Box C 20
Large carnivores and forest habitats:
what can we learn from the Naliboki Forest?
M. Hetzer
Bayerische Staatsforsten AöR
The Naliboki Forest is a vast swamp forest along the River Biarezina located in the hemiboreal zone of central-western Belarus. This transitional zone between boreal and temperate climates supports high levels of biodiversity with a great range of European species of flora and fauna, including the large carnivores, such as grey wolf (Canis lupus), lynx (Lynx lynx) and bear (Ursus arctos). Approxi- mately half of Naliboki Forest is protected as a landscape reserve with legal restrictions on hunt- ing. However, hunting is allowed in large areas sur- rounding the reserve and wolves are persecuted each winter. In such vast forested areas, the large
carnivores often come into contact with humans and forestry. Of these species, especially wolves have settled quite successfully into the European cultural landscape. They use and habituate to the structures provided by forestry very effectively, but they also need an (irregular) mosaic of natural suc- cession within the managed area to find sufficient food and places to retreat for denning and raising their pups. Thus, it is important to consider these aspects of the animal behaviour and ecology when managing forests.
There has been extensive research carried out in Naliboki Forest for many years on how large car- nivores use their forest habitat, and how they are affected by different forestry measures. In the past, different methods of investigation (from telemetry studies of lynxes to autopsies of wolves) have been used to study wolves and lynxes and their interac- tions within the ecosystem. Today, mainly non-inva- sive methods (e.g. habitat inspections, snow-track- ing, reading of activity signs, and camera traps) are used to examine the ecology and behaviour of these animals. The findings from these studies have
Fig. 1. (a) canal system created by beaver dams; (b) typical birch forest in autumn; (c) spruce forest with tree falls; (d) typical swamp forest (Photos: Vadim Sidorovich, Maximilian Hetzer).
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paved the way for unprecedented investigation of behaviour and ecology of lynxes and wolves. In this box we share some insights for forest enterprises and forest owners in other parts of Europe where wolves and lynxes are reclaiming their territories after decades of absence, and where practical knowledge of their management is limited.
The Naliboki Forest is made up of mostly flat lowland terrain interspersed with larger or smaller complexes of sand dunes. In total, Naliboki Forest and its surroundings cover an area of 2750 km², of which approximately 1900 km² are densely for- ested. Coniferous and small-leaved broadleaved trees predominate: Scots pine (Pinus sylvestris) stands can be found on 40 % of the area and black alder (Alnus glutinosa) swamp forests are found on 27 %. Only 7 % of the forests are older than 80–100 years, and only 1 % are broadleaved old-growth stands with an age between 200–400 years. The river density is about 0.9 km/km² and there are many canals (about 2–9 km/km²). The typical forest management practices are clearcuts, creating a mosaic of clearfelled areas of between 3 % to 7 % over the whole terrain (see figs 1). Usually there are a lot of logging remains or rotten log piles on the cutting areas. Additionally, there are often a lot of fallen trees around such clearcuts. Tree fall is also quite a widespread phenomenon in the swamp areas. Such tree falls can occupy an area of several hectares. Usually these groups of fallen or inclined trees stay untouched by forestry measures and are naturally overgrown by the regenerating forest.
The importance of the forest habitat: Denning behaviour of wolves
Wolves are able to adapt and live near human set- tlements or managed forest just as they are able to inhabit forests that they are not used to. They do not have particularly high demands of the forest, or other environments that they live in. Therefore, the structure of the forest is not a decisive factor determining the distribution of wolves in a specific area. A more important factor is the supply of prey and territorial space for the settlement of wolf packs and safe shelter places for denning and rais- ing pups. Counting wolf pups is a very effective method for the study of the breeding behaviour of grey wolves. Over the years, more than 75 dens with healthy pups have been found. The denning behaviour of the wolves is strongly affected by the environment. This means that wolves often change
locations and adjust their behaviour according to the environment; there are no particular ‘rules’ or
‘normal features’ of favoured wolf habitat.
The Naliboki wolves locate their den close to the main roads in the area in which they breed. The parent wolves need to know what people do in the area by monitoring human activities from the den or nearby. Furthermore, the roads provide conven- ient routes for parent wolves to access hunting areas and bring the food back to the den. Marking of borders of the denning area on the road also seems to be important for the parent wolves. In addition, roads and other paved paths offer con- venient and quick routes back to the den. Never- theless, that does not mean that wolves like breed- ing close to busy roads. The parent wolves were observed to check on the roads up to 60 times a day. Another important consideration is that wolves from outside the area use roads and forestry tracks to enter the territory and denning areas.
Suitable wolf denning areas include: areas with a large amount of tree fall; thickets with many uprooted trees (especially spruce); abandoned thickets in logging areas with a lot of tree stumps and logs; abandoned peat cuttings; and sand dunes with young pines and small openings. Tree falls and logging areas are used by wolves after giving birth.
We found that from July to September, about 30 % of the wolf family home range habitats (n=135) were in areas with fallen trees in old spruce forests (fig. 2).
For denning of wolves, it is important that the dens are well sheltered from attacks by other pred- ators like lynx or brown bears. Additionally, large ungulates like red deer (Cervus elaphus), elk (Alces alces) and European bison (Bison bonasus) can be a threat to wolf cubs: especially red deer stags have been repeatedly observed attacking and killing wolf cubs (fig. 3). Other important aspects in wolf denning include: a rather low occurrence of mos- quitoes, good views of the surroundings, and good shelter for the pups and parents from the weather.
During the denning period it is important to distinguish ‘breeders’ from ‘non-breeders’ (i.e. the yearling wolves). The pattern of track trails left by
‘non-breeders’ is likely to be more random or absent. Furthermore, the ‘non-breeders’ carry and leave useless things like human rubbish (rubber boots, plastic bottles) and they collect and gnaw on ungulate bones and antlers.
Lynx – a deep interaction with wild forests and trees
Tree falls, and especially inclined trees leaning against other trees and thickets, are very important for lynx ecology and behaviour. In mid-autumn, male lynxes start searching for, and guarding, suit- able habitats for mating and rearing young in their
home range. These habitats should have a low den- sity of large ungulates and provide shelter against possible wolf attacks. Suitable den sites include spruce thickets and rotten trees or tree falls with several layers (figs 4). In the home range of a mat- ing lynx pair there must be a few (3–5) of these sheltered sites. During mating, the mother leaves Fig. 2. (a) typical denning habitat of wolves; (b) young wolves in late summer at a treefall; (c) wolf pups under an uprooted tree; (d) wolf on a forestry road (Photos: Vadim Sidorovich, Maximilian Hetzer).
Fig. 3. (a) red deer stag checking on wolf den with pups; (b) wolf cubs killed by red deer (Photos: Maximilian Hetzer).
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the new kittens in such sites to keep them safe.
These sheltered spots are guarded by male lynxes with frequent visits and intensive scent-marking in a large area (several kilometres in diameter). Within the home range of an adult male lynx there may be several ‘house areas’ (distinct patches of the home range of a lynx containing several such mating spots and dens). These house areas can be relatively poor in prey (in Naliboki, 14 out of 24 house areas had relatively low densities of potential prey), as the male chooses the winter house area mainly for the quality of shelter, rather than the availability of prey. At the mating spots, male lynxes choose ele- vated positions and often climb tall trees to call for mates. During the mating season, adult females seem to actively search for adult males with suita- ble house areas and mating spots.
In mountainous or rocky regions, it is known that female lynxes usually create lairs in cavities between rocks. In contrast, very little is known about lynx denning in forests in non-rocky areas.
Our research shows that there is a relation between
the presence/absence of badgers (Meles meles) and den selection by lynx in Belarus. In some areas, lynx give birth, and raise their kittens in the early post-natal stage in former wolf burrows, aban- doned badger setts, or beaver burrow networks. In other areas, where the badger population density is high and most burrows are occupied by badgers, lynx dens are more often situated in tree fall areas.
The kittens are hidden under the compressed remains from logging or in the spaces where spruce trees fall on other large spruces so that a sheltered platform is created. A tree fall consisting of several large fallen spruce trees, with one crown laying down on the top of the other creates a favourable shelter underneath the compressed green spruce branches where mother lynxes can safely leave their kittens. Under this thick layer of spruce branches, kittens are well protected from rain and mosquitoes. The compressed remains left after log- ging can provide a similar kind of shelter.
From May until June 2018, we discovered three lynx dens in Naliboki Forest during 40 days of obser- Fig. 4. (a) Mating lynx pair in a spruce thicket; b) young lynxes in their homesite; (c) lynx kittens under a root plate of an uprooted tree; (d) pregnant female lynx checking a former wolf burrow as a potential denning site (Photos: Vadim Sidorovich, Maximilian Hetzer).
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vation; two were found in tree falls and one was found under an abandoned/rotten log pile in a boggy pine stand with dense Ledum palustre (syn.
Rhododendron tomentosum subsp. tomentosum) shrub cover. Later, the kittens were hidden by their mothers under piles of logs that were abandoned by loggers on the clearcut (fig. 5). We found remains of three different roe deer (Capreolus
capreolus) that had been eaten by the lynxes on the log piles. So, on the one hand, the log piles pro- vided a sheltered place for the kittens while the mother is hunting, and on the other hand a safe place to eat the prey that was brought by the mother.
Out of 11 lynx dens, in two cases lynx kittens were discovered on raised platforms where one spruce tree had fallen against another large spruce.
The kittens were found at a height of 5–7 m on platforms formed by the spruce branches. Three other types of dens connected with trees were dis- tinguished: a closed cavity of a root plate of an uprooted tree; a lair under the green crowns of recently fallen spruces; and the remains of a large tree fall overgrown with dense vegetation.
The role of trees in hunting by lynx is very important. In the warm season, when there are plenty of mosquitoes in Belarus, lynxes prefer to wait and watch for their prey from trees (at heights from 3 to 10 m above ground, where the mosqui- toes are less numerous). Amongst 54 known lynx ambush sites on trees, most (78 %) had similar char- acteristics: a tree trunk (usually spruce with a dense Fig. 5. Lynx family playground and sheltered place on an
abandoned log pile (Photo: Maximilian Hetzer).
Fig. 6. Lynxes regularly use tree trunks for ambush hunting (Photo: Maximilian Hetzer).
crown) that was inclined against another tree. The ambush sites in trees were mainly situated along prey pathways (91 %). The lynxes mainly used these ambush sites during the snowless periods, they could wait and watch in these sites for long periods (fig. 6). The longest time we observed a lynx stay- ing at one point was 32 hours. At a rough estimate, during the warm season lynxes may spend about 90 % of the hunting time waiting and watching for prey from tree ambush sites; during this period lynxes almost completely stop more active methods of hunting (patrolling and stalking), when mosqui- toes become numerous.
In Belarus, lynxes have quite often been observed in concrete road drains. In the warm sea- son, they mainly use road drains without running water. In winter, when the temperature is below 0 °C, almost all drains that are large enough are used by lynxes.
We investigated this use of road drains and identi- fied four different uses (fig. 7):
1 Road drains are often something that visually stand out from the habitat structure of the forest
road. Such spots are often marked by carnivores, including lynxes. Snow-tracking data suggest that about 90 % of visits to road drains by lynxes (more than 200 cases were observed) were, at least, partly for territorial marking.
2 In approximately 60 % of the cases, lynxes were observed walking, hidden in the road–forest eco- tone, then they use the road drains to surprise possible prey. On one occasion a lynx was observed to have killed a roe deer close to a drain entrance. On another occasion a raccoon dog (Nyctereutes procyonoides) was killed by a lynx using such an approach.
3 During rainy weather or wet snow, lynxes have been observed using the drains to dry out and shelter from the weather (17 observations).
4 Sometimes the lynxes even rest inside the drains (5 observations at least). On two of the five occa- sions, the lynx may have been waiting and watch- ing for prey at the same time; on these occasions the lynx stayed for a long time in the drain (7 to 11 hours). While inside the road drain, the lynxes use the sand or the dry remains of vegetation to rest on.
Fig. 7. Lynx entering a concrete road drain (Photo: Maximilian Hetzer).
Marking behaviour and competition between large carnivores
Wolves and lynxes are territorial carnivores that typically use visual- and scent-marking to delimit their territory. Crossings on forestry roads, root plates of fallen trees, forestry poles, or essentially anything that protrudes from its surroundings are often marked. Forestry roads are popular routes for marking by wolves and lynxes. The analysis of our snow-tracking data shows that wolves use such
roads in about 60–80 % of marking events. The intensity of marking varies over the course of the year. For instance, during the mating season wolves mark up to 60 times within 24 hours. In compari- son, during denning wolves only use 2–3 marking points, mostly along forestry roads. When marking their territory, male lynx can walk approximately 15–40 km and place 5–20 territorial marks per kilo- metre. The intensity of scent-marking remains more-or-less constant over the year; however, there
Fig. 8. (a) typical scratch marks on a road by wolves; (b) lynx hair after marking on a root plate; (c) lynxes marking on a forestry pole; (d) wolf aggressively gnawing on the same pole; (e) female wolf in front of her den with pups inside;
(f) lynx leaving the same burrow den after having killed the litter (Photos: Vadim Sidorovich, Maximilian Hetzer).
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is a two-fold increase in marking before the mating season in mid-February.
However, marking is not only done to delimit the territory. More specifically, marking behaviour is also an indicator of wolves and lynxes sharing the same habitat. For example, wolves start erasing lynx marking points. In more than 1000 km of lynx snow-tracking, we found cases in which wolves start to ‘over mark’ lynx marking points but never vice versa. Another example of erasing lynx mark- ing points was documented by a camera trap: a male wolf started to gnaw a forestry pole (fig. 8d) which had been marked by different lynxes in numerous ways (urinating, scratching, and rub- bing).
We found that lynxes can have a deep impact on reproduction, pack composition, and immigra- tion/emigration of wolves: lynxes were repeatedly documented to target wolf dens and kill the wolf pups. This behaviour is so effective that wolf repro- duction can decrease to zero over several years, although the adult wolf population is still relatively high. As a consequence, in Naliboki wolf packs lack the typical family structure and consist largely of only adult animals. However, wolves were also observed to be able to react to such situations by more carefully selecting protected dens, changing denning habitats, but also by ‘multiple breeding’
(while it is normally only the alpha pair in a pack that breed, other wolves in the Naliboki group have also produced offspring). The pack has also been observed to use ‘pup sitters’ (i.e. wolves that are not the mother or father) to guard the pups.
Conclusions
Even in vast forest landscapes, like in Belarus, large carnivores are always in contact with humans; this is especially true for forestry work. Wolves have set- tled quite successfully into the European cultural landscape. For both lynxes and wolves, it is crucial to have sufficient food and places to retreat for denning and to raise their young. To a certain extent, these species can modify their behaviour, and adapt to the available habitats very effectively.
However, they do require a range of sites for differ- ent purposes (giving birth, rearing young, shelter from the weather, hunting), and it is important to manage the forests irregularly so that the full range of such sites is available. Foresters have to learn to forget the ‘Prussian cleanliness’ and delight in the wilderness of nature.
References
Sidorovich, V.E., 2009: Guide to Mammal and Bird Activity Signs: Skills Gained in Belarus. Zimaletto, Minsk, Bela- rus.
Sidorovich, V.E., 2011: Analysis of Vertebrate Preda- tor-Prey Community. Tesey, Minsk, Belarus.734 p.
Sidorovich, V.E., 2016: Naliboki Forest: Land, Wildlife and Human. Volume 1 Land and Plant Communities. Chatyry Chverci, Minsk, Belarus. 410 p.
Sidorovich, V.E.; Gouwy, J.; Rotenko, I., 2018: Unknown Eurasian Lynx lynx: New Findings on the Species Ecology and Behaviour. Chatyry Chverci, Minsk, Belarus. 273 p.
Sidorovich, V.E.; Rotenko, I., 2019: Reproduction Biology in Grey Wolves Canis lupus in Belarus: Common Beliefs versus Reality. Chatyry Chverci, Minsk, Belarus.
