Blue Ear Tag on a Doe

November 7, 2019

Question: I was hunting up in the Mendocino National Forest and saw a doe with a blue ear tag on her left ear. I have never seen this before and was curious as to whether or not you may know what the tag means. I have attached a picture that I took of the deer. I hope you satisfy my curiosity! (Rosanna)

Answer:  Thank you for the photo! We shared it with our Deer Program biologists, who were tickled to see that one of their study deer – aka 7303 with the blue left ear tag 804 – was alive and well in the Mendocino National Forest – almost eight years after she was captured and tagged there by our biologists. She is estimated to be 14 years old today.

Deer 7303 is a survivor for sure. She was part of a five-year population assessment — from 2009 to 2013 — of Columbian black-tailed deer in the Mendocino National Forest conducted by the California Department of Fish and Wildlife (CDFW) and researchers from UC Davis. The 2014 Final Project Report is still available online at https://nrm.dfg.ca.gov/FileHandler.ashx?DocumentID=153193.

Deer 7303 was one of 57 adult female deer captured as part of the study, along with 137 fawns and seven mountain lions. Deer 7303 was captured by tranquilizer dart on June 6, 2012, and determined to be 7 years old at the time. She also had a fawn with her. In addition to the blue ear tag, deer 7303 was outfitted with a GPS tracking collar, which she wore for 453 days before the collar dropped off. All collars were fitted with automatic releases to drop off after a certain amount of time.

Deer 7303 has fared much better than many of the other study deer. The study found that while Columbian black-tailed deer in the Mendocino National Forest were abundant with average pregnancy and birth rates, their population was on the decline primarily as a result of low adult female survival. Researchers investigated deer mortalities and confirmed predation accounted for approximately 57 percent of the 21 deaths investigated by staff. Most of the predation was from mountain lions, one was killed by a black bear, poachers took two of the does, and seven died from unknown causes. Black bears, however, were the main predators of fawns, particularly within 30 days of birth. The researchers also found that habitat quality – or lack thereof – played a role in low fawn and doe survival.

The assessment of deer in the Mendocino National Forest is just one of many studies conducted by CDFW deer biologists to better understand the mechanisms that drive deer populations throughout California.