Mothers needing to relocate tadpoles to safer locations after hatching comes with a series of risks. Therefore, transport only makes sense when the risk that is taken serves the survival of one's offspring. A recent study from the University of Veterinary Medicine in Vienna revealed that female brilliant-thighed poison frogs rely on what researchers call an "inner GPS" to recognize and provide preferential care to their own offspring.
The brilliant-thighed poison frog (Allobates femoralis) is a ground-dwelling species living in tropical forests of South America. Females lay their eggs on fallen leaves, while males stand guard.
However, after three weeks of development, tadpoles must be transported to the nearest body of water - but only at the right time, otherwise their chances of survival are compromised. Generally, males are the one's responsible for transport, but if they are around when the time window for relocation presents itself, females will take over.
As innate body guards, males run the risk of loosing their territory to rivals when leaving it unguarded to transport their tadpoles.
"Transport therefore only makes sense when the risk that is taken serves the survival of one's offspring," explained Eva Ringler, one of the study researchers from the Department of Comparative Cognitive Research at the Messerli Research Institute of Vetmeduni Vienna.
However, this implies that the frogs are able to distinguish their own offspring from a number of unrelated clutches.
"Especially interesting was whether there is a difference between male and female behavior," Ringler added.
Researchers designed a series of experiments to test how the frogs discriminate their offspring from others. In the first trial, for instance, male and female frogs were presented only with an unrelated clutch. In the second trial, the frogs were presented with both an unrelated and related clutch. Then, in the third trial, researchers exchanged the positions of the frog's own clutch and a foreign clutch to test whether they recognized the clutch itself or just remembered the location of them.
The trials revealed that, for the most part, males let all tadpoles in the area wiggle onto their back in a parental strategy researchers call "my territory, my tadpoles." This suggests males forego the challenge of discriminating their offspring completely.
On the other hand, females do not transport unrelated tadpoles when they knew the position of their own clutch. However, when researchers switched the position of their clutch with another, they only transported the unrelated clutch. This suggests that, even weeks later, females remember the exact position where they laid their eggs and that, when they are in charge of transportation, they choose the correct clutch based on its location.
While the end goal may be to provide care only to one's own clutch, females actually have a much higher risk of transporting a foreign clutch and neglecting their own entirely. Males, owing to their territorial behavior, assume that all clutches in their territory are theirs and therefore have a lower risk of neglecting their own offspring.
"Further research is needed to clarify just how the females remember the exact location of oviposition in the dense rain forest," Ringler concluded.
Their findings were recently published in the journal Animal Behaviour.
