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Old April 1, 2013, 05:49 PM   #11
Double Naught Spy
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Join Date: January 8, 2001
Location: Forestburg, Montague County, Texas
Posts: 10,461
Something to consider is that judging behavior as a means of assessing capabilities is not a valid measure for capabilities. Just because a deer, hog, coyote, bobcat, etc. should be able to see you and does not run off does not mean you are invisible to it or even unrecognized. A simple explanation is that you are simply not perceived as a threat. If you are not perceived as a threat, the animal may not respond to you in a manner that you would think is indicative that it can see you.

I have been through a bunch of animal studies for vision, looking for information on what hogs can see. Results seem varied depending on how the study was conducted (everything from behavior tests to dissections to electrical signals of ocular receptors).

Hogs have about 330 degrees of vision with a narrow region of binocular overlap in front (~50 degrees). Eye structure tests indicate that they see yellow, green blue much more so than seeing the color of red. So they are not color blind as is often claimed, but have a more limited color spectrum of vision than humans. That is NOT to say that they cannot see red. Red is not invisible to hogs, but not visible as red. Hogs can and do often respond to the use of red lights when hunting. My guess is that they see is as a gray light, like you would see a red light illuminated in a B&W movie.

Hogs do not have comparable focal capabilities to humans. They aren't likely to be texting and reading emails, but as noted above, their signals for danger will undoubtedly be inspired by movement. Remember, vision is not solely based in the capabilities of the eyes, but in the brain's ability to interpret the information from the eyes

In various places, I have seen where folks have noted that hogs don't see well at night because of their lack of a tapetum lucidum (the reflective tissue noted for eyeshine in animals such as coyotes and raccoons). Pigs have generally poor eyeshine, but they do have it. Do they see poorly at night? That would depend on what "poorly" means. They probably see worse than deer or coyotes, but they apparently see a helluva lot better than humans. I have watched a sounder of running hogs through night vision that managed to miss numerous obstacles at full run.

So hogs can make good use of their vision when they need to do so, but may not respond to a lot of stimuli simply because they don't have a known need to respond to the stimuli. Some hogs are not fearful of humans. After deer season, the deer on my land let me approach to within 15 yards of them in broad daylight as I carried a bag of corn to refill a feeder by which they were standing. They saw me get out of the truck, LOL.

http://www.artschool.utas.edu.au/PigVision/specvis.html
http://www.fao.org/fileadmin/user_up...download.pdf33
http://www.google.com/url?sa=t&rct=j...-1EOmj-2_eE96A

Sometimes, despite best efforts, vision, vision interpretation, and decision making fails every species. This little guy didn't quite make the corner.
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-- said to me by my 11 year old daughter before going out for hogs 8/13/2011
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