Subcategory serializer only on single subcategory page

I am building a category map sort of functionality, and each subcategory holds data for nearby cities that I want to add to the serializer when viewing just that individual subcategory. BUT when the user is looking at the parent category, I don’t want that data in that category’s “subcategories” object, as it’s a huge amount of data to select.

Does anyone know of a serializer that I can hook into to allow me to load up data when viewing a single subcategory that won’t show in the parent’s subcategories?