Why strays that hang around garbage dumps don't have skin problems?

Why strays that hang around garbage dumps don't have skin problems? Spend the next few weeks observing any stray dogs hanging around garbage dumps...why no skin problem. Also observe especially the wild dogs on Discovery Channel 12, or even on Channel 10 and 11...."man" all these wild dogs can be covered in mud...where got "bathe"...any skin problems? Remember seeing all those Australian dingos documentaries...wah lau their coat so beautiful and shiny....the Australian outback can be very dry and especially harsh for live animals...I remember watching in amusement how these dingos survived by catching rats...rats good to eat meh?...better then your dog food?********************************************* all those dogs described as above only got skin problem if they are injured through eg.....fights and accidents like falling into a rocky ditch...but mind you they can recover real fast..................WHY...why...why...think...th ink...think!!! I will leave this thread open for all all dog owners to put down why you think all those dogs who are supposedly at the lower rung of the animal kingdom can maintain healthy skin while your supposedly beloved, pampered and well taken care pets are always going to the vet for skin problem treatment. Please help keep thread going by contributing your reasons and hopefully we all can understand how to keep our pet heathy and skin problem- free!!!

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German Shepherd Dog is my strength. Ranchu is something I love to learn & appreciate.