Hi and welcome
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Chum is adorable! He has such a sweet, cheeky look about him and I have a particular fondness for cream coloured hamsters
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I've had two before and both were completely maverick haha. I'm not saying all cream coloured hamsters are, but both mine were similar personalities to what you describe and great fun
Re the toilet - it needs to be in the right place for them to approve! Anything near his nest, he clearly didn't approve! Maybe try putting it in a corner of the cage - is it a corner litter tray? If he doesn't use it, try a different corner. The usual advice is to put it in his usual pee place - but if he's peeing in his nest ............ you can't really. It's common for baby hamsters to pee in their nest at first, but once it's had to be cleaned out a couple of times (which they don't like at all!) then they tend to get the message and pee somewhere else.
It helps to try and leave a tiny bit of the old nest behind, even if has to be removed because pee soaked - so it still smells like their nest. Maybe a dry bit even if it's a bit whiffy! The same with any hoard. If the hoard is pee'd on, that needs removing too, but try and leave a tiny bit of the old hoard that's dry, so it still smells familiar - and then add a handful of new food as well. They can start having abnormal behaviours if they have no hoard.
I had to laugh at him putting the scattered food in his food bowl
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But that is the foraging instinct - forage for it and then put it somewhere. It seems he considered his food bowl is his hoard. He maybe hasn't quite got the hang of pouching and hoarding yet
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Or, if there isn't much substrate, they can't bury the hoard (the tend to bury it under the nest) so he needed somewhere to put it
Cage: Have you seen the cages list on the home page? I'll link it below. I use the Savic Plaza cage. It can be adapted to have more bedding in - either using cardboard round the inside bars (if he doesn't chew it off!) or grass mats or perspex panels. So the bedding doesn't fall out. The Bucatstate doesn't need adapting but there is a limitation of 9" of bedding anyway or the sides bow out. And it's not that difficult to get 8" of bedding into a savic plaza if you put something inside the bars.
I just like the big front opening door on the plaza cages - for interaction with the hamster and spot cleaning, and the cages are easier to move - but that's a personal preference. I do have the perspex panels to attach to mine - but they cost extra and then it would cost about the same as the Bucatstate. But you could use grass mats or cardboard instead. I'll link a photo below of the cardboard bedding panel option - it's not that glamorous but it does the job! Unless the hamster is one who chews cardboard! Not all hamsters do, but my cream one did!
Playpen. Is it too late to send it back for a refund? If it is then it is probably ok for now, although he might just climb the sides. They always need observation all the time in a playpen anyway. There are better playpens but they're expensive. I have the Happy Henry Homes one which is good, but it costs about £50. I also have the omlet one which I prefer (without the wipe clean base) as it is so quick and easy to put up and down (as long as you don't use the plastic base which I find too fiddly - unless you leave it set up all the time somewhere).
I tend to start taming in the bathtub first though
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With a blanket down and maybe a tunnel and hide and a spare wheel if you have one. There's a whole article about taming on the home page
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The bathtub is a smaller area to start with hand taming, and then progress to a playpen.
The current saucer wheel will need changing though. It's too small for a Syrian hamster and that may be adding to his pent up energy. Plus not healthy for them to run in a saucer that's too small as they can't run in a straight line properly so they bend their backs.
They need an upright wheel for the cage that is 11" diameter or larger. My view is that a saucer is ok in a playpen, for out of cage time, providing it's a 12" one.
When you decide on a cage to upgrade to, then it might help decide on which wheel to get. They have their pros and cons and some need to stand a platform and some attach to bars.
The main difference between a tank style, like the bucatstate, and a barred cage is - with a tank style you will need to buy or make platforms for things to stand on - like a wheel, sand bath or any heavy ceramic items (or they could squash the hamster if tunnelled under). With a barred cage you can attach shelves to the bars and wheels to the bars. Although I have used the Happy Henry cloud platforms in the Plaza cage instead of shelves sometimes, because they will fit up to the edges of a barred cage with a sloping base, which most platforms won't.
As Socks Mum says, the cork granules are fine - however the listing says coco soil and the photo shows cork granules! So it depends which one you wanted.
For substrate, you don't want to be using the wood shavings really. Even if it says kiln dried and dust extracted on the packet. Pine and softwood shavings contain phenols which aren't good for hamsters long term (that is the pine smell). Kiln drying removes some of the phenols but not all of them). Also if it just says "softwood" on the packet, it could be any kind of softwood and not just pine. So it might include cedar which is a big no no for hamsters as it's very high in phenols.
Most people use alternative substrates. I personally think Kaytee clean and cozy is better than Carefresh. I use Fitch, which is recycled food grade paper and can be bought in bulk. Although it's only white. (Sometimes off white depending on the batch). Hamsters do love paper based bedding though and it holds their tunnels better plus they like it's softness. You could use more than one type of substrate though. There are others as well like Megazorb, Hemp or beech shavings or aspen (beech and aspen are hardwood so no issues with phenols). Although some people find megazorb smells funny. Beech wood shavings can be a bit hard. I find aspen dusty and spiky personally. Hemp was popular for some times (unless you have allergies!) but doesn't hold tunnels. Which is maybe why the kaytee and Fitch are more popular.
I can't wait to hear more about Chum
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He sounds like he is going to be a lot of fun