Suchergebnisse

Patterns of distribution and use of rabbit warrens in 540 acres (219 ha) of subalpine habitat during 1963 and 1966-71 are described. The numbers of rabbits and of burrows in which they live can fluctuate independently of each other. It is demonstrated in a marked population that careful measurement of changes in burrow use can be used to estimate changes in the numbers of rabbits using the burrows.

The most favourable habitat for rabbits in subalpine regions is raised areas on the floor and sides of valleys in open alpine grasslands, where there are projecting granite tors and moraine-like materials.

Shot samples of rabbits were collected over several years at 11 sites in Australia and one in New
Zealand. At any one site, pregnancy rates and litter sizes vary both with age of mother and with time
of year. Few rabbits become pregnant before the age of 19 weeks; pregnancy rate increases until the
full adult rate is achieved about 27 weeks old. Litter size is also affected by age, adult litter size being
reached by females at about 43 weeks old. Rates and timing of reproduction vary greatly from site to
site in response to local conditions. The annual production of young per fully adult female is highest
at Wairarapa, N.Z. (53 young) and lowest in the semiarid (17) and subalpine (15) environments. At six
of the sites cohorts of marked rabbits provided estimates of seasonal survival rates; survival improves
with age but becomes relatively constant in rabbits aged more than 24 weeks; survival patterns differ
between sites. Life tables were constructed combining the information on reproduction and survival.
Their possible usefulness is discussed.