[2] When Toronto Zoo opened in 1974, Mehren became its first female veterinarian at the institution, joining Dr. William Rapley.
[4] In 1982, she became a charter diplomate of the American College of Zoological Medicine (ACZM), involved in developing standards for training, experience, and certification of zoo veterinarians.
[5] Towards the end of her tenure at the Toronto Zoo, Mehren noted that her job had shifted from pediatrics of baby animals to care of geriatric animals as the zoo population aged over time.
[8] Among the organizations she has consulted for on animal health and welfare are: Canadian Animal Health Consultative Committee; National Wildlife Disease Strategy; Canadian Veterinary Medical Association; Ontario Society for the Prevention of Cruelty to Animals; Ontario Ministry of Health; Ontario Animal Care Review Board; the American College of Zoological Medicine; American Association of Zoo Veterinarians; Wildlife Disease Association; Ministry of Natural Resources, Aquatic Research and Development Section; Toronto Zoo Animal Care and Research Committee; and Canadian Council on Animal Care.
[9] Mehren has worked with numerous captive and wild species and individual animals.