August 8th, 2009
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Concerning old friends and site fidelity
Over the years we’ve written a lot about site fidelity: the strong tendency of honu to return to the same reef and often the same exact spot, year after year. We presented a poster at the 2000 Sea Turtle Symposium on the subject, and we make several references to the concept in our book. Yet this faithfulness is not absolute. Some honu, particularly mature males, are around for a few summers and then—not. We sight others every summer once we’ve met them, and there are those who are around for a while, absent for a few summers, then show up again.
Some absences are easily explained. Mature females migrate to nest every second or third year (see the poster). Usually when this happens our friend George Balazs, who heads the Marine Turtle Research Program in the Central Pacific for the National Marine Fisheries Program (George needs a shorter title; I suggest Head Honu Honcho) notifies us. Every season we send him a watch list and the monitors at East Island in the French Frigate Shoals let George know which ones show up. We can’t track males this way because males aren’t tagged, and although they might haul ashore to bask while at East Island, the monitoring team there don’t normally tag or mark them.
When we see a male at Honokowai with a carapace that has little algae growth, and who has whitish scars on his flippers and neck, we assume he’s been mating at the Shoals, but of course we can’t be sure. Nevertheless, such indicators do explain an absence: he’s been off mating somewhere. This brings us to Zeus.
For many years, we saw Zeus every single summer. We thought he probably wasn’t mating, since he never bore scars. (The scars result from wounds inflicted by other males as they attempt to dislodge a male who has successfully mounted a female.) Then, a few years ago a friend of ours sent us some pictures he took at Honokowai in March, showing a mating pair of honu. We easily identified the male as Zeus. So we thought, “Hmm. Zeus is clever, he doesn’t make the long swim to East Island, he just courts the ladies at home.”
Except… this week we saw Zeus for the first time this summer. He swam right by us at a leisurely pace, allowing Ursula to get plenty of good video.
As you can see, this time Zeus has several mating-type scars. It’s likely that he got those at East Island, where the competition for females is tough. Besides, the scars are pretty fresh, and most of the females who are receptive are there, not here. So the Big Guy probably does migrate sometimes. His mating habits, however, are not the only reason I mention Zeus.
Zeus is an excellent example of how our, i.e. Ursula and my, perception of site fidelity is inherently incomplete. All our observations on the topic are drawn from coverage of what is really a pretty small area. We’d be naive to assume that it coincides with the range of any particular honu, let alone an entire ohana. It’s true that some honu show up in that tiny observation area year after year, but it’s also true that some honu drift in and out of it. We are convinced that they still live at Honokowai, just not in the limited range we cover in our dives—not to mention that we are in the water for only about 5% of a given day.
Zeus used to hang around places that were within our dive site, so we saw him frequently. The spots he preferred changed gradually, though. At first we found him most often at the Turtle House. Later, we saw him so frequently at a place on Reef 2 that we named it Zeus’s Lair. Then, when North House was active, we encountered him there. So when he went missing for a whole summer a few years ago, we were concerned but we always felt that he’d just started hanging out somewhere outside our range.
Since then our Zeus sightings have confirmed our suspicions. We usually see him once a season, no more. It’s all we need. Sure, we’d love him to move back into our dive range, but we’re just happy to know he’s still out there, safe and living his life at Honokowai. Best of all, Zeus gives us confidence that most if not all of the honu that we used to call regulars but who we don’t see anymore are somewhere out there, safe and sound just like he is.
Seals & eels
Something interesting happened a few days ago—a monk seal dropped by for lunch. Hawaiian monk seals are endangered (reports say there’s only about 1200 of them) and most of them hang around the French Frigate Shoals. We’ve been lucky enough to see one around Honokowai a few times, but never when we’re in the water. The first time was back in 2005, when we were out on our kayak and spotted a big head that was neither honu nor human.
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The seal—we don’t know its sex so let’s call it a she—had caught an eel and was gleefully slapping it against the water. I gather this is how they stun/kill their prey, because while it looks playful for the seal, the eel winds up chewed and swallowed.
I’ve seen a seal (presumably the same one since there just aren’t that many of them) playing with an object that wasn’t food. It was a couple of summers later, and I spotted her from our lanai. She was tossing and chasing something white and round and definitely not food. Eventually she gave up and left it to float away. but she showed that she’d play with something floating in the water.
At the time, none of our cameras had a zoom capable of capturing anything worth showing, but then last year (2008) we got a Panasonic SDR-H18. This little gem has a 32x zoom with fantastic image stabilization, so when we spotted our friend the monk seal diving repeatedly for something, we grabbed the camera and got this video from our lanai:
For some reason I never worked it up to post on YouTube, but then last week, the seal came by for a repeat performance. Fortunately, this year we bought a Panasonic SDR-H80, which is smaller and cuter and has a whopping 70x zoom! The image stabilization is amazing, but even on a tripod it’s difficult to zoom right in, track a moving subject, and get an image that isn’t a bit shaky. Nevertheless, we got more video of that rarest of Hawaiian sea mammals, the monk seal, enjoying another eel meal.
Good news from Kuamo’o
Readers of past summer summaries know that we have an alternate dive site that we call Kuamo’o. That’s not it’s real name, but we call it that because the site can only be reached by crossing private property. It has a large honu ohana, and we were invited to dive there a few years ago because many of the turtles had tumors. We were asked to check them out and try to determine how they were doing.
At the time, the tumor epidemic at Honokowai was slowly waning. We saw fewer honu with tumors. Many of the turtles we sighted we knew had recovered—regression cases. Kuamo’o was disturbing, in the sense that it was like stepping into a time machine and visiting Honokowai 5-10 years earlier: most turtles had tumors and there were many severe cases. We could comfort ourselves and the concerned residents at the location with the knowledge that we had already established that many turtles would recover.
This summer we were late going to Kuamo’o because of the constant swells throughout July. Kuamo’o is shallow and sandy. While it is a spectacular dive in the right conditions, the smallest wave action stirs up the sand and turns the water murky—not really an enjoyable dive.
Every year since we started diving there, we’ve placed a temperature logger for George Balazs, so we were just waiting for a few days of calm in a row that would let us retrieve last year’s logger. Finally, on July 31, we got the conditions we wanted. Sort of.
It had been calm but the water was still pretty messed up. Usually, on a Kuamo’o dive we’ll see 25-30 honu, but not this time. A resident assured us that there were as many turtles as there always had been, but I guess they had better things to do the day we were there. We did see 10-15 turtles. While that’s not a big sample, what we saw was encouraging.
For the first time, we did not see a lot of tumors. Usually, most of the honu we see there have some tumors, and until now we’d always see at least one extreme case. That didn’t happen this time. It was a lot like Honokowai: some small tumors on some turtles, and nothing serious on any of them. Some of them appeared entirely tumor-free, although if we checked the chances are high that those are regression cases.
Without several dives, it’s not possible to say whether the epidemic has faded from Kuamo’o in the way it has from Honokowai, but that’s what we’ve always expected. Our single visit certainly gave us reason to feel encouraged.
Oh, and we did retrieve George’s temperature logger.
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Our summer gem
Who would deny that the cutest of any species are the youngest? Maybe it’s Nature’s way of protecting the most vulnerable and promising individuals, or maybe it’s just humans who automatically find youngsters endearing. At any rate, there’s no doubt that the little jewel of a honu that we’ve featured several times now has completely charmed us. If the reader responses we’ve gotten so far are typical, we’re far from alone. I wanted to give you an idea of just how small this little turtle is, so here’s a photo with Ursula in the picture for comparison:
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We see this beautiful young honu on almost every dive, always in the same area, never intimidated by our presence. We try not to pay too much attention but it’s hard not take pictures and just enjoy the cuteness of the little turtle—especially when she (or maybe he, who knows) sometimes seems to be acting out just to get our attention.
For example, sometimes when she returns from getting air, instead of returning to rest underneath the coral head she lands in the sand and flings it about. That’s what Ursula is recording, and that’s what she’s doing in my favourite pic of the week.
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Update, August 11
Ursula’s latest blog is honu-related. See City of Mississauga’s “Trust, Quality, Excellence” pushes MISSISSAUGAWATCH straight over the Edge –and The Muse escapes to Mickey Newbury.