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Native Californian, biologist, wildlife conservation consultant, retired Smithsonian scientist, father of two daughters, grandfather of 4 small primates. INTJ. Believes nature is infinitely more interesting than shopping malls. Born 100 years too late.

Sunday, July 27, 2008

Deer, flies, bats and phlebotomy

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


tai haku said...

Hey CTC. I think your theorising may be on the money - Darren Naish had a post up at Tet Zoo noting a similarish set of developments in the behaviour of one of the african oxpeckers I believe

Opa said...

I have seen reindeer in northern Sweden to forgo feeding and stay on snowpatches above vegetated areas all day to escape the zillions of mosquitoes.
Yngve Espmark described reindeer in his field station running themselves to exhaustion, even death, when trying to shake off mosquitoes tormenting them.

Beverly said...

Chris, I’d heard the same thing about mosquitoes killing creatures, but not so much as draining them dry as driving them crazy. Look at that poor thing; I’ve heard they will run themselves ragged trying to escape the biting insects.

...I like your arm-chair theorizing; I bet your on the money, too!

Great stories; thanks.

Neil said...

One of the reasons the North Slope of Alaska is supposed to be so important to caribou is that sea breezes deter mosquitoes. Incidentally, nose-bot flies are also supposed to factor into caribou mortality by obstructing airways and leading to suffocation! I think I'll take mosquitoes...

Of course, direct lethality imposed by the activities of biting insects must be minor compared to their importance as vectors of microbial pathogens.

Here is the link to the Tet Zoo article on the origins of sanguivory

Camera Trap Codger said...

Thanks for the feedback, and the link back to Darren's brilliant summary -- which appeared before I discovered his blog. I'm pleased to know that my own theorizing finds agreement with Darren's assessment. Regarding Fenton's hypothesis, I have examined a lot of mammals in the field over the years, and have encountered external parasites much more often than festering wounds. But my field experience is mostly in Asia, so I won't press the point. In support of the ectoparasite feeding hypothesis (Darren's hyp. #2) however, let me point to the sharp-beaked ground-finch (Geospiza difficilis), a sanguivore from the Galapagos Islands that 'parasitizes' marine birds. Bowman and Billeb make the case that the behavior evolved from feeding on parasitic louse flies. But getting back to proto vampires, I want to emphasize that tabanids are crude phlebotomists and a certain amount of bleeding often follows the bite -- a natural event that could have linked feeding on sanguivorous parasites to feeding on the hosts. I've witnessed elephant - tabanid interactions many times in elephant camps in SE Asia. There were plenty of pachyderms and louse-ridden giant birds in South America.

Bowman, R. I., and Billeb, S. L., 1965. Blood-Eating in a Galapagos Finch, The Living Bird, 4:29-44.

Thanks to my old buddy, Rich Tenaza, who still had a copy of the above reference. We were both students at SF State when Bowman and Billeb made the bizarre discovery.

T. Laurel Sulfate said...

Fascinating entry!

I don't know if mosquitoes can kill an animal through blood loss alone, but I know fleas can. As a veterinary assistant, I saw two dog deaths by flea anemia. They were horrible, and cleaning up after them was worse.

Sean said...

Very interesting piece CTC. I looked like that deer on Saturday. The mosquitos and deer flies are unusually thick this year in Minnesota.


Camera Trap Codger said...

I used to look like that too, esp when in the tropics. Then I got dengue fever. That adjusted my "field man attitude" about machismo and mossies.

phlebotomy technician said...

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