 The toughest part is, of course, feeding the fleas, which does require some human involvement of a kind of sacrifice I personally am unwilling to make, but Miss Cardozo apparently is not. Once you train fleas, then are they like your stable of actors, or do you recruit new fleas when you arrive in Edinburgh? Well, unfortunately, their lifespans are not particularly long, so you're always recruiting and training new fleas. Maria Fernanda Cardozo. Yes.