If I were to do a study on predators for four weeks, I would either pick four predators and focus on one a week or pick four different type of predators from the different classes of animals and study one each week.
Week Two - Lion
Week Three - Eagle
Week Four - Snake
If you wanted to make the study a little longer you could add others.
Or for big cat enthusiasts:
Week Two: Lion
Week Three: Cheetah
Week Four: Mountain Lion/Cougar
Activity kits that would be interesting depending on the animals chosen, including casting kits for ages 7 and up. Of course there won't be activity kits every animal unless you do some real searching. Reading, watching videos, play-acting and playing a game or two should keep the kids interested. You can fill out the study with coloring books and sticker books, I have an Animal Predator sticker book, ISBN 1-84510-626-1, or you might be able to find an activity book that contains several different activities.
Hope this gives you plenty of ideas! We homeschool year-round and I like to finish our products, I've assessed that we should be done with all our first grade curriculum in May/June. Camille's birthday is in July so I'd like to wait until after that to start 2nd grade. If our dinosaur study gets interrupted that's fine, we could do it in two weeks.