The Daily Bucket: Take a deep breath
Backyard Science is a group that celebrates the beauty and of nature in photos, facts and conjecture. No natural object or phenomenon is off topic. The Daily Bucket is the vehicle of our aims. Share your observations and a record is made, some day these records may be a somber reminder of what has been wasted. But for we lucky ones, all this is a celebration. Photos are welcome.
This is a Dall Porpoise rising, note the position of the blowhole on the back of the head.
These porpoise are fast movers, the one on the right has made a 90 degree turn, surfaced and taken a breath. All in about two porpoise lengths. How do they manage?
This was probably more pictures than needed to convey the action of a lazy dive, but these are astounding animals. Consider that without a camera with sports mode most pictures intended to be of Dall porpoise are just big splashes, these puppies are fast.
Here is a Dall rising to breathe, the exhalation has begun and the exhaled air is being dragged backwards but hasn't separated from the boundary layer next to the sleek animal's skin.
This is a lucky shot, you can barely make out the little bump on the nose of the porpoise that is one of the secrets of their snorkel gear. The water has separated from the rostrum and head, there is a ventilated area over the blowhole. The rest of the animal is covered by a layer of water. Conjecture: the little bump creates a low pressure are above it that cavitates at high speeds (pressure low enough to create water vapor) that collapses drawing air over the blowhole
under the surface of the water
Here the ventilated region is collapsing but there is still connection to the surface air. Though I doubt than inhalation is taking place at this point. (ya' never know though, these guys are risk takers and heart breakers)
Here you can see the funnel of clear air (sort of) above and behind the blowhole.