Health Of Wildlife Populations Research Articles

Exposures to Estradiol, Ethinylestradiol and Octylphenol Affect Survival and Growth of Rana pipiens and Rana sylvatica Tadpoles

Endocrine disrupting compounds (EDCs) are often detected in the aquatic environment and can negatively affect the health of wildlife populations. However, little is known about the sensitivity of native amphibians to EDCs. Wood frogs (Rana sylvatica) and Northern leopard frogs (Rana pipiens) were exposed to three estrogenic EDCs: estradiol (E2), ethinylestradiol (EE2), and 4-tert-octylphenol (OP). In addition, R. pipiens were exposed during two developmental stages (Gosner stages 26 and 36) to examine life-stage differences in sensitivity. Tadpoles were exposed for 2 wk to 8 nominal concentrations (0.25 μM–10 μM) of each compound. Individual mortality was recorded during the exposure period, while body weight was measured at the end of 2 wk. LC50 values were calculated, and differences in body weight between vehicle control and exposed groups were assessed. Rank order toxicity of the compounds for both R. pipiens stages and both species was OP > EE2 > E2. Gosner stage 26 tadpoles were more sensitive (LC50: E2 [5.57 μM], EE2 [3.01 μM], OP [1.36 μM]) to all three compounds when compared to stage 36 tadpoles (LC50: E2 [>10 μM], EE2 [4.17 μM], OP [2.80 μM]). Interspecies comparisons revealed R. sylvatica tadpoles (LC50: E2 [2.50 μM], EE2 [1.89 μM], OP [0.74 μM]) as being more sensitive to the three compounds than R. pipiens (LC50: E2 [4.56 μM], EE2 [2.75 μM], OP [1.42 μM]). Xenoestrogen exposure also affected tadpole body weight which may have long-term adverse effects on the rate of metamorphosis. These results provide toxicological data needed for assessing sublethal effects of estrogenic compounds on amphibian development and suggest that environmental levels of OP may pose a serious risk to the health of amphibian populations.

The health of wild red and sika deer in Scotland: An analysis of key endoparasites and recommendations for monitoring disease

Monitoring the health of wildlife populations is important for understanding and controlling the risk of infections to livestock, humans and/or other wildlife. In this paper, we analyse the results of surveys of parasites and non-specific signs of diseases carried out on organs from 638 red and 107 sika deer culled in four regions of Scotland between 1991 and 1997. Infections of the lung by Elaphostrongylus spp. were significantly greater in red than sika deer. Older animals were more heavily infected with Elaphostrongylus spp. and Sarcocystis spp., and infections with Sarcocystis spp. tended to be heavier in more recent years. The results suggest that a combination of key indicator parasite species and non-specific signs of disease may be useful for monitoring the health of wildlife populations at a national scale. However, they also demonstrate that such monitoring needs to be long-term, carried out according to standard protocols and at an appropriate resolution to enable integration with data on other potentially influential environmental factors.

Conservation medicine.

The Field Veterinary Program (FVP) of the Wildlife Conservation Society (WCS) was created in 1989 to combat the wildlife disease and health problems that increasingly complicate the process of wildlife conservation. The FVP provides veterinary services for the more than 300 WCS conservation projects located in more than 50 countries around the world. Most of these projects are in tropical regions and many have a wildlife/domestic livestock component. Wildlife health care provided by the FVP staff includes (1) identifying critical health factors; (2) monitoring health status; (3) crisis intervention; (4) developing and applying new technologies; (5) animal handling and welfare concerns; and (6) training. Additionally, the staff of the FVP give expert advice to many governmental and non-governmental agencies that are involved in setting policies directly related to wildlife health and conservation issues. In this paper, two FVP projects are presented as examples of studies that have increased our understanding of the role wildlife diseases may play in the health of livestock and human populations, as well as the role humans and livestock may play in the health of wildlife populations. Examples of the collaborative work between the FVP staff and scientists from many disciplines (e.g., acarologists, mycobacterium experts, ecologists, and biologists) are also presented.

Preliminary assessment of the impacts of human activities on gorillas Gorilla gorilla gorilla and other wildlife at Dzanga-Sangha Reserve, Central African Republic

AbstractThe aim of this study was to make preliminary assessments of the effects of human activities on the gorillas and other wildlife in the Dzanga-Ndoki Park and broader Dzanga-Sangha Dense Forest Reserve (RDS), Central African Republic. During a month-long survey in 1997, observation and sign of humans and large mammals, including ape nest-sites, were recorded on 81.2 km of line transects in three sectors of the park and reserve. Human activities, including intensities of logging and hunting, appeared to decrease with distance from the population centres and were lower in the park than in the reserve sectors. Encounter rates with sign of duikers Cephalophus spp., monkeys Cercopithecus spp. and Cercocebus albigena, elephants Loxodonta africana, and gorillas Gorilla gorilla gorilla were generally lower in regions of high human activity in the reserve than in the park sectors. Nevertheless, gorilla nest-site densities did not vary significantly between sectors or with human activity levels. A high frequency of zero (bare ground) nests at RDS suggests that gorilla surveys that rely on line transect methods and use nest decomposition rates from other studies may sometimes underestimate gorilla densities. This study suggests that current levels of exploitation in managed hunting zones of national forest reserves may be negatively affecting targeted wildlife populations in these zones. Assessments should be a regular part of efforts to monitor the health of wildlife populations in managed protected zones. Participation by Central Africans in research will continue to benefit conservation and development efforts.

Aquatic pollution-induced immunotoxicity in wildlife species.

The potential for chemicals to adversely affect human immunologic health has traditionally been evaluated in rodents, under laboratory conditions. These laboratory studies have generated valuable hazard identification and immunotoxicologic mechanism data; however, genetically diverse populations exposed in the wild may better reflect both human exposure conditions and may provide insight into potential immunotoxic effects in humans. In addition, comparative studies of species occupying reference and impacted sites provide important information on the effects of environmental pollution on the immunologic health of wildlife populations. In this symposium overview, Peter Hodson describes physiological changes in fish collected above or below the outflows of paper mills discharging effluent from the bleaching process (BKME). Effects attributable to BKME were identified, as were physiological changes attributable to other environmental factors. In this context, he discussed the problems of identifying true cause and effect relationships in field studies. Mohamed Faisal described changes in immune function of fish collected from areas with high levels of polyaromatic hydrocarbon contamination. His studies identified a contaminant-related decreases in the ability of anterior kidney leukocytes to bind to and kill tumor cell line targets, as well as changes in lymphocyte proliferation in response to mitogens. Altered proliferative responses of fish from the contaminated site were partially reversed by maintaining fish in water from the reference site. Peter Ross described studies in which harbor seals were fed herring obtained from relatively clean (Atlantic Ocean) and contaminated (Baltic Sea) waters. Decreased natural killer cell activity and lymphoproliferative responses to T and B cell mitogens, as well as depressed antibody and delayed hypersensitivity responses to injected antigens, were identified in seals fed contaminated herring. In laboratory studies, it was determined that rats fed freeze-dried Baltic Sea herring had higher virus titers after challenge with rat cytomegalovirus (RCMV) than rats fed Atlantic Ocean herring; perinatal exposure of rats to oil extracted from Baltic herring also reduced the response to challenge with RCMV. Keith Grassman reported an association between exposure to polyhalogenated aryl hydrocarbons and decreased T cell immunity in the offspring of fish-eating birds (herring gulls and Capsian terns) at highly contaminated sites in the Great Lakes. The greatest suppression of skin test responses to phytohemagglutinin injection (an indicator of T cell immunity) was consistently found at sites with the highest contaminant concentrations. Judith Zelikoff addressed the applicability of immunotoxicity studies developed in laboratory-reared fish for detecting altered immune function in wild populations. She presented data from studies done in her laboratory with environmentally relevant concentrations of metals as examples. Although the necessity of proceeding with caution when extrapolating across species was emphasized, she concluded that published data, and results presented by the other Symposium participants, demonstrate that assays similar to those developed for use in laboratory rodents may be useful for detecting immune system defects in wildlife species directly exposed to toxicants present in the environment.

Polychlorinated dibenzodioxins, dibenzofurans and non-ortho substituted polychlorinated biphenyls in caribou (Rangifer tarandus) from the Canadian Arctic

The presence of contaminants in the Arctic environment has raised concerns regarding levels in wildlife and possible effects on the health of wildlife populations. In addition, contaminants in wild foods are of particular concern to those people who rely on these foodstuffs for a significant portion of their diet. Among the most toxic contaminants found in the environment are the polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and non-ortho substituted polychlorinated biphenyls (NOPCBs). Few data exist documenting the levels of these compounds in Arctic terrestrial wildlife. In 1993, caribou samples were obtained from three herds in the Yukon Territory (Finlayson, Tay and Bonnet Plume) and from four herds in the Northwest Territories (Bathurst, Southampton Island, Cape Dorset and Lake Harbour). High resolution gas-chromatography/mass spectrometry was used to measure contaminant concentrations. Wet weight concentrations of PCDDs, PCDFs and NOPCBs were greater in fat tissue than in muscle and liver, however, concentrations in all tissues were extremely low. Lipid normalized concentrations were greater in muscle and liver than in fat, indicating that equilibrium partitioning is not the only process regulating tissue concentrations of these contaminants. There were no significant relationships between concentrations of individual congeners and caribou age. Concentrations of the non-ortho substituted PCBs #126 and #169 were greater in caribou from the eastern Arctic, although levels in all herds were low. 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) toxic equivalents were also low in tissues from all herds. The presence of these compounds in the Arctic can likely be attributed to long-range atmospheric transport. The levels documented in this study are some of the lowest ever reported in wildlife and are unlikely to pose a threat to caribou or their human consumers.