Estimating abundance of different age/sex classes using cluster observations (CTDS)

[Tristen Brush]

Hi all,

I'm looking for some guidance on whether it's feasible to estimate abundance by age/sex class in CTDS when animals occur in clusters, often with >1 class in a single observation.

For example, I have images with an adult female and a juvenile elk. Can I separate one of these observations into 1 record of 1 adult female and 1 record of 1 juvenile so that I can stratify my results by class? And in that case, do I need to input distances to each individual or can I still use the distance to the centre of the cluster for both records?

Much appreciated,

Tristen

[Eric Rexstad]

Tristen

Good to hear from you again and you are continuing your distance sampling "journey".

At a superficial level, I think you can separate your individual animals and record multiple detections of single individuals; in which case I would think the distances to the individual animals would be recorded in the data.

There may be nuances about animals in groups with camera traps of which I am unaware, but if I'm wrong somebody on the list will set me straight.

---

From: distance...@googlegroups.com <distance...@googlegroups.com> on behalf of Tristen Brush <teb...@gmail.com>
Sent: 02 September 2025 19:28
To: distance-sampling <distance...@googlegroups.com>
Subject: [distance-sampling] Estimating abundance of different age/sex classes using cluster observations (CTDS)

 

--
You received this message because you are subscribed to the Google Groups "distance-sampling" group.
To unsubscribe from this group and stop receiving emails from it, send an email to distance-sampl...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/distance-sampling/9ac4261b-ed59-4383-833a-bce818111b13n%40googlegroups.com.

[Tristen Brush]

Thanks Eric! That's what I was thinking but wanted to confirm before I go through the work of doing more distance measurements.

I am working on my MSc and will hopefully have a manuscript ready in the next few months to share more CTDS research with the world!

Best,

Tristen