DIAMOND-BACK TERRAPIN CULTURE 
37 
cerning diseases are to be found in subsequent paragraphs. A definite record of the 
deaths that have occurred can not be given because several animals in nearly every 
lot are missing. Some of these animals may have died unnoticed (especially when 
they were small), others undoubtedly were carried away by rats, birds, or other 
enemies, or, again, they may have found an avenue for escape. It is definitely known 
that in a few instances a number of animals got away during storms, when the water 
nearly reached the top of the walls of the pens. On the other hand, not infrequently 
the missing animals simply were overlooked when a census was taken. It is very 
difficult, because of their very proficient hiding propensities, to find all the terrapins 
in an inclosure even though the pen be small. Therefore, the “missing” animals of 
one census sometimes reappeared in the next one. On account of the impracticability 
of getting and keeping definite records of deaths and escapes only the animals found 
when a census was taken were considered in many of the tables appearing in this 
report. From a practical standpoint, the animals that are missing, of course, are of 
no more significance (unless they can be found) than the dead ones, and the propor- 
tionate number of those hatched that may be grown to maturity is of chief importance. 
Many of the terrapins grown in captivity, as stated elsewhere, were selected, and 
the entire brood was kept only in 1910, 7 when only a small number was hatched. 
This brood originally consisted of 293 animals. It was divided into two lots. One 
lot, consisting of 120 individuals, was allowed to hibernate, and the other one, con- 
sisting of 173 animals, was kept warm and fed the first winter and part of the second 
winter. At the age of 1 year 93 per cent of the winter-fed terrapins and 85.8 per 
cent of the hibernating ones were alive. At 6 years of age, when at least some of the 
animals had become sexually mature and reproduction had begun, 83.2 per cent of 
the winter-fed lot and 78.3 per cent of the hibernating one still survived, and at 15 
years of age 74 per cent of the former and 76.6 per cent of the latter lot were found. 
In two unselected lots of the brood of 1911, each originally consisting of 100 terra- 
pins, the percentage of survival at 1 year of age was 95 for the winter-fed lot and 89 
for the hibernating one. At 6 years of age 82 per cent of the winter-fed animals were 
found and 78 per cent of the hibernating ones, and at 15 years 77 per cent of the 
former and 76 per cent of the latter were on hand. 
The four lots discussed in the preceding paragraphs are the only ones of those 
at hand that have reached maturity that were carried through as separate lots and 
without selection from the time of hatching to maturity. All the other lots of mature 
terrapins were selected at about 1 or 2 years of age from lots that had been fed the 
first winter, and therefore the records are not continuous and not directly comparable 
with those of the 1910 and 1911 broods. 
Winter feeding in an especially constructed brooder house 8 was begun with the 
1913 brood. The object of winter feeding, of course, was mainly to increase the 
growth of the young animals. The results of this project, with respect to the rate of 
growth, are discussed in another section of this paper. Its results with respect to 
mortality or survival, however, appear to belong to the present section of this report. 
7 In 1909 only a few terrapins were hatched, of which only 12 grew to maturity. This number is regarded as too small to be of 
much significance and is omitted in this discussion. 
8 A description and photograph of the terrapin brooder house used in these experiments may be found in Bureau of Fisheries 
Economic Circular No. 60, 1920, pp. 17 and 18, fig. 8. 
