When did animals begin to die?

When did animals begin to die? Did animals begin slowly dying at the time of the fall of Adam and Eve or had it happened earlier at the fall of Satan, which may be what Romans 8:20 is hinting at? > For the creature was made subject to vanity, not willingly, but by > reason of him who hath subjected it (Rom 8:20) Were animals already dying when God gave humans to have dominion over them in Gen. 1:28?: > And God blessed them, and God said unto them, Be fruitful, and > multiply, and replenish the earth, and subdue it: and have dominion > over the fish of the sea, and over the fowl of the air, and over every > living thing that moveth upon the earth. (Gen. 1:28, KJV) Or were animals originally created by God as already dying? What do the Roman Catholic Church, the Eastern Orthodox Church, and the main-stream Protestants -- that is, those Protestants who pray to Jesus Christ in their prayers -- officially teach regarding this matter? EDIT 4: Following one remark in comments (stating that senescence by definition is not only the process of aging, but also the process of maturing that precedes the process of aging) decided to switch to "dying" again; EDIT 3: Following a suggestion in the comments, rephrased the question as "When did senescence enter the animal kingdom?" EDIT 2: Originally I used the term "mortal" in my question, but since the word "mortal" may mean only "being able to be killed" (see sequoia trees example in the EDIT 1 or Adam before his fall), I decided to switch to "dying". EDIT 1: By "dying" or "already dying" I mean the very state, in which all animals are now: each species is born, lives a certain number of years, gets old and then dies. This is different from being able to be killed, yet not having the process of dying taking place within (consider sequoia trees - some of them don't die by themselves, but can be killed by, say, fire or being cut)