Geology topics

R. K. LaVal

Publications and source records attributed to R. K. LaVal.

5 recordsLinked to original sources

USGS1983

Year and age effects on residues of dieldrin and heptachlor in dead gray bats, Franklin County, Missouri— 1976, 1977, and 1978

Dead gray bats ( Myotis grisescens ) containing lethal concentrations of dieldrin were found beneath a maternity roost in Bat Cave Nos. 2 and 3, Franklin County, Missouri, in 1976, 1977 and 1978. Whereas residues of dieldrin, DDE [1,1-dichloro-2,2-bis( p -chlorophenyl)ethylene] and PCB polychlorinated biphenyls in bats appeared not to change significantly over the 3 years, residues of heptachlor-related chemicals increased in 1977 to potentially dangerous concentrations and remained elevated in 1978. Lethal brain levels of dieldrin in adult bats (geometric mean = 12.1 μg/g), compared with juvenile bats (geometric mean = 6.5 μg/g), indicated that juveniles are nearly twice as sensitive. The estimated population of gray bats (as maximum number of nonflying young) at Bat Cave Nos. 2 and 3 in 1976 and 1978 was 1,800 bats, but in 1979 no bats were present. Dieldrin, perhaps in conjunction with heptachlor, may have caused the decline and disappearance of this colony. However, dieldrin was banned in 1974 and Missouri's authorization to use heptachlor on corn expired in 1981. Furthermore, three organophosphate insecticides (chlorpyrifos, dyfonate and mocap) are to be substituted. We hope that the gray bats remaining in this area of Missouri survive the residues of dieldrin and heptachlor still in their food chains and prove to be unaffected by the new organophosphates.

Environmental Toxicology and Chemistry↗

USGS1982

Estimating pesticide burdens of bats from guano analyses

Bat guano was first collected and analyzed for environmental pollutants in the early 1970's (REIDINGER 1972:53-64; PETIT & ALTENBACH 1973). Later analyses of both guano and bats from two roosts indicated a correspondence between levels of organochlorine residues in guano and in bat carcasses from the same colony (CLARK & PROUTY 1976). Gray myotis ( mytosis grisescens ) were found dead with lethal brain levels of dieldrin in two colonies where dieldrin levels in guano were high relative to other colonies (CLARK et al. 1978, 1980). We collected and analyzed both guano samples and bats found dead or killed accidentally during handling from numerous roosts of several bat species. The objective of this study was to determine whether a correlation existed between organochlorine residues in guano and in bat carcasses.

Bulletin of Environmental Contamination and Toxico↗

USGS1981

Gray bats and pollution in Missouri and northern Alabama

Gray bats died with lethal brain concentrations of dieldrin and rising levels of heptachlor epoxide in 1976, 1977, and 1978 at Bat Caves No. 2-3, Franklin County, Missouri. The colony disappeared in 1979. Dieldrin was banned in 1974 and 1981 was the last year for heptachlor use in Missouri. The State is recommendiing three organophosphates (chlorpyrifos or Dursban, dyfonate or Fonophos, and ethoprop or Mocap) as substitutes for heptachlor. All three compounds have excellent records in the environment. Analyses of insects collected where bats of this colony fed showed beetles, particularly rove beetles (Staphylinidae), to be the most heavily contaminated part of the bat's diet. Lactation concentrated these residues so that levels in milk were approximately 30 times those in the insect diet. Gray bats found dead in caves in northern Alabama showed DDD (a DDT derivative) contamination. Bats from the colony at Cave Springs Cave on the Wheeler National Wildlife Refuge contained up to 29 ppm DDD in their brains, but this is probably less than one-half the lethal level. Bats from other colonies contained less. The DDD contamination enters the Terinessee River just above the Wheeler Refuge and is seen in gray bat colonies as far as 60 miles downriver.

Bat Research News↗

USGS1980

Dieldrin and heptachlor residues in dead gray bats, Franklin County, Missouri--1976 versus 1977

Lethal dieldrin concentrations were found in the brains of dead gray bats ( Myotis grisescens ) collected during 1976 and 1977 beneath a maternity roost in a Missouri cave. In addition, residues of heptachlor epoxide, oxychlordane, cis-chlordane, and trans-nonachlor increased significantly in both brains and carcasses of bats collected during 1977. These increases appear to reflect a switch by local farmers from aldrin, dieldrin's parent compound, to heptachlor for the control of cutworms. They also constitute an additional threat to this colony of this endangered bat species.

Pesticides Monitoring Journal↗

USGS1978

Dieldrin-induced mortality in an endangered species, the gray bat ( Myotis grisescens )

Brains of juvenile gray bats, Myotis grisescens , found dead beneath maternity roosts in two Missouri caves contained lethal concentrations of dieldrin. One colony appeared to be abnormally small, and more dead bats were found a year after the juvenile bats had been collected. This is the first report to link the field mortality of bats directly to insecticide residues acquired through the food chain.

Missouri↗