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[Ron Dreher]

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Risso's dolphins make presence known in channel 


Peter Howorth 






 


 


 


 



Risso's dolphin breach: This Risso's dolphin bursts through the surface like
a missile from a submarine. 


PETER HOWORTH PHOTOS 


 


 



Risso's dolphin eye: Risso's dolphins love to watch people as much as we
love to watch them. 


 


 


 



Risso's dolphin surfacing: This Risso's dolphin sends a crystalline bubble
to the surface as it emerges to breathe. 


 


 

July 20, 2008 6:22 AM

Santa Barbara has many species of small whales, but we often don't think of
them that way. Instead, we think of many of them as dolphins or porpoises
rather than as small whales.

Conversely, killer whales and pilot whales are just large dolphins, although
few people realize this. In truth, they are all odontocetes, or toothed
whales.

Risso's dolphins, superficially similar to the pilot whale in shape, are
among the more interesting of the small cetaceans. They are light gray or
white when born, then turn chocolate brown to almost black as adolescents.
As they mature, they again turn white, although the fins have darker
shadings. They also often have dark patches around the eyes.

Mature Risso's dolphins are covered with long scratch marks. Scientists
assumed the beaks of squid, major prey for the species, caused these. A
closer inspection often reveals that the scars are evenly spaced, however,
suggesting fracases with other dolphins, either of the same species or
perhaps from other species.

Risso's dolphins can be aggressive toward other species, including even
large whales. They have been observed bow-riding the frontal wake of blue
whales, zipping back and forth and causing the whales to flee. On one
memorable occasion, I observed an exasperated blue whale flip a Risso's
dolphin end over end with a toss of its huge head. The dolphin hastily
abandoned the chase.

Following the 1982-83 El Niño event, Risso's dolphins moved into Southern
California waters in numbers, occupying a niche once held by short-finned
pilot whales. One researcher theorized that the Risso's dolphins might have
ousted the pilot whales through competition for squid, primary prey for both
species. Other species of marine mammals also changed their distribution
following the El Ni0x96o event, however.

After the El Niño, years went by with few if any sightings of pilot whales.
Over the past several years, they have turned up in larger numbers, although
nothing approaching the numbers seen in the past. Their population trend in
this region is unknown.

Like pilot whales, Risso's dolphins have no noticeable beak. Their snout is
blunt and their head bulbous, much like that of the pilot whale. Risso's
dolphins are quite large, growing to 13 feet long and weighing several
hundred pounds. Calves are just under 5 feet long at birth.

Risso's dolphins are often seen off the north shore of Santa Cruz Island,
especially in late spring, summer and early fall, when squid are prevalent.
Unfortunately, their preference for squid has led to competition with squid
fishers. According to NOAA Fisheries, Risso's dolphins with fresh squid in
their stomachs have turned up dead from bullet wounds.

Though generally not as gregarious toward boats as are common dolphins and
bottlenose dolphins, Risso's dolphins sometimes do ride the bow waves of
small craft, particularly if the boats are not moving fast.

Although individuals are sometimes seen, Risso's dolphins usually travel in
groups of 25 to several hundred. Sometimes they travel abreast in a long
line, possibly part of their hunting strategy.

Risso's dolphins can put on quite a show, with some individuals racing at
high speeds through the waves, slapping their flukes down on the surface and
making a loud noise, or leaping completely out of the water.

One of the most endearing habits of this species is lifting its head out of
the water and making definite eye contact with people in boats. Other
species often roll on their sides while bow riding, gazing up at the people
above, but Risso's dolphins observe folks directly.


 

  

Makes you wonder if they enjoy looking at us as much as we enjoy looking at
them.

 

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