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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.

Alligator lizard coitus 2021 by iNat user James

Above Image: A pair of mating southern alligator lizards observed by Jacob, Oscar (age 5), and Mae (age 4)  https://www.inaturalist.org/observations/73385631 in their front yard in the Valley Village neighborhood of Los Angeles on April 7, 2021. The male is biting the female’s head and neck region; this is termed the bite hold. Pairs may stay in the bite hold for several days even though mating only takes a small portion of this time. photo: Jacob 

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 alligator 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. 

Six years ago, 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 three 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 538 observations of mating southern alligator lizards, and 98 observations of 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.

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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. The COVID-19 pandemic changed the way people observe nature.
In spring 2020, much of the country was under lockdown, staying home while trying to limit the spread of COVID-19. Not only were people spending more time at home, but with trails closed and travel limited, they were getting their nature fix in their own neighborhoods. The timing of the lockdown almost completely overlapped the spring mating season, and we received more mating observations than ever before. Plus, nearly every observation was from an urban area, whereas in prior years usually only 65–75% of observations were from urban areas. It will be interesting to see where observations are made in the 2021 season while many of us are still spending more time at home but also more able to leave home than last year. 

2. Wet years are the big breeding years.
Although we started this research effort in 2015, people have submitted observations that date back to 2003 (woohoo for digital cameras!). Across these years, what we see are that drier years have reduced breeding activity. For example, the 2015, 2016, and 2018 mating seasons followed below average rain seasons, and we received 32–35 observations of southern alligator lizards in the mating position. But following the wetter 2017 and 2019 winters, we received nearly three times as many observations! 2021 is another very dry year, and early results indicate reduced breeding activity. Mating activity should continue through mid-May in Southern California and through early June in more northern and higher elevation locations, so we’ll have to wait to see the final numbers. 

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 (but we still have more research to do before we are positive this is what’s happening). But how long might a male maintain the bite hold? We now have four reports of pairs together over 48 hours, with the current record being a pair that were in a bite hold for at least 54 hours in an Orange County, CA backyard in March, 2021. 

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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% 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. This year, the season seems to be delayed, and mating pairs should be found in Southern California through early May. For the northern alligator lizard, breeding should occur from early April through mid-June.

Where to look?
Alligator lizards can be found from coastal sand dunes to high elevations in our mountains. And they do better than any other local lizard in urban areas across this range. 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 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 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 photo to nature@nhm.org, or by using #NatureinLA on social media (Facebook, Twitter, Instagram), or by texting us your photos at (213) 663-6632. If you have photos from previous years, please submit those as well.

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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