We have questioned or explained conflicting reports and conclude that the breeding habits of Canadian chipmunks are essentially similar to those described by some U.S. Although the young attain adult size and dentition in 3 months, most do not breed until 11 months old. Litter sizes from embryo and scar counts averaged 4.8 and 4.9. Young have emerged in four consecutive Septembers at Stanley Corners, Ontario. Spring breeding is probably annual and ubiquitous but records are too few to reveal the local frequency of summer breeding. These occur over much of the Canadian range, with distinct waves of young appearing above ground in June and September. As females can breed in MarchвЂ“April and (or) JuneвЂ“July, eastern chipmunks are unique among hibernating sciurids in that they have two breeding seasons per year. Most adult males are in breeding condition (with large testes in black scrotal sacs and macroscopic tubules in caudae epididymidon) from March to June. Schedules of the major stages of reproduction and growth are summarized graphically. Reproductive, age, and body-size data from 1403 museum specimens from Manitoba to Nova Scotia and data on live chipmunks studied in the field in southeastern Ontario were analyzed.

Canadian pitfall trap