Title: Litter Size and Latitude in North American Mammals
Abstract: The phenomenon of fluctuations of mammal populations in the higher latitudes of the northern hemisphere is well known. Clearly, population changes of such magnitudes are evidence that large mortality rates are being experienced by these species. Because such large fluctuations in populations seldom occur in the lower latitudes, it seems apparent that species in these latitudes may not often experience the large mortality rates of closely allied species to the north. The principle of inversity as expressed by Errington (1946) and others, seems to imply that the species of the high latitudes experiencing the high mortality rates will have correspondingly high reproductive rates to help compensate for their losses. Because the breeding season in the north is shorter than that in more southern latitudes, there is less opportunity for increasing reproduction by way of more litters during the season than there is by an increase in the litter size. Therefore, the average litter size of mammals of the same or closely related species should increase with an increase in latitude. Rowan and Keith (1956) for the snowshoe hare and Burns and Burns (1957) for the opossum have shown that such an increase does occur. Moore (in press) has also shown the effect of climate on reproduction in the tree 'squirrels of the world. To determine if this phenomenon was evident in other mammals a search was made of the literature concerning litter size of mammals of North America.
Publication Year: 1960
Publication Date: 1960-10-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 136
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