aReading literature and talking with wolf and lynx researchers, it becomes evident that interference between the two species is actually poorly studied. Some mammalogists tend to assume that wolves suppress the lynx population. Some even suggest details of the aggressive behaviour of wolves towards lynxes: strong wolf packs attack lynx family groups and kill kits during lynx mating season when the kits stay alone or disperse. Seemingly, such stories are only speculative beliefs and ideas.

During vast amounts of time in the wild and a lot of field studies on wolves and lynxes in Belarus only lynxes killed by lynxes (males killed by other males and kits killed by males) were found. We never found any lynx (kits or adult) killed by wolves.

In contrast, we found several wolf pups of various age and pregnant wolves killed by lynx:

8 wolf pups of 2-11 months old and 2 heavily pregnant female wolves that were killed by lynxes (1997-2015, Naliboki Forest and Paazierre Forest);

one more pregnant female wolf was killed by either lynx or wolf (more likely to say that lynx, Naliboki Forest, May 2017);

at least, two wolf litters up two one month old were killed by lynxes (Naliboki Forest, April-May, 2016 and 2017),

two more such litters – very plausible;

one wolf litter of 2-3 months old and their small mother were very plausibly killed by lynx (Naliboki Forest, June-July 2016);

adult male wolf plausibly died being wounded after a fight with a male lynx (Naliboki Forest, April 2017).

That was mostly different lynxes, but not a single smart killer-lynx. A lot different timing and place of these interference registrations confirm that.

My point of view is clear: at least, in Belarus, lynxes, first of all, adult males suppress wolf reproduction, by frequently killing of pups and pregnant females. This, in turn, affects the wolf population dynamic, sometimes, quite heavily. Nowadays, I and my collaborators from Wild Naliboki have enough proofs to confirm that.

Below you will find some photo-material on the interference between wolves and lynxes in Nalibiki Forest in Belarus suggesting the leading role of lynxes in the interspecific interference.

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Wolf parents at burrow-den with pups inside and the visit of male lynx into the den. Afterwards, the wolf couple has lost the pups. There is snow on the photos with lynx, as it was snowing in the morning of that day in May.

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Encounter and fight between an adult male lynx and an adult male wolf. The fight took place at an important marking point and grooming place of the male lynx on an abandoned forest road. The lynx won and plausibly the wolf died afterwards from his wounds.

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Lynx visits to the active wolf burrow-den.

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An example of wolf response to lynx odour. A pack of four wolves approaching a dead tree, where female and male lynxes had marked previously by urinating. Two of the pack members cautiously inspected the tree with their ears flat, a clear sign of fear and/or subordination.

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Another example of wolf response to lynx odour. A wolf was passing at the lynx marking point, got scared and escaped galloping away.

Many people find it hard to believe that lynxes can kill healthy wolves. Indeed, even a large adult male lynx would expose itself to serious risk of being killed if it tried to fight with a wolf pack. In fact, a lynx will never attack a wolf pack.

However, wolves are not always in packs. They live in packs in the cold season (from late September untill mid-April) and even then many wolves walk around alone. In the warm season (from mid-April untill late September) wolves walking alone are more common then wolves living in small groups.

Just before denning and 10-20 days after parturition the parent wolves are alone most of the time: the mother is at the den, the father forages. Female wolves in the last decades of pregnancy are clumsy, and when their males are foraging they are very vulnerable.

The majority of yearlings that are chased away from the new denning site by their parents walk alone, even if there are several of them.

Pups of the year are another category of vulnerable wolves. They stay alone from the age of 15-20 days until they start to move with the parents (i.e. from mid-May until mid-September). During these months wolf pups can easily be killed by lynxes.

Moreover, we got convinced that an adult lynx, especially a big male can win a fight from any lone wolf. We photo-documented a fight between a not very big and quite old male lynx (older than 8 years) and a (not small) adult male wolf. The lynx threw the wolf on its back, attacking it’s belly. Obviously the lynx won the fight and most likely the wolf died from his injuries. Before the fight we photographed this easily recognizable wolf frequently, five minutes after the fight the clearly wounded wolf was photographed one more last time.

So, by near consideration lynxes have plenty of opportunities to kill wolves.

Besides attacks of adult lynxes on lone weakened wolves we faced with scaring lynxes away from their kills by wolf packs and consuming of the kills. That is also considered as acts of interference competition between wolves and lynxes, during which wolves suppress lynxes. Read about that in a separate post.

In the below you may find a quite long text on the interference between the Eurasian lynxes and grey wolves in Belarus from the Chapter 14 of the book “Unknown Eurasian lynx: New findings on the species behavior and ecology”, which we (Vadim Sidorovich, Jan Gouwy and Irina Rotenko) are preparing for publication. It is partly the same results as in the above, but there are more details, more discussion on the question and our inferences. Also, it is still rough text and without photos, which you partly saw in the above. Anyway, it may be interesting for you with the extra information on the question.

Chapter 14. Interference with and killing of wolves, respective effect for the wolf population

Statement. Adult lynxes, particularly males, deliberately hunt and regularly kill vulnerable categories of wolves such as pups of various age, heavily pregnant females, wounded or somehow weakened (e.g. ill) individuals, small subadults or even just any not a big wolf that is walking alone. On the other hand, lynxes (kittens or adults) are only rarely killed by wolves.

In effect, wolf reproduction may be suppressed by frequent killing of wolf pups and pregnant female wolves by mainly adult male lynxes. This, in turn, affects the population dynamics of wolves, sometimes, quite heavily. Since lynxes became numerous in our main study area in Naliboki Forest (2 to 5 inds per 100 km2), recruitment in wolves almost stopped because most of the pups are being killed by lynxes. This, in turn leads to a different packing pattern in wolves: from packs consisting mainly of related individuals (family origin packs) to packs consisting mainly of non-related and subordinated individuals.

Usually wolves avoid visiting the spots, where lynxes mainly stay. However, wolves sometimes scare lynxes away from their kills, which is also an essential part of the on-going interference between wolves and lynxes in Belarus.

The pattern of habitat usage by lynxes with the absolute preference of forested biotope is resulted from the on-going interference with wolves, when a lynx out of tree stand may be killed by wolves.

Publications in relation to the statement.

Specific studies in the wild on interactions between wolves and lynxes

Although Eurasian lynxes and grey wolves are two large carnivores that are sympatric in large parts of their range, few researchers have studied both species simultaneously in the same study area. Besides our own studies on the topic, which have already partly been published (Sidorovich and Rotenko 2018), we found only two studies that attempted to specifically investigate interspecific interactions between lynxes and wolves in the wild (Schmidt et al. 2009, Wikenros et al. 2010).

In the Polish part of the Bieloviezha Forest, spatial interactions of both species were investigated by means of VHF-telemetry; three wolves and seven lynxes were radio tracked simultaneously between 1994 and 1996. Considerable overlap between the wolf pack territories and lynx home ranges were registered and both species were sometimes registered in close proximity (less than 1 km) to each other. Statistical analysis of the spatial data showed that lynxes and wolves neither avoided nor attracted each other (Schmidt et al., 2009), which made the authors conclude that wolves and lynxes co-exist peacefully in the Bieloviezha Forest, due to niche separation and heterogeneity of the habitats. As we mentioned in the introduction, the Bieloviezha Forest is not so heteregenous if we compare it with our study area’s in Belarus, and we have evidence of all but peaceful co-existance between wolves and lynxes. Moreover, the authors point out that we should be aware of the small sample size and the fact that the whole populations of both predators weren’t monitored in the study area. Also, the time span of the study is very short. As the telemetry study was not combined with camera trapping and track inspection, we don’t know how the studied lynxes and wolves really interacted and how they affected each other’s behaviour, something that we cannot learn through spatial analysis of telemetry data alone.

In south-central Sweden, competition between a recolonizing wolf population and an established lynx population was investigated by analyzing telemetry data (VHF and GPS) and data derived from several census methods of lynxes and wolves (Wikenros et al., 2013). Lynxes did not avoid using wolf territories (i.e. lynxes had overlapping home ranges with wolves) despite the fact that large parts of the study area had no wolves. At a rough scale (the home range scale), there is no spatial segregation between lynxes and wolves. This is a similar situation as in many other areas where wolves and lynxes co-occur (Zheltukhin, 1986; Danilov et al., 2003; Matyushkin and Vaisveld 2003; May et al. 2008, Schmidt et al., 2009). Survival of 16 lynx litters inside wolf territories did not differ significantly from 17 lynx litters outside wolf territories. To test whether lynx females would select different den sites after wolf recolonisation, radio tracking data from three lynx females were analysed. Lynx females appeared to use the same local area for denning before and after wolf establishment. However, the mentioned denning areas used by the three females before and after wolf recolonisation are very large: on average 24.4 km²: far too large to notice possible changes in den site locations. Unfortunately, despite a large potential for interesting information on denning by lynxes (17 female lynxes were radio collared and survival of 33 lynx litters was assessed), details about the den locations and physical nature of the dens are absent in the publication. These factors are extremely important to avoide intraguild predation and thus for the survival of lynx kittens (see Chapter 8), and crucial for a better understanding of the complex relation between lynxes and wolves. They also tested whether lynxes would increase their home-range size due to exploitative competition with wolves, this turned out not to be the case. Space-use by individual lynxes remained unchanged after wolf establishment as well but was this only investigated for three females. No evidence of kleptoparasitism by wolves on roe deer killed by lynx was found, however, as far as we understand from the description, only nine roe deer killed by two female lynxes were found in an area occupied by one wolfpack. The authors concluded that the intensity of interference and exploitation between wolves and lynxes was low. Interestingly, their initial hypothesis were based on a wide-spread belief that wolves might have a negative impact on lynx populations but not vice-versa, so interference was only investigated one-directional. In the introduction the authors state that they expected that competition between the two species would be high and assymetrical, based on the prediction that interference competition between carnivores is highest between species with intermediate differences in body-size (Donadio and Buskirk, 2006). In this case, the larger predator (the wolf) is expected to be dominant over the smaller predator (the lynx). However, even though this might true in most cases, the threat emanating from one predator towards the other is without a doubt dependent on more factors than size differences alone. Of course, the local situation in south-central Sweden was not well suited to study the impact of lynxes on wolves, as wolves were just recolonizing parts of the study area. Perhaps there was little impact of recolonizing wolves on lynxes in the study area in south-central Sweden. Unfortunately, we can only read about spatial analysis and – statistics in the publication and there is a total absence of descriptions of habitat features and behavioural aspects of lynxes and wolves. These aspects are crucial to understand the relation between lynxes and wolves. As we stated above in the discussion on the publication on the topic by our Polish colleagues (Schmidt et al. 2009), spatial and statistical analysis of telemetry data alone is not enough to understand the complex interactions between these two elusive and hard to study predator species.

Comparing population dynamics

In the absence of specifically designed studies to answer the questions on interference and exploitative competition, several researchers have made statements in the past about the relation between wolves and lynxes based on hunting statistics and reported numbers as a method to compare population dynamics of both species. In the Russian monograph on lynx (Matyuschkin and Vaisveld, 2003), most information regarding this topic is based on such reports. Negative impact of wolves on lynx numbers is suggested, as lynx numbers reported from area’s with wolves were lower compared to area’s without wolves. In the same monograph, simultaneous increase of both predators was reported in western Siberia (Azarov & Shubin, 2003). In Poland, the populations of lynxes and wolves in the region around Bielaviezha Forest increased simultaneously as well (Jędrzejewska & Jędrzejewski, 1998). This might be because both predators had unsaturated populations and started to re-occupy large area’s with many vacant territories, as we have evidence for similar situations in Belarus. Anyway, it’s quite clear that these methods are very rough, and they certainly don’t provide us with much insight on the interactions between lynxes and wolves.

Interspecific killing between wolves and lynxes

In the review on interspecific killing among carnivores by Palomares and Caro, 1999, no records of wolves killing lynxes or vice-versa are reported, neither in an additional list of cases provided by Donadio and Buskirk, 2006. There is only one known record of a wolf scat containing lynx hair in the Bielaviezha Forest (Gavrin and Donaurov, 1954), which is by no means evidence of a wolf killing a lynx, as it might have concerned a case of scavenging. Of course, interspecific killing among carnivores of similar size is usually triggered by competition and usually does not involve consumption of the killed predator. Snow tracking is a suitable method to find wolf kills (consumed or not) and has been frequently used by several researchers to study wolves in the wild. Wikenros et al., 2013 compiled snow tracking data of wolves from several studies in Scandinavia, totalling more than 15.600 km: lynxes killed by wolves were never found. Only Matyushkin and Vaisfeld, 2003 provided a list of cases, where lynxes were suspected to have been killed by wolves. However, the majority of this information was provided by hunting wardens and we have reasons to question the reliability of these records. To determine the killer with certainty, careful examination of the carcass is required. As we mention further in this chapter where we present our own findings, we found several lynxes killed by other lynxes and wolves killed by lynxes (Sidorovich and Rotenko, 2018), but so far we never found a lynx killed by a wolf in Belarus.

No records of wolves killed by lynxes found by other researchers are known to us.

Kleptoparasitism

In the Polish part of Bielaviezha Forest, 214 carcasses were inspected for a study on carcass use by scavengers. Of the carcasses killed by lynx (n = 10), 20 % was visited by wolves (Selva, 2005). As mentioned above, no evidence of kleptoparasitism by wolves on lynx kills was found in Sweden, however, as far as we understand from the description, they found only nine roe deer killed by two lynxes in an area of one wolf pack (Wikenros, 2010). Inversely, we couldn’t find any record of lynxes feeding on wolf kills in literature.

Interestingly, in the Dinaric mountains of Slovenia and Croatia, brown bears usurped 30 % of lynx kills (n= 83) (Krofel et al., 2012). Similar interference between wolves and lynxes might occur in regions, where wolves are abundant. However, it’s clear this has not yet been studied thoroughly.

Exploitative competition

To assess competition over food between wolves and lynxes, a meta-analysis of 15 dietary studies on Eurasian lynxes and Grey wolves in Europe was carried out (Lelieveld, 2013). Statistical analysis of the data from the dietary studies suggests that lynxes consumed fewer roe deer and more wild boar, hares, lagomorphs and birds in the presence of wolves. The explanation for this would be competition with wolves (as the supposed dominant predator species) over roe deer. However, local prey availability was not published in most of the dietary studies and thus could not be taken into account in the meta-analysis. It speaks for itself that it has no sense to make a statement on competition over prey between wolves and lynxes, if this crucial factor can not be taken into account. Unfortunately, statistical comparisons between study areas in bio-geographically different regions are often made with a far too simplified view on the complex relations between predators and their prey.

Schmidt et al. 2009 commented that lynxes and wolves might peacefully co-exist due to niche separation in the Polish part of Bielaviezha Forest, as wolves there mainly preyed on red deer (Jedrzejewski et al., 2000) and lynxes mainly on roe deer, but still to a considerable extent on red deer fawns on does (Okarma et al. 1997). In south-central Sweden, lynxes mainly preyed on roe deer, and wolves mainly on elk, but still to a considerable extent on roe deer (Wikenros et al., 2010). In most areas in Europe, there will always be a considerable degree of overlap between the diet of both predators. In the Naliboki Forest in central-western Belarus, lynxes were entirely specialised on roe deer before the local roe deer population crashed in 2013 (Chapter 12). At that time roe deer were the main prey species of wolves as well, closely followed by beavers and to a lesser extent by wild boar. After the crash in roe deer wolves had a more diversied diet, still with beavers as main prey but supplemented with large ungulates (elk and red deer) and medium-sized carnivores (Sidorovich et al. 2017). Lynxes diversified their diet as well, however with large individual differences. Beavers, raccoon dogs, red deer, wild boar, hares, grouse and other small prey all became important prey items to a varying degree depending on the individual lynx (details in Chapter 12). So, in regions with a wide range of potential prey species for wolves and lynxes, there is always a certain degree of overlap between the diet of both predators. At the same time our findings in central-western Belarus demonstrate how complex and difficult to analyse exploitative competition between two predators may be.

Assumptions on why this had not been studied before.

To study interactions between grey wolves and Eurasian lynxes, a large study area, where both species are common, is required. This is in itself not so easy to find in Western Europe, where most studies on lynxes and wolves in Eurasia took place. Moreover, simultaneous study of both predator species in one study area in the wild requires huge efforts and (financial) investment.

In attempt to study these relations, researchers tend to analyse spatial data from telemetry or census data with computer software. As mentioned above and in the introduction of this book, there are limits to this approach and it may even bring artefacts. It can only brings results on a rough scale, such as demonstrating overlap of home ranges of both predator species. Behavioural details of their interactions, however, remain unknown without habitat inspections, reading of tracks and activity signs of the species and applying smart camera trapping.

Materials, data and other information sources in relation to the statement.

After analyzing the available literature, it becomes evident that interference between lynxes and wolves is actually poorly studied. This becomes even more clear, when discussing the topic with wolf and lynx researchers. There is a variety of opinions on these large carnivore relationships; and quite many mammalogists tend to assume that wolves suppress the lynx population. Some even suggest details of the aggressive behaviour of wolves towards lynxes: strong wolf packs attack lynx family groups and kill kittens during lynx mating season, when the kittens stay alone or disperse. We have the impression that most of these stories are only speculative beliefs and ideas.

Lynxes killing wolves

During vast amounts of time in the wild and a lot of studies on wolves and lynxes in Belarus (mainly in Naliboki Forest and Paazierrie Forest in 1995-2017), we never found any lynx (kitten or adult) killed by wolves. We only found lynxes killed by other lynxes (adult male killed by other adult male and kittens killed by adult males). In contrast to that, we found several wolf pups of various age and pregnant wolves killed by lynxes Presence of lynx tracks, lynx hairs and lynx bite marks on the wolf carcasses provided evidence that they were killed by lynx. Those findings of the period of 1997-2015 in Naliboki Forest and Paazierre Forest were as follows:

two heavily pregnant female wolves were certainly killed by lynx;

one pregnant female was plausibly killed by lynx, in this case we can’t exclude another wolf as the killer with certainty;

eight wolf pups of 2-11 months old were definitely killed by lynxes; one case where wolf pups less than one month were certainly killed by lynx.

Camera trapping combined with track reading provided us with further proofs. We have registered lynxes systematically following wolves and inspecting freshly used wolf burrows and dens during wolf denning season to search for wolf pups.Cases of wolves killed by lynx, registered with camera trapping and track reading:

two wolf litters up to one month old were certainly killed by lynx (Naliboki Forest, April-May 2016 and 2017)

two more litters up to one month old were very plausible killed by lynx (April-May 2017);

one wolf litter of 2-3 months old and their small mother were very plausibly killed by lynx (Naliboki Forest, June-July 2016);

an adult male wolf presumably died from its injuries after a fight with a male lynx which we are able to document with photos (Naliboki Forest, April 2017).

These cases concern not just one lynx, who became a smart wolf killer, but several lynxes, as they were recorded in different locations. On the photo’s we can see several territorial males we recognize by their individual fur spot pattern, as we closely follow them by camera trapping. Many people find it hard to believe that lynxes can kill healthy wolves. Indeed, even a large adult male lynx would expose itself to serious risk of being killed, if it tried to fight with a wolf pack. In fact, a lynx will never attack a wolf pack. However, wolves are not always in packs. They live in packs in the cold season (from late September until mid-April) and even then many wolves walk around alone. In the warm season (from mid-April until late September) wolves walking alone are more common than wolves living in small groups. Just before denning and 10-20 days after parturition the parent wolves are alone most of the time: the mother is at the den, the father forages. Female wolves in the last decades of pregnancy are clumsy, and when their males are foraging, they are very vulnerable. The majority of yearlings that are chased away from the new denning site by their parents walk alone, even if there are several of them. Pups of the year are another category of vulnerable wolves. They stay alone from the age of 15-20 days until they start to move with the parents (i.e. from mid-May until mid-September). During these months wolf pups can easily be killed by lynxes.

Moreover, we got convinced that an adult lynx, especially a big male can win a fight from any lone wolf. We photo-documented a fight between a not very big and quite old male lynx (older than 8 years) and a (not small) adult male wolf. The lynx threw the wolf on its back, attacking it’s belly. Obviously, the lynx won the fight and most likely the wolf died from his injuries. Before the fight we photographed this easily recognizable wolf frequently, five minutes after the fight the clearly wounded wolf was photographed one more last time.

So, by near consideration lynxes have plenty of opportunities to kill wolves.

Body language and marking behaviour as indicators of interspecific relations

Camera trap images can also show us the body-language of lynx and wolf, giving clues about their interspecific relations (e.g. wolves taking subordinate postures at lynx marking points).

Below some examples of the responses of wolves to lynx odour, documented by camera traps:

a pack of four wolves approaching a dead tree where a female and a male lynx had marked previously by urinating. Two of the pack members cautiously inspected the tree with their ears flat, a clear sign of fear and/or subordination.

a male wolf was photographed crossing an abandoned forestry bridge with extreme caution (walking very slowly, step by step). Later on the same day when the pictures of the wolf were taken we found fresh tracks revealing why the wolf behaved this way: a lynx walked by shortly before the wolf arrived. The lynx approached the bridge from the ice and walked just outside the detection zone of the camera trap. When the wolf appeared, it hesitated to cross the bridge, inspected the lynx tracks and cautiously walked in its footsteps. There are no pictures of the lynx but its footprints can be seen on the pictures with the wolf, while they were missing in earlier pictures of other animals crossing the bridge.

By camera trapping important marking points of both lynx and wolf we found a consistent pattern. Wolves are usually interested in lynx marking points and inspect them with caution, while lynxes photographed at wolf marking points usually act indifferent and uninterested.

Kleptoparasitism by wolves

Besides attacks of adult lynxes on vulnerable or lone wolves we found evidence of kleptoparasitism of wolves on lynx kills. This is an act of intereference competition between wolves and lynxes, where the roles are turned around and during which wolves suppress lynxes. Registration of these events are easiest in winter during snow tracking, however it’s reasonable to assume this phenomenon mostly happens in winter, when competition over food is more severe and wolves are mostly in packs and have the upper hand on lynxes.

Here we would like to share an outstanding case of kleptoparasitism where a lynx family was scared away from their kill by two wolves. To tell this story we will share an excerpt from a trip report by Els Lavrysen and Hans Van Loy, a couple of Belgian naturalists who joined a wildlife trip with the volunteers of Wild Naliboki from 1-10 february 2018 in Naust Eco Station, Naliboki Forest.

…

Wednesday 7

The conditions are perfect today, so Pepijn will do some snow tracking in the area where Vieranika (it is the name of this mother lynx) and two kittens (plus previously one subadult) live. Fresh lynx tracks cross the road. These tracks weren’t here yesterday evening, so it’s unlikely we’ll find better ones!

We leave Pepijn, imagining what it would be like: all alone in the forest, only accompanied by the silence and sounds of this big wilderness. Maybe a meeting with elk or deer, … It would be great to join him or do some snow tracking ourselves one day.

Pepijn is following the tracks in the opposite direction. One moment, Vadim stops the car and asks if someone wants to follow the tracks in the other direction? Yes, of course we want to!

A little bit unprepared (both in equipment and in mind) but excited, we put some bread, cheese and sausage in our backpacks, take some matches in case we get wet and receive some last instructions from Vadim. We agree to meet again at 6 pm. We mark our position in our smartphone and off we go. The phone is our only GPS, but it’s probably best to rely on our own footsteps to get back to the car.

The tracks of Vieranika and the kittens are clearly visible and near the road we see a few small marking places from the mother (rubbing small trees). It seems one of the kittens is more adventurous and regularly splits from the others for short times. But every time, the tracks come together again.

Lynxes don’t always follow the easiest path for people: they walk on ice where we bag through, they crawl through low bushes and jump over canals we can’t jump. But it’s all very enjoyable to see where these lynxes have passed before us. And this track is not that difficult. We use small beaver dams, humps of grass, …

After a while wolf tracks appear from the opposite direction and close to the lynx track. It’s difficult to count them, because they are going back and forth. It’s also quite swampy terrain so it’s difficult to follow the right tracks. But Hans persists and we eventually find the lynx track again.

One moment we are on a small elevation in the terrain. We already heard and saw two raven hanging around for a while. Suddenly Els whispers: “Hans, straight ahead, something is standing there…” One hundred meters in front of us, partly hidden between the birch trees, we see a red-brown back and the base of a bushy tail. It’s not like a deer and it’s certainly not an elk. It takes a few seconds before Els whispers the words we could only dream of: “It’s a wolf…”

The animal lifts up his head and looks around. Wow, what a big wolf with a massive head and thick hair! “There are two!” A few meters to the right another back is visible through the trees. He lifts his head as well. We try to be like a salt pillar, because sometimes they seem to look straight into our eyes/binoculars. We’re looking at wild wolves, this is truly unbelievable. One wolf is carrying and eating a blood-red piece of meat. The ribs are clearly visible. Incredible, we just found a recent kill!

Was it because of a noise we made (Hans was trying to take out his camera as quiet as possible)? Or was it the breeze coming from behind us? But the wolves lift their head again, look in our direction, smell the air and fly.

How many time had passed? Three of four minutes at least. We squeeze each other’s arm and realize this was a once in a lifetime experience! What a thrill!

At the kill site, we feel like real crime scene investigators: what happened? The tracks of the wolves are clearly visible, but there are also lynx tracks at the carcass. It’s a roe deer, eaten to a great extent. The hind legs and one of the forelegs is still present as well as part of the chest, but the head is nowhere to be found. A few meters from the carcass, we find the place where the roe deer was killed and eaten: a lot of greyish hair, blood on a little spruce and on the ground, remnants from an intestine,… There’s also a resting place nearby with a lot of lynx tracks. Between the place from where we watched the wolves and the kill, the lynx tracks had split. One was going around, the two others stayed together. We suppose the rode deer was killed by Vieranika, while the kittens stayed aside.

We send a message to Vadim. They might want to see this as well. It’s a pity that we couldn’t share this experience with the whole group, but it would have been very difficult to stay unnoticed.

We try to pick up the traces from the lynx family again, but it’s very complicated and Vadim is returning earlier to put a camera trap near the carcass.

We meet again at the car and lead Vadim to the site. First he gives his interpretation of the scene. Pepijn found another place where a lynx had been lying under the dense canopy of a spruce nearby the roe der carcass. According to Vadim this was used by Vieranika as an ambush. Somehow the wolves were led to this place. Perhaps, they follow the ravens when these scavengers found the carcass.

A pygmy owl starts calling nearby. The camera trap Vadim is installing is not the best one and it seems not to be functioning properly, but Vadim persists to make it work. This case is too interesting to miss a thing! Who would come back tonight? What would happen? We are all highly interested!

…….

Thursday 8

When we arrive next day after lunch there are wolf tracks on the road. Would the carcass still be there? If it has been moved it’s possible that we won’t have any picture… On the way to the camera there’s a wolf track with a little bit of blood aside. Did they take it?

The carcass is gone. But when we check the camera trap there are pictures of lynx! Vieranika returned yesterday, only half an hour after we left. Maybe she was watching us while we were installing the camera…! The kittens showed up one hour later. The last picture was taken three hours after Vieranika’s first visit.

It’s really amazing to see how wolves and lynxes interfere with each other in this vast wilderness…. So, in the above-described case from all available sources of information (snowtracking, activity signs of wolves and lynxes at the roe deer carcass, visual observation, camera trapping etc.) we finally learned the following. The mother lynx (we call as Vieranika) noticed the roe deer group in young succession forest, it hid in the ambuscade under the small spruce. Then she was waiting for a roe deer getting closer. After killing it she called for kits, which were waiting about 300 meters away. The lynxes started consuming the roe deer. Ravens discovered them at the kill and began screaming. This attracted wolves. They came and chased away the lynx family from their food. However the lynxes stayed not far away, and when Els and Hans scared the wolves, and we left the place, the lynx family returned to the roe deer carcass and consumed it almost all during one night. The wolves came back the next afternoon and found poor remnants of the kill and they consumed them entirely.

During the late 1990s and 2000s in Naliboki Forest and Paazierre Forest, we found three more cases of kleptoparasitism by wolves. In the first case, a lynx female with three kittens just started eating on their kill, a roe deer, when a pack of six wolves chased the lynxes in birch trees; consumed the kill entirely, and stayed around the birch trees, where the lynx family was sitting; however, none of the lynxes were wounded or killed. This first case was reconstructed by following recent signs left by all those animals on the snow cover.

In the second and third cases, a young red deer was killed by a lynx, but was mostly consumed by a pack of wolves. Nevertheless, when the wolves were absent at the red deer remnants, the lynx returned to the kill to feed. In these two cases, it again seems that the raven calls attracted the wolves. Based on these four cases, we can assume that kleptoparasitism by wolves on lynx kills is not rare, and this phenomenon is an essential part of on-going interference between wolves and lynxes in Belarus.

Impact of lynx on reproduction, pack composition, immigration and emigration in wolves

Since 1999, the wolf population of Naliboki Forest has been thoroughly monitored and its reproduction biology meticulously studied (Sidorovich 2016, Sidorovich & Rotenko 2018). Over the years 1999-2014, the number of wolf packs varied between 6 and 14, and the number of wolves between 27 and 70. Wolf population density in early winter varied from 0.9 to 2.5, with mean of 1.8/100 km². A total of 37 dens with pups and 92 denning plots with recent dens were discovered. Litter size in May ranged from 1 to 11, with a mean of 5,8. Before 2015 pup survival by the beginning of winter was on average 52%.

Sudden and dramatic changes in wolf numbers and pack composition were limited, and mostly related to killing of wolves by hunters. These changes generally occurred predictably during and shortly after wolf hunting season in late winter (February-March). After 2010, wolf hunting was limited or restricted in a part of Naliboki Forest. Despite the (irregular) killing of wolves by hunters, there has been a fairly high stability in the wolf population for many years.

In recent years, lynx numbers have increased markedly in Naliboki Forest: from 22 in 2013-2014, more than 40 since 2015 to about 85 in 2017-2018. At the same time, we start to notice three pronounced processes in the wolf population: disappearance of the majority of litters and pups (extremely low pup survival rate), immigration of wolves in January-February and emigration of wolves in April. That becomes clear already in the winter-spring of 2015-2017, having 40-60 lynxes there, and that was particularly pronounced during winter-spring of 2017-2018 with about 85 lynxes (see the wolf distribution maps).

As we see on the wolf distribution maps of 2015-2017, the survival of wolf pups was very low:

after 6 or 7 litters in May 2015, we registered only 4 pups in late November 2015

only 6 pups of the year were registered in the early winter of 2016, despite the fact that we registered 10 litters in May 2016

from the 7 litters that were traced during summer 2017, only two pups survived until October 2017.

In January-February 2016, 2017 and 2018, many wolves arrived in Naliboki Forest, so that the local wolf population almost doubled compared to the first half of winter. The phenomenon of large-scale immigrations might have happened in the winter 2014-2015 already, but we weren’t able to record these changes in detail due to the weather conditions.

In late March and April 2016, 2017 and 2018, an essential part of the local wolf population (perhaps, mostly breeding groups) emigrated from Naliboki Forest. During these years, wolves were confronted with high lynx densities and many other newly arrived wolves in late winter. We think this triggered the wolves to leave the forest again in search of safer denning areas with no or fewer lynxes and less other wolves. Those can be found in more rural landscapes where forest fragments are interspersed with open agricultural land.

Especially that was pronounced in the spring 2018, having about 5 lynxes per 100 km2 in the terrain. In May 2018, when only one (maximum four) breeding group of wolves out of more than 20 wolf breeding units registered in late March and early April remained in the forest massive for denning. We are sure of these results. From two to five of us worked for 40 days since the end of April until the 8th of June, and we discovered only 9 dens from one wolf breeding group consisting of two breeding females and one male. Before the unfavourable situation for wolf denning (i.e. the terrain appeared to be densely occupied by lynxes that are aggressive to wolf denning), one to three of us worked for 25-30 days and found several hundreds of wolf dens including 2 to 5 actual ones i.e. with pups. At that time there were usually only 8-13 wolf breeding groups in mid-April.

On the whole, after Naliboki Forest were densely inhabited by lynxes we found three trends in wolf denning behaviour. First, it is the mentioned emigration of breeders out of Naliboki Forest to den in the forest-agriculture mosaic surrounding the forest massive. There the majority of residential wolves are killed each winter during the species population control actions. Intensive camera-trapping in Naliboki Forest in 2015-2017 suggests that, at least, a part of such emigrated breeders comes back to their previous territories in the next autumn, but still it is hard to say what the reproductive efficiency of such breeders is. Actually, we documented only two, maybe three such cases (wolves are not easily recognisable by camera-trapping), and in one of the cases the returned pack of nine wolves had 3 or 4 pups of the biological year.

The second trend in the denning by wolves in Naliboki Forest is the increasing use of pine stands as a main denning habitat type. During the first decade of the 2000’s and early 2010’s only about 6% of the wolf dens, which were found by us (mostly without pups, recent ones, n=736 dens), were situated in pine stands. Quite opposite, in the new unfavourable situation for wolf denning in Naliboki Forest since 2016, about 52% of the wolf dens, which were registered by us (n= 104, again mostly without pups, recent ones), were found in pine stands. This switch in the used denning habitats by wolves may be explained merely by potentially less disturbance of breeding wolves by lynxes (also by bison, elk and red deer stags, which number got higher in the last years too) in pine stands, because these habitats are poor in food and poorly structured and thus markedly less frequently used by species that are hazardous to denning wolves.

Another evident trend in the wolf denning behaviour in Naliboki Forest is the increasing use of burrows to place pups during their first days, perhaps, as an attempt to save the pups from attacks of the above-mentioned inimical animals, first of all, the lynx. Before the new situation in Naliboki Forest breeding wolves mostly used open couch-dens. These dens were not so easily noticeable for the inimical animals, and when too many mosquitos or too much smell accumulated at such a couch-den, the parent wolves easily relocated the pups in a new couch-den. Perhaps, it was also essential that not much effort was needed to prepare a new simple couch-den. Usually such couch-dens were situated in treefall. In the first decade of the 2000s and early 2010s, 72% of the wolf dens, which were found by us in Naliboki Forest (mostly without pups, recent ones, n=736 dens), were found in treefalls. Quite opposite in the new unfavourable situation for wolf denning in Naliboki Forest since 2016, about 68% of the wolf dens, which were registered by us (n= 104, again mostly without pups, recent ones), were burrows or cavity-dens.

Quite often when wolves prepare a burrow-den, they do so by enlarging the entrance of a badger sett or red fox earth. This means there are still plenty of narrow passages, made by the former owners (badgers or foxes), where the wolf pups (or at least, a part of them) may escape in the case of a lynx attack.However, during the last 7-9 years we registered a rather fast recovery of the badger population in Naliboki Forest, in the background of the decline in raccoon dogs. The recovered local population of badgers occupied not only all former badger setts, but also all present red fox earths, former wolf burrows and even abandoned beaver burrow networks in sandy banks of drainage canals. So, such a safer possibility for breeding wolves to den in abandoned badger setts became markedly more limited. We think that badger population recovery accelerated the spring emigrating of wolf breeding groups from Naliboki Forest as well.

In 2014-2018 we registered several lynx attacks on wolf dens in the Rabachova locality of Naliboki Forest and documented the behavioural responses of those breeding wolves. During four breeding seasons (2014-2017) the breeding group of wolves (two to three breeding females and one to two adult males, both not small ones) had lost all their pups already somewhen before early autumn, despite the fact that in April-May of each these years there were one to three litters in the breeding group. In late April 2016, by reading the activity signs from the local wolves and lynxes, we got more or less convinced that, at least, one wolf litter was killed by a male lynx.

In early May 2017 (on the 5th and 11th), the same male lynx killed two litters from the wolf breeding group for sure. We succeeded to document these events (e.g. see above photos from the Rabachova locality of Naliboki Forest). Several days after the second litter was killed, the third litter had disappeared as well, and the most plausible explanation is that this third litter was killed by the same male lynx, too. Similarly, we are almost sure that the unsuccessful breeding of the wolf group in 2014 and 2015 was because of attacks of the same or another lynx.

In the denning season of 2018 the same wolf breeding group started preparing dens in mid-April in the Rabachova locality again, but then, after facing with lynx presence in the denning habitats and after the experiences of lynxes killing their pups during previous breeding seasons, they seemed to escape out of the forest massive. Suddenly, after much preparations for denning they just disappeared. We undertook a lot of efforts to find the new denning locations of the wolves, but we didn’t find anything that suggested new attempts to den inside the forest.

Now let us compare wolf reproduction and pack formation before and after lynxes got so numerous.

In the early winter of 2008-2012 in Naliboki Forest and the surrounding forest-agriculture mosaic (an area of about 2700 km²), there were 51-70 wolves . The portion of pups of the year (0+) was 25-44% and 86% packs were of family-origin (perhaps, some of these packs contained a few non-relative, subordinated individuals).

In the early winter of 2015-2018 in Naliboki Forest and the surrounding forest-agriculture mosaic (an area of about 2700 km²), there were 40-46 wolves . The portion of pups of the year (0+) was 4-18% and the majority of the packs (at least, 63%) were entirely or mainly of non-family origin, i.e. mainly consisted of nonrelative subordinated individuals.

So, before 2015 the wolf population in Naliboki Forest was considerably more stable and wolf packs were mainly of family origin (Sidorovich, 2016). Since 2015, low wolf numbers and instability in the packs at the beginning of winter allows vagrants to settle during wolf mating season, resulting in instable packs with mainly nonrelative, subordinated individuals.

As described above, we have many evidences of lynxes killing wolves, and not vice versa. In recent years, there has been a marked increase in lynx numbers and a total absence of any other significant changes that might affect wolf population dynamics (e.g. increased poaching, diseases etc.). So, evidently these recent changes in wolf population dynamics are connected with lynx interference.

With the current high lynx densities, the Naliboki Forest acts as a reproduction pitfall for wolves. The wolf population persists, not because of reproduction, but due to immigration from adjacent rural areas with fewer lynxes.

The findings above demonstrate the complexity which has to be taken into account when considering the possible impact of lynxes on wolf populations. If one would only compare wolf numbers in mid-winter over the years, no significant changes will be found. Taking reproduction, pup survival rate, pack composition, immigration and emigration into account reveals a completely different story.

Our conclusion is clear: at least, in Belarus, lynxes suppress reproduction in wolves, by frequent killing of pups and pregnant females, mainly by adult male lynxes. This, in turn, affects the population dynamics of wolves, sometimes, quite heavily.

The diversified and heterogeneous Belarusian forests of today, particularly the Naliboki Forest, clearly favour lynxes over wolves. However, we do not claim that lynxes are dominant over wolves in all circumstances. Other areas, where both species live, might favour wolves over lynxes.

Shift in the habitat usage by lynxes

We have stated that the pattern of habitat usage by lynxes characterized by the absolute preference of forested biotope is a lot formed by the on-going interference with wolves, because a lynx that is out of tree stand may be killed by wolves. There is a good consistency in that because in an opening a lynx, which is overtaken by wolves (a wolf is a better runner for a fairly long distance), has a little chance to survive. Lynxes know that and avoid large openings in the terrains, where wolves are common in the habitats. It is an idea, but the reality is nearly the same.

At first, we caught this hypothesis, being in Hiumma island in Estonia in the late 1990s, when the lynx was common, but wolf was rare or no wolf there. At that time in Huimmaa we faced that about two-thirds of lynx tracks were situated in openings. Those openings originated from the former marshlands and the opening structure included roads and drainage canals with willow bushes and few birth trees nearby. There lynxes mostly walked at the opening edge at the border with forest, but simultaneously there were many crossings of the openings by the lynxes. At that time in Huimmaa we numerically registered lynx hunt-watching and resting sites in the middle of the opening somewhere at the dranage canal nearby willow bush or more frequently on hay piles. All categories of lynxes, not only adult males, but mothers with kittens and subadults visited such openings in Huimmaa rather often.

In Naliboki Forest, which has very similar ecological structure of the terrain, while comparing with the Huimmaa’s one, we registered such a lynx behaviour very rare, actually several times per a year only. In those rare cases only adult males took the liberty to walk in opening, but not faraway from the forested edges (not further than 50 meters from the forested edge). Only once during longer than 30 years being in Naliboki Forest we registered crossing of the fairly wide opening (about 400 meters) by adult male lynx.

Another example that may confirm a reality of the idea was traced in the Krasny Bor terrain of Paazierre Forest. In the 1980s there were common both lynxes and wolves, and lynxes were very rare visitors of open habitats. Quite opposite, in the period from the late 1990s to 2016 the heavy eradication of wolves that was on-going year-round got wolves rare in the Krasny Bor. In effect lynxes began visiting vast lowly forested terrain at the west side of Krasny Bor rather often; even in that area the lynx track abundance was manyfold higher than that in the densely forested localities of the terrain.