Age of Rabbits Measured "By Eye"
The European rabbit Orzctolagus cuniculus is a major pest in Australia.
A reliable method of age determination for rabbits caught in the wild
would be of importance in ecological studies. In a studz bz Dudzinski
and Mykytowycz (1961), the dry weight of the eye lens was measured for
71 free-living wild rabbits of known age. Eye lens weight tends to vary
much less with environmental conditions than does total body weight, and
therefore may be u much better indicator of age.
The rabbits were born and lived free in an experimental 1.7 acre enclosure
at Cungahlin, ACT. The birth data and historz of each individual were
accurately known. Rabbits in the enclosure depended on the natural food
supply. In this experiment, 18 of the eye lenses were collected from rabbits
that died in the course of the studz from various causes such as coccidiosis,
bird predation or starvation. The remaining 53 rabbits were deliberately 
killed, immediately after beeing caught in the enclosure or after they had
been kept for some time in cages. The lenses were preserved and their dry
weight determined.
Here we take R = eye lens weight in mg.
             x = age in days
Dudzinski and Kykytowycz suggest the deterministic relationship
             R = \theta_1 \exp\{-\theta_2/(\theta_3+x\}