Reported Annual Travel Distances in Four Studies of Migrating Animal Populations
| Species | Continent | Distance (km) | Measurement method |
|---|---|---|---|
| Brown bear | North America | 1,325 | GPS |
| Tibetan antelope | Asia | 700 | RTD |
| Caribou | North America | 4,868 | GPS |
| Reindeer | Asia | 1,200 | RTD |
Some studies of migrating animals measure how far the animals travel in a year by fitting individuals with GPS tracking collars. Other studies track annual round-trip distance (RTD), which is equal to double the distance separating the two habitats a population migrates between each year. A researcher argues that since GPS records all of an animal’s movements, using the GPS method to track a population would result in significantly higher recorded travel distances than using the RTD method would. For example, it’s very likely that the distance reported for the __________