Later in my Dinosaur Time story I plan on having a human civilization. However there is a very high risk of them being eaten by theropods like T rex or hurt by other dinosaurs such as Ankylosaurus.
So I planned on having ceratopsians like Triceratops defend the human civilization as the humans learn about the dinosaurs starting with ceratopsians.
However Triceratops, even as large as it is, is easy prey for a pack of T rex. And baby triceratops are nowhere near ready to defend themselves.
Also, egg laying would make there be gaps in the defense unless the humans told the ceratopsians something along these lines:
"Don't worry. We will protect the eggs while you protect us."
So what I am asking here is how many ceratopsians is enough for good defense?
And I am talking Triceratops mainly because of its size. However if you give me a good number of Triceratops for defense, I can easily look up different ceratopsians and their sizes(possibly even horn length which would be awesome) and deduce how many of that ceratopsian would be good for defense(not including protoceratops since they don't have any horns)