Look Out for Amorous Alligator Lizards
Spring is mating season for alligator lizards. From Baja California to British Columbia, we need your help to study their mating behavior in the 11th and likely FINAL year of this long-term project.
Updated April 14, 2025
Originally Published April 16, 2021
Above Image: A pair of mating southern alligator lizards observed by Jacob, Oscar (age 5), and Mae (age 4) https://www.inaturalist.
SOUTHERN ALLIGATOR LIZARDS CAN BE FOUND FROM NORTHERN BAJA CALIFORNIA TO SOUTHERN WASHINGTON, AND THEIR CLOSE RELATIVE, THE NORTHERN ALLIGATOR LIZARD, CAN BE FOUND FROM CENTRAL CALIFORNIA TO SOUTHERN BRITISH COLUMBIA. IN URBAN AREAS, INCLUDING THE GREATER LOS ANGELES AREA, THEY ARE THE MOST WIDESPREAD LIZARDS.
Within the ranges of these two alligator lizard species are a handful of major museums, hundreds of universities, and thousands of biologists, so you might think we must know everything there is to know about these relatively common lizards. Unfortunately, like most other species on this planet, we still have a huge amount to learn about the basic natural history of alligator lizards.
In 2015, we realized that we could use crowdsourcing as a way to study mating behavior. At that time, in the entirety of the scientific literature, there were only four dates reported for when southern alligator lizards had been observed breeding. We knew we could get more observations through community science, by crowdsourcing the study of this rarely documented behavior. We started asking people to send us photos and videos of mating pairs. We have now accumulated over 950 observations of mating southern alligator lizards, and over 200 observations of mating northern alligator lizards. We are pretty sure that through community science, we have generated the largest dataset ever on lizard mating. This result demonstrates the incredible value of community science for studying rarely observed natural history events.
Madeleine Claire Doney https://www.inaturalist.org/observations/73466001 found this pair of northern alligator lizards at Point Lobos State Natural Reserve in Carmel, California on April 6, 2021. This pair is in a bite hold, but they are not mating.
photo: Madeleine Claire Doney
WHAT HAVE WE LEARNED WITH ALL THESE OBSERVATIONS? HERE ARE THREE DISCOVERIES SO FAR.
1. Wet years are the big breeding years.
The 2015, 2016, and 2018 mating seasons followed below-average rain seasons, and we recorded 30–40 observations of southern alligator lizards in the mating position (i.e., the bite hold, shown in the above images). In contrast, the 2017, 2019, 2020, 2023, and 2024 mating seasons followed wet winters, and we recorded nearly three times as many observations! In the 2019–2020 and 2021–2022 rain seasons, Southern California experienced very high rainfall in December and then very little rain in January and February, but we still received a large number of observations. This suggests that the lizards are responding not just to rainfall, but to early-season rainfall. Good December rains yield springs with lots of lizard mating activity.
2. Weather has a big impact on mating activity.
Cooler and wetter weather can shut down mating activity until conditions improve. For example, in 2015, most of the mating activity in Los Angeles, Orange, and San Diego Counties took place between March 11 and April 17, but we received no reports for two week-long periods during which large storms swept through the region.
3. Lizards can stay paired up for over two days!
The actual act of mating likely takes place shortly after the lizards pair up. However, the male maintains the bite hold for a long time. This is most likely a type of “mate guarding”, in which the male is trying to make sure that no rival males try to mate with the female. Pairs in prolonged bite holds can also mate multiple times. But how long might a male maintain the bite hold? We now have eight reports of pairs together over 48 hours. The current record is (sort of) shared by two pairs that were each observed together for 54 hours! One pair was observed together for 54 hours in an Orange County, CA backyard in March 2021, and the other pair was observed together for 54 hours and 1 minute on a San Diego County front porch in April 2023!
WHY IS 2025 THE FINAL YEAR OF THIS STUDY?
In spring 2024, we announced that the 2024 mating season would be the 10th and final year of this long-term study, but then we experienced unprecedented weather, and we just couldn’t stop the project. The 2024–25 rain season was incredibly dry in Southern California, while Northern California received above-average rainfall. We know that rainfall has a big impact on the timing of the mating season and on the number of pairs that mate. With much of Southern California experiencing the driest start to the rain season on record, we just had to keep the study running for one more year. It takes a lot of time to advertise the project and process observations, so we do want to transition from data collection to analysis. Assuming nothing else happens that motivates us to go for a 12th year, the 2025 mating season will be the 11th and final year of this study.
Early results are already quite interesting. The 2025 mating season is the latest start to the mating season compared to the prior 10 years of this study, and 2025 is also the first year when mating Northern Alligator Lizards were documented mating before Southern Alligator Lizards were observed mating. Normally in drought years, mating season starts earlier, but this year, we are seeing a different pattern—it appears to have been so dry that breeding was dramatically delayed and is only starting after the better rainfall in late February and March.
Cheryl Peach https://www.inaturalist.org/observations/73396823 observed this pair of southern alligator lizards in a bite hold in her Escondido yard on March 23, 2021. Note that this pair is in a bite hold, but they are not mating.
photo: Cheryl Peach
What to look for?
During mating season, males search out females. The male bites the female on her neck or head and may hold her this way for several days. Early in the encounter, the two may engage in a bit of a wrestling match (if you see this, please try to get videos). Sometimes, a second male shows up and we get even more interesting observations! About 9 percent of all observations in our dataset have two males and a female.
When to look?
Because we have accumulated so many observations, we now know that the southern alligator lizard mating season can start as early as early February in the southern part of the range and continues into early June in the northern part of the range and at higher elevations. In Southern California, most of the breeding activity is between mid-March and late April. In dry years, mating activity starts earlier, but following better rain seasons, mating activity usually begins in mid to late March. In 2025, however, the season is quite delayed in Southern California, so people should keep looking through April and May.
For the northern alligator lizard, we don’t see mating activity in the south-to-north and low-to-high elevation patterns that we see in the southern alligator lizard. Northern alligator lizards can be breeding on the same day in Santa Cruz, CA, and on Vancouver Island, British Columbia. Pairs are most commonly found between early April and early June.
Where to look?
Alligator lizards can be found from coastal sand dunes to high elevations in our mountains (southern alligator lizards rarely get above 8,000 ft in elevation, but with community scientist Joseph Esparza, we documented this species at 10,300 ft in the San Jacinto Mtns; northern alligator lizards can range to about 10,500 ft). Southern alligator lizards do better than any other local lizard in urban areas across their range so they are in many neighborhoods. When in the bite hold, pairs are often found out in the open, on driveways, sidewalks, lawns, and in yards. It is also possible to find pairs several feet off the ground on fences and in shrubs
How to document? Take photos!
If the pair is wrestling, or otherwise being active, please take a video as well. We are especially interested in how long pairs remain in the mating hold, so please check back every few hours and search for the pair in the general area. If you find them again, please take a photo each time you encounter them so that we can assess whether they are mating, or in the bite hold, but not mating.
If you see courting or mating alligator lizards, please take photos and ideally also a video if they are being active. Then upload these to iNaturalist if you are already an iNaturalist user or send them to us at the Natural History Museum by emailing the photos to nature@nhm.org. If you have photos from previous years, please submit those as well. We have received observations that date all the way back to 1974.
Danna Santos https://www.inaturalist.org/observations/73464347 observed this mating pair of southern alligator lizards in San Diego on April 4, 2021. This pair was found in a backyard in a residential neighborhood, highlighting that interesting nature observations can be made anywhere, as long as people choose to observe.
photo: Danna Santos
