Use of a seaweed habitat by red deer (Cervus elaphus L.)

The use of a seaweed habitat by red deer Cervus elaphus L. on the Isle of R um, Scotland, was examined in detail. New information is provided on diet s election, timing of seaweed use relative to tides, interindividual differen ces in seaweed use, and sex differences in site use within the seaweed habi tat ('site segregation'). Interestingly, seaweed use by adult males and fem ales was closely correlated to that of their mothers. This implies that dee r 'learn' early in life to include seaweed into their diet. Formerly, it ha s been suggested that male inferiority in indirect competitive ability rela tive to females causes site segregation in dimorphic ungulates ('indirect c ompetition hypothesis'). The observed pattern of site segregation within th e seaweed habitat was used to test the hypothesis, which predicts that male s should be found at sites where they can achieve higher intake rates, but where forage quality is lower than at female sites. With respect to seaweed use, the hypothesis further predicts that segregation should be lower with in the seaweed habitat than within terrestrial vegetation communities, and that males should time seaweed use earlier (relative to the tide) than fema les. This is because seaweed availability is more subject to tidal rhythm t han to indirect competition in comparison to terrestrial habitats. Males an d females used different bays, and within bays they used different fraction s of seaweed. However, male-preferred sites did not yield higher intake rat es and were not of lower forage quality than sites preferred by females. Mo reover, segregation was not lower within the seaweed habitat than within te rrestrial vegetation communities, and males did not time their seaweed use earlier relative to the tide than did females. The indirect competition hyp othesis could not explain the observed pattern of site segregation. Other f actors, such as sex differences in sheltering or anti-predator behaviour, o r social harassment, could be responsible instead.