Examples of using 条 : 两条腿 liǎngtiáo tuǐ Two legs. 一条烟 yìtiáo yān a multipack of cigarettes. Examples using 只: 这只猫非常强壮，荤似一只小老虎 Zhèzhī māo fēicháng qiángzhuàng，hūnsì yìzhī xiǎolǎohǔ。 This cat is very strong, exactly like a little tiger. 一眼望去江天上只有几只海鸟 Yìyǎn wàngqù jiāngtiānshàng zhǐyǒu jǐ zhī hǎiniǎo A few seabirds fly in the vast sky over the river. Apparently 只 is more often used as a measure words for animals and birds, while 条 is used only for those animals having the shape of a long thin object and could be then interchanged with 只

只 is a classifier for birds and certain animals ( so you have to memorize them), one of a pair, some utensils, vessels etc 条 is a classifier for long thin things (ribbon, river, road, trousers etc) and some animals that take the same shape,therefore that dog must have had this kind of long think body shape .

条 is normally for describing something that has the form of long strip. for example. 一条裤子》one pair of trousers. 一条狗》it implies that the dog is long. 只 is normally for the little pets or for small animals.

when the animal is more "square or like a ball", "只“is better than"条”。e.g：一只大象，一只老虎，一只猫，一只乌龟,一只小鸟； when the animal is more "long and agile", "条“is better than ”只“， e.g: 一条鱼，一条蛇，一条毛毛虫，一条大虫（chinese in Song dynasty，= 一只老虎，but more focus on it's long body and agile movement)。

As a native speaker, i dont see difference between “一只狗”and "一条狗". But I'm sure I've never heard "一条猫", never.