Warning: This post includes photos of a dead deer, along with invertebrates feeding on and around it. I know that’s not everyone’s bag of chips, so to speak, so this is your chance to wander elsewhere.
Yesterday’s weather was far too pleasant to just watch through the window, so I headed down to our family prairie to see what was happening there. Temperatures were in the 60’s (Fahrenheit) and there were some thin clouds overhead, making it a nice day for close-up photography. I hoped I’d find some insects and take advantage of that.
There were definitely insects moving around. Most were flies and sawflies (non-stinging relatives of wasps) and they weren’t very cooperative photo subjects. The breeze wasn’t helpful either.
I did, eventually, manage to catch one sawfly sitting still long enough to get a decent photo of it. There was another one nearby that looked similar, but without any red on its thorax, which made me wonder if I was seeing two species or males and females of one species. Given the little I know about sawflies, I’m guessing maybe these had overwintered as pupae and had just emerged to mate. No wonder they didn’t want anything to do with me – they had much more important things on their minds!
The most interesting thing I found was a deer carcass behind the dam of our old pond. It had been there long enough that it had been mostly stripped down to bones, but there was some hair left on the skull and legs. Before I found the full skeleton, I came across its lower jaw bones, which I stopped to photograph mainly because I needed something that wasn’t either blowing in the wind or flying away from me.
As I inspected the carcass (because that’s what ecologists do, right?), I spotted a few little creatures crawling around on it and started trying to photograph them. The wind wasn’t a factor, which was nice, but the little buggers didn’t hold still very well, which wasn’t. More experienced carrion-inspectors would surely be able to age the carcass based on the species and life stage of the insects I found, but that’s not my expertise. I was just curious and enjoyed seeing what was there.
My curiosity was piqued further when I started noticing dog ticks (Dermacentor variabilis) in the grass around the carcass. When I saw the first one, I didn’t think much of it, other than to recognize it as another sign of the coming spring. After spotting the fourth one, though, I realized maybe there was something going on. A couple were on the carcass itself, but most were perched on plants within a foot or two of it. There were at least half a dozen. All but one of the ticks were males, but I’m not sure if that’s relevant.
Why would parasites be hanging around the carcass of a deer? There’d be no food value for them, especially this long after death. Maybe it was just chance, and I noticed them because I had paused to pay close attention to a small area. I don’t think so, though, because I didn’t see a single tick around the rest of the prairie, including while lying on my belly trying to photograph flies and sawflies.
As I pondered the question, I tried to think from a tick’s perspective. What if they recognized the value of the dead deer as bait for the kinds of creatures ticks like to feed on? That would be a pretty brilliant strategy. The life of a tick in the middle of a prairie has to be pretty frustrating – just sitting there, perched on a plant, hoping an animal will come close enough to grab onto. If a tick could predict where those animals were going to be, that would be of tremendous benefit.
After returning home, I went to the internet to see if there were records of this phenomenon. Sure enough, I found this study, and this one, which both reported finding ticks near carrion (mice and a porcupine, respectively) and the second paper cited an additional researcher who had found ticks around a white-tailed deer carcass. None of them had definitive answers for why the ticks seemed to be attracted to carrion, but my hypothesis matched some of theirs, which was nice to see.
I know ticks aren’t most people’s favorite creature and that’s perfectly understandable. On the other hand, they’re fascinating little invertebrates that have developed their own effective strategy for surviving in a complex and challenging world. If ticks have evolved the tendency to cluster around dead animals as a way to increase their likelihood of encountering the live animals they need to feed on, I think that’s pretty amazing.
If you’re in Nebraska, there’s a great community science project you can help with, aimed at building better understanding of what tick species are in Nebraska, and where. https://ticktaggo.unl.edu/
The Prairie Ecologist 
You might be interested in this article.
Perhaps the ticks or their parents came from the dead animal and were waiting for the next host.
Thanks for yet another interesting newsletter. I happened upon a rabbit carcass on our campus this morning, exposed by melting snow. Now I want to go back to see what else is feeding on it or simply dwelling near it.
Agreed — I find ticks to be esthetically repulsive, but evolutionarily fascinating.
The blogger ‘reluctantarchaeologist’ has done research on ‘who’ scavenges animals and how far the bones are scattered. I saw the same thing on our property when a deer died. Over the years the bones were dispersed quite far!
Just wondering could it be that the ticks you saw near the deer carcass were not attracted to the carcass but instead were fleeing the carcass for the hope of finding a new victim.