Optimality models of food selection by herbivores assume that individuals are capable of assessing forage value, either directly through the currency used in the model or indirectly through other variables correlated with the currency. Although energy and protein are the two currencies most often used, controversy exists regarding their respective influence on food choice. Part of the debate is due to the difficulty of teasing apart these two nutrients, which are closely correlated in most natural forages. Here we offer a test of the assumption that energy and protein contents of the forage are both currencies that large mammalian herbivores can use when selecting their food. We observed feeding behavior of 47 wild white-tailed deer (Odocoileusvirginianus) during winter while individuals were presented with four experimental foods representing two levels of energy and protein (dry matter digestibility: 40-50%; crude protein: 12-16%). Using experimental foods allowed us to separate the influences of energy and protein and clearly distinguish between the roles of these two nutrients. Deer discriminated between foods through partial selection, and selected diets higher in energy but lower in protein. The observed choices appeared consistent with physiological needs of deer wintering at the study site, where digestible energy was in short supply in the natural environment while protein was probably not. Results are in good agreement with recent findings on domesticated ruminants. They support a basic assumption of optimality models of food selection that use energy and/or protein as a currency, although the physiological mechanisms behind the food selection process remain unclear. We urge students of food selection by herbivores to replicate our experiment with other foods and/or in other circumstances before more general conclusions are drawn.

In field investigations on the relative resistance of varieties of peas, Pisum sativum L., to the pea aphid, Acyrthosiphon pisum (Harr.), the average number of aphids per terminal growth for 13 years (Maltais, 1937, 1950, 1951, and unpublished technical report, 1950-54) for six varieties was as follows: Perfection, 39.6; Daisy, 32.6; Lincoln, 35.6; Laurier (H-103), 9.8; Champion of England, 11.8; and Melting Sugar, 16.8. In a preliminary investigation by Auclair and Maltais (1950), 11 free amino acids were detected in pea plant extracts by paper chromatography. From a visual comparison of chromatograms, the variety Perfection appeared to contain a higher concentration of most free amino acids than the variety Laurier. This is a report on the quantitative estimation of the free and total amino acid contents of the three susceptible varieties (Perfection, Daisy, and Lincoln) and the three resistant varieties (Laurier, Champion of England, and Melting Sugar) by the method of paper chromatography.

We examined published historical information, reports on aerial surveys conducted since 1953, and harvest data collected since 1971 to describe changes in the distribution and abundance of Caribou (Rangifer tarandus) in Québec. The southern limit of the Caribou distribution diminished considerably in the late 19 th century, and the decline in numbers probably continued until the 1960s and 1970s east of the 62 nd meridian. South of the 49 th parallel, only four small populations still persist. Despite the fact that all Caribou of the province were assigned to the same sub-species (R. t. caribou), three ecotypes with specific habitats and behaviour are found. The Barren-Ground ecotype, the only migratory form, is found north of the 52 nd parallel. This ecotype currently occupies ≈ 255 000 km 2 in fall and winter, mainly in the ecological subzones of the forest tundra and the taiga. The Barren-Ground Caribou was characterized by a very low abundance from the end of the 19 th century until the mid1950s, but increased markedly thereafter reaching over a million individuals at the beginning of the 1990s. Populations of the Mountain ecotype have been identified in the southeastern and, possibly, in the northeastern parts of the province. The latter Mountain population is virtually unknown. The southeastern population is sedentary and uses mainly the boreal forest. This population has decreased over the last century and currently numbers only ≈ 140 individuals. Finally, the Forest-Dwelling ecotype is found discontinuously, mainly between the 49 th and 55 th parallels. Its current distribution covers ≈ 235 000 km 2 , mainly east of the 72 nd meridian. This sedentary ecotype is found almost exclusively in the boreal forest, principally in areas with long forest fire cycles. Its abundance has also decreased over the years. Large Forest-Dwelling populations still persisted during the 1950s and 1960s, but they apparently disappeared. The current abundance is not known precisely, but based on density estimates and considering the current distribution, it probably does not exceed 3000 individuals. Current data are insufficient to identify precisely the causes of the population decline, although hunting seems to be an important proximal cause. L'abondance actuelle n'est pas connue mais elle pourrait difficilement dépasser 3000 individus si l'on se base sur les estimations de la densité et de l'aire de répartition. Les données disponibles sont insuffisantes pour identifier les causes exactes des diminutions d'effectifs bien que la chasse semble une cause proximale importante.

Differences in resistance of varieties of peas to the pea aphid, Acyrthosiphon pisum (Harr.), have long ago been shown in the field and bv controlled rearings under glass, Russell and ilforrison (1924, p. 63) apparentl) being the First to observe differences. Trjrly investiprinns at Wisconsin by Searb ( 1932) showed that pea varieties differ in the number of aphids horn upon tl~ern. R~Ialtais ( 1937) corraborated these early findings and reported ( 1950) the development of a pure-line strain of apkrd-resistant pea. The influence of resistance in peas upoil aphid development, reproduction, and l o n g e v i~ was investigated by Harrington ( 1941 ) with individual plants under controlled conditions in the greenhouse. His results confirnled the jnabilitrr of the insect to develop and reproduce as fast on a resistant plant as on a susceptible one. Tt has been postulated that the composition of the available food in the host plant plays possibly the most important role in determining the resistance to aphid ittack (Evans, 1938;Painter, 1941). Maltais (1948), Auclair and !\laltais (1 9.701, and Alnltais (1951) gave preliminary reports on the probable factors in varietal resistance in peas.This is a report on the determination of total nitrogen, soluble nitrosen, and sugar contents of three susceptible varieties (Perfection, Daim-, and Lincoln) and three resistant varieties (Laurier, Champion of England, and Melting Sugar) of cultivated peas (Pisum sativum L.). Results of aphid population counts in the field (Maltais, 1937(Maltais, , 1950(Maltais, , 1951(Maltais, , and unpublished technical report, 19.50-1954 for a period of 13 years gave the following average number of aphids per plant sample for each variety: Perfection, 39.6; Ilaisy, 32.6; Lincoln, 3 5.0; Laurier (H-103), 9.8; Champion of England, 1 1.8; ~\+Ielting Sugar, 16.8. MethodsThe plot system adopted for the growing of the pea varieties in the field was the latin square. Each plat was 15 feet long with four rows 24 inches apart. T h e plocs 11-ere separated in all directions by a space 48 inches wide.T h e seed, treated liglltlv ~v i t h Spergon (zetrachloro-pamhenzoquinone) was sown between 114ay I r a d 20. A light application of 2-12-6 fertilizer was made on tlie surface of the rows afcer seeding. T h e peas were also grown in the greenhouse, n-here the seed was treated with Spergon and placed in wet sand for germination. After one week, in earlv Februarv, rile well-developed and healthy seedlings wwe placed in loamy soif in &inch flower pots. Observations on growth were made periodicallv and plmt samples were coUected for analysis at the beginning of April. The &ages of plant growth (Table I) were established by counting the internodes of whole plants collected at random at replar intervals, the terminal bud heins counted as the first internode. Uninfested plant samples, collected from the field and the greenhouse, consisted of the temzinal growth, from the terminal bud down to the base of the fourth internode; and of the middle growth, from the fi...

The influence of varietal differences in plants on infestation by aphids has received considerable attention in control studies. Painter (14), in 1941, concluded that the composition of the available food in the host plant plays possibly the most important role in determining the relative resistance to aphid attacks. In biological studies on Aphis rumicis L., Davidson (8) found that factors that influence the physiological activity of the plant affect also the progress of aphid infestation. The same author (6) also pointed out that aphids exhibit a wide range of fecundity on different hosts. “The sap of certain varieties of beans”, writes Davidson, “appears to have a direct inhibiting effect upon the reproductive capacity of the aphids, whereas that of other varieties seems to have the opposite effect.”