Courtship And Mating Behavior In The Big-headed Turtle(platysternon Megacephalum)

Mating behavior is an important part of species’ responses of breeding which is an important link in life history of animals. The success of mating behavior is related to the continuation and the diversity of species. Reptiles were the first to be on land in vertebrate and had a special status in animal evolution.Whether they can successfully be on land depends on the success of breeding. So the intensive study about breeding appears important.The Platysternon megacephalum, a single specialty in Asian, has important scientific and economic value. This species is currently endangered. Due to commercial harvesting, trade for medicinal purposes and as pets, and habitat destruction. At present the research about reproductive ecology have not been reported because the population resource is limited and field observation is difficult. Captive breeding is an important approach to turtle conservation. Establishing captive populations can decrease the risk of extinction. The reason why the captive breeding cannot success is the barrier of the mating behavior. So we conducted a study on the courtship and mating behavior and its seasonal changes in P.Megacephalum in order to make up the blank of the reproductive ecology of this species. It has a important significance to comprehensively understand the ecology habitat of the species.It has a important significance to comprehensively understand the ecology habitat of the species and provides scientific basis for the captive breeding of this endangered species.The study lasts from March to November 2014 in the Xiangtoushan national nature reserve in Guang Dong(an animal research station of the South China Institute of Endangered Animals). The courtship and mating behaviors of P. megacephalum were recorded in the artificial simulation habitat through using video-recorded approach and the data was analyzed by film analysis technology. A total of 185 pairings(from a pool of 25 males and 25 females,all sexually mature) were selected for behavioral observation, of which 66 pairings(12 males,24 females) exhibited courtship behaviors. From these 66 pairings, 259 courtship behavior sequences were analyzed. Males perform seven mutually exclusive motor patterns(approaching, sniffing, chasing, resting, mounting, subduing female, copulating) and females display three mutually exclusive motor patterns(fleeing, mating resistance, mating acceptance). The temporal sequences of courtship and mating behavior motor patterns were analyzed using Chi-square tests and Kappa analyses, from which a flow diagram of the courtship and mating motor patterns in P. megacephalum was constructed. The flow diagram showed that approaching is the beginning of behavior of the courtship and mating, Thecourtship and mating behavior of P. megacephalum is divided into 3 stages including the courtship phase(AP�'SN�'CH), ready to mating phase(MO�'SF) and mating phase(CO�'SE). The duration of time of the AP, SN, CH, MO, SF and CO respectively are 11s、12s、13s、4s、19s and 139 s. The mail mating patterns of P. megacephalum is original and this is the first report of such courtship behavior in an Asian turtle species.Endocrine conditions have important effects on the courtship and mating behavior of turtles and the environmental conditions of captive breeding may cause the dyscrasia of the endocrine in turtles that an prevent the courtship and mating behavior. Testosterone and estradiol are known to be the key sex steroids regulating mating behaviors. Testosterone level is associated with male mating behaviors and while estradiol level is associated with female mating behaviors. Based on the observation of the species’ behavior, the mating intention of males could be divided 2 groups including the individuals that had no mating intention(showed no courtship or mating behavior) and the individuals that had(showed courtship or mating behavior, such as CH, MO and CO). The female mating intention also could be divided 2 and respectively were the individuals accepted mating and the individuals not accepted mating(females performed FL and MR in the progress of males courtship). This study captured urine after every mating experiments and used enzyme-linked immunosorbent assay(ELISA) made in north biotechnology research institute in Beijing to detect the levels of testosterone in males and the levels of estradiol in females. The study collect a total of 237 samples of urine including 118 of males and 119 of females. The results of this study showed that:(1) The testosterone levels in the male induviduals that had mating intention were significantly greater than the individuals had no mating intention(non-parametric test,P<0.05). There were no significant differences between the 2 groups that had different mating intention(non-parametric test, P>0.05).(2) The levels of testosterone and estradiol showed seasonal changes to some degree. The levels of testosterone in April significantly higher than the levels in March, May, June, August and October(P<0.05). There were no significant differences of the levels of testosterone between the rest each month(P>0.05). The levels of estradiol in April and July were significantly greater than the levels in March, May, June and November(P<0.05). There were no significant differences of the levels of estradiol between the rest each month(P>0.05).(3)There was a long mating period exists from March to November with April being the peak mating month(63.64%).(4) High testosterone levels in males are the key initiators of successful mating. This study suggests that the best time for mating in big-headed turtles is April(shortly after hibernation).