Reproduction in the wild:	no
Dispersion potential:	high
Natural habitats:	high

More on naturalization and invasiveness: Sika deer is found in dense woodland and scrub, including the thicket stages of coniferous forests and adjacent open ground. It usually prefers early seral stages over mature forests. It can also be found in estuarine reed beds and similar wet areas. Sika is increasing and expanding in several European countries. It may build up to very high local densities before expanding population's range. In Northern Scotland, there has been a rapid population expansion since the 1970s, at a rate of 3-5 km per year.

Predation / Herbivory:	high
Competition:	medium
Disease transmission:	likely
Genetic effects:	high

Nutrient cycling:	low
Physical alteration:	high
Natural successions:	likely
Food web alteration:	likely

More on impacts: Sika can build up higher densities than red dear and can cause great environmental and economic damages to forests and wetlands due to ring barking (especially in hard winters), browsing, bole-scoring, trampling, etc. Hybrids with the native congeneric red deer are fertile, and further hybridisation or back-crossing to either parental type is rapidly threatening the genetic integrity of the native species. Sika are often reported to be better competitors than native deer species (e.g. roe deer). As with other deer species, sika are a possible source of bovine turbeculosis. They also play a role in the epidemiology of the nematode Asworthius sidemi, affecting other mammal species.

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