amounts up to 1 pound per acre. Birds have tolerated up to 2 pounds of DDT 

 per acre and most mammals, up to 5 pounds, with little or no apparent, immedi- 

 ate effect (Table 6). Of the lower forms of life, arthropods are most sensi- 

 tive. Many aquatic arthropods are killed after applications of 0.1 pound of 

 DDT per acre. The microfauna (mainly protozoa) are reported to be relatively 

 resistant as are the adults, at least, of the Mollusca and Annelida. Most of 

 the newer insecticides that are commonly applied to wildlife habitat are more 

 toxic to vertebrate animals than is DDT (Tables 7, 8, 9 and 10). On the other 

 hand, some herbicides and most fungicides are less toxic than is DDT. 



Specific examples of damage have recently been summarized in various ways 

 by Service personnel: for large area treatment [ll], for forest areas [24], 

 for aquatic areas [25], for specific programs such as Dutch elm disease [l6J, 

 and for the fire ant program [33]. General surveys also have been prepared 

 [l5], [22], [26], [58], [60]. The more recent and significant findings are 

 summarized here. Laboratory studies are presented first; then studies of 

 direct effects of pesticides on field populations are summarized; and finally 

 indirect effects of pesticides are discussed. 



III. LABORATORY STUDIES AND TOXICOLOGY 



The Patuxent Wildlife Research Center has conducted tests on captive bob- 

 white quail and ring-necked pheasants for many years. Laboratory populations 

 of mallard ducks have been established and maintained during the past 2 years 

 and tests on them are under way. Approximately 5000 young and adult of these 

 and other game birds are available as subjects and controls. Experiments are 

 commonly conducted with 25 young subjects in a group and replicated 2 or 3 

 times. More limited tests on adult game birds, and on blackbirds, starlings, 

 and small mammals also are being conducted at Patuxent and at educational insti- 

 tutions under contract with this Bureau. 



These tests are designed to determine quantities of common pesticides 

 which will produce acute or chronic poisoning, and to furnish information upon 

 the effects of repeated or prolonged exposure to sublethal dosages. Appraisals 

 are complicated by the fact that effects of a chemical vary with the species 

 of animal, dosage rate, duration of exposure, time of year, sex, age, vigor, 

 and nutritional status of the individual. For example, male pheasants are 

 more susceptible than females to chlorinated insecticides; particularly during 

 the breeding season; and young birds are less resistant than adults. The data 

 in Table 7 show quantities of insecticides which will produce at least bO% 

 mortality of birds at all stages of the life cycle. 



Feeding of low levels of insecticides prior to or during the breeding 

 season produced adverse effects upon reproductive capacity of quail (Tables 

 8 and 9). Production, fertility or hatchability of eggs were reduced, and un- 

 usually high percentages of chicks were crippled or defective. Viability of 

 the apparently normal chicks was reduced, and mortality of the young birds 

 during the first 6 weeks of life was above normal. 



