Possible Clues:

• Tending to silence
• Saying very little
• Uncommunicative, saying very little
• Taken for granted it goes to pot - say nothing
• Understood vessel could be reserved
• Dumb animal turns; then I turn
• Reserved, saying little
• I, cat, have little to say, it seems, on the turn
• I, cat, get round and round to keeping my mouth shut
• Understood vessel to be quiet