Wednesday, 3 February 2010
Giving tiny toads a home
Zoos are a controversial subject. Even if we leave aside the question over the cruelty or not of keeping animals in captivity, there is a whole other debate as to their role in conservation. Pioneers such as Gerald Durrell say zoos as a vital component of conservation effort, acting as a stationary ark to preserve the most endangered species until their wild habitats can be repopulated. For Durrell, conservation was the primary objective of zoos and any other benefit was subsidiary. How then, does this ideal stand up in the cold light of day?
Examples such as the Arabian oryx (extinct in the wild in 1972, now has a wild population of over 1000) and black-footed ferret (last wild population removed to captivity in 1985, wild population thought to be in excess of 750) show that ex situ conservation can not only work but give a huge publicity boost to conservation. In a world of increasingly doom-laden prophecies, it’s nice to hear that the ferrets are OK.
However, several studies have argued that whilst there are success stories, there perhaps aren’t as many as we would like. Clubb et al. (2008) showed that elephants in captivity actually have a lower life expectancy than in the wild, whilst Balmford et al. (1995) demonstrated that keeping black rhinos in captivity costs over twice as much per year as managing a national park with rhinos in. Moreover, Conway (1986) made the point that even with the best will in the world, zoos will be unlikely to house viable populations of more than around 500 species of vertebrate. The IUCN red list currently contains over 1000 mammal species alone – clearly ex situ conservation will not be a panacea to biodiversity conservation.
There are many other issues with ex situ conservation as well, involving the risk of novel diseases, loss of adaptation to the wild, limited reintroduction success and so on, but I want to concentrate on this idea of capacity and choosing which animals you put in zoos. And I want to talk about tiny toads without a home.
In 1998, an adorable new species of toad was found in Tanzania. This week, the NY Times reported that there were no longer any in the wild (http://www.nytimes.com/2010/02/02/science/earth/02toads.html?ref=global-home). In a similar story, the truly hilarious Panamanian golden frog was recently evacuated from its last known wild home (http://news.bbc.co.uk/1/hi/7219803.stm) and, whilst less yellow, the equally charismatic and brilliantly named mountain chicken frog was airlifted to safety (http://news.bbc.co.uk/cbbcnews/hi/newsid_8010000/newsid_8011600/8011646.stm - all the best news is from cbbc).
So why am I talking quite so much about amphibians? My point is that these species are as endangered as lions or elephants but you can actually keep them in captivity. If you load up a zoo with frogs, toads and even invertebrates then you can vastly increase the number of species you can save. The six species of Patulla snail at Bristol zoo are allegedly managed by a single part-time keeper; whilst the cost of keeping the (admittedly horrific-sounding) wartbiter cricket in captivity is something around 1% the cost of a gorilla. If zoos want to actually conserve species, rather than act solely as a glorified amusement park then they could get so much more done by concentrating on species they can actually keep alive. Unfortunately, this is almost exactly the opposite of what they are actually doing. The number of breeding programmes for mammals actually increases with body size (Balmford et al. 1996) when all sense and reason says the opposite should happen.
Obviously there are issues of drawing people to zoos using charismatic megafauna and so on but wouldn’t it be better to get people interested in the smaller, less spectacular species as well? Who are we to say that a rhino or a gorilla has any more right to a home than a tiny toad?