This photo definitely has a mouse in it.
It looks like a mouse, possibly kangaroo. By the way, I also think part of the tail is missing.
Warning: if you google “kangaroo mouse” you could die of cute.
The Great Mouse Detective? Apparently the villain is called Ratigan in that movie.
FWIW, the Deer Mouse (Peromyscus Maniculatus) and her friends, the most common mouse in the wild in North America, has a hairy tail.
Of course, the photo also is 100% certainly not a Deer Mouse.
What is the most common mouse in Amsterdam?
The OP’s location gives the helpful note “I am here”. I missed earlier in the thread where they posted “Amsterdam.” So never mind.
I say rat, mainly because of the ears. Look like rat ears to me. And the tail - too thick for a mouse.
Young rat, mainly based on the size of the head.
I am highly familiar with mice, only barely familiar with rats. The proportions look all wrong for a mouse, so I’m going with young rat.
Yep. Baby rat (not necessarily a Brown rat, there’s lots of regional rat species most places) for sure, 3-5 weeks old. I’ve kept and bred and raised pet mice and rats for years. The head and feet are much too large in proportion for it to be an adult mouse of any species and the ears are set wrong. It does look a bit like a gerbil or jerboa in that picture, but the color and tail are wrong and so is the shape of it’s nose, plus what are the chances of your cat finding and killing a gerbil among the billions or mice and rats.
The tail is not furry, it’s darker in color due to skin color, ‘tail wax’, and the sparse hairs that all rats have on their tail.
And Brown rats which are what people think of when they hear ‘rat’ are not ‘huge’. Bigger than that, yes, but ‘giant rats’ (unless we’re talking tropical species or non-rats such as muskrats) are fictional. Males average 12oz, females 9oz. I had a big fat fancy rat once who was just over a pound, but he still fit comfortably in my one hand and I’m a small person.
‘Tail wax’ is a phrase I never wanted to hear.
LOL! It’s even grosser than it sounds. I used to clean my rat’s tails with a toothbrush to get it off.
Another vote for baby rat.
Final answer: We don’t know.
You may not; but I KNOW that’s not a mouse of any species. Could possibly be several kinds of rodent, but not a mouse.
My Vote: Rat
The tail and hands/feet look just like the many young rats I have had as pets.
Only the rounded ears look slightly wrong but I am convinced it’s a rat.
I don’t know that the color and the tail are wrong, and the shape of the nose looks plenty gerbil-like to me (considering it could also be slightly distorted by kittybites). Compare this picture of a Mongolian Gerbil. Look at the elongated ears and the long rear legs. If it was a younger gerbil it might not have the darker feet that my picture does; also, pet gerbils come in a huge variety of shades and color patterns. Certainly it looks much more like a gerbil than the rat or mouse pictures we’ve seen so far.
I vote for “escaped/feral pet gerbil.”
I think young rat.
To me, it doesn’t look much like that picture of a gerbil. The tail is too thin and short and not furry, and the front legs, feet, head, snout and ears are all proportionately larger. It’s much too large compared to the cat (no matter that cat’s size) to be a juvenile gerbil.
It does look just like this dead baby rat of a similar age. I don’t know why you won’t take my word as an expert, since I’ve handled 50 rats this age and am intimately aquainted with their physical characteristics. 
I have also had gerbils. That’s not a gerbil.
