Cancers Threaten Wild Animal Populations

Sad Green Turtle photo

Image: Green Turtle Face, by Sharon Deem, courtesy of WCS
Sad Green Turtle
If this Green Turtle appears sad, perhaps it is pondering the newest threat to its endangered species. Green turtles belong to the groups of marine denizens known to suffer from high levels of cancer in the wild. Cancer kills about one in every ten humans; now a new study done under the auspices of the Wildlife Conservation Society reveals that some wild animal species are dying at similar rates. Tazmanian devils, turtles, whales, sea lions, dolphins and fish are some of the species shown in the study to be suffering from elevated rates of cancer, in some cases threatening the very survival of the species.
Fibropapillomatosis tumor which commonly inflicts green turtles photo

Image: Turtle Fibropapillomatosis Tumor, Cynthia Lagueux, courtesy of WCS
Fibropapillomatosis Tumor Infects Green Turtles
Cancer prevalence in green turtles, an endangered species, have increased 92% since the early 1980's, reaching epidemic proportions in some areas along the coasts of Florida, Hawaii and Caribbean islands. The authors have hypothesized that cancer must join habitat destruction, over-hunting of the turtles and their eggs and fishing accidents as a cause of population decline in the threatened green turtle species.

Cancers Prevent Animals from Mating and Reproducing
In some cases, cancers could threaten populations by preventing reproduction in addition to killing individuals. Sea lions found off of California suffer widespread metastasizing genital carcinomas which prevent them from mating. Rarely seen before the 1980's, such cancers were found in over 18% of sea lions washed up on California beaches. In a separate study of sea lions killed during an unusual algal bloom, 6.3% were found to have cancer. Fortunately, sea lion populations have been growing in spite of the simultaneous increase in observed cancers. Ocean-going dolphins are also showing increased rates of genital cancers.

Pollution Causing Animal Cancers
Cancer is the second leading cause of death in Beluga whales living in the Saint Lawrence River estuary, collector of smelting effluents and known to have elevated levels of cancer causing polycyclic aromatic hydrocarbons (PAHs). Higher rates of cancer in bottom feeding fish point to the potential dangers of carcinogens lurking in the sediments at the bottom of lakes and waterways.

Growing Interest and Concern About Animal Cancers
Be sure to check out THTV, showing a video with Fabien Cousteau where he talks about the threat of cancer to wildlife. Cousteau's most recent film has a scene with an autopsy on a St. Lawrence River Beluga whale cancer tumor.

The study Wildlife Cancer: A Conservation Perspective, by Denise McAloose and Alisa L. Newton, appears in the July edition of Nature Reviews Cancer. The authors work at the Pathology and Disease Investigation in the Global Health Program at the Wildlife Conservation Society.

More on Cancers and Wildlife:
Wildlife Conservation Society
Cute Tasmanian Devil on Sick Leave
The Extinction Sucks Series and Other Films
Zoos Warn Mad Max Landscapes are a Probability
Why Are Most Homes Filled With Cancer Causing Substances?

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