2023 Year in Review for “Lizards of the Amazon Region” project

This entry is an overview of what this year provided for the Lizards of the Amazon Region project. I start with a brief review of the lizard observation data over time followed by review of data on the community of identifiers/observers for the project before mentioning some notable 2023 observations. Notable observations include notable firsts, neat lizards, neat behavior, and neat interactions. As always, feel free to join the project to receive future updates.

REVIEW OF DATA ON OBSERVATIONS

As of December 31, 2023, this project had 17,464 lizard observations from the Amazon region of which 4842 were added in 2023. Here's a color heat map showing the 2023 observations and their sporadic, wide-ranging locations of origin.

The five most commonly observed Amazonian lizards account for a third of the total observations, and 15 species account for half of all observations. Yet, 2023 saw observations of 187 total lizard species in the Amazon (of the 259 currently added to iNaturalist and of the over 300+ described Amazonian species). This means the other half of observations came from 172 lizard species with another 73 known lizard species simply not observed in 2023.

Of course, there are a number of unknown or not yet observed lizard species in the Amazon. In order, to clarify how many unknowns there are, I assembled annual data from the lizards in the Amazon region. Annual data (starting with the earliest observation of an Amazonian lizard in 2011) are provided below for total number of observations that year, the percent of total that year represents, the total number of lizard species observed, and the percent change in observation number from the previous year (Table 1).

Table 1: growth in observations of Amazon lizards over time.

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The data in Table 1 reveal several things.

First, there has been solid growth in observations added to this site over time. Nearly every year is a record year for lizards of the Amazon.

Second, each of the past two years have added about a quarter of all observations. Another quarter of observations were added in the combined two years before that. Thus, 75% of observations were added in the past four years.

Third, we, as a community, have not yet seen all of the lizards possible in the Amazon. That is, there are a number of unknowns not yet added to this project. Continued strong growth in the total species observed (259 Amazonian lizards and counting!!!) suggests there are quite a few additional species to be observed. This site has been adding about 20 lizard species per year with no signs of slowing. My ID tips now cover 286 species, so there are at least 25-30 species not yet observed on iNaturalist. I estimate there are well over 300 species of lizards in the Amazon in total.

Fourth, the pandemic probably slowed the addition of observations to this site in both 2020 and 2021. In particular, 2021 seemed to have fewer observations added than expected.

Fifth, the annual growth of observations is about +400 more observations each year. This is consistent with the weekly total of lizard observations from the Amazon (estimated from "Obscure Amazonian Lizard Observation of the Week”). For the past 15 weeks the average is ~96 observations added per week. If this rate holds, we can expect over 5000 Amazonian lizard observations to be added in 2024.

Observations are not the only kinds of information reviewable for this project The identifier and observer communities can also be reviewed for trends. I do so below.

REVIEW OF DATA ON IDENTIFIER/OBSERVER COMMUNITIES

One of the interesting things about iNaturalist is how data can be generated and used. As of December 31, 2023, this project has been aided by nearly 4500 observers with nearly 1600 identifiers aiding in the identification process, for which we are forever grateful. Below is a table showing how the number of users of this site, both identifiers and observers, has grown and changed over time (Table 2).

Table 2: growth in identifiers and observers of Amazon lizards over time.

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The data in Table 2 reveal several things.

First, the number of identifiers grew slowly but steadily at first, but has recently plateaued. The annual number of identifiers has been steady at about 400-500 users each year for the past five years. Regardless, we now have nearly 500 IDers in 2023...a record.

Second, the number of annual observers has continued to grow exponentially on iNaturalist. In the past five years, the number of annual contributing observers has doubled to over 1500 users.

Third, in 2018 the sum of observers exceeded the sum of identifiers for the first time. The cumulative number of observers is now 3X that of identifiers (3:1). For comparison, the ratio of observers:identifiers for Central American lizards is 4.5:1 and for U.S. lizards 6.5:1. So a ratio of 3:1 for the Amazon is perhaps quite good.

In 2023, the first year of this project, the focus was on identifying the existing observations of lizards in the Amazon region. This turned out to be a gargantuan task at first that became easier and easier with the ongoing help of the many talented identifiers on this site. Here are a few I especially thank upon whom I’ve come to rely for their advice: @marco_sena , @mauricio_ocampo, @ccostah, @agbentley77, @johngsalamander, @guillaume_delaitre, @enricotosto96, @rojas-runjaic, @aaronhgriffing, @juanariasbermeo, @rodriguerz, @volpe00, @leandromoraes, @felipe_barrerao, @christianmarty, @vincentpremel, @rlangstroth, @feranolis, @esteban_koch, @a_f_r, @sullivanribbit, @vitorcdg, @dbocanumenthe, @mario_yanez_munoz, @zanelibke, and many others too numerous to list. Thank you all for your observations and identifications.

As this project progresses, another goal is to expand participation in terms of identifiers and observers. To aid in that, I have built out a library of identification tips assembled based on my reading of sources such as "The Reptile Database" (spearheaded by @uetz) and others. I have augmented these sources with original species descriptions in some cases, or based on my own knowledge and experience with the lizards of the Amazon. Throughout I have linked to iNaturalist observations to illustrate my points.

Because there are so many species to deal with in the Amazon, I intend my identification tips to be reference notes that grow and developed as the community grows. These tips now include mention of ~290 lizard species and will continue to grow as new species are described or observed on iNaturalist. I have prioritized visual traits that are more likely to be visible from the kinds of photos posted on this site and tried to make particular mention of distinguishing similar-looking species. If you have any questions or comments about these tips, or just want to point out any issues, please do not hesitate to contact me @petezani.

2023 HIGHLIGHTS

NOTABLE NEW SPECIES

In 2023, iNaturalist added nearly 20 species of lizards to the Amazon to bring the total to nearly 260 species across the region. New additions in 2023 include:

Alopoglossus andeanus

Enyalioides anisolepis

Gymnophthalmus vanzoi

Liolaemus wari

Marinussaurus curupira

Potamites juruazensis

Potamites ocellatus

Urostrophus chungarae

Wilsonosaura

NOTABLE OBSERVATIONS

NOTABLE FIRSTS

This, the first observation of Urostrophus in the Amazon on iNaturalist and helped this project surpass 250 species present in the Amazon. While the photo is from an older date, these kinds of observations are always welcome as well.

Similar to the above, here is a nice series of three observations of Enyalioides anisolepis. This species was just confirmed on iNaturalist for the first time in the latter part of December, so is a quite recent addition.

NEAT LIZARDS

It is easy to overlook observations from early in the year so I went back specifically to find interesting sightings from January and February to find these two Uracentron flaviceps [Tropiduridae] and Hoplocercus spinosus [Hoplocercidae]. Check out the tail on these two lizards, which are not even in the same lizard family. Uracentron has two species...U. flaviceps and U. azureum. Some authorities nest Uracentron within Tropidurus making this a likely case of convergence. Uracentron is an ant/termite specialist found in the canopy of Amazon rainforest trees. Hoplocercus is monotypic and more of ground lizard in the drier areas to the southeast of the rainforest.

Baby lizards are always cute and fun, but sometimes hard to identify. More importantly, they are a valuable window into the life history of these animals, specifically the timing of when these start to show in a population.

NEAT BEHAVIOR

Observations that show some aspect of behavior are always a bonus. Here are some neat examples:

Another valuable type of observation is courtship or mating behavior. Especially useful are copulations for sexually dimorphic species. These observations are valuable in terms of when these type of behavior occur.

Kentropyx as a genus is much more of a climber than in Ameiva as shown here, here, here, and here. In some cases good photos of behavior like this can aid in the identification process. Another example is the aquatic behavior of Crocodilurus amazonicus illustrated here, here, and here, or this one of a nearly 1-m long adult Crocodilurus sitting on one of the Amazonian giant waterlily.

Some lizards, like the Teiidae sleep underground, but many many different species of lizards sleep above ground on really thin twigs or leaves, usually perched 1-2 m high. Behaviorally, this is likely a defense against night-active predators like snakes. A thin twig or leaf will move if a predator approaches and the lizard will just away into the night...and probably terrified. Hence, some of these snakes are especially thin and light, like this Imantodes consuming an Anolis. The variety of lizards in 2023 big and small using this nighttime defense strategy can be seen here, here, here, here, here, and here. Sometimes this makes IDing harder because lizard colors can change while asleep. These have lead to some really gorgeous observations such as here and here. But if you ever find yourself in a place like this keep this in mind....it can be a great way to make observations.

NEAT INTERACTIONS

Here is a really neat observation of two Cnemidophorus fighting. These types of behavioral interactions allow us to determine when males may be competing for mates.

Predator-prey interactions are always fantastic observations as illustrated here, here, here, and here. These include foraging by lizards, such as here and here.

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Posted on Ιανουάριος 01, 2024 0418 ΜΜ by petezani