by Nichole Shelmidine
The Turtle Survival Alliance partners with the Wildlife Conservation Society on a number of conservation projects globally. We are excited for their recent success in breeding Chinese big-headed turtles, a species that is notoriously difficult to reproduce in captivity. Their guest post below details this accomplishment, which can also be read about in a recent issue of Zoo Biology.
Chinese big-headed turtles (Platysternon megacephalum) are Southeast Asian freshwater turtles endemic to Cambodia, China, Laos, Myanmar (Burma), Thailand, and Viet Nam. They inhabit cold temperature fast-moving, rocky, mountain rivers or streams and are considered taxonomically monotypic (family Platysternidae). In comparison to other freshwater turtles, two unique morphological features stand out: their extremely large head (from which their name is derived from) and their extraordinarily long tail in respect to body size. They are currently listed as endangered on IUCN’s Red List and as CITES Appendix II. However, continued pressures on wild populations – due to deforestation, construction projects along the streams that they inhabit as well as commercial harvesting has led recently to a proposal for them to be re-categorized to critically endangered on the IUCN’s Red list as well as to CITES Appendix I.
Successful long term captive propagation within US zoological institutions has not yet been established and this species is known to be difficult to propagate and incubate with only sporadic success in the private sector. Given these present concerns regarding the potential future of wild populations, in 2008 the Wildlife Conservation Society’s Prospect Park Zoo endeavored to take on the challenge of propagating this species in captivity. After five years the team’s efforts paid off when 5 big-headed turtles hatched between November 14-19, 2013 from a breeding pair consisting of a 14 year old female and 12 year old male. In addition, the program has had consecutive years of success with this same pair in 2014 & 2015, giving us a total of 13 hatchlings since the inception of the program.
The breeding pair is set up in an off-exhibit area that enables staff to manipulate environmental parameters such as ambient and water temperatures as well as photoperiod throughout the year. Each turtle is housed separately in a Waterland tub (female’s enclosure: medium waterland enclosure; 76”L x 35”W x 24”H & male’s enclosure: Small waterland enclosure; 55”L x 24”W x 12”H) that offers a well planted land area and an aquatic area with a water depth of about 10 centimeters. Each enclosure has its own chiller (Aqualogic Delta chiller) and a canister filtration system (Filstar XPS or Fluval), a basking light (Zoo Med 160W UVB) that is offered during non-hibernation periods (May to Oct) along with a UVB fluorescent strip light (Zoo Med UVB 5.0). The turtles are fed 4x a week during the spring/fall months and daily during the summer months depending on their weight. Additionally, once breeding season starts the female is placed on a calcium supplement until she has laid her eggs. The diet consists of red worms (Eisenia foetida), neonatal mice, super mealworms (Zophobas morio), greater wax worm moth larva (Galleria mellonella), live freshwater crayfish, live or cut up fish, shrimp and a formulated gel diet. Feeding is discontinued about 5 weeks before the hibernation temperature goal is reached.
The hibernation process starts the first week of November with ambient and water temperatures being decreased by 2 degrees every week until 8.9⁰C (48⁰F) water and 10.6⁰C (51⁰F) ambient temperatures are reached at which point the turtles will brumate. During the first week of April the process is reversed until a 22.2⁰C (72⁰F) water and 23.3⁰C (74⁰F) ambient temperatures has been reached. They have an 8-hour photoperiod during the winter months and a 12-hour photoperiod during the summer.
Breeding introductions begin the first week of May with the female being placed in the male’s enclosure daily for approximately 10-30 minutes depending on the level of male interest. Typically, the male would very slowly circle around the back of the female and then rush at her to mount her from behind. Once mounted the male grip her carapace with his front and back feet and tucking his tail underneath her shell. Copulations were as short as three minutes but as long as ten minutes and only two confirmed copulations were needed for the female to become gravid. Approximately one month post- copulation, staff could confirm that the female was gravid first by inguinal palpation and then via ultrasound. At this point, breeding introductions were discontinued.
Nesting behavior was observed about a week after the first copulation and staff began to observe the female spending more time on the land area digging and burying herself. Nesting substrate consists of an equal mixture of vermiculite, coco brick soil and fine grained sand. In most cases, the female was observed laying her eggs on land during the morning hours. Egg weights ranged from 9.50g to 11.922g and had an average length of 39.6mm and width of 21.4mm. Eggs were removed and set in vermiculite (1:1 water ratio by weight) and incubated at 23.3⁰C (74⁰F). Eggs were candled weekly. Banding of the eggs occurred within 24 hours and blood vessels could be observed around day 19. The incubation period ranged from 98-105 days. Hatchlings weighed between 8g to 10g and virtually all of their yolk sac had already been absorbed. The hatchlings were set up in acrylic tanks (2’ L x 1’ W x 6i” H) that were tilted at approximately 45 degrees in order to create dry and wet areas within the enclosure. Initially, the water level was about ½ inch and then slowly increased as the hatchlings grew.
This recent success will hopefully be only the beginning as the team at Prospect Park Zoo partner with the Bronx Zoo in breeding this dynamic species of turtle as part of the Wildlife Conservation Society’s global effort for turtle and tortoise conservation. Our hope is for repeated success with additional pairs of big-headed turtles and for increased interests in breeding at other facilities, so that a North American assurance colony may be established.
* Correspondence to: Nichole Shelmidine, Animal Department, Prospect Park Zoo, Brooklyn, NY 11225, USA, phone: 718-399-7339 x302, fax: 718-399-7337, e-mail: firstname.lastname@example.org
Photo Credits: Julie Larsen Maher ©WCS