Abstract

Stereotypic behaviors are frequent subjects in animal welfare research. Rumination syndrome, similar to behavioral regurgitation, has been reported in humans, non-human primates and bottlenose dolphins, among other species^1,2,3 and can result in a suite of secondary conditions including esophagitis, aspiration pneumonia, and megaesophagus⁴. Management strategies are often multimodal including behavioral, enrichment, and pharmacologic therapies⁵.

We present a 19-year-old castrated male California sea lion (Zalophus californianus) with a 17-year history of rumination syndrome resulting in difficulty maintaining weight and intermittent bouts of aspiration pneumonia. Previous management strategies included combinations of aversive behavioral control, pharmacologic therapies (SSRI’s and tricyclic antidepressants), and post-feeding session environmental changes encouraging retention of ingesta. Initially, there were positive results in curbing rumination, however the behavior ultimately returned in frequency and severity.

Fifteen years after the onset of rumination syndrome, megaesophagus developed. Acetylcholine receptor antibody tests and resting cortisol were normal, but thyroid hormone levels were below normal⁶. Esophagitis and hypothyroidism have been implicated as causes for megaesophagus^5,7 thus, new management strategies were implemented including more frequent feeding sessions, feeding in an upright position, a novel in-session cognitive video game, end of session “playtimes” with enrichment other than food, and pharmacologic therapy using naltrexone (opioid receptor antagonist) and levothyroxine (synthetic thyroid hormone). Thyroid hormone levels improved after 3.5 weeks on levothyroxine, and rumination behavior decreased from 360 minutes to 50 minutes per day, after 5 months of therapy. The animal has maintained a healthy weight and improved health with no further instances of aspiration pneumonia, thus improving welfare.

Acknowledgements

The authors would like to sincerely thank the incredible animal care team at the U.S. Navy Marine Mammal Program for dedicating their lives to the animals under their care. Specifically, the authors would like to thank the veterinarians, veterinary technicians, and the training staff working with the California sea lions both present and past.

Literature Cited

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