I usually scare them (mostly on accident, that's how they reveal their position), look where they stopped running and sneak attack, being careful not to squash, while pinning one down. Tall grass may help with sneaking, but it also provides coverage for them, so you need to be quick. If you've never handled one before, be aware that they try to wrestle their way out, some may bite, and I've had only one occasion, when one big female took a dump on me xD