Giga spawn in valguero ark survival evolve

i can't find any of these gigan on my ark mobile, i have been tamed a titan, quetzal and many else but i never saw these creature on my ark mobile, can anyone help me why i can't find it?

I can't fine any gigan in my ark, i have tamed titan, quetzal and many else but i never saw a single one of these gigan, can anyone help me and tell me why i can't find it?