66 
BULLETIN OF THE BUREAU OF FISHERIES 
In 1919, 100 animals of the 1917 brood were placed in a small pen measuring 
about 5 feet wide by 36 feet deep and 100 in a much larger pen, similarly situated, 
having a width of about 24 feet and a depth of about 36 feet. Owing to depreda- 
tions by rats the numbers were greatly reduced. In 1927 only 50 animals were left 
in the small pen, and these (including 10 males) had an average length of about 
inches (134.8 millimeters), whereas only 39 were found (more animals probably were 
present, but they were difficult to find due to the large size of the pen) in the larger 
pen, which (including 7 males) had an average length of slightly over 5 inches (126.4 
millimeters). If this experiment could be used as a criterion, “close range” would 
seem to be better than a wider one. The animals are sluggish, and it is not believed 
that a large pen is necessary for the purpose of providing space for exercise. The 
main consideration is the provision of sufficient room to furnish the necessary 
sanitation. 
It seems reasonable to conclude from the experiments described and from the 
results obtained with several other lots that under the conditions existing at Beaufort 
certainly as many as 100 animals may be held and grown to maturity in pens having 
an area of 5 by 32 feet. Space requirements, as already suggested, undoubtedly 
would vary in different localities according to the cleanness of the water brought by 
flood tides and other local conditions. 
SEX RATIO 
The sexes of terrapins can not be distinguished from external characters until a 
length of 3 to 4 inches is attained. When this size is reached the males may be 
recognized by the much larger and heavier tail. There are other differences, such 
as the smaller head and the more wedge-shaped posterior outline of the carapace in 
the male, but the most evident character is the tail. Because it is impossible to 
distinguish the sexes in young animals from external characters, and because dissec- 
tions of such animals have not been attempted, information concerning sex ratio is 
still quite incomplete. It may be stated, however, that the males are greatly in the 
minority among the total number of terrapins grown to maturity in captivity. This 
becomes evident from the fact that in 1927 among a total of 1,300 such animals in 
which the sexes could be distinguished positively there were only 242 males, thus 
giving a ratio of 1 male to 4.4 females. Omitting certain hybrid lots, in which the 
males are numerous, and using only pure stock of Carolina terrapins, the ratio 
becomes 1 male to 6.4 females. 
Most of the lots from which the foregoing data were derived consist of animals 
selected (usually at about 1 year of age) from a year’s brood (which usually con- 
sisted of a few hundred to a thousand or more individuals) because of the rapid growth 
they had made, while the rest were liberated. One lot was selected for the opposite 
reason, however; that is, the “runts” were retained; and still other lots were unse- 
lected. It is not evident from the results that the selections affected the sex ratio 
constantly in any one direction. The large variation in sex ratio among the small 
lots on hand suggests, however, that the element of chance selection as well as chance 
survival may have been important. 
The extremes in sex ratio are represented in two lots of the brood of 1911 of 
Carolina terrapins, and in a lot of hybrid terrapins (Carolina males crossed with 
