To avoid pseudo-replication, only images taken 30 min of a previous photo to the same event are considered as independent records. I think 30 minutes seems excessive to avoid pseudo-replication between photographs. I am sure that at times, different individuals (animals) could pass the same camera trap within 30 mins. Can anyone give reasoning a little more?
I've seen a lot of different times used as the cutoff to determine individual events and that will vary depending the species you are studying and what is known about their behavior. If this was something that I was really concerned with, I would be looking for projects that used radiotelemetry or had marked individuals or individuals that were easily identified through spot patterns or some such means to get some comparative data on how long the species you are studying tend to linger at a camera site.
You might be able to generate some of this sort of information from your own images. For example, you might look at time between camera events by species on a given night or how many times a certain species is photographed only once a night. If 95% of the time species x is only photographed once a night, maybe there isn't a big need to worry too much about the very few times you get two photos in a night. Now, if you're getting photos of species y almost hourly and are trying to use that data to say something about the number of species y in the area, then the cutoff time between events is really important.
Many of the settings, cut-offs used in camera trapping are historical hold-overs from the time when memories could hold only a few (compared with current capacities) images, and deactivating the camera for several minutes after an image capture was a convenieint way of not exceeding memory capacity.
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