A Natural History of the Costa Rican Gladiator Tree Frog: Hypsiboas rosenbergi

In the summer of 2013 I got the chance to travel with some friends to what is arguable the most biodiverse country in the world, Costa Rica.  Much of that diversity is seen in amphibians because the humid and rainy climate of tropical rainforests is ideal for their lifestyle (with cutaneous respiration and many biphasic dependent species).  Frog diversity was no exception, and we saw numerous species such as poison dart frogs, red-eyed tree frogs and my favorite, the gladiator tree frog, Hypsiboas rosenbergi.   Gladiator tree frogs are usually easy to distinguish, as they are very large in size with no warts or bumps, and most notably, they have a line that beings as the tip of their nose and runs down to the middle of their back.  Also, as members of the Hylidae family, this species has very large as sticky toe pads, as my friend David found out first hand.

This big, adult individual (around 8-9cm long (STV)) was likely female, because males only leave the forest canopy during mating season.  We found the individual near our sleeping huts located adjacent to the rain forest.  If it were a male we would have likely seen it calling, and it would have been near a newly built nest in an attempt to attract a mate.   Females have been known to be very selective, passing up around half of the nests they inspect.  Males draw females in with advertisement calls then as females approach they use somewhat lower intensity mating calls.   This species of the family Hylidae has a biphasic lifestyle, and shows extreme parental care.  Their common name is derived from their parental care strategies as the males actively defend breeding pools before and after the tadpoles hatch.  Males have multiple aggressive calls and reportedly get into physical altercations where many males loose eyes, break eardrums, and some die.   It has been reported that most males who successfully breed leave mating season with fairly permanent damage.