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

Unmanned drones, an emblem of modern war and now a tool of modern conservation, can stop poachers before they strike by providing live video feeds that reveal their locations. (Read "Drone Nation" in National Geographic magazine.)

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.)

1. Fighting Wildlife Crime

Drones already act as wildlife police, scoping out poachers in Kenya and Nepal. With a $5 million grant from Google, the World Wildlife Fund (WWF) has launched aerial surveillance in remote areas in Africa and Asia, where endangered species like elephants and rhinoceroses are most vulnerable to illegal trafficking.

Beyond poaching, unmanned aircraft are tackling illegal fishing, hunting, and burning. In Belize, drones are saving threatened fish populations by finding vessels that are over their catch limits, fishing without permits, or in restricted waters.

2. Getting Up Close

By getting nearer to animals than people often can, drones take intimate photographs and collect solid data. Piloted by scientists at the National Oceanic and Atmospheric Administration and the Vancouver Aquarium, a hexacopter drone (a remote-controlled aircraft with six rotors) recently hovered 100 feet (30 meters) above a group of killer whales off British Columbia, Canada. With images from the drone, scientists were able get a better picture of which whales were malnourished, which were pregnant, and which were likely to die.

3. Counting Populations

Getting an accurate population size not only tells park managers how much food and habitat is needed for a certain species, but also how threatened that species might be. (Read about other drone uses ranging from border patrol to crop dusting.)

In Colorado's San Luis Valley, the U.S. Geological Survey and the Fish and Wildlife Service are using a retired Raven A—an aircraft once deployed in warfare that's been replaced by sleeker combat drones—to tally sandhill cranes, a popular game bird.

"It's a safer alternative to the fixed-wing aircrafts we've been using since the 1950s," said Leanne Hanson, the USGS biologist flying the drone. "When they're roosting at night, the cranes are not disturbed when the Raven flies over. They don't flush off and collide mid-air."

4. Getting the Big Picture

To understand how climate change and industrial development affect wildlife, ecologists need a birds-eye view. National Geographic grantee Jeffrey Kerby uses drones to map caribou habitat in west Greenland, tracking changes in plant cover and sea ice over time.

"[Surveying habitats] is a very time-consuming and labor-intensive task, requiring researchers to spend days hiking through the forest looking for these nests," said Lian Pin Koh, an ecologist who worked in Sumatra and a pioneer in drone conservation. "A forest that would normally require one to two weeks to survey can be done in a few days using a drone."

5. Doing Chores

Drones also assist in the unsexy tasks of conservation, including weeding and fence mending. In 2012, a Raven aircraft scanned Hawaii's Haleakala National Park for tears in the park's fence and for miconia, an invasive weed threatening native Hawaiian flora.

The mission wasn't as successful as hoped—high winds made for blurry pictures. But the drone saved the rangers the trouble of navigating the park's extreme temperatures and rugged terrain, said Matt Brown, Haleakala's chief resource manager. The pictures were clear enough that rangers were able to identify places worth visiting to check on ripped fences and troublesome weeds.