What is GeckoWatch?

GeckoWatch is a community science project to map the fine-scale distribution of nonnative geckos in the United States. The primary interest is in mapping the rapidly increasing range of the Mediterranean House Gecko, Hemidactylus turcius. However, we are interested in all nonnative gecko species.

There are at least 18 species of nonnative geckos that have established populations in the United States. Although many of these species are known only in Florida, others are showing up with increasing regularity in multiple states. At the most extreme end is the Mediterranean House Gecko, which has established populations in at least 24 states in the continental US.

To undertake any research on these nonnative geckos, scientists must first understand where these geckos occur.  As we learn about the rapidly changing distributions of these nonnative geckos, we can then ask:

  • What are the impacts of these nonnative geckos on our native species?
  • What makes some species successful colonizers?
  • What are the likely routes of colonization?

Observations from community scientists are essential to answering these questions and allowing us to learn about the biology of these nonnative geckos.

Lizard RASCals project

Community Science Participants Discover New Gecko Populations in California

Mediterranean House Gecko

  • First L.A. County record

Indo-Pacific Gecko

  • First California State record
  • First L.A. County record
  • First Orange County record

Through NHMLAC's community science program, we have discovered two gecko species that had not been previously recorded in the Greater Los Angeles Area, the Mediterranean House Gecko (Hemidactylus turcicus) and the Indo-Pacific Gecko (Hemidactylus garnotii).

These geckos are not native to California. The Mediterranean House Gecko, as you would expect from its name, is native to the Mediterranean region of southern Europe, northern Africa and the Middle East. The Indo-Pacific Gecko is native to Southeast Asia, but has been introduced to Australia, India, the Philippines, and Polynesia. In the United States, it has been documented in Hawaii, Florida, Georgia, Alabama, and now California.

These important discoveries were made possible by the keen eyes of our participating community scientists. These community scientists are working with museum researchers to publish their findings in the journal Herpetological Review. You can read about the first of these finds here: Bernstein, W. L. and R. W. Bernstein.  2013.  Hemidactylus turcicus (Mediterranean Gecko). Herpetological Review 44: 374.  

Diversity of Nonnative Geckos in the United States

The project is an outgrowth of a collaborative effort by Robert Espinoza and Jeanne Robertson (California State University, Northridge), Aaron Bauer (Villanova University), Heather Liwanag (Adelphi University), and Greg Pauly (Natural History Museum of Los Angeles County) to examine what factors are allowing the Mediterranean House Gecko to be such a successful and rapidly-expanding colonizer. Although the initial focus was on Mediterranean House Geckos, we realized that similar questions could be asked about any of the nonnative geckos in the United States. The first step to asking these questions is to understand the rapidly changing distributions of these species. And the only way to rapidly collect these distributional data all across the continental US is to enlist the help of numerous community scientists.

Below is a list of nonnative gecko species in the continental United States and the states in which established populations have been documented.

  • Gekko gecko (Tokay gecko).  Florida.
  • Gonatodes albogularis (Yellow-headed Gecko).  Florida.
  • Hemidactylus frenatus (Comon House Gecko).  Florida.
  • Hemidactylus garnotii (Indo-Pacific Gecko).  Alabama, California, Florida, Georgia, and Texas.
  • Hemidactylus mabouia (Tropical House Gecko).  Florida.
  • Hemidactylus platyurus (Flat-tailed House Gecko).  Florida.
  • Hemidactylus turcicus (Mediterranean House Gecko).  Alabama, Arkansas, Arizona, California, Florida, Georgia, Illinois, Kansas, Kentucky, Louisiana, Maryland, Missouri, Mississippi, Nevada, New Mexico, North Carolina, Oklahoma, South Carolina, Texas, Utah, and Virginia.
  • Lepidodactylus lugubris (Mourning Gecko).  Florida.
  • Phelsuma grandis (Madagascar Giant Day Gecko).  Florida.
  • Sphaerodactylus argus (Oscellated Gecko).  Florida.
  • Sphaerodactylus elegans (Ashy Gecko).  Florida.
  • Tarentola annularis (White-spotted Wall Gecko).  California and Florida.
  • Tarentola mauritanica (Moorish Wall Gecko).  California and Florida.

Mediterranean House Gecko History and Research Summary

Mediterranean House Geckos (hereafter, MHGs), Hemidactylus turcicus, have been widely introduced throughout the New World from their native range in the eastern Mediterranean. They were first reported in Florida in 1910 and have since spread as far north as Baltimore, MD and as far south as southern South America. By the 1950s, coincident with the development of the interstate highway system, this species began to spread rapidly westward throughout the humid Gulf States and, most recently, into the desert Southwest and Mediterranean habitats of California. They are currently established in 22 states (21 states in the continental US plus Hawaii) and the primary route of dispersal is apparently as cargo stowaways. As human commensals, these geckos inhabit a niche (often called the “porch light niche”) in the US that is not occupied by any native vertebrate (although some treefrogs do forage at porch lights, this is not a primary foraging strategy for these species); thus, they likely have an insignificant impact on native vertebrates. They may, however, negatively impact populations of their invertebrate prey. Future studies of impacts of MHGs on native species would greatly benefit from increased knowledge of the distribution of this species.

In their introduced range, MHGs occur in extremely diverse climates: from the high humidity environments of the southeastern US to the hot, dry deserts of the southwestern US. Research by GeckoWatch scientists will determine whether introduced MHG populations have evolved physiologically and/or morphologically to adapt to their new local climates. Alternatively, MHGs might be an extremely plastic species with broad tolerances to diverse climatic conditions. To place this work in the appropriate environmental context, however, we must first determine the fine-scale distribution of MHGs and characterize the specific climates they experience. This is where GeckoWatch plays a critical role in our investigation.

Lastly, as we determine the current fine-scale distribution of MHGs in North America through community science, we can then compare the current distribution to historical records to test models of range expansion and understand the time course of expansion for this introduced species.

Distributional Records and Community Scientists Publishing in Peer-reviewed Literature

We have every expectation that GeckoWatch will produce new distributional records including new records for states and counties.  A similar community science project led by several of the GeckoWatch scientists already resulted in documenting the first established populations of Mediterranean House Geckos in Los Angeles County and the first Indo-Pacific Geckos in Los Angeles and Orange Counties. These latter two records also are the first records of this species in the state.

If community scientists contribute observations to GeckoWatch that document an established population of a species in a county or state where it has not previously been documented, the GeckoWatch scientists will work with the original observer to help them publish their record in the peer-reviewed scientific literature.

How to Participate

It is easy to participate in GeckoWatch; all you need to do is follow three easy steps.

  1. Find geckos: Go out and find geckos anywhere in the continental US. Geckos might be in your yard, your neighborhood, or encountered on your travels (Bored at your motel? Go look for geckos! No really, we are not kidding; motels are especially good spots to search for geckos.).
  2. Take pictures: Once you find a gecko, take at least one photo of it. Try to have one photo be close enough so that you or others can carefully examine it to confirm which species of gecko you have found.
  3. Upload pictures or submit via e-mail: Upload your gecko photos to the GeckoWatch Project on iNaturalist or submit them via e-mail at Please include:
  • Date of observation.
  • Location. Because nonnative geckos are often found around structures, a street address can provide a very accurate description of the locality. Latitude and longitude are also very helpful and can be obtained with many newer smartphones and cameras, looked up on Google Earth, or specified using the map function on iNaturalist.
  • Approximate number of geckos observed. A single gecko might simply be a stowaway, but finding multiple geckos, especially if they are of different sizes, indicates an established population.
  • Type of site. Nonnative geckos tend to hang out around human habitations. So let us know if your observation was at a house, motel, building, highway rest stop, etc.

Please note that to upload your images to GeckoWatch on iNaturalist, you will need to create an account on iNaturalist or log in with your Facebook, Twitter, or one of your other social media accounts. There is also an iNaturalist app available for iOS and Android mobile devices. 

iNaturalist is a fun online community in which others can share in your find, comment on your observation, and even help identify the animal you photographed. GeckoWatch scientists should confirm and/or comment on your observation within a few days of you posting it to iNaturalist. We strongly encourage everyone to participate in GeckoWatch through iNaturalist.

For those who would prefer an alternative to submission on iNaturalist, we encourage you to submit your observations via email to We will then upload these photos to iNaturalist under a general account and act as stewards for these important observations. You will receive a confirmation email that also includes a link to the iNaturalist submission.

GeckoWatch Data

To view the GeckoWatch data, visit our project page on iNaturalist. You will be able to view a map of observations that have been submitted, see who has contributed, and how many contributions each person has made. You can also sign up to iNaturalist and start contributing your own observations, help identify gecko submissions, and comment on observations from you and others.  You can also read journal posts from the GeckoWatch team.

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