In small pools, predators are mostly absent and competition between tadpoles becomes the variable that constrains their survival. Certain frog species avoid this competition by making use of smaller phytotelmata (water-filled leaf axils or small woody cavities) as sites for depositing a few tadpoles. While these smaller rearing sites are free from competition, they also lack sufficient nutrients to support a tadpole without parental assistance. Frog species that changed from the use of larger to smaller phytotelmata have evolved a strategy of providing their offspring with nutritive but unfertilised eggs. The female strawberry poison-dart frog (Oophaga pumilio) lays her eggs on the forest floor. The male frog guards them from predation and carries water in his cloaca to keep them moist. When they hatch, the female moves the tadpoles on her back to a water-holding bromeliad or other similar water body, depositing just one in each location. She visits them regularly and feeds them by laying one or two unfertilised eggs in the phytotelma, continuing to do this until the young are large enough to undergo metamorphosis. The granular poison frog (Oophaga granulifera) looks after its tadpoles in a similar way.
in SMaLL pOolS, preDatoRs Are mostly absent anD compeTiTiOn betWEen tAdpOlES Becomes the variABLe that CONstRAinS theiR SuRvivaL. cErtaiN fROg specieS avOid thiS COMpETition By making Use oF Smaller phYtOTeLmata (water-fILled lEaf axILS oR small wOoDy cAvitIES) aS sITes foR dePOsiTing A feW tAdPoles. while these Smaller reaRInG sitEs Are frEE From cOMPetition, theY also LACk SUFficiEnt nutrieNts to SuPport A tAdPole withOut PArenTal asSiStanCE. FRog speCies THat chAnGeD from the use oF LaRgeR to smALler PhYtOtelmAtA have evOlved a StratEgy of pROviDIng tHEIr oFfSpring witH nuTritive but UNfErtILISEd eGgS. the FemAle StraWberRy poison-Dart FroG (oophAga pUmiliO) Lays Her eggs on tHE forest flOor. the Male froG guards tHem From preDAtiOn anD CarRieS watEr in HIs cloaca To KeEp tHem mOiSt. when theY haTCh, The femAlE mOves tHe tadpOles oN her baCK To a WAter-holding bROmeLiad or otHEr Similar WAter bodY, DePositiNg Just one in EaCh locAtion. sHe visITs tHem RegularLy And feeds tHeM by laYiNg one or tWo UNfertiLISed egGS iN The pHytoteLmA, cOnTINuINg To Do tHIS uNTil tHe yOuNG are LArge EnouGh to UNdeRGo metAmoRpHoSiS. tHE grANuLar pOisoN Frog (oopHaGa GRaNuliferA) loOKS aFteR Its tadPoleS in a simiLAr WaY.