Research on "probabilistic thinking" in non-human animals?
Try an internet search on animal learning probability.  Although that might not be what you want because it sounds like you specifically want insight as opposed to learning in general.

Your particular example is problematic because you're inferring far too much on the subjects part. They might prefer B because they just want more of anything offered. The experiments need to be much more careful than that in order to attribute effects to probabilistic thinking. What kind of response will occur doesn't just depend on the probability of events but what kind of reward contingencies are associated.  Both people and animals do dumb things with simple probabilities and rewards.  But they do the same thing. Does that justify an argument that they have a probabilistic sense?

Deriving a distinction between insight and conditioning is sometimes problematic (for example food aversion in rats) and insight is usually only accepted when it can pass the interocular impact test.  While I can show you lots of papers on probability learning I'm unaware of any that tap insight about probabilities.

Consider the problem for the researcher. In order to establish insight into probabilities the subject has to experience the events repeatedly in a relevant way so that they become learnable. Given this takes a degree of exposure in the first place it would be very hard to dissociate conditioning from insight based learning.

Also consider that people sometimes can learn probabilities but don't always do intelligent things with them. For example, when there are two possible events and one happens 75% of the time people tend to select the frequent event 75% of the time. This is rather boneheaded because selecting the frequent event all of the time will give you the most accurate performance. Animals actually learn to do the latter. So maybe animals have a stronger probability sense? Regardless, they clearly they learn probabilities.