Hello and welcome
I'll start with a bit of history of Uk hamster owners:
I think many owners have found, just from experience, that the larger the cage (over a certain size), the happier the hamster is. Providing there is sufficient enrichment. A large cage without much in it is not good for a hamster as they could feel stressed and exposed and unable to have normal behaviours such as burrowing, foraging and having a dark place to retreat to.
Personally I have been using 100cm cages for Syrian hamsters for about 9 years now. And most Syrian owners recognised that 100 x 50 cages, or larger, meant the hamster didn't bar climb or bar chew - they were more content in their environment (providing they weren't cleaned out every day which would be stressful whatever cage they were in).
This was at a time when the Uk "minimum size" was about 80 x 50cm - an old RSPCA minimum which later was removed with no actual minimum size quoted, but within the hamster world it was still widely accepted that 80 x 50cm was the absolute minimum (for a Syrian) and about 70 x 40cm for a dwarf (although most dwarf owners found 80 x 50 was better for a dwarf).
It was also at a time when 100 x 50 or 100 x 54 cages were easily and cheaply available from Zooplus (before the pandemic and brexit) and those who did start with an 80 x 50 cage for a Syrian, even if tall enough (eg the Alaska cage) quickly found it wasn't really enough and upgraded to 100cm x 50cm cages.
The German minimum welfare cage size has been abiut 100 x 50 x 50 for as long as I can remember which is why so many cages that size were available from Germany (from Zooplus and also a wider variety from Amazon.de).
So possibly the most popular cages for many years were the Hamster Heaven (in the Uk - minimum 80 x 50) without the tubes and penthouse, the Barney cage (100 x 54 x 46) and the Alexander cage (100 x 50 x 50).
Tanks were always prohibitively expensive in the Uk but more popular in the Us where they could be obtained much cheaper, and the only barred cages accessible in the US were the 80 x 50 Hamster Heaven, the 80 x 50 Savic Mickey 2XL, and, at one time, The Marchioro Goran and Kevin (both about 84 x 48 but taller at 46cm). The Goran was 1cm bar spacing and the Kevin was narrow 7mm bar spacing.
The biggest complaint amongst hamster owners about 100cm cages available, was they had small doors on the front - unlike the Hamster Heaven and Mickey 2XL which had a large front opening door. So requests were made to Savic to make a 100cm x 50cm version of the Hamster Heaven
And this materialised - it became available around 2016? And is the Savic Plaza 100 cage. It quickly became the most popular cage for Syrian hamsters - among owners who knew Syrians needed larger cages, despite there being no official minimum cage size in the Uk any more.
Personally I eventually sold my Barney cage (the small front doors were no good for a shy hamster and it meant having to take the bars off which was cumbersome, and replaced that, and my Mickey 2X:L with two Savic Plaza cages.
The Savic Plaza 100 wasn't perfect - it was less deep than the Barney cage, but aside from that it was the "near perfect" cage for most Syrian Hamster owners.
There was also no real minimum recommended bedding depth in the Uk at that time, but people recognised that 6" (ie filling the cage base) was a good amount of bedding for a hamster to burrow down and bury hoards under their nests and they seemed happy with that.
There was an awareness that in Germany, much deeper bedding was used, in tanks, for hamsters to dig their own tunnels. But most owners in the Uk found their hamsters were happy with 6" of bedding. Most dwarf owners continued to use 80 x 50 (some would use 100 x 50, as I did with my robo eventually) but it meant quite a lot of adaptation to make the cages safe from fall risks.
Many owners wanted cages bigger than 100 x 50 however, and there were no barred cages available of that size, unless you were prepared to mesh a guinea pig cage (which some brave people did!) or unless you spent a lot of money on the tank style Living World Eco Habitat (which came in much bigger sizes, but also needed some diy to mesh the roof and also didn't have front opening access (some people adapted them with diy to have a front door).
Large front access was seen as a good way to allow a hamster to come out, without stressing them, and a good way of interacting with the hamster on their level. ie it was good for taming and interaction and also for spot cleaning without having to partly dismantle the cage (which can also stress the hamster).
There was a constant desire to find the perfect cage. For many the Savic Plaza 100, when it came out, was that near perfect cage. This became particularly so when the pandemic came along in 2020. And Brexit. Suddenly nothing was available from Germany any more. There were hardly any hamster cages available at all! But Savic still shipped the Plaza 100 to the Uk (and the Hamster Heaven) and as such these became hugely popular. And about the only barred cages available, without diy. (I regretted selling my Barney cage once it was no longer available!).
In the US, a 40 gallon breeder tank (about 90 x 45 x 45) was seen as a "go to" suitable size for most species of hamster.
Studies
Hamster owners in the Uk were aware of German studies and German legal welfare minimums. Showing 100 x 50 x 50 should be the minimum size for hamsters and many people tried to persuade the RSPCA to have a new minimum cage size in line with that, but this was unsuccessful. So it largely fell upon experienced owners to spread the word and give reasons why people should use 100 x 50 cages or upgrade their cages.
The prime reason, from observation, was that - hamsters don't bar chew once the cage is 100 x 50 or larger. And that is my personal experience. There will be the occasional exception (usually female Syrians! Who often need much more space). But providing owners didn't cause stress (like have a bare set up or clean out a lot) then hamsters didn't bar chew or monkey bar.
The advantages of the barred cages were seen as - good ventilation and interaction with the hamster - which is slightly unquantifiable. However people had personal preferences - some preferred tank style cages, some preferred barred cages.
Even back as far as 2014/15, owners would put cardboard inside the bars to allow for deeper bedding as it was recognised hamsters loved deep bedding.
The RSPCA were informed of these German studies but their response was often "we do our own studies".
Some people also tried to undermine the main German study as being unreliable (I think they kept hamsters in different sized cages and observed bar chewing stopped once the cage got to 100 x 50). The criticism were that maybe it didn't allow for hamsters being close together in cages which could cause bar chewing, if they were close to another hamster. That said, the study found that hamsters in 100 x 50 cages didn't bar chew (and no doubt that was with not quite enough enrichment as well).
This was not news to Uk hamster owners who already knew that! From experience - we didn't need studies to tell us that. However trying to persuade Uk animal welfare charities to set a Uk minimum cage size proved pretty fruitless.
And it was forums, like this one, that spread the word and we tried to educate people (some members on here will remember this period and the huge effort they put into trying to educate people).
There was also a German study on bedding depth. I believe showing that hamsters with x amount of bedding (I think it was 40cm) didn't bar chew. I must admit that wasn't taken too seriously in the Uk and we couldn't imagine the feasibility or cost of 40cm of bedding. Or find it necesssary when hamsters were happy in 100 cm cages with 6" or slightly over of bedding, or a deeper area or digging box. We just thought the Germans had different standards (and commonly it was said - well the Germans have bigger houses and are better off!). Which is perhaps embarrassing to admit now! But that was the general thought.
However people in the US, who mostly used tanks, did tend to use deeper bedding - 30cm or so.
The general view in the Uk was - there are different types of enrichment. What the barred cages lost out on with bedding depth, they made up for with being able to creat more enirchment by attaching things to the bars and roof and provide an interesting environment.
To be continued!......
But likewise there used to be a view that an enclosure or cage without a front door meant a hamster was "behind a wall" without real human interaction or bonding.
