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Re: Makos on TV


> Date:          Tue, 12 Aug 1997 20:18:55 -0400 (EDT)
> Reply-to:      bz050@freenet.carleton.ca
> From:          bz050@freenet.carleton.ca (Ben S. Roesch)
> To:            Shark-L@raven.utc.edu
> Cc:            dinosaur@usc.edu
> Subject:       Makos on TV

> 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...