And if you wanted another creature you would either have to kill or release the one following you or get the second rank. The stronger the creature the longer it takes to grow(Geckos(or similar Fallout 4 Creature)would take about 1-2 weeks and Deathclaws(or similar Fallout 4 creature)would take about 1 1/2 months to get full grown even longer if you want an Alpha Male/Female), the Females would give you an egg every now and then, while the Alpha Males are stronger. Perk Requirements:Level 14 and 7 Charisma Perk Ranks:2 Perk Name:Animal Control Perk Idea:When you carry an egg around w/ you for a few hours It'll hatch the stronger the creature the longer it takes to hatch(Gecko eggs(or a similar creature in Fallout 4)would take about 2-3 days to hatch while Deathclaw eggs(or similar Fallout 4 creature) would take about 6-7 days to hatch),it starts as a Baby/Young and slowly grows as it gains XP from kills you or it makes(5-10% of XP goes to it until its full grown).
(Remember these most likely be in the game)I'm thinking a Perk that allows you to hatch Creature eggs since in New Vegas your always finding eggs everywhere.