Black Dog Syndrome

Why does it appear that black dogs, particularly the large ones, and black cats are unadoptable? The phenomenon has been dubbed "black dog syndrome." Is it superstition? Black cats are considered unlucky by some. Is it mythology? Big black dogs have been portrayed as symbols of death in literature and legend, cast as bad guys in movies like The Omen, and even featured in modern stories like the dog Grim in the Harry Potter tales.
Some of the reasons may be more pragmatic. Black dogs have to be specially lighted for photography and therefore don't show up well on shelter websites, and in pamphlets and flyers. Visitors have trouble noticing them too in poorly lit kennels. "In a lot of shelter environments the lighting is not that great to begin with," says Pam Black Townsend, a shelter volunteer at the SPCA/Humane Society of Prince George's County in Maryland, whose photo book of black dogs raises money for the shelter www.pgspca.org. "They are hard to photograph and some people say, with black dogs, their eyes don't stand out as much and so they are harder to read. That makes people a little bit cautious."
There is also a theory that there are just more black dogs then those of other shades, being the black gene is most dominant.

Some experts dispute the severity of "black dog syndrome." Kimberley Intino, director of animal sheltering issues for the Humane Society of the United States, cites one study by Pethealth Inc., a pet insurance and animal microchip company, that went through numbers from 679 shelters and found black dogs indeed had longer stays before being adopted — but just by two days on average. "The idea that black dogs are not being adopted is not as gloomy as it is being portrayed," Intino says. But the anecdotal evidence seems hard to dispute.