Animals often do things that people find gross - such as eating dung or eating each other. Exploding Ants, by Joanne Settel, talks about some of the animals survive that we might not be willing to do. For example, while the swallowtail butterfly is still a caterpillar, it looks like a bird dropping in order to discourage birds from eating it. As long as the caterpillar staying still, the birds don't know that it's alive. Other interesting lifestyles include murderous birds, brainwashing, exploding ants, dog mucus, ticks, lice, vampire bats, eyeballs that swallow, rhinocerous urine, and more.
This book is good for boys who like gross stuff, and is a cool introduction to the interesting ways that animals adapt to the world. It has clear, color photos, and includes a glossary, selected bibliography, and an index.
If you are looking for a book for an upper elementary or middle school child who likes animals, this is a low-key look at a piece of the animal world.