Use of abandoned structures by Przewalski’s wild horses and other wildlife in the Chernobyl Exclusion Zone

Abstract

Przewalski’s wild horses (Equus ferus przewalski) are an endangered species and current conservation efforts aim to maintain genetic diversity and reintroduce wild populations. From 1998 to 2004, 36 Przewalski’s horses were introduced in the Chernobyl Exclusion Zone (CEZ) with no subsequent direct management, and current population size and genetic diversity are unknown. We used remote cameras positioned at the entrance of abandoned structures within the CEZ to elucidate visitation of these structures by Przewalski’s horses and other large mammals to assess the use of this method for monitoring the horse population within the CEZ. We estimated frequency of structure use in winter (Nov 2016–Feb 2017) and summer (Mar 2018–Oct 2018) periods and estimated basic group characteristics such as group type (all male vs. mixed sex), group size, and number of foals. Przewalski’s horses were detected 35 times at 9 of 10 monitored structures in winter and 149 times at all 8 monitored structures in summer. Eight other mammalian species were documented using abandoned structures. Mixed sex groups of horses contained 5.30 ± 0.25 adults and 1.00 ± 0.12 foals (mean ± S.E.). All-male groups contained 1.59 ± 0.15 individuals. Our data suggest Przewalski’s horses routinely use abandoned structures in the CEZ with visitation patterns tending to be nocturnal in winter and crepuscular in summer. Congregation of horses in these structures could have implications for future monitoring of the population by providing detailed information on demographics, population size, and genetic diversity which would benefit management plans for this population and provide a baseline for future work.

Full text

SHORT COMMUNICATION
Use of abandoned structures by Przewalski’s wild horses and other
wildlife in the Chernobyl Exclusion Zone
Peter E. Schlichting
1
&Valery Dombrovski
2
&James C. Beasley
1
Received: 18 April 2019 /Accepted: 2 August 2019
#Mammal Research Institute, Polish Academy of Sciences, Bia?owie?a, Poland 2019
Abstract
Przewalski’swildhorses(Equus ferus przewalski) are an endangered species and current conservation efforts aim to maintain
genetic diversity and reintroduce wild populations. From 1998 to 2004, 36 Przewalski’s horses were introduced in the Chernobyl
Exclusion Zone (CEZ) with no subsequent direct management, and current population size and genetic diversity are unknown.
We used remote cameras positioned at the entrance of abandoned structures within the CEZ to elucidate visitation of these
structures by Przewalski’s horses and other large mammals to assess the use of this method for monitoring the horse population
within the CEZ. We estimated frequency of structure use in winter (Nov 2016–Feb2017)andsummer(Mar2018–Oct 2018)
periods and estimated basic group characteristics such as group type (all male vs. mixed sex), group size, and number of foals.
Przewalski’s horses were detected 35 times at 9 of 10 monitored structures in winter and 149 times at all 8 monitored structures in
summer. Eight other mammalian species were documented using abandoned structures. Mixed sex groups of horses contained
5.30 ± 0.25 adults and 1.00 ± 0.12 foals (mean ± S.E.). All-male groups contained 1.59 ± 0.15 individuals. Our data suggest
Przewalski’s horses routinely use abandoned structures in the CEZ with visitation patterns tending to be nocturnal in winter and
crepuscular in summer. Congregation of horses in these structures could have implications for future monitoring of the population
by providing detailed information on demographics, population size, and genetic diversity which would benefit management
plans for this population and provide a baseline for future work.
Keywords Camera traps .Chernobyl Exclusion Zone .Population monitoring .Przewalski’swildhorse
Introduction
The Chernobyl nuclear accident in 1986 created an unprece-
dented radiological containment issue, resulting in the crea-
tion of a 4300-km
2
restricted access area spanning the modern
borders of Ukraine and Belarus. This area, referred to as the
Chernobyl Exclusion Zone (CEZ), has remained relatively
untouched, allowing for natural reclamation of a primarily
agricultural and forest matrix. Over 190 abandoned human
villages and towns are interspersed throughout the landscape,
consisting of thousands of abandoned structures. These struc-
tures range from abandoned apartment complexes to barns
and other former livestock holding facilities, and represent
unique habitat for the diverse wildlife that now inhabit the
CEZ (Baker and Chesser 2000; Deryabina et al. 2015;
Webs t e r e t al. 2016; Schlichting et al. 2019). The large size
and restricted human access also has made the CEZ a target
for the introduction of species of conservation concern includ-
ing European bison (Bison bonasus) and Przewalski’swild
horses (Equus ferus przewalski).
The endangered Przewalski’s horse is the last remaining
subspecies of wild horse (King et al. 2015), whose popula-
tions declined rapidly due to hunting, habitat loss, harsh win-
ters, and competition with domestic livestock, leading to their
extinction in the wild in the mid-twentieth century (Ryder
1993; Bouman and Bouman 1994). All extant Przewalski’s
horses are descended from a small number of captive individ-
uals (n= 13), and captive populations are subject to a compre-
hensive breeding program where maintenance of genetic
Communicated by: Marietjie Landman
*Peter E. Schlichting
peter.e.schlichting@asu.edu
1
Savannah River Ecology Laboratory, Warnell School of Forestry and
Natural Resources, University of Georgia, P.O. Drawer E,
Aiken, SC 29802, USA
2
Laboratory of Molecular Zoology, National Academy of Sciences, 27
ul. Academichnaya, 220072 Minsk, Belarus
Mammal Research
https://doi.org/10.1007/s13364-019-00451-4

diversity is a priority. A second management priority is the
reintroduction of sustainable wild populations, which has oc-
curred at five locations in Mongolia and China. In addition,
from 1998 to 2004, 36 Przewalski’s horses were released into
the CEZ near the town of Chernobyl as an experimental pop-
ulation, and this population gradually spread north throughout
the zone (Zharkikh and Yasynetska 2008) and occupied the
Belarussian portion of the CEZ, the Polesie State Radiation
Ecological Reserve (PSRER), by 2007 (Deryabina 2015). The
CEZ population was monitored 10 years post-release and in-
creased to a maximum of 65 individuals, but because of their
small population size, poaching, and limited gene flow, the
population remains at risk (Zharkikh and Yasynetska 2008).
Evidence suggests that Przewalski’s horses use abandoned
structures in the CEZ, based on the presence of feces (Klich
et al. 2017), and these structures are assumed to be used as
thermal refugia. However, the frequency and extent to which
horses (and other wildlife) use these structures is currently
unknown.
To address this knowledge gap, we conducted a pilot study
to assess the use of human structures by Przewalski’shorses
and other wildlife in the CEZ. By placing motion activated
cameras at the entrances of abandoned structures, we estimat-
ed frequency and diel patterns of use by Przewalski’shorsesin
winter and summer seasons. In addition, we assessed popula-
tion characteristics of groups visiting structures including
group size, group type (mixed sex or all-male groups), and
number of foals in mixed sex groups during summer. Finally,
we examined the role of abandoned structures as refugia dur-
ing summer. This information can be used to improve moni-
toring and management strategies for the Przewalski’shorse
population in the CEZ.
Methods
We deployed motion-activated game cameras (A-25i,
Moultrie, USA; Attack IR, Cuddeback, USA; 2.6C Willfine,
Suntek,China)toassesswinter(n= 10, November 20, 2016
to February 14, 2017) and summer (n= 8, March 23, 2018 to
October 23, 2018) use of abandoned structures by
Przewalski’s horses and other wildlife in the PSRER
(Fig. 1). Cameras were placed within structures originally
used for livestock husbandry (cattle, sheep, and horses) where
the presence of Przewalski’s horses was anticipated based on
observations of horse fecal material. Cameras were set ~ 1.2 m
off the ground at entrances to maximize detection of horses
and other large mammals and programmed to record a burst of
three photos when triggered. Photos were delineated into in-
dependent visits per species separated by a minimum of 6 h.
Visits were used to determine presence, visits per structure,
and visits per trap night in winter and summer trials. In addi-
tion, we evaluated visits by horses during the winter and
summer periods by creating activity curves using a non-
parametric kernel density approach (Ridout and Linkie
2009). Activity curves were created with the package “over-
lap”(Meredith and Ridout 2014)inprogramR(R
Development Core Team 2018).
Extreme cold during winter trials made cameras less reli-
able, meaning group composition and the role of structures as
refugia was estimated for summer trials only. Group size was
determined by recording the maximum number of individuals
present in a single photo within a visit. The lack of identifiable
marks on Przewalski’s horses and difficulty in differentiating
sub-adults from adults meant that group composition could
only be reliably recorded into two types: mixed sex (at least
one male and female identified) and all-male groups (all indi-
viduals identified as male). Groups where a female could not
be verified but included a foal were considered a mixed sex
group. Visits where group composition could not be deter-
mined were labeled as unknown. The role of structures as
thermal refugia was tested by comparing maximum tempera-
tures (Ttest) and days with rainfall (chi-squared test) on days
with visits to days without. Meteorological data were obtained
within the PRSER at the Masany Research Station (Fig. 1).
Results
Przewalski’s horses were detected 35 times at 9 of 10 moni-
tored structures (Fig. 2a, b) in winter trials and visited all 8
monitored structures 149 times in summer (Fig. 2c, d).
Structures were visited an average of 3.89 ± 0.77 times (range
1–8) during 655 trap nights in winter (0.05 visits/trap night).
Summer trials totaled 1339 trap nights (0.11 visits/trap night)
with an average of 18.63 ± 4.06 horse detections per structure
(range 5–34). Przewalski’s horses used structures for extended
periods of time (>5 h), including as loafing, breeding, and
sleeping locations (Fig. 2b), resulting in 4668 and 7685 photos
in winter and summer, respectively. Horses primarily used
structures nocturnally in winter while summer visits occurred
throughout the day with greater use during crepuscular pe-
riods (Fig. 3). The number of days between visits averaged
6.27 ± 0.65 during summer. We detected eight other mid- to
large-sized mammals using abandoned structures in summer
including brown hare (Lepus europaeus,n=34 detections),
red deer (Cervus elaphus,n= 13 detections), moose (Fig. 2e,
Alces alces,n= 63 detections), wild boar (Sus scrofa,n=2),
red fox (Vulpes vulpes,n= 5 detections), raccoon dogs
(Nyctereutes procyonoides,n= 9 detections), Eurasian lynx
(Fig. 2f,Lynx lynx,n= 9 detections), and wolves (Canis lupus,
n= 8 detections), along with several avian and bat species.
Przewalski’s wild horse groups averaged 3.31 ± 0.22 indi-
viduals per visit across all group types during summer. Mixed
sex groups were detected visiting structures on 53 occasions
and contained 5.30 (± 0.25) adults and 1.00 (± 0.12) foals on
Mamm Res

average. Mixed groups contained 2–11 adults and 0–3foals,
and foals were first detected May 4th. All-male groups visited
monitored structures on 44 occasions and were smaller than
mixed sex groups, containing 1.59 ± 0.15 individuals on av-
erage and ranging from 1 to 4 adults. Groups of unknown
composition averaged 1.73 ± 0.11 individuals. Groups of sim-
ilar type and size were commonly detected on the same cam-
era for several consecutive days followed by extended periods
without visits (>40 days). Temperature (p= 0.81) and days
with rainfall (p= 0.91) did not differ between days with and
without visits.
Discussion
Przewalski’s horses and other wildlife appear to regularly use
abandoned structures in the CEZ. Visits occurred throughout
both night and day, and horses were documented loafing,
breeding, and sleeping in structures. Successive visits tended
to be temporally clustered, indicating groups repeatedly use
structures when in that portion of their home range, but struc-
tures may go unvisited for extended periods of time. No other
species documented using abandoned structures appeared to
stay in them for extended periods, but we likely missed detec-
tions of small bodied species because cameras were set spe-
cifically to detect horses and other large ungulates (>1 m
high). Horses were documented visiting structures more dur-
ing summer trials but this is likely an artifact of poor camera
performance in extreme cold temperatures. Alternatively,
summer months with the greatest number of visits
corresponded to increases in blood sucking flies (families
Ceratopogonidae, Simuliidae, and Tabanidae) and horses
could be visiting abandoned structures as a respite from these
pests. Horses used unmonitored barns (based on the presence
of feces) as well as the barns we monitored, and the lack of
climatic influences based on detections could be misleading
based on our small sample size. Horses primarily used barns at
night in winter suggesting they may serve as thermal refugia,
but this hypothesis should be more thoroughly tested, possibly
with paired climate loggers in a greater number of structures.
The extensive and repeated congregation of Przewalski’s
horses in abandoned structures could have implications for
future monitoring of the population in the CEZ. Przewalski’s
wild horses in the Ukrainian portion of the CEZ also use
abandoned structures (Klich et al. 2017), suggesting these
congregation areas represent unique focal points for which
monitoring of horses with remote cameras may be feasible
across the CEZ. Our results provided estimates of group size
and usage, but monitoring a greater number of structures,
using multiple cameras per structure, and incorporating video
surveillance could allow for more accurate estimates of pop-
ulation structure including age/sex ratio, birth rates, herd num-
ber, herd composition, and abundance. These represent critical
population parameters that, in conjunction with climatic vari-
ables, influence the long-term viability of reintroduced
Przewalski’s horse populations (Slotta-Bachmayr et al.
Fig. 1 Map of the Belarussian
portion of the Chernobyl
Exclusion Zone, the Polesie State
Radiation Ecological Reserve
(PSRER), indicating the location
of monitored barns and the
Masany Research Station. The
inset displays the location of the
PSRER (in black) within Belarus
Mamm Res

2004). Identification of key parameters for population growth
and their threshold values could help optimize management
objectives for this population.
Congregation of Przewalski’s horses in abandoned struc-
tures could also provide valuable information about popula-
tion characteristics and viability using non-invasive genetic
sampling (King et al. 2018). Genetic capture-recapture
methods (Lukacs and Burnham 2005) could provide abun-
dance estimates as well as estimates of survival and popula-
tion growth if the population were repeatedly sampled. Other
reintroduced Przewalski’s horse populations have displayed
increased genetic drift and inbreeding compared to their
founding population (Liu et al. 2014). Although genetic diver-
sity is currently unknown, the CEZ population has likely ex-
perienced similar losses in diversity since introduction.
Comparisons of genetic diversity and inbreeding coefficients
to reintroduced populations in China and Mongolia as well as
the founding population in Askania Nova Biosphere Reserve
would benefit management plans for this species and provide
baseline population information for future work in the CEZ.
The future of Przewalski’s horses in the wild depends on
introductions that maintain sustainable and genetically diverse
Fig. 2 Przewalski’s horses
(Equus ferus przewalski) and
other wildlife occupying
abandoned structures in the
Chernobyl Exclusion Zone.
Mixed sex groups (a–c)andall-
male groups (d) were documented
occupying monitored barns
previously used for livestock
husbandry in winter (a,b)and
summer (c,d). Eight other
species, including moose (Alces
alces,e) and European lynx (Lynx
lynx,f), were detected utilizing
abandoned structures
Fig. 3 Diel distribution of Przewalski’s wild horse visits to abandoned
structures in the Chernobyl Exclusion Zone in winter and summer
periods. Sample sizes (n) denote the number of visits per sampling period
Mamm Res

populations (Sarrazin and Barbault 1996; Van Dierendonck
and Wallis de Vries 1996). Successful reintroduction of
Przewalski’s wild horses have generally included intensive
monitoring and periodic supplementation with individuals
from captivity (Boyd and Bandi 2002; Souris et al. 2007;
Xia et al. 2014). The population in the CEZ offers a unique
opportunity to evaluate a reintroduction with limited direct
management and future investigations could identify potential
management needs such as mitigating the genetic conse-
quences of founder effect and limited gene flow. In addition,
the use of a range of structures by a wide array of species
offers an opportunity to understand the importance and impact
of former human settlements on wildlife populations in the
CEZ and other areas abandoned by people, as well as the
potential importance of these structures to horses in the CEZ.
Acknowledgments We thank the Polesie State Radioecological Reserve
staff and C. Love for field assistance and discussion, as well as the
Ministry of Education and Research for their support. This material is
based upon work supported by the Department of Energy Office of
Environmental Management under Award Number DE-EM0004391 to
the University of Georgia Research Foundation.
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