Runner

Runners (Internecivus raptus canis) are one of the smallest aliens, on par with the Drone. They act as scouts for the Hive, likely due to their quadrupedal and fast nature. Other names for them are the Dog Alien or the Bambi burster. They are made from a facehugger jumping onto a dog or other quadrupedal species, such as an ox.

Appearance
Runners are tinged a noticeable brown and run on four legs like the host they hailed from. However, they will walk and stand on two legs sometimes. On their back, there are no dorsal tubes, likely for better head mobility. Unlike most Aliens, they are digitigrade (i.e. they walk on their toes).

Their chestbursters are not as larval as the other aliens, but rather a smaller, pale version of itself.

Mannerisms and Abilities
"It's like a lion....sticks close to the zebras"

- Ellen Ripley speaking to Francis Aaron about the Runner's nature.

The Runner is all about speed and agility, perhaps one of the fastest castes of Xenomorph ever encountered. It stalks its prey much like a lion or tiger, waiting for an unfortunate victim to come about and killing them outright rather than cocooning them in a nest like others would. They are known to use stealth just like their siblings but cannot walk on two legs without some kind of supporting structure keeping them up on two. Although not as strong as other castes, Runners are still strong enough to lift a full grown human. They also are known to attack the head of their prey with their pharyngeal jawed tongues like their siblings. They also are known to go after anything or anyone that tries to interact with it, either verbally or physically trying to harm it, but even when those factors don't apply Runners attack victims of their choosing.

It has been widely believed that Xenomorphs can eat humans, however not many people have seen this happen. It was the Runner known as "The Dragon" in Alien 3 that started taking bites out of a prisoner it captured in the lead works of the penal colony of Fury 161.

The Runner was the first caste of Xenomorph to introduce the creature's ability to spit acid at its victims and the only alien able to poison prey and continue damaging long after it has been killed itself. The game AVP:E (Alien versus Predator: Extinction) shows them being able to do this, after upgrading. They also do this in the game Aliens vs Predator (2010) and look exactly like the one from Alien 3.

Runners are shown to be more animalistic in nature and are not the sharpest caste in the hive. They do have some intelligence, but not as much as their drone or warrior counterparts. This is shown in Alien 3 when the Runner on Fury 161 utilizes hit and kill tactics rather than capturing creatures and cocooning them in an established nest like drones or warriors. They are known to be smart enough to not harm any members of their own kind, especially larval queens. This was seen when Ellen Ripley was in the medical bay of the Fury 161 penal colony. After the Dragon killed Chief Medical Officer Jonathon Clemens, it quickly turned to Ripley who was horrified of the creature and despite its intimidating moves towards her, left her completely unscathed. It even tried protecting Ripley from Leonard Dillon who was trying to get her away from it while it was trapped in a corner. The Xenomorph Runner also demonstrates its desire for revenge, even against those carrying unborn Xenomorphs. This was seen after the Dragon was drowned in hot lead and managed to survive. This led to the creature chasing after Ripley until she dowsed it in water from the sprinklers causing it to explode via thermal shock.

Despite being a Xenomorph caste, Runners aren't as durable as others and weakest of them all.