. Il campo Canadese-naturalista. La figura 3. Parte superiore. Il numero di porta ha offerto un- nually per bounty nei tre Northwestern Ontario distretti; la media mensile precipita- zione e la temperatura media giornaliera per marzo, aprile e maggio in Northwestern Intario, inferiore. Una ripetizione dell'orso dati; medio mensile di nevicata per marzo, aprile e maggio; il novembre nevicata nel nordovest della Ontario. (3) Bounty un bounty sugli orsi è stato stabilito in primo luogo nel Canada superiore nel 1793 da un atto intitolato "un atto a favorire la distruzione di lupi e orsi in diverse parti della provincia". Questo le

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. The Canadian field-naturalist. Figure 3. Top. The number of bears offered an- nually for bounty in the three Northwestern Ontario districts; the average monthly precipita- tion and the average daily temperature for March, April and May in Northwestern Intario, Bottom. A repeat of the bear data; average monthly snowfall for March, April and May; the November snowfall in Northwestern Ontario. (3) Bounty A bounty on bears was first established in Upper Canada in 1793 by an act entitled "An Act to encourage the destroying of wolves and bears in different parts of the province". This legislation was repealed in 1796 and the bounty was not paid again until 1942. In 1961 the bear bounty was dropped and black bears were protected under the Game and Fisheries Act of the Province of Ontario, The use of bounty records as an indication of population size has often been questioned. However, since this is often the only record of population over long periods, investigators of population fluctuations frequently make use of it. There are a few reservations outlined by Keith (1963) that should be considered in each instance of use: fluctuating prices, un- stable socio-economic conditions and the sus- pected practice of bounty hunters of preserving the breeding stock when populations are low. Each of these factors may have a significant effect on the number of bounties collected. We have carefufly considered these reservations and believe that we can make the assumption that change in the number of bears presented for bounty is an indication of population change. around the den. Thirdly, we believe a rapid disappearance of the snow cover in early spring faciUtates feeding by the hungry, adult bears. Spring rainfall is considered to be relevant to this study in Northwestern Ontario. We believe that heavy rain hampers the feeding of the adults and perhaps causes some mortal- ity among the new born cubs. Temperature is perhaps most relevant in faU and spring. In the faU, sno

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