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Saturday, September 19, 2015

Long or short?

Yesterday was the third time I've seen common dolphins on a pelagic trip to Bodega Canyon and Cordell Bank.  Before 2014-2015, it would be more typical to see Pacific White-sided Dolphins or Northern Right Whale Dolphins, so I'm still learning how to separate Short-beaked Common Dolphins (Delphinus delphis) and Long-beaked Common Dolphins (Delphinus capensis).

On 18 September 2015, several groups of common dolphins approached the boat and rode the bow waves.  

Before showing the pictures, here's a reminder about characteristics to look for to separate the two species:

A Short-beaked Common Dolphin has (1) a shorter beak, (2) a brighter front panel (of the hourglass pattern along the side), especially between the pectoral fin and the eye, (3) a dark eyeline between the beak and the eye contrasting with the bright white front panel, and (4) a dark line extending from the pectoral fin to the vent. 

This picture is from the first group of dolphins:

And now here's a photo from the second group: 

I'm leaning towards calling the first individual a Long-beaked Common Dolphin, and the second individual a Short-beaked Common Dolphin.  What do you think?

Also, I reviewed my dolphin pictures from the September 6 boat trip.  I'm not sure about the identification now.  On the boat, we thought they were Short-beaked.  But now I'm going to retract that initial identification because I'm wondering if they could be Long-beaked.  If you'd like to review those pictures yourself, check out the post from 10 September 2015.  Let me know if you have any thoughts about the identification.

Watching these fast and graceful swimmers is always a trip highlight!

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