Dynamics of the Arctic Fox Population on St. Lawrence Island, Bering Sea

English abstract: We hypothesized that the arctic fox, Alopex lagopus (Linnaeus), population on St. Lawrence Island was cyclic and that its fluctuations in size. structure, and productivity were correlated with the relative size of the population of northern voles, Microtus oeconomus Pallas, the primary prey. Based on a nine-year study, we determined that the variations in size of the fox and vole populations were similar, but they both were of low amplitude and not closely correlated. The high pregnancy rate (mean, 86%/yr) and numbers of young conceived (mean, 11.5/pregnancy) did not vary significantly among years, probably because of the consistently abundant and diverse food supply available to the foxes. The age composition of the trappers' catch of foxes each winter also was comparatively stable, but it was closely correlated with the size of the vole population in the previous summer. The survival of the young foxes during the summer probably was dependent on the availability of the voles, The composition of the catch also appeared to be influenced by immigration of faxes from the adjacent continents via the pack ice. French abstract: Nous avons émis I'hypothèse que la population du renard arctique, Alopex lagopus (Linnaeus), sur I'île Saint Lawrence était cyclique el que les fluctuations concernant sa tailIe, sa structure et sa productivité étaient corrélées à la taille relative de la population du campagnol nordique. Microtus oeconomus Pallas, sa principale proie. En nous appuyant sur une étude menée sur neuf ans, nous avons déterminé que les variations dans la taille des populations du renard et du campagnol étaient semblables. mais que toutes deux avaient une faible amplitude et n'étaient pas corrélées de façon étroite. Le taux de grossesse élevé (moyenne 86 p. cent/an) et Ie nombre dc petits conçus (moyenne 11,5/grossesse) ne variaient pas de façon significative au cours des ans, probablement à cause de I'abondance et de la variété de sources de nourriture pour les renards. La composition d'âge des prises des trappeurs était également stable d'un hiver à I'autre, mais elle était corrélée de façon étroite avec la taille de la population dc campagnols au cours de I'été précédent. La survie des renardeaux au cours de I'été dépendait probablement de la disponibilité des campagnols. La composition des prises semblait aussi être influencée par I'immigration des renards venant des terres continentales adjacentes par la voie de la banquise.

The Change from Red to White Meat: The Role of Technology

Since 1950, the composition of the U.S. meat diet has shifted markedly from red meats to poultry. For example, from 1970 to 1984, on a percapita basis, beef consumption has declined by 6.4 percent, while chicken and turkey consumptions have increased by 37.9, and 42.5 percent respectively (U.S. Department of Agriculture, 1985). The numerous studies of this phenomenon from the demand side (Chavas, 1983; Braschler, 1983; Nyankori and Miller, 1982; Moschini and Meilke, 1984; Wohlgenant, 1985, Thurman, 1987; Chalfant and Alston, 1988) have failed to achieve a consensus as to whether a change in taste contributed to this shift. One reason for the lack of consensus is that the very large price and quantity changes make it difficult to establish whether consumers are on a new indifference map. But there have been no comparable studies of the nature and causes of the technological change that has made these large consumption and price changes possible. A decrease in the relative price of poultry with respect to red meat is in any case a major explanation of recent shifts in meat consumption patterns. The main reason for such a decrease appears to be a higher rate of technical progress in the poultry industry than in the red meat industry. Substantial productivity gains in both the production and marketing of poultry over the last two decades appears to have been translated into lower retail prices for poultry. Although some productivity gains have taken place in the red meat industry, they have not matched the cost reductions in the poultry industry (Chavas, 1987). Thus, a consumption shift from beef to poultry could possibly be interpreted as a response to changing relative prices, the structural change having occurred in the meat industry. This would imply that, if the beef industry desires to maintain or expand its market, it should seek a decrease in the production and marketing costs of beef.