Winter bed-site selection by red deer Cervus elaphus xanthopygus and roe deer Capreolus capreolus bedfordi in forests of northeastern China

1. What they did

Red deer and roe deer share the forests of northeastern China, where winters are long and very cold and winter food is at its poorest. Where a deer chooses to lie down can help them save energy, so the researchers compared the winter beds of the two species. They expected that the smaller roe deer, which have higher energy needs for their size and digest winter browse less well, would choose more sheltered beds than red deer. They also expected night beds to be under denser canopy than day beds, and canopy cover over beds to be greatest in the coldest part of winter.

• Finding beds. In five sampling areas on Tonghe Hunting Farm, from late November to late March 1991 to 1992, a team of three walked in parallel about 100 m apart, looking for tracks in the snow. When they found a fresh trail in the early morning, they backtracked it to find the night bed and followed it forward to find the day bed. An experienced hunter judged whether tracks were fresh from the looseness and puffiness of the snow.
• Telling the species apart. Beds were identified as red deer or roe deer from the tracks, the size of the beds, whether the bed had been scraped, and the pellets.
• Measuring the site. Beds within 20 m of the first bed found counted as one bedding site, and one bed was chosen at random to represent it. They counted and measured the beds, and recorded 14 habitat features, including snow depth, distance to human disturbance, slope, canopy closure (from photographs taken straight up from each bed), ground cover (with a cover board read from 15 m), conifer composition, the nearest trees and shrubs, and browsing on nearby shrubs.

2. What they found

The beds

• All 128 roe deer beds had been scraped. None of the 75 red deer beds had.
• Red deer beds were larger and deeper than roe deer beds. Red deer night beds were longer than their day beds (about 133 cm versus 124 cm), and roe deer night beds were longer and wider than their day beds.
• The number of beds at a site (about 1.4 to 1.8) did not differ between species or between day and night.

Canopy and conifer cover

• For both species, night beds had more canopy closure than day beds: red deer 49.6% at night versus 23.5% by day, roe deer 78.5% versus 21.6%.
• At night, roe deer chose denser canopy than red deer.
• Roe deer night beds had far more conifers around them than their day beds (32.2% versus 4.3%). Red deer showed no such difference.
• Roe deer night beds had the most canopy closure in the cold mid winter (about 92%, read from the figure), more than in early or late winter. Their day beds did not change. Red deer showed no difference between mid and late winter.

Ground cover, slope and snow

• Roe deer day beds had better concealment (ground cover) than their night beds and than red deer day beds.
• Red deer bedded closer to trees at night (4.0 m) than by day (7.1 m). Roe deer showed no difference.
• For both species, most night beds were on north-facing slopes (61.6% red deer, 62.5% roe deer) and most day beds on south-facing slopes (60.8% and 57.5%).
• Red deer bedded in deeper snow than roe deer (about 21 cm versus 14 to 16 cm).
• Distance to human disturbance (about 820 to 890 m) did not differ between species or bed types.

Browsing

• Red deer browsed less around night beds (7.7% of sites) than day beds (31.8%). Roe deer showed no difference.

The analyses

• Six principal components explained 75.3% of the variation in the bed sites.
• Canopy closure, distance to the nearest tree, ground cover above 1 m, tree height and snow depth best separated day and night beds. Red deer and roe deer chose different bed sites, and roe deer differed much more between day and night beds than red deer did.

3. What they concluded

• Red deer and roe deer differ in where they bed in winter. Roe deer chose night beds with denser canopy and more conifers, and day beds with better concealment, than red deer.
• These differences reflect thermal cover and hiding cover, which may be closely linked to the different energy needs of the large-bodied red deer and the small-bodied roe deer.
• North-facing slopes usually carry the heaviest forest cover, which may explain why night beds were found there.
• Human hunting is the main predation pressure on roe deer in the area, so the dense ground cover at their day beds may be an antipredator strategy. Red deer may be more used to people, which may explain why their day and night beds did not differ in concealment.
• Bed scraping by roe deer may be a comfort and energy-saving behaviour.
• The authors caution that it is very difficult to tell whether tracks are fresh and whether a bed was used by day or by night, and that some conclusions need care because of some confusion in identifying tracks.

4. How tracking was or was not used

Tracking in snow was the core method. A team of three searched for tracks walking about 100 m apart. From a fresh trail found in the early morning, they backtracked to the night bed and trailed forward to the day bed. Freshness was judged by the looseness and puffiness of the snow in the tracks. Beds were assigned to red deer or roe deer from the tracks, the size of the bed, signs of scraping, and the pellets. Browsing on shrubs around each bed was also recorded.

5. Tracker or observer certification

Reported but not validated. An experienced hunter (described in the Discussion as having over 30 years of hunting experience) judged the freshness of tracks and helped decide whether beds were used by day or night. The hunter’s skill was not tested. Who identified the species from the beds is not stated. The authors note “some confusion in the identification of tracks”, which matters because the day and night comparison depends on these judgements.

6. Other technologies, skills or innovations

• Canopy closure measured from black and white photographs taken straight up from 0.5 m above the centre of each bed, scored on a 100-dot grid.
• A cover density board (0.3 by 2.5 m, marked in 0.5 m bands) read from 15 m in each of the four compass directions.
• Point-quarter sampling of the nearest trees and shrubs around each bed.