Here is an answer by stages for you.
The fresh stage is the first phase of decomposition that begins approximately four minutes after death and lasts around three days until putrefaction. Following initial decay, approximately 4 to 10 days after death, the body begins the second stage of decay called putrefaction. Than black putrefaction, also known as active decay begins about 10 to 25 days after death. The fourth stage called butyric fermentation begins around 20–25 days after death. The final stage in animal decomposition is dry decay. Dry decay begins between 25 and 50 days after death and can last up to a year. The only remnants of the body are dry skin, hair, and bones.
I would say at 5+ months it's safe to say the animal is bones.