• 
  Liz Bonnin

  (unknown episodes)
• 
  Taryn Gilroy

  Self - conservation biologist
• 
  Axel Hunnicutt

  Self - University of Pretoria
• 
  Axel Primmer

  Self
• 
  Patti Ragan

  Self
• 
  Didone Frigerio

  Self - biologist
• 
  Louis J. Guillette

  Self - professor
• 
  Kurt M. Kotrschal

  Self - professor and biologist, Universität Wien

• 
  Paul Rose

  Self - University of Exeter
• 
  Thomas Flower

  Self - University of Cambridge
• 
  Joachim Schöne

  Self - veterinarian
• 
  Qazi Rahman

  Self - psychologist, King's College
• 
  David Boza

  Self
• 
  Françoise Malby

  Self
• 
  Alison Cronin

  Self - anthropologist, director of Monkey World

• 
  Cat Talbot

  Self - keeper of Sam the Gibbon
• 
  Camila Galheigo Coelho

  Self - biologist
• 
  Isabel Behncke

  Self - primatologist