Annuaire de l’Université de Soa “St. Kliment Ohridski”
Faculte de Biologie
2016, volume 101, livre 4, pp. 23-32
Youth Scientic Conference “Kliment’s Days”, Soa 2015
VIGILANCE BEHAVIOUR IN ROE DEER
(CAPREOLUS CAPREOLUS L.): PRELIMINARY DATA FOR THE
ROLE OF HUNTING PRESSURE IN NP VITOSHA, BULGARIA
ELITSA POPOVA1*, NIKOLA DOYKIN1,2, VALENTIN ZLATANOV3,
1 – Department of Zoology and anthropology, Faculty of Biology, Soa University “St.
Kliment Ohridski”, Soa, Bulgaria
2 – Nature Park Vitosha, Soa, Bulgaria
3 – Advanced Wildlife Technologies and Management, Soa, Bulgaria
* Corresponding author: firstname.lastname@example.org
Keywords: vigilance, behaviour, roe deer, hunting
Abstract: Vigilance is an aspect of animal behaviour, which is often underrepresented
in camera trap studies. In the current study, we provide preliminary camera trap data
analysis on the differences in vigilance behaviour in two areas of Vitosha Mountain,
Bulgaria (with and without hunting pressure). Our results suggest that in locations where
hunting is permitted through the year, roe deer tend to be more vigilant (explained by the
heightened perceived risk) but some of them are more sedentary, spending relatively longer
periods of time in front of the camera trap. This could be attributed to the supplementary
feeding in the hunting area, which results in higher densities of ungulates (thus increased
competition and consequently smaller home ranges).
Camera traps have been used extensively to study biodiversity, species
richness, distributions and habitat use. In recent years more and more studies
were focused on animal behaviour issues, such as reproductive behaviour, feeding
behaviour, intraspecies and interspecies interactions (competition, predation,
etc.) and the effect of human-induced disturbance on all of these processes.
The vigilance behaviour exhibited by many species that leave the safety of
their shelters to forage is relatively underrepresented in these studies. Vigilance
is a type of behaviour associated with heightened perceived risk either by
competitors, predators or humans. It is often costly during foraging as it decreases
the time available to locate and consume food resources. Therefore, there is a
trade-off between the two, which could be inuenced by a number of factors,
such as food availability, predator densities, disturbance or hunting pressure,
habitat visibility etc.
Most of the existing studies regarding vigilance behaviour focus on ungulates
and are working on a single area with or without hunting/predation pressure
(Altendorf et al., 2001, Le Saout, 2015) or during or outside the hunting season
(Benhaiem et al, 2008). To our knowledge, our study is the rst to study the
differences in vigilance, relative to hunting pressure by comparing camera trap
data from two sites sharing similar habitat characteristics, where one is in a
hunting reserve (hunting is allowed through the year) and in the other hunting is
allowed only during open season.
MATERIALS AND METHODS
The study sites are located in Nature Park Vitosha, Bulgaria (N 42° 33’ 44”, E
23° 17’ 9”), on the southern slopes of the mountain. The study sites were labelled
Zone 2 and Zone 6 for consistency with previous work. Zone 2 is in the area
above Bosnek village, in the premises of the Vitoshko-Studena Hunting Reserve,
whereas Zone 6 is located above Zhelezhnitsa village. Hunting is permitted
throughout the year (and supplementary food is provided – e.g. corn) within the
area of the Hunting Reserve, whereas in the other study area (serving as a control),
hunting is restricted to the open season (October – February). Both study areas
are inhabited by wolves (Canis lupus) and their effect on the roe deer’s behaviour
is presumed to be similar in the two zones.
20 camera traps (Ltl Acorn 5210) were deployed in the two study areas (10 in
each zone) between May and September 2015 (Fig. 1). The camera traps were set
up on animal trails in forest habitats, according to a predetermined grid (Kilshaw
and Macdonald, 2011). They were programmed to take 3 photos and a 10-sec
video when activated by a passing animal, allowing the analysis of behaviour.
The camera traps were checked regularly to replace batteries and memory cards.
A standard form was lled for each camera trap location, including information
on the habitat characteristics. During the day, visibility was estimated (following
the method used by Le Saout, 2015) by using a 1m pole with 10 alternating
white and red 10 cm stripes, which was placed directly in front of the camera
trap. Visibility was assessed as the number of stripes visible from a distance of
10 m in the four cardinal directions. A visibility index was then estimated as the
proportion of visible stripes relative to the total number of stripes (ranging from
0 to 1, where 0 is a dense forest with low visibility and 1 is an open forest with
high visibility). For the analysis of the behaviour during different parts of the
day, 3 categories were used: day – the time between 30 min after sunrise and 30
min before sunset; twilight – the time within 30 min before and after sunrise and
sunset; night – the time between 30 min after sunset and 30 min before sunrise.
The exact times of sunrise and sunset were taken from the Astronomical calendar
of the Bulgarian Air Force (Bulgarian Air force – Meteorological Center, 2015).
Figure 1. Map of the camera trap locations in Zone 2 and Zone 6
Behavioural data and Statistical Analysis
The resulting photos were imported and analysed through CameraBase 1.6.
(Tobler, 2013) translated into Bulgarian and complemented to adapt the needs
of the study (Zlatanova 2014, unpublished). A total of 652 independent roe deer
registrations were recorded in 2124 camera trap nights. Relative abundance index
(RAI) was calculated for the two zones as the number of roe deer registrations per
100 camera trap days (ctd). For each registration, the following parameters were
estimated: total time in front of the camera (sec), time spent displaying vigilant
behaviour (sec), time spent displaying non-vigilant behaviour (sec) and the ratios
between them. Vigilant behaviour is described as the posture of the animal where
its head is above shoulder level and it’s scanning the surroundings (Appendix
Fig. A1, a). Non-vigilant behaviour is any other behaviour – including grooming,
browsing, feeding etc. (Appendix Fig. A1, b). Behaviour was analysed only when
the head of the animal was in the frame. Photos and videos displaying roe deer,
but not suitable for behavioural analysis were included in “time spent in front of
the camera”, but excluded from all other calculations. Roe deer behaviour was
successfully identied in 88,51% of the registrations, whereas the other 11,49%
were labelled as “unknown behaviour”.
Statistical analyses were performed in R v. 3.1.0 (R Core Team, 2015).
Figure A1 Camera trap photos of a male roe deer displaying
a) vigilant and b) non-vigilant behaviour
RESULTS AND DISCUSSION
A summary of the resulting camera trap photos and the behavioural data
derived from them is presented in Table 1. Due to malfunctions of part of the
camera traps the total operational time (camera trap days) is different between the
two zones. The RAI shows a considerable difference in the abundance of the roe
deer. In Zone 2 (within the Hunting reserve) the index is much higher, indicating
a more abundant population, which is expected considering the supplementary
food provided to the animals there.
Table 1. Summary of the camera trap and behavioural data
Zone 2 Zone 6
Registrations of roe deer 478 174
Camera trap days 1158 966
RAI (registrations/ 100 ctd) 41.28 18.01
Number of registrations displaying
vigilant behaviour 207 75
Percentage of registrations displaying
vigilant behaviour 43,31% 43,10%
The number of registrations in the camera trap locations is mapped and
presented in Fig. 2.
Figure 2. Roe deer registrations in the two zones
The total time spent in front of the camera (Fig. 3a) appears to be shorter in
Zone 2 than in Zone 6 when comparing the median values. There is, however,
an interesting distinction to be made – the presence of outliers with high
values of time spent in front of the camera in Zone 2, one even reaching more
than 2 minutes. It seems unexpected at rst to observe individuals spending
comparatively such a long time in one place, especially when faced with hunting
pressure and disturbance. In our case, this could be attributed to the difference
in the abundance of roe deer (and other ungulates, notably the red deer Cervus
elaphus, which is virtually absent from Zone 6) between the two zones. The high
roe deer density and the added presence of red deer in Zone 2 lead to increased
competition for space and food. That in turn limits the territory that is available
for foraging to a single individual and causes it to spend more time in the same
location utilizing the accessible resources at hand to the maximum.
The total percentage of registrations displaying vigilant behaviour in the two
zones are very similar, but the differences are visible in the analysis of the duration
and proportion of vigilant behaviour in each observation (Fig. 3). The box plots
for the duration of vigilant events (Fig 3b) show little difference between the
zones in terms of the median and the spread of the distributions. However, a larger
number of outliers are present in Zone 2, some holding values 2-3 times bigger
than those in Zone 6. This could be explained again with the higher densities
(resulting in smaller home ranges and the need to avoid competitors) in Zone 2,
and the data points to increased vigilance in the individuals that spend more time
in front of the camera.
The analysis of the proportion of time spent vigilant in each registration (Fig.
3c) shows a noticeable difference in the two zones. Vigilance levels are higher
in the zone with hunting pressure with a median of 0,67 and much lower in Zone
6 (median = 0,50) which emphasizes the role of hunting on roe deer behaviour.
This is in agreement with the result of Sönnichsen et al. (2013) and Benhaiem et
al (2008) that report heightened vigilance during the hunting season.
Figure 3. Effect of hunting pressure on roe deer behaviour. Total time spent in front of
the camera (a), duration (b) and proportion (c) of time spent vigilant in Zone 2 (in the
Hunting enterprise, hunting pressure through the year) and Zone 6 (control, without
hunting pressure outside of the open season)
When considering the different times of day, further patterns emerge. The
number of registrations displaying vigilance during the day, twilight and night
differs signicantly between the two zones (χ2 = 7,215; d.f. = 2; p < 0,05). The
proportion of the time spent vigilant (Fig.4) is higher and more variable during the
day and night in Zone 2, whereas higher levels of vigilance are observed in Zone
6 during twilight. The effect of hunting is reected in higher vigilance during the
day. The increased vigilance during the night in Zone 2 could be explained by
the concentrations of ungulates in the area (due to supplementary feeding) which
attract carnivores. In the conditions of high hunting pressure in this area during
the day, the wolves are limited in their activity patterns and need to forage during
the night. Under normal conditions (in the control Zone 6) the wolves are active
predominantly in twilight, which is reected in the higher vigilance levels of the
roe deer there.
Figure 4. Proportion of time spent vigilant at different times of day in:
a) Zone 2 – with hunting pressure and b) Zone 6 – without hunting pressure.
The roe deer in Zone 2 are more vigilant during the day and twilight than
during the night, which supports the conclusion of Eccard et al. (2015) in their
similar results in Germany. The authors suggest that this is a long-term adaptation
to daytime hunting. These results are also in agreement with those of Sönnichsen
et al. (2013) from the Białowieza Primeval Forest in Eastern Poland.
With regards to the visibility (Fig.5), in the hunting zone locations with
denser forests tend to have roe deer registrations with higher levels of vigilance,
whereas in the non-hunting zone vigilance levels are relatively stable in the
different visibility classes. This is in agreement with the ndings of Benhaiem et
al. (2008) that during the open season roe deer are less vigilant when they were
close to woodland, but this is not the case outside the open season.
Figure 5. Proportion of time spent vigilant at different times of day in:
a) Zone 2 – with hunting pressure and b) Zone 6 – without hunting pressure.
In locations where the forest is relatively dense (forest visibility class 0.20
– 0.40) roe deer are more vigilant in the hunting zone. Such habitats provide
concealment to hunters and roe deer need to be more alert in order to spot a
potential threat early enough. In more open forests (class 0.60 – 0.80) there is a
reverse relationship – with higher vigilance levels in the non-hunting zone where
the only threat can be attributed to predators. In the open forest with very high
visibility (class 0.80 – 1.00) the vigilance levels are similar.
In Zone 2 the percentage of registrations displaying vigilant behaviour are
lower in the open forests than in the dense forests which points at visibility as one
of the factors that determine roe deer behaviour. In conditions of high visibility,
the animal is capable of detecting danger much easier and thus does not need to
be alert as long. This is especially true in Zone 2, where the main threat are the
hunters, who can easily be heard and seen in an open forest. These results are in
agreement with the conclusions of Altendrof et al. (2001) for the behaviour of the
mule deer in Idaho, USA and those of Le Saout (2015) for the Sitka black- tailed
deer in Canada. Kuijper et al. (2014), however, suggest that olfactory cues (in
their case wolf scat) are more important than visual ones when assessing risk in
Additional environmental and habitat variables could be studied in order to
further understand the dynamics of roe deer behaviour. The seasonal shifts in
territoriality, hunting pressure, foliage (altering visibility) and food availability
should all be taken into account when attempting to explain the differences in roe
deer vigilance. Roe deer density, presence of other ungulates acting as competitors
(red deer), as well as carnivores, could also play an important role. Furthermore,
it is interesting to test the effects of characteristics such as sex, age and group size
on vigilance behaviour (Lashley et al. (2014) provide an insight on white-tailed
deer vigilance in these aspects).
The results of the current study suggest that hunting pressures does cause
changes in the behaviour of roe deer that is reected in heightened vigilance not
only during the day (when hunters are active), but also at night. Forest visibility
plays a role in determining vigilance levels, mainly in the hunting zone. Due to
the high density of the roe deer population in the hunting zone (caused by the
abundant supplementary food provided by the Hunting reserve) some individuals
are limited in space by their competitors. They tend to spend more time in the
same location and show high levels of vigilance.
Acknowledgements: This work was supported by project „Ecological and behavioural
aspects of representative species of reptiles and mammals in model Natura 2000 zones”
(Contract № 167/17.04.2015), funded by the Fund for Scientic Research of Soa
University, and by the Directorate of NP Vitosha.
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