Abstract
Every spring, stranded Pacific harbor seal (Phoca vitulina richardii) pups are admitted to The Marine Mammal Center (TMMC) in Sausalito, CA for rehabilitation. Exposure to a variety of factors both in utero and in the environment, including toxins and infectious diseases, can affect neurological development.1,2,3 Neurological scales are established in both human and veterinary medicine to assess disease presence and progression in patients.4,5 Clinical neurologic abnormalities recorded in marine mammals include seizures, head-shaking/bobbing, muscle fasciculation, myoclonus, hypersensitivity, nystagmus, and jaw smacking.1 These qualitative signs are valuable tools for determining patient outcome, but often require specialized training to interpret. A neurological scoring method was developed at The Marine Mammal Center for use by lay staff as well as veterinary professionals. We hypothesized that lower neurological scores would be associated with a positive outcome of release into the wild. Neurological observations were conducted on-site between January-August during three pupping seasons (2015 to 2017). Animals were assessed weekly, and assigned neurological scores based on six behaviors: interaction with other pups, response to tactile stimulation, ability to move on land, to swim, to hand-feed, and to eat dead or live fish in a pool. Individuals were observed for either a total of ten minutes or until all behaviors were recorded. Each behavior was scored from one to four with lower scores signifying a normal behavior and higher scores indicated slow or underdeveloped responses. A total 1305 observations were collected on 193 harbor seals pups, of which 159 survived to release, and 34 died or were euthanized. The mean score was calculated for each behavior and compared between seals that died and those that survived. Year was included in these tests to control for yearly differences in seals, seal husbandry, and data collectors. Three behaviors (interaction with other pups, response to tactile stimulation, and the ability to eat dead or live fish in a pool) were associated with survival, however, because some behaviors were not observed until animals had survived for several weeks (e.g., ability to eat fish in a pool), the data were skewed toward survivors. Data for response to tactile stimulation was available for all animals; this behavior was defined by a light touch on the back with either a hand or small probe while the animal was on land. Scores were assigned based on level of response: 4=no response, 3=moves head only, 2=attempts to move body by unable, 1=moves whole body away. The mean response to tactile stimulation score was different between animals that lived (1.146±0.303) and those that died (1.609±0.952, two sample t-test, t=2.8077, df=34.441, p=0.00816) with a lower score for response to tactile stimulation associated with greater survival. Thus, behavior is a useful prognostic indicator, and can be used with other clinical indicators when evaluating Pacific harbor seal pups undergoing rehabilitation. Our next steps are to investigate interactions between the neurological scores over the course of rehabilitation and developmental stage of harbor seal pups.
Acknowledgements
The authors thank Dr. Shawn Johnson, Dr. Claire Simeone, Dr. Sophie Whoriskey, Michelle Corsi, Stan Jensen, and Erica Marshall from The Marine Mammal Center for their mentorship and support; Dr. Esteban Soto-Martinez from The University of California-Davis; and The Marine Mammal Center for financial support and the opportunity to learn more about wildlife rehabilitation. Finally, the authors thank each individual volunteer, the true unsung heroes, at The Marine Mammal Center for their on-going efforts.
* Presenting author
+ Student presenter
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