In polluted environments, dolphins gradually accumulated toxins in their body fat, and the larger the dolphin the more accumulated toxin it can tolerate. Nearly 80 percent of the toxins a female dolphin has accumulated pass into the fat-rich milk her nursing calf ingests. Ttherefore, the unusually high mortality rate among dolphin calves in the industrially contaminated waters along Florida' s Gulf Coast is probably the result of their being poisoned by their mother' s milk.
The statement 'The survival rate of firstborn dolphin calves in the area along Florida's Gulf Coast is highest for those whose mothers were killed before they were weaned' most strengthens the argument.