Selection analysis:
For litter size, we found only a positive effect of the mother’s mass in
June and no effect of pup emergence date (neither linear nor quadratic)
(Table 4). For the proportion of pups in a litter surviving to one year
old, we found only a negative linear effect of pup emergence date (Table
4, Figure 4a). For the total number of pups in a litter surviving to one
year old, we found a positive effect of maternal mass in June and a
negative linear effect of pup emergence date (Table 4, Figure 4b). In
addition, we found an effect of valley with more pups surviving to one
year old in the up-valley compared to in the down-valley (Table 4).
Table 4. GLMM (number of females
= 176; number of litters = 417) determining the association of pup
emergence date with the weighted proportion of pups surviving their
first winter (binomial distribution), the total number of pups surviving
their first winter (Poisson distribution), and litter size (Poisson
distribution). Reference category is down-valley for valley. Pup
emergence date was fitted using orthogonal polynomials.