September
20, 2017, Phys. org
Poison
frogs, especially male poison frogs, are very caring parents. After the
tadpoles hatch, the males piggyback their offspring to distant pools spread
around the rainforest where they can feed and develop. In a recent study, a
team of researchers from Vetmeduni Vienna, the University of Vienna and Harvard
University show that this parental behaviour can be triggered experimentally.
When unrelated tadpoles are placed on the backs of adult frogs, male – and even
female – "foster parents" make their way to pools in the forest in
the same way as if they had picked up the tadpoles themselves. The experiment
showed for the first time that an external stimulus can trigger complex
behaviours such as parental care in amphibians. The study was published in the
Journal of Experimental Biology.
Parental
care is widespread in the animal kingdom. Poison frogs are also known to be
dedicated parents. They pick up their tadpoles after they hatch and piggyback
them to distant pools spread around the forest. Until now, the processes that
trigger parental
care
have been mostly studied in birds and mammals. But the exact stimulus that
triggers frogs to carry their offspring to the pools remains unstudied.
Researchers
from Vetmeduni Vienna, the University of Vienna and Harvard University have now
investigated whether adult frogs will only transport tadpoles if they pick up a
clutch themselves or if this behaviour could be triggered experimentally. The
team of researchers placed unrelated tadpoles on the backs of different frogs.
The study showed that the amphibians are exemplary foster parents and that even
females, which under natural conditions only rarely perform the role of
"transporter", assumed their parental duties just like males when
tadpoles were placed on their backs.
After the
foster tadpoles were placed on the backs of male and female frogs, the adults
were fitted with miniature transponders for tracking. "We wanted to know
if foster tadpoles were also transported to the pools. The results show that
the tadpoles do not have to be picked up, but that contact with the backs of
the adult frogs was enough to trigger the transport," explains Andrius
Pašukonis of the University of Vienna, who led the study together with Kristina
Beck and Eva Ringler.
"We
observed that all tested frogs, both males and females, transported the
experimentally placed tadpoles to pools," says Eva Ringler of the
Vetmeduni Vienna's Messerli Research Institute. Their behaviour was the same as
if they had decided to pick up and transport the tadpoles themselves. This
shows that the parental care instinct in these frogs can be triggered by
placing tadpoles on the backs of the adult animals whether they are related or
not. However, the experiment could not yet clearly identify the mechanism that
triggers this instinctive behaviour.
"We
suspect that tactile stimuli, certain touching or movement patterns by the
tadpoles, play a role. These findings are interesting, as they show how one
stimulus can trigger such complex behaviour. The adult poison frogs don't
just march off; the touching also stimulates memories of distant pool locations
in the forest," says Pašukonis.
Also
interesting was that the female
frogs voluntarily carried the foster tadpoles to the pools.
"In this species, females naturally transport tadpoles only in rare
cases," explains Ringler. The instinctively triggered behaviour therefore
does not appear to be sex-specific. Among both males and females, the physical
presence to the tadpoles placed on their backs was sufficient to make the frogs
transport the tadpoles to the pools and so to ensure the survival of
unrelated young. The study was the first to show in the wild and among
amphibians that such complex behaviour can be
triggered by one external stimulus.
More
information: Andrius Pašukonis et al. Induced parental care in a poison frog: a
tadpole cross-fostering experiment, The Journal of Experimental Biology (2017).
DOI: 10.1242/jeb.165126
Journal
reference: Journal
of Experimental Biology
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