The variety of life styles of Eurasian lynxes in Belarus: a combination of the gained results and hypotheses

In Eurasian lynxes there are several age-sex categories, which are strikingly or markedly differed by their life styles.  The data that leads us (Naust Eco Station & Wild Naliboki) to this conclusion originated from about 2300 km of snowtracking lynxes, multiannual study of lynxes with camera-traps (up to 70) and much other various research results. Among them the results of two lynx telemetry projects.

Before describing the revealed differences in the life style of the different sex-age categories in lynxes to be more backgrounded in the description, we will list the main features of lynx home ranges in Belarus. As we mentioned in our lynx pilot book (Sidorovich et al., 2018), the home range sizes of indi­vidual lynxes in Belarus vary a lot. For this reason,  we did not calculate any averages or other statistics that had not much sense in such a variable situation. Home ranges of lynxes in Belarus  are always much smaller in subadults (10-43 km²) and, perhaps, in adult female without a litter (27 and 70 km²), whereas adult males may have very large home ranges – up to 203 km² (minimal 61 km²), and mothers with kittens have home ranges of intermediate size (34-89  km²). Lynx home ranges in the same sex-age category were getting larger with poor prey supply. Even adult male home ranges overlapped a lot, and if the population density is higher than 2 lynxes per 100 km², during a year in non-mating season from 2 to 6 different adult males (mean about 4) may be registered at the majority of frequently used marking points within any adult male home range. Nevertheless, almost every adult male lynx has its own exclusive territory, but it is usually not large – approximately 10-30 km². This relatively small area includes one or several housing places with guarded mating spots. Adult lynx males try to defend this small territory with several mating spots strictly from adult males. If the lynx population density in a given forested terrain is about 3 inds per 100 km² and higher, there is no doubt that the whole terrain has already been shared between adult males. Up to 4 (normally 2) adult females may live in a particular home range of an adult male, and small territories of subadult lynxes may be everywhere.

These variations in home range size of different lynx categories as well as home range inclusion are more or less similar as in the other published studies (overview in Herfindal et al., 2005). Nevertheless, the below-described so distinctive category-specific life style of Eurasian lynxes can’t be found in any other publications. Nevertheless, that is not still the precise knowledge, but still a combination of the gained results and hypothesis.

 

Of course, the most outstanding   category of lynxes is a family group that normally consists of a mother and her kittens. After parturition, the mother stays at the lair with small and vulnerable kittens and she leaves them for foraging only.  Presumably, till mid-July lynx mothers mainly hunt actively on small prey like grouses, red squirrel, mallard, young hairs or roe deer or even on voles, and she uses ambush hunting less often. Here it is important to clarify what we mean under ambush hunting, as we will frequently use this term in this text.  We define ambush hunting in lynxes as:

–          staying for fairly long in an ambuscade (more or less hidden site) and then stalking of detected prey over a short distance

–          directly jumping on a prey from an ambuscade.

For the moment there are only three registrations of a successful, direct hunting jump from an ambuscade for all lynx categories. However, we have  several hundred registrations (by hair, footprints or sometimes by taking photos with camera-traps), when lynxes were in an ambuscade for quite long time. In the most cases it was unknown, if the hunt was succesful (only 10 cases were successful for sure).

But  we come back to the life style of mothers with kittens. In the busy denning period, ambush hunting by the mother  lasts not longer than a few hours. When from August kittens begin to move with enough speed and agility, mothers start to take the kittens with them to walk. Such walks are very important in the learning process of  the kittens, but at the same time it is dangerous for the family, as wolves that live in close proximity in the same habitats  may pose a threat for the kittens.  Therefore, mother lynxes with mobile kittens, anyway tries to hide them in a safe place and supply them with enough food. She tries to keep the kittens in one sufficiently large safe place (i.e. in a dense thicket in treefall, or under an abandoned log pile, or in and abandoned badger sett), and hunts alone and regularly brings them new portions of food. Sufficiently large treefall of several layers  with a tunnel passages under the layers of fallen trees are perhaps optimal habitats for such lynx kittens to stay, because kittens have enough place to safely play there. We have got enough  registrations that wolves do not venture to enter in such habitats, if they smell a lynx there.  When a mother lynx finds such a sheltered place and provides kittens with food soon, she tries to forage in the vicinity again and keeps her kittens there as long as possible.  This may continue rather long – up to two months. But usually something unfavourable happens earlier, for instance, a disturbance by people or when the mother failed to get enough food around this spot where she leaves her kittens. So, usually such a stay of kittens in a particular spot continues for 7-12 days only. After leaving the spot of stay mother lynx walks by searching for the vacant (from other lynxes) places with a relatively rich temporal prey supply. She tries to catch prey, while moving with kittens, only dropping them behind for a short time (less than an hour). When the mother catches something bigger like roe deer or beaver or capercaillie, she tries to establish the former life style, i.e. leaving her kittens in a safe place with food, while the mother continues hunting in the vicinity.  Since mid-autumn or even earlier, mother lynxes begin applying quite long ambush hunting, when their kittens stay in a safe place and are provided with food of the previous kill.

As we found out during the last three years, quite often mother lynxes tend to accept one (or rarely even two) of their kittens of the previous biological year (i.e. subadults) that still stays in the mother home range (Sidorovich et al., 2018). Concerning the frequency of such reacceptance of subadults by their mothers, for the moment we state that 30-50% of the mothers (from each third mother to a half of them) accept subadults, i.e. one or even two kittens of the previous year. Moreover, sometimes a mother with kittens may stay with an adult male for a few days (up to about 10 days). So far we found that in such a case, the mother leaves her kittens in a safe place a markedly higher portion of the time, and the kittens are supplied with food more regularly. It looks like such two lynxes (mother and subadult or mother and adult male) are markedly more successful to forage, but that needs markedly more data to show that in precise figures. Also, compared to a mother hunting alone or just any single lynx, such two lynxes mostly apply the hunting tactics of patrolling of habitats with rich prey supply and stalking. They do so by both stalking the same prey from opposite sides; as one lynx initiates the attack by jumping, another lynx waits to attack in some ambuscade on the possible escape route of the prey. Hunting manner of such two joined lynxes should be checked much more, too. It is only the first data we gained on the question.

Having about 620 km of snowtracking of mother lynx with kittens (indeed not enough), we preliminary reconstruct that in November-early April kittens were left to stay in a safe place by the mother on average for 10-12 days (up to about 40-50 days), and the mother visits them regularly bringing food. The average duration of walking between two such  periods, when kittens are staying in a sheltered place,  was 4-6 days (perhaps from 2 to 10 days) or in distance approximately it was  30-70 km. Taking into account the data of snowtracking as well as the information of at least 6 other complete  registrations of kittens stay, during such a stay of  kittens (n=19) they were provided by two or three relatively big prey (roe deer, beaver, young wild boar or capercaillie) in 8 cases (42%), merely by one big prey in 5 cases (26%), by one relatively big and several small prey (red squirrel, voles, hazel grouse etc.) in the other 6 cases (32%). We evidently need more data, to get more solid results on this question. Here it is worthwhile to notice that mothers in heat usually do not send their kittens away to disperse before they go mating, but temporarily leave them in a safe place, just like they do when they need to hunt without kittens (may be with scarcer food supply). After mating, most mothers re-accept their kittens for a joint life for at least a month longer (Sidorovich et al., 2018). Being in heat, such a female mainly searches for an adult male by males’ scent marks, recent track trails and mating calls (Sidorovich et al., 2018).

Anyway, despite of the need for a larger dataset, principally, the life style of adult females with kittens is already clear.  Certain peculiarities are already clear as well for example subadults or even adult males temporarily staying with a mother.

Adult male lynxes have a rather distinctive life style, as well. We already know the life style of this category quite well (Sidorovich et al., 2018). To be brief, in the cold season adult males mainly stay in the surrounding of housing areas (with well-sheltered mating spots), guard them, go ambush hunting not faraway, and approximately after 6-14 (on average 7-8) days staying in the housing area with potential mating spots they undertake large walking-marking routes for 40-70 km with about 10 marks per km. This marking itinerary usually covers the whole home range of the adult male and it takes one to 3 days to complete it. During these walking-marking days adult males only hunt occasionally. These marking routes of adult male lynxes are very conservative (some parts of the route are100% the same each time they pass, other parts are the same for 70-90%). This inference is largely confirmed by both snowtracking and telemetry data as well as by camera-trap registrations, for example the walking direction of a lynx on a given pathway was the same in every of e.g. 42 photo-registrations. Adult males emit territorial (or mating) calls from elevated position on the way of their marking walks as well as at the housing areas with mating spots. It is also important to mention that for adult males to be successful in the mating season in late February-March, they need to have several thickets with tunnel-structures in their housing areas, where mother lynxes in heat may safely leave their kittens and where she may agree to mate in safety not faraway (Sidorovich et al., 2018). Such thickets we define as potential mating spots that were already mentioned above. In the warm season, adult male lynxes spend a lot of time with ambush hunting, only  switching from one place of stay to another from time to time within the winter home range. Generally, adult males apply ambush hunting markedly more often than mothers with kittens. As to hunting from ambuscades of adult male lynxes, it does not mean that adult males jump on prey from an ambuscade. Watching from an ambuscade, they mainly fix the position of a prey and then stalk the prey, if it is already on a short distance. Principally the life style of adult males is already clear. However, to know more details of this life style we need more data as well.

The next lynx category with distinctive life style consists of adult females without kittens. However, actually they have two different life styles, depending on whether they stay with an adult male or alone. Adult female lynxes living alone mainly forage by means of ambush hunting, and just this category of lynxes applies ambush hunting the most often, and they stay in an ambuscade the longest.  In this feature they are similar to adult males, but in comparison with them they do not mark so much and do not undertake long walking-marking routes (Sidorovich et al., 2018). They gradually relocate within their home ranges, slightly marking on the way (about one mark per 0.4-2 km), and then they stop in a suitable place for ambush hunting for several days.  Hunting on the way with stalking of a prey happens sometimes in this lynx category, but markedly less often than in the case of mothers with kittens. Adult females without kittens are the most passive category of lynxes: they do not mark and do not walk a lot and they mainly hunt from ambuscades. Such a life style is characteristic for adult females without kittens almost year-round, except during the mating season. This lynx category is more or less well investigated. The only problem is that some of the lone females that were snowtracked were still subadults (1+). However, such subadult females tend to have such a life style, as well.

As to a joint life of a female (adult or subadult) and adult male in non-mating season, we do not know much about their life style yet, and it is one of the pressing questions for the further studies on lynx behaviour. The first information on the question was gained in 2016-2018 (Sidorovich et al., 2018), and it suggested the following. If an adult male lynx has an adult female without kittens within its home range, it tends to join the female. For the moment, our very preliminary estimates indicate that at least a quarter of adult males frequently stay with a female out of the mating season. These females may be mainly subadults or adults whose kittens died early.  This joint stay of an adult male with a female includes cooperative hunting, simultaneously consuming of kills, grooming and sleeping. This cooperative living may last months or at least the whole cold season. However, the long walks of adult males with a lot of territorial marking are mainly carried out alone. So, cooperative living of adult male and female lynxes mainly takes place in housing areas. Until the winter of 2018-2019 it looked like this was the single relevant hypothesis on the life style of this lynx category, as it matched with all the respective data collected.

But during the last winter of 2018-2019, two known adult lynxes (male and female without kittens) stayed together at least from the end of October till April. The difference with all other cases of cooperative living of males and females registered before (Sidorovich et al. 2018), was that this pair walked everywhere together, even on the very long (as far as we learned about 70 km) walking-marking itinerary of the male  during 3-4 days. During these walks, it looked like the male marked normally as every male (about 10 marks per  km), but the female marked rarely. During the winter, they stayed a lot at the two thickets, where they mated later in March. As far as we learned, the couple hunted a lot actively by patrolling prey-rich habitats and stalking prey cooperatively. When they were at the housing area, they applied ambush hunting too: three cases were revealed versus one known active hunt there. No more may be said about the couple, but generally it is a pity that we evidently paid not enough attention to this outstanding pair.

The last categories of lynxes is subadults. Again, perhaps, there are a lot of differences in the life of subadults that follow the mother, and subadults that are acting alone. Subadults that follow the mother have the same life style as the mother. Such a subadult frequently takes part in  active hunting of the mother i.e. patrolling and stalking. Life of lonely living subadults is evidently not sufficiently known, first of all, because we preferred to track adults with telemetry, whereas during snowtracking it is always hard to know for sure if a given track trail belongs to a subadult. Nowadays, by  applying many camera-traps and knowing how subadults look like (spot patterns on their fur) we may use snowtracking correctly.  From the data we already  got, we assume that lone subadults move gradually within their rather small home range and try different manners to hunt, including both ambush hunting and active hunting.

So, from the above-described various life styles of different, mostly sex-age-related categories of lynxes we started to realize Eurasian lynxes have a high variety of life styles. It is evident that this behavioural variety is directed on successful breeding and higher survival.

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