Eurasian lynxes in Belarus climb in trees to emit territorial and mating calls

During the winter of 2017-2018 in Naliboki Forest we have found that Eurasian lynxes climbed rather high pine trees (Pinus sylvestris) to emit mating calls during the mating season (Sidorovich, Gouwy & Rotenko 2018). In total, during February and March 2018, we registered four pine trees, on which adult male lynxes climbed for about 17-26  meters high. The density of the  local lynx population was about 4-5 individuals per 100 km2 i.e. about 80 on an area of almost 2000 km2.  We have evaluated that phenomenon of calling by lynxes from a tall tree top as a mating call, also taking into account that it was registered in the lynx mating season in Belarus (mid-February-early April).

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However, between 1998 and 2012, when  the species population density was lower than 3 individuals per 100 km2 (usually between 1 and 2 individuals per 100 km2),  we never found such tall trees climbed by lynxes after more than 2000 km of snowtracking lynxes. This strange situation lead us to think that these trees might also be used to emit territorial calls by lynxes, when the species population density is rather high. On the other hand, when the lynx population is low and individuals are not so tightly packed, calling for mates might not be efficient.

Then, in July 2018 we found a tall pine with fresh climbing marks in Naliboki Forest, presumably it was climbed by an adult female lynx (mother with two kittens), because the tree was in the core area, where this mother lynx with two kittens stayed most of the time. The area contained badger setts and kittens used a lot badger burrows (mostly outlayers) to shelter from mosquitos.

In November (again in Naliboki Forest) we registered at least two, maybe even three, recent climbing’s of tall pine trees by lynxes in different lynx territories, and when we discovered that a male lynx climbed a tall aspen tree in mid-december, we started to think that lynxes use these trees to emit territorial calls when the lynx population has a high density.

Aspen tree climbed and used as a territorial call tree by lynx in the end of december 2018.

With so many lynxes in Naliboki Forest, it was already too hard to do a precise census of lynxes. Camera trap registrations (60-70 camera traps were applied), track survey (twice per month) and snowtracking (about 260 km) suggested that during the winter 2018-2019 there were more than 80 lynxes in Naliboki Forest, perhaps, about on average 6 individuals per 100 km2. The local range of the species density was between 2 individuals per 100 km2 in sand dune massifs and 14 individuals per 100 km2 around the Biarezina river (medium-sized river valley with broadleaved deciduous forest).

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These climbing marks were made by lynx in February 2018,  in March 2019 they were not light red anymore, but already dark brown.

In January-March 2019 in Naliboki Forest we registered 42 new trees, which were climbed by lynxes (see the tree distribution maps). In total in this period we registered 60 trees that were recently climbed by lynxes, 41 trees were climbed during late February and March (mating season in lynxes), which is evidently more often (68%). Fresh climbing’s of a tree can be registered  by looking at fresh claw marks on the bark (still light red in the case of pine trees), recently broken dead branches on a height and a lot of small bark remains on the snow surface around the tree.  Recent climbing’s may also be registered by camera trapping; in three cases we found that lynxes stepped on camera traps on a height of 2-5 meters and the camera traps took pictures of fragments of lynx fur as they were climbing  the trees.

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Trees climbed by lynxes in  Naliboki Forest in 2019; lynx claw marks on the tree bark and pieces of lynx bodies that were photographed by cameras fixed on the tree stems.

Still we do not have a good photo or video of Eurasian lynxes climbing trees, because, in the majority of cases, a lynx runs towards the stem and jumps on the tree that it decided to climb. In this case a lynx can jump 3-4 meters high on the stem. As lynxes climb down, they mainly jump down from a height of 4-6 meters. So, on camera traps you see photos of the stem, but already  without the lynx, because in the majority of cases, the camera-traps were not fast enough to capture a climbing lynx. In February-March we got three such failures. However, we still hope to take photos of a lynx climbing a tree, because claw marks on the tree bark suggests that sometimes before climbing, a lynx smells the tree stem and begins climbing without jumping. When a lynx is climbing down, it may sometimes also reach the ground level without jumping.  To register that, we put camera traps on the neighboring tree on a distance of 4-6 meters. The camera trap is placed in vertical position and it has  in the frame 4-6 meters of the stem of the tree, on which we guess a lynx will climb. Other possible ways of taking such a photo are rather time and labour-consuming and need more and quite large equipment (e.g. ladder), for the moment this is too impractical for us and hard to combine with our way of working. Perhaps, we will undertake other approaches to take photos of lynx climbing trees, if we finally failed with the method we use for the moment.

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So why we did not find out about this behaviour before, having so much lynx snowtracking experience? We assume that lynxes called from tall trees before as well, but not so often. The key point is: what is much lynx snowtracking? In 2018-2019 in Naliboki Forest, when we quite often registered lynxes climbing trees, we did about 260 km of snowtracking and during just this kind of study we have registered merely one climbing of a tree top. So before, by doing 2000 km of snowtracking, we could potentially reveal about 8 such climbing’s of trees by lynxes. But in the conditions of a lower population density of  lynxes, in which the studies were carried out,  undoubtedly lynxes emitted  territorial calls and did other markings of their territories markedly less frequently (as all other vertebrate animals). Additionally, the main aim of the lynx snowtracking we did before was to reveal the home range of lynxes by multi-tracking the same individual. We were in a hurry to do as many as possible km of snowtracking and did not pay much attention on details. So, from the above we see that that 2000 km of snowtracking, when the lynx density was lower, is not a good enough argument that lynxes did not climb trees during that time. Possibly they did, but less frequently than nowadays.

So, currently we state that lynxes emit territorial calls almost year-round,  particularly when the species population density is high (4 and more individuals per 100 km2). Perhaps, in non-mountainous forested areas lynxes do so from an elevated position, mainly by climbing a tall tree. Just before and during mating season, such a call of adult males plays a double role, and indicates both occupation of the territory for other possible adult males in the surrounding area, and attracts females in heat.

Which trees do lynxes prefer to climb?

While inspecting  a number of trees, the answer will be more or less biased, because mainly pine trees are relatively easy  to find during such an inspection, as the soft pine bark leaves visible lynx claw marks. However, while snowtracking and just checking trees with snow cover, we also found that lynxes climbed  aspen, spruce and oak, and in these cases there were almost no claw marks on the stems (with the exception of three oaks). So, only pines that were climbed by lynxes were more or less easily found and they prevail among the 51 lynx trees that were registered by us in Naliboki Forest in 2018-2019: two aspen, six oaks, one spruce and 42 pines. 22 (43%) out of 51 lynx trees were situated on small hills (in the flat Naliboki Forest there are no high hills); 12 lynx trees (24%) were situated on recent clearcuts without any tree stand around.  Only 6 (15%) out of 39 lynx trees that were situated in a tree stand were slightly lower than the forest canopy level, whereas others (8 or 21%) were on the level of the forest canopy  or even higher than the forest canopy (15 or 64%). At the top of lynx trees there should be at least one suitable branch to sit and emit calls. In two cases such a suitable place was formed by raven and buzzard nests.

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Oaks that were climbed by lynxes for territorial calls. Only some marks on the moss and very few claw marks on the hard bark.

Lynxes chose trees either almost without branches below the sitting branch, or trees having a row of stable and solid branches. In the case of a stem without branches there should be thick and outstanding  bark segments of about on average 5 cm wide by 15 cm long, which can be grabbed by lynxes as they climb. Such a tree should have a rather broad stem.  In the case of climbing by grabbing thick bark segments of big trees, lynx leaves really few small claw marks.

Simulation of lynx climbing technique on large trees with wide stems and thick, outstanding bark segments, leaving only few claw marks

Alternatively, lynx may climb trees trees with relatively narrow stems of 30-40 cm  in diameter, no branches and no thick bark segments. In this case lynx  encircles the stem with its fore paws, while the claws of its hind paws are stuck in the bark. In this case there are usually markedly more lynx claw marks on the tree.

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Simulation of lynx climbing technique on  trees with  relatively narrow stems of 30-40 cm  in diameter, no branches and no thick bark segments.

If there are solid branches on the upper half of stem, a lynx, while climbing, uses them to jump from branch to branch.

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Not so tall pine trees, which were climbed by lynxes, while jumping from one branch to another (living or dead, broken but solid branches); using these branches lynxes can come down face down. 

Also, lynxes like to climb inclined trees. In this case they can just walk up along the inclined stem and reach the tree that supports the inclined tree.

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Interestingly to emphasize is that at the Biarezina valley, with  old deciduous broadleaved forest, the highest local number of lynxes (20 individuals in the winter 2018-2019) occurs on not a large area of about 140 km². In this area, we found 26 lynx trees (half of the lynx trees discovered or about 19 lynx trees per 100 km2 ), while in the rest of the about 660 km2 of model area in Naliboki Forest we found only 25 lynx trees (about 4 lynx trees per 100 km2).

Some information on lynx calling itself in Belarus

Vadim Sidorovich: ‘while working with carnivores  and other vertebrate  predators  during almost 35 years in the wild and sleeping in the wild perhaps about two years (approximately about 700 nights) in different seasons, I definitely heard lynx calling only for three times. That was mostly when the lynx population density was not high (mainly about 0.5-1, sometimes about 2 individuals per 100 km2), and I had no idea that they may call from a tree top. Two lynx callings were heard at night and one was registered during dusk, when it was almost dark.  I would say that the callings were rather long-lasting. In one case lynx was calling for about three hours; sometime there were 5-15 calls per a minute and sometimes there was a brake in calling for 3-10 minutes. In nights, when sound travels relatively faraway, the lynx calls I could hear were at a distance of about 2 km maximally. Nowadays, trying to remember and analyse my memories of those lynx calls, I realize that, at least, two of the lynx callings were emitted from a tree top, because the lynx positioning did not change for about one hour in one case and about three hours in another case. Interestingly to notice that in Belarus among the nature-related people (like hunters etc) everybody knows that wolves howl, but with the exception of one life-long hunting warden, nobody knows about calling by lynxes. ’

Generally, for the moment there are more pressing questions than complete knowledge when it comes to climbing of trees by Eurasian lynxes to emit territorial and mating calls. Possible questions are as follows. How often do lynxes call in non-mating and mating seasons? As to non-mating i.e. territorial calls, how are they seasonally or monthly distributed? Is lynx calling weather-related? How long do lynxes call? Other characteristics of the callings of the Eurasian are poorly known as well. Do only adult male lynxes emit territorial and mating calls or do adult females call too? How often do lynxes use the main and secondary calling trees? What is the real tree species proportion between the lynx trees? How much is calling by lynxes density-related?  What is the proportion of calling by lynxes from trees and ground surface in forested areas with a more or less flat relief? No doubt, there is a lot unknown in relation to the climbing techniques by Eurasian lynxes; it should differ from that of Canadian lynxes, which are markedly lighter.

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