Wolves in Chernobyl Exclusion Zone

We re-analyzed field data concerning potential effects of ionizing radiation on the abundance of mammals collected in the Chernobyl Exclusion Zone (CEZ) to interpret these findings from current knowledge of radiological dose–response relationships, here mammal response in terms of abundance. In line with recent work at Fukushima, and exploiting a census conducted in February 2009 in the CEZ, we reconstructed the radiological dose for 12 species of mammals observed at 161 sites. We used this new information rather than the measured ambient dose rate (from 0.0146 to 225 µGy h⁻¹) to statistically analyze the variation in abundance for all observed species as established from tracks in the snow in previous field studies. All available knowledge related to relevant confounding factors was considered in this re-analysis. This more realistic approach led us to establish a correlation between changes in mammal abundance with both the time elapsed since the last snowfall and the dose rate to which they were exposed. This relationship was also observed when distinguishing prey from predators. The dose rates resulting from our re-analysis are in agreement with exposure levels reported in the literature as likely to induce physiological disorders in mammals that could explain the decrease in their abundance in the CEZ. Our results contribute to informing the Weight of Evidence approach to demonstrate effects on wildlife resulting from its field exposure to ionizing radiation.

In the initial aftermath of the 1986 Chernobyl accident there were detrimental effects recorded on wildlife, including, mass mortality of pine trees close to the reactor, reduced pine seed production, reductions in soil invertebrate abundance and diversity and likely death of small mammals.

More than 30 years after the Chernobyl accident there is no consensus on the longer-term impact of the chronic exposure to radiation on wildlife in what is now referred to as the Chernobyl Exclusion Zone. Reconciling this lack of consensus is one of the main challenges for radioecology. With the inclusion of environmental protection in, for instance, the recommendations of the International Commission on Radiological Protection (ICRP), we need to be able to incorporate knowledge of the potential effects of radiation on wildlife within the regulatory process (e.g. as a basis on which to define benchmark dose rates).

In this paper, we use examples of reported effects on different wildlife groups inhabiting the Chernobyl Exclusion Zone (CEZ) as a framework to discuss potential reasons for the lack of consensus, consider important factors influencing dose rates organisms receive and make some recommendations on good practice.

Measurements of external contaminant exposures on individual wildlife are rare because of difficulties in using contaminant monitors on free-ranging animals. Most wildlife contaminant exposure data are therefore simulated with computer models. Rarely are empirical exposure data available to verify model simulations, or to test fundamental assumptions inherent in exposure assessments. We used GPS-coupled contaminant monitors to quantify external exposures to individual wolves (Canis lupus) living within the Belarus portion of Chernobyl’s 30-km exclusion zone. The study provided data on animal location and contaminant exposure every 35 min for 6 months, resulting in ~6600 individual locations and ¹³⁷Cs external exposure readings per wolf, representing the most robust external exposure data published to date on free ranging animals. The data provided information on variation in external exposure for each animal over time, as well as variation in external exposure among the eight wolves across the landscape of Chernobyl. The exposure data were then used to test a fundamental assumption in screening-level risk assessments, espoused in guidance documents of the U.S. Environmental Protection Agency and U.S. Department of Energy, — Mean contaminant concentrations conservatively estimate individual external exposures. We tested this assumption by comparing our empirical data to a series of simulations using the ERICA modeling tool. We found that modeled simulations of mean external exposure (10.5 mGy y⁻¹), based on various measures of central tendency, under-predicted mean exposures measured on five of the eight wolves wearing GPS-contaminant monitors (i.e., 12.3, 26.3, 28.0, 28.8 and 35.7 mGy y⁻¹). If under-prediction of exposure occurs for some animals, then arguably the use of averaged contaminant concentrations to predict external exposure is not as conservative as proposed by current risk assessment guidance. Thus, a risk assessor’s interpretation of simulated exposures in a screening-level risk analysis might be misguided if contaminant concentrations are based on measures of central tendency. We offer three suggestions for risk assessors to consider in order to reduce the probability of underestimating exposure in a screening-level risk assessment.

Scavenging increases the connectivity of food webs yet scavenging links between adjacent ecosystems are poorly characterized. Here we explored the movement of aquatic carrion into terrestrial food webs by vertebrate scavengers across two habitat types in the Chernobyl Exclusion Zone (CEZ). We used motion activated cameras to monitor experimentally placed fish carcasses to quantify the composition and efficiency of vertebrate scavengers of canal and river communities in the CEZ. We conducted 83 trials that were scavenged by 10 mammalian and 5 avian species. Species diversity, percentage consumed, scavenging efficiency, and time until scavenged differed between canal and river trials. Mesocarnivores were the predominant scavengers in both habitats, and we observed greater scavenger efficiency and higher diversity (but lower richness) among river trials. Variation in scavenging among habitats was attributed to the interplay of higher detection rates in the river habitats and differences in scavenger community, as canals intersected a greater diversity of habitat types. Our data suggest the CEZ supports a highly diverse and efficient vertebrate scavenging community with important implications for the redistribution of scavenging-derived nutrients and the connectivity of adjacent ecosystems. Future studies should focus on species-specific patterns of nutrient redistribution and ultimate carcass deposition sites to further our understanding of the mechanisms connecting aquatic and terrestrial systems via scavenging of aquatic nutrients by terrestrial scavengers.

The Chernobyl Exclusion Zone (CEZ) is a ~ 4300 km2 area in Belarus and Ukraine that remains heavily contaminated with radiation from the nuclear accident of 1986. Long standing controversy persists on the fate of wildlife within the CEZ following human abandonment of the area. Human residency remains extremely sparse, and the CEZ has become a refuge for some populations of wildlife, including gray wolves (Canis lupus). Using GPS telemetry, we documented the first long-distance movements of a young (1–2 years) male wolf from the CEZ into the surrounding landscape. The wolf traveled 369 km from its home range center over a 21-day period in February 2015. In the 95 days prior to dispersal, the wolf maintained a home range of ~ 28 km2, with daily displacements rarely exceeding 5 km. With the onset of dispersal, daily displacement increased to a mean of 16.8 km. The dispersal of a young wolf isan important observation because it suggests that the CEZ may serve as a source for some wildlife populations outside of the CEZ, and raises questions about the potential spread of radiation-induced genetic mutations to populations in uncontaminated area.

Although nearly 30 years have passed since the Chernobyl Nuclear Power Plant accidentnear the town of Pripyat, Ukraine, the status and health of mammal populations within the Chernobyl Exclusion Zone (CEZ) remain largely unknown, and are of substantial scientific and public interest. Information regarding the response of flora and fauna to chronic radiation exposure is important in helping us understand the ecological consequences of past (eg Chernobyl and Fukushima) and potential future nuclear accidents. We present the results of the first remote-camera scent-station survey conducted within the CEZ. We observed individuals of 14 mammalian species in total; for those species with sufficiently robust visitation rates to allow occupancy to be modeled (gray wolf [Canis lupus], raccoon dog [Nyctereutes procyonoides], Eurasian Boar [Sus scrofa], and red fox [Vulpes vulpes]), we found no evidence to suggest that their distributions were suppressed in highly contaminated areas within the CEZ. These data support the results of other recent studies, and contrast with research suggesting that wildlife populations are depleted within the CEZ.

Following the 1986 Chernobyl accident, 116,000 people were permanently evacuated from the 4,200 km2 Chernobyl exclusion zone [1]. There is continuing scientific and public debate surrounding the fate of wildlife that remained in the abandoned area. Several previous studies of the Chernobyl exclusion zone (e.g. 2, 3) indicated major radiation effects and pronounced reductions in wildlife populations at dose rates well below those thought 4, 5 to cause significant impacts. In contrast, our long-term empirical data showed no evidence of a negative influence of radiation on mammal abundance. Relative abundances of Elk, Roe deer, red deer and wild Boar within the Chernobyl exclusion zone are similar to those in four (uncontaminated) nature reserves in the region and wolf abundance is more than 7 times higher. Additionally, our earlier helicopter survey data show rising trends in Elk, Roe deer and wild Boar abundances from one to ten years post-accident. These results demonstrate for the first time that, regardless of potential radiation effects on individual animals, the Chernobyl exclusion zone supports an abundant mammal community after nearly three decades of chronic radiation exposures.

Political events associated with the disintegration of the USSR and the creation of the independent stateof Ukraine led to changes in economical situation, which in their turn affected the structure of the productive forces and led to the changes in environmental conditions. Demographic trends and changes in agriculture and mining affected significantly the distribution of the human population of the country. There appeared relative-ly large areas with a long history of development, where production activities were phased out and hence the population reduced. Accordingly, in these areas the process of restoring the natural environment began turning them into new habitats for animals. There is a problem of environmental impact assessment and, above all, of the environmental potential. The existing in the country theory and practice of environmental measures are based on the conservation paradigm of undisturbed natural systems and do not consider the methods for their recovery. As a result, the question of value of anthropogenically modified areas remains a subject of debate.Solving of this problem is possible by exploring the indicative groups of fauna on the anthropogenically modified areas, which remain for a long time without human influence. The Exclusion Zone formed as a result o fa disaster at the Chernobyl Nuclear Power Plant in 1986 can be suggested. Large carnivores are recommend-ed as an indicative group of fauna.

Fauna composition of the large carnivores in Ukraine

At present a group of large carnivores of Ukraine includes three species: grey wolf, brown bear and Eurasian lynx. Bear and lynx are listed as endangered species. During their long history large carnivores have been objects for extermination, hunting or number control or an object of conservation. Irrespective of their status these species have a considerable potential of conflict with man.

Wolf

The wolf (Canis lupus Linnaeus, 1758) is a widespread in Ukraine predator characterized by high environmental plasticity. The number of wolves in Ukraine is between 2, 500 and 3, 000 individuals before a breeding season at the end of a hunting season. The maximum population size is reached immediately after birth and held till the autumn battue on the ungulates, when the first in the year mass elimination of wolves occurs.The pack sizes vary. For Ukraine, an average pack size is from 5 to 7 animals, but there are groups of 3—12 wolves and the largest variability in the pack size is typical for the steppe zone.A pack in Ukraine occupies a patch from 130 km2 in the steppe zone to 390 km2 in the woodland (Shkvyrya, 2008). The wolf in Ukraine preys mainly on wild ungulates, rodents and domestic animals. Among the secondary feed are wild and cultivated plants, birds, fish, reptiles, amphibians, and insects. Preying activity of the wolf and the choice of prey depend on the season and marital status (a pack member or not, young or old). The research of this aspect in Ukraine reveals the predominance of large wild animals among the prey of packs and a large share of secondary feed and domestic animals preyed by single wolves (Shkvyrya, Kolesnikov 2008).Wolf is a game species. Hunting on wolf is not regulated in fact; moreover, poaching is actually encouraged as regulatory measure. The limitation of hunting period from October to March will not be of practical use due to the fact that it is quite difficult to hunt a wolf by legal methods in this period.