Friday, November 18, 2011

Florida - the Bull Shark next please!

Badass Bull, by Sasha!

From a message by Doc.

The way I see it the bull shark is the true top predator in the Eastern coastal zone (New York to Brazil).
This shark is a perfect example of adaptive radiation where one species finally evolves to feed on member of closely related species. As THE top predator bull sharks must play a strong controlling role on its prey and exert a significant stabilization factor as well as supporting biodiversity.
For all these reasons and more the bull shark should be protected even more than the other LCS sharks like hammerheads, lemon sharks, reef sharks etc and rays---species that bulls prey on and to some extent control.

One of my favorite standard question to the many visiting Shark researchers is, why do you think evolution has selected for Bull Sharks to look like they do. Surely, this enormous non-hydrodynamic bulk must be a disadvantage - so where's the advantage?
Inevitably and after much pondering, the answer turns out to be, in my rather liberal interpretation, because this is the ultimate badass Shark!

Bulls are by no means specialized predators of Elasmobranchs, see their incredibly diverse diet here - but they do prey on Sharks and with that stature and formidable dentition, they are very well equipped to do that with overwhelming power and devastating results and thus at minimal risk to themselves. In brief, by looking like they do, they can prey on whatever they please - and they certainly do!
It's good to be the Bull! :)

Yes ours are quite timid and really, totally endearing - but let there be no doubt about what they could do if they wanted to!

So here's my wish for Florida.
Now that the less problematic species have been successfully protected, could somebody please start advocating the protection of the true apex predator? Yes it will politically difficult, not least because Bulls have a terrible reputation because they do sometimes kill people - but as Doc says, they are the ultimate regulators and if anything we always profess about trophic cascades is true, they do deserve special protection.

Any takers?


jsd said...

'Surely, this enormous non-hydrodynamic bulk must be a disadvantage - so where's the advantage?'

- I'm not so sure. After all, most submarines have blunt fronts and a great deal of work must have gone into the designs. The secret, surely, is in the relationship between resistance/drag and the ability to pack in more muscles into the basic form hence selecting for bulk...But then I am assuming a healthy bull shark's bulk IS mostly muscle.

DaShark said...

... sure, as is a comparatively sleek Mako or Grey Reef!

The most consistent interpretation I hear is that the benefit of the (expensive) bulk is that by being so big and powerful, a big Bull can overwhelm & dispatch basically anything down there, making it the ultimate apex predator as per Doc's comment.

But of course that just one plausible, tho largely untestable hypothesis.
Maybe the Bull dudes just happen to like big Bull mamas, thus providing for the according selective pressure!

Questions questions... :)

jsd said...

I remember a fisherman telling me once that he saw a bull shark feeding on a tarpon in shallow water. It charged the tarpon and slammed into it before feeding (whether it bit when it hit I don't know).

If the story was accurate, another possibility is that the foreward bulk acts as a shock absorber for a method of 'charge' feeding that we know nothing about.

DaShark said...

Actually, my always erudite friend, I think that it IS known: Bull sharks have been known to use the bump-and-bite technique to attack their prey. from Wikipedia.

Also, check here: ramming with snout (mouth closed) has very much been described as typical agonistic behavior of Bulls - and I can certainly attest to that! :)

jsd said...

Thanks for this: the holes in my memory seem to be growing. Perhaps the name 'bull shark'is more apposite than we have realised if they are happy to charge and butt.

Several of the photos of displaying sharks in Aiden's paper are mine. Photo M was at Walkers' Cay. I T-boned the bull in shallow water because I was looking through the fisheye lens of my camera and didn't realise how close I was (almost touching - duh!). It appeared to lower its pecs somewhat (difficult to judge because of the fisheye distortion) but also opened its mouth. Have you seen similar?

DaShark said...

No, not really.

I, resp my housing, have been bumped many many times - but always mouth closed!

When excited/apprehensive, they also visibly tense up and swimming becomes a tad more jerky.

But when it comes to lowered pecs, like in probably most other Sharks, it is not a threat display but merely due to the fact that they are making a tight turn.

IMO, the lowering of the pecs is way over-rated.
When combined with arching of the back is only really diagnostic for Grey Reefs.

jsd said...

I agree with you about those lowered pecs!