Respuesta :

One way this could have happened is something in their own ecosystem which threw off the food chain. They most likely migrated to a new ecosystem and invaded it to survive and get energy.

Answer:

A species of rats entered a habitat stowed away in a train.=unintentional introduction  

A man added invasive water hyacinths to beautify his private lake.=intentional introduction  

A flood prompted many aquatic species to inhabit a new area.=loss of habitat