This will probably hack off a few people but it's 4:06 am and I don't rightly care at the moment. I just wanted to point out when you sleep--humans and animals alike your heart continues to beat, you breathe and you live. Calling it "put to sleep" of PTS is just ridiculously childish. Whenever you end the life of an animal by giving it drugs to stop it from living you are killing it. That's just the plain and simple truth. I know we call it put to sleep to ease our conscience--but come up let's man up and grow some balls about the phrase. Ending the life of anything is not "putting it to sleep"
I think this is a two-fold issue. One is euthanising a perfectly healthy animal just because we humans decide it is not fit to live on this planet & the second is performing that last, loving act of kindness on an animal which is in pain, distress, or has reached the end of a terminal condition.
Whilst I agree with you on one level - the word euthanasia is preferable - I am going to put a slightly different twist on the term "put to sleep" - from an anthropomorphic point of view (which is what we humans use constantly).
Anyone who has been anaesthetised knows that as far as you are concerned you are "put to sleep". The drugs are administered & for you, the patient, you effectively "go to sleep" i.e. are reduced to a level of unconsciousness from which you then (hopefully) "wake up" after the procedure.
Taking a beloved pet to be euthanised - I don't have a problem with using the vernacular "put to sleep" because I view it as taking my companion who has reached the end of a terminal disease or condition to their final "rest". For them, they simply fall asleep under the anaesthetic & are then given a fatal dose of anaesthesia so that their heart & respiratory systems fail. They "fall alseep" & know nothing more - it is us humans who have a problem with it. I genuinely find it a privilege (although an excrituatingly painful one at times) to be able to provide for them that final act of kindness & compassion.
If it helps humans feel a sense of peace in that kind of situation then I think using "PTS" as a phrase is wholly acceptable.
The first scenario - as is being discussed here with Tilly? Absolutely not. It's not even euthanasia (the original Greek means "A good death") .......... & I'll leave my thoughts there.
Going back to whales in captivity - dolphins & whales use sonar to communicate - the tanks, not matter how large they seem, distort those sonar signals & the constant noise from humans (construction work, fireworks, banging on the glass etc) must have an impact on the animals - I wonder if anyone has considered that sensory deprivation & over-stimulation are used as forms of torture .......... something else to think about perhaps.