Abstract

Captive pinnipeds are commonly outliving their wild counterparts and often are reaching ages of thirty years or more. With extreme age comes associated problems such as arthritis, skin conditions, poor vision, cancer, dental issues, idiopathic seizures and other neurologic problems. At our institution, five California sea lions (Zalophus californianus) and one harbor seal (Phoca vitulina) have reached an age of thirty years or older. Medical management is directed at keeping the animals comfortable and optimizing their quality of life.

Arthritic conditions have been mitigated by weight management, use of chondroprotective agents and anti-inflammatory drugs, as well as placement of rubber mats to cushion the areas where the animal hauls out.

Idiopathic skin conditions have occurred in two California sea lions that were over thirty years of age. They frequently occurred in folds of skin and appeared to be similar to a moist dermatitis seen in dogs. The lesions resolved with appropriate systemic and topical antibiotic therapy. Another skin condition seen in geriatric pinnipeds has been superficial sores over pressure points such as the tuber coxae, likely due to the fact the older animals seem to haul out more frequently, and some animals prefer to lay in only one position. Generally these animals have concurrent skeletal or arthritic problems. The lesions were alleviated by the placement of heavy rubber mats in the haul-out areas.

Progressive visual problems have been observed in several geriatric pinnipeds. A few animals have developed cataracts. One show sea lion began to become progressively near-sighted beginning at the age of twenty-five. The animal was healthy and active in all other respects and still has vision at the age of thirty. The staff was able to continue to train and work with the animal by giving more obvious hand commands closer to his face and using audible commands. The animal can see well enough to find his way around his enclosure, and when moved to other areas, the animal will follow the trainers on a hand target.

Idiopathic seizures have been seen in one 29-year-old California sea lion and have been controlled for over one year with daily low doses of phenobarbital, beginning with a dose of approximately 1 mg/kg PO SID. When seizure activity was seen again after several months of treatment the dose was increased to 1.5 mg/kg PO BID.

Because predators, pollution, parasites and epidemic disease have been eliminated from captive animals' environments, cancer, related to extreme age, is becoming a more common finding in post mortem examinations. Of the five aged pinnipeds that have died in the past six years, four had neoplasias. Malignant melanoma was diagnosed in a 29-year-old harbor seal and was successfully managed for over three years, at which point the animal's health declined and it was euthanized. A 24-year-old female California sea lion showed progressive neurologic problems and after a year of treatment began to show more severe clinical signs and was euthanized. She had a malignant glioma in the brain. One 30-year-old male sea lion died acutely with no previous clinical signs and was diagnosed with a large hemangiosarcoma in the spleen. Another 30-year-old male sea lion died after three months of vague clinical signs and was diagnosed with squamous cell carcinoma that involved the entire mediastinum, and had miliary tumors adhered to the tissue lining the thoracic cavity.

Every effort is made to make the geriatric pinniped patient comfortable and to optimize its quality of life. In some cases this may be as simple as providing rubber mats for it to lay on when it hauls out. Many pinnipeds show no obvious signs of aging well into their twenties, and a few exhibit normal activity and behavior when they are over thirty years old.