Panthers of the Everglades National Park

What was causing the drastic decline of the panther population in the Everglades? The panthers were on the critically endangered list, was loss of habitat responsible or could it have been inbreeding?
Evidence of a possible cause became evident when in 1989 the body of an apparently healthy female panther was discovered in Everglades National Park. This find prompted further investigations by wildlife agencies on the remaining panthers in the area.

 

The panthers showed a number of disturbing abnormalities

The wildlife specialists concluded that the dead female panther died of mercury poisoning which like other toxic chemicals also tended to accumulate further up the food chain.
But further study showed a number of other problems that couldn’t easily be explained away through mercury poisoning. A disproportionate number of panthers were found to be sterile, some of the male panthers had serious sperm abnormalities and most of the panthers showed evidence of impaired immune response. Thirteen of the seventeen males studied had undescended testicles.

 

Deeper investigations uncovered evidence of endocrine disruptors

The reproductive abnormalities pointed to a number of possible causes. It seemed very likely that the panthers had suffered some kind of hormone disruption early in their development. A study of their hormone levels discovered that a few male panthers had far more estradiol (a form of oestrogen) in their blood than testosterone which was highly unusual. In some there were equal amounts of both hormones in their systems.
It was then no surprise when further analysis of the fat deposits of the dead female panther showed not only lethal levels of mercury but contained 57.6 parts per million of DDE (a breakdown product of DDT) as well as 27 parts per million of PCBs.

DDE as well as been a weak oestrogen mimic, acts also as a potent blocker of male hormones. It can block testosterone messages getting through to the developing fetus in the womb. Any male panthers that she gave birth to would have exhibited a number of reproductive disorders due to the possible hormone imbalance they would have experienced during fetal development.

 

What can we learn about the Everglade Panthers?

Unfortunately, the situation regarding the panthers is not an isolated one. In fact Florida has a number of well publicized wildlife issues that are related to chemical pollution. There was the case concerning the alligators of the Florida swamps and another concerning the turtles of the same locality.
The fact is that there are many animals and many habitats all over the world that have been damaged by one environmental pollutant or another.
What we can learn about the panther situation is that a lot of hard work is required to uncover the roots causes behind the more serious problems affecting some forms of wildlife. Most of the problems are not easy to isolate and identify and most environmental issues are very complicated.
The discovery that mercury killed the panthers only scratched the surface of the problem. There were deeper underlying issues that were not so apparent. Issues that might have slipped under the radar if not for the persistent and diligent work of a few wildlife specialists.