Selection of bed-sites by roe deer Capreolus capreolus fawns in a boreal forest landscape

1. What they did

Newborn hoofed animals often die from predation, starvation or cold in their first weeks. Roe deer fawns are “hiders”: for their first four weeks they spend up to 80% of their time lying still in a bed-site while their mother feeds 50 to 1,000 m away. A well-hidden bed is their main protection against searching predators. Earlier studies of roe deer fawn bed-sites were done where predators of fawns were almost absent. This study was in southeastern Norway, where red foxes and Eurasian lynx were present.

• Finding the fawns. Adult females were caught in box traps at winter feeding sites and fitted with radio-collars. In June, the researchers checked them for signs of having given birth, then searched for the fawns and fitted each with a small radio-collar. They followed 19 fawns from seven mothers.
• Recording bed-sites. Each fawn was located about once a day and approached until it was seen, until it was 2 to 3 weeks old and began to run off. The bed-site was marked and examined the next day, once the fawn had moved on. After fawns began to run, the researchers only came close enough to see which habitat they were in.
• Measuring cover. At each bed-site and at a random site 50 m to the north, they recorded habitat type and forest age class, the height of the tallest vegetation, the distance to the nearest tree, its trunk diameter and the height of its lowest branch, and canopy cover. They placed a model fawn in the bed and measured how far away it disappeared from view at fox height (30 cm), from four directions. They recorded the main ground cover in a 50 x 50 cm square.
• Habitat use and availability. For each family group’s home range they compared the habitats used for beds with the habitats available, read from forest maps. They estimated the availability of forest age classes by walking transects at two sites.

2. What they found

Hiding at the bed-site

• In the forest, fawns chose bed-sites with taller vegetation (median 60 cm versus 38 cm at random sites), lower visibility (median 145 cm versus 250 cm) and more canopy cover (median 78% versus 58%) than nearby random sites.
• They did not choose sites closer to trees, or under trees with lower branches or thicker trunks.
• In the fields, where cover is even, bed-sites did not differ from random sites.
• Bed-sites in fields gave better cover than bed-sites in the forest: taller vegetation and lower visibility.
• Canopy cover increased with forest age, but vegetation height and visibility at bed-sites did not differ between forest age classes.

Ground cover

• Fallen branches and tree trunks were chosen early in the season, when other plants had not grown much.
• Later, as herbs covered more of the ground (from 11% to 37% at random sites), the preference for wood disappeared, grasses and low shrubs were avoided, and bare low ground cover (lichens, moss, leaf litter, soil) was chosen.
• No selection was found for bushes or herbs.

Main habitat types

• Fawns bedded in almost every habitat in their home ranges: forest, fields (pasture and grain) and bogs. Only gardens and roads were not used.
• Forest was preferred over fields and other habitats, which were used about equally.
• Even so, fields and bogs were used often. One family group (#58) had most of its bed-sites (78%) in a field.
• All forest age classes were used, from recent clearcuts to over-mature stands, in roughly the same proportions as they were available (31%, 24%, 25% and 20% use for classes I, II, III and IV-V, against 27%, 19%, 29% and 26% availability).
• Three fawns died during the study: two were killed by red foxes and one by a domestic dog.

3. What they concluded

• Where predators are present, roe deer fawns pick bed-sites that hide them better than expected, mainly through dense ground vegetation rather than trees and bushes.
• The soft low ground cover at the bed itself probably gives comfort and lets fawns lie low, getting the most from the surrounding plants.
• Fields hide a lying fawn well from fox height but give no cover to the mother. Predators may watch the mother approach and use her to find the fawn, which may be why fields were not favoured.
• Unlike a study in France, where fawns strongly chose forest openings, fawns here used all forest ages. The authors link this to the richer understory of Scandinavian conifer forests compared with European deciduous forests.
• Because fawns could hide well almost everywhere, all habitats may simply have been equally good. Another possibility, not exclusive of the first, is that spreading beds across all habitats forces a predator to search everywhere, raising the cost of hunting fawns.

6. Other technologies, skills or innovations

• Radio-collars from Televilt International: 30 g transmitters on elastic collars for newborn fawns, swapped for 100 g transmitters on expanding collars at 10 days old.
• A “model” fawn placed in each bed to measure from what distance it was hidden at fox height.
• A flat mirror with a grid to measure canopy cover from directly above the bed-site.

7. Implications for conservation (from the paper)

• If fawns depended on very specific habitat for bed-sites, keeping that habitat available would matter when planning forestry or grazing. In this study fawns used all forest ages and hid well in each, so the authors judge the effect of forest age on hiding to be small.