The drought has been awful for Southern California residents: dry, hot days, water restrictions, and a brown landscape. These are things we can all live with, but for our resident native reptiles and amphibians, drought can be a life-or-death situation. I have been working in the San Diego Zoo Safari Park’s Biodiversity Reserve (a 900-acre area adjacent to the Safari Park) for 15 years studying the reptile and amphibian species that call it home. This year I began a project studying a relatively rare coastal sage scrub species, the coastal patch-nosed snake Salvadora hexalepis virgultea. My plan was to capture at least 10 animals and implant them with radio transmitters so I could follow their movements and study their ecology. On normal rainfall years I see an average of eight of these wonderful snakes, so I figured that if I actively searched for them, I would be able to get a good sample size to study. However, I did not count on the drought being so intense.
Snakes get most of their water from the food they eat, and when there is no water, the food disappears as well. Many of our small, native animals tend to stay underground during such “tough times” and await better weather. Not only did many of the prey species disappear over the spring and summer, but the snakes also stayed deep underground to conserve moisture. Some snakes and other reptiles came to the surface for a brief period during the breeding season (April through June), and I was able to find a couple of patch-nosed snakes for my study. Unfortunately, reptile activity ceased altogether soon after. On a good spring day in a year with normal rainfall, I can find up to 20 snakes belonging to 8 to 10 different species in a single day. This year, in stark contrast to normal expectations, my best snake day yielded just two snakes. In addition, I spent nearly every day in the field for seven weeks in May and June and only saw two rattlesnakes. As the summer progressed and the habitat became more and more dry, very little lizard and snake activity was observed.
August is often our driest month, so we rarely see many animals in the field at that time. We often wait until late September before we start seeing hatchlings and juveniles along with occasional adult animals. This year, the young snakes have been virtually nonexistent, and that makes sense. If the adult female snakes and lizards cannot gain enough body mass, they generally will not reproduce. Since most of our wild animals stayed underground for much of the year, they probably did not feed and therefore were unsuccessful in breeding.
Last week I saw firsthand how difficult the drought has been on our native snakes. While walking through the coastal sage, I found a large, female red diamond rattlesnake Crotalus ruber. She was very thin and could barely move. I presume she had recently given birth (rattlesnakes in San Diego County give birth to live young in August and September) and just did not have enough body mass to make it through her pregnancy. No baby snakes were found in the vicinity, and I can only hope this female pulls through. If she had babies, they will, hopefully, be able to hold out until the rains eventually arrive.
In over 30 years of field “herping” (searching for reptiles and amphibians), I have not experienced drought conditions worse than those seen in 2013 and 2014. In fact, the North American Field Herping Association has shown just how bad the drought has been on Southern California snakes. When comparing non-drought year data from July 1, 2010, to June 30, 2012, with drought year data from July 1, 2012, to June 30, 2014, for snakes found in Los Angeles, San Diego, Orange, San Bernardino and Riverside counties, 4,971 snakes (1,055 hatchlings) were found between 2010 and 2012 whereas only 2,888 snakes (680 hatchlings) were found from 2012 to 2014. It is also interesting to note that there were more contributors to the database in the latter years, so roughly half the snakes were found by considerably more field herpers in the drought years than in the normal rainfall years, and roughly half the hatchling snakes were found in the drought years than in the normal years.
So what does this all mean? Nobody can be certain right now. We do know that our climate has boom and bust years and drought and rainfall totals are very cyclical for most areas of the world. However, our findings to date do suggest that climate change is occurring at a rapid pace, and we all need to do our part to protect the environment and our natural resources, especially the snakes!
Jeff Lemm is a senior research coordinator in the Behavioral Ecology Division of the San Diego Zoo Institute for Conservation Research.