Mammalian Conservation Notes

Mammalian conservation

INVASIVES

* 4 ways a newcomer may impact local biodiversity:

* Predation

* Easiest to detect and quantify

* Greatest threat to natives

* E.g. decline of water vole (Arvicola terrestris) attributed to accidental introduction of American mink (escaped from fur industry); impact also exacerbated by agricultural conversion (loss of good quality riparian habitats)

* Water vole reintroduction projects assessed relative impacts of mink predation and habitat quality on survival of released water voles mink control most important determinant of success; where control successful, habitat quality determined survival rates and population densities (grazing right up to water’s edge was detrimental to water vole survival rates)

* Competition for resources

* Different and subtle mechanisms

* Extinctions rarely entirely attributed to competition by introduced species

* 2 forms: direct ‘interference’ competition (individuals interacting with each other) and indirect ‘exploitation’ competition (mediated by another species, e.g. shared food resource)

* American mink has also affected European mink- interact aggressively and potentially compete for food; both occupy same niche; American mink larger and more adept swimmer generally dominant; European mink is one of Europe’s most threatened mammals

* Intra-guild competition may actually be beneficial to recovery of water vole

* Hybridization with natives

* Interbreeding; potential to eradicate native species

* May occur when geographical boundaries between populations are eliminated by moving species or physically (e.g. bridges in Bhutan golden and capped langurs can now cross/mix and interbreed)

* Carriers of disease

* Indirect, through parasite species

* Species lacking exposure to introduced diseases, or lacking time/opportunity to adapt...