Home range size, structure and usage of housing spots

To answer some basic questions on home range size and structure we followed several individual lynxes in two study areas:  Naliboki Forest (central-western Belarus) and Paazierre Forest (northern Belarus). We used (manifold) snow tracking, VHF-telemetry and GPS-GSM telemetry.

Home range size

From 2012 to 2014 in Paazierre Forest, in conditions of abnormal prey supply (roe deer, hares and Tetraonids were scarce but wild boar and beavers were common), lynx home ranges were relatively large:

  • adult male: 203 km2 (90% minimum convex polygon), the whole area was about 270-290 km2, GPS-GSM telemetry
  • adult male: 120 km2 (90% minimum convex polygon), the whole area was about 190 km2, VHF-radio tracking
  • adult female: 70 km2 (90% minimum convex polygon), the whole area was about 80 km2, VHF-radio tracking
  • adult female with three kits: 57 km2, manifold snow tracking
  • adult female with one kit: 69 km2, manifold snow tracking

lynx_telemetry3

In the 2000s in Naliboki Forest, in conditions of very rich prey supply (e.g. 2-19, mean 4 roe deer/km2), lynx home ranges were markedly smaller:

  • 3 adult males: 61-93 km2, manifold snow tracking
  • 4 sub-adults: 24-43 km2, manifold snow tracking

One big adult male – having a home range of 93 km2 – accepted three females in the home range. One of the females had 3 kittens and lived entirely within the home range of the male, the other two female territories overlapped for a third part with this male.

IMG_2599
Snow tracking lynx

In the winter of 2016-2017 in Naliboki Forest there were at least 10 fold fewer roe deer and wild boar (combined) compared to the situation before 2013. This crash in the roe deer and wild boar population is due to an extended period with deep snow in late winter and early spring. However, prey supply in Naliboki Forest after the crash was still richer compared to the situation in Paazierre in 2012-2014, with substantially higher numbers of beavers and red deer as alternative prey.

Home range sizes were assessed by manifold snow tracking combined with camera trapping:

  • adult male (perhaps 2+ or 3+ years of age), medium quality habitats for Naliboki Forest: 97 km2
  • adult male (older than 7+ years of age), medium quality habitats for Naliboki Forest: 135 km2 (markedly larger than before 2013!)
  • adult male, (older than 4+ years of age), very rich habitats for Naliboki Forest: 74 km²
  • adult female with 2 kittens, rich habitats for Naliboki Forest: 34 km²
  • sub-adult, rich habitats for Naliboki Forest: 10-15 km² (approximately)

Home range structure

Lynxes use only parts of their home range intensively. We call the intensively used parts ‘housing areas’. We found large differences between the size of the housing areas in the cold season (November-March) and the warm season (April-October). Below we give some examples. Housing areas are roughly illustrated as dark patches.

 

AFC

Home range structure of an adult female in Paazierre Forest from November to March (2014-2015). The 90% minimum convex polygon was about 70 km2. 39% of the home range was in relatively intensive use (87% of the radio fixes). The housing areas were 2.2 – 4.1 km in their diameters.

AFW

Home range structure of the same adult female having two kits, April-October (2014). The 90% minimum convex polygon was about 53 km². 11% of the home range was in relatively intensive use (87% of the radio fixes). The housing areas were 0.9-1.4 in their diameters.

 

AMC

Home range structure of an adult male in Paazierre Forest, November – March (2014-2015). The 90% minimum convex polygon was about 203 km². 42% of the home range was in relatively intensive usage (87% of the radio fixes). The housing areas were 1.7-4.8 km in their diameters.

AMW.png

Home range structure of the same adult male, April-October 2014. The 90% minimum convex polygon was about 156 km2; 7% of the home range was in relatively intensive use (74% of the radiofixes). The housing areas were 0.9-1.5 km in their diameters.

Usage of housing spots: findings and hypotheses

Many of the winter housing areas (8 out of 12 well-known cases in Naliboki Forest and 5 out of  14 well-known cases in Paazierre Forest) were rarely visited in summer. Looking at prey supply, the majority of the winter housing areas do not seem to be the best available areas in the lynx home ranges.

These winter housing areas are most likely chosen for other reasons. Suitability of the area for  sheltered mating might play a determinant role. Usually lynx pairs use plots of  1-3 ha with young spruce thickets and specific treefall (existing of several tree layers) for mating. These microhabitats create comfortable, snowless cavities and tunnel structures for sheltered mating. They protect the mating pair from sudden wolf attacks. All the registered winter housing areas of adult male lynxes contain several such plots of similar size and appearance. Other areas within their home range – even with markedly better prey supply – don’t contain such specific ‘mating-habitats’ that are large enough. From late autumn on, males seem to actively guard mating plots. In mating season males mainly roam around in the vicinity of the mating plots, waiting for females. Area’s around the mating plots (several kilometres away) are marked very intensively by males.  Guarding these mating plots seems to be the most important tactic males use to get access to females. Perhaps, this is one of the main factors determining the choice of winter housing areas  in male lynxes. Roaming far away in search of females is a tactic that males use as well, but it comprises only about one third of their mating behaviour. Females in mating season seem to actively search for males with housing areas which contain several suitable mating spots.  Several of these spots in a housing area also allow the mother lynx to  leave her kittens in one of these spots when she goes mating in another spot not far away. This way the kittens are protected against wolf attacks as well.

During the warm season, both males and females have considerably smaller housing spots compared to the cold season. They can spend weeks in very small areas. Why do they do this and how do they survive, living for weeks on end in such a small piece of forest? To investigate this we used tracking and camera trapping (see methodological approach).

We found that these small housing spots in the warm season are connected with hunting behaviour: in the warm season lynxes mainly use a specific type of ambush hunting. By waiting for prey from a hide 2,5 – 4 meters above their pathways, lynxes can exploit passing prey from a larger area. Indeed, in the warm season several prey species use predictable multi-annual pathways, especially near seasonally abundant food sources (e.g. the first spring herbaceous cover in forest on rich soil; acorns from late August-November in oak stands; blueberry and other berries in pine stands in July-September; areas around leks of black grouse and capercaillie, which contain nests and fledglings in May-August;  etc …). At the same time, waiting for prey from a height offers lynxes protection from mosquitoes: a few meters above the ground there are already hardly any mosquitoes.

IMG_8161sh
The first spring herbaceaous growth in forest on rich soil attract a lot of prey. In autumn acorns have the same effect on prey movements. In such habitats lynxes wait in a ambush on trees 2.5-4 meters above  predictable prey pathways, thus exploiting prey from a larger area.
lynx_hunting2
Lynx waiting in ambush for prey to pass underneith his hide

Another factor that presumably plays a role in the choice of housing spots is the presence of comfortable dry shelters from rain and mosquitoes. As stated above in relation to their hunting behaviour, sitting or lying on a height offers them protection for mosquitoes. However, in wet weather they probably prefer dry shelters.

Furthermore, for lynx mothers during spring and early summer, the availability of denning possibilities might determine their choice of housing spot.

Our (preliminary) conclusion is that the small size and the location of the warm season housing spots is mainly the result of hunting behaviour as a response to prey predictability and efficiency of ambush hunting from a height. In winter, presence of suitable habitats for mating seems to play an important role in the choice of the housing spots.

Both mating behaviour and hunting behaviour (with both ground based ambush hunting and stalking) result in the still patched structure of the winter home ranges. However, both the housing areas and the home-ranges itself are considerably larger in the cold season. An explanatory hypothesis:

  • in the cold season, prey distribution and movements differ from the warm season, and the warm-season hunting hides are mostly not effective anymore. In winter, prey use different pathways that are less predictable. Their locations and trajectories are strongly influenced by weather (snow) conditions. It also depends on the first individuals creating the pathways, as they are soon followed by others. Moreover, after each next heavy snowfall, the pathway trajectories are changed considerably.
  • low temperatures and snow on inclined trees, trunks and branches are unsuitable circumstances for ambush hunting from a height (high energetic cost and uncomfortable stay) and without foliage, lynxes are less concealed for their prey.
  • the gradual disappearance of mosquitos in autumn stimulates ground-based hunting (both waiting and stalking)
  • in summer, hunting is easier with access to plenty of young and other voulnerable prey (e.g. mothers raising their offspring). Survival in winter demands more efforts and a larger living area. In winter there are still places with prey concentrations, but these are changeable and their location depend on dynamic weather conditions. At the same time, efficient mating requires a larger territory (access to several mates). In winter, both the use of a larger home range (not limited to small housing spots) to provide in their food demands, and preparations for mating season demand a lot of  territory-wide marking. This need for intensive and extended marking matches perfectly with the stalking-hunting mode in winter, but not with long waiting for prey during ambush hunts.
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In summer more voulnerable prey are available for lynxes

 

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