Montana Mule Deer Mismanagement

[rogerthat]

I haven’t followed this thread much, but did see some of the discussion/questioning about biases in the age sampling. Apologies if someone else already mentioned this but I didn’t want to wade through all the arguing.

But from what you guys were saying, the age data being referenced were tooth cementum data collected from CWD sampled individuals? If this is true, it’s quite possible there is a sampling bias against younger age class animals, as most states don’t bother collecting CWD samples from 1-2 year olds. Or they are at least way lower priority. Not sure if Montana is following that strategy, but it would not surprise me.

Just a point for thought. Carry on.

I think Montanas system is to submit all voluntary provided samples for Cwd testing and part of that is to pluck a tooth and submit to Matsons to build an age profile of the Cwd positive and negative samples. So the bias would have to be from the decision of the hunters when deciding to have their buck tested. The ages 100% indicates an age structure of the deer tested for Cwd. I think the question is whether the age data can it be used to and does this age structure indicate overall harvest age structure? Thoughts on the voluntary nature of the sampling?

 

[Hunting Wife]

I think Montanas system is to submit all voluntary provided samples for Cwd testing and part of that is to pluck a tooth and submit to Matsons to build an age profile of the Cwd positive and negative samples. So the bias would have to be from the decision of the hunters when deciding to have their buck tested. The ages 100% indicates an age structure of the deer tested for Cwd. I think the question is whether the age data can it be used to and does this age structure indicate overall harvest age structure? Thoughts on the voluntary nature of the sampling?

My gut feeling is that collecting samples for a specific purpose (CWD) that has a well-documented and publicized age bias, then trying to use those data for a second purpose (to represent the age structure of the population at large) may not be the best sampling strategy for that second purpose. Though I get the temptation because sampling and testing samples is labor and money intensive.

I am not a stats/study design expert by any means. But I talk to a lot of hunters and I collect samples if they want it done. Most people I talk to are familiar with the research, and in my experience they are much more likely to want it sampled if it is older and they think it might be a good candidate or more likely to have CWD. So yes, I think there is potential bias in who volunteers a sample.

 

[Rie Bread]

My gut feeling is that collecting samples for a specific purpose (CWD) that has a well-documented and publicized age bias, then trying to use those data for a second purpose (to represent the age structure of the population at large) may not be the best sampling strategy for that second purpose. Though I get the temptation because sampling and testing samples is labor and money intensive.

I am not a stats/study design expert by any means. But I talk to a lot of hunters and I collect samples if they want it done. Most people I talk to are familiar with the research, and in my experience they are much more likely to want it sampled if it is older and they think it might be a good candidate or more likely to have CWD. So yes, I think there is potential bias in who volunteers a sample.

Not only that but the fact hunters are trying to shoot older deer in general adds to the bias

 

[Gerald Martin]

My gut feeling is that collecting samples for a specific purpose (CWD) that has a well-documented and publicized age bias, then trying to use those data for a second purpose (to represent the age structure of the population at large) may not be the best sampling strategy for that second purpose. Though I get the temptation because sampling and testing samples is labor and money intensive.

I am not a stats/study design expert by any means. But I talk to a lot of hunters and I collect samples if they want it done. Most people I talk to are familiar with the research, and in my experience they are much more likely to want it sampled if it is older and they think it might be a good candidate or more likely to have CWD. So yes, I think there is potential bias in who volunteers a sample.

This was my reaction as well. FWP is not biased in their sampling but hunters are consciously or subconsciously skewing sampling results because they know older age class deer are more likely to be CWD positive and they’re submitting what they believe to be older deer at a higher rate than deer believed to be younger.

 

[Hunting Wife]

This was my reaction as well. FWP is not biased in their sampling but hunters a consciously of subconsciously skewing sampling results because they know older age class deer are more likely to be CWD positive and they’re submitting what they believe to be older deer at a higher rate than deer believed to be younger.

Yes. It is important that your sampling strategy is designed with your question in mind. They are not necessarily interchangeable, for exactly this reason.

 

[Rie Bread]

So I guess with the cwd data the prevalence of younger 4x4 is kinda moot then?

 

[Gerald Martin]

So I guess with the cwd data the prevalence of younger 4x4 is kinda moot then?

I’m not completely sure of your point but we all know that a 4x4 is automatically 8 years old…. (joking)

 

[Rie Bread]

I’m not completely sure of your point but we all know that a 4x4 is automatically 8 years old…. (joking)

Well 4.5 is young to 8.5 haha