Prairie dog towns are known to provide habitat for many species of plants and animals. Some of those are attractive and/or popular wildlife species like burrowing owls and ferruginous hawks. Others are attractive (at least to me), but maybe less popular among the general public, including prairie rattlesnakes and black widow spiders. It’s easy to understand why rattlesnakes would appreciate the availability of burrows. The snakes can sun themselves on the bare soil at the edge of a burrow, but quickly retreat underground to cool off or escape predation. From the perspective of spiders, I’m sure the burrows funnel insects nicely into webs, but I’m not sure why prairie dog burrows are so attractive to black widows in particular. I’ve spent a fair amount of time looking for invertebrates around Nebraska, but prairie dog towns are the only places I’ve ever seen black widows.
While I was up along the Niobrara River last week, I walked around a small prairie dog town hoping to find either rattlesnakes or black widows to photograph. I didn’t find any snakes, but did find black widows in two of the first 20 or so burrows I examined. Both had webs strung across abandoned burrows. That makes sense, but I wonder if the spiders recognize the burrows as abandoned before they build a web? If not, I imagine there are some pretty interesting prairie dog/spider interactions as prairie dogs burst in or out of burrows and encounter the webs. I laughed about something similar with badgers and spiders about a month ago, but the more potent venom in black widow spiders adds an extra degree of risk to prairie dogs… My guess is that very few, if any, prairie dogs are actually harmed by black widows (the spiders probably just try to get away and prairie dog fur seems thick enough to protect against the small fangs anyway) but I don’t know of any research that’s actually investigated that.
Once I found the two black widow spiders, the next challenge was figuring out how to photograph them. The first issue was that the late afternoon sunlight was very bright and the tunnels were very dark, making the lighting conditions problematic. A homemade collapseable diffuser (thin fabric sewed to a plastic hoop) helped cut the light intensity. The second problem was that the angle of the webs relative to the shape of the burrow made it difficult to get the spider in focus. I finally gave up trying to find a position from which to photograph the first spider and concentrated on the second.
However, the biggest issue was that the spiders were very tuned in to movement near the edge of the burrow and kept scurrying away into the shadows every time my head, camera, or hand moved across the opening. The above photo took 45 minutes to obtain. Most of that time was spent waiting for the spider to return to the web (and the light) every time I re-positioned the camera, focused, or breathed (or so it seemed). It’s not a fantastic shot, but given the challenging situation it still feels like a kind of victory.
I moved a couple of them with me when I came from New Mexico. I think they’re really cool. I was told they are very place-based and territorial year after year. We had a female guard her eggs right above the back door. That’s the only time I saw her. When there weren’t any eggs she was super shy and elusive. Guess you got a taste of that!
That is very interesting Chris – – particularly whether or not they can detect used vs. unused burrows in some way. You would think there would be a lot of evolutionary pressure for them to be able to detect unused burrows, or at the very least move on to another burrow fairly quickly if the first web was disturbed. Maybe it is a matter of chance and a lot of them just don’t survive . . .
I think the photo looked pretty good!!
I think the clarity of the shot makes this spider photo an excellent one. Thanks.
Are you really disappointed with your Prairie Dog Spider photo, Chris, or are you putting us on because it’s so incredible? For me it’s the next best thing to seeing the real thing!
Oops, I forgot to ask a question in my comment above. Looking at the SD Spider’s last pair of legs, it appears that there are “extensions” that have emerged from within the legs. What is happening here? Is something “fooling my eye” like an unusual angle of light, or are the spider’s back legs really that long?
Those are the tarsus segments of the hind legs, Chris M., differently lighted from the remainder, so the legs really are that long. The hind legs are essential tools for catching prey. Once the beetle or whatever gets tangled in the sticky strands attached to the ground, the spider uses her first two pairs of legs to reel in the prey, then turns around and deftly throws sticky threads on the struggling prey to immobilize it with glue, then wraps it by placing swaths of non-sticky threads over it while spinning the prey with middle two paira of legs. Only after wrapping does she go in for the bite, usually delivered on a now immobilized leg joint. This complex series of behaviors explains why it is so rare to be bitten by a black widow. She just can’t get through the right behavioral sequence to get to the biting part (that is, unless directly trapped against the skin, and delivers a defensive bite).
Some years ago, on a family visit, I happened to notice that the western black widow (Latrodectus hesperus, which this one also appears to be) is the most common spider nesting in cracks at the bases of walls and building along trendy State Street in Santa Barbara CA. All the tourists, celebs, yuppies, hippies, students, and every other sort of people walking by never notice, because of the shyness of these spiders, so well illustrated by Chris’s story.
Thanks, James, for taking the time to explain this to me so well — very interesting! Someone had suggested that the back legs are used somehow in the “catching,” but I just didn’t get it since I don’t know spiders as well as I’d like. Thanks, again, James — your explanation was exactly what I wanted to know.