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#53806 - 03/03/01 06:58 AM Re: How many pups
howler Offline
Die Hard Member III

Registered: 04/20/01
Posts: 2027
Loc: Glasgow, Mt.
I guess I addressed the post to Steve But I want everyone to respond

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#53807 - 03/03/01 07:28 AM Re: Re: How many pups
coyoteseeker Offline
Junior Member

Registered: 01/06/02
Posts: 36
Loc: victor,ny-USA
you are absolutly right,this is why coyotes will never be elimanated from this planet.on a normal year they will drop 3 to 5 pups and in years of mass die off(for what ever reason)they will drop 10 to 14 pups.this is truely an amazing safe gaurd that nature has given the coyote.i don't believe that any other animal has it that way.

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#53808 - 03/03/01 07:42 PM Re: Re: How many pups
steve allen Offline
Predator Master

Registered: 01/05/02
Posts: 88
Loc: Bismarck,ND
Howler--That is a very good question. This came up about a month ago on Posse Country, too. The answer is a lot longer than what you might expect, so here goes.

First, I need to go thru the results of a couple of studies I conducted in the past. We examined coyote reproductive performance to determine what factors were the main players in affecting reproductive performance. We collected almost 300 females from 15 Mar-15 May 1980-1987 in North Dakota and eastern Montana. We looked at lots of stuff, but for this discussion we'll stick to litter sizes. The influencing factors we examined were female age class, relative condition, animal size, and year. Our data was not good enough to examine the affect of population size. We found the strongest factor we tested was female age class. The other factors we tested were essentially non-players in influencing litter size.

We found one year old females averaged about 0.75 pups/litter and 6 and greater year old females averaged about 6 pups/litter. Each age class between 1 and 6 showed increasing litter sizes by age class.

Another study we did was to examine the mechanics of the annual harvest. By this I mean which age/sex classes are dying and when. We found that the annual harvest starts it consists of a disproportionate amount of young animals compared to their level in the population. We also found that if lots of mortality pressure is applied to the population in the harvest, most of the younger age classes will be dead by late winter so that the survivors are primarily older age coyotes. Vice versa for light harvest--lots of surviving young animals; so much so that one seldom finds an older animal.

Now lets say we have 2 study areas of about 50,00 sq. miles each--one lightly harvested and the other heavily harvested. If we take a sample of females from the lightly harvested area in the spring we will find an average litter size of 2 or 3 or thereabouts. But if we take a sample of females from the heavily harvested area will likely find an average litter size of at least 5 but probably somewhere between 6 and 8.

What's the problem. The problem in the 2 samples is that they were not examined by female age class. If they had been, we would have seen the sample from the lightly harvested area was composed almost exclusively of younger females, because they are still alive. We already know these animals have smaller litter sizes from the reproductive work. In comparison, the sample from the heavily harvested area was composed of almost all older females (they survived the mortality pressure). These females we know inherently have larger litters anyway.

Thus, on the surface it looks like mortality pressure automatically causes higher litter sizes. But it does not. The mortality changes the age structure of the population, and creates a biased sample that looks like higher litter sizes.

As far as the population is concerned the lighter harvested population will have the greatest total increase in size next year. However, the heavily harvested population will have the greatest % increase in size the next year.

A very long answer to a short question. Sorry, but we need to know the whole story about the animal, and sometimes the answers can be very long. If anyone is confused, it is because I didn't get it explained so that you can understand it; be sure to post again and we will keep talking/discussing until you understand.

That almost calls for a glass of burgundy and some popcorn, doesn't it!

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#53809 - 03/03/01 07:47 PM Re: Re: How many pups
steve allen Offline
Predator Master

Registered: 01/05/02
Posts: 88
Loc: Bismarck,ND
Howler--Oops, I forgot the rest of your question; north v. south litter sizes. I don't think the data is available from the southern part of coyote country to answer that.

I would guess that litter sizes might well be somewhat different, but I would also guess that female age class would be a very strong influence there just like it was in the northern plains.

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#53810 - 03/04/01 10:37 AM Re: Re: How many pups
coyoteseeker Offline
Junior Member

Registered: 01/06/02
Posts: 36
Loc: victor,ny-USA
thats an interesting answer and it makes alot of sense.thru my own experience it is true that most coyotes harvested are young inexperenced animals.leaving the older females to reproduce.just like in alot of cannine spieces the older females always have bigger litters then the yearling ones.

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#53811 - 03/04/01 11:36 AM Re: Re: How many pups
Cal Taylor Offline
Die Hard Member

Registered: 05/10/01
Posts: 545
Loc: Gillette Wy.
Here's a theory for you Steve.
When coyote numbers are low, the prey base numbers are higher, therefore the coyotes that are there are far better fed and generally have an easier time due to less competition. I believe that a female in better shape will have more, and healthier, pups. When coyote numbers are high, the prey base suffers. Coyotes have a tougher time, females are in poorer shape, and have less pups, and less healthy pups. I have denned in high and low cycles and really believe this has some effect. I do agree that age is a factor, but I have killed two and three year old bitches that had 7 or 8 pups several times, and killed one bitch I believed to be a three year old that had 11. I'm fairly sure these numbers are accurate because I usually cut them open to count attachments to the uterine wall, and have dug up several of these dens after smoking them. What do you think?????

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#53812 - 03/04/01 02:26 PM Re: Re: How many pups
steve allen Offline
Predator Master

Registered: 01/05/02
Posts: 88
Loc: Bismarck,ND
Cal--We didn't see any influence of our measure of relative condition on litter sizes. However, I will be the first to admit our measure of body fat as an indicator of condition was crude at best and uninformative at worst. The problem is how to measure condition on animals that have been dead up to several days, and there simply isn't much available that is expedient to collect in the field on "very dead" specimens.

In looking at food I never saw where coyotes or red fox ever ran short of food at any densities at any time of year. There is so much variety (at least here) that if one thing isn't available for whatever reason, they simply eat something else. Also these species are so good at finding food that it is almost like you or I going over to the refrigerator and opening the door. But food availability doesn't necessarily tell us much about condition either, unfortunately.

If we could accurately determine condition in the field (or take some specimen back to the lab to test it), we might very well find that improving physical condition in older females is the factor that older age class is trying to tell us actually affects litter size. Age class is likely an indicator of something that is going on inside the female; that "something" is what is actually causing the increased litter sizes.

Also, we found that counting placental scars in uteri (attachment points of embryos) tended to overestimate actual litter sizes, and pup counts at dens (even completely dug dens) tended to underestimate actual litter sizes. The other problem one encounters at dens is pups from more than 1 female in the same den. It is easy to tell the obvious differences in pup ages at some "double dens", but if 2 females whelped a day or 2 apart we likely wouldn't know this by looking at the pups.

Those are some really good observation on your part, and I can already tell you have been and are doing some serious thinking about the animal in general and this stuff in particular. Keep up the good work, and keep posting your observations and ideas!

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#53813 - 03/04/01 07:37 PM Re: Re: How many pups
Cal Taylor Offline
Die Hard Member

Registered: 05/10/01
Posts: 545
Loc: Gillette Wy.
Steve,
I'm glad to see that you subscribe to the double den theory. I have seen a couple and know that it happens. I have taken pups of at least a months age difference out of the same hole. I have also been told that it doesn't happen. Oddly enough I have never been able to kill two wet bitches off the same hole. I just attribute it to bad timing on my part, not being able to catch everyone home at the same time. I have many times killed two females off of a den, along with the dog, but one female is always a dry yearling or two year old. I have mistaken the "baby sitter" for the wet bitch more than once, and it can be a little frustrating. Anyway, I sure enjoy having a couple of you educated fellers around. I will have many questions to come.

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#53814 - 03/04/01 08:35 PM Re: Re: How many pups
steve allen Offline
Predator Master

Registered: 01/05/02
Posts: 88
Loc: Bismarck,ND
Cal--Another phenomenon that happens at least in red fox is pup adoption. A stray red fox pup roaming around that is found by a neighboring adult fox has immediately found himself a home.

We suspected this when we were digging up dens and tagging red fox pups in the 70's. We did this experimentally just to see if we were right. We dropped off 2-7 week old fox pups with ear tags into a road ditch at dark about 1/2 mile from an active fox den. The next morning both pups were at the den playing with their newly adopted littermates like they had been born there. Also, the resident littermates were about twice the size of the newly adopted pups.

Now, can that same thing happen coyotes? We don't know; however, I would suspect it could based on what we saw with the foxes.

It seems like there is always something new to complicate things, isn't there?

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#53815 - 03/05/01 07:36 AM Re: Re: How many pups
Nebraska Coyote Hunter Offline
Seasoned Member

Registered: 04/23/01
Posts: 187
Loc: Elkhorn, NE USA
Steve,

Is it safe to say then that coyotes do not have the ability to increase their litter sizes when their population is suppressed?

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#53816 - 03/05/01 05:53 PM Re: Re: How many pups
steve allen Offline
Predator Master

Registered: 01/05/02
Posts: 88
Loc: Bismarck,ND
Nebraska coyote hunter--That is exactly correct.

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#53817 - 03/05/01 06:05 PM Re: Re: How many pups
steve allen Offline
Predator Master

Registered: 01/05/02
Posts: 88
Loc: Bismarck,ND
Cal--I forgot to address a comment you made in a previous post. You indicated some individuals have said that "double dens" don't exist. They simply haven't visited enough dens (maybe none), because the coyotes are telling both of us that they do exist.

Also, if you're interested in this pup adoption business with coyotes and how it might relate to "double dens", post back and I'll tell you how to do it. It sounds like you are around a fair number of dens and pups. It would be an interesting experiment and you will be directly involved in advancing science. If you're not interested, that is fine too.

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#53818 - 03/06/01 02:12 AM Re: Re: How many pups
Cal Taylor Offline
Die Hard Member

Registered: 05/10/01
Posts: 545
Loc: Gillette Wy.
Steve,
Always interested. I know some strange things happen. I have been told by two other ADC men, both of whom I trust completely, that they have seen a dry bitch adopt pups and raise them. They have cut them open to find no uterine scars, but they had came to milk. I wouldn't believe it, but these guys take dozens of dens yearly, and dang sure know what they are looking at. Every time it has been after the wet bitch was killed one way or another and the den wasn't found right away. Another interesting thing I have personally seen is a wet bitch finding another dog to help raise pups after her mate was killed. I have seen this several times when I have killed the dominate male.

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#53819 - 03/06/01 06:28 AM Re: Re: How many pups
steve allen Offline
Predator Master

Registered: 01/05/02
Posts: 88
Loc: Bismarck,ND
Cal--Another thing that happens is that most if not all coyote families have at least 3 adults in them. We saw this in the 70's, when we had radio collars on adult coyotes. The extra adults could be either sex, and at least all that we handled were yearling animals; one of which we identified as a pup from the litter the previous year by the ear tags. Thus, if something happens to the dominant male or female there are likely always other adults immediately available to assist in pup raising.

Re: the adoption thing the first thing you need is an active coyote den with pups present that you can observe from 3/4 mile or so with a spotting scope. Then you need to capture a couple of pups of almost any age from 1 or more other dens somewhere else, and pup some ear tags in them. Self piercing cattle/sheep tags work fine as long as they are not to big. Weigh each animal (e.g. a bathroom scale is ok) and record the sex. Put a tag in each ear; yellow tags on 1 pup, orange on another, green on the 3rd, or something like that so you can tell individuals when observing the new den with your spotting scope. About dark some night drive to with a 1/2 mile or so and drop your tagged pups off with a minimum of disturbance and drive away.

Now the fun starts. Try to be out to your pre-selected observation point the next morning/evening for the next several days. If the pups are at the den living it up, you'll know the adoption answer about coyotes. With different colors on each pup you can identify individuals and what they are doing. If they don't show up at the den you won't know if they weren't at the den and are somewhere else (coyotes and red fox often have more than 1 active den at the same time), or if the adults killed them.

Keep in touch on how it goes, if you decide to do it and what you find out.

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#53820 - 03/08/01 07:50 PM Re: Re: How many pups
Wiley E Offline
Seasoned Member

Registered: 04/21/01
Posts: 410
Loc: Kadoka, S.D.
Steve, I am finally able to check out your awesome forum again.

Litter size, always an interesting topic. I have always stated that litter size increases or decreases with prey availability. Based on the studies I have reviewed, that is how I always interpreted it. Maybe it was misinterpreted and a result of population dynamics as you stated than the result of prey availability. I trust your judgement on this and our many years of checking coyotes would confirm your thoughts. Interesting curve ball and worthy of consideration!

Well, here comes a slider back at you from the book you were trying to remember, "Wild Furbearer Management and Conservation in North America":

Pups are born after a gestation period of 60 - 63 days. Litter size varies primarily with prey availability. Gier (1968) reported mean litter sizes of 4.8-5.1 in years with low rodent numbers but litter sizes of 5.8-6.2 during years of high rodent numbers. In Alberta, Todd and Keith (1976) observed correlated decreases in ovulation rates and snowshoe hare abundance. Knowlton (1972) reported an increase in mean litter size from 4.3-6.9 with decreasing coyote densities in Texas. Mean numbers of corpora lutea for captive coyotes range from 5.6 for 2-year olds to 7.1 for 4 year olds (Kennelly 1978). Counts of fetuses or placental scars in western U.S. coyote control areas are as high as 14-17, suggesting compensatory reproduction (Gier 1968: J.M. Laughlin. pers. commun.). Nellis and Keith (1976) reported a 9% embryo loss between ovulation and parturition, whereas Gipson et al. (1975) reported a 27% loss. More detailed accounts of coyote reproduction can be found in Kennelly (1978) and Bwekoff (1982).


Here's another piece of information from a post listed above:
http://texnat.tamu.edu/symp/coyote/p1.htm

Steve, if you could find some time could you read the information from the above link and summarize it for us. In considering population dynamics, you can probably provide a broader picture of the issue then we see at face value when reading this.

Now from personal observation of checking years and years of females based on embryos, uterine scars, and counting pups, we consistently reach an average litter size of 5 1/2. Through the fur boom to current years, it didn't change and we check hundreds of female coyotes every year statewide. The problem with our observations is that we check all females so it is not broken down by age classes. We have also found that usually 60% of the females are bred. The ones that aren't are usually yearling females. For what that's worth. I wish we had it broke down by age classes as that would provide a bigger picture.

Steve, will be anxiously awaiting your response to the above taken directly from the Furbearer Biologists Bible. Wiley E


[This message has been edited by Wiley E (edited 03-09-2001).]

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