Well, work and life got in the way – as I should have expected. Better late than never though.
Lizards
I’ve compiled the holdings for what I now believe to be the top two dozen or so most common lizard species in US zoological facilities… probably.
1. (tie) Gila Monster (Heloderma suspectum) – 96 holdings
1. (tie) Inland Bearded Dragon* (Pogona vitticeps) – 96 holdings
3. Prehensile-tailed Skink (Corucia zebrata) – 87 holdings
4. Green Iguana (Iguana iguana) – 85 holdings
5. Blue-tongued Skink (Tiliqua sp.**) – approx. 80 holdings
6. Leopard Gecko (Eublepharis macularius) – 64 holdings
7. Komodo Dragon (Varanus komodoensis) – 59 holdings
8. Common Chuckwalla (Sauromalus ater) – 52 holdings
9. Argentine Black-and-white Tegu (Salvator merianae) – 51 holdings
10. Sheltopusik (Pseudopus apodus) – 43 holdings
11. Rhinoceros Iguana (Cyclura cornuta) – 42 holdings
12. Caiman Lizard (Dracaena guianensis) – 39 holdings
13. Crested Gecko (Correlophus ciliatus) – 38 holdings
14. Henkel’s Leaf-tailed Gecko (Uroplatus henkeli) – 37 holdings
15. Madagascar Giant Day Gecko (Phelsuma grandis/madagascariensis***) – 36 holdings
16. (tie) Mexican Beaded Lizard (Heloderma horridum****) – 35 holdings
16. (tie) Veiled Chameleon (Chamaeleo calyptratus) – 35 holdings
18. (tie) Crocodile Lizard (Shinisaurus crocodilurus) – 32 holdings
18. (tie) Sudan Plated Lizard (Broadleysaurus major) – 32 holdings
20. Emerald Tree Monitor (Varanus prasinus) – 30 holdings
21. New Caledonian Giant Gecko (Rhacodactylus leachianus) – 28 holdings
22. Asian Water Monitor (Varanus salvator) – 27 holdings
23. (tie) Black Tree Monitor (Varanus beccarii) – 26 holdings
23. (tie) Green Basilisk (Basiliscus plumifrons) – 26 holdings
23. (tie) Cayman Blue Iguana (Cyclura lewisi) – 26 holdings
*technically combined Pogona holdings, but all holdings were assumed to be P. vitticeps based on available evidence
**is mostly T. scincoides, with smaller numbers of T. gigas and a single T. multifasciata holding
***includes P. grandis and P. madagascariensis. Both are present in US zoos and were once considered the same species, in the survey their results were combined.
****includes only true/suspected H. horridum, not any of the subspecies that have been elevated to species
Unsurprisingly, top of the list is a Halloween-colored venomous sleepy slug with a bulldog bite. You’d have to put a little cowboy hat on it to make it any more cartoonishly American.
Taken at Dallas Zoo by @GiornoPizza
US Survey Count vs US ZTL Holdings
Comparing my survey holdings to ZTL holdings, my capture rate once again had wide variability. My most accurate count was for Emerald Tree Monitor, with my survey capturing 90% of known holdings (27 of 30). My worst capture rate was for Argentine Black-and-white Tegu, with my survey capturing less than 20% of known holdings (10 of 51) – a very poor result, even by “common pet trade species” standards. Several other common pet lizards – Bearded Dragons, Leopard and Crested Geckos, Veiled Chameleons, Blue-tongued Skinks and Green Iguanas – all fell in the 25% to 33% capture range, so all ended up very underestimated also. Meanwhile, many species found mostly in accredited zoos and/or with captive breeding programs – Komodo Dragons, Black Tree Monitors, Henkel’s Leaf-tailed Geckos, Caiman Lizards and Crocodile Lizards – were all estimated pretty accurately, mostly in the 75% to 80% range. My average capture rate across ~24 common taxa was 57%, so worse than for amphibians.
In my lizard survey recap, I had found 4 species to be Abundant (40+ holders) and 9 species to be Very Common (30-39 holders). Based on current ZTL data, there are actually 11 Abundant and 9 Very Common species, so I definitely underestimated abundance for a lot of these species. Of the 25 taxa whose abundance I evaluated: 11 (44%) were estimated accurately, 8 (32%) were slightly underestimated and 6 (24%) were significantly underestimated. Oh well.
As far as what species are held in what kind of facilities… the first species I checked was the Black-and-white Tegu; unsurprisingly 75% of its holdings are in non-AZA facilities, it is a very common species for small, privately operated zoos and “interactive” aquariums like SeaQuests. The other common pet-trade species (Green Iguana, Leopard Gecko, Bearded Dragon, etc) were all similar, with 65 to 80% of holdings in unaccredited places like private zoos and safari parks, small aquariums, nature centers, science museums and reptile zoos.
Tegu: the cheap man’s monitor lizard. Lots of tiny private zoos in the countryside harboring this black-and-white egg-eating menace.
Taken at Tupelo Buffalo Park by @SusScrofa
Meanwhile, the % AZA holdings on many other species was the mirror opposite: roughly 75-85% of Blue Iguanas, Black and Green Tree Monitors, Caiman Lizards, New Caledonian Giant Geckos and Prehensile-tailed Skinks are in accredited zoos and aquariums, as are over 90% of Komodo Dragon holders and nearly 100% of Crocodile Lizards and Henkel’s Leaf-tailed Geckos. Therefore, as with amphibians there is a large divergence in what lizards are held in different types of zoos.
Once again I tested how much my survey captured holdings overall. I compared the overall holdings between the survey and ZTL for 7 lizard groups:
Anoles: 44/80 (55%)
Monitors (excl. Komodo, Asian Water, Green and Black Tree): 116/188 (62%)
Beaded Lizards: 116/153 (76%)
Phrynosomatidae: 57/72 (79%)
Skinks (excl. Blue-tongued and Prehensile-tailed): 67/86 (78%)
Geckos (excl. Leopard and Crested): 192/250 (77%)
Basilisks: 32/40 (80%)
With capture rates ranging from 55 to 80%, these results were similar to those for amphibians, with an overall average sitting around maybe 70-75%.
US ZTL Holdings vs Europe ZTL Holdings
This time I did not look at native versus exotic, since only 2 of the ~27 species I looked at were native (Gila Monster and Common Chuckwalla). For what it’s worth, both of those species were 40% more common in US zoos than European zoos… so okay, I guess I did look at them separately.
As for the exotics, there was a wide variation. The largest divergence percent-wise was Grand Cayman Blue Iguana, for which there is a robust breeding program here while European zoos only have a small handful of animals. The next largest divergences in America’s favor were Black Tree Monitors and Komodo Dragons, which are ~75% and ~65% more common than in Europe respectively. Komodos are a big one (literally and figuratively!) that I already knew was different; Europe has three dozen holders – with no more than half a dozen in one country – while the US has ~60 holders, now including the majority of large and mid-sized accredited zoos… and with at least a couple new holders still on the way in the next few years!
The new Komodo digs at Nashville Zoo, one of the newest in a line of major American zoos that jumped on the giant lizard bandwagon.
Taken by @cubsmaster
Meanwhile, Europe had larger holdings primarily for the common private trade species – which I’m guessing is either an artifact of more privately operated zoos generally, better reporting thus far on private zoos, or both. ZTL holdings count more than 3x as many Bearded Dragons in Europe, 4x as many Green Iguanas and Leopard Geckos, and 5x as many Veiled Chameleons. There are also (surprisingly to me) 5x as many Plumed Basilisks in Europe and 5x as many Madagascar Giant Day Geckos; I couldn’t really pinpoint a reason why, they just seem to be much more abundant in European zoos than in American zoos.
Did a bunch of European zoos get basilisks after Chamber of Secrets came out, or are plumes just that stylish across the pond?
Taken at Omaha's Henry Doorly Zoo by @DesertTortoise
Another surprising find is that the European Glass Lizard (Pseudopus apodus) was roughly equal between the two continents. In fairness the species is native to coastal southern Europe – i.e. not the countries most zoos are in – but it was unexpected nevertheless, given how many European-themed zoos and zoo exhibits are in the region.
Overall for 24 common US taxa (after Blue Iguanas were excluded as an outlier), Europe had roughly 33% more holdings than the US – a number that rises to 45% more when the two native species also get excluded. That is a result very similar to amphibians, so a pattern is starting to arise…
-----------------------------
And that’s it for now. The next group will be snakes, but realistically I don’t know if I’ll have time to work on them in the next couple of weeks. In the meantime, though, questions and comments are more than welcome
Lizards
I’ve compiled the holdings for what I now believe to be the top two dozen or so most common lizard species in US zoological facilities… probably.
1. (tie) Gila Monster (Heloderma suspectum) – 96 holdings
1. (tie) Inland Bearded Dragon* (Pogona vitticeps) – 96 holdings
3. Prehensile-tailed Skink (Corucia zebrata) – 87 holdings
4. Green Iguana (Iguana iguana) – 85 holdings
5. Blue-tongued Skink (Tiliqua sp.**) – approx. 80 holdings
6. Leopard Gecko (Eublepharis macularius) – 64 holdings
7. Komodo Dragon (Varanus komodoensis) – 59 holdings
8. Common Chuckwalla (Sauromalus ater) – 52 holdings
9. Argentine Black-and-white Tegu (Salvator merianae) – 51 holdings
10. Sheltopusik (Pseudopus apodus) – 43 holdings
11. Rhinoceros Iguana (Cyclura cornuta) – 42 holdings
12. Caiman Lizard (Dracaena guianensis) – 39 holdings
13. Crested Gecko (Correlophus ciliatus) – 38 holdings
14. Henkel’s Leaf-tailed Gecko (Uroplatus henkeli) – 37 holdings
15. Madagascar Giant Day Gecko (Phelsuma grandis/madagascariensis***) – 36 holdings
16. (tie) Mexican Beaded Lizard (Heloderma horridum****) – 35 holdings
16. (tie) Veiled Chameleon (Chamaeleo calyptratus) – 35 holdings
18. (tie) Crocodile Lizard (Shinisaurus crocodilurus) – 32 holdings
18. (tie) Sudan Plated Lizard (Broadleysaurus major) – 32 holdings
20. Emerald Tree Monitor (Varanus prasinus) – 30 holdings
21. New Caledonian Giant Gecko (Rhacodactylus leachianus) – 28 holdings
22. Asian Water Monitor (Varanus salvator) – 27 holdings
23. (tie) Black Tree Monitor (Varanus beccarii) – 26 holdings
23. (tie) Green Basilisk (Basiliscus plumifrons) – 26 holdings
23. (tie) Cayman Blue Iguana (Cyclura lewisi) – 26 holdings
*technically combined Pogona holdings, but all holdings were assumed to be P. vitticeps based on available evidence
**is mostly T. scincoides, with smaller numbers of T. gigas and a single T. multifasciata holding
***includes P. grandis and P. madagascariensis. Both are present in US zoos and were once considered the same species, in the survey their results were combined.
****includes only true/suspected H. horridum, not any of the subspecies that have been elevated to species
Unsurprisingly, top of the list is a Halloween-colored venomous sleepy slug with a bulldog bite. You’d have to put a little cowboy hat on it to make it any more cartoonishly American.
Taken at Dallas Zoo by @GiornoPizza
US Survey Count vs US ZTL Holdings
Comparing my survey holdings to ZTL holdings, my capture rate once again had wide variability. My most accurate count was for Emerald Tree Monitor, with my survey capturing 90% of known holdings (27 of 30). My worst capture rate was for Argentine Black-and-white Tegu, with my survey capturing less than 20% of known holdings (10 of 51) – a very poor result, even by “common pet trade species” standards. Several other common pet lizards – Bearded Dragons, Leopard and Crested Geckos, Veiled Chameleons, Blue-tongued Skinks and Green Iguanas – all fell in the 25% to 33% capture range, so all ended up very underestimated also. Meanwhile, many species found mostly in accredited zoos and/or with captive breeding programs – Komodo Dragons, Black Tree Monitors, Henkel’s Leaf-tailed Geckos, Caiman Lizards and Crocodile Lizards – were all estimated pretty accurately, mostly in the 75% to 80% range. My average capture rate across ~24 common taxa was 57%, so worse than for amphibians.
In my lizard survey recap, I had found 4 species to be Abundant (40+ holders) and 9 species to be Very Common (30-39 holders). Based on current ZTL data, there are actually 11 Abundant and 9 Very Common species, so I definitely underestimated abundance for a lot of these species. Of the 25 taxa whose abundance I evaluated: 11 (44%) were estimated accurately, 8 (32%) were slightly underestimated and 6 (24%) were significantly underestimated. Oh well.
As far as what species are held in what kind of facilities… the first species I checked was the Black-and-white Tegu; unsurprisingly 75% of its holdings are in non-AZA facilities, it is a very common species for small, privately operated zoos and “interactive” aquariums like SeaQuests. The other common pet-trade species (Green Iguana, Leopard Gecko, Bearded Dragon, etc) were all similar, with 65 to 80% of holdings in unaccredited places like private zoos and safari parks, small aquariums, nature centers, science museums and reptile zoos.
Tegu: the cheap man’s monitor lizard. Lots of tiny private zoos in the countryside harboring this black-and-white egg-eating menace.
Taken at Tupelo Buffalo Park by @SusScrofa
Meanwhile, the % AZA holdings on many other species was the mirror opposite: roughly 75-85% of Blue Iguanas, Black and Green Tree Monitors, Caiman Lizards, New Caledonian Giant Geckos and Prehensile-tailed Skinks are in accredited zoos and aquariums, as are over 90% of Komodo Dragon holders and nearly 100% of Crocodile Lizards and Henkel’s Leaf-tailed Geckos. Therefore, as with amphibians there is a large divergence in what lizards are held in different types of zoos.
Once again I tested how much my survey captured holdings overall. I compared the overall holdings between the survey and ZTL for 7 lizard groups:
Anoles: 44/80 (55%)
Monitors (excl. Komodo, Asian Water, Green and Black Tree): 116/188 (62%)
Beaded Lizards: 116/153 (76%)
Phrynosomatidae: 57/72 (79%)
Skinks (excl. Blue-tongued and Prehensile-tailed): 67/86 (78%)
Geckos (excl. Leopard and Crested): 192/250 (77%)
Basilisks: 32/40 (80%)
With capture rates ranging from 55 to 80%, these results were similar to those for amphibians, with an overall average sitting around maybe 70-75%.
US ZTL Holdings vs Europe ZTL Holdings
This time I did not look at native versus exotic, since only 2 of the ~27 species I looked at were native (Gila Monster and Common Chuckwalla). For what it’s worth, both of those species were 40% more common in US zoos than European zoos… so okay, I guess I did look at them separately.
As for the exotics, there was a wide variation. The largest divergence percent-wise was Grand Cayman Blue Iguana, for which there is a robust breeding program here while European zoos only have a small handful of animals. The next largest divergences in America’s favor were Black Tree Monitors and Komodo Dragons, which are ~75% and ~65% more common than in Europe respectively. Komodos are a big one (literally and figuratively!) that I already knew was different; Europe has three dozen holders – with no more than half a dozen in one country – while the US has ~60 holders, now including the majority of large and mid-sized accredited zoos… and with at least a couple new holders still on the way in the next few years!
The new Komodo digs at Nashville Zoo, one of the newest in a line of major American zoos that jumped on the giant lizard bandwagon.
Taken by @cubsmaster
Meanwhile, Europe had larger holdings primarily for the common private trade species – which I’m guessing is either an artifact of more privately operated zoos generally, better reporting thus far on private zoos, or both. ZTL holdings count more than 3x as many Bearded Dragons in Europe, 4x as many Green Iguanas and Leopard Geckos, and 5x as many Veiled Chameleons. There are also (surprisingly to me) 5x as many Plumed Basilisks in Europe and 5x as many Madagascar Giant Day Geckos; I couldn’t really pinpoint a reason why, they just seem to be much more abundant in European zoos than in American zoos.
Did a bunch of European zoos get basilisks after Chamber of Secrets came out, or are plumes just that stylish across the pond?
Taken at Omaha's Henry Doorly Zoo by @DesertTortoise
Another surprising find is that the European Glass Lizard (Pseudopus apodus) was roughly equal between the two continents. In fairness the species is native to coastal southern Europe – i.e. not the countries most zoos are in – but it was unexpected nevertheless, given how many European-themed zoos and zoo exhibits are in the region.
Overall for 24 common US taxa (after Blue Iguanas were excluded as an outlier), Europe had roughly 33% more holdings than the US – a number that rises to 45% more when the two native species also get excluded. That is a result very similar to amphibians, so a pattern is starting to arise…
-----------------------------
And that’s it for now. The next group will be snakes, but realistically I don’t know if I’ll have time to work on them in the next couple of weeks. In the meantime, though, questions and comments are more than welcome
