Yes, stratified density models can be formulated, which assume uniform animal density within each stratum (area), for which boundaries are determined based on survey coverage, the number of sightings, and prior knowledge of distribution and habitats of mammals :)

Dhaval is the sightings are opportunistic or based on sample design?

stratification would be tough as this sightings would not be based on survey n following proper methodology/samples

Yes, I stated the conditions under which stratified models could be formulated :)

@Arpitbhai, all sightings are opportunistic but, we followed same transects every time.

You can model detectibility, your data seem to be appropriate for this. You need high enough numbers and at least in perfect case (assumed) uniform density. You can find more info. at http://distancesampling.org/ together with an open access tool.

Andrew Paul McKenzie Pegman stated, stratified density models can be formulated. However, depending on which mammal species you are working with, behavior, characteristics, body markings, etc. you can create a photographic data base or just a list of individuals with their particular markings and analyze the data like if you are doing Capture-ReCapture analysis or other statistical methods such as Schnabel. 

https://community.dur.ac.uk/philip.stephens/Papers/Stephens%20et%20al.%202006.pdf

Hope this can be useful to you Dhaval

Thanks

Akshit

Thanks Akshitbhai

I leave a suggestion, though I imagine that the original problem has been solved. Beside the manuals commonly used in population studies (e.g., books of T R E Southwood or G A F Seber), here’s a book that might be useful (in Spanish): ‘Manual for the census of the terrestrial vertebrates’ (Raíces, 1986), by José Luis Tellería. A chapter specifically addresses how to estimate population density based on the sighting of individuals. (But I don’t know if there’s an English edition of this book.)