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- Upon the purchase of a couple different cheaper night-vision devices, it was seen that both used “infra-red” illuminators that are not totally invisible to normal vision. Both units use a red LED. The light that these LED’s cast is very difficult to directly observe (it doesn’t seem to “cast” any red light, even in a dark room), but if the light is pointed near (or right at) your eye, you can see it very plainly as a bright red light. My question is if wild animals would be able to see this light at night. --And of course there’s bazillion-year-old lemurs that weigh a pound and have eyes as big as tennis-balls, who can go outside tomorrow night and see what you did last night–so I guess I should include that I am wondering about Central-USA sort-of-animals.
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- Upon the purchase of a couple different cheaper night-vision devices, it was seen that both used “infra-red” illuminators that are not totally invisible to normal vision. Both units use a red LED. The light that these LED’s cast is very difficult to directly observe (it doesn’t seem to “cast” any red light, even in a dark room), but if the light is pointed near (or right at) your eye, you can see it very plainly as a bright red light. My question is if wild animals would be able to see this light at night. --And of course there’s bazillion-year-old lemurs that weigh a pound and have eyes as big as tennis-balls, who can go outside tomorrow night and see what you did last night–so I guess I should include that I am wondering about Central-USA sort-of-animals.
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- I do know from playing with a red penlight-laser (wavelength unknown, but an older one that now probably sells for maybe $15) that cats can quite plainly see the light from that, and dogs seem to also but aren’t much interested by it. I have not been able to turn up any solid info online, just kiddy-trivia sort of educational blurbs…
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I’m not sure if this sheds any immediate light on the subject (har har) but it at least adds to the data pool: zoos sometimes house small nocturnal animals in darkened red-lit buildings, so that the animals think it’s time to be up and about while there are people at the zoo. After closing time, they turn white (or full-spectrum) lights up in the building, and the animals hide and go to sleep. So these little fellers can’t see red light all that well.
In terms of American animals, I think I’ve seen possums living in such enclosures.
as far as dogs go, I’ve got a green light laser, and my dog’s not too interested in that either. I think dogs just may be less interested in small darting motions than cats. I do have a large dog, who may have different instincts than a smaller one.
Don’t all mammals have the same dye molecules in their retinal cells? If so, then their eyes are somewhat like human’s: needing fairly bright light for full color or “photopic” vision, and using visual purple molecules for dark-adapted or “scotopic” vision.
The graphs show that the human IR sensitivity for daytime vision is high, but it’s really low for dark-adapted vision, even though our sensitivity to blue light is much higher in the dark. If animals use the same molecules as human retinas, they still could have much better night time vision if their pupils were larger, if the rod cells were longer and more numerous, if there was a mirror layer behind the rod cells, etc.
http://hyperphysics.phy-astr.gsu.edu/hbase/vision/bright.html
http://www.4colorvision.com/files/photopiceffic.htm
I hypothesize that this is dependent on the breed of dog, as you suggest. I have two Basenjis, which are considered sight-hounds (that is, they hunt by sight rather than purely by smell). Sight-hounds include other breeds like Greyhounds, whippets, Afghans, etc. As a group, they are generally lanky, built for running and they share some traits that are unusual outside the sight-hound group. One thing I know for sure: my basenjis go wild for the laser pointer! One in particular loves to chase it, even though he seems to realize there’s no food there. He will even chase around reflected bright spots (such as from a watch crystal or mirror) or a flashlight beam for some time before getting bored with the activity. So at least some dogs can clearly see the laser beam and find it interesting.
Another intesting thing I observed once: I had just gotten a new programmable/learning remote control. I sat down on the couch next to one of the dogs to start setting the remote up. When I tested the remote the first time to see if I had programmed it correctly, my dog whipped his head around and started sniffing at the remote like crazy. He continued to show a lot of interest in it as I worked as well. I don’t know if he actually saw something from the LED, but he certainly acted like he saw something that caught his attention. In this instance, the room was fairly dim. The remote differed from my other by not having the plastic IR-pass filter covering the LED. Neither dog had ever shown any interest in any remote control previously, and after a while they lost interst in the new one as well.