Pointer Dogs? No, Pointer Dolphins

7/5/14

Chloe Cavanaugh

            We blasted out east this morning with the intention of finding Buttercup, one of the spongers that we want to follow. While Mission: Buttercup did not come to fruition today, we did end up spending the afternoon on our coolest follow to date.

            We came across one of the classic east gangs, socializing as usual. Almost as soon as we began a follow on one of the group's known spongers, the dolphin left the group and picked up a massive Pseudoceratina sp. sponge, which looked like a head of golden broccoli. The dolphin sponged for the next couple hours, occasionally surfacing with a fish. Meanwhile, all of the other dolphins from before continued to socialize some distance away; all except one, that is. This one non-sponger hung out with our sponger for the full two hours of sponge time. The non-sponger spent the two hours resting, often snagging at the surface, presumably watching the sponger in action. We watched with growing incredulity as the sponger surfaced in the exact direction the non-sponger was pointing, and even began using the non-sponger as a predictor of which direction the sponger would surface from next. The dolphin was surprisingly and laughably accurate, only misleading us a small fraction of the time.

Photo credit: Madison Miketa

            The channel we were in was about nine to eleven meters deep; normally the bottom would be beyond sight at this depth, but the water was calm and clear enough that we could see straight to the bottom. At one point when the sponger dropped its sponge, the water clarity, combined with the non-sponger's indication, enabled us to see the sponger swim down to the channel floor right below our boat and retrieve the dropped sponge! Definitely an excuse to spend some more observation hours out east.

Peron Highlights

7/1/14

Chloe Cavanaugh

            This morning we took the boat up to Peron, an hour’s ride to the Northwest at blasting speed. As we rounded Skipjack Point, the red rock outcrop with a tall, smokestack of a lighthouse atop it, we began our first survey in the protected inlet beyond. The turquoise water might as well have been a glass window to the immaculate sand a couple meters below, and all the shovelnose rays and starfish that clung to the bottom.

Peron landscape
Photo credit: Ewa Krzyszczyk

We rounded the broad red dune of Peron Point. Pomboo pitched back and forth as we rode through the patch of sea in front of the point where the two tides meet. Professor Mann has aptly named it The Vortex. Our next survey was on Cha-cha and Flamenco. We stuck with them for a while because they belong to a group of dolphins that beach forage: the dolphins chase fish in the shallows and then hurl themselves up against the wet sand to corner and catch said fish. Sure enough, we soon witnessed Cha-Cha and Flamenco doing both partial and full beachings in their pursuit of fish.

Beaching dolphin
Photo credit: Eric Patterson

We spent the afternoon running a transect line. The objective is to go in a straight line from one GPS location to another, and survey any dolphins seen within 300 meters of that 8 kilometer-long stretch. James set the coordinates and drove while the rest of us kept vigilant watch from each side of the boat. We saw many dolphins, but the highlight of the transect came when we spotted a very strange-looking chop-off a couple hundred meters out. Closer inspection revealed a light gray, lumpy, isosceles triangle of a fin. We squinted in confusion as the dolphin surfaced again.

"Sammy" the Sousa
Photo credit: Madison Miketa

“It’s Sammy!” cried Professor Mann. Sammy the Sousa chinensis; an Indo-Pacific Humpbacked dolphin that hangs around Peron. Seeing Sammy in comparison to the bottlenose dolphins we see illustrated the contrast between the bottlenose's quick dives and long, streamlined body and Sammy’s slow dives and stubby, misshapen frame. Seeing Sammy was certainly one of the highlights of the season.

Sexing Success

6/25/14

Chloe Cavanaugh

            Today was our first day out with Professor Mann here, and our second full day of the season. We kicked the morning off with several surveys and a dive follow on two spongers. After lunch we began a mother calf dive follow on Kite and her calf, Otus. The naming theme of their line is birds: Kite’s mother is Kestral, and her other, older calf is Osprey; Otus is Latin for owl.

 Kite and Otus
Photo credit: Ewa Krzyszczyk

           The three-hour follow stretched through a beautiful afternoon: rays of sun broke through the clouds onto the distant ocean and the water was smooth as silk. Kite, a known sponger, sponged for the first half hour of the follow, and then switched to snacking, a foraging tactic in which dolphins chase a fish up to the surface and go belly up to trap it there while they catch it. Often with snacking bouts we see the fish breaking the surface or even jumping out of the water in an attempt to escape. Otus never picked up a sponge, but the calf did join the mother in snacking bouts and other dive foraging later on. We hoped Otus would bowride so we could sex it, but the two never came over to the boat.

A calf snacking belly up in pursuit of a fish

Photo credit: Ewa Krzyszczyk

            The setting sun turned the water to liquid gold as we neared the end of the follow. The light was fading fast, but Professor Mann was determined to sex Otus. We did one last survey of several dolphins that had joined up with our two at the end of the follow. Finally, Kite and Otus came over to bowride—Professor Mann and Eric rushed to the bow, leaning over the edge, but Otus wouldn’t roll over onto its back. He swam off and came back again, and this dance was repeated a few more times. Then, right before darting away for good, Otus barrel-rolled, giving Professor Mann the one glance she needed.

           “Long gen slit, big gap, no mamms, grade A view!” she cheered, with high-fives all around. Otus was officially a boy. 

A ventral shot of a male dolphin with long genital slit clearly visible.

This individual has a scratch of unknown origin to the left of its genitals.

Photo credit: Ewa Krzyszczyk

From a few dolphins to dozens!

Check out Georgetown undergraduate student Chloe Cavanaugh's second blog post from the field!

6/20/14

This afternoon we did our second follow of the season, on a sponger with a very identifiable chop-off for a fin. I wrote our first focal follow of the season, on Kiya and her calf, Wirriya, yesterday; today was James’ turn.

            There were several dolphins at first, which is always difficult, both for the observers (Eric) trying to identify everybody, and for the scribes (us undergrads) who have to write down which dolphins are there every minute, on top of the other information. But our focal started traveling consistently with two other dolphins after the first hour and a half of the three-hour follow, and things calmed down. We were out east and the water was absolute glass. Other than the time when the pearl farm pontoon came by and it took us several minutes to relocate our dolphins, things were quite calm. That is until about 20 minutes before the end of the follow, when off in the distance we saw the reason our dolphins had changed direction: a giant group of dolphins, heading to meet our little group halfway.

Photo credit: Madison Miketa

            James steeled himself for lots of writing, but there were so many dolphins that when the mutual join between groups was finally made, Eric had me pull out the second camera and start shooting along with Madison, to try and get as many fins on film as we could. There were more than 30 dolphins present now—by far the largest group I had ever seen. We laughed at how wonderfully overwhelming it was, watching them all dart about socializing with each other as the swam around and under the boat. Their squeaks and whistles were so loud that we could hear them from above the surface, if we were quiet and listened. And when they would all snag together on the surface, resting—it was incredible, how many of them there were, just hanging out in the glassy, sunset-tinted water. And when they leapt, now and again, Madison and I clicked our cameras like demons, trying to catch them in action. Even when the follow was over and we began heading back into the sunset towards Monkey Mia, we glanced back at the group over our shoulders until we could see them no more.

Photo credit: Chloe Cavanaugh

First Day on the Water

            

The first post in our field blog series is coming to you from undergraduate student Chloe Cavanaugh, who is out in Monkey Mia with Janet Mann, Eric Patterson, graduate student Madison Miketa, and fellow undergrad James Davis. 

6/10/14

Chloe Cavanaugh

            We went out for the first time two days ago, and were almost immediately welcomed by one of the notorious beach dolphins, Nicky, as we headed out of the mooring area. She swam right up next to the boat, practically grinning back at us undergrads who were still stunned to see a wild dolphin so close.

            After we parted ways with Nicky, we headed out to Red Cliff Bay, the area just west of Monkey Mia and her flats. Eric went through the typical first day boat safety rules with us, and then before he could finish saying “now everybody look for dolphins,” we had spotted a couple traveling four hundred meters away. As we headed towards them I took down the starting time in the day’s first survey: our field season had officially begun.

            This afternoon the sky still held the threatening thunderheads whose wind had kept us off the water this morning, but now the glassy water reflected them like a molten mirror. We were again greeted by Nicky and her calf, Missel the instant we got out on the water. Nicky, always on the search for a free lunch, was boat-begging, while Missel’s bowriding allowed us to see she had the aptly named “black spot disease.” We could see black spots on her head and dorsal fin as she wiggled and turned just beneath the front of the moving boat.

A couple hours later, through my strangely sepia-tinted binoculars, I, like everyone else, scanned a side of the boat for any dolphin activity. Suddenly, we alerted to a black blip of movement where the horizon bled into the sky. All squinting with concentration, we stared until the movement could be confirmed by repetition: a dolphin dorsal fin breaking the water’s surface. Two kilometers away, we identified our first sponger of the day and season: Demi. Almost immediately after that survey was completed we came across our second: Bytfluke. As we were all silent, motor off, listening for the breath sounds that would indicate she had come up from a dive, she made us all jump by loudly surfacing right next to the boat, with a basket sponge fit snugly on her beak like a prickly ice cream cone. Seeing her mere feet in front of me, I realized the photos of spongers, tough as they are to get, hardly do the real-life version justice. 

Photo credit: Madison Miketa