Final answer:
The primary threats to animals include habitat destruction, overharvesting, introduction of exotic species, and climate change, with human activities being a significant underlying cause.
Step-by-step explanation:
The greatest threat to animals is habitat destruction, fueled by human population growth and unsustainable resource exploitation. Habitat loss, through deforestation and other disruptive activities, affects a significant percentage of threatened species worldwide, especially mammals. Overharvesting, the introduction of exotic species, and climate change are also major threats, contributing to biodiversity loss and the extinction of various species. Pollution and human overpopulation exacerbate these threats, leading to a decline in animal populations and loss of biodiversity.