So for the purposes of this question, the following items are already determined by our world:
- The humans and human society are in very beginning of an Industrial Revolution almost identical to our own on an Earth identical to our own, meaning they are technologically and socially on par with Western culture in 1760-1800.
- Animals have developed human-level intelligence. Direct quote from Wikipedia:
Human intelligence is the intellectual capacity of humans, which is characterized by perception, consciousness, self-awareness, and volition. Through their intelligence, humans possess the cognitive abilities to learn, form concepts, understand, apply logic, and reason, including the capacities to recognize patterns, comprehend ideas, plan, problem solve, make decisions, retaining, and use language to communicate. Intelligence enables humans to experience and think.
- Not all animals have become intelligent. Firstly, it has only affected mammals. No lizards, no birds, no bugs, etc.
- Secondly, it has not affected any animals who were genetically manipulated by humans and domesticated. So cows, pig, sheep, "food animals" are still dumb. Same for cats and dogs, they are still our companions but not intelligent.
- Thirdly, even among "wild mammals" the newly intelligent animals are a small percentage. Say about 10-20% of current animals' populations were affected. So we aren't talking about hundreds of bears suddenly becoming human smart, but maybe a few dozen.
- For purposes of the question, I'd like to focus in on Eastern U.S. and Western European species of wild mammal, such as bears, wolves, rodents (squirrels, rats, rabbits, mice, etc), deer/elk/etc, wild boar, and so on.
- We are assuming that granting human intelligence and sentience to these animals has brought them together mostly peacefully, so that animals who were once predator/prey (deer and wolves for example) are now working together due to these special circumstances.
- Also for the purposes of this question we will be assuming that the animals can communicate to one another. That whatever mystical, fantastical, or magical "incident" let's say, that gave them this intelligence also allowed them to "speak" to one another, whether through telepathy, or powerful perception of body language and their natural animal sounds. This telepathy or perception, however, only extends to other animals affected by the same incident and is cross-species.
How could the animals reveal their newly found intelligence to human society?
How could the animals first communicate their sentience in such a way as to convince the humans of their intelligence? Assuming that the animals are now smart enough to understand and parse together local language (English), but still lack the physiological ability to form human speech, how do they communicate? Would it be easier for them to approach as a large group or would they select a "liaison" to attempt to approach human society? Which species would be best suited for this? Would they head straight for places of government and large cities or would they drum up support from smaller villages?
You don't need to answer all questions above. They are just a few examples of discussions that branch off of the main question which is in bold. Basically a discussion of what methods would work best for human-intelligent animals, who had previously been seen as wild, dumb creatures, to convince humans they are now smart enough to cause some serious problems.