Design for scat closed robust model

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Design for scat closed robust model

Postby lisark » Wed May 31, 2023 9:06 pm

Hi phidot community,

We are designing a sampling regime to monitor a vulnerable species of bat using a closed robust model with genotyped scats, and would really appreciate any feedback on the design please.

Although genetic data suggests there is mixing of individuals across a very large area, the constraints of the project require an abundance estimate in each of three study areas within the larger area.
It seems to me this would only be logical if the colonies prefer these areas, at least at the times of the year we are monitoring, otherwise the ‘population’ we wish to estimate becomes ambiguous.

Provided we can logically define the populations to be estimated, we will have data from roughly 10 roosts in each area, chosen for their abundance of bats. It is possible some roosts will have been missed, but we think most roosts will be sampled, based on knowledge from the field.

To achieve sampling closure within the year we plan to sample during the mating season in July and August when it’s expected the population is unchanging. That is, males and females don’t range far from their roosts and before births have not yet occurred. The duration of sampling also will not be longer than we expect a bat to live. Sampling will be divided into multiple periods. Each period will begin when a scat collection sheet is laid down beneath the roost and end when it is collected.

The length of each sampling period (e.g. day, week) will be determined from simulation studies, once we know expected capture and recapture rates and genotyping error. The sampling periods may be successive, but do not have to be.

Scats will be collected by random sampling (if too many for a complete census) at a rate 2.5-3 times more than assumed number of bats, to ensure we have enough positive ids from the lab. All scats will be sent for genotyping.

Data from roosts in each sampling period in each area will be pooled before analysis.
Independent estimates obtained from visual counts will be included to validate the mark-recapture method.
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