No, it isn’t tired. When an anaconda swallows something as large as a capybara, each side of its jaw moves separately, almost as if it were walking over the prey to push it toward the esophagus.
That effort completely throws off the symmetry of its head: the cranial bones separate, the elastic ligaments stretch to the limit, and even the lower jaw—divided into two halves joined only by cartilage—ends up out of place.
The “yawn” is actually the moment when it forces that entire system back into place, regains the oxygen it lost during hours of digestion and, in the process, uses the Jacobson’s organ in the roof of its mouth to smell whether there are predators nearby while it is more vulnerable than ever. 🐍