I've seen them by day, and during dusk/dawn. I think in general they are cathemeral, with only the peak activity periods differing by season, location, etc.
Just a quick update: Walkabout Creek's last platypus is no longer at the facility and hasn't been for a few months. I wasn't able to confirm whether he died or moved to another collection. Lone Pine's two males were alive and well two days ago during my visit by the way. 22-year-old Barak is still going strong and was as sprightly as ever catching his yabbies, putting on a show for the small audience present.
Not sure how true this is, but according to this article that I read many years back - Platypus are incredibly expensive to feed. Depending on the interpretation of the words in this article, a close second only to the elephants! This may be a major factor in why more (Australian zoos) don't keep them. No Cookies | Herald Sun
I remember seeing a black and white pic taken years ago of David Fleay tending a earth worm farm they had going at his park as part of their diet. I believe that yabbies were also high on the menu then.
Yep at Healesville they feed their Platypuses yabbies. I’ve never heard of Earthworms though, that’s interesting. I think they also feed them mealworms.
Elephants aren't that expensive to feed. It's just bulk amounts. Species (like platypus) where the diet is fiddly is time-heavy. Numbats being fed on live termites (they are also kept on a special custard mix, but need the insect's protein during breeding) takes alot of time to harvest, manage, weigh out etc. Koalas need fresh eucalyptus branches of only a certain few species. If a zoo doesn't have their own trees planted, then staff need to go out and regularly cut. Fridges need to keep the branches fresh. Having worked with both species I can tell you they are both alot of effort!