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How to tell the difference between the tadpoles of native frogs versus the tadpoles of the Cane Toad, an introduced pest rapidly spreading across Northern Australia
  NATIVE TADPOLE… OR CANE TOAD? by Marion Anstis Western Australia is facing an imminent invasion of the Cane Toad. The Statehas at least 70 species of native frogs which have a variety of egg and tadpole types.Fortunately, the eggs and tadpoles of the Cane Toad are quite easy to recognize incomparison to our native species. The key features to look for are shown here, withcomparisons to some native species from northern WA. The Eggs Cane Toad eggs are laid in long chainsor strands, often strung aroundvegetation Eggs of the Cane Toad are very unlikenative species because they are laid invery long strings or chains, mostcommonly made up of pairs of eggs. Eachblack and white egg is enclosed within aclear jelly capsule that is part of a longstrand of rope-like jelly. While somenative species string their eggs together,they are not mainly in pairs and often atleast part of the egg mass is clumpedtogether - see photos below. When yousee Cane Toad eggs, they are in a verylarge tangled mass of strands of thesepaired eggs as each female toad can layup to 25,000 eggs! She moves around asshe lays, so the eggs can be spread out over quite a wide area, and often severalfemales lay at once in the same pond, so the result is a very conspicuous mass of eggs.Egg masses of native frog species, on the other hand, are often harder to findbecause they don’t lay as many, and because the eggs are laid in different ways. Themost commonly known egg mass isprobably the foamy one of the BanjoFrog (genus Limnodynastes ) and itsclose relatives, which looks very similarto this. The white foam floats at thesurface of the water and is a mixture of air bubbles and clear jelly, rather likebeaten egg-whites. The female froguses her hands as an egg beater towhip up this dome of froth as she laysher tiny black and white eggs. The foamprotects the eggs from sun andpredators as they are hidden within andbeneath the jelly-coated bubbles. Banjo Frog egg mass    Another common type of egg mass, especially in north-western Australia,(where Cane Toads will first arrive), is that of the Rocket Frog ( Litoria nasuta ) and itsclose relatives. These frogs lay their eggs in small floating clumps at the surface, andall the jelly capsules stick together, but there is no white foam. The diameter of aclump like this is usually only from 3 – 10 cm or so across.The clear jelly capsules can beseen around each dark brown and whiteegg. These eggs are usually laid inponds, swamps or flood plain pools.A third type of native egg massyou may see, again often near thesurface (if recently laid), just below thesurface or on the bottom in shallowwater, is that laid by the NorthernSpadefoot Frog (affectionately knownas the Golf-Ball Frog), Notadenmelanoscaphus . A very similar mass islaid by the burrowing frogs of the genus Neobatrachus . These lay a larger clumpof jelly eggs (non-foamy) that adheretogether. Floating egg clump of Rocket frog orother ground-dwelling tree frogs There are about 1,000 or moreeggs in this clump (below left), and it isabout 15 cm across (larger than theclumps of the Rocket Frog group). The rather fluid jelly capsules tend to stick quitestrongly together. Some species of  Cyclorana (for example, the Hidden-ear Frog, C.cryptotis ) which is common in north-eastern WA, lay smaller clumps which may beattached to a fine strand of grass. The individual egg capsules too are smaller, lessfluid and will separate if jostled. Egg mass of Hidden-ear FrogEgg mass of Northern Spadefoot 2  Still other native frogs lay their eggs attached singly or in very small groups alonggrass stems or twigs, for example the members of the genus Uperoleia (smalltoadlets) and the genus Crinia (small froglets). While Uperoleia are called toadletsbecause of their glandular skin, they are not true toads. They spread their individualeggs out over a broad area underwater, and unlike Cane Toad eggs, these are veryhard to find. Common Froglet egg clusterattached to stemA single egg of a froglet ( Crinia  ,left) and 3 of a native toadlet( Uperoleia  ) The Tadpoles  Some of the main differences between native tadpoles and the Cane Toad tadpoleare:- Cane Toad Tadpole Native Species of northern WA Body uniform black Body dark or light to clear brown, or very palewhitish gold to sandy, some may have darkerpatches or mottling. One species is usuallyblack – the Marbled Frog ( Limnodynastesconvexiusculus ), but this tadpole is very muchlarger (to 80+ mm) - see photo below.Tail muscle uniform black, finsclear.Tail muscle pale to dark brown or blotchy. Blackin Marbled Frog. Fins may be very dark ormostly clear, often with pigmented veins. Mayhave spots or blotches and usually have somefine or more prominent gold pigment.Tail only about 1 1/4 to 1 1/2 timeslength of body, tail tip rounded.Tail usually twice the length of body or a littlemore. Tail tip may be rounded, pointed or veryfinely pointed.Tadpole small – grows to maximumtotal length of about 28 mm, bodyonly to about 11 mm.Tadpoles from small to very large - totallengths from about 25 to about 80+ mm, bodylengths from about 8 mm to 32 mm, dependingon the species. 3  Body oval and broader than it isdeep, especially across gills (behindeyes), with eyes positioned in fromthe sides of the head, and distinctnostrils.Body can be cylindrical (of similar width todepth along length of body), oval and plump(wider than deep), rounded, etc. Eyes oftenright on sides of head (lateral, as in many treefrogs) or just in from sides of body, but someare more dorsal (towards centre of head).Nostrils usually less noticeable (larger in Uperoleia ).Belly black or very dark bluish grey. Belly usually silvery or coppery, or mottled withcopper/gold spots. Clear of most pigment insome.Behaviour: Cane toad tadpolesoften swim in very large swarms of small black tadpoles.Some native species such as C yclorana willform large congregations and school together,but the individual tadpoles are larger andusually dull brown or paler.The tadpoles of the Cane Toad are shown here. Note the features describedabove, such as the eyes in from the sides of the body, the short tail and the blackbelly underneath (middle tadpole). Cane Toad tadpoles. Bar = 5 mm 4
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