Survival of the Fittest (audio story)

 was the one hundred and thirty-first monthly Doctor Who audio release produced by Big Finish Productions. It is the final 3 part story in Big Finish's Doctor Who range, bringing the experiment of 3 and 1 part stories, beginning in April 2007 with I.D. (3 part) and Urgent Calls (1 part), to a close.

Publisher's summary
The hive of the Vrill bears the scars of a terrifying cataclysm. Only a handful remain alive, hatched after the holocaust of the mysterious Winterlack. The Vrill seek a new Authority. They find the Doctor, a two-legged creature who can lead them to survival. He must solve the mystery of the Carrion beast that haunts the lower chambers. He must face the Winterlack that still stalk the mountains. And he must find a path that does not lead to extinction...

Plot
to be added

Cast

 * The Doctor - Sylvester McCoy
 * Elizabeth Klein - Tracey Childs
 * Steffen / The Authority - Adrian Bower
 * Rose / The Vrill - Hannah Smith
 * Lilly / The Vrill - Evie Dawnay
 * Jackson / The Watcher - Mark Donovan
 * The Carrion - Alex Mallinson
 * Butterfly - Rupert Wickham

The Doctor

 * The Doctor tells Lilly that he has known many beekeepers in his time. He claims that Aristotle never stopped wittering on about bees whereas he was stuck at a tea party with Thomas Jefferson and he spoke about them at least.
 * Klein tells the Doctor that, with his intelligence, he would have been a great asset to the Nazi Party. The Doctor sarcastically remarks that it was "such a sweet thing to say."

Individuals

 * Steffen claims that he, Jackson and their deceased colleagues are the advance party of colonists. In actuality, they are raiders seeking the Vrill's super-concentrated nutrients, having almost devastated the colony through the use of the "Spear of Destiny" biological weapon akin to nerve gas.

Organisations

 * Steffen mistakes Klein for a representative of the Geopolice, an environmental agency which is charged with selecting and if necessary restricting access to planets across the various neighbouring systems (relative to the Vrill colony) identified for colonisation or exploitation. They are essentially fascists. Steffen regards them as being incorruptible. He disagrees with Geopolice's philosophy as he believes that humans are the master race which should be permitted to treat nature in whichever way it chooses.

Planets

 * The Doctor and Klein previously visited the crystal plains of Mandroxya, the Folly Ocean of Quindrax IV and the mercury swamps on Vulcan.

Species

 * The Vrill are a communal winged insect species where the individual members are organised into a variety of different roles: workers, watchers, warriors, healers and male drones. As is typical of insect species, sentient or otherwise, there is a fertile queen at the top of the hierarchy, whom the Vrill refer to as the Authority. The Vrill do not have individual names but the Doctor gives the two worker Vrill the names "Rose" and "Lilly" due to their smells and the newly hatched warrior Vrill the name "Butterfly" due to its magnificent wings.
 * At the centre of the colony, there is a hatching yard where the Authority has laid thousands of eggs in a geothermal pool of hormonal fluids which cure the eggs and the resulting pupae become warriors, workers or male drones. Without fertilisation, the eggs hatch in their default warrior state. It is possible to create a new Authority by releasing certain nutrients into an egg but only an existing Authority possesses this ability.
 * The scent which the Vrill use to represent their human attackers is translated by the TARDIS' telepathic circuits as "the Winterlack." They killed the vast majority of the Vrill, which they refer to as xenomorphs, using weapons grade nerve gases.

TARDIS

 * Through the TARDIS' telepathic circuits, Klein hears the Doctor speaking German in "a stuffy Prussian accent."
 * The TARDIS' telepathic circuits can translate scent used by the Vrill into speech that can be understood by the Doctor and the humans.

Continuity

 * The Doctor and Klein have recently visited the mercury swamps of Vulcan. (TV: The Power of the Daleks)
 * There no longer seems to be a spare TARDIS key in the cubbyhole above the "P" outside the TARDIS. (AUDIO: The Architects of History) It would be restored by the time of the Doctor's regeneration into his eighth incarnation. (TV: Doctor Who)
 * The removal of Klein from the timeline in AUDIO: The Architects of History probably resulted in the events of this story being either changed significantly or prevented entirely. The Doctor may have visited the Vrill homeworld alone or with another companion, but his/their adventure would certainly have ended quite differently.