O ne of the most dramatic changes that has occurred in forests of eastern North America during the twentieth century is the increase in the dominance of red maple (Acer rubrum L.; Lorimer 1984, Abrams 1992). Red maple has become nearly ubiquitous across sites of widely varying light, moisture, and nutrient availability. This distribution is in stark contrast to the limited distribution of red maple reported in pre-European settlement forests, where it occurred mainly in poorly drained areas. Red maple has increased after a wide range of disturbances and as a late successional species in many forest types. It now dominates the understory and mid-canopy of many oak (Quercus), pine (Pinus), and northern hardwood forests; moreover, it will probably continue to increase in dominance in the overstory during the next century, causing widespread replacement of the historically dominant trees of the forests of the eastern United States. Surprisingly, red maple exhibits rather modest levels of leaf physiological responses (e.g., gas exchange and osmotic adjustment) to various environmental conditions and has leaf structural characteristics and nitrogen levels that are not particularly conducive to a robust leaf physi-

The red maple paradox: What explains the widespread expansion of red maple in eastern forests?

A variety of nut-producing plants have mutualistic seed-dispersal interactions with animals (rodents and corvids) that scatter hoard their nuts in the soil. The goals of this review are to summarize the widespread horticultural, botanical, and ecological literature pertaining to nut dispersal inJuglans, Carya, Quercus, Fagus, Castanae, Castanopsis, Lithocarpus, Corylus, Aesculus, andPrunus; to examine the evolutionary histories of these mutualistic interactions; and to identify the traits of nut-bearing plants and nut-dispersing rodents and jays that influence the success of the mutualism. These interactions appear to have originated as early as the Paleocene, about 60 million years ago. Most nuts appear to have evolved from ancestors with wind-dispersed seeds, but the ancestral form of dispersal in almonds (Prunus spp.) was by frugivorous animals that ingested fruit.

The evolutionary ecology of nut dispersal

I used a 14-year dataset on dynamics of mast-consuming rodents from an eastern deciduous forest to determine the relationship between population fluctuations of white-footed mice ( Peromyscus leucopus ), deer mice ( P. maniculatus ), and eastern chipmunks ( Tamias stria-tus ) and production of acorn mast. Mast (acorn) production was episodic with four excellent crops produced in 14 years. Densities of rodents in summer ranged from 3 to 103 animals/ha and correlated positively with production of mast the previous autumn (all r 2 > 0.56). During years of high production of mast, stores of acorn lasted throughout winter, whereas in most years, acorns were gone by January. During years of high production of mast, mice bred all winter, which resulted in high densities the following summer. Episodic production of mast and resulting fluctuations in consumers of mast have implications for the predator-satiation hypothesis and other community processes.

Population Fluctuations of Mast-Eating Rodents Are Correlated with Production of Acorns

White-tailed deer (Odocoileus virginianus) exhibited seasonal rhythms in heart rates, activities, and metabolism, with the lowest ecological metabolism occurring in the winter and highest in the summer. This rhythm is an adaptation for energy conservation; resource needs are lower when range resources are reduced. A series of equations is used to estimate ecological metabolism and forage consumption from measured heart rates and activity patterns throughout the year. The highest energy expenditure (about 4 times baseline metabolism) is estimated for a female with 2 fawns during the lactation period, and the lowest (about 1.5 times baseline metabolism) for deer in midwinter. As metabolism rises in March and April, the intake of dormant forage should also rise until more digestible spring growth is available. The timing of the arrival of spring seems to be an important factor in population dynamics, with its effect being most pronounced 2 years later when the fawns should become members of the breeding population. J. WILDL. MANAGE. 42(4):715-738 The free-ranging animal presents several acute problems for the physiological ecologist interested in quantifying the animal's "cost of living" over the annual cycle. Knowledge of this cost is fundamental to an understanding of productivity, for an animal can be productive only if the range supplies nutrients in excess of the level necessary for maintenance. There is ample evidence for this in the literature; it is well known that deer on overstocked range are smaller in size, have fewer fawns, and have smaller antlers than those on range that is properly stocked. Difficulties in the direct measurement of the metabolism of free-ranging animals are sufficiently great to compel one to seek alternate methods of estimation. This paper presents a method for predicting ecological metabolism (Moen 1973) and forage intake of white-tailed deer based on equations derived from several years of physiological telemetry measurements at the Wildlife Ecology Laboratory, Cornell University, and additional data from the literature. Funds for this research have been provided by the New York State Department f Environmental Conservation through Pittman-Robertson Project W-124-R and the N.Y. State College of Agriculture and Life Sciences, Cornell University. Special thanks are due Anne Hiller and Barbara Buxton for their part in the training and measurements on experimental deer, Joanne Paul for summarizing data, and Elyse Egan for verifying each of the equatio s. I wish to recognize Helenette Silv r for her pioneering work on the metabolism of white-tailed deer in the 1950's which served as an important foundation for my research in the 60's and 70's.

https://www.jstor.org/stable/pdfplus/3800763.pdf

Seasonal Changes in Heart Rates, Activity, Metabolism, and Forage Intake of White-Tailed Deer

Summary

(1) The savanna ungulate faunas of the North American Miocene were broadly similar to those of present-day East Africa in terms of overall morphological and taxonomic diversity. However, the predominant ungulates of the African faunas are bovids, which possess bony horns that are primitively sexually dimorphic in their occurrence. The predominant ungulates of the North American Tertiary were equids, camelids and oreodonts, which all lacked horns. A limited number of horned ruminants were present, but these were largely Miocene immigrants from Eurasia. Horns were also absent from the large-bodied herbivores in the endemic faunas of South America and Australia.



(2) The absence of horns in equids and tylopod artiodactyls is unlikely to be due to genetic insufficiency. Bony horns were present in brontotheres, which were closely related to equids, and in protoceratids, which were closely related to camelids. Nasal horns were present in one oreodont genus.



(3) Studies on living ungulates show that a strong correlation exists between habitat type, feeding behaviour, social behaviour and morphology. It is possible to use the morphological remains of extinct ungulates to reconstruct the types of feeding and social behaviour, and to use the distribution of morphologies and body sizes in a community of mammals, in conjunction with geological and paleobotanical evidence, to reconstruct the type of habitat.



(4) The importance of the post-Eocene climatic changes to the history of mammalian evolution is stressed. Continents at higher latitudes have become increasingly seasonal in terms of temperature and rainfall since the equable global conditions of the early Tertiary. Savanna mosaic were the predominant biome in North America by the early Miocene, and in Eurasia by the middle Miocene. Living temperate-latitude species of ungulates may not be a reliable guide for the assessment of the interrelationship between behaviour and morphology in an evolutionary perspective, as their behaviour may have been recently adapted to a habitat type that has only been in existence since the Pleistocene.



(5) The primitive condition in eupecorans and protoceratids is the absence of horns, with the presence of large sabre-like canines in the males. The first horned members of these divisions had horns in the males only. Small present-day antelope, where horns may also be present in the females of the species, are probably secondarily small.



(6) Horns were acquired independently in ruminant artiodactyls at least three times, and a maximum number of seven times is not unlikely. In each case, horns first appeared at a critical body weight of about 18 kg, and in correlation with a change in habitat from closed to open woodland.



(7) Horns in living ruminants are associated with territorial defence by males holding exclusive feeding and reproductive territories in woodland habitats. Such behaviour in present-day antelope is correlated with a body size of greater than 15 kg and a folivorous diet. It is argued that horns evolved in ruminant artiodactyls on the adoption of this type of territorial behaviour once the critical combination of body size, diet and habitat type had been attained in their evolution from small, essentially frugivorous, forest-dwelling animals.



(8) Perissodactyls never evolved sexually dimorphic bony horns of the type seen in ruminant artiodactyls. This is because their foraging and digestive strategies necessitate a larger daily intake of food. In a woodland habitat they were never able to adopt a feeding area small enough to make exclusive territory maintenance an economical proposition. Territory holding in male perissodactyls is seen, but under the opposite conditions of habitat to territorial behaviour in ruminant artiodactyls.



(9) Study of the morphology and paleoecology of oreodonts suggests that they were woodland herd-forming browsers with exclusively folivorous diets. They probably had some forestomach fermentation, but did not chew the cud. Similar studies of Tertiary camelids suggest that they were predominantly selective browsers eating herbage at a low level in open country and formed mixed-sex feeding groups. These combinations of feeding and social behaviour suggest a more open structure of the mid-Tertiary habitat in North America than in Eurasia.



(10) Studies of the behaviour and morphology of living members of the Ruminantia, and of the morphology and paleoecology of their fossil ancestors, suggest that they were primitively tree browsers living in closed woodland habitats. Such habitats were abundant in the Old World, but in limited supply in North America during the Oligocene, where the protoceratids were the only ungulates to parallel the eupecoran type of feeding and social behaviour. South America appears to have had an even more open habitat in the Oligocene than North America, and no parallel to the eupecorans was seen amongst the indigenous ungulates. The radiation of the Bovidae into open grassy habitats in the Pliocene may have been dependent on the immigration of grazing equids into the Old World.



(11) I conclude that there was a difference in habitat structure between North America and the Old World during the Tertiary. The food resources in North America were more widely dispersed, and this may have been the result of the trees being more widely spaced. A possible causal mechanism for this was the stable land mass of the North American continent during the Tertiary, resulting in a more continental climate, with a more severe effect of the post-Eocene seasonality on the vegetation. The faunal record of the two continents also implied a greater density of trees in the Old World.



(12) Thus most endemic North American ruminants did not evolve horns because, at the critical combination of body size and diet seen in the evolution of horns in the Old World ruminants, the dispersal of the food resources within the vegetation was too great for an effective home range to be maintained as an exclusive territory.



(13) Attention is drawn to the dangers of constructing evolutionary stories about living animals without primary reference to the fossil record to see if the hypotheses are upheld, and of assuming that fossil animal communities can be made to fit models of existing communities.

Evolution of horns in ungulates: ecology and paleoecology

Rumen contents of white-tailed deer (Odocoileus virginianus) during November and early December of 1966 through 1973 in a mountainous area of southwestern Virginia revealed that acorns made up an average of 76 percent by volume of the deer's diet when acorns were abundant. When a mast failure occurred, deer replaced acorns with large amounts of the leaves of prostrate evergreen plants and shrubs and mushrooms. Proximate analysis of rumen contents revealed that diets containing acorns were higher in nitrogen-free extract and crude fat and lower in mineral content. In mast-free diets both mineral matter and protein increased. Proximate analysis and in vitro tests of composite diets indicated that when mast was present the diets were more digestible and were higher in fat and soluble carbohydrates. A relatively low value of 1.5 kcal/g for estimated digestible energy in mast-free diets suggests that when deer must rely on this type of diet during the winter season, their energy requirement for maintenance may not be met. The addition of oak mast to winter diets increased estimated digestible energy to 3.1 kcal/g, or a level adequate to meet the maintenance energy requirement. A forage inventory in the major forest types indicated that mature stands of pitch pine-bear oak (Pinus rigida-Quercus ilicifolia) produced the greatest quantity of important staple foods for deer during late fall and early winter. J. WILDL. MANAGE. 39(2):330-336 Oak mast predominates in the fall and winter diets of white-tailed deer wherever and whenever it is abundant in the Southeast (Ruff 1938, Pearson 1943, Pearson and Burnett 1940, Harlow 1961, Harlow and Hooper 1971). Acorns are often available to deer for eight months or more (Goodrum 1959). They are high in carbohydrates (King and McClure 1944, Morrison 1957) and provide energy and nutrients during the winter. During years of oak mast scarcity deer must turn to other forages. In this study, data from 1966 through 1973 are used to compare the effects of oak mast abundance and scarcity in late November on food selectivity patterns of deer. Nutritional values of rumen samples and of composite diets reconstructed from rumen analysis were estimated. Important forages available to deer were inventoried in the major forest types of the study area. DESCRIPTION OF THE STUDY AREA The Broad Run Wildlife Research Area in Craig County, Virginia, is within the Ridge and Valley Province. The soils are derived from shale, sandstone, and conglomerate bedrock. Thirty-five percent of the approximately 3,035-ha area is composed of the pitch pine-bear oak forest cover type; 33 percent, oak-hickory-yellowpoplar-white pine (Quercus spp.-Carya spp.-Liriodendron tulipifera-P. strobus) type; and 19 percent, mixed oak-pine type (Whelan 1962). Site indexes (the height which upland oaks attain in 50 years [Olson 1959]) range from 35 to 60 with pitch pine-bear oak containing the lowest index. Elevations range from 469 to 689 m above sea level. Slopes range from 0 to 58 percent and face primarily northwest. From 1959 to 1964, approximately 389 ha (12 percent of the study area) were dis330 J. Wildl. Manage. 39(2):1975 This content downloaded from 207.46.13.149 on Mon, 03 Oct 2016 04:08:45 UTC All use subject to http://about.jstor.org/terms DEER FOODS AND OAK MAST AVAILABILITY * Harlow et al. 331 turbed by clearcutting and heavy selection cutting. In 1957, 23 wildlife clearings were established which ranged in size from 0.30 to 1.33 ha. Seneca (1961) estimated 120 deer on the study area, or 1 per 27 ha. Hunter observation and annual kill statistics indicate little change in deer numbers since 1961 (Weekes 1974).

Deer Foods during Years of Oak Mast Abundance and Scarcity

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Deer Foods during Years of Oak Mast Abundance and Scarcity