Using sign at power poles to document presence of bears in Greece

1. What they did

Brown bears in Greece are endangered, and the people protecting them need reliable information that can be gathered quickly. Tracks and scats were the main signs used to show where bears live, but Greek weather wears them away fast. In 2003 the researchers noticed bears marking and rubbing on wooden power poles in Grevena, northwestern Greece: more than 60% of the area’s 648 poles showed this activity, and one pole was so heavily marked that the power company had to replace it.

They set out to describe this behaviour and the signs it leaves, to compare those signs with tracks, scats and other bear signs, and to test whether pole checks could document bears elsewhere in Greece.

• Main study area. They chose 40 of the most used poles, spread across pine forest, oak forest, cultivated fields and mixed stands. They cleared all old bear signs from each pole and from 50 m around it, then wrapped each pole in a spiral of barbed wire up to about 2 m to catch hair. Every month for a year (November 2004 to October 2005) they recorded and photographed every new sign on and around the poles: hair, bite and claw marks, mud smears, tracks, scats, feeding signs and marked trees. They followed each sign until it could no longer be seen, to learn how fast each type fades. One pole could not be reached in winter and was dropped, leaving 39.
• Three more areas. In October and November 2005 they surveyed Mount Grammos, Mount Askio and the Rodopi Mountains once each, checking sets of 10 poles in a row along power lines (360 poles in all) and ageing the signs with the guidelines from the main area.

2. What they found

What bears do at the poles

• Bears sniff the base of the pole, or stand on their hind legs with their front legs against the pole and sniff at about 1.8 to 2.0 m. Video from a separate behaviour study in the area supported this.
• Mud smears were mostly at the pole base or at about 1.4 m, and were found even on poles with no other sign.
• Hair was left all around the pole up to about 1.8 m.
• Bite and claw marks were mostly at 1.0 to 1.2 m and 1.8 to 2.0 m, forming two distinct rings on heavily used poles; some were as high as 2.6 m.
• Barbed wire did not seem to put bears off.

Main study area

• 261 new bear signs: 217 (83%) came from pole behaviour (144 hair deposits, 64 bite and claw marks, 9 mud smears) and 44 (17%) were general signs nearby (32 tracks, 8 scats, 4 feeding signs and marked trees).
• Pole signs were found significantly more often per pole per survey than other signs.
• 186 hair samples were collected from the barbed wire for genetic analysis.
• Marking went on all year, peaking around the breeding season in April and May.

How long signs last

• None of the 40 tracks and scats lasted longer than 2 months.
• Mud smears usually lasted 2 to 3 months (three lasted up to 6); this depended on how hard the bear rubbed and how much rain followed.
• No hair deposit lasted more than 6 months; hair lasted longer in dry weather.
• Bite and claw marks lasted the whole year.
• From this they wrote ageing guidelines. Fresh hair (1 to 2 months) is long, curly, brownish, in locks, flexible and hard to break; older hair (3 to 6 months) is short, straight, bleached, in single strands, stiff and brittle. Fresh bite and claw marks (1 to 2 months) smell strongly of creosote, have raised wood pieces and are lighter than old marks; at 2 to 8 months the smell is medium and wood pieces lie scattered around; by 8 to 12 months there is no smell and the colour difference is fading.

Other areas

• Bears had marked 33% of poles at Mount Grammos, 30% at Mount Askio and 1% in the Rodopi Mountains.
• Of 130 recent signs (1 to 6 months old), 125 (96%) came from pole behaviour. Bite and claw marks were the most common, then hair, then mud smears.
• Pole signs were significantly more common than tracks, scats and other signs at Grammos and Askio, but not in the Rodopi Mountains.
• The bear distribution found matched the pattern from damage compensation claims.

3. What they concluded

• Bears rubbing and marking on power poles happens across Greece, in different habitats and with different levels of human activity.
• Pole signs are more common and last longer than tracks and scats, the signs mainly used to document bears in Greece.
• Preliminary genetic results suggest rubbing is mostly done by males, as in North America and Japan. Greek brown bears bite and claw poles much as American black bears do on trees, rather than rubbing like North American grizzly bears.
• Fewer marks in the Rodopi Mountains could reflect different marking behaviour in this separate eastern population, or fewer bears; this needs more study.
• Pole checks can miss bears unevenly across seasons, sexes and places, so results on where bears occur should be treated with caution, and future work should account for this.
• The approach made possible the first genetic study of brown bears in Greece and a nationwide distribution survey within one year, and may work for other bear populations.

4. How tracking was or was not used

The whole study is a tracks and signs survey. The team identified and counted bear signs on and around power poles (hair, bite and claw marks, mud smears) and nearby (tracks, scats, feeding signs and marked trees), photographed each sign and followed how it changed month by month. From this they built a guide for ageing hair and bite and claw marks, and used it to age signs in the three other areas. No trailing was reported.

5. Tracker or observer certification

Not reported. The paper does not say who found, identified and aged the signs; G. Starkie is thanked for help with data collection. The ageing guidelines and the counts rest on sign identification.

6. Other technologies, skills or innovations

• A single strand of barbed wire spiralled up each pole, a cheap way to collect bear hair for genetic analysis without capturing bears.
• A photographic record and history of marks for each pole, used to tell new signs from old.
• Remote video cameras from a separate behaviour study, giving anecdotal evidence of how bears use the poles.

7. Implications for conservation (from the paper)

• Greece lacked a permanent nationwide bear monitoring scheme, held back by limited funding, expertise and political will.
• Regular checks of power poles are cheap, indirect and need little knowledge of bear habitat, because the poles are fixed and easy to reach. Volunteers with minimal training could run them.
• Hair from poles can identify individual bears and their sex, family relationships and genetic diversity, including comparing the western and eastern populations.
• Pole checks are not a cure-all, but could become a valuable tool for brown bear conservation in Greece.