In the international fight against poaching, eyes in the sky could make all the difference.

But drones are expensive and hard to fly, putting them out of reach of many park managers.

For the Wildlife Conservation Unmanned Aerial Vehicle (UAV) Challenge, an international competition that runs until next spring, 137 teams of students, hobbyists, and engineers from 29 countries are designing and building affordable, easy-to-use drones for the rangers of South Africa's Kruger National Park. The goal: unmanned aircraft that can scan Kruger for poaching activity and map routes for the rangers to apprehend traffickers.

Here are five ways drones are being used on the front lines of wildlife conservation around the world. (View photos of elephants and anti-poaching efforts.)

Drones