Amazing Manta Ray!

Amazing indeed - enjoy!

Amazing Manta Ray🐳🐬 pic.twitter.com/URylHUYgaw

— Ocean diversity (@Oceandiversity2) November 7, 2019

Manta molesting - Videos!

Source.

Whoops.
Watch = click here or on post below!



The question being, who is molesting whom!
May this be some defensive maneuver, or is the Manta simply having fun like they often appear to do?

Questions questions!
And lest you thought this is strictly a one-off: here's another one from 4 years ago - story here!



Anyway, 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? :)

Color Changes in Mantas - Paper!

These are birostris, but the same is being described for alfredi and cf birostris. Click for detail!

Who would have thought!

Turns out that Mantas can change their color.

And this not gradually over a long period of time but instead, within minutes! According to this paper, coloration may indicate their mood but perhaps also be linked to communication - whilst making visual species ID just a tad more difficult!

Fascinating - and great observation by Csilla Ari!

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!