Animal feed to change crocodile gender?

That's a problem scientists have discovered and published in the journal Science.

"If you want to know a crocodile is a male or female, you have to catch it, but it's very slippery," said Chris Murray, who spent three dry seasons in Palo Verde National Park in Costa Rica studying alligators ( Crocodylus acutus), say.

Do food for tilapia?

After analysis, Murray and his colleagues found that there was a large gender difference in baby crocodiles , 4 males had 1 female.

Furthermore, they found a piece of their tissue attached to a steroid of artificial origin, and scientists suspect this is the cause of sex change in crocodiles.

The sex ratio of crocodiles in Palo Verde National Park is currently 4 - 1 - (Photo: ROBERT BLANKEN).

It is the hormone 17α-methyltestosterone (MT), sometimes indicated for men with testosterone deficiency or older women with breast cancer.

But why is it found in crocodiles in rural Costa Rica?

Looking for the answer, Murray and his colleagues found that there were many households raising tilapia with food containing this hormone. They are currently investigating whether the MT hormone from these farms has affected crocodiles.

"This result can impact a large ecoregion , " said Matthew Milines of Mars Hill University in North Carolina.

In addition to the incidence of gender bias, MT can break the reproduction process of crocodiles because they are listed as vulnerable animals in the region.

It can also make crocodiles become more aggressive, leading to a "war" between humans and crocodiles that are already much more abundant.

As a result, this species can harm other species such as turtles, birds, fish, and many other aquatic organisms. And because tropical fish farms all feed tilapia on foods that are rich in MT, the same problem can occur elsewhere.

More than climate change

Climate change has the opposite effect on gender, which increases the number of children.

Unlike humans, alligators have no sex chromosomes. The fetus becomes male or female depending on the temperature of the nest during incubation.

The temperature in Palo Verde has increased by about 2.5 degrees Celsius in less than 20 years. To calculate the effect of this temperature increase, Murray and colleagues studied the eggs buried in 25 drives.

The team estimates that, based on the temperature in the nest, the number of females must be higher than males at a ratio of 2-1. Obviously something has impacted more on temperature. Is it an MT hormone?

In the future, the research team wants to determine whether MT also affects crocodiles in other areas.