With the caveat that Global Zootierliste still has notable gaps and identification issues, at 10 months in I think there is enough reliable data to make *some* comparisons – and so I thought I’d start with a group that is reasonably well-documented (the great apes) and see how a comparison between Europe and North America would play out!
I chose this group mainly because I happened to already have a (largely) complete holder list of great apes in the US, so all I had to do was double-check these and then compile the European stats. I took three steps:
1) Compared the overall holdings of each great ape genus (Gorilla, Pongo, and Pan) between Europe* and North America*;
2) compared the combinations of great ape genera between European and American zoos (in other words, how many zoos on each continent hold each possible combination of great apes);
3) compared the great ape holdings of North America by geographic region to each other (I did not do this for Europe because classifying European countries into groups always seems to start fights here
)
So let’s get into it!
Topline Numbers
*Important notes:
1) my definition of “zoo” excludes captive facilities not open to the public – therefore excluding a number of great ape sanctuaries on both continents.
2) these numbers may be slightly off - especially for chimpanzees, due to the sheer number of holdings in Europe and multiple listings by subspecies there. I am confident they are not off by enough to significantly alter the general patterns I found.
In total (according to ZTL) there are 142 European zoos* and 88 North American zoos* with great apes – so already 60% more in Europe than in North America. As you will see below, however, this gap is explained almost entirely by one genus:
So almost no difference in holdings for Gorilla and Pongo (4% and 2% respectively) but a 136% (i.e. over 2x) difference between Pan holdings on the two continents. Although Bonobos (P. pygmaeus) are more common in European zoos than North American zoos (11 vs 7), the overall number was small on both continents – so the Chimpanzee (P. troglodytes) makes up the vast majority of the difference. One additional note: a small number of zoos in Europe hold both Chimpanzee and Bonobo, while none in the United States currently do.
It is also worth pointing out that – while Chimpanzees are significantly more widespread than any other great ape in European zoos – in North American zoos they are not only less widespread, they are less common than both gorillas and orangutans.
Great Ape Zoo Combinations
I also wanted to see what “combinations” of great ape zoos had on each continent – i.e. what zoos had only one genus versus two versus all three, and what genera did they combine or hold exclusively. Overall the numbers here aren’t surprising once you’ve seen the topline holdings, but some differences are worth noting:
The dominance of Chimpanzees in European zoos is clear here: there are roughly 4x as many zoos holding only Chimpanzees on that continent as in North America, accounting for the vast majority of the differences in great ape holding between the two regions (no zoos on either continent hold only Bonobo). Gorilla + Pan and Pongo + Pan combos are also more common in Europe, most likely a product of Pan being more common there generally. Meanwhile, Gorilla + Pongo combos are more common in North America – which is likely also a product of fewer zoos having Pan, since North America and Europe have similar numbers of the other two apes. The number of zoos holding only Gorilla or only Pongo was similar between the two continents, with the Gorilla-only option being slightly more popular in Europe and the Pongo-only option being slightly more popular in North America.
One somewhat surprising result is that – despite having significantly fewer zoos holding Pan – North America actually has slightly *more* zoos than Europe with all three genera (18 vs 16). The difference is small enough to possibly just be a coincidence… or, perhaps it is a product of North America having fewer zoos with great apes than Europe. Just over 60% of zoos with great apes in Europe have only one genus (with over 70% of those being Pan-only) while only 45% of zoos with great apes in North America have only one genus. A North American zoo with great apes has roughly double the odds of having a genus trifecta than a European zoo with great apes (20% vs 11%).
North American Geographic Comparisons
Finally, I did a breakdown of how many zoos in each of the four geographic regions of the United States (Northeast, South, Midwest and West) and Canada held each genus of great ape. The sample size isn’t that large, so any differences you see could likely be explained by random chance; however, it is worth noting that no genus was absent from an entire region (except for Pan in Canada) and the difference between regional holdings of two genera was never greater than 7 (numerically) or 50% (proportionally).
Some notes about geographic definitions:
Some interesting differences do stand out. The Southern United States has the most zoos with great apes (32) and the most zoos with a genus trifecta (8); the Midwest then the West follow in a linear fashion on both counts (25 and 18 zoos with great apes, 6 and 4 with genus trifectas). The Northeast has 9 zoos with great apes (half the number as the next US region) and none have a trifecta; Canada only has three zoos with great apes and none of these have a trifecta either (and in fact one genus is absent from public facilities in Canada, making a trifecta impossible).
Before I get into species comparisons, it’s worth pointing out that these regions have very different populations and this explains much of the variance in great ape holdings. Below is a combination chart showing the population of each region in bars and the number of zoos with great apes; the left axis measures population (in millions) while the right axis measures number of zoos.
Overall you see fewer zoos with great apes than you’d expect based on population in Canada, the Northeast and the West, while the Midwest has more zoos with great apes than you’d expect from the trendline. The South seems to be the most proportional region. The higher proportion of great apes in the Midwest and South – and comparatively low proportion of great apes in Canada, the Northeast and the West – is likely based on population density and distribution: the Midwest and South have lots of mid-sized and smaller cities with sizable rural populations surrounding them that can support zoos with great apes (ex. Fort Wayne, Indiana; Madison, Wisconsin; Greenville, South Carolina; and Chattanooga, Tennessee) while most people in the Northeast, Canada, and especially the West (where population density is very low in rural areas) are concentrated in a handful of larger urban areas that normally have just one major zoo with great apes.
As far as what genera are represented in each region, Gorilla is the most popular in the Northeast and Canada (in 9 of 12 zoos combined, with all three Canadian zoos holding them); Pan is marginally the most popular in the South (in 22 of 32 zoos); and Pongo is the most popular in the Midwest (18 of 25) and in the West (14 of 18). Pan are outnumbered by the other two genera outside the South, other than in the Midwest where they are equal with Gorilla. Some other interesting findings:
And that more or less concludes my research findings. Everyone please feel free to ask questions, make observations, or suggest other data analysis that could be done similar to this
I chose this group mainly because I happened to already have a (largely) complete holder list of great apes in the US, so all I had to do was double-check these and then compile the European stats. I took three steps:
1) Compared the overall holdings of each great ape genus (Gorilla, Pongo, and Pan) between Europe* and North America*;
2) compared the combinations of great ape genera between European and American zoos (in other words, how many zoos on each continent hold each possible combination of great apes);
3) compared the great ape holdings of North America by geographic region to each other (I did not do this for Europe because classifying European countries into groups always seems to start fights here
)So let’s get into it!
*Europe = the European Union + Norway, the UK and Switzerland (so excluding Ukraine, Russia, Turkey and the non-EU Balkan states)
North America = the United States and Canada (so excluding Mexico)
I understand that the “real” Europe and North America are bigger than this, but for a number of reasons (animal exchange patterns, unclear statistic reliability, international travel and transportation networks, etc) I ended up doing my analysis with only the above countries. Spare me the geopolitical commentary, please.
North America = the United States and Canada (so excluding Mexico)
I understand that the “real” Europe and North America are bigger than this, but for a number of reasons (animal exchange patterns, unclear statistic reliability, international travel and transportation networks, etc) I ended up doing my analysis with only the above countries. Spare me the geopolitical commentary, please.
Topline Numbers
*Important notes:
1) my definition of “zoo” excludes captive facilities not open to the public – therefore excluding a number of great ape sanctuaries on both continents.
2) these numbers may be slightly off - especially for chimpanzees, due to the sheer number of holdings in Europe and multiple listings by subspecies there. I am confident they are not off by enough to significantly alter the general patterns I found.
In total (according to ZTL) there are 142 European zoos* and 88 North American zoos* with great apes – so already 60% more in Europe than in North America. As you will see below, however, this gap is explained almost entirely by one genus:
So almost no difference in holdings for Gorilla and Pongo (4% and 2% respectively) but a 136% (i.e. over 2x) difference between Pan holdings on the two continents. Although Bonobos (P. pygmaeus) are more common in European zoos than North American zoos (11 vs 7), the overall number was small on both continents – so the Chimpanzee (P. troglodytes) makes up the vast majority of the difference. One additional note: a small number of zoos in Europe hold both Chimpanzee and Bonobo, while none in the United States currently do.
It is also worth pointing out that – while Chimpanzees are significantly more widespread than any other great ape in European zoos – in North American zoos they are not only less widespread, they are less common than both gorillas and orangutans.
Great Ape Zoo Combinations
I also wanted to see what “combinations” of great ape zoos had on each continent – i.e. what zoos had only one genus versus two versus all three, and what genera did they combine or hold exclusively. Overall the numbers here aren’t surprising once you’ve seen the topline holdings, but some differences are worth noting:
The dominance of Chimpanzees in European zoos is clear here: there are roughly 4x as many zoos holding only Chimpanzees on that continent as in North America, accounting for the vast majority of the differences in great ape holding between the two regions (no zoos on either continent hold only Bonobo). Gorilla + Pan and Pongo + Pan combos are also more common in Europe, most likely a product of Pan being more common there generally. Meanwhile, Gorilla + Pongo combos are more common in North America – which is likely also a product of fewer zoos having Pan, since North America and Europe have similar numbers of the other two apes. The number of zoos holding only Gorilla or only Pongo was similar between the two continents, with the Gorilla-only option being slightly more popular in Europe and the Pongo-only option being slightly more popular in North America.
One somewhat surprising result is that – despite having significantly fewer zoos holding Pan – North America actually has slightly *more* zoos than Europe with all three genera (18 vs 16). The difference is small enough to possibly just be a coincidence… or, perhaps it is a product of North America having fewer zoos with great apes than Europe. Just over 60% of zoos with great apes in Europe have only one genus (with over 70% of those being Pan-only) while only 45% of zoos with great apes in North America have only one genus. A North American zoo with great apes has roughly double the odds of having a genus trifecta than a European zoo with great apes (20% vs 11%).
North American Geographic Comparisons
Finally, I did a breakdown of how many zoos in each of the four geographic regions of the United States (Northeast, South, Midwest and West) and Canada held each genus of great ape. The sample size isn’t that large, so any differences you see could likely be explained by random chance; however, it is worth noting that no genus was absent from an entire region (except for Pan in Canada) and the difference between regional holdings of two genera was never greater than 7 (numerically) or 50% (proportionally).
Some notes about geographic definitions:
NORTHEAST: Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, New York, New Jersey, Pennsylvania, Delaware, Maryland and the District of Columbia
MIDWEST: Ohio, Indiana, Kentucky, Michigan, Illinois, Wisconsin, Minnesota, Iowa, Missouri, North Dakota, South Dakota, Nebraska and Kansas. Kentucky is included in the Midwest total because the only zoo with great apes there is in Louisville, which is geographically more Midwestern than Southern.
SOUTH: Virginia, West Virginia, North Carolina, South Carolina, Georgia, Florida, Tennessee, Alabama, Mississippi, Arkansas, Louisiana, Oklahoma, and Texas (excluding El Paso). West Virginia was included for the South for cultural and statistical reasons, even though its one zoo with great ape is arguably closer geographically to the Northeast and Midwest.
WEST: Alaska, Hawaii, Washington, Oregon, California, Idaho, Montana, Wyoming, Utah, Nevada, Colorado, Arizona, New Mexico, and part of Texas. El Paso, Texas was included in the Western total as the city is both geographically and culturally more Western than Southern.
CANADA: All Canadian provinces.
MIDWEST: Ohio, Indiana, Kentucky, Michigan, Illinois, Wisconsin, Minnesota, Iowa, Missouri, North Dakota, South Dakota, Nebraska and Kansas. Kentucky is included in the Midwest total because the only zoo with great apes there is in Louisville, which is geographically more Midwestern than Southern.
SOUTH: Virginia, West Virginia, North Carolina, South Carolina, Georgia, Florida, Tennessee, Alabama, Mississippi, Arkansas, Louisiana, Oklahoma, and Texas (excluding El Paso). West Virginia was included for the South for cultural and statistical reasons, even though its one zoo with great ape is arguably closer geographically to the Northeast and Midwest.
WEST: Alaska, Hawaii, Washington, Oregon, California, Idaho, Montana, Wyoming, Utah, Nevada, Colorado, Arizona, New Mexico, and part of Texas. El Paso, Texas was included in the Western total as the city is both geographically and culturally more Western than Southern.
CANADA: All Canadian provinces.
Some interesting differences do stand out. The Southern United States has the most zoos with great apes (32) and the most zoos with a genus trifecta (8); the Midwest then the West follow in a linear fashion on both counts (25 and 18 zoos with great apes, 6 and 4 with genus trifectas). The Northeast has 9 zoos with great apes (half the number as the next US region) and none have a trifecta; Canada only has three zoos with great apes and none of these have a trifecta either (and in fact one genus is absent from public facilities in Canada, making a trifecta impossible).
Before I get into species comparisons, it’s worth pointing out that these regions have very different populations and this explains much of the variance in great ape holdings. Below is a combination chart showing the population of each region in bars and the number of zoos with great apes; the left axis measures population (in millions) while the right axis measures number of zoos.
Overall you see fewer zoos with great apes than you’d expect based on population in Canada, the Northeast and the West, while the Midwest has more zoos with great apes than you’d expect from the trendline. The South seems to be the most proportional region. The higher proportion of great apes in the Midwest and South – and comparatively low proportion of great apes in Canada, the Northeast and the West – is likely based on population density and distribution: the Midwest and South have lots of mid-sized and smaller cities with sizable rural populations surrounding them that can support zoos with great apes (ex. Fort Wayne, Indiana; Madison, Wisconsin; Greenville, South Carolina; and Chattanooga, Tennessee) while most people in the Northeast, Canada, and especially the West (where population density is very low in rural areas) are concentrated in a handful of larger urban areas that normally have just one major zoo with great apes.
As far as what genera are represented in each region, Gorilla is the most popular in the Northeast and Canada (in 9 of 12 zoos combined, with all three Canadian zoos holding them); Pan is marginally the most popular in the South (in 22 of 32 zoos); and Pongo is the most popular in the Midwest (18 of 25) and in the West (14 of 18). Pan are outnumbered by the other two genera outside the South, other than in the Midwest where they are equal with Gorilla. Some other interesting findings:
- All 6 zoos with Gorilla + Pan combos are in the Midwest and South;
- The Midwest has no zoos with only Gorilla, despite having the second highest number of zoos with Gorilla;
- Other than a lone chimp held at a roadsize zoo in Oregon (the status of which recently earned them a USDA citation), every Western zoo with great apes outside California has Orangutans;
- 14 US states lack a zoo with great apes; all but one of these states is in the bottom half nationally for population size, the exception being New Jersey (which has two zoos with great apes about 5 mi from the border);
- 7 US states only have one genus of great ape in their zoos: three with only Orangutan (one zoo each in North Dakota, Arizona and as of recently Hawaii), three with only Chimpanzee (one zoo each in Mississippi, West Virginia and Maryland) and one with only Gorilla (New York, with two zoos)
And that more or less concludes my research findings. Everyone please feel free to ask questions, make observations, or suggest other data analysis that could be done similar to this
I enjoy reading posts packed with information and there's lots to analyze in this thread. A key takeaway that has already been briefly discussed is the abundance of Chimpanzees in European zoos in comparison to American zoos. It's certainly a stark difference. However, you did mention that you excluded facilities that are not open to the public, which makes sense, but it does mean that there's a lot of chimps in the USA that are not accounted for if one were to look at total populations. Chimp Haven (300 chimps), Save the Chimps (330+ chimps over the years) and probably a dozen more primate sanctuaries in the U.S. all have Chimpanzees, and I'm not sure if Europe has as many high-profile Chimpanzee rescue centers. 
