We would like to estimate the population size of an animal across the landscape, covering approx 20,000 km2 area. We expect the poplation size to be not more than 30 -40. Since such a large area is to be covered, the only 10% of said area can be sampled. How do I estimate the density of such a population?
Good question. If the occupancy (psi) and probability of detection (p) are very low, could be very difficult to calculate both parameters. I recommend you Designing occupancy studies: general advice and allocating survey effort from MacKenzie & Royle (see attached). Maybe you can increase you survey effort or use covariates for psi and/or p.
I guess for occupancy you will have to use larger units in the survey although, as Jose pointed out, surveying larger units means increased surveying effort. For population size, the standard would be marking and re-capturing. But I don't know what species you are looking at, so it may not work...
It is very difficult but you can try with the Video-UVC method. (see attached)
Article An equation to estimate absolute population density from vis...
What type of animal? The possibilities will vary greatly depending on the species ecology, so some description would help. For example, if it were a large vagile mammal like a bear, DNA based methods from hair trapping might work in a capture-mark-recapture framework, but obviously would not work for a territorial bird for example. Provide a bit more description.
I wanted to estimate the density of the great indian bustard. it is large territorial bird seen in flocks of 2-3.
Settled video camera might be useful for your survey. You can set several settled camera in different sits, based on the figures in your video, then calculated the population size.
Can the bustards be individually identified, or perhaps captured and individually marked with e.g. patatgial tags? If so, then photo ID could work nicely using mark recapture approaches, presumably open population estimators (e.g. http://link.springer.com/article/10.1198%2F108571101750524553 ). However, you will need some stratification of sampling locations to get a truly valid estimate.
Could you involve local communities in any way? Great Indian bustards are easily identifiable so could you use social surveys to find out if people have seen them? It might at least provide a way to select which 10% to sample.
You could also equip target groups (forest users, wood cutters, honey collectors, poachers) with digital cameras with built in GPS and get them to take photos when they see a bustard. This has been done with various species but it depends on local culture, your existing relations with local communities, your budget, scale and duration of your research etc. etc.
thank you for your responses. let me see how i can work it out
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