The Yautja species at the heart of the Predator movies, a choice that paid off by revitalizing the franchise in the 21st century. The iconic green blood plays a pivotal role in the events of Prey, but some audiences might be curious as to why the species has distinctive bioluminescent green blood.

Beyond being an easy way for the Predators to be further distinguished as an alien race, the distinct blood and its consistent presence in the franchise (especially as a plot beat in Prey) can be seen as a direct reference to a clever storytelling trick from the first Predator film. Released in 1987, that movie introduced the now iconic line "If it bleeds, we can kill it." This line is repeated in Predator and Prey, representing the realization that because the Yautja hunters can be tracked and hurt, they can also be killed.

Predator's Green Blood, Explained

The Green Blood Gives Predator A Unique Visual Marker

The Predators have a distinctive green hue to their blood, helping underscore their alien nature. This aspect of the Yautja biology has been a factor in the Predator series since the very beginning of the series, when Dutch and his remaining allies were able to injure the Predator that was stalking them. Discovering the green blood was a good way to establish to the characters in-universe that the threat they're contending with is an alien creature and not just some advanced human weapon.

The green blood is a unique visual marker, playing into both the sci-fi elements and the violent aspects of the series. The green blood serves as an easy way to help distinguish the Predator from any human, while also serving as a bright flash of color not typically seen on film. The particularly luminous shade of green in the blood draws the eye of the audience, gives the in-universe characters something clear to track, and ensures any brutal fight scene involving a Predator stands out from the typical combat seen in an action/sci-fi film.

The Unique Properties In Predator Blood

Depending On The Target, The Predator Blood Can Either Be A Help Or A Hinderence

These visual properties of the Predator blood are important, although definitive explanations for them remain elusive. Nevertheless, a simple and sensible answer is to assume that the properties of the Yautja’s blood cause its green color. It can be assumed that their blood doesn’t contain hemoglobin, which causes red pigmentation in human blood. There are examples of animals on Earth that have green blood caused by the presence of chlorocruorin. However, given that Yautjas originate far away from Earth, it seems unlikely that the same specific oxygen-binding proteins would be present in their blood.

The distinctive properties in Predator blood are both an aid and a hindrance to the alien hunters. Notably, the bioluminescence of their blood has assisted the humans they hunt. ittedly, the difficulty for characters like Dutch in Predator and Naru in Prey making them bleed in the first place. Since the Yautjas’ cloaking technology gives them a huge advantage over their human adversaries, the advantage is lost once their blood is spilled and can be tracked. In that regard, a Predator's own blood can work against them, turning the hunters into the hunted.

Predator blood is far more useful in their confrontations with Xenomorphs. Despite the events of 2018's The Predator, it remains unclear whether Alien vs Predator and Alien vs Predator: Requiem can be considered completely canon in the Predator movie series. Even so, these movies do illustrate a key property of Predator blood. Xenomorph blood is a potent molecular acid with the ability to burn through human flesh and bone. However, this is not the case with Yautjas. Their blood can partially neutralize this acid, offering their flesh a degree of protection from the Xenomorph’s powerful defense mechanism.

Interestingly, not all Predator blood is the same. The so-called "Feral Predator" of Prey has darker and less luminous blood than other Yautjas. It has been suggested, though not confirmed, that this may be an evolutionary quirk due to the "Feral Predator," which also had a distinctive mask, evolving in a more desert-based environment than other Predators. Whatever the cause, the unique properties of Predators’ glowing green blood remain a distinctive and arresting image and a powerful element within the wider Predator mythos.