a few years back a 120 pound rotty was taken by coyates in milton, they got into a 6ft fenced in area, where there is a will there is a way. Remember there isnt usally just one.
Male dogs are easier prey for them, they will actually send a female in heat to attract the male dog away form his surroundings and then ambush them.
It is rare but yes you shoudl be aware of the threat.
Cheers!