Makos on TV

[bz050@freenet.carleton.ca (Ben S. Roesch)]

I thought the show was pretty good overall, and here are some general
comments. Keep in mind I totally understand what people are saying about
Discovery focusing on entertainment too.BTW, this pretty picky!

-- First of all, I want footage of mako/marlin predator/prey interaction!
When they showed the marlin feeding on the fish school, I held my breath,
but unfortunately nothing came of that!

-- According to the show, Thorburn (sp?) noticed signs of intelligence
isharks in that they learned when they were going to be fed. Of course, 
doubt Thorburn needs reminding that learning behaviour is well documented
in at least some sharks (case in point-Eugenie Clark's studies with nurse
sharks).

-- Makos _do not_, relatively speaking, have big brains compared to their
body. In fact they have pretty small brains compared to their body. In
fact, blue sharks (_Prionace glaucas_) have bigger brains relative to body
size, but in the show they said it was very instinctive etc.! In any case,
makos _are_ "smarter" than white sharks (_Carcharodon carcharias_); i.e they
have a more developed telecephalon. The central nucleus of the dorsal
pallium (in the telecephalon) is known to play a part in visual
discrimination in nurse sharks, and the central nucleus as a whole
is believed to control complex behaviours and "multimodal sensory
integration". In carcharhinids and sphyrnids, the telecephalon is esp. large,
which seems to fit with their apparent complex social and territorial
behaviour. Sphyrnids in particular seem to have social systems based on
hierarchies and sex and size (the latter is exemplified by their schooling
behaviour - but I'm not totally certain on that. Also, I believe only a
couple of species school - I think the bonnethead hammerhead does for
sure). These complex behaviours likely rely partly on the ability of the
sharks to learn of specific individuals and landmarks, so the telecephalon
might play a role in this too.

(Should have started a new paragraph long ago!) 
Anyway, makos have much smaller telecephalons (and of course brains
relative to body mass) than either carcharhinids or sphyrnids, and white
sharks (closely relate dof course) have even smaller ones. In makos the
telecephalons comprise 37% of the brain's mass (can't recall what it is in
white sharks). In carcharhinids and sphyrnids, the % is 51 and 52,
respectively. These two shark groups are the real "smart" groups, at least
in human terms. OK, on to other things!

-- Warm blooded probably isn't the best way to describe a makos (or white
or Lamna sp.) physiology - I like "warm bodied" better. The retia mirabilia
(bunches of parallel arteries and veins) warm the muscles, viscera, brain
and eyes and there is evidence of thermoregulation (in white sharks, and
therefore probably other "warm bodied" lamnids), but I still don't think
this constitutes endothermy. Or maybe it does, I'm not sure! "Will the
real physiologist please stand up?" Incidentally, aren't alopiids "warm
bodied" too?

-- On the first mako, there appeared to be two stab-like wounds on its
ventral side, near the head....possibly wounds from a defending marlin? If
so, the shark is probably lucky it survived!

-- Overall the show was pretty anthropocentric, but I guess that's a given.

-- I'm not sure about the suggestion of makos moving in "loose packs." I
would assume there'd just be a bunch of them there to cash in on the
abundant food supply.

-- In the experiment with the electrified fibreglass fish, the mako made
no distinction. In white sharks, at least, electroreception is poorly
developed compared to the exceptional vision (and smell). So, I assume the
mako is like the white shark in this respect.

-- A question: have comparable "inteligence studies" been performed with
white sharks?

-- The footage of the mako attacking the moving bait was phenomenal. The
thing is so damn fast and agile I cna't believe it! 

-- "Makos are to sharks as humans are to primates" BS! That's ridiculous;
that honor (if you want to compare sharks in that way) would have to go to
a carcharhinid or a sphyrnid, for sure.

Well that's it for now...I've got to get home !

BTW, for more info on shark brains check out Demski and Northcutt's
chapter on white shark brains in Klimley and Ainley's "Great White
Sharks". I don't know the actual chapter or pages, as I don't have the
book here, but it's a great source fo info and further refs.

lates

ben...