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Physical, physiological, and behavioural welfare measures in captive california sea lions


Year: 2022

Elizabeth Wilcox 
University of Edinburgh, UK

Supervisor(s): Dr Laura Dixon


California Sea Lions (Zalophus californianus) are popular in captive environments due to their gregariousness, tameness, and trainability. Their complex cognitive and social capabilities have raised questions about our ability to meet their welfare needs in a captive environment.

The aim of the project is to use three measures – physical (body condition score), physiological (cortisol levels in fur), and behavioural (cognitive bias) - to assess California Sea Lion welfare in captivity. Integration of these measures will enable a holistic view of the welfare of the sea lions in captive environments to be taken.

Body score will be measured through weighing 18-23 California Sea Lions of varying ages and backgrounds in three different enclosures.  Subcutaneous fat depth will also be measured. These measures will be analysed with the support of marine mammal veterinarians at both participating zoos using photographs and typical weight ranges associated with emaciated versus robust sea lions in various rescue and zoo environments. Taking advantage of a sampling programme already operating, cortisol levels in fur samples taken from seals win each enclosure will be determined as a measure of physiological stress.

Cognitive bias testing, as an indicator of an animal’s affective state, has been validated in other species but not yet in sea lions (despite literature suggesting it as one of the most promising new techniques for measuring Pinniped welfare). Using fish as a reward, sea lions’ latency to approach a bowl that they have been trained to associate with potentially holding food will be determined. The latency to reach the bowl is defined as the time elapsed between release from the ‘stay’ position and an individual putting its head into the bowl or touching the rim placed at holding Tests will be conducted on land if possible, or all in water depending on zoo discretion. Latencies will be adjusted for differences in size and speed of an individual. It is hypothesised that sea lions with good welfare will approach bowls placed in positions that they have been trained to associate with no reward (ie bowl being empty) more quickly than those with poor welfare.

Finally, scan sampling for three specific affiliative behaviours considered to be indicative of sea lion welfare will be used to further validate the cognitive bias test. These behaviours are still to be determined upon pre-study observations, but may include allogrooming, naso-nasal contact, and specific play behaviour based on literature.

The results of all three test – physical, physiological and psychological - will be compared and any correlation with each other and the enclosure an individual kept in investigated.