Mating Reef Mantas - Video!

Source.

This is great.

I've always wondered how the males manage to hold on to the female in order to get the necessary leverage for inserting the clasper, and here's the answer.

Enjoy!

Reef Mantas off Eastern Australia - Paper!

Click for detail!

The paper is open access.

Read it!

Great stuff.

And, it clearly illustrates how behavior is being mediated by the environment.

But we knew that already - right? :)

Manta Ray in California!

What species is this?

Wow wow wow!

Have you seen this post?

Now, I know nothing about kelp diving and what to expect there - but it looks like the Niño is driving all kinds of tropical Fishes north, so having a Manta migrate north from, say, their known range in Baja/Socorro doesn't seem like such a big deal.

But watch the video.

See what I mean?

That's not one of the Pelagic Mantas that are ubiquitous on the tropical West coast of the Americas - that's a Reef Manta! Mantas have been shown to change color, but that apparently does not apply to the ventral side - and if you look at the comparative pictures, that Manta is definitely not featuring an uninterrupted dark terminal band but is instead featuring coloration that is diagnostic for Manta alfredi!

Correct?

Check out the distribution of the Reef Manta.

See? No records for the Eastern Pacific, meaning that this is either a massive range extension, or that this is a straggler that must have swum over from either French Polynesia or more likely, the Hawaiian Islands - and this in a species that is generally believed to be highly coast-oriented!

Amazing!

Spatial Behavior in Elasmobranchs - Papers!

OCEARCH tracks in SA - so far, highly ambiguous!

Interesting!

I've been remiss in not posting about several new papers.

This one by, among others, (the proudly left-brained, and obstinate) Michelle Wcisel, describes the movements of GWS in the Dyer Island and Geyser Rock system near Gansbaai and observes that they differ substantially from the GWS movements in Mossel Bay. As a possible explanation, it observes that the former Sharks are largely sub-adult to adult (= seasonal hunters of Mammals ) whereas the Mossel Bay Sharks are predominantly juveniles that feed predominantly on bony Fishes and Cephalopods.

Offical synopsis and great infographic here.

This one examines the abundance and sexual composition of GWS in Gansbaai in relation to the season and ENSO, and comes to the conclusion that females appear to favor warmer water whereas males do the opposite, possibly owing to competitive exclusion by the larger female conspecifics.

And this one by, among others, Tiger Shark supremo Yannis Papastamatiou describes the movement patterns of Reef Mantas at Palmyra Atoll with its two immediately adjacent lagoons. Whereas most Mantas in one lagoon alternate between lagoonal and offshore habitats, those in the other lagoon appear to be much more resident, possibly owing to the different hydrology and/or capacity of the lagoons to provide for adequate nourishment.

And the take-away message of it all?

What once again strikes me in all those papers, is how behavior is being mediated by the environment (= climate, geography, habitat but also occurrence and/or migration of prey etc) but also by factors like gender, age and of course, individuality - and this all within one and the same species!

And if Michelle and Yannis can show significant variance across the smallest of geographical areas, and this within one single population - isn't it only logical to expect even bigger differences between distinct populations that are completely separated both genetically and geographically?

Definitely a big yes for Tiger Sharks - and the GWS?

Even discounting the Fischer factor, it seems to me that all those many comments about those tagged GWS are tacitly assuming that all GWS must necessarily follow a life cycle that is analogous, if not identical to what has been documented by Domeier for the Guadalupe population.

But with the above in mind, is that even plausible?

Take the Atlantic.

Its hydrology (think: Gulf Stream), climate and fauna are very different from that of the Eastern Pacific. Other large Sharks like Great Hammers and Tigers have been shown to migrate smack into the middle of the Atlantic, quite possibly following prey - so why not some of those GWS. Other, possibly younger GWS could be following the Bluefin into the Gulf. Consequently, the overall picture is much more ambiguous - incidentally, much like in South Africa with its ENSO-mediated interplay between the Benguela and the Agulhas!

Australia?

There are two genetically distinct GWS populations that both migrate to the Neptunes where they intermingle as they prey on Pinnipeds - meaning that barring the discovery of some highly sophisticated reproductive isolation mechanism, one would have to assume that they mate completely elsewhere. And if so, this would be very different from what is being postulated for Lupe where the Pinniped colony appears to act as a focal point for mating!

Or the Mediterannean GWS.
Much more restricted habitat and quasi absence of Pinnipeds owing to the extirpation of the Monk Seal - surely this must have big effects on both their diet and migration!

Long story short?

We should really refrain from resorting to those very broad generalizations when describing the behavior of those different Sharks. Instead, let's stick to the evidence that keeps reminding us that things are complicated!

Agree?

Reef Mantas in the Red Sea - Paper!

Reef Mantas or Giant Mantas? Source.

Very Cool.

Reef Mantas are shown to engage in deep dives during the night.

Apparently, they are mostly targeting Plankton that ascends from the deep at night - but the authors speculate that occasional very deep dives to up to 400m are not for foraging but instead, a more efficient way of traveling.

Synopsis here, open access paper here.

Enjoy!

Manta birostris or Manta alfredi?

The two Mantas - once you know what to look for, pretty unequivocal! Click for detail.

Cool!

Ever since Andrea described the second Manta, I've been looking for a user-friendly ID guide to reliably differentiate the Giant, or Pelagic Manta Manta birostris from the Reef Manta Manta alfredi. That was a major challenge when designing the posters and ID guides for the Great Fiji Shark Count where we finally decided to reference the two species and to say that holding them apart required specialist knowledge.

Well, here it is - finally!
It is hidden within the pages of Manta Matcher, the world's first global Manta Ray database. Here are the various pics, and should you want to find out more about the principal distinguishing features, you can find them right here.
Pretty unequivocal - no need for specialist knowledge after all!


And here's the video about that glorious discovery!
Enjoy!

New Manta Ray discovered!

Not even the most inveterate lover of toothy Apex Predators will escape the gentle charm of the beautiful and friendly Manta Ray, the more as it sometimes shares the same habitat as Sharks, like in Cocos, the Galapagos, Socorro and sometimes, even Shark Reef.

Like many of my fellow divers, I've often wondered at their massive range in size and coloration: quite small and lightly colored on the reefs of say, Yap and French Polynesia, much bigger and darker on the west coast of the Americas or in the cold waters around Komodo.
But despite the best efforts of the Taxonomists, even including illegal DNA sampling within Marine Protected Areas, no evidence could be found that the "Giant Pacific Mantas" were anything different than their fairer and smaller cousins. The difference in size and coloration was apparently merely due to environmental factors and nutrition. After all, the reason for the crystal clear azure water on coral reefs is its lack of nutrients which has forced corals to co-operate with algae; whereas in the Americas, the cold and dark Humboldt and California currents carry plenty of nutrients allowing for abundant plankton growth and thus, a much larger size of plankton feeders.
Thus, scientific wisdom had it that all Manta Rays belong to one and the same single circumtropical species of Manta birostris.
Until now it seems.
Now and again, there would be reports of truly whoppingly gigantic individuals, reputedly with wingspans in excess of six meters, and this mainly from coral reef habitats in the Indian Ocean. With the exception of a possible encounter in the Seychelles many many years ago when I was green and impressionable, I never saw such an animal, and this despite of hundreds of sightings - so I quicky started filing those reports under the category of urban legends.

Well, it seems that as so often, I was dead wrong.
It now appears that the behemoth not only exists, but that it even represents a new species!
Keep in mind that discovering such a large marine animal, and this on reefs and at depths teeming with recreational divers is nothing short of miraculous! The last such marine discovery, after the two Coelacanths, was the Megamouth Shark and those animals are found in deep-water and pelagic habitats people like us would never vist.

Here, a massive ray with a wing span of up to 8 meters (!) would have gone unnoticed but for the tireless efforts of University of Queensland's PhD researcher Andrea Marshall and her Manta Ray & Whale Shark Research Centre.
Situated in a small village on the coast of Mozambique, people in the know tell me that it's as remote and lonely as it gets and subject to regular natural catastrophes as floods and cyclones. To persevere in such an environment is a testimony to her dedication and some would say, obsession - but what a wonderful vindication to be able to come up with such spectacular results!
This is like discovering a new species of African Elephant in the middle of Kruger National Park after years of it perambulating in total impunity from detection among thousands of safari tourists.
Truly, a remarkable feat!

Apparently, the new species is much rarer and much bigger than the "usual" Manta and lives a migratory, more pelagic life in contrast to its more resident and reef-bound cousin. Alas, like in the case of the migratory pelagic Sharks, and Fish, it is the object of substantial fishing pressure owing to the difficulties in establishing collaborative and coordinated conservation and management practices in such a large and unregulated environment.

You can watch Andrea talk about her discovery on this webpage of her proud sponsor, the Save our Seas Foundation (Video #1) and you can learn more about her research on her Manta Ray webpage. With a possible third species in the works, the future looks bright indeed!

Paper here!

Be amazed and enjoy!