While there are numerous variations on the Hunter, all types are genetically engineered B.O.W's which share common characteristics such as powerful claws, a bipedal form and scaled skin accompanied by a generally reptilian form. The Hunter was created by the Umbrella corporation through a process which involved the combination of a fertilised human egg being injected with reptillian DNA using the T virus prior to the zygote stage. The Hunter is then raised in a tank which simulates the amnion until it is fully developed, resulting in a biological weapon which retains both human and reptilian characteristics. The original Hunter model was first developed by William Birkin after a breakthrough allowed him to stabilise the virus and produce the Hunter, though most of the further research was carried out by unspecified Umbrella scientists while Birkin continued research into the G virus.
As a weapon the Hunter was designed specifically as a countermeasure to military forces with sufficient anti virus equipment/defenses to withstand the zombie infection caused by the T virus and the resulting onslaught. The hunter retains a great deal of intelligence compared to other B.O.W's and as such is capable of carrying out simple commands on the battlefield, cornering targets and stalking fleeing prey (even being able to open doors) and this makes the Hunter ideal as a countermeasure against experienced military units. It has proven to be one of Umbrella's most successful and cost effective B.O.W. projects and as such there have been numerous revisions and iterations on the Hunter formula.
Hunter Alpha ( RE 0, RE1) MA-121
Given the code number MA-121, Hunter Alpha was the first to be developed and proved to be extremely successful, going on to become the basis for all subsequent Hunter variants. A strong muscular build gives this type immense physical prowess and with the ability to jump great heights, move quickly and track targets as well as withstand a great deal of damage from most conventional firearms, this Hunter was a deadly foe for all those it encountered. Battle data obtained through it's confrontations with S.T.A.R.S. members in the Arklay mountains research facility and the mansion incident became incremental in the development of future models.
Hunter Beta ( RE 3 ) MA-121
Developed after the Alpha, the Beta was designed to improve upon it's predecessor in terms of cost effectiveness and battle capability. While the Beta had less physical strength and endurance than it's predecessor, it was developed with an improved nervous system which allowed it to react much faster and even evade bullets as a result. It is easily distinguishable due to the grotesque sores and tumours on it's torso, as well as a lighter more gaunt frame than the Alpha model. These mutations are the result of the extensive genetic manipulation used to develop the creature, and the cost of the enhanced nervous sytem it maintains.
Hunter II ( RE CV)
Notable for being the only Hunter variant which was not developed by Umbrella, in fact this variant was developed by a rival organisation in response to the success of Umbrella's project. Created using data supplied by Albert Wesker, the aim of the project was to increase the control which could be exerted over the Hunter. A system named the automatic surveillance device is implemented in this Hunter design, allowing the Hunter to be controlled, and the user to specify targets for the Hunter to attack. The result is a much more effective weapon on the battlefield.
The Hunter II also has a subspecies named the Sweeper, which utilises poison based attacks and can be distinguished by it's purple and red colouring as well as it's poisonous claws. It should be noted that neither version is actually encountered by the player over the course of the series.
Hunter Gamma ( RE 3, CV, Outbreak) MA-124
The Hunter Gamma is a variant on the Hunter which incorporates amphibian DNA instead of the reptilian DNA found in other Hunter types. Developed in Umbrella's European research facility using data from the Alpha & Beta models as a base, the Hunter Gamma shows very dominant amphibian traits and increased intelligence.
The consequence of increased intelligence is the Gamma's physical weakness compared to the other Hunter variants, as well as it's lack of eyes and claws. Dominant amphibian traits prevent the Gamma from surviving outwith aquatic environments, and also cause further weaknesses such as an aversion to direct sunlight and dry air.
Considering these drawbacks the Gamma Hunter variant is the least effective Hunter type B.O.W. and as such has been found by Umbrella to be unsuitable for distribution.