PCBs and their putative effects on polecat (Mustela putorius) populations in Central Europe

A review of the status of the Western polecat Mustela putorius: a neglected and declining species?

The Western polecat Mustela putorius has a widespread European distribution and is currently listed as Least Concern by the IUCN Red List of Threatened Species. Reports are increasing of polecat population declines in several countries, although a paucity of data means population trends are poorly understood. This paper reviews and summarises information on the polecat’s status and range-wide population trends. Information and opinion were gathered for 34 countries, from individuals and organisations studying polecats and from reviewing the literature and national Red Lists. Where trends were identified, the polecat population is known or suspected to be declining in 20 countries, reported to be stable in five countries, stable or increasing in one country, and increasing in two countries. For many countries, data are so limited in quantity or spatial scale, or at risk of bias, that trends could not be identified or confidence in trend assessments is low. The main drivers of polecat decline are poorly understood, but might include habitat degradation; changes in prey availability; competition with invasive carnivores; poisoning; conflict with human interests; harvesting and killing of polecats; and hybridisation. Robust survey methods and systematic monitoring programmes are urgently needed to gather up-to-date data on polecat population trends across the species’ range.

The impact of environmental chemicals on wildlife vertebrates

A plethora of papers have been published that address the affects of chemicals on wildlife vertebrates. Collectively, they support a connection between environmental pollution and effects on wildlife vertebrate populations; however, causal relationships between exposure, and reproduction or population structure effects have been established for only a few species. In a vast number of fish species, particularly in teleosts, it is accepted that EDCs affect the endocrine system of individuals and may alter sexual development and fertility. However, only few studies have demonstrated population-level consequences as a result of exposure to EDCs. The same applies to fish populations exposed to contaminants or contaminant mixtures with non-endocrine modes of action; few studies link EDCs directly to population affects. Amphibian populations are declining in many parts of the world. Although environmental chemicals have been shown to affect reproduction and development in single organism tests, the degree to which chemicals contribute to the decline of amphibians, either alone, or in concert with other factors (habitat loss, climate change, introduction of neozoa, UV-B irradiation, and direct exploitation) is still uncertain. Because reptilian endocrinology is so variable among species, EDC effects reported for individual species cannot easily be extrapolated to others. Nevertheless, for some species and locations (e.g., the Lake Popka alligators), there is considerable evidence that population declines are caused or triggered by chemical pollution. In birds, there is ample evidence for EDC effects on the reproductive system. In some bird species, effects can be linked to population declines (e.g., based on egg-shell thinning induced by DDT/DDE). In contrast, other bird species were shown to be rather insensitive to endocrine disruption. Oil spills, which also may exert endocrine effects, are usually regarded to cause only transient bird population effects, although long-term data are largely missing. Mammal population declines have been correlated with organochlorine pollution. Moreover, numerous studies have attributed reproductive and non-reproductive dysfunctions in mammals to EDC exposure. However, in the majority of cases, it is uncertain if effects at the population level can be attributed to chemical-induced reproductive effects. Evidence shows that selected species from all vertebrate classes were negatively affected by certain anthropogenic chemicals. Affects on some species are well characterized at the organismal level. However, the proof of a direct link between chemical exposure and population decline was not given for the vast majority of studied species. This review clearly shows the gaps in knowledge that must be filled for the topic area addressed. We, herewith, make a plea for long-term studies to monitor effects of various environmental chemicals on wildlife vertebrate populations. Such studies may be augmented or combined with mechanistically-oriented histological, cytological and biochemical parallel investigations, to fill knowledge gaps.

Organochlorine and heavy-metal contaminants in wild mammals and birds of Urbino-Pesaro Province, Italy: an analytic overview for potential bioindicators

Tissue samples from 56 bird and 11 mammal species of different trophic levels, collected from 1994 to 1995 from the Urbino-Pesaro area in the Marche region of central Italy, were analyzed for the presence of organochlorine compounds (polychlorinated biphenyls and p,p'-DDE) and heavy metals (Pb, Cd, Cr, and Hg). Results revealed interspecies differences in pollutant residue concentrations. A clear relationship between contaminant and trophic levels emerged depending on several factors specific to the chemicals and the organisms, the importance of dietary accumulation, and metabolic capacity as it increased toward higher trophic levels. Polychlorinated biphenyls and p,p'-DDE were found in all of the bird and mammal species analyzed (bird- or fish-eating birds), and insectivore mammals showed the highest level of these contaminants. Pb and Hg residues were also widely detected and reflected trophic-level differences. The highest concentration of Pb was found in herbivorous or bird-eating aquatic invertebrates and in insectivorous mammals, particularly in the hedgehog (Erinaceus europaeus), whereas the highest Hg levels were found in fish-eating birds. All of the other heavy metals were detected at low concentrations and represented background levels for birds and mammals, with the exception of increased amounts of Cd and Cr, respectively, found in stone marten (Martes foina) and fox (Vulpes vulpes). Data from this study provided information on baseline levels of interest to monitor status and trends in chemical residue in biota in this specific area, and therefore they represent a tool to evaluate potential ecologic, wildlife, and human health exposure.