A few questions came up in the 'Wild Asses in the UK' thread regarding Marwell's mortality rates. Marwell are one of the (very) few UK zoos who are open enough to publish births and deaths for every species. The only other zoos that make this information public are Chester, Edinburgh and Bristol, unsurprisingly all members of the Consortium of Charitable Zoos (CCZ). Dudley also published the overall number of deaths in their bird and mammal collections. Quotes copied from the other topic: I thought the numbers were surprising too, but then I've never studied zoo births/deaths very closely! I compared the Marwell numbers with those for Chester, Edinburgh, Bristol and Dudley, looking only at mammals and birds, and excluding rodents which would seriously distort the results. What is interesting is that in 2006, Marwell had the lowest birth and death rate of the five zoos. I have also been in contact with Marwell. They do try to limit or control the breeding of the ungulates but had to dispose of a number of male ungulate calves last year. Other options (repatriation in the wild or formation of a bachelor group at another zoo) are not always available. They use a nearby SSI to graze a group of Przewalski's horse. They have had a problem with penguin chicks dying because the parents are trying to feed them twigs. Unfortunately the same thing has happened this year. They are looking at ways to resolve the problem before the next breeding season. Marwell have categorically stated that all deaths and disposals are incinerated under supervision or donated to a leading museum for research purposes. Autopsies can provide useful information to inform husbandry techniques.
Okay, some fair points there, I can understand breeding and then selectively managing endangered species like the oryx or Dama gazelles, but would you allow any breeding whatsoever of common species like Kudu or Collared Peccary if you know it will be impossible to place the males? Surely you just wouldn't allow your current animals to breed, rather that knowingly set yourself up for some sizeable numbers to inevitably have to destroy once born. Seems such a waste, and at great risk of bad publicity. If you can't place animals that are common already, don't produce them.
Ok, nobody else has replied for a while so I'm going to shamelessly keep this thread going because I think it's quite an interesting subject! It's perhaps worth pointing out that my comparison of Marwell's mortality rates with other zoos isn't entirely valid because of course no two zoos have the same animal collection. Marwell as we know have a higher proportion of large mammals than the 'average' zoo which may well explain their lower birth and death rates. The reason I excluded the like of rodents and reptiles from my comparision is because their breeding rates/clutch size would dramatically skew the data (for example, Chester had over 800 births and deaths of Turkish spiny mice last year!) As for the breeding of more common species it does lead to the questions you raised Hadley. I don't have the answers to those, but it could be that the matings were accidental, or that they were purposeful in the hope of female offspring to continue the line, and Marwell just got unlucky.
I agree, it's really strange how few people wanted to comment at all on this thread. It is definitely important to compare similar taxa when looking at death rates, I was specifically interested in the losses occurring in ungulates and longer-lived birds such as cranes and parrots. Marwell does some really good work, eg. with oryx, somali ass, okapi, etc, I just don't get why the rest of the park is full of hybrid giraffe, hybrid roan antelope, and common species such as peccary and kudu, which they then have to cull to keep under control. It also seems strange to me the imbalance from collection to collection, where some zoos might announce a birth as special of the same species that marwell has to control the population of!
I haven't got involved in this 'death' debate yet as I don't have a good knowledge of the numbers involved etc(for any zoos) but its still very interesting nevertheless... Marwell has,in the past,kept a very wide range of species, many of which for various reasons, they no longer have. Partly this was due to their gradual transition to (chiefly) African hoofedstock. I think some of the common species they still keep are necessary in order for them to have a sufficiently large collection, which has also become(apart from the African ungulates) far more generalised than it used to be.
