Optimal monitoring when detectability varies – my talk at #ESAus2012

Edit: A paper based on this work has now been published in PLoS One (open access, i.e. free). doi: 10.1371/journal.pone.0115345.

I’m looking forward to the Ecological Society of Australia conference this week. I’m speaking in the second time slot (2:15 p.m.) of the last session on Thursday (the last day). Check out the other QAEcology talks here.

I am sandwiched between two Bayesian talks. I’ve heard a rumour that Gerry Quinn and Ralph Mac Nally will present an entertaining double act (prior to me), while Brendan Wintle will be talking about Bayesian detection (posterior to me; sorry about that. I couldn’t resist…).

How many surveys should be done to account for variation in detectability?

My talk will discuss how to optimize the number of times one should survey a site to maximize the chance of observing a species. This might be the number of nights to survey a stream to find a frog species, or the number of plots to search to detect a species in a region, or even the number of searchers to send to a site.

The key is that because of variation in detectability (over time, over space, or among people), a single visit to a site (or a single site within a region) might have, by chance, a low probability of detection. So there is an incentive to search more than once – that will increase the chance of having a higher detection rate at least once. However, going more than one incurs greater travel costs, which eats into the time available to actually search.

The tension between more shorter searches (with extra travel time) and fewer longer searches (with less total travel time) creates a trade-off. We developed and analyzed a model to optimize this trade-off. And we used a field experiment to evaluate it.

If you want a sneak preview, a pdf file of my slides (minus the best jokes) is posted here.

I’ll also be auto-tweeting this talk using the hash-tag #micktalk in case you can’t make it to Melbourne and want to follow along with the slides. For overseas folk, my talk is on Thursday 1415 Melbourne summer time, which is Thursday0315 UTC (I’m not expecting too many folks following along in London!), Wednesday1915 in Los Angeles, and Wednesday 2215 in New York.