When in an emergency survival situation were you don't have access to clean or at least "okay" water but to wildlife (or it is at least easier to grab a snake for example than to gather water), is it a good idea to drink blood to avoid dehydration?
While various sources suggest drinking some blood in emergency will help, the risks outweigh the benefits.
From 5 Myths of Dehydration:
Sure, there’s water in blood. But whose or what’s blood are you planning to drink? Some of the traditional cattle cultures of Africa still consume cattle blood, often blended with milk. But this is done for protein and minerals, rather than hydration... While the consumption of turtle blood and other animal blood has helped to keep oceanic castaways alive, the risk doesn’t usually justify the gain. Drinking the raw blood of any creature could result in the contraction of a pathogen.
As most animals that you are likely to catch need water, use this as a brief stopgap (a few days) while you find their water source, which is hopefully not too far away.