Look at this handsome fellow. About the size of my palm, I spotted him crossing the trail about two miles from my house, on the west side of the Diablo foothills. I was gobsmacked; I had never seen a tarantula in the wild before. Aphonopelma iodius are a fairly well-known entity around these parts - many people flock to Mount Diablo in the fall to see the annual tarantula ‘migration.’ This is a misnomer. The spiders do not migrate; the males leave their burrows in order to find a mate. Tom and I (and the kids, and my parents) have been on several tarantula ‘hikes’ which are held every year on the east side of the mountain. We’d seen burrows, we’d seen webs, but never an actual spider.
And then, today - Tom and I saw two (!) on another trail on the west side of the mountain, this time in a canyon before we started heading up a steep section. These two were also males (naturally, because it’s only the males that travel to find mates), but they were younger and smaller than the one I saw a week ago. Tom was just as giddy as I had been when I saw the first one. We really didn’t know that we’d be able to see them in broad daylight, on well-traveled trails.
This annual ‘migration’ used to happen later in October, coinciding nicely with Halloween and giving everyone some seriously spooky vibes. But due to climate change, it’s now happening earlier and earlier each fall, and in fact, now in late summer. I don’t know if our recent heat wave had anything to do with our seeing them so frequently (acting as some sort of trigger, maybe?), or if this is a typical occurrence on these particular trails, and we just happened to be in the right place at the right time.
I wrote my final college paper on our local tarantula population. It was a study design; my imagined study would make a definitive count of the number of female spiders in one particular section of the park. I thought you might be interested to read it, or at least the first third of it, which explains more about the biology and behavior of Aphonopelma iodius, and the conclusion, which discusses the phenomena of earlier mating seasons.