They were not set free, they are still fenced.
Zebras in captivity.
- Thread starter CheeseChameleon1945
- Start date
Some are and some aren't. I just looked it up, some zebras are in Hearst Ranch, and others around San Simeon.
That was a poor choice of words on my part. I should have said they were allowed to freely roam, unmanaged, on the 80,000+ acres of the Hearst Ranch.
Maybe they could, but the question is also wether there would be any interest to set up a breeding program for them. In Europe for example there are already 3 breeding programs in place (Grevy - EEP, Hartmann - EEP and Maneless - Mon-P) and 3 more subspecies of plains zebra are semi- to very well established.
In Europe at least there isn't much space left if you'd turn every current population in a sustainable one. Hartmanns mountain, maneless and even Burchells need to grow to make the population sustainable in the long term. The grevy is currently at carrying capacity I believe. This means that only the non-subspefic, the grant's and the chapman are able to free up spaces, but the non-subspecifics should only have low numbers left in Europe and the chapman population is also not that excessive.
When looking at the current populations:
E. grevy: 59 zoos, taken as standard for carrying capacity
E. zebra hartmannae: 30 zoos --> + 30 needed
E. quagga boehmi: 162 zoos --> -100 in theory
E. q. borensis: 13 zoos --> + 47 needed
E. q. burchelli: 35 zoos --> +25 needed
E. q. chapmani: 97 zoos --> -37 in theory
E. q. ssp.: 24 zoos --> ideally all 24 freed up
This is of-course a rough schematic, some zoos keep more or larger herds and others keep small herds made up of more then one subspecies. What we can roughly learn from this is that only in ideal circumstances, about 60 spaces would be available for another species. Zoo population management however is messy and getting each (sub-)species to this level is almost impossible. I even doubt that they will be able to elevate each (sub-)species to this sustainable level and I wouldn't be surprised if EAZA would decide to phase out burchelli in favor of the other populations.
When looking at the current populations:
E. grevy: 59 zoos, taken as standard for carrying capacity
E. zebra hartmannae: 30 zoos --> + 30 needed
E. quagga boehmi: 162 zoos --> -100 in theory
E. q. borensis: 13 zoos --> + 47 needed
E. q. burchelli: 35 zoos --> +25 needed
E. q. chapmani: 97 zoos --> -37 in theory
E. q. ssp.: 24 zoos --> ideally all 24 freed up
This is of-course a rough schematic, some zoos keep more or larger herds and others keep small herds made up of more then one subspecies. What we can roughly learn from this is that only in ideal circumstances, about 60 spaces would be available for another species. Zoo population management however is messy and getting each (sub-)species to this level is almost impossible. I even doubt that they will be able to elevate each (sub-)species to this sustainable level and I wouldn't be surprised if EAZA would decide to phase out burchelli in favor of the other populations.
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I decide it might be interesting to dive a bit further into these modesl. This model above of-course doesn't take into account that for some species the average herd size is smaller then others or that for some species the relative number of males that get to breed is higher then for others. Both factors affect the effective population size used in the classical 50/500 rule.
Based on ZTL i suspect average herd-size to be about 3,5 (or 3.5) - 5 for most populations. This means for 60 zoos about 210 - 300 zebra's. Taking into account that not every female breeds and that breeding males almost always have several foals resulting in several males that can not breed, I estimate the effective population size to be about 30 - 65% of the total population. I know it's low, but there are some females having almost a dozen offspring and males having 5-6 foals isn't that uncommon. I'd even say the only way they could currently get near 65 is through culling, but I don't know how commonly it's done with zebras. Introducing new genetics via sperm or animals from other continents is of-course also an option, but I don't think this is done very often currently.
So what does this mean. If we are very pessimistic and take 30% and let's say 200 zebra's, that means you have roughly 70 zebra's with offspring. That's quite low to conserve genetics in the long run. So even though it's an unpopular move I'd even be inclined to say the best option is to phase out another subspecies of grant zebra (I'd say burchell due to it's low population size and it's lower conservation value compared to the maneless zebra).
I could of-course be wrong as the margin of error on such rough estimates is considerable. If anyone could confirm or correct some of these numbers that would be great.
Based on ZTL i suspect average herd-size to be about 3,5 (or 3.5) - 5 for most populations. This means for 60 zoos about 210 - 300 zebra's. Taking into account that not every female breeds and that breeding males almost always have several foals resulting in several males that can not breed, I estimate the effective population size to be about 30 - 65% of the total population. I know it's low, but there are some females having almost a dozen offspring and males having 5-6 foals isn't that uncommon. I'd even say the only way they could currently get near 65 is through culling, but I don't know how commonly it's done with zebras. Introducing new genetics via sperm or animals from other continents is of-course also an option, but I don't think this is done very often currently.
So what does this mean. If we are very pessimistic and take 30% and let's say 200 zebra's, that means you have roughly 70 zebra's with offspring. That's quite low to conserve genetics in the long run. So even though it's an unpopular move I'd even be inclined to say the best option is to phase out another subspecies of grant zebra (I'd say burchell due to it's low population size and it's lower conservation value compared to the maneless zebra).
I could of-course be wrong as the margin of error on such rough estimates is considerable. If anyone could confirm or correct some of these numbers that would be great.
imaginarius
Well-Known Member
Are Grévy’s the most common in captivity? And is that due to the fact that zoos want to have a robust insurance population, given their endangered status?
No. Plains Zebras are the most common, but Grevy's would probably be number 2.
imaginarius
Well-Known Member
Does anyone keep Selous’s zebra? The internet informs me that it is by far the most endangered of all zebra species and subspecies.
It is, but due to its rarity I wouldn't be surprised if it was kept in some reserves and research centers in its native range, or at least near it. Not sure about public facilities though.
I think that Grant's is #1, then Grevy's, then Burchell's, then Hartmann's Mountain for the US.
No chapmani in the US? It's the second biggest population in Europe so that kinda surprises me.
I agree. There has to be somewhere that keeps Chapman's Zebra in the U.S.
I remember reading about this years ago. Wasn't it to establish a population of Grevy's zebras?
Ah, yeah there definitely are Chapman's in the US. They would probably be 5th, though.
Interesting, that would give the option for Europe to let the Burchell go and keep the chapman, and for the US to do the reverse. That way they would at least free up spaces in Europe for the Maneless and hartmann mountain zebra. Depending on current population sizes, the Us could then expand their Hartmann program and possibly even bring in another subspecies of either mountain (cape) or plains zebra (selous or crawshawi). The latter would of-course be a difficult matter as those subspecies aren't easy to get. It might just be better for them to stick to 4 populations (grant, burchell, grevy and hartmanni), and probably this is also what will happen in reality as the small chapmani population will become more and more inbred and thus less viable.
Do you have any evidence to substantiate your claims about Chapman’s zebras in the United States, or are you just assuming? There is likely Chapman’s blood in the plains zebra population in the States, but it is extremely unlikely there are any purebred animals left. The plains zebra population is largely hybridized— even many “Grant’s” zebras are to some degree hybrids, though there are far more purebred Grant’s left than there are Burchell’s. The plains zebra population is to be phased out of AZA institutions, single species zebra exhibits are to be replaced with Grevy’s and multi-species exhibits are to be replaced with Hartmann’s. In theory there should be space for another purebred population, but I can pretty much guarantee that will not happen. With the changes coming down the pipeline for SSP and related programs within the AZA, we can really only expect decreases in programs and decreases in species.