Fur and Scales

February 06, 2018 Posted by: Stephanie Root

Every month, biologists and volunteers set out in the coastal sage scrub and perform "herpetofauna monitoring." You might already know that herpetofauna is an all-encompassing word that includes reptiles and amphibians.  The biodiversity of our herpetofauna in Cabrillo National Monument is a great indicator of ecosystem health, and it is important that we do these monthly check-ups - especially since 7 species of reptiles have been extirpated (historically known to occur and now extinct from a particular area) from the park! 

We monitor these animals using a pitfall sampling technique. We put 5-gallon buckets in the ground that are joined by 8" tall drift fencing. The fencing intercepts a critter running along the ground, and as the critter tries to circumnavigate the fence, it will eventually fall into a bucket where it is retrieved the next morning. 

NPS Photo - An NPS ranger checks a pitfall bucket

In 2017, the capture rate of herpetofauna species is about average compared to previous years - we began this study over 20 years ago, in 1995. The map below shows our four most common species: the orange-throated whiptail (Aspidoscelis hyperythra), alligator lizard (Elgaria multicarinata), western fence lizard (Sceloporus occidentalis), and the side-blotched lizard (Uta stansburiana). What is different compared to previous years is the distribution of diversity of the lizards in Point Loma. You can see that the western fence lizard is present at all pitfall arrays, but they dominate the northernmost arrays. In the other locations to the south, the lizards are more evenly distributed. Why could this be? Could it be that habitat fragmentation is still a problem for the remaining species of herpetofauna?

NPS Photo - Distribution of the four most common lizard species at pitfall arrays sampled in 2017 

Some cool things that have happened in 2017 - we caught the first legless lizard and ring-necked snake since 2012! We also happened to catch the first-ever Botta's pocket gopher since the pitfall sampling began in 1995. This was a new animal that we added to our park's species list! We think that because we had so much rain from December 2016 through February 2017, it may have increased the activity of the critters in Point Loma, and the likelihood of us catching them! 

NPS Photo - Stebbins legless lizard (Anniella stebbinsi) from 2017

NPS Photo - Ring-necked snake (Diadophis punctatus) from 2017

NPS Photo - Botta's pocket gopher (Thomomys bottae) from 2017