I'm a neuroscientist who used to work with animals, and while I didn't focus on consciousness, I don't think it's a reasonable scientific perspective to start from the assumption that animals don't and require proof that they do. Clearly there's a spectrum of intelligence across species, but plenty of animals appear to have theory of mind, complex emotions, object permanence, tool use, long term memory, spatial navigation, some idea of the self, etc. Humans are better at language, and math, and destroying the planet, but that doesn't explain why our feeling of consciousness wouldn't be substantially similar to a great ape or an Australian shepherd.