| Nile crocodiles(Crodylus niloticus)and Siamese crocodiles(Crocodylus siamensis)have introduced breeding species for foreign countries in China.In this paper,we studied the reproductive biology parameters of Nile crocodiles and Siamese crocodiles introduced in Hainan,China,in order to analyze the suitability of introduced crocodile in southern China,and provide scientific basis for the legality of commercial use of crocodile under artificial breeding conditions in China.In this paper,the data for the eggs and young crocodiles(recently hatched crocodiles)of two introduced species were collected at a Sanya crocodile breeding farm in Hainan(with the National Forestry Administration's breeding license),a total of 1574 Nile crocodiles eggs,644 young crocodiles,2205 Siamese crocodiles eggs,and 588 young crocodiles were collected.The characteristic variables of crocodile eggs were statistically analyzed,obtaining a normal range of normal values for Nile crocodiles and Siamese crocodiles eggs in a new living environment.The normal range of the egg length of Nile crocodile is 7.57±0.41cm,the egg width is 4.52±0.18cm,the egg mass is 95.49±11.51g,the clutch mass is 3853.8±1177.86g,and the clutch size is 40.36±10.00,the average clutch mass is 94.66±10.65 g;the normal range of the egg length of Siamese crocodiles is8.01±0.29cm,the egg width is 5.01±0.17cm,the egg mass is 119.04±25.79g,the clutch mass is 4665.2±928.2g,and the clutch size is 39.38±7.18,the average clutch mass is118.47±8.23 g;Through partial correlation analysis,and the results indicated that:There is a strong positive correlation between egg length and egg mass of Nile crocodiles(R~2=0.707,P<0.001),and there is a strong positive correlation between egg width and egg mass(R~2=0.664,P<0.001);There is a strong positive correlation between egg length and egg mass of Siamese crocodiles(R~2=0.504,P<0.001),and there is a strong positive correlation between egg width and egg mass(R~2=0.683,P<0.001),regression analyses were used to develop the linear equation between the egg length,egg width and egg mass.At the same time,it was found that the weight of young crocodiles and the egg mass of Nile crocodiles were strongly positively correlated(R~2=0.963,P<0.001);there is also a significant correlation between the weight of young crocodiles and egg mass of Siamese crocodiles(R~2=0.944,P<0.001).The linear equation for assessing egg mass and initial weight of young crocodile was developed for regression analyses.There was no significant relationship between clutch size and egg characteristics(P>0.05).Mating time of the Nile crocodile in Hainan(March-May)and the spawning season(August-October)are significantly earlier than in the Zimbabwe region of origin.Under artificial breeding conditions,the average of clutch size(47eggs/clutch)and the mean size of eggs(105g)for Nile crocodiles in their native habitat is greater than the introduced region as indicated by analyzing data using a two-sample t-test.Although the Siamese crocodile has a spawning time similar to its origin,but the size of clutches and the mean size of eggs in the introduced region were greater than in their native region as indicated by results using a two-sample t-test.At the same time,whether it is a Nile crocodiles or a Siamese crocodiles,its hatching rate is significantly higher than that of its origin under artificial breeding conditions(P<0.05).It shows that the Nile crocodiles and Siamese crocodiles introduced in Hainan can breed well.The breeding characteristics of Siamese crocodiles are even better than their original habitat.This result provides a scientific basis for commercial use of these two crocodiles in China. |
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