PARENTAL CARE

---

In 1991 Lambert suggested that the question of dinosaur temperature regulation might be addressed from the point of view of parenting behaviour. His argument starts from the premise that post natal care of the young, such as foraging for extra food, is an energy expenditure that cold-blooded animals, with only short periods of sustained activity limiting the time and distance over which foraging can occur, simply cannot afford. Using the Maiasaura nesting grounds as an example, he cites the evidence that the young spent a considerable period of time in the nest after hatching (badly fragmented eggshells indicative of repeated trampling, juveniles of different ages within the nest, poorly developed limb bone joints indicating limited locomotion of the young) to support the theory that the parent hadrosaurs were involved in foraging to provide food for their rapidly growing, nest-bound young, and that this behaviour was strong evidence against them being cold-blooded. He also notes that evidence from the second well documented north American nesting site of the hypsilophodont Orodromeus (now identified instead as the theropod Troodon) is much less clear, with eggshells relatively intact, no juveniles within the nests and well developed locomotion in the young. They still remained in the vicinity of the nest for a significant period, which may imply some dependence on the parents.
The evidence from this nesting site has since been challenged. It has been claimed that the bones found in the nest were all from embryos , and that joint development is far less critical for early movement than hip development which appeared adequate in the Maiasaura chicks. Currently this argument lacks support and most experts seem to concede parental involvement at this site at least.

References