Harming an animal species causes that animal 's population to decrease.
Today, the pink flamingo is included on the endangered species list.
Harming pink flamingoes causes their population to decrease.
What causes pink flamingos' population to decrease?
  * replenishing their habitats
  * drought
  * harming them
  * hypothyroidism
  * helping them
  * influenza
  * feeding them
  * Pesticides