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Re: dromaeosaurid intelligence



----- Original Message -----
From: "Marcel Bertolucci" <mbertol@terra.com.br>


> To the brain mass to body mass ratio matter, the question is: how
> far does it goes?

There has to be a lot more to it than just this. Take _Craseonycteris
thonglongyai_, the bumblebee bat. Once a candidate for smallest mammal on
Earth, adults weigh around 2 to 3 grams. I have no idea what percentage of
body weight the brain takes up, but even if we say brain weight is 1% of
body weight, we have 0.02 grams of neural tissue that is capable of highly
advanced echolocation (sound production, hearing and interpretation), social
behaviour (bats are highly social animals), significant spatial memory and
orientation ability, complex flight AND the various behaviours associated
with controlling a relatively complex body. Pretty neat stuff for such a
physically tiny creature, regardless of its brain to body weight ratio.


> This is
> strange to crocs, because they normally are territorialists and agressive
> with each other, mostly in feeding matters. This tolerance behavior could
be
> explained by the survival instinct, but not for crocs. Other question is
> that the male crocs accept female crocs in their territory in the mating
> season, but not other male crocs, as it happens in this case. Could it be
> the 'smart' sense of crocs working for their benefit?

Actually, the majority of crocodiles are highly gregarious and social, and
only a few species are considered territorial (eg. saltwater crocodiles) or
solitary (eg. dwarf caimans) - and then only as mature adults. Social
behaviour is vastly underestimated in crocodilians, and definitely never get
your information on crocodilian social behaviour from the Discovery Channel!
A large array of different behaviours have been recorded in crocodilians,
including their ability to produce a remarkable array of complex (ie.
combined) signals using visual, auditory, chemical and tactile cues.
Crocodilians also have a well-developed ability to learn associatively, able
to recognise any combination of signals (visual, auditory, chemical,
tactile) linked to events in both space and time. For example, Nile crocs
will move to particular locations at particular times of year to take
advantage of events (eg. migrations), and they hunt cooperatively. Pack
hunting behaviour has been reported in Cuban crocodiles, and all species
show complex parental care and short-term pair bonding in some. In
captivity, crocodilians can be trained to respond to specific signals (ie.
names) and commands. They learn such commands very quickly, sometimes after
only 1 to 2 reinforcement attempts through habituation, operant or classical
conditioning. Most zoological exhibits are now considering training their
crocodilians for management purposes (eg. moving into a holding area when a
bell sounds), and most people who work with crocs recognise their ability to
take advantage of routine opportunities. This is from an animal whose brain
weighs 0.005% of its body weight, although in hatchlings it starts out
relatively much larger (0.9% body weight).

I can't find it right now, but there was some work being conducted in Canada
on American alligators which showed they had a proportionally higher neurone
density in the cerebral cortex of their brains compared with certain other
vertebrates (quoted, but I can't remember so I won't make a guess),
tentatively suggested by the neurobiologist as a possible explanation for
their apparently high degree of complex behaviour relative to their brain
size. If I can relocate the notes I'll elaborate further.

Adam Britton