Open-air cages installed in the Monkey House resulted in a dramatic improvement in the life expectancy of its residents, but the potential for expansion and improvement after the First World War was limited by the post-war economy. Rising labour costs and minimal profits resulted in the gardens' increasing dilapidation. The zoo began to be neglected after the sale of Belle Vue in 1925, but it was rejuvenated by the appointment of Gerald Iles as zoo superintendent in 1933. A new Gibbon Cage and Monkey Mountain were created and the Reptile House was extended.