The Javelin or Dwarf Rocket Frog (Litoria microbelos) is a tiny hylid frog from the northern part of Queensland, the Northern Territory and the northeastern corner of Western Australia. In this area it is a frog of woodlands and swampy areas. I recorded these frogs in flooded pastures and roadside ditches in areas of open grassland surrounded by woodlands.
The individuals I encountered were all calling from deep within clumps of grass right above the water line. They were quite difficult to find due to their diminutive size (~16 mm / 0.6 inches) and the fact that they were calling from deep within grass. This behavior combined with their small size and the nature of their call reminded me of some of the smaller North American Chorus Frogs such as the Little Grass Frog (Pseudacris ocularis).
Of course, the goal of all this calling is to attract a mate and this individual below seems to have been succesful as he is in amplexus with a female. Note that the female is larger than the male, a trait common in many frogs and toads.
The call of the Javelin Frog is a high pitched, dry upward trill. The trill is about 1/3 of a second long and they call constantly at a rate of approximately twice a second. Of course, I suspect that call rates for this species, like most frogs, are temperature dependent.
It is very insect like when first heard.
Here is a recording of two Javelin Frog calling together. You can hear how the two frogs alternate both the timing and the pitch of their calls to make sure they are not competing directly with each other. This is very common in frogs.
Looking at a section of the spectrograph for those two Javelin Frogs you can see the upward slur to the trill and the pitch of this call, centered approximately around 7khz. This is quite high pitched for a frog call, but not unexpected for a frog this small. The Javelin Frog call is highlighted in the spectrograph. The other similar pattern at around 3khz is also part of the javelin frogs call. The other markings below that are the calls of another species (Litoria nasuta) from that recording.
© Chris Harrison 2015