Context

Dry forest has evolved for millions of years in the absence of land mammals, the only NC native mammals being Chiropterae (flying foxes).

From an evolutionary point of view, the impact of introduced mammals on the ecosystem is relatively recent.

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Rusa deer on slopes covered in Heteropogon contortus (Poya), photo M. de Garine-Wichatitski

Introduction of herbivores and omnivores has followed human settlement of the islands.
Rodents were first introduced by Melanesian populations (Rattus exulans), then by Europeans (R. rattus, R. norvegicus, Mus. Musculus). Feral pigs are assumed to be descended from pigs imported by Captain Cook at the end of the 18th century.
Domestic ruminant (cattle and goats) and wild ungulate (Rusa deer, Cervus timorensis russa) were introduced during the 19th century.

Feral pigs are found in dry forest,
photo M. de Garine-Wichatitsky

In the absence of “co-evolution” between dry forest native flora and introduced mammals, survival and/or regeneration of dry forest native plants is highly at risk, since these plants have not developed protection or tolerance mechanisms to herbivores (as is the case, for example in African savannahs).

Impact of introduced ungulates

Sclerophyll forest in New-Caledonia has greatly declined owing to a number of factors : climate, bushfires, clear-cutting, and the impact of introduced species.

Cattle (Tiéa),
photo M. de Garine-Wichatitsky

It is not known how far these species (rodents, feral pigs or ruminants) have contributed to the general reduction of areas previously covered by dry forest.
Nonetheless, the vast majority of residual forest patches are situated in current cattle-breeding zones or suffer the impact of wild ungulates (rusa deer and feral pigs)


It is possible to enclose selected land plots for protection, but the high cost of fencing means that only limited areas can be protected in this manner.

Sustainable conservation of New Caledonian dry forest cannot be ensured by the artificial preservation of a few sanctuaries . It will only be achieved through a better understanding of the negative impact of ungulates and appropriate handling of these constraints.

Understanding and measuring the impact of ungulates on dry forest is a prerequisite to establishing a management program to maintain and restore sclerophyll forests vegetation.
A study is being carried out to evaluate the effect of Rusa deer on natural environment (impact of browsing and of antler rubbing by rutting males). This study aims to establish appropriate methods to survey wild deer populations and to assess damage.

Expected results of this study are :
- to identify endemic plants most vulnerable to ruminants
- to select native plants with a natural resistance to ruminants (these will then be used in reforestation programmes)
- to define (if applicable) deer threshold densities compatible with dry forest regeneration.