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).]