no 



BULLETIN OF THE BUREAU OF FISHERIES. 



in such locations in the nursery house that direct sunlight fell upon them. Greatest 

 growth also occurs in those terrapins held closest to the heater, and therefore there 

 appears to be a direct relation between rapid growth and increased prevalence of the 

 disease. The mortality of winter-fed terrapins, as it has occurred during the period 

 from November of one year to March of the next since 19 12, is as follows: 



Mortality of Winter-fed Terrapins. 



Year. 



IQI2- 

 1913. 

 1914. 

 I9IS- 



Year. 



1916 

 1917 

 1918 

 1919 



Number 

 fed. 



2. 126 

 2.038 

 (") 

 2 937 



Mortality. 



Number. Per cent. 



227 

 554 



37 

 18 



" All terrapins of the rt>r8 brood were liberated. 



SUMMARY. 



The egg production and the hatch of the original and second Carolina and of 

 the Texas brood stocks during their captivity at Beaufort have been reviewed. It 

 appears that the probable average age of individuals of the two Carolina brood stocks 

 in 1921 is 28+ and 18+ years, respectively. Egg production in domestic terrapins 

 has occurred as early as the fourth year. In terrapins fed one or two winters egg pro- 

 duction generally begins in the fifth or sixth year. In hibernating terrapins it rarely 

 occurs before the seventh year. Egg production immediately after penning is small 

 but increases to normal in about the third year of captivity. At least for the first six 

 years of sexual maturity, probably for much longer, it is greater among the fed terra- 

 pins of a certain brood than among those of the same brood allowed to hibernate. It 

 is estimated that maximum egg production occurs when a terrapin is approximately 25 

 years of age. 



Terrapins in captivity have been observed to lay as often as five times in a single 

 season. Average annual egg productions as high as 23.6 and 24.5 per female have 

 been recorded for the original Carolina stock and the Texas brood stock, respectively. 

 The maximum average annual egg production of any female under observation has 

 been 35 eggs; the maximum hatch per female, 31.2 young. This record was obtained 

 in 1920 from the 1909 offspring of the "wild" stock. 



Rats, because of their burrowing into lately made nests and destroying large num- 

 bers of eggs, are serious enemies of the terrapin. 



The proper numerical relation of males to females for maximum fertility is not 

 known exactly, and it is difficult to ascertain it accurately in view of the habit of pro- 

 miscuous mating among terrapins. One mating, moreover, may give rise to fertile 

 eggs for four years thereafter; that is to say, the life of the spermatozoon in the female 

 after copulation may be at least four years. A 90 per cent hatch, which appears to be 

 normal, can, however, be obtained among well-matured terrapins when the number of 

 males is one-third the number of females. This average percentage of hatch is not 

 increased by the presence of a larger proportion of males. It appears from the study 

 of certain of the domestic broods that while egg laying is small a maximum fertility may 



