Frogs in our Forests
Wendy is the local frog expert who has been operating her frog tours for many years here in Pemberton. Her tours are bookable from the Pemberton Visitors Centre on 9776 1133 or email pemtour@karriweb.com.au.
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The Pemberton area is home to 10 species of frogs, several are Gondwanan species. The surrounding areas to the north and south also provide habitat for another 5 species.
Pemberton’s rainfall currently averages approximately 1100 mm a year. Generally February is the only month where no or very little rainfall is experienced and frogs can be found year-round.
Most rain occurs in the months from April through to October when temperatures can be quite low and despite being cold-blooded many of the frog species have evolved adaptations to the cold weather.
The burrowing frogs in the south west, Helioporus species, build breeding burrows in winter-wet areas. During autumn rains, the burrows fill with water. The Helioporus frogs will breed in the burrows and the tadpoles will live in the burrows initially until the swamps fill with water.
Sand Frogs (Helioporus psammophilus) will breed quite early with the first autumn rains, usually in March, followed by Moaning Frogs (Helioporus eyrei) a few weeks later. Sand Frogs have a rapid ‘put-put-put’ call, similar to a generator running in the distance, Moaning Frogs have a drawn-out repeated ‘hooooooottt’.
Lea’s Frogs (Geocrinia leai) will start to breed when the heavy autumn rains set in – their call is a simple ‘tik tik tik’. Lea’s Frogs don’t lay their eggs in water, they lay them in vegetation surrounding water or under bark/leaf litter in moist areas. The tadpoles can take up to 120 days to undergo metamorphosis so Lea’s Frogs will breed at the beginning of the wet season, when the tadpoles hatch from the eggs they either fall into water from the vegetation or live amongst the degraded egg jelly mass.
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By the end of autumn the first of the Crinia species will usually start breeding. Bleating Frogs (Crinia pseudinsignifera) breed in shallow waters along the edges of waterways and have a call similar to a softly bleating lamb.
The dams, rivers and streams filling with winter rains will trigger the Glauert’s Froglet (Crinia glauerti) to breed, once the groundwater table has recharged the continual rain will then form shallow puddles, gently-running seepages and drains which the Quacking Frogs (Crinia georgiana) will use to breed.
Both Bleating Frogs and Glauert’s Froglets have a maximum size of around 2 cm. Glauert’s Froglets have a call like a clicking rattle, sometimes described as “a dried pea rattling in a can”.
Quacking Frogs sound just like a duck quacking and will only breed in very shallow waters. They have a bright red colouration in their thighs and when they are calling from the water they resemble a dead marri leaf floating in the water.
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By early spring we will start to hear Slender Tree Frogs (Litoria adelaidensis) calling, generally when our night-time temperatures consistently rise above 12 degrees Celsius. Their call is a loud ‘squark‘ and they can be found around almost any waterways, usually calling from vegetation above the water level.
Banjo Frogs, or Pobblebonks (Limnodynastes dorsalis) also breed in spring and they will be heard around any large waterbodies (a ‘bonk’ call).
Karri or Roseate Frogs (Geocrinia rosea) can be heard from September to November, calling from under vegetation in moist karri forest areas. Their call is a rapidly-repeated click, similar to castanets. Karri Frogs lay their eggs in a shallow scrape in the soil under the vegetation and the tadpoles undergo metamorphosis in the degraded egg jelly mass.
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When our nights warm up consistently Motorbike Frogs (Litoria moorei) will head towards the nearest water to breed. The males call from the water to attract females. Motorbike Frogs are one of our most abundant frogs and because of their large size are relatively easy to find at night from late October through to March. Their call is a quiet motorbike-like sound.
Over summer the only frog we will generally hear calling is the Nicholls Toadlet (Metacrinia nichollsi). These small frogs live underneath fallen logs in the forest where they lay their eggs. The tadpoles develop within the eggs and emerge as small frogs on hatching. They can be heard over summer during light rains, a grating, squelching ‘criiiiick’.
By Wendy Eiby
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Apps that you may be interested in: Frog Log
