Predator Masters using UBB.threads ™ Infopop Corporation.
PM Gear Moon & Weather

Welcome to the Predator Masters Forums
Be sure to visit the main Predator Master website at





PM Gear
PM Gear
PM Gear
The Official Predator Masters Search Engine
Search Predator Masters

Topic Options
#53914 - 07/19/01 09:49 AM A hot SEX question for Steve A.
trappnman Offline
Predator Master

Registered: 04/21/01
Posts: 54
Loc: Lake City, MN
Steve- in your post to Wiley, you stated "that the changes in birth sex ratios (a very strong variable)," as part of a larger statement. My question- how/why/when does the birth ratio of the sex change? On all of the major furbearers does this happen? I vaguely know this happens in reptiles, but was unaware that not only it existed for mammals, but apparently does change as you implied on a frequent basis. What's the scoop? Enquiring minds want to know......trappnman

------------------
Your American Heritage- Fur Trapping, Hunting and Fishing

Top
#53915 - 07/19/01 12:56 PM Re: A hot SEX question for Steve A.
steve allen Offline
Predator Master

Registered: 01/05/02
Posts: 88
Loc: Bismarck,ND
Trappnman--I was almost sure I would hit someones button with that one. If you hadn't asked, Wiley almost certainly would have. What we saw in examining pregnant female red fox (about 150) and coyotes (about 300) was a tendency for younger females of both species to have somewhat more males in the litters and older females having somewhat more females in the litters. There was not a really strong difference, but it was there. This, of course, will then likely vary annually, because the age structure of the female population of both species varies annually. I'm sure you remember our discussions earlier about age-related increases in reproductive performance in both species. Thus, if there was a high number of young females in the spring population that typically had somewhat smaller litters than older females, intuitively one could expect the embryonic sex ratio to be somewhat heavy to males.

Now, the "strong variable" part of the comment was referring to the impact of a variable embryonic sex ratio in models of population dynamics (e.g. computer population models). I found that even varying the sex ratio of the incoming pup cohort from 50:50 to say 49.5:50.5 or 50.5:49.5 impacted the population size 10-15 years later quite a bit. A change to say 48.5:51.5 or vice versa really made dramatic changes. I know it doesn't seem like very much until ones examines computer printouts, and starts making the calculations that the computer did to check. Sure enough, the computer was right on the dot; to as many decimals as one wants. Additionally, I used 2 different computer population models, and saw the same results with both of them.

However, we may not see these dramatic population changes 10 years later resulting exclusively from changes in this variable, because the female population next spring will likely have a different age structure than the population did this spring--maybe really different if pelt prices change dramatically and fur harvesters really get after stuff. So you don't think I'm against fur harvesting, my attitude was always and still is "with special consideration for the population in future years, happiness now is a bigger pile of pelts!"

Hopefully, I didn't muddy up the whole thing for you. Post back again if I left something unclear, and we will keep talking.

Top
#53916 - 07/19/01 02:38 PM Re: A hot SEX question for Steve A.
NASA Offline
PM is my life

Registered: 04/22/01
Posts: 9179
Loc: 40.02N/105.25W
Steve- Am I correct in understanding that you said the determining factor in litter sex ratio was the age of the bitch? If true, how would you account for that? I can't comprehend the dynamics that would promote such a trend. Population densities, food availability, prior litter survival rates and such would seem to be a much more predominant factor in determining the m-f litter ratio. How are specifics determined in this kind of analysis?

Top
#53917 - 07/19/01 04:09 PM Re: A hot SEX question for Steve A.
steve allen Offline
Predator Master

Registered: 01/05/02
Posts: 88
Loc: Bismarck,ND
NASA--No I can't say that. I don't have any experimental data at all to show cause and effect of that nature. The only thing I can say is that based on the samples I had available (which I consider small by the way) I saw some indications that more males may be being born to younger females and vice versa for the older females. We really ran into sample size problems in the older age classes of females (>6 years old or so). It would, however, be a fascinating area for some solid research to see if this hypothesis is even remotely possible on a large scale.

I agree in that I can't comprehend the mechanics of how something like this might occur either. And, in fact, really large samples may very well show that it really doesn't occur to a great extent at all.

Good thinking by you and Trappnman. I surely wish I had had a staff to work with comprised of yourself, Trappnman, and Wiley when I was in the wildlife field professionally. You 3 guys, and others as well, are all solid thinkers!

Top
#53918 - 07/19/01 08:01 PM Re: A hot SEX question for Steve A.
NASA Offline
PM is my life

Registered: 04/22/01
Posts: 9179
Loc: 40.02N/105.25W
Steve, who would fund something like (qualified) independent research into these grey or vague areas of coyote biology? Would it be worthwhile to even consider such an undertaking? With the resources available on this board (especially the distribution variable) it might not be all that difficult to organize a network of volunteer field researchers. I'm thinking ahead to the positive PR response that a white paper on something like this could provide for our sport. Since you have an extensive background in organizational research, and the corresponding credentials, you would have a better feel for the effort involved. Remember, we're all linked by e:mail so communication is no barrier. What do you think, got any fire left in 'ya?

Top
#53919 - 07/19/01 09:09 PM Re: A hot SEX question for Steve A.
trappnman Offline
Predator Master

Registered: 04/21/01
Posts: 54
Loc: Lake City, MN
Steve- Thanks for the complement- I'm appreciated more on some forums than others LOL

To draw a conclusion, based on limited data I realize, one would have to say that litter size is part of the equation. That is, smaller litters by young females have more males; larger litters by older females have more bitches. Now- heres a thought- is this then related to the overall care that the female can give her pups? Have you found that either male or female pups have a higher survival rate?.....trappnman

------------------
Your American Heritage- Fur Trapping, Hunting and Fishing

Top
#53920 - 07/20/01 07:23 AM Re: A hot SEX question for Steve A.
steve allen Offline
Predator Master

Registered: 01/05/02
Posts: 88
Loc: Bismarck,ND
NASA--An interesting thought, but it wouldn't really be in the category of super data like some areas of research would be. You're correct in that the distribution of potential data collection would be very good. However, the logistics of collecting and handling large numbers of tissue samples would be virtually impossible. Also, there is the resulting histological work that needs to be done that would also be next to impossible unless I did all that. That is fun stuff, but also necessitates a lot of expense; mostly money but also time. Data processing is also a problem as I no longer have access to all the computer software I used in the past. Fire and horsepower is not a limiting factor.

However, if promoting predator related activities is an objective, there is something that can be done that eliminates all the above logistical problems. All of us could volunteer to put on a class through your local hunter safety class or whatever and teach kids what we know about predators, hunting and trapping. All of you know a lot of stuff; certainly more than most 12 year olds. My own experience with kids is that 2 arm loads of tanned furs, a slide show, and a half dozen back issues of Trapper and Predator Caller and I have everyone's attention including the teacher. Almost everytime there are 1 or several kids that are really attracted to it all. These kids might well be the next generation of predator hunters/trappers. That would be a really good way for all of us to reproduce ourselves for the good of fur hunting and trapping.

Top
#53921 - 07/20/01 07:39 AM Re: A hot SEX question for Steve A.
steve allen Offline
Predator Master

Registered: 01/05/02
Posts: 88
Loc: Bismarck,ND
Trappnman--My guess is that litter sex ratios are not determined by care a female can give the litter, but I certainly don't know this for sure at all. The reason I say this is because gender is "assigned" to each living embryo very early in gestation, and probably way before the female is even thinking about den sites or anything else along that line.

I don't have any data to show differential survival rates between males and females within pregnant females or at dens after pups are born. There are different rates of mortality by age/sex once the fur harvest starts. Young males tend to be taken at a disproportionate higher rate, and adults at a similar lower rate than they occur in the population.

Top
#53922 - 07/20/01 08:02 AM Re: A hot SEX question for Steve A.
trappnman Offline
Predator Master

Registered: 04/21/01
Posts: 54
Loc: Lake City, MN
Steve- I am having a hard time explaining this. Look at it this way:

Young Females = less experience at raising pups = smaller litters = more males

Older Females = more pup raising experience = larger litters = more females

What is the primary genetic disposition here? to me you can see a pattern of cause and effect (or one of those dang physics laws LOL) Now why these patterns seem to exist is what puzzles me- hence my question if one sex has a higher % of reaching the juvenile stage.....trappnman

------------------
Your American Heritage- Fur Trapping, Hunting and Fishing

Top
#53923 - 07/20/01 07:00 PM Re: A hot SEX question for Steve A.
steve allen Offline
Predator Master

Registered: 01/05/02
Posts: 88
Loc: Bismarck,ND
Trappnman--Excellent thinking on your part and you make an equally excellent point. Let me muddy the waters somewhat re: your equations. What happens if the differences we see in relation to female age class are not really the age class itself? By that I mean what happens if something is occurring inside females (but not necessarily the same in all females; maybe genetic differences) that is causing improved reproductive performance that is related to her age, but it is not age class itself that is causing the changes?

What could these be? Potentially we might see significant changes in endocrinology in females related to her age that promotes larger litters (higher ovulation rate) and better intrauterine survival of embryos (lower prenatal mortality) that results in higher litter sizes. If one could measure condition accurately in carcasses that have been dead multiple days, we might see changes there as well that are reflected to age class, but not necessarily caused directly by age itself. We might also see some other physiological changes within females that is directly related to increased litter size. What I mean is that age class may be a reflection of something going on inside females, but not necessarily directly the cause. Hope I didn't lose you with this one.

Another concept I have thought about; what about the pair bond between alpha family members and its influence on litter size. What happens if a strengthing social relationship between mated pairs as age increases is conducive to higher reproductive performance? What happens if the alpha male is killed and replaced by a new male of a younger age (our data showed this is what happens)? Does her litter size continue to increase, or does it decline to some lower level and increases as the pair bond strengthens to the level that existed with the original alpha male? All this can kind of get mind boggling, but all these things are real possibilities and we can't really measure any of them. Lack of technology at this point.

I like your equations and again they show excellent thinking on your part, but one needs to be cautious because we may need to modify our perspective of the 1st variable. If we could get a correct and complete look at the 1st variable, then we would have a better idea what other variables to add or delete from the equations.

Top
#53924 - 07/21/01 08:07 AM Re: A hot SEX question for Steve A.
trappnman Offline
Predator Master

Registered: 04/21/01
Posts: 54
Loc: Lake City, MN
I can see how complex something like this gets. Now here is another thing to consider- which in a way contridicts what we were saying earlier. I take this for a fact- I have seen extensive data on this published back in the 80's in Hounds and Hunting magazine concerning data on quality of pups vs litter #. George Nixon, who raised literally hundreds of beagle Field Champions, kept records showing field ability of each pup- and consistently, bitch after bitch- had her best performers in her first litter or two. The good producers of course produced well in every litter- but the % of good pups declined each time. THe moral of the story was that if you were breeding hounds, the worse thing you could do was "breed a good bitch to a buddy's dog to see what she produced, then if there was anything in that litter, breed her to a real good stud". The wise breeder bred to the best he could afford for that first litter.

Now- wouldn't you think that something this basic to the genetic makeup of domestic dogs
would also have a good chance of being present in wild canines? (But of course I know that there ARE many genetic difference, pair bonding for one. Darn it Steve- why didn't you think of all this stuff back when you were collecting data. Think of the book you could have written "The Definitive Book on Coyote Behavior" ILMAO trappnman

"So many questions, not enough answers"

------------------
Your American Heritage- Fur Trapping, Hunting and Fishing

Top
#53925 - 07/21/01 10:02 AM Re: A hot SEX question for Steve A.
steve allen Offline
Predator Master

Registered: 01/05/02
Posts: 88
Loc: Bismarck,ND
Trappnman--I would say there is a good possibility that some of the traits you point out in domestic dog production such as pup quality might well also exist in wild canids in some form. The problem, of course, is how do we identify that these traits exist, how do we measure them in the wild canids, and how do we ever get a sufficient sample size to be meaningful? As we've discussed earlier that is another example of technology to do these things has not kept up with the ideas.

I did think of a lot of this stuff, when I was still professionally in the field. Often the problem was lack of technology, lack of adequate funds, politics, and lack of time resulting from needs with higher priorities. I'm sure your cousin Mike G. would concur on these points, and maybe add a couple others.

Top
#53926 - 07/21/01 07:01 PM Re: A hot SEX question for Steve A.
steve allen Offline
Predator Master

Registered: 01/05/02
Posts: 88
Loc: Bismarck,ND
Here is another piece of data for the puzzle. I got an e-mail from Steve Craig in AZ yesterday, and he indicated he sees about the opposite in AZ coyote litters re: sex ratios. He is seeing somewhat more females in the smaller litters and more males in the larger litters. I don't doubt Steve's observations for a minute because he is an excellent student of the animal, and it further indicates to me what I questioned from the onset that the sample size of coyotes I had (about 300) was not large enough to detect the true embryonic sex ratio.

Further, it indicates that lots of these biological phenomena we try to document can require huge sample sizes of animals from varied areas to get a true picture of what really is occurring. Even though I had about 300 females collected in April and early May, the required sample size to document some things might very well be in the thousands. Not that the effort isn't worth it, but one needs to prioritize where he is going to spend his effort. I think everyone can appreciate the magnitude of effort required in some investigations.

Top



Moderator:  Infidel 762 

© Predator Masters™, All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.