If you know a bit about AI you may know that learning algorithms generally have variable learning rates. Typically learning rates are high to begin with then slowly drop as the algorithm progresses.
The reason for this is that early in the learning process you want find answers that are approximately correctly quickly so later you can refine and perfect them.
This high -> low learning rate strikes a balance between the importance of finding answers quickly vs spending time to perfect an answer.
If you keep the learning rate high the learning algorithm will be unfocused and constantly consider new potential answers. If it's kept too low it will waste time perfecting answers that are completely wrong.
Humans seem to do something similar. Children (especially new borns) learn extremely rapidly. Then as we age we tend to learn slower and mostly just refine existing views. Generally people don't change radically past their teenage years and by our early teens years we typically have a good sense for who we are and what we might become.
I guess what I'm trying to say here is that it's extremely important that people are exposed to things like language and maths from an early age otherwise it becomes difficult to ever master them.
For example if you don't play a musical instrument as kid although you might be able to learn later in life you're unlikely to ever become a great musician.
Of course individual also have some varying amount of hard-wired intellectual capability – some people have genetic learning disabilities, others seem to be uniquely gifted in their ability to learn.
I think the answer to your question is difficult to answer because it largely depends on what you mean by intelligence. This hypothetical individual you describe would probably score extremely poorly on any traditional IQ test and would never fully grasp language.
However, there's not reason to think they wouldn't be very capable in other ways. They may have very good hand-eye coordination. They may be very good at communicating with orangutans. They may have an instinctive understanding of the rainforest and environment they grew up in. Whether you class that as intelligence is really up to you.
That said, in my opinion intelligence is can typically be defined as cognitive tasks that humanity collective deem important. So if you take a more traditional definition then no, this individual wouldn't be considered intelligent because they probably wouldn't be good at language, math and logic puzzles.