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Results for “Transactions of the North American Wildlife and Natural Resources Conference”

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USGS1969

The killing efficiency of soft iron shot

A cooperative research effort between the ammunition industry and the Bureau of Sport Fisheries and Wildlife is aimed at finding a suitable non-toxic substitute for lead shot. A contract study by an independent research organization evaluated ways of coating or detoxifying lead shot or replacing it with another metal. As a result of that study, the only promising candidate is soft iron. Previous tests of hard iron shot had suggested that its killing effectiveness was poor at longer ranges due to the lower density. In addition, its hardness caused excessive damage to shotgun barrels. A unique, automated shooting facility was constructed at the Patuxent Wildlife Research Center to test the killing effectiveness of soft iron shot under controlled conditions. Tethered game-farm mallards were transported across a shooting point in a manner simulating free flight. A microswitch triggered a mounted shotgun so that each shot was 'perfect.' A soft iron shot, in Number 4 size, was produced by the ammunition industry and loaded in 12-gauge shells to give optimum ballistic performance. Commercial loads of lead shot in both Number 4 and Number 6 size were used for comparison. A total of 2,010 ducks were shot at ranges of 30 to 65 yards and at broadside and head-on angles in a statistically designed procedure. The following data were recorded for each duck: time until death, broken wing or leg bones, and number of embedded shot. Those ducks not killed outright were held for 10 days. From these data, ducks were categorized as 'probably bagged,' 'probably lost cripples,' or survivors. The test revealed that the killing effectiveness of this soft iron shot was superior to its anticipated performance and close to that obtained with commercial lead loads containing an equal number of pellets. Bagging a duck, in terms of rapid death or broken wing, was primarily dependent on the probability of a shot striking that vital area, and therefore a function of range. There was no indication that iron shot would result in greater crippling loss. Despite the apparent effectiveness of this iron shot, transition to its use in waterfowl hunting is not now possible. The sample used for this test was produced by a laboratory procedure that is unsuitable for manufacture. There is no process for producing soft iron shot in the quantities needed. Industry is doing its best to resolve this problem.

Transactions of the North American Wildlife and Na↗
USGS1971

The occurrence and significance of polychlorinated biphenyls in the environment

SUMMARY: Polychlorinated biphenyls constitute a group of chlorine-bearing compounds of industrial origin that have permeated the natural environment throughout the world. Their chemical structure resembles that of some of the organochlorine pesticides. They are troublesome interferences in gas chromatographic analysis of these pesticides. Although methods have been developed to overcome analytical problems, measurements of quantity still are only approximate. Special studies in the United States, Netherlands, and Great Britain have traced PCB's to industrial effluent, but other possible sources have not been followed. Their use in paints, cartons, and insulating fluids suggests that environmental pollution may be from many different sources. PCB's are present in fish and wildlife in many countries of the world. Quantities are higher in animals living near industrial areas. PCB's build up in biological food chains with increases of tens to thousands of times from lower to higher organisms. Experimental studies have shown that PCB's have a toxicity to mallards, pheasants, bobwhite quail, coturnix quail, red-winged blackbirds, starlings, cowbirds, and grackles that is of the same order as the toxicity of DDE to these species. Overt signs of poisoning also are similar to those caused by compounds of the DDT group. Toxic effects of DDE and Aroclor 1254 to coturnix chicks were additive, but not synergistic. PCB's containing higher percentages of chlorine are more toxic to birds than those containing lower percentages. PCB's of foreign manufacture contained contaminants to an extent that greatly increased their toxicity Aroclor 1242. Statistical evaluations of the role that different chemicals may play in thinning of eggshells of brown pelicans show that DDE residues correlate better with shell thinning than do residues of dieldrin or PCB's. Studies of the effects of PCB's in the environment are as yet insufficient for well-rounded conclusions. The evidence available indicates that they must be viewed as potential problems until fuller data can be assembled. Toxicity to insects of PCB's of different degrees of chlorination is the reverse of the pattern in birds: the lower chlorinations are more toxic to insects. PCB's enhanced the toxicity of dieldrin and DDT to insects. Shrimp are very sensitive to PCB's and most will die as a result of 20-day exposure to a concentration of 5 ppb. PCB's also inhibit shell growth of oysters. Fish and crabs are less sensitive; all accumulate residues to many times the concentrations in the water, and a test with crabs showed that they lost the residues very slowly. Residues of PCB's in the brains of birds killed by these compounds measure in the hundreds of parts per million. PCB's may have contributed to mortality of some birds in the field. PCB's induce microsomal enzyme activity in birds and mammals and the lower chlorinated mixtures have estrogenic activity in rats. Exposure to PCB's increased the susceptibility of mallard ducklings to duck hepatitis virus. Offspring of pheasants whose parents received high dosages of PCB's made poor choices in visual cliff tests. Egg production and hatching after pipping also were affected. Long-term studies of the reproductive effects of Aroclor 1254 on mallards and bobwhite quail and of Aroclor 1254 plus DDE on quail showed no significant differences from controls. In studies of chickens, however, egg production, hatchability, and shell thickness were impaired by high doses of Aroclor 1254 and by low doses of Aroclor 1242. Statistical evaluations of the role that different chemicals may play in thinning of eggshells of brown pelicans show that DDE residues correlate better with shell thinning than do residues of dieldrin or PCB's. Studies of the effects of PCB's in the environment are as yet insufficient for well-rounded conclusions. The evidence available indicates that they must be

Transactions of the North American Wildlife and Na↗
USGS1960

Pesticidal residues in animal tissues

Tests with penned starlings, rats, pheasants, and ducks indicated that each species differs in sensitivity to the various pesticides. Residues in tissues are proportional to the degree of exposure during area treatment and they are also found in animals shot six or more months after treatment. The presence of more than 20-30 ppm of DDT, 20 ppm of chlordan, and 6-20 ppm of heptachlor epoxide in quail tissues indicated that the birds had ingested lethal dosages of the pesticides.

Transactions of the North American Wildlife and Na↗