Scientists put 'G-strings' on tiny frogs to track their movement

The frog ‘pants’ are made up of tiny hand-made silicon waist bands and a tracking device.
Sejal Sharma
Tiny frogs fitted with tracking devices
Tiny frogs fitted with tracking devices


Why would scientists put pants on a frog?

Biologist Andrius Pašukonis says it’s a good way to track where they’re headed.

“Miniature tracking tags have been used on amphibians and other animals before but tracking tiny mobile frogs in the rainforest required reimagining the tag design and the tracking methods,” said Pašukonis in a press release. “One of the biggest challenges has been designing and perfecting a frog harness that can fit a frog as small as two centimeters (less than an inch)!”

Pašukonis and his team of researchers studied three poison frog species: Allobates femoralis, Dendrobates tinctorius, and Oophaga sylvatica.

They wanted to find out how these male and female frogs navigate. The study was based on sex differences in spatial behavior across three poison frog species with contrasting parental sex roles and reproductive strategies. 

These brightly colored frogs are found in South America and are some of the most dangerous frogs to touch. Their skin secretes toxins that can kill or paralyze people or animals.

Research in Ecuador and French Guiana

The frog ‘pants’ are made up of tiny hand-made silicon waist bands and a tracking device. The device would send signals from the antennae, so that the researchers could locate them.

"My French colleagues like to call it a telemetric G-string," said Pašukonis, as per a report by CBC. "It's a lot of fine motor skills and a lot of practice in handling tiny frogs and sewing little frog harnesses. But we go find them in the rainforest, and we catch them, and we put the tags on."

The researchers gave the frogs a ‘spa’ to assess androgen levels. The spa was a glass container partially filled with water.

“The frogs sit in the bath for a half hour before and after translocation,” explained Stanford biologist Lauren O’Connell. The frogs release hormones into the water and then, “we extract hormones from the bath water back at the lab.”

The team removed the trackers after four to six days

The results of the tracking showed that male poison frogs are generally more explorative and have androgen levels which is consistent with the androgen-spillover hypothesis. The hypothesis being that males, in previous studies conducted on rodents, tend to navigate better than females.

A similar design was adopted by Richard Essner, a biologist at Southern Illinois University Edwardsville, a decade ago. Essner was not a part of the Stanford study, as per the CBC report.

He attempted to use a similar tracking divide to track the movement of the threatened Illinois chorus frog. "Unfortunately, we had to abandon the study because we found that the transmitter apparatus was interfering with locomotion. If the belt was too tight, it caused abrasion. If it was too loose it slid down around the legs and left the frog immobilized and vulnerable to predation," he said.

Study abstract:

Sex differences in vertebrate spatial abilities are typically interpreted under the adaptive specialization hypothesis, which posits that male reproductive success is linked to larger home ranges and better navigational skills. The androgen spillover hypothesis counters that enhanced male spatial performance may be a byproduct of higher androgen levels. Animal groups that include species where females are expected to outperform males based on life-history traits are key for disentangling these hypotheses. We investigated the association between sex differences in reproductive strategies, spatial behavior, and androgen levels in three species of poison frogs. We tracked individuals in natural environments to show that contrasting parental sex roles shape sex differences in space use, where the sex performing parental duties shows wider-ranging movements. We then translocated frogs from their home areas to test their navigational performance and found that the caring sex outperformed the non-caring sex only in one out of three species. In addition, males across species displayed more explorative behavior than females and androgen levels correlated with explorative behavior and homing accuracy. Overall, we reveal that poison frog reproductive strategies shape movement patterns but not necessarily navigational performance. Together this work suggests that prevailing adaptive hypotheses provide an incomplete explanation of sex differences in spatial abilities.

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