They changed some stuff in Tibia, now during night some monsters appear and at day some others, I'm not sure when it happened but you can also see the werewolfs appear in Darashia in place of Wyrm depending on time, cobras also only been spawning during day, more bats appear during night, noticed it during tournament trying to get a cobra tongue for access of lion rock, if you go on the way to green djiin during day you can find cobras during night you can't, don't know if it is of any help but think cipsoft is trying to show some logic on monsters respawns like "bats goes out at night" cobras walk around during day.