Female of the Species Really Is More Deadly—If You’re a Toxic Newt

Scientists have found that female toxic newts are far more deadly and poisonous than males.

Taricha newts are a highly toxic species found in the Pacific coastal region. They possess a powerful neurotoxin called Tetrodotoxin that seeps from their skin. The toxin, which is the same one possessed by the deadly blue-ringed octopus, can be fatal to humans if ingested. Scientists however, are not sure why the species possesses the toxin or how it is produced, so they are undertaking more research.

A new study published in the journal Frontiers in Amphibian and Reptile Science found that females are more poisonous than males.

“It had long been considered that newts’ toxin concentrations do not change in their lifetime and that males and females tend to have the same toxin concentrations. Now, we have shown that female newts actually contain more toxin than male newts,” Gary Bucciarelli of the University of California Davis, corresponding author of the study, said in a release. “We observed significantly greater and more drastically fluctuating toxin concentrations in females, which may have numerous causes, like mate selection.”

Scientists analyzed 850 newts found in 38 sites in California. They assessed the newts’ skin to gauge toxin levels, and then compared them between males and females.

The newts are sexually dimorphic in other ways. It was already known that their tail height and size differed between sexes, but until now, toxin levels were not distinguished between them.

The findings suggest that females are far more dangerous than males, the study reported.

“For would-be predators, these higher concentrations pose a serious threat,” Bucciarelli said. “Taricha newts should not be handled unless by knowledgeable personnel, because they can contain up 54 milligrams of tetrodotoxin per individual. Doses up to 42 micrograms per kilo of body weight can lead to hospitalization or death.”

Scientists also weighed the toxin levels with other sexually dimorphic aspects of the newts. They found that heavier newts had a larger amount of toxin than newts that weighed less.

However, the median concentration of the toxin was always consistently higher in females.

Not only does this show that females are more dangerous than males, but it also suggests that the toxin production could be different between the sexes. Scientists theorize that each sex needs different resources to produce and carry the poison.

While it is uncertain why females carry more, it could be for protection in females that are vulnerable when carrying offspring, the study reported.

“Taricha newts’ breeding patterns are highly dependent on precipitation patterns,” Bucciarelli said in the release. “Given the drought conditions of California, we did not always have a balanced design when field sampling. However, we feel the pattern is still very strong. Our next plan is to explore how drought and fire affect newts and their toxin concentrations and how each sex responds to these natural disasters.”