30 
BULLETIN OF THE BUREAU OF FISHERIES 
that among terrapins, as among chickens, certain females are “boarders.” If fur- 
ther observations confirm the results already obtained, it should be possible to elim- 
inate the boarders and to select animals of high fertility for breeding purposes. 
It appears to be of interest to call attention to the long period of time during 
which the original brood stock has produced eggs. Some of these animals were 
confined in 1909 and others in 1912. The early records of egg production by the old 
breeders are rather obscure, but there is on hand a fairly definite record dating 
from 1915 to 1926. Table 1 is based upon this record. It is evident from the table 
that the general trend in egg production over this period of years has been downward. 
Yet it has fluctuated from year to year, and the rather sharp recovery in 1926 is 
noteworthy. The age of these animals, as stated elsewhere, is not known, and the 
length of life of diamond-back terrapins, too, in unknown. Therefore, it is entirely 
impossible to state that the general decline in egg production is due to old age. 
Furthermore, the table shows an upward trend since 1921. An upward trend during 
recent years would scarcely be expected if the general decline were due to old age. 
For the same reason it does not seem logical to assume that the long confinement 
affected egg production. Neither can the decline readily be ascribed to food and 
care, for these have been uniform throughout the period. It seems very difficult, 
therefore, to find the cause or causes for the decline in egg production from 1915 to 
1921, the partial recovery during recent years, and the annual fluctuations that have 
taken place. The number of eggs destro 3 r ed by rats has varied from time to time, 
but it is not believed that the loss was great enough to affect the results greatly. 
Table 1 . — Average number of eggs produced by the wild brood stock, based on a, lot confined in a single 
pen from 1915 to 1927 
Year 
Eggs 
Year 
Eggs 
Year 
Eggs 
1915 
23.9 
1920 
13.4 
1925 
9.8 
1916 
21.6 
1921 
7.6 
1926 
14.8 
1917 
20.8 
1922.. 
8.2 
1927 
10. 1 
1918 
18. 6 
1923 
9.2 
1919 
19.6 
1924 
11.6 
Average. 
14.5 
The yearly egg production by the wild brood stock from 1915 to 1927, inclusive, 
has averaged 14.4 eggs per female. The average per year for all females 534 inches s 
and over in length, exclusive of two lots of wild animals recently confined, is 13 eggs 
per female. This, then, appears to be about the number of eggs per female that may 
be expected of acclimated animals. It is shown in another section of this report 
that a rate of fertility of the eggs of about 90 per cent usually prevails when sufficient 
males are present. These data, then, indicate that in general terrapin-cultural 
work about 12 young per female per annum may be expected. 
s The records show that no lot of terrapins grown in captivity has ever produced eggs until at least some of the females had 
reached a length (on the median line of the plastron) of 5J4 inches or more. Therefore, animals less than 5J4 inches long are consid- 
ered immature and are not considered in computing this average. 
