Chuck Gackstetter, a year-round camera trapper from southwest Minnesota was good enough to send me this amazing image. It was taken with his home-brewed camera trap, a Sony P41 with a Snapshot Sniper control board in a camouflaged Pelican case. (Thanks again, Chuck.)
Most of the insects look like mosquitoes, but the lighter-colored ones may be deer flies. (Entomologists please weigh in).
If that doe was running from the insects, she's didn't seem to be shaking them off.
A picture like this makes you wonder how much blood a deer loses to mosquitoes. I recall reading long ago that arctic mosquitoes could actually kill a caribou. It sounds a bit far fetched.
Mossies can double their body weight after a blood meal, and the mossie known as Culex pipiens pallens sucks as much as 7.1 milligrams of human blood at a time. Thus, a thousand mossies could siphon off about 7 grams of blood, or a quarter ounce. That doesn't sound lethal. It would take a lot more than that to drain a deer to the point of death, but I am not going to claim it is impossible.
So what about Minnesota's deer gleaning bats -- the ones presumbly feeding on blood filled mosquitoes? Up there in northern Minnesoata, Willy4003 posted yet another picture of a bat and deer. (You may have to register with Pixcontroller to see it-- not to worry, it's free.)
It's known that mosquitoes (Anopheles gambiae, to be exact) fly more slowly when carrying larger blood meals than mossies with smaller payloads. They are also more vulnerable to predation by jumping spiders.
And bats? It seems likely that insectivorous bats can discriminate blood-fattened from light-weight mossies using sonar, and may also find the fat slow ones to be easier pickings.
Is this the route that led to phlebotomist bats? If eating blood-sucking insects gave ancestral vampires a taste for blood, how did they make the transition to biting the insect's prey?
The most likely explanation is that they started to feed on insects that were in the act of drawing blood themselves. If so, it seems more likely that the parasite was not a mosquito, but a biting fly like a tabanid. (Blood sucking leeches seem far less likely candidates).
Why? Because biting flies leave bloody wounds. Mosquitoes are better phlebotomists. They don't leave a trace of blood unless crushed on the spot. Bat eats blood-bloated fly . . . bat licks bloody wound . . . bat nips skin . . . bat becomes vampire. That might have been the evolutionary scenario in deep time.
PS: I would have liked to consult the literature on this topic, and apologize for arm chair theorizing. I realize that another route to vampyry is for a bat specializing on small mammal prey (like Megaderma spp) to switch to increasingly larger prey. If any readers can refer me to relevant references on this, please let me know. I'll chase down the refs next time I am in the bay area.)
Bekku, Hisao. 19__?. On the amount of blood taken up by a female mosquito of Culex pipiens pallens Coquillett, Nagasaki Iggakai Zassi, XXVIII(9):1036-7
Roitberg, Bernard D., Mondor, Edward B., and Tyerman, Jabus G. A. 2003. Pouncing spider, flying mosquito: blood acquisition increases predation risk in mosquitoes. Behavioral Ecology, 14(5): 736-740