Considering the amount of work that has gone on in the past couple of decades the news that numbat numbers have fallen is very depressing. During that time operation Western Shield has been fairly successful in eradicating foxes over a wide area, and in situ and ex situ work has led to successful introductions into a number of new sites. Perhaps the drop is numbers is related to reduced rainfall in recent years. The numbers of woylies in the same area has fallen after populations had had many years of growth and no-one is sure why this is.
The zoo population has not grown in this time as the animals bred at Perth Zoo are used for reintroductions. Perth is the only zoo to keep and breed them apart from the odd collection every so often such as Cleland. I don't know why other major Australian zoos don't display them - perhaps there is a zoochatter who knows the answer to this.
Alice Springs desert park is/was the only other collection to house them (probably not an ISIS member, largely because many of their species aren't uploaded into the species list!).
It is true that the numbers at Perth do fluctuate due to the release program. The slow increase in numbers is probably due to the relative high mortality of the species. Basically it is at the unfortunate size to be eaten by virtually every available medium and large-sized predator (wedge-tail eagle, goannas, pythons, quolls, foxes, cats). That and the fact they don't live for many seasons, I think 5 years is doing exceptionally well.
Pygathrix - you are probably correct that the sustained drought conditions are having an impact on the population. Much of the numbat's natural habitat is/was arid bush which has in the past been turned into what the locals refer to as 'the Wheatbelt'. Occasional long-term droughts and poor water useage has turned productive areas into salty deserts, which are difficult to reverse. I'm sure this has a cumulative effect even on those areas that haven't been farmed. The feral foxes and cats only added insult to the problem. While Western Shield has been very successful, again it is labour intensive managing the baiting program.
Perth has the breeding and rearing husbandry down pat, but it is exceptionally labour-intensive. Staff need to harvest local species of termites, raiding the exposed top of a mound (think half a football - soccerball, not aussie rules). The termites can be kept for a period, but obviously without queens, they do not breed and need replacing. Numbats can be managed on a specially balanced custard mixture, but will not breed without a high percentage of termites in the diet. This kind of explains why the other zoos in Australia are unable to join in on the program.
Why don't other zoos display numbats? Although they are an endangered, diurnal and pretty species, most zoos (or visitors) aren't going to go ga-ga over a small orangey striped squirrel that eats ants. Well to the largely uninformed... It works okay at Perth because they are native to that part of the world.
