Join me in the cold, dark, life-sustaining NE Pacific Ocean to discover the great beauty, mystery and fragility hidden there.

The Case of Stones in Sea Lions’ Stomachs

Did you know that stones are commonly found in the stomachs of Steller sea lions?

These stomach stones or “gastroliths” are as big as 12 cm!

Share your theories about why you think this might be after viewing the video below. It provides you with information to help with this Marine Detective case.

Happy sleuthing to you!

 

Click here for SeaDoc footage of Steller Sea Lions playing with California Sea Cucumbers.

7 Responses to “The Case of Stones in Sea Lions’ Stomachs”

  1. Stacey

    Such a great puzzle – one I’ve spent some time scratching my head over in WIC days past! I think more information about the size and sex of sea lions with gastroliths could help to narrow down the list of possible explanations for this phenomenon. The buoyancy regulation and stomach fullness hypotheses would work better for large males than females. Perhaps water movement could explain why the smaller stones have little or no growth in comparison to the bedrock though? xo

    Reply
    • The Marine Detective

      Thanks so for this insight Stacey. It would be so valuable to have age and gender information re. gastroliths. Regarding the stones not having growth, it is pretty rare to have a bed of rocks like this with no current while everything around them does.

      Reply
  2. Gillian Butler

    I’m wondering if similar behaviour has been observed in captive animals? If access to stones is available (if it isn’t perhaps it should be provided). Thanks Jackie xoxoxo

    Reply
    • The Marine Detective

      Thanks so much Gillian. I know of no instances where this has been observed in captive animals but, as you identify, this is likely because stones of ingestible size are not available.

      Reply
  3. Amber

    I think this behaviour is very interesting! My best guess would be that the sea lions are manipulating their mouth and jaw in order to prepare for the real thing – forage fish! I am curious to know if this behaviour is seen more in young Steller sea lions.

    Reply
    • The Marine Detective

      In my opinion, this is the best hypothesis to date! That the behaviour is to learn how to manipulate and eat prey – even bigger fish like salmon. It would thereby be very valuable to know if the behaviour was more common in juveniles. Thank you so much Amber!

      Reply
  4. Anonymous

    I have witnessed captive animals swallowing a lot of foreign objects including stones that fallen in the pool. One study I was part of had them eat a heavy concentration of squid, they would regurgitate the pens daily.

    Reply

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