Length: 70 feet
Height: 15 feet
Weight: 30 tons
- Adult (both sexes): A gray color with darker gray markings on the back.
- Juvenile (both sexes): Lighter gray body.
Any low-growing plants it can find.
Wide open spaces to accommodate its size.
Medium-sized groups of animals close to other herds of sauropod and smaller ornithopods.
A long-necked sauropod, Apatosaurus is the largest animal on the island, after Brachiosaurus and Mamenchisaurus. It is a heavily-built animal with forelimbs slightly longer than its hindegs, a small head in comparison to its body-size, and jaws lined with chisel-like teeth. The whip-like tail is long and tapered at the end, held clear off the ground. The long neck is relatively stiff and cannot be lifted much higher than shoulder height.
Apatosaurus' tail has multiple functions. It is mainly used to counterbalance the animal’s long neck and most famously, it is used as a weapon against predators. However, the tail is also used as a an important communication device. In a herd, members keep in constant contact with others in the group with their long tails; occasionally whip-cracking and using the resulting breaking of the sound barrier to communicate over long distances with other Apatosaurus. Mostly, the tail serves as a visual communicator; with individuals constantly waving their tails in the air to remind others of their location thus helping to keep the herd together. In addition, Apatosaurus touch the backs of other individuals at close range with their tail tips almost continuously, seemingly to reassure and comfort others with their presence.
The tails of male Apatosaurus are also used as a device to attract females. During the breeding season, males can be easily distinguished by the ends of their tails, which develop red rings as they become flushed with blood. Males will wave their tails around in front of a receptive female, accompanied by deep-frequency bellows and stamping of their feet.
Competing males will attempt to warn the other off using this method as well, although in extreme circumstances fights may break out, involving each male standing side by side and attempting to use their bulk to push and shove against one another in tests of strength. Apatosaurus breeding season coincides with the breeding seasons of the other two sauropod species of Isla Sorna, occurring outside the breeding seasons of hadrosaurs. After mating, gravid females will travel single file into the Meadow, laying their eggs en mass on the edge of the forests bordering the Lower Mountain Range. The females will then quickly move away, being far too large to remain without risking stepping on the vulnerable eggs and young. A few of adults may remain on the outside of the Meadow, discouraging predators from entering. Although hundreds or even thousands of eggs may be laid between the three species, few survive to hatch and even fewer hatchlings survive into reach their full size owing to the abundance of predators. Like baby turtles, the sauropodlets will instinctively make a beeline for the relative safety of the forests, remaining together in mixed species crèches. Juveniles grow rapidly, and upon reaching adolescence they will move out of the forests onto the open grasslands in order to seek adult herds to join.
Even though the full-grown adults have little to fear against predators due to their immense size, the younger individuals are vulnerable to predators such as Allosaurus and Tyrannosaurus. The young remain in the center of the herd while the much larger, older individuals remain on the outside - providing a barrier to hide and protect the vulnerable juveniles from predators. The adults protect themselves by lashing out with their whip-like tails, inflicting painful, discouraging blows.
Apatosaurus produce distinctive bellowing and whinnying calls. Herds are often followed by packs of Allosaurus.