Donald R. Clark

Responses of the iguanid lizard Anolis carolinensis to four organophosphorus pesticides

Abstract Dose related mortality and cholinesterase effects of parathion, methyl parathion, azinphos-methyl and malathion on Anolis carolinensis were investigated. The comparative effects of the four compounds on fish, birds and mammals are well known, but the effects of organophosphates on reptiles have not been studied critically. Sensitivity and patterns of mortality from exposure to the pesticides resemble those of birds and mammals rather than those of other poikilothermic vertebrates. Possible symptoms of epinephrine accumulation were observed in exposed animals; this side effect is consistent with the known mechanisms of the pesticides. Our findings indicate that brain cholinesterase activity is related to dose, that 50% inhibition of cholinesterase is associated with death and that 40% inhibition indicates sublethal exposure. Anolis lizards are frequently exposed to pesticides in the field and they may be useful in monitoring the hazards posed to a variety of wildlife species.

Gray bats killed by dieldrin at two additional Missouri caves: Aquatic macroinvertebrates found dead

We learned previously (CLARK et al. in manuscript) that mortality due to dieldrin poisoning occurred during 1976-78 in two maternity colonies of the endangered gray bat (~otis grisescens) at Bat Cave No. 2-3 and Roaring Spring Cave, Franklin County, Missouri. Residues of heptachlor-related chemicals in bats increased markedly in 1977 to potentially dangerous concentrations and remained elevated in 1978. The colony that showed the greater mortality disappeared in 1979 and was not present when the roost caves were visited in 1982.

Selenium accumulation by raccoons exposed to irrigation drainwater at Kesterson National Wildlife Refuge, California, 1986

In February–March 1986, eight raccoons (Procyon lotor) were collected at Kesterson Reservoir (Merced Co., California), which had received selenium-contaminated irrigation drainwater, and four raccoons were collected at the nearby Volta Wildlife Area, which had not. Selenium concentrations in Kesterson raccoons averaged 19.9 ppm (μg/g dry wt) in liver, 28.3 ppm (dry wt) in hair, 21.6 ppm (dry wt) in feces, and 2.61 ppm (wet wt) in blood and exceeded Volta concentrations by 12, 30, 21, and 10 times, respectively. Selenium concentrations in livers of Kesterson raccoons were less than those in five of nine other mammal species sampled in 1984. Selenium concentrations in hair provided the strongest statistical separation between study areas. Hemoglobin levels in two Kesterson raccoons equalled levels reported in rats with selenium-induced anemia, but the raccoons showed no illness. Amyloidosis in one Kesterson raccoon may have been selenium-induced. Our data indicate that raccoon births peaked about 2 months later than was previously reported. Based on our sample of 12 raccoons, we found no evidence that contamination by irrigation drainwater had negative effects on raccoons inhabiting Kesterson.

Uptake of environmental contaminants by small mammals in pickleweed habitats at San Francisco Bay, California

Small mammals were live-trapped in pickleweed (Salicornia virginica) habitats near San Francisco Bay, California in order to measure the uptake of several contaminants and to evaluate the potential effects of these contaminants on the endangered salt marsh harvest mouse (Reithrodontomys raviventris). Tissues of house mice (Mus musculus), deer mice (Peromyscus maniculatus), and California voles (Microtus californicus) from nine sites were analyzed for chemical contaminants including mercury, selenium, cadmium, lead, and polychlorinated biphenyls (PCBs). Concentrations of contaminants differed significantly among sites and species. Mean concentrations at sites where uptake was greatest were less than maximum means for the same or similar species recorded elsewhere. Harvest mice (Reithrodontomys spp.) were captured only at sites where concentrations of mercury or PCBs were below specific levels in house mice. Additional studies aimed at the protection of the salt marsh harvest mouse are suggested. These include contaminant feeding studies in the laboratory as well as field monitoring of surrogate species and community structure in salt marsh harvest mouse habitats.

Estimating Pesticide Burdens of Bats from Guano Analyses

Bat guano was first collected and analyzed for environmental pollutants in the early 1970s (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) 0 Gray myotis (~otis g~sescens) 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.

Organochlorine residues in females and nursing young of the big brown bat (Eptesicus fuscus)

SummaryCarcasses and brains of 18 big brown bats from Gaithersburg, Maryland, were analyzed for residues of organochlorine insecticides and PCBs. Eleven bats were adult females, and six of these had seven nursing young associated with them.Young bats resembled their parents in microgram amounts of PCB and DDE present in carcasses. However, concentrations of chemicals (expressed as ppm) were significantly higher in young. Brains of three young contained detectable residues of PCB and DDE.Younger adult females contained higher levels of PCB and DDE than did older ones. However, among the oldest females, amounts appeared to begin rising again. This pattern resembles that in free-tailed bats from Bracken Cave, Texas, but differs from the continuous linear decline seen in a Laurel, Maryland population of big brown bats, in which initial levels among younger females were higher than those in the Gaithersburg population.DDE was transferred from female to young more readily than was PCB by nursing. Five of 51 neonate big brown bats from the Laurel population were thought to have been born dead because of residues of PCB that were transferred across the placenta. Present data show that even greater amounts of PCB may be transferred to young by lactation and nursing.

Northern Alabama colonies of the endangered grey bat Myotis grisescens: Organochlorine contamination and mortality

Abstract From 1976 to 1986, dead and dying grey bats Myotis grisescens and grey bat guano were collected from caves along the Tennessee River in northern Alabama to determine the possible role of organochlorine chemicals — in particular wastes from a former DDT manufacturing plant near Huntsville—in the mortalities. Concentrations of chemical residues in brains were less than known lethal levels; certain observations and analyses did indicate the possibility of past organochlorine-induced bat deaths. Levels of contaminants in bats declined slowly during the 10-year sampling period, but heavy residue burdens persist. The high ratio of DDD to DDE in residues from the former DDT plant made them identifiable as far as 140 km downriver. Grey bats concentrated chemical residues to higher levels and demonstrated the presence of these residues over much greater distances than did red-winged blackbirds Agelaius phoenicus . Grey bats may be the most sensitive indicator available for monitoring the contamination from this former DDT manufacturing site.

Uptake of dietary PCB by pregnant big brown bats (Eptesicus fuscus) and their fetuses.

In a previous study (CLARK and LAMONT 1976), 26 pregnant big brown bats were captured, caged, and fed uncontaminated mealworms until their litters were born. Immediately after parturition, female bats and litters were frozen. Five litters included at least one dead young, and these five litters contained significantly more of the PCB, Aroclor 1260, than did the 21 litters with only living young.SummaryIn a previous study (CLARK and LAMONT 1976), 26 pregnant big brown bats were captured, caged, and fed uncontaminated mealworms until their litters were born. Immediately after parturition, female bats and litters were frozen. Five litters included at least one dead young, and these five litters contained significantly more of the PCB, Aroclor 1260, than did the 21 litters with only living young.The present study attempted to verify that Aroclor 1260 could cause stillbirths. I fed 18 of 36 pregnant big brown bats mealworms containing 6.36 ppm of Aroclor 1260 prior to birth of their litters. Both carcasses and litters of dosed females contained approximately 10 times more PCB than their respective controls, but no additional stillbirths resulted. Three of 18 control litters included dead young, whereas the comparable ratio among litters from dosed females was one of 18. Additional comparisons involving means of litter weight, adult female weight, parturition date, days in captivity, tooth wear, and percentage fat also failed to show any effect of the PCB.The association found earlier between PCB and dead young (CLARK and LAMONT 1976) was not one of cause and effect. In both studies, bats that had not been dosed showed greater PCB residues among younger females. Among control bats in the present series, females that produced dead young were significantly younger (that is, showed significantly less tooth wear) than other females. In sum, whereas dead young seemed to have been caused by greater residues, these two factors were actually independent of each other but associated with a third factor--age of the female parent bat.

Organochlorines and heavy metals in 17-year cicadas pose no apparent dietary threat to birds

Organochlorine and heavy metal concentrations in 17-year cicadas from Prince Georges and Anne Arundel Counties, Maryland, were well below levels known to be harmful to birds. Cicadas contained concentrations of metals similar to or less than other local invertebrates except they contained more copper than did earthworms. Copper and lead concentrations in cicadas from one site may have been elevated by sewage plant effluent deposited during river floodings. Cicadas from the median of a major highway did not contain more lead than cicadas from non-traffic sites.

Female reproductive dynamics in a Maryland population of ringneck snakes (Diadophis punctatus)

Adult female ringneck snakes (Diadophis punctatus) collected from a Maryland population during five successive summers laid a total of 50 clutches in which all eggs hatched successfully under laboratory conditions. Mean hatchling mass was not significantly related to female mass or clutch size when each was evaluated in separate analyses, but was significantly related to these factors when they were evaluated in a joint analysis. Mean hatchling masses of 0.6-1 g appear most adaptive; when females are large enough to produce 1 g eggs, the tendency is to produce a larger number of relatively smaller eggs. The relationship of clutch mass to female mass was unaffected by clutch size. Reproductive effort, measured as relative clutch mass (RCM, clutch mass/female mass), increased with age, as indicated by snout-vent length (SVL); also, the relationship of clutch mass to female mass indicated that clutches equaled a larger percentage as female mass increased. Clutch size averaged 3.55 eggs and ranged from 2 to 6. Clutches were laid from 17 June through 21 July (35 d), median 2 July. Clutches hatched during the 20-d interval 8-27 August (median August 18). Larger clutches were laid earlier in the season on average than smaller clutches. Incubation periods for clutches averaged 47 (range 42-51) d. Clutches laid later in the season averaged shorter incubation periods than clutches laid earlier.