The alarm call plays a loud warning cry that varies depending on the significance of the threat. In the case of the Parasaurolophus, it will play either a short honk for less threatening predators such as Velociraptors, a long, drawn out honk for moderately threatening predators such as a Utahraptor, and two long, drawn out honks for a large, threatening predator such as an Acrocanthosaurus. The alarm call will also alert anyone in your herd of the presence and type of threat you have spotted in the chat window in bright red characters.
Using the alarm call consumes 30 Ability Power. It serves no direct combat purpose as it provides no stat-based buff or debuff, but is highly useful for alerting nearby herd members of a stalking predator. In some situations such as during an intense storm, the visibility it provides can also be helpful given it highlights the marked player in bright, emissive red or purple. Successfully using the alarm call is a two step process. When right mouse button is pressed, a small cursor will appear at the center of the player's screen. Releasing the mouse button with the cursor over a terrestrial or aquatic predator or a prey with the Acrocanthosaurus will mark the player for 10 seconds, sound the alarm call, and inform your herd in chat. Only the marked player, yourself, and any other player in your herd will be able to see the mark, but all players can hear the call.