Phenology: noun. "The study of cyclic and seasonal natural phenomena, especially in relation to climate and plant and animal life”

There was a very small window of a couple days of “cooler” temperatures last week, so Katie and I took advantage and headed up the Spitler Peak trail — at the north end of Garner Valley. Hiking temperatures were in the high 70s and low 80s – just perfect. The last time I had been there was two months ago, but the intense heat of July and August had taken its toll. Shrubs such as sticky monkey flowers and blue stemmed keckiella at lower elevations looked like someone had taken a blow torch to their leaves, flowers and fruits, but looked increasingly healthy as we gained elevation and shifted to more north-facing slopes. 

We saw 70 lizards, which sounds like a lot, but two months ago we saw more than twice that many. The difference was that the phenology of the entire slope had shifted from the energy of late spring to the “relaxed pace” of mid-summer. Two months ago, the lizards were nearing the end of their active courtship and breeding cycle. It was do it now or wait until next year — if you live that long — sort of energy. Flowers and pollinators were abundant. Life was everywhere. Now the flowers have mostly gone to fruit (unless fried by the heat). Adult lizards were active only long enough to get a meal, and then remained well-hidden; staying active would mean putting themselves at risk of becoming someone’s lunch. Passing your genes on to the next generation was worth that risk two months ago, but now the goal was to stay alive until next spring when the passing on of genes would again be a possibility.

Two months ago, the lizards were making babies and now their labors had come to fruition. Hatchling lizards the size of small grasshoppers darted across the trail every few meters. Whereas an adult lizard might have enough experience to realize we bipedal, lumbering hominids were of little risk and so not worth expending the energy of a quick dart into cover, for hatchlings, everything is perceived as a potential predator, and for good reason. For me, it was particularly interesting to see the different reproductive strategies in play. The spiny lizards — western fence, granite spiny, and southern sagebrush lizards, along with horned lizards and whiptails, all have a reasonable likelihood of breeding over multiple seasons, and so it is important to not put all your eggs in one basket (so to speak). They need to have a balanced strategy of reproducing and surviving to the next year to try their luck again. Side-blotched lizards have a very different perspective. They will almost certainly survive just one breeding season. Rarely, maybe a second season. In a strategic sense, they are not unlike an annual wildflower – you are only going to have one shot at passing on your genes, so you better invest everything in that shot. They must put all their eggs into one basket. The outcome was that side-blotched hatchlings outnumbered all other lizard species hatchlings combined, by 2 to 1.

Given how small the lizard hatchlings are, and how fast they move, lizard surveys this time of year require a good pair of binoculars. Even then identifications can be tough. I am attaching images of the two Blainville’s horned lizard hatchlings we saw, along with one side-blotched and one southern sagebrush lizard hatchling. Notice the side-blotched has a sharper snout, smoother skin, and a skin fold along its flank. 

I’ll finish this week’s essay by passing along my reply to Susan Forgrave (Cal Nat class of 2018) who asked about the abundance of lizards in her yard.

“First, congratulations to you on having designed such a lizard-friendly yard. As to your question, the size and shape of home ranges (or when actively defended, territories) is dependent of the resources available. Generally, that means food, but also includes members of the opposite sex, hiding places, thermal cover refuges from predators, and so on. I can imagine that for a desert lizard living away from human landscapes, at this time of year food is sparse so territories need to be large. In contrast, our human landscapes tend to be much lusher, and if we avoid being stupid and so don’t use pesticides, then food can be relatively abundant. Lizard territories or home ranges can then be smaller. In addition, our walls separating us from our neighbors, are very suitable analogues for cliffs and rock faces, and so provide ideal, linear resources for desert spiny lizards, and provide another way to pack more lizards into a smaller space. Tracy Bartlett proposed that, when we provide lizard friendly landscaping, we may be creating climate change refugia for the lizards, and so allow them to thrive when their brethren at low elevation may not be fairing nearly so well.”

Stay safe, healthy, and it looks like by the end of next week we might get some serious cooling. Celebrate having survived one of the hottest summers on record and take a hike.