"Little ones can take it easy"
"Actually, thanks to the little one who looks like Marisa, living a life everyday can really take it easy"
"But, if living without the beloved little one, who is there to make yu itself easy?"
With reasons that make sense (for yukkuris) like these making them think that getting accompanied by things that are nothing but their children is of the utmost urgency, they will get busy with multiplying.