Koolies are known for being vigorously healthy dogs. They can, however, due to the merle factor, throw pups from time to time with hearing and/ or sight problems (see more info below). They are tough, strong and possess excellent stamina and endurance. Koolies are thinking dogs who possess impeccable work ethics, unsurpassed biddability and superior temperaments.
Most identify and recognize the Koolie breed by their merle colour.
A Koolie can either be a solid colour (with or without white and/or tan markings) or a merle pattern colouration. The only difference between the solid colour and merle coloured dogs, in relation to workers and health, are their colours.
Experienced, long standing, breeders are informed, use care, and are selective in their breeding merle to merle colours. It is not an irresponsible practice as long as it is done knowledgeably and with due care. Many long time experienced breeders have been breeding merle to merle for many generations without adverse effects because they are careful in their choices of breeding lines. Most only use dogs with a minimum of white colouration, especially on the head, in their breeding practices.
The practice of merle to merle breeding, sometimes, can be tragic as it may produce offspring that will have full and/or partial vision and/or hearing disability. This disability is due to the "double merle factor" that sometimes will produce offspring that are solid white or with a white head. Although this is not a frequent occurrence, responsible breeders are informed of these possible health issues and monitor their pups carefully. Merle to merle breeding, and the possible effects to the offspring, need to be taken into consideration when planning to breed.
For more information on colour genetics we suggest a peek at this site:
If in doubt, it is recommended to breed a solid coloured dog to a merle colour in order to help avoid these problems from occurring. The solid coloured dogs are no less a Koolie than the merles are, and their working ability is in no way impaired. Some people prefer solids, others merle. It is all a matter of personal preference.
The merle coloured Koolies often have blue, green, flecked eyes or different coloured eyes. Blue and green flecked colored eyes are common in both the merle and solid coloured dogs.
There are both medium and short coated Koolies, this is again a matter of personal preference and regional types.