You can try to create a vector array and add current location to array every 3 or 5 seconds when animal is moving. Create a function that will save the last 50 (or more) locations in array by replacing the oldest with new locations.
The way you show the trails depends on your game mechanics.
For example, you can display all trails that are close to a character within a certain radius via particle effect or similiar.
Or you can find the nearest animal and show trails/footprints from that animal only.