large-scale study to retrospectively evaluate endoscopic sex identification in multiple chelonian species. Results suggest that endoscopic sexing is a safe, accurate and practical means for sex identification in turtles and tortoises, and represents a valuable tool in their reproductive management.

FIELD ANESTHESIA AND GONADAL MORPHOLOGY OF IMMATURE WESTERN SANTA CRUZ TORTOISES (CHELONOIDIS PORTERI)

Evaluation of sex ratios is a critical component of chelonian captive breeding programs and may become increasingly useful to assess the demographics of free-living populations. In many reptile species, the sex of immature animals cannot be determined based on external features. Endoscopic sex identification is an accurate and safe method to identify the sex of immature individuals of some chelonian species. A number of studies describe this technique in controlled, hospital settings and report significant interspecies variations in gonad morphology; however, there are few reports describing this technique in field conditions. In the current study, the gonadal morphology of 40 immature Western Santa Cruz tortoises (Chelonoidis porteri) on Santa Cruz Island in Galapagos, Ecuador, was assessed. A previously described endoscopic protocol was used to perform sex identification under field conditions. Tortoises were anesthetized using an intramuscular injection of ketamine (10 mg/kg) and medetomidine (0.1 mg/kg), which provided an adequate plane of anesthesia. The medetomidine was reversed with atipamezole (0.5 mg/kg). Field conditions presented challenges such as limited control over lighting, suboptimal patient positioning, and restricted power supply for endoscopy equipment. The immature testicle in Western Santa Cruz tortoises was oval, reddish pink, and tightly adhered to the coelomic membrane ventral to the kidney. The surface of the gonads resembled other species with the notable exception that the ovaries lacked a significant number of primordial follicles. These gonadal characteristics were consistent, with only one individual identified as undetermined sex of the 40 samples. This field-based endoscopic gonadal evaluation was a safe and sensitive technique for determining the sex of free-living immature Western Santa Cruz Galapagos tortoises.

Head-started Agassiz’s desert tortoises Gopherus agassizii achieved high survival, growth, and body condition in natural field enclosures

We measured survival, growth, and body condition of 8 hatchling cohorts of desert tortoises Gopherus agassizii (living in predator-resistant outdoor pens in the Mojave Desert, California, USA) over 11 yr to evaluate head-starting methods. At 11 yr of age, 7 times as many of the first cohort had survived than if they had been free-living tortoises. Subsequent improvements in predator control, food and water supplementation, and pen structure increased survival from 7 to 10 times that under wild conditions in younger cohorts. Annual survival averaged 96%. Carapace length (CL) increased 6.95 mm yr-1, similar to that of free-living tortoises. Annual growth rates varied with calendar year (possibly reflecting food and water supply), age, cohort (year hatched), mother, and in 4 dry years, with crowding. Most of the first cohort grew to a releasable size (CL >100 mm) by their 9th year. Body condition indices remained high, indicating little dehydration despite droughts in 8 of the 11 years, because irrigation offered drinking opportunities. Head-started tortoises developed fully hardened shells (≥98% of adult shell hardness) earlier (10.1 vs. 11.6 yr), but at a larger CL (117 vs. 104 mm) than did free-living tortoises. Selective feeding in head-start pens decreased subsequent germination of favored wildflower species, apparently by reducing the natural seedbank. Consequently, we reseeded and irrigated each autumn to promote subsequent spring food supply. We irrigated in early summer to enable drinking and ensuing consumption of dry, dead plants and Bermuda grass hay, a supplement. These procedures can greatly improve juvenile survivorship, and increase numbers of hard-shelled, midsized juveniles to help augment wild populations.