Marking activity of the Kamchatka brown bear (Ursus arctos piscator)

1. What they did

Brown bears leave marks on trees and other objects, and these marks are thought to be a way bears communicate with each other: about where they are, their social status, and finding mates during the rut. This study describes how brown bears mark in the Kronotsky Reserve on the Kamchatka Peninsula, Russia.

• Describing marked trees. In May 2004 and June 2005, the author searched a 3 km by 2.5 km stretch of the Valley of Geysers and described every tree with bear marks (203 trees) using a set protocol. For each tree he recorded its position with a Global Positioning System (GPS) device, its place in the landscape (ridge, terrace or floodplain) and whether it stood on a trail; the tree species, whether alive, trunk diameter and any tilt; and each type of mark: rubbing (hair, polished, dirty or greasy bark), bites, claw scuffs, and broken or bitten branches. He separated this year’s fresh marks from old ones, measured the height of bites and scuffs and the size of bite patches, and noted track marks, rolling places, urine and scat near the trees.
• Measuring track marks. Bears often walk to a marking tree with a stiff, stamping gait that leaves deep footprint holes. He measured these “mark tracks”: their length, the number of holes, hole size and the distance between holes.
• Watching bears. From 2002 to 2005 he watched bears marking in four river valleys and counted marked trees per kilometre of bear trail. Near the Kronotskaya River he also watched bears feeding on spawning salmon for over 216 hours.

2. What they found

The trees

• Most marked trees (186 of 203, 91.6%) were stone birches; the rest were 13 willows and 4 alders. All were alive.
• The average trunk diameter was 24 cm (from 3 to 85 cm); 60.6% were 11 to 30 cm across.
• 39 trees (19.2%) were tilted. Tilted trees near a trail mostly leaned toward it (89.5%), and bears marked them mostly on the trail side (79%) and on the underside of the lean (76%).

The marks

• Rubbing was found on 187 trees (92.1%), from ground level up to 207 cm. Most had both fresh and old rubbing.
• Bites or claw scuffs were found on 167 trees (82.3%). The highest damage on a tree was on average about 198 cm above the ground (105 to 270 cm). Bites were rectangular patches where bark was stripped with the teeth, often leaving tooth marks in the wood. On birch, claw scuffs were usually just scratches, because the bark is thick and hard to strip.
• Six trees had bitten or broken branches, and two willows had broken trunks.
• In June 2004, two neighbouring birches had fresh round urine marks at 103 cm, with a sharp smell, probably from one bear.
• Four rolling places and scat under two trees were found near marked trees.
• 21 trees (10.3%) were marked intensively, with many marks over many years.

Mark tracks

• Mark tracks led to 53.7% of the marked trees, on bare ground and on hard snow, usually from both sides along the trail.
• The longest ran about 300 m along a ridge trail and linked seven marked trees; the shortest was 364 cm long with five holes. Some led to bear bathing places.
• Holes were on average 77.6 cm apart, about 39 cm long and 25 cm wide, and up to 5 cm deep. They were larger than the bears’ ordinary overlapping footprints (about 30 by 19 cm). On some trails the same holes were reused and refreshed every year.

Where the marks were

• 180 trees (88.7%) were on ridges, mostly watershed ridges; marked trees were found only between 270 and 380 m.
• 161 trees (79.3%) stood on trails: 116 on bear trails and 45 on other animal and human trails. In five cases a trail seemed to bend specifically to reach a tree.
• Marking reached up to 40 trees per km of trail. Groups of marked trees within 5 m of each other were common: 25 groups, holding 32% of the trees.
• The density of marked trees in the Valley of Geysers was 27.1 per km², far higher than in the wider river valleys (0.4 and 1.1 trees per km on two routes). On one Khriukina River trail, bears had marked 9 of 12 suitable birches.
• Bears also marked alder bushes, wooden huts and buildings (especially rarely visited ones), poles on the treeless seashore, metal oil barrels and helipads.

Behaviour and season

• Bears sniffed a tree, then turned and rubbed their back, neck and head against it, standing or sitting; some hugged the trunk and rubbed with their chest and neck. They sometimes bit the trunk and more rarely clawed it. They walked to and from the tree with the stiff stamping gait, and some bears did the same when they met people.
• Many bears used the same trees. Bears staying long in the valley revisited particular trees and refreshed their marks. In the Valley of Geysers, only adult males were seen marking trees.
• Marking peaked in May and June, the mating season. At other times bears mostly just rubbed; on the seashore they rubbed and bit a wooden pole all summer and into autumn.
• Along salmon rivers, young bears and females also rubbed on trees, but rubbing took only 16 minutes of more than 216 hours of observation (0.1%).
• Bears of all ages were drawn to kerosene spilled on a helipad; a mother and cub rolled in it for hours each morning.

3. What they concluded

• Marking is an important part of how brown bears communicate in Kamchatka, as elsewhere in their range, and trees are the main objects marked.
• The typical marked tree in the Valley of Geysers is a live stone birch, 10 to 30 cm across, beside a trail, with a mix of rubbing, bites and scuffs on the side facing the trail, mark tracks beneath it, and used for many years.
• Bears seem to prefer thicker trees, and trees that lean toward the trail. Rubbing is more common than biting or scuffing, which are not essential parts of marking.
• Some low bites (40 to 100 cm) may be for feeding on birch sap rather than marking.
• Marked trees cluster on ridges because steep, overgrown valleys leave ridges as the easiest routes. Tracks in snow suggest bears know where marked trees are and may leave their route to reach them.
• The high density of marks reflects the many bears that gather in the Valley of Geysers in spring for the rut and early plants. Marking by females, young bears and cubs at salmon rivers or oil spills may be comfort behaviour rather than communication.

4. How tracking was or was not used

The whole study rests on reading bear signs. The author recorded and aged marks on trees (hair and polished bark from rubbing, tooth marks from bites, claw scratches, broken branches), separating this year’s fresh marks from older ones. He also recorded and measured the stamped footprint holes of mark tracks, on the ground and in snow, and compared them with ordinary bear footprints; noted urine marks, scat and rolling places; and mapped marked trees against bear, animal and human trails. Tracks in snow were used to suggest that bears approach marked trees directly. No trailing of individual bears is reported.

5. Tracker or observer certification

Not reported. The paper does not say who identified and aged the signs. Field assistance from J. Paczkowski, V.V. Zhakov and V.A. Zlotnikov is acknowledged. The author notes that he judged mark intensity in both this study and an earlier one in Primorsky Krai, which makes those two comparable.

6. Other technologies, skills or innovations

• A handheld GPS device to map each marked tree.
• A standard protocol for describing marked trees and mark tracks.

7. Implications for conservation (from the paper)

• The frequency, distribution and features of bear marking in the Valley of Geysers can serve as a baseline for Kamchatka brown bears. Comparing them with areas under more human pressure could reveal disruption to bears’ social structure and the health of the population.
• Bear marking activity and bear numbers could be indicators of human impact on the Valley of Geysers, which is a tourist destination.
• In May and June, the peak of marking and the mating season, the author recommends that bears be kept as separate as possible from human disturbance.
• Bears may come to the Valley of Geysers from beyond the protected area.