During the past decade, in North America, many concepts about moose have changed. Fears that they would be extirpated have been replaced with the know ledge that, when in good habitat, they can withstand heavy hunting pressure. Many of the past estimates of moose numbers and population trends have been guesses, or have been based on information of a subjective nature. In general, very little is actually known about previous moose numbers and fluctuations. Aircraft are now being used extensively to census moose. A transect-line survey method is widely used, however, in Ontario, the results obtained by this method are considered to be too variable to be of value. A system of intensive search of 25-square-mile (65-sq.-km.) plots has now been adopted for use in the province. Results of aerial surveys indicate that densities of 1 moose per 1 or 2 square miles (2.6 or 5.2 sq. km.) are not uncommon for large units of range. The results of studies conducted in British Columbia and Newfoundland have shown that the reproductive rate of moose is quite variable. Three aspects of moose reproduction — breeding and pregnancy rates of yearlings, pregnancy rates of adults, and the occurrence of twins — were found to vary from area to area.