3.3 Skull dimensions in all three age categories from 1955 to
1985
Skull height, width, and length were significantly correlated with age
(confirming the typical seasonal size change pattern; Table 3A). Only
the skull height showed a negative significant relationship with year,
and the interaction between year and age was significant when included
in this model (F 2,289=5.23, P =0.0058).
All measures of skull size differed significantly between the age
categories (Table 3B). Skull height decreased significantly by 14.4%
from summer juveniles to winter subadults and regrew by 7.4% in the
following summer adults. Skull width followed this pattern with a lesser
but statistically significant decrease of 1.4% and then an increase of
1.9%. The 2.0% decrease in skull length from juveniles to subadults
was also statistically significant (Table 3B).