You guessed it! She is marking her territory with urine. Island foxes are very territorial. Territory = food resources. Food means she and her mate can support a litter of pups.
Thanks to Daniel for taking this great photo on a trip to Santa Cruz Island with Friends of the Island Fox. Interested in traveling to see island foxes? Subscribe to the FIF newsletter for info on upcoming trips.
Marking territory with urine communicates through scent to other island foxes. Both male and female island foxes mark territory with urine and with scat.
Island fox scat tells lots of stories:
Island fox diet and scat
Genetic science and island fox scat
Plants and island fox scat