Damage to saplings by red deer (Cervus elaphus): effect of foliage height and structure

Red deer cause heavy damage to forest production, hence the need to better understand what determines their dietary choices. Deer are selective herbivores. According to the optimal foraging theory (OFT), they should select foods that maximise their net rate of energy gain. For a given nutritional quality, we predict that plant architecture and height should affect deer feeding preferences through intake rate variations. In the first experiment, 12 tame red deer with shoulder height (SH) ranging from 82 to 105 cm were individually offered fresh bunches of Salix caprea at seven heights regularly spaced from 25 to 205 cm. Animals preferred bunches at 85 and 115 cm height (29 and 32% of feeding time). There was a positive relationship between average consumption height (CH) and animal shoulder height (CH=0.99×SH; r2=0.43; P<0.05) but intake rate did not change with consumption height. In the second experiment, 10 fresh bunches of Quercus pedunculata were offered on three wooden structures, resembling a bushy topped (BT), a normal (N) and a five-shoot (FS) oak sapling. For each structure, average bunch height was set at preferred consumption height. Five tame hinds were observed during individual cafeteria trials (double- then triple-choice). Intake rate was slightly higher for FS than for the other structures (FS=23.7 g DM/min, N=22.3 g DM/min and BT=22.0 g DM/min). Preferences were expressed as the proportion of feeding time during the first min of test. In the double-choice trials, preference was higher for FS relative to BT (61%–39%), and for N relative to BT (62%–38%), but similar between FS and N (57%–43%). In the triple-choice trials, preference for FS (44%), N (24%) and BT (32%) differed from 33%–33%–33%. In both trials, there was thus a slight preference for FS, i.e. for the structure where all bunches were widely spaced and at the hinds’ preferred height. Foliage height and, to a lesser extent, structure of saplings thus affect the feeding preferences of red deer. These results can contribute to improving management practices to limit deer damages to commercial plantations.

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