A review of the diet of Rusa Deer Cervus timorensis russa in New Caledonia: Are the endemic plants defenceless against this introduced, eruptive ruminant?

Abstract

Rusa Deer Cervus timorensis russa was introduced to New Caledonia in 1870 from Java, and has colonized the main island of Grande Terre, where it is found in virtually all the terrestrial biotopes. Despite its abundance and its socio-economic importance for New Caledonians, little is known about the diets of the wild deer populations living in contact with native vegetation which has a high degree of endemism and which, until recently, evolved without ruminant herbivores. We collected information on the diet of Rusa Deer in New Caledonia from published and unpublished reports, a questionnaire addressed to experts and preliminary data from browse-surveys. All sources of information suggested that wild Rusa Deer in New Caledonia is a mixed-feeder, and the list of plants consumed included 25 grasses, 15 forbs, 26 trees/shrubs and 12 vines and ferns. Nearly half (49%) of the plants identified as principal and preferred foods were introduced species. Physical defences (spines and thorns) did not seem to deter deer. It is remarkable that many of the avoided plants were native species (56% of the avoided species). Further research is required to confirm these results, but they are relevant to the evolution of plant/herbivore interactions and to the management of deer populations for conservation perspectives in island ecosystems.