How are the tags for intelligence and sapience different? Should this be clarified or merged?
The way I understand it, the difference is that sense of "I".
"Sapience," noun of sapient, is the ability to think, and to reason. It may not seem like much a difference, but the ability to reason is tied more closely to sapience than to sentience. Most animals are sentient, (yes, you can correctly say your dog is sentient!) but only humans are sapient.
There are lots of really intelligent animals, but so far as we know, humans are the only sapient species.
Intelligence and Sentience are probably the same thing, or close enough that they could be combined under one tag.