68 BULLETIN OF THE BUREAU OF FISHERIES 
Table 36. — Sex ratio in several lots of diamond-back terrapins hatched and grown to maturity in 
confinement 1 
Year of hatching 
Number 
origi- 
nally 
in lot 
Number on hand, 
1927 2 
Ratio of 
males to 
females 
Remarks 
Males 
Females 
1910 
171 
13 
116 
1:8.9 
All fed first winter, some the second winter; unselected. 
1910 
119 
5 
87 
1:17.4 
Hibernated each winter; unselected. 
1911 
100 
0 
78 
Fed first three winters; unselected. 
1911 
100 
0 
73 
Hibernated each winter; unselected. 
1912 
100 
10 
54 
1:5.4 
Some fed first winter, all fed the second winter. Selected at the age of 
1 year, the smallest of the entire brood, consisting of 1,221 animals. 
Majority fed first winter, all fed the second winter. Selected at the 
age of 1 year, the largest from the entire brood, consisting of 1,221 
animals. 
1912 
100 
17 
64 
1:3.8 
1913 
100 
4 
75 
1:18.8 
Fed first winter; selected at 1 year of age, the largest from lot consisting 
of 504 animals. 
1914 
100 
2 
83 
1:41.5 
Fed first winter; selected at age of 1 year, the largest from a lot consisting 
of 587 animals. 
1916 
200 
40 
158 
1:4.0 
Fed first winter; selected at age of 1 year, the largest from a lot consisting 
of 1,710 animals. 
1917 
200 
17 
73 
1:4.3 
Fed first winter; selected at 9 months of age, the largest from a brood 
consisting of 961 animals. 
1919 
100 
22 
52 
1:2.4 
Fed first winter; selected at 8 months of age, the largest from a lot com- 
posed of 169 animals. 
1919 
80 
33 
18 
1:0. 5 
Hybrids (Texas males and Carolina females). Fed first winter; un- 
selected. Number reduced through depredations by rats when the 
terrapins were small. 
1919 
100 
13 
18 
1:1.4 
Hybrids (Carolina males and Texas females) . Fed first winter; selected 
at 8 months of age, the largest from a lot consisting of 192 terrapins. 
Original number much reduced through depredations by rats when 
the terrapins were small. 
1920 
200 
23 
89 
1:3.9 
Fed first winter; selected at 8 months of age, the largest from several 
hundred animals. 
1920 
87 
40 
20 
1:0.5 
Hybrids (Carolina males and Texas females). Fed first winter; un- 
selected. 
Total 
1,857 
239 
1,058 
Ratio for all lots combined, 1 male to 4.4 females. 
1 The animals are Carolina terrapins unless otherwise stated under remarks. 
2 The difference between the number originally in a lot and the number on hand in 1927 does not indicate the natural death 
rate that has occurred in each group. In a few instances several animals were taken away and used for other purposes; in a few cases 
some terrapins were lost in a storm; and in several lots rats killed some of the animals while small. Furthermore, the census varies 
from year to year; for it is extremely difficult to capture all of the animals at one time, because of their highly developed hiding 
propensities; and therefore the census for any one lot may vary from one to several from one year to the next, even though no deaths 
have occurred and no animals have been removed. 
SUMMARY 
The present series of experiments in diamond-back terrapin culture was started 
in 1909. Two subspecies (Chesapeake and Carolina) of terrapins are used in the 
experiments. Texas terrapins, too, were used at one time but have been discarded, 
except as represented in certain hybrid lots. Some of the experiments that have 
been undertaken have not been carried on long enough to yield results, and upon 
those no report is given. The discussion is confined to the experiments from which 
noteworthy results have been secured. 
Egg production has fluctuated greatly from year to year within lots and within 
broods. The number of eggs produced by individual females of the same age is 
known to vary from 5 to 29 during a single season. Within a single lot, egg production 
has varied from 7.6 to 23.9 eggs per female. It is concluded that in general terrapin 
culture an average annual production of 12 eggs per female may be expected. 
The degree of fertility of the eggs, too, has fluctuated greatly, for which often 
no good reasons can be given. In general, the highest percentage of fertility has 
resulted in the lots having the largest proportionate number of males, although 
exceptions to this rule are noted. Data are presented that would indicate that with 
