By the end of Mortlock’s ownership of Coffin Bay Run in 1927, the run had become erratic and progress had taken its toll on the financial success of the breeding horses. The horses had become simply unmanageable and wild to a large degree. New owner Martin Cash found the horses at Coffin Bay Run to be so uncontrollable and overpopulated that he authorized culling and mass destruction to reduce the population to a more controllable number.
In 1932, yet another owner, the Morgan family, purchased Coffin Bay Run. During the Depression and Second World War, the pony was once again in high demand for workers in the area, as petrol became unaffordable and unobtainable. The ponies then became invaluable as the unusable machinery sat rusting in paddocks.
After peace was declared in 1945, the demand for ponies declined as machinery became usable once again. Moss Morgan made a modest living, which was partly assisted by the catching and breaking of wild ponies for sale to locals as riding ponies. Many locals in Coffin Bay can still recall the ponies as buck jumpers at the local rodeos.
In 1972, Geoff Morgan ceded the Coffin Bay Run to the Southern Australia government to be used as a national park. This was the end of the pastoral history in Coffin Bay. Eight years later, the ponies of Coffin Bay faced removal from their long-time home under the Parks and Wildlife ‘pest control’ program. Concerned locals banded together to form the Coffin Bay Pony Society, a volunteer group dedicated to helping the ponies in the park. Negotiations began for a management and control program which would allow a compromise, whereby the ponies would be allowed to stay in their home of over 100 years but in a controlled and managed park setting.