DIAMOND-BACK TERRAPIN CULTURE 
39 
series of experiments tanks 8 feet long and 20 inches wide, divided into four equal com- 
partments, have been used. Each compartment, therefore, had a floor space of about 
20 by 24 inches. In some of the compartments 25 to 50 animals were held, 100 in 
others, and in still others 125 to 150 were placed. The experiment was carried through 
three seasons (October to May, 1923 to 1926) using each year an equal number of 
compartments for the different degrees of crowding. The rate of survival is very 
slightly in favor of the least crowding, for of 325 animals used, 80 per cent survived. 
Of 1,100 terrapins held 100 to a compartment, 79.5 per cent survived, whereas under 
the crowded condition of 125 to 150 animals to a compartment only 70.7 per cent of a 
total of 1,530 terrapins survived. The results with respect to the rate of growth for 
the different degrees of crowding are discussed elsewhere. It is sufficient to state here 
that they bear a relationship to each other somewhat similar to the rate of survival. 
It may be concluded, therefore, that it is practicable to confine as many as 100 young 
terrapins in a space having an area of 20 by 24 inches. 
The death rate among the young animals that are allowed to hibernate frequently 
is almost negligible during their first winter, as in the brood of 1926, of which 99.9 
per cent of 1,627 animals survived (Table 17). However, in a few instances the death 
rate has run very high, as, for example, in the brood of 1922, in which only 44.7 per 
cent of 789 animals survived the winter. 
Records of survival of the hibernating animals, as well as the winter-fed ones, 
as far as data are available, are given in Table 17. The percentage of survival of the 
winter-fed and hibernating terrapins, given in the table are not directly comparable, 
as the hibernating ones usually emerged from hibernation and were counted during 
the latter part of March or early in April, whereas the winter-fed animals each year 
were counted from four to six weeks later; that is, at the time they were removed from 
the nursery house. During the first four to six weeks after emerging from hiberna- 
tion the death rate usually is quite heavy and generally much greater than in non- 
hibernating animals. Therefore, Table 17 does not contain directly comparable 
data, with respect to survival, of the advantages of one method over another. It does 
show, however, the yearly fluctuations in the rate of survival during the early months 
of life that has taken place during the course of the experiments, both for hibernating 
and winter-fed animals. 
The fluctuations in the death rate in the winter-fed animals can be accounted 
for, in part, by the prevalence of a cancerous disease (elsewhere referred to as “sores”) 
that as yet (1928) is of unknown origin and for which no preventive or cure has been 
found. This disease, which outwardly makes its appearance as sores chiefly on the 
tail or as discolored areas on the plastron, has always existed among winter-fed 
animals throughout the course of the experiments. However, it reached serious 
epidemic proportions only in the 1914 and 1927 broods, when the rate of survival, as 
shown in Table 17, was greatly reduced. Deaths have occurred from other causes, 
of course; principally of “soft shell” and a few of “limber neck” and miscellaneous 
causes. The deaths from these sources, too, have varied and are the cause of a part 
of the great fluctuations. 
The disease designated as “soft shell” is associated with a failure to eat, resulting, 
of course, in a failure to grow and in general emaciation. The majority of cases of soft 
shell occur among young that never have been induced to take food, although rather 
35006—29 3 
