There's good news for Rudolph and his friends - an app is helping officials reduce the number of reindeer killed in traffic accidents in Finland.

Some 300,000 reindeer freely wander the wilds of Lapland in Arctic Finland. An estimated 4,000 are killed every year through road accidents, officials say, and compensation to reindeer herders can be expensive.

Most of the accidents occur during the dark winter months when the animals are hard to spot.