Warm-blooded or cold-blooded; Implications for climatic change and extinction.
Even though dinosaurs are from the class Reptillia, which are cold-blooded animals,
there is evidence that might be warm blooded.
Evidence;
Haversian bone associated with some dinosaurs: - This is a dense form
found in birds and mammals, both are warm blooded.
Volume to Area ratio in large dinosaurs:- Large dinosaurs would find it difficult
and slow to warm their bodies in cool conditions.
Internal regulation of temperature require a higher intake of food and makes
species prone to starvation, due to the inability to slow their metabolisms.
Predicted running speeds and distances covered by some dinosaurs , suggests
the need to be able to metabolise energy quickly, i.e., be warm -blooded.
Large modern ectotherms (cold-blooded) are confined to within 20 degrees of the
equator.
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With reduced temperatures, resulting from climatic change dinosaurs could not have
remained active through "winter" (Dunham and others,1989), hence, migration would be
necessary. This is based on the assumption that dinosaurs were cold-blooded.
Boys, Girls and Eggs !
Sex determination in reptiles is highly sensitive to the temperature at which eggs
are incubated (Paladino and others,1989).If an imbalance in sex-ratio alterations
occurred in dinosaurs, as a result of a rapid change climate temperature, then this
would have been a strong influence in their demise.
Conversely, dinosaurs may have
had change their habit in order to maintain the required temperature of incubation.
i.e. restricting nesting to the summer months, which would change the overall
reproduction cycle.
Horner and Weishampel(1988) suggested that hadrosaur hatchlings remained in or near
their nests for several months after hatching. Rapid growth at the end of the summer
was necessary in order to be strong enough to migrate. Therefore, if the nesting and
growing seasons was put back in time, to maintain a (1:1) sex-ratio (i.e. equal males
and females),by say two months this would have result in; less chance of a juvenile
surviving the first migration or would be left behind by the adult population, and
perished.
How could you leave a cute dino-babe like this ?