* They are challenging to care for: Platypuses are very sensitive to their environment and have specific needs for water temperature, diet, and habitat.
* Limited breeding: Zoos are working on captive breeding programs, but platypus breeding is not easy.
* Conservation efforts: They are a threatened species, so zoos prioritize their welfare and may not exhibit them if they are not available.
To find out if a specific zoo has a platypus, you can check their website or call them directly. You could also try searching for "platypus zoos" on the internet.