Deer are omnivorous opportunists and will feed catholically on grasses, heather, lichen, shoots, bark, leaves, herbs, rushes, buds, nuts, fungi, fruit and berries; even holly and bramble. They are typically mixed concentrate feeders, which means they select young shoots, young foliage, fruits and other high quality foods from which they can extract bone-building nutrients; “mixed” comes from their ability to switch between grazing and browsing. Muntjac appear particularly partial to ivy and the wild arum known as lords and ladies (Arum maculatum). Carnivorous tendencies have also been documented in some species, perhaps most notably in Red deer which made it into the 2007 Guinness Book of Records under the unenviable title of “Most bloodthirsty ungulate”! The type of food consumed depends as much on location and season as on species.
Along with the more customary items in the diet, a range of inedible objects have also been recovered from deer digestive tracts; these include polythene bags, balloons, string and even a pair of disposable underwear. Unfortunately, these kinds of objects can easily get stuck and cause a blockage. In her 1991 book Deer, Norma Chapman notes that a study of more than 80 Fallow deer stomachs collected in Essex found that they all contained at least one foreign object.