The largest hawks in the US are the Ferruginous (western states only) and the Redtailed . The females are larger, as in all birds of prey, reaching weights of 4 to 4 1/2 lbs, a body length just under 2 ft and a wing span of 5 feet. They prey on, and lift and carry away, mostly small rodents, large gophers weigh about a half pond. They occaisionally kill prairie dogs (4 lb max) and rabbits ( jack rabbit up to 8 lb) they usually do not carry such large prey away, but eat what they can where it lies, often coming back later for more. A small dog or cat is probably pretty safe even from being attacked. The hawk is just not likely to make a kill where it would have to eat so close to human habitation, but it is possible. It would be even more unusual for a hawk to actually carry one away. Late breaking news, requiring an edit; A few hours after answering I visited the local used book store where to my delight I found three years worth of Birder's magazine in the 'discard free for the taking' box!! Even bigger surprize, in June 2006 issue someone asked almost the same question! Except 'Have hawks been known to pick up small dogs?' Instead of 'can they.' The expert's answer was almost the same as mine, he adds Harris's and Swainson's hawks as likely suspects and his jack rabbits weigh almost 10 pounds (thas a BIG rabbit.) The important difference is he warns that night time is more dangerous, Great Horned Owls have been known to take cats, in England a Eurasian Eagle Owl made headlines when it attacked and injured at least 5 small dogs before it was captured. ( The following is me talking) Eagle owls are huge , they don't live in the US. The great Horned lives all over the US, even in suburbs, it and/or the Snowy Owl is the largest owl in the US. Great Horned is lil over 2 ft long, weighs over 3 lb wing span of over 6 ft! Snowy Owl breeds along the Artic coast but winters as far south as Texas, but is more of a rural dweller, it has a slightly shorter wingspan but slightly out weighs the Gret Horned. Since they hunt mostly at night they are not as leery of making kills near human habitation. The Snowy also hunts during the day, and on wintering grounds shows little fear of humans,a bird watcher's favorite, it will sit calmly in the open unless approached to within a few feet, some have been known to catch prey within 10-15 feet of people. You're not likely to have Snowys near your home,( unless you to spend winters in rural areas, but the Great Horned could snatch your pet out of the yard.

I have studied Hawks all my life and have a Docotrate in Animal Physiology. One study being conducted at the University, that I teach at, is cat coat color and which is most desireable by these impressive creatures. Best wishes. Dr. Hawk