The Tyrannosaur Chronicles by David Hone

Author:David Hone
Language: eng
Format: epub
Publisher: Bloomsbury Publishing

A nested development

The dinosaur nests that we know of were relatively simple affairs, and not the complex interleaved vegetative structures of most modern birds. Roughly circular scrapes were excavated in the ground, and these may have been lined with loose leaves or similar to provide some protection, moisture and heat from decomposition. In short, the nests were generally more like the nests of alligators and crocodiles than those of most birds. However, some later theropods did sit on their nests as birds do,2 and they may have used their feathers to help protect the eggs or newly hatched baby dinosaurs, and of course to help keep them warm.

Dinosaurs, including tyrannosaurs, probably exhibited some form of parental care over both the eggs and the newly hatched young. A few birds have all but eliminated parental care and look after the eggs in the nest, but not the hatchlings, which fend for themselves as soon as they hatch. However, this approach is very unusual, and all crocodilians and the rest of the birds look after both the eggs and the newly hatched youngsters. They may do this for as little as a few weeks, or a year or more, but there is generally some care from at least one parent (typically, but not exclusively, the female), and often both. There are a number of dinosaur fossils that appear to include preserved young juveniles in the company of adults, which may represent parents living with their offspring, and the interpretation is reasonable as this is what we would expect.3 Still, given the lack of available data, this is about as far as we can go. All of this is probably true for tyrannosaurs, but the exact degree and extent of any parental care is hard to determine.

Naturally, passing on your genes and raising the next generation is a key part of the life cycle of any organism, so it’s not surprising that animals attempt to maximise their reproductive potential. Part of this comes down to ensuring that they have a good mate: they don’t want to be stuck with a partner who is sickly or a poor forager. Animals go to great lengths to ensure that they mate with an appropriate partner, and as explained below this can lead to some interesting evolutionary effects. It also means that they need to adapt their reproduction strategy according to the prevailing conditions. As noted above, animals typically go for either larger numbers of offspring with little investment in each, or few with considerable investment, but there are further subtleties to this and interesting possibilities for dinosaurs.

With egg size limited, dinosaurs produced more eggs for their size than might be expected, but if they were investing heavily in their offspring they may not have laid as many eggs as they could. Looking after babies can represent a huge amount of work: just look at how manic small birds are when their eggs hatch, with parents returning to the nest every few minutes to cram food down the gullets of their offspring.

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