Climbing trees by Eurasian lynxes to emit territorial and mating calls in Belarus: pressing questions and knowledge up-to-date

Another important role of trees in the life of lynxes is usage of elevated positions in tall trees to emit territorial and mating calls. During the winter of 2017-2018 in Naliboki Forest, the central-western part of Belarus we have found that lynxes climbed rather high Scotch pine trees (Sidorovich et al., 2018). In total, during February and March 2018, we registered four such trees, on which adult male lynxes climbed for about 17-26 meters high. The density of the local lynx population was very high about 4-5 inds per 100 square km i.e. about 80 lynxes per almost 2000 square km. 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 (mid-February-early April).

Then in Naliboki Forest in July 2018 we faced with several fresh climbing a tall pine presumably by adult female lynx (that was mother with two kittens), because the tree was in the core area, where this mother lynx with two kittens were staying most of the time.

Below you will see the photo-material we have got in February-March of 2018.

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Then in Naliboki Forest again in November we registered at least two may be even three recent climbing of tall pine trees by lynxes in different lynx territories. Then in the late December 2018 we found that an adult male lynx climbed a tall aspen tree, and after this observation we have started thinking about territorial calling by lynxes in the conditions of high population density.

In January-March 2019 in Naliboki Forest we registered 42 new trees, which were climbed by lynxes. In total in this period we registered 60 recent climbing of trees by lynxes; 41 of them were climbed during the period from the mid-February till early March i.e. in pre-mating time and mating season in lynxes. The facts of climbing tree by lynxes were mainly registered by fresh (still light red in the case of pine trees) claw marks on the bark, recent broken dead branches on a height, a lot of small bark remains on snow surface around the tree as well as in three cases by stepping on camera traps on the height of 2-5 meters and fragments of lynx fur taken by the cameras in these cases.

These lynx climbing marks were made by lynx in February of 2018, and now in March of 2019 they are not light red, but alredy dark brown.
These climbing marks were made by lynx in February of 2018, and now in March of 2019 they are not light red, but already dark brown.

In April 2019 during regular inspecting of 22 trees, which were climbed by lynxes before, we registered only one recent lynx climbing, while later in the period of May till the mid-July these trees were climbed 9 times, at least. Then in August there was no any recent climbing found.

Since the late autunm of 2019 till the spring 2021 we checked regularly from 72 to 104 such trees, on which lynxes climbed (hereafter lynx tree). There were revealed three seasonal periods with the increased climbing-calling activity of lynxes. First one is from the early November till early December (14% of climbing-calling fixes), which can be connected with establishing of winter home ranges by marking not only with scent, but with calling as well. From the mid-February till the early March is the second such a period (42% of climbing-calling fixes), which is pre-mating time and beginning of mating in lynxes. The period of May till the mid-July shows the third increased climbing-calling activity of lynxes (34% of climbing-calling fixes).

By investigating so many trees on which lynxes climbed, we seemingly can characterize how lynxes choose them. The main three details are plausibly as follows. First, it should be lynxes in the surrounding habitats, to which such a calling message of a particular lynx is sent. Second, such a tree should be higher than the neighbouring tree canopy. Alternatively, it may be a single tree on a hill within a clearcut or any other opening. Third, it should be not many weak dead branches on such a tree trunk. Otherwise, it will be hard for a lynx to climb such a tree, taking into account the species manner to do that.

In Naliboki Forest 62 out of 104 lynx trees (60%) stood within forest habitats. Among them 37 (i.e. out of 62) trees have the tops that was higher than the canopy level of adjacent forest. Almost all other 25 out of those 62 trees reached the adjacent forest canopy level, but they were not taller. Only some of them were slightly lower than the forest canopy level. Forty two lynx trees (40%) stood either in small openings that were surrounded by forest habitats or at their forested edges. Mainly those openings were clearcuts with an area less than 15 hectares. Seventy out of 104 investigated lynx trees (67%) stood on small hills (in Naliboki Forest there are no high hills, it is a flat terrain mainly). It was noticeable that among standing trees lynxes prefered to climb a slightly inclined trees (24 out of 104 investigated lynx trees, 23%).

Interestingly, that during the winter of 2018-2019 in Naliboki Forest around the large valley of the Biarezina river with  old deciduous broadleaved forest, there was the highest local number of lynxes: 20 inds on not a large area of about 140 km2. In this area, we found 26 lynx trees (a half of the lynx trees discovered during this winter or about 19 lynx trees per 100 square km). In the other inspected part of Naliboki Forest on the area about 660 square km there were found only 25 lynx trees that is about 4 lynx trees per 100 square km.

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Lynx climbed this aspen tree for a territorial call in the end of December of 2018. Photos by Siege Van Ballaert and Reinhardt Strubbe.

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The trees which were 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 trunk.

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In the case of trunk without branches there should be thick and outstanding  bark segments about on average 5 cm wide by 15 cm long, which can be grabbed by climbing lynxes. Such a tree should have a rather broad stem.  In the case of climbing by grabbing thick bark segments of broad trees, lynx leaves really few small claw marks.
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Lynxes usually do not climb on broad stem tree with relevant  branches, suitably located, but without thick outstanding bark segments like this one.
F59A3538WEbIf there are solid branches on the upper half of trunk, a lynx, while climbing, uses them to jump from branch to branch.

Lynxes may climb trees without branches having a relatively narrow trunk of 30-40 cm  in diameter and no thick bark segments. In this case lynx  encircles the trunk with its fore paws, while the claws of hind paws are stuck in the bark. In the case of such a climbing usually there are markedly more lynx claw marks on the tree.
P1020744WebTo register lynx climbing of a tree, 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 trunk of the tree, on which we guess a lynx will climb.

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Not a high pine trees, which were climbing by lynxes, while jumping from one branch to another one (alive one or only dry broken one, but solid enough); the same it jumped down using the branches.

Lynxes like to climb a tall tree by walking there along another tree that was inclined on that targeted  tree.

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Oaks that were climbed by lynxes for territorial calls. See the only marks on moss and something negligible  on solid bark.

Among the 104 investigated lynx trees there were 30 oaks, 4 maples, 3 limes, 3 aspens, 2 black alders and 62 pines. So, in Belarus lynxes prefer to climb oaks or pines. Concerning oaks, almost all big oaks have got thick and outstanding  bark segments that are suitable for lynx climbing. Also, big oaks have nearly no weak dead branches on a broad stem. In the case of pine trunk without weak dead branches there should be thick and outstanding  bark segments about on average 5 cm wide by 15 cm long, with which climbing lynxes can grab. Such a pine tree should have a rather broad stem.  In the case of climbing by grabbing thick bark segments of broad trees, lynx leaves really few small claw marks.
Interestingly, that 4 out of 104 investigated lynx trees had big nests of ravens, common buzzards and spotted eagles, and lynxes used the nests as a platform for calling and a couch for resting.

From the below photos you may see the climbing technique which lynxes apply to climb a wide tree. A lynx embraces a wide trunk by their fore paws and lift hind legs to the belly level. At this moment a lynx hitches by hind paw claws and, by pushing up with hind legs, it can grab about one meter higher with the claws of the fore paws. Also, it is worthwhile to notice that a lynx may fix itself even on bark of deciduous tree in all direction positions.

Lynxes usually do not climb broad stem tree even with relevant  branches, suitably located, but without thick outstanding bark segments. If there are solid branches on the upper half of trunk, a lynx, while climbing, uses them to jump from branch to branch.Lynxes may climb trees without branches having a relatively narrow trunk of 30-40 cm  in diameter and no thick bark segments. In this case lynx  encircles the trunk with its fore paws, while the claws of hind paws are stuck in the bark. In the case of such a climbing usually there are markedly more lynx claw marks on the tree.

Also, it should be given  some information available on a lynx calling itself. We will describe a long-lasting callings only, when we definitely could recognize that we were hearing a lynx calling, but not a roe deer shouting. We have many video with lynx calling and we hear that as ‘weow’. Indeed, the calls of a lynx and roe deer are quite similar from a distance of several hundreads meters in forest habitats.

A total, we heard eight relatively long-lasting lynx callings: two at night, three in twilights and three in daytime.  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. At night, when sound travels relatively faraway, the lynx calls could be heard at a distance of about 2 km maximally. Concerning the five lynx callings at night and in twilights, we are not sure about types of spots, from which the lynxes were calling. Only in one case we were more or less convinced that a lynx was calling from a treefall. Perhaps, one calling by a lynx was emitted from an elevated position, possibly from a tree.
All three lynx callings that we registered in daytime were emitted from standing tall trees. Once in the late February we heard many lynx calling (more than 30) and succeeded to approach the point. The lynx escaped before we see it. However, using tracks on snow cover and claw marks on trunk we found that the lynx was definitely calling from the big nest of spotted eagle, which was situated on a tall pine. Taking into account when the last snowfall was, we estimated that the lynx stayed on the nest 18 hours, at least. So, it was not only calling from the nest, but also resting and watching from there.

Another such case of lynx calling in daytime happened in the mid-February. We heard at least 72 calls of a lynx, which was sitting on a pine tree top. It emitted calls during 40 minutes. After three answers by another lynx from the opposite side of our point the lynx calling from the pine top stopped, and the lynx climbed down and disappeared.

One more such a case was in the end of April. A lynx was calling in daytime from the top of black alder, and in total we heard about 40 callings with 2 seconds to 4 minutes interval.

It is very hard to take a good photo or video of Eurasian lynxes climbing a tree, because in the majority of cases a lynx runs towards a tree trunk and jumps on it. In this case a lynx can jump 3-4 meters high on a stem. Climbing down trees, a lynx mainly jumps down from the height of 4-6 meters. So, on camera traps you see photos of the trunk, but already without the lynx, because in the majority of cases camera-traps are not fast enough to capture a climbing lynx.
There is the strange fact that earlier during the long period of 1998-2012 by doing more than 2000 km of snowtracking of lynxes, when the species population density was lower than 3 inds per 100 square km (usually between 1 and 2 inds per 100  square km), we have never faced with climbing so tall trees by lynxes. The situation was really strange, and that suggested us about phenomenon of a territorial calling by lynxes, when the species population density is rather high.

We assume that lynxes did such climbing and calling from a tall tree before too, but not so often. The key point is: what is much lynx snowtracking? In 2018-2019 in Naliboki Forest, when lynx climbing trees was registered more or less often by us, 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 climbings of trees by lynxes. But in the conditions of the lower population density of lynxes, in which the study were carried out, undoubtedly lynxes emitted territorial calls and did other marking of the territory 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 of 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. Also, a marked part of that snowtracking was done by my assistants, who might have been less focused on lynx behaviour. 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 lynx did not climb trees during that time. Possibly they did, but less frequently than nowadays.

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