Sunday, December 16, 2012

Lekking GWS? Yeah, Right!


This is lekking.



These examples probably not as there is only one male.
But it's fascinating footage, so there.



So what is this all about?
A lek is a gathering of males, of certain animal species, for the purposes of competitive mating display. Leks assemble before and during the breeding season, on a daily basis. The same group of males meet at a traditional place and take up the same individual positions on an arena, each occupying and defending a small territory or court. Intermittently or continuously, they spar individually with their neighbors or put on extravagant visual or aural displays (mating "dances" or gymnastics, plumage displays, vocal challenges, etc.).
So this is an aggregation of males showing off in a competition, allowing females to compare and then choose what they consider to be the most attractive partner. Alternatively, weaker males may tire faster and the females may end up mating with those who endure the longest.
Often the result is that only a small percentage of the males will mate with a large percentage of females, thus eroding genetic diversity and resulting in the Lek Paradox, see the same Wikipedia link.

Sal Jorgensen believes that he has discovered lekking in GWS.
According to him, the GWS males aggregate in the SOFA and then engage in rapid oscillatory diving, or ROD in order to find and/or convince the females to mate with them.
Nice synopsis here.

I say this is total baloney, and this is why.
This is the map of where the ROD happens - yellow dots.


Right.
Correct me if I'm wrong - but this "aggregation" would be happening in an area measuring about 8-10 degrees (60x8 - 60x10 nautical miles) on each side, i.e., conservatively, an area of 230,000 square nautical miles!

And this would be comprising how many GWS?
The same Jorgensen has co-authored the paper stipulating that there are only 219 adults and juveniles in central California and approx double that in the whole of the the North-East Pacific including Guadalupe.
I believe it's crap - but let's take him at his word.

So there.
I think it's fair to assume a ratio of 4:1 of juveniles/sub-adults to sexually mature adults, meaning that there are only approx 88 adults of which let's assume 44 are males and 44 females. Let's further assume that all the males are always horny and are willing to travel for some hanky panky - makes one male every 5,200-odd square miles! I mean, seriously: does this correspond to a gathering as per the above definition?
And there's more than that: the females have a two-year cycle and thus the number of available females would be only approx 22!!!

Chances of  a female encountering a male?
And if so, chances that evolution would select for this astounding migration and according expenditure of energy only for mating?

Anybody who has perused Domeier's GWS book knows that the SOFA features several potential prey species, foremost of which Cephalopods.
For the pregnant females, it also constitutes a stepping stone for traveling further to Hawaii where  the warmer water may favor the development of the embryos - and where (that's me speculating) there used to be another readily available energy-rich food source in the form of the Hawaiian Monk Seal - now depleted but likely much more abundant when these migration patterns may have originated.
Sal's males are likely to be oscillating in order to catch some elusive Squid that aggregate in the SOFA, e.g. attacking the school of Squid from below, as they do, only to dive back down for a further attack (yes I'm of course speculating!) - as very much acknowledged in the weasely part where he does not make any strong statements but calls lekking merely a hypothesis warranting further testing!
Yeah, right - but shouldn't a hypothesis be at least plausible?

And Domeier?
He obviously assumes that mating occurs in the known hotspots Farallones and Guadalupe where both males and females aggregate (Chapter 16: A New Life-History Hypothesis for White Sharks, Carcharodon carcharias, in the Northeastern Pacific) - which considering the numbers makes much much more sense! That's what I call a gathering!
And maybe, there is lekking there - remember that the males often feature wounds that are being attributed to brawling, i.e. sparring individually with their neighbors!

Plus, there is this.

Gill Raker - source.

These would be fresh mating scars.
This is commonly observed on female GWS at Guadalupe and from my own experience, it is a strong indicator that mating has occurred in the proximate vicinity. Granted we haven't observed GWS - but we have now witnessed the near-miraculous healing of mating scars in Tigers, Bulls, Sicklefin Lemons and Grey Reefs, and the healing time has been 2 weeks, maximum!
How does that dovetail with the fact that the females leave the SOFA weeks to months after the males - or are we to believe that after having made their choice in the SOFA, the females recognize the successful suitor weeks later and mate with him in Lupe?

And there may be another clue.
Wheres some pelagic Rays like the Mantas and Eagle Rays mate on the fly in mid-water, all other Elasmobranchs I've witnessed (Shovelnose Guitarfish,  Scalloped HH and Reef Whitetip in person - Nurse and Lemon on video) have a competitive mid water phase where several males try to latch on, after which the female stops struggling and sinks to the bottom with the successful male inserted. Copulation then happens on the bottom and lasts several graphic minutes.
Assuming this is the case in GWS - wouldn't copulating close to an island make much more sense than in the SOFA where the animals would sink forever? And is it possible for telemetry to detect that behavior?

Anyway.
I think Sal must have been sniffing glue when he came up with this - and shame on the reviewers for having approved of that ludicrous nonsense!

But of course this may not be merely about research.
Sal is very much one of the researchers "associated" with the Junior debacle - so may this be nothing more than another attempt to gnaw at Domeier's ankles?

Honi soit qui mal y pense!

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