17 



shown to be affected through the fish the birds consumed. Samples of tissue 

 from fish and grebes contained very high concentrations of DDD, up to 1600 parts 

 per million in grebes and 2500 parts per million in fish. For this reason con- 

 trol operations were suspended in 1958, despite the fact that larval counts of 

 gnats in 1958 were the highest on record [SOj. 



Wildlife also could be seriously affected by reduction in the amount of 

 insect or crustacean foods, aside from direct or indirect poisoning. For 

 example, many studies have shown that fiddler crabs are greatly decreased in 

 numbers after pesticidal application [27], [59], and this reduction could 

 affect the clapper rails for whom they are a principal food [47]. 



C. Grasshopper Control 



Bureau studies of the side effects of an application of 1 pound of sevin 

 per acre for grasshopper control in Montana during July of 1959 indicated 

 vertebrates were not affected directly. No vertebrate casualty attributable to 

 sevin was found. Counts of birds on the treated area, however, dropped from 

 173 before spraying to 30 two weeks after spraying. Counts on the control area 

 for the same periods averaged 85 and 56 birds, respectively. The post-breeding 

 population of birds apparently departed from the test area after destruction of 

 their insect food supply by spraying (Finley, unpubl.). 



Indirect effects on vertebrates through changes in the numbers of food- 

 chain organisms are inherent in the use of any broad-spectrum insecticide. 

 These faunal displacements sometimes lead to outbreaks of other pest species, 

 e.g., an outbreak of red spider mites may follow spraying to control spruce 

 budworm (Finley, unpubl.). The full import of population imbalances is unknown, 

 but such phenomena as the development of invertebrate populations resistant to 

 presently used insecticides or secondary outbreaks of pests, sometimes neces- 

 sitates additional control measures. 



VI. RECENT PESTICIDE LEGISLATION 



Federal and State laws have been and are being enacted to regulate the use 

 of pesticides. Federal laws include the Insecticide, Fungicide, and Rodenticide 

 Act of 1947, amended in 1959 (Nematocide, Plant Regulator, Defoliant, and 

 Desiccant Amendment). This Act is administered by the U. S. Department of Agri- 

 culture, and clearly states that wildlife values must be considered in the 

 registration and use of pesticides. The Food, Drug, and Cosmetic Act was 

 amended in 1954 (Pesticide Chemicals Amendment), and again in 1958 (Food Addi- 

 tives Amendment). This Act is administered by the Food and Drug Administration 

 of the U. S. Department of Health, Education, and Welfare which sets tolerances 

 on pesticide residues in food. Although the Act does not directly concern 

 wildlife, it has had great effect on the procedures, dosage rates, and chemicals 

 used in wildlife environments. Public Laws 85-582 (1958) and 86-279 (1959) 

 specifically direct the Service to study the effects of pesticides on wildlife. 



