EUROPEAN BISON ( BISON BONASUS ) IN THE CHORNOBYL EXCLUSION ZONE ( UKRAINE ) AND PROSPECTS FOR ITS REVIVAL

European bison (Bison bonasus) in the Chornobyl Exclusion Zone (Ukraine) and prospects for its revival. — Gashchak, S., Gulyaichenko, Y., Beresford, N. A., Wood, M. D. — In 2012–2016 a European bison adult bull was observed (by camera traps) in the Chornobyl Exclusion Zone (CEZ, Ukraine), west of Tovstyi Lis village. This is the first record of wild bison in Kyiv Polissya for over 300 years. The animal must have come from the Paliessie State Radioecological Reserve (PSRER, Belarus), having crossed the Pripyat river. The site where he was observed is 30–40 km from the locality where bison were introduced into the PSRER in 1996. The total area over which the bull has been observed is ca. 30–50 km2, and includes deciduous (oak, hornbeam, aspen) and mixed woodlands, and former grassy meadows now overgrown with birch, alder, aspen, pine. This constitutes the most favourable habitat type for bison available in the CEZ. The animal was only observed in February–March and August–October. Currently we are not able to judge how permanently the animal stays on this territory. Taking into account the amount of appropriate habitat in the region, size of the CEZ, protection regime and the fact that bison was a native species in the past, the CEZ could be the best area in Ukraine where a large free population of the European bison could be established.


Introduction
In April 2012, during field studies assessing the environmental quality of the 'Tovstyi Lis' site in the Ukrainian part of the Chornobyl Exclusion Zone (CEZ), some 'cow pats' (faeces) were found in a mature deciduous forest, 3-4 km westward Tovstyi Lis village.These were definitely from some species of the bovine family (Bovidae).However in Lubyanka village, which was in 5-6 km away, some cows and a bull were kept by residents, and some of these animals could have roamed this far.As far as it was known at that time, there were no wild bovines in the CEZ and hence the possibility that the faeces were from a European bison seemed unrealistic.The nearest locality they were known to be was 30-40 km to the north, in Belarus.In 1996, European bison were introduced into the Pali-essie State Radiation and Ecological Reserve (PSRER) (Deryabina, 2008).Over 10 years their number grew, and in 2005-2011 they began to spread.However, their main territory was > 30 km from the 'Tovstyi Lis' site.Importantly this territory was on the opposite bank of the Pripyat river (Deryabina, 2012).Only a few individuals had been observed closer to the Ukrainian border, but again, these observations were all on the far bank of the Pripyat.
However, motion activated camera traps deployed in 2012-2016 at this site (westward Tovstyi Lis village) captured photographs of a European bison.The aim of this paper is to summarise records of bison in the CEZ in 2012-2016 and to discuss the status of the species in this area and the potential of the region for European bison conservation.

Methodology
From November 2014 to July 2016, Chernobyl Centre for Nuclear Safety, Radioactive Waste and Radioecology (Ukraine) together with the University of Salford and the Centre of Ecology & Hydrology (UK) carried out an assessment of biodiversity of macrofauna in several areas of the CEZ using motion activated camera traps (see TREE project: http://tree.ceh.ac.uk).
The TREE project deployed 42 camera traps (Ltl Acorn 6210MC) at three sites in the CEZ, each of 5 km radius.One site was situated near the villages Tovstyi Lis and Buda about 25 km westward the Chornobyl Nuclear Power Plant.Within this site, 14 camera traps were deployed.Coordinates were calculated using a random number algorithm, the actual position used for each camera was the most appropriate place within 200-300 m of the random coordinate.Selection criteria for locating the camera included the presence of animal trails.Preference was given to the sites where the movement of animals was channelled by natural barriers (water, thickets etc.).The camera traps were run in one location for 7-8 weeks, then they were moved to new points within the overall study site.The cameras were moved six times (i.e. the cameras were each run at seven different locations).The main study ran from November 2014 to January 2016.Subsequently, until July 2016, four camera traps continued to be deployed, each camera being set-up at three additional locations.In total cameras were located at 97 locations in the study area, and the total duration of deployment was 6485 days.A more detailed description of the methodology used for the camera trap study can be found in article by S. Gashchak et al. (2016).
A further set of motion activated cameras have been in use at this site since May 2012.This was for a national project which was trying to identify areas of the CEZ of 'valuable environmental status' (Gashchak, Domashevsky, 2013;Petrov, Gashchak, 2013).A range of camera models (Ltl Acorn 5210A, Ltl Acorn 6210M, Bushnell 119437c, DLC Covert Red 40, Weltar 8210A and Browning Strike Force) were used.The number of camera traps deployed varied from 3 to 7, and the duration of deployment at a given location was from two weeks to more than a year.The cameras were used at 35 points for a total duration of 3796 days.Between January to November 2016 the cameras were sited at points where it was considered most likely to observe European bison based on known habitat preference (Korochkina, 1969 a;Baskin, 1979;Kozlo et al., 1999;Deryabina, 2012).
At every point, during the setting up of the camera trap, a preliminary shooting of the site was taken (the study camera) with measurement poles in place.This was in order to be able to estimate animal size once photographs were obtained.Twenty 1-meter poles were placed in three paralleled rows, with 1 meter gaps, the first pole was located 3 m from the camera and the last at 8 m.The poles had markings at every 20 cm.Images of measurement poles and animals were overlaid using Adobe Photoshop to allow animal dimensions to be estimated (accuracy of estimation ca. 5 cm).

Results
Since April 2012 European bison were recorded at the Tovstyi Lis/Buda site 25 times: 'cow pats' were found on five occasions at different locations; photographic records were obtained on 19 occasions from 7 points; and a there was a confirmed oral report of a sighting at an additional point (tab.1).All the observations were made in the same area: to the west and south of Tovstyi Lis village, inside woodland or close to its edge (fig.1).Almost all pictures were taken during the period 11:30 to 24:00, only one photograph was taken earlier in the morning.Mostly the animal was passing the camera and sometimes grazing grasses.At point No. 5 the bison came several times to scratch on a bridge side post, where he stayed for up to 17 min (fig. 2 and 3).Although the camera traps were deployed at the site for a long period, and the bison appeared in the same points several times, he was observed only during February-March and August-October.There were no data for other months.
It is not possible to comment on the animals' movement routes.However, between August and October 2016 the animal walked over the site at least three times from the north-west (point No. 5) to south-east (No. 12) and back, covering at least 5.3 km (straight line distance) over 2-10 days (5.5 d on average).Based on the photographs, there appears to be only one individual that has been observed to date.This is an adult bull; height at shoulder approximately 135-140 cm and about 120-125 cm on the rump.The animal looks in good condition (fig. 2 and 3).

Past history of European bison in Kyiv Polissya
In the past European bison were common inhabitants of most regions of modern Ukraine (Kirikov, 1979 a) though it is not clear if it was present in the territory of the modern CEZ.Written evidence and fossils records suggest that the bison was abundant in different regions of Polissya (Kirikov, 1979 a).However, almost all written/fossil records originate from the forest-steppe zone (which is to the south of the CEZ) or in forest zone (as is the CEZ) but in north-west of Ukraine and in Belarus.Kirikov cited results from Volovich (in: Kirikov, 1979 b): in the 16th century, European bison undertook mass passages from forest-steppe areas near the Dnipro river to 'pripyat puscha' (dense virgin forest).Regardless of their past distribution, bison had disappeared completely from most regions of Ukraine by the 18th century due to deforestation of lands and eradication by humans (Kirikov, 1979 a).
In the mid-1990's there was an attempt to return European bison back to the Kyiv Polissya.At that time, the programme of species conservation was failing because of a lack of available habitat where there would be no conflicts with man (Kryzhanovsky, 2007).Small isolated sub-populations still existed in Ukraine but these served to rescue the species from local extinction rather than being home to free populations, bison require large territories with the ability for contact between subpopulations.Social and economic crises contributed to a further reduction of the bison population in the Ukraine (Gerus, Kryzhanovsky, 2005;Kryzhanovsky, 2007;Parnikoza et al., 2010;Red Book of Ukraine, 2009).Consequently, the appearance of a large 'protected' territory in the north of Kyiv oblast, where there was no human population, opened up new prospects (Kryzhanovsky, 2007).
In 1998 two animals (a male and a female) were transported from the Askania Nova reserve (south Ukraine) and placed in an enclosure near Chornobyl town together with Przewalski horses (Program 'Fauna', 1998).Unfortunately, the female died within the first months as the result of an injury and the bull died of unknown reasons after 2.5 years.
Therefore, the first free bison (as reported here) must have come to Kyiv Polissya from Belarus, without the help of people.Favourable development of the situation in the PSRER fostered this.

Reintroduction of European bison in neighbour territory of Belarus
Sixteen animals (4 bulls and 12 females) were transported from Bialoweza Puscha National Park (Belarus) in 1996, and placed into an enclosure near the village of Babchin in the PSRER (Deryabina, 2008).One and a half years later they were released into the wild.Over 10 years their herd increased up to 116 animals in 2016 (Penkevich, 2016).Since 2005 the bison have begun to explore new territories, mostly in the north.A few individuals moved to southern areas of the PSRER but only on the left (east) bank of the Pripyat river (Deryabina, 2012).Growth of the herd and the number of mature bulls were main reasons for dispersion (Deryabina, 2012).It would appear that at least one bull swam across the Pripyat river and reached the Ukrainian part of the CEZ, with faeces being found in 2012.The width of the Pripyat river in this area is 100-200 meters, and the depth approximately 3-4 meters (State water cadastre, 1967).Such 'swim passages' of bison were well-known in the past and the site of river crossings used to be places for hunting (Kirikov, 1979 a).According to long-term studies in 'Bialoweza Puscha' (Korochkina, 1973) 'distant roaming' takes place periodically, and is provoked both by expulsion of males (competitors) from the herd and by the search for new territories when food is scarce.

The observed facts referring to ecology of European bison
Usually European bison have relatively small territories of 450-900 ha (Korochkina, 1973).A similar range was observed for 'our' bison, the area of forest and meadow habitats on which he roamed in August-October 2016 was approximately 500-700 ha.Baskin (1979) reports that European bison that travelled far could come back to the same locations.However, the annual behaviour of the animal observed in the CEZ is difficult to comment on.Whilst, in the periods November to January and April to July there were no observations, it is in these seasons that bison are the most sedentary (Korochkina, 1973;Baskin, 1979).Distance and activity of movement increases at the end of winter -beginning of spring, in the period of poor food availability and again in the mating period (August-September).It is possible that the observed bison periodically returns to the Belarussian territory.However, it is also possible that during the periods of his 'absence' he is somewhere close by and that the most appropriate habitats with better food availability had no camera traps.Studies would be needed to clarify this.
The fact that observations of bison have been made in the same area for four years suggests that the site is not an occasional visiting place.The CEZ is a large area (2600 km 2 ) but the animal came over tens of kilometres and appears to have settled at this particular site.
The site is between a large forests, spreading hundreds of kilometres to the west, and former agricultural landscapes that are now overgrown with trees and bushes.This site has a relatively high amount of deciduous and mixed forests on hygrophilous soils with rich mineral supply (Petrov, Gashchak, 2013).Near to 20-25 % of the forest is 80 to 150 years old or older, which is unusual for the CEZ where most trees are younger.Approximately 13 % of the total area over which bison activity has been observed are oak forest (Quercus robur L.), and up to 9 % aspen forest (Populus tremula L.); this area has a higher proportion of these habitats than much of the rest of the CEZ.Hornbeam (Carpinus betulus L.) is common in the understory layer of the area favoured by the bison and in some places it forms pure stands.There is a lot of ash (Fraxinus excelsior L.), maple (Acer sp.), rowan (Sorbus aucuparia L.) and spindle (Euonymus sp.).These species are reported as the most preferred among tree and bushes in the diet of bison, and are typical of the species' main habitats in Europe (Korochkina, 1969 a;Baskin, 1979;Kozlo et al., 1999).The pine and mixed forests which are more abundant than deciduous in the study area grow in hygrophilic (moist) conditions and have a rich layer of grasses and herbs which are consumed by bison (Korochkina, 1969 b;Baskin, 1979;Kozlo et al., 1999).Up to 35 % of the study site is areas of natural reforestation of former meadows/agricultural land where 10-30 years old birch trees now predominate with abundant grasses.
The conditions at the study site are not uncommon in the CEZ, however there are not many places where these habitats occupy such a large area (30-50 km 2 ).If we had wanted to re-introduce European bison into the CEZ, it would be difficult to find a more suitable area.

Prospects of European bison revival in the CEZ
As a whole the CEZ has many localities of similar quality and habitat composition (fig.4).The largest among them are forests with high component of oak in the south-east near the villages of Paryshev and Ladyzhychi.Suitable habitat also includes areas on the north of the Pripyat river's leftbank, between the villages of Usiv, Mashevo and Gorodchan.It is possible that bison have been there or are in these areas but that no observations have been made.These sites are closest to the Belarussian reserve and those localities where bison were observed (in Belarus) in 2005-2011(Deryabina, 2012)).
Bison prefer habitats with meadows and overgrown logging areas, avoiding residing in vast total woodland (Korochkina, 1973;Baskin, 1979).Much of the most appropriate habitat for bison in the CEZ is surrounded by dense woodlands (fig.4), this is likely to make these areas less attractive to the bison though we speculate that they may be temporarily used during migrations or in winter.
Given its size, natural conditions and protection regime, the CEZ is a good prospective location for establishing a free (natural) population of bison (as opposed to the bison elsewhere in the Ukraine which are restricted to small areas).This is especially the case given that with the neighbouring PSRER (Belarus) the total area with very little human activity is up to 4760 km 2 .In the opinion of Kryzhanovsky (2007), the CEZ has the potential to be the largest Ukrainian reserve for bison, with a total herd of up to 500.
But currently a developing population exists only on Byelorussian territory.In theory, bison coming from Belarus to Ukraine could create a new herd (as was observed for Przewalski horses migrating to the PSRER from the CEZ (Deryabina, 2013)), but this is a future prospect taking into account territorial behaviour of maternal herds (rather sedentary) and the relatively low birth rate (Baskin, 1979).There is no governmental programme to support the reintroduction of bison in the CEZ (Parnikoza et al., 2010).There is also no organisation which could oversee the protection of bison in the CEZ.The recent decision to establish the 'Chornobyl radiation and ecological biosphere reserve' in the Ukraine (Decree of the President, 2016) should be positive for wildlife.However, only time will show if it will be helpful in returning the bison to 'Pripyat Puscha'.