The southern herd had no fresh water for nearly two weeks according to a story by Shore Daily News.
High tides from Hurricane Erin and lack of rain are thought to be responsible for the contamination.
The northern herd was not affected.
The ponies are unique as stated in the article, not because of adaption to island life, but because of the highly abnormal sex ratio and unprecedented birth rate.
In August, after the pony swim but before the hurricane, the herd consisted of 23 males and 126 females.
The population limit is 150.
The saltwater cowboys have turned the wildlife refuge into a puppy mill for wild horses, raking in over $1 million from this year’s auction.
Western Horse Watchers Association 