What is the most effective approach to define niche of anurans for which no such data is available?
The most commonly method used to study amphibians is doing Visual Encounter Surveys. However, the method you use will depend on the species you target and the study aims. To help you decide, I suggest doing some reading about different methodologies and techniques for species survey and monitoring. Here are good books to start with:
Measuring and monitoring biological diversity: standard methods for amphibians, by Heyer et al. 1994.
Ecological Census Technique: a Handbook, by Sutherland et al. 2006.
Amphibian Ecology and Conservation: A Handbook of Techniques, by Dodd et al. 2009.
Hope this helps and good luck in your future studies!
Thank you for responding, Bela. I would like to rephrase the question as "How do I define which habitat/ environmental variables are affecting certain species of frogs when there are no previous data available for the concerned species other than presence data?"