If an invasive species preys on native species, spreads widely and becomes dominant, should it not become extinct soon enough because of a lack of food?

  • $\begingroup$ Afaik starvation and diseases usually just reduces the population of a species, and does not necessary wipes it out. Btw. interesting question, by Ambrosia artemisiifolia ppl claim that it disappears from a territory after 5-10 years. $\endgroup$ – inf3rno Nov 5 '14 at 13:58
  • $\begingroup$ Practical experience says they survive...like "Eichhornia crassipes" was introduced in my country long time (about 100 years) ago...& still is going strong...also a species called " carrot grass" was accidentally introduced about 30-40 years ago, from food-grain given as an aid from U.S.A..& it now threatens to occupy vast swathes of green pasture....both are showing no sign of decline... $\endgroup$ – souvik bhattacharya Nov 5 '14 at 19:03
  • $\begingroup$ Wild boars and wild horses were introduced to the Americas in the early 1500's and have been alive ever since. I don't know if their populations ever increased so much to cause problems with the native ecosystem though. $\endgroup$ – user137 Dec 5 '14 at 20:55

This potentially depends on what species you are referring to.

In the case of plants, photosynthesis is used to as their source of energy, so will never run out of food as such. Assuming the conditions are favourable in terms of water and temperature (likely, otherwise the species wouldn't have flourished in the first place) and they stay that way, the only limiting factor is going to be nutrients in the soil. These are returned to the soil when the plant dies, so this is fairly self-limiting, when there's not enough then plants will die and the nutrients will return to the soil.

Animals face a slightly different situation, in that they need to eat to survive. As such, if the population that was introduced was large enough to eat all the prey (whether plants or other animals) in the area and carnivorous animals didn't partake in cannibalism even when times were tough, then the animal may die out.

In general however, predator and prey regulate fairly effectively, a decrease in prey causes a decrease in food availability which leads to a decline in predators. This allows an increase in prey, which gives a higher availability of food to predators so their numbers increase. This causes a decrease in prey numbers and so on. In general once an invasive species has been established, it will require intervention for it to be removed and it will not die out naturally.

  • $\begingroup$ Invasive animals generally are not introduced in large numbers...normally people bring 1 or 2 of them...but in due course they grow into huge numbers...e.g a farmer introduced only 2 pairs of rabbit in Australia..but in a short time their no. reached in the hundreds.. $\endgroup$ – souvik bhattacharya Nov 5 '14 at 19:13
  • $\begingroup$ Agreed, that was pretty much a hypothetical situation in which the OPs theory may be correct. It is not one seen in the real world. A gradual increase allows regular predator-prey cycles to take place, if there's not enough food the growth of numbers of the invasive species will slow. $\endgroup$ – Rob Mackinnon Nov 5 '14 at 20:35

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