Geoscience Reference
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by sitting on the nest, and then they feed and defend the hatchlings.
Because both crocodiles and birds care for their young, it is logical to
infer that they inherited this behavior from their common ancestor.
Furthermore, because this ancestor was also the ancestor of the
extinct dinosaurs, most scientists agree that most dinosaurs must have
provided their young with some kind of parental care. Based on our
observations in the egg quarry at Auca Mahuevo, we ruled out the kind
of parental protection in which parents directly care for their own nest,
but less elaborate kinds of parental care may have taken place.
Although it is impossible to prove, the sauropods from Auca Mahuevo
could have communally guarded the whole nesting colony. Adults may
have patrolled the periphery of the nesting area to ward off potential
predators. We will never know for sure, but it seems unlikely that the
eggs were left to the mercy of the fearsome predators that must have
roamed the region at that time.
The quarry was also useful in documenting the spatial relationships
between individual eggs, although it was not large enough to provide
a lot of data on how the clusters were distributed across the nesting
site. For that, we would need to document the position of clusters
across a larger area. The flats where we had first discovered eggs, the
better part of a mile away from the quarry, seemed to be the best place
to do that because the eggs and clutches were weathering out on a
large, relatively flat surface.
So Luis, Frankie, and Gerald Grellet-Tinner had returned to the flats
and surveyed a larger grid in an area that seemed to contain a repre-
sentative number of clusters. The rectangle that they laid out was
about sixty-five yards long and thirty yards wide, with the whole area
encompassing about two thousand square yards. The surface of the
area was fairly flat. The difference between the highest and lowest
point within the area was about two feet, which was not much more
than the thickness of one clutch, so we assumed that only one layer of
eggs was present. Within the mapped area, we found seventy-four ran-
domly distributed egg clusters that we assumed represented distinct
clutches. In a couple of spots near the middle of the area, clusters were
packed together rather densely, only two to four feet apart from one
another, but throughout most of the area, clusters were separated from
each other by at least nine or ten feet. To double-check our observa-
tions, we constructed and mapped a second grid about three hundred
