Thuja Green Giant - Trunk issue
This does not look like animal damage but probably a frost crack. These vertical cracks occur at weak points in the trunk due to seasonal temperature fluctuations. They are most likely to form on a southwestern exposure where late afternoon sun heat gives way quickly to freezing temperatures in winter. The outer layer of wood contracts more quickly than the inner layer and a crack forms.If the tree is fertilized too late in the season, delicate new growth is promoted that is more susceptible.
The wound should heal itself though it can reoccur in successive years. Keep your eye out for signs that fungal or bacterial disease has entered through the wound while healing.