Should suffering endangered animals be euthanized?

This is an opinion question and there are strong views about this.

One viewpoint is that it is inhumane to allow an animal to continue suffering without the hope of recovery, therefore the animal should be euthanized. The fact the animal is of an endangered species is irrelevant.

Another viewpoint is the animal may be able to recover, which would allow the animal to re-enter the breeding population and help the species recover. The suffering here is secondary to the usefulness of the animal in terms of the overall species.

My opinion is, it depends on three key factors: is the animal under the direct care and management of humans, is the animal a valuable or proven breeding animal, and what is the prognosis for recovery to breeding. If the animal is in the wild, I am comfortable with letting the animal find its own fate, be it death, disease or recovery - this is the natural world and it isn't pretty or nice. If the animal is under human care and management, however, then humans have to accept the ethical obligation to continue that same care and management.

Second, if the animal is past breeding age, has reproductive abnormalities or is effectively sterile, there is no value to the species to keep this animal alive if it is suffering. However, if the animal is a proven successful breeder, premature euthanasia may set back the recovery of the species as a whole.

Third, what is the animal suffering from? Certain injuries and diseases can be easily treated and the animal can be expected to make a fairly good recovery from them. Other injuries and diseases are basically incurable and untreatable, and the animal is likely to suffer until it dies.

For a wild animal just being observed by humans in its own environment, I don't think we should euthanize. For a captive animal, if the animal is not a breeder or does not have a good prognosis, I believe it should be euthanized.