Academic journal article The American Midland Naturalist

Winter Use of Senescent Herbaceous Plants by White-Tailed Deer in Minnesota

Academic journal article The American Midland Naturalist

Winter Use of Senescent Herbaceous Plants by White-Tailed Deer in Minnesota

Article excerpt

ABSTRACT.-

During winter in northern North America, white-tailed deer (Odocoileus virginianus) have been reported to consume non-woody browse items such as dried leaves (of woody plants), lichens, and evergreen herbaceous plants. We report use of five species of senescent (dead) herbaceous perennial plants in winter by a high density white-tailed deer herd in south-central Minnesota during a winter of average snow depths and below average temperatures. While low in digestible energy, senescent herbaceous material may present deer with a forage item higher in digestible protein than larger diameter woody twigs during periods of nutritional stress.

INTRODUCTION

The winter diet of white-tailed deer in the northern part of its range in North America consists primarily of current-annual-growth of woody twigs, with the remainder composed of green herbaceous plants and ferns and occasionally dried leaves and lichens (Dahlberg and Guettinger, 1956; Snider and Asplund, 1974; Pierce, 1975; Mautz et al, 1976; Mooty, 1976; Crawford, 1982; Verme and Ulrey, 1984; Hodgman and Bowyer, 1985; Dusch et al, 1989; Gray and Servello, 1995). However, in areas of moderate to high deer densities, availability of woody current-annual-growth and other nutritious forages (e.g., evergreen plants and lichens) decreases as winter progresses such that they are often of limited supply by the end of winter. Consequently, to meet minimum daily nutrient requirements, deer must choose between other low quality forage items such as: 1) less preferred woody browse, e.g., alder (Alnus spp.), spruce (Picea spp.) or raspberry (Rubus sp.); 2) older tissues on palatable woody stems that are high in fiber and low in digestible protein (Palo et al, 1992); or 3) plants or plant parts that are readily available but often lower in gross energy and digestibility, e.g., bark, leaf litter, etc. (Amman et al, 1973; Gray and Servello, 1995). Several species of herbaceous perennials present in this region, such as Solidago spp. and Desmodium spp., have relatively tall, rigid stems that can persist after senescence and extend above the snow pack, thus presenting deer with an alternative forage. During years of high deer densities, winter use of senescent forbs, apparently during the period between snow-melt and spring green-up, has been observed several times in the 1990s in south-central Minnesota, including at Cedar Creek Natural History Area and the Twin Cities Army Ammunition Plant (TCAAP; P.A. Jordan, pers. obs.). Significant winter use of senescent herbaceous plants, however, has never been adequately documented. Our objective was to describe the winter use of senescent forbs by white-tailed deer at TCAAP.

STUDY AREA

The TCAAP (45°05'38''N, 93°10'04''W) is a 1025 ha tract completely enclosed by 2-m tall fencing with restricted access (i^DeGayner and Jordan, 1987 for full description of TCAAP). Approximately 500 ha of this land is considered habitable by deer; roughly 50% is comprised of open grasslands, oak ( Quercus spp.) savannas, and old fields, with die remainder comprised of lowland shrub interspersed with hardwoods (quaking aspen Populus tremuloides, Cottonwood Populus deltoides, American hazel Corylus americana and willow Salix spp.) , white spruce (Picea glauca) and red pine (Pinus resinosa) plantations, a cattail (Typha spp.) dominated wetland of about 60 ha and two small lakes (Baggot et al, 1988). Most of the undeveloped land is formed of well-drained soils of glacial till origin. Mean temperatures at the Minneapolis International Airport were -1.7 C below average during the winter of 1995- 96. Mean daily snow depth at the Minneapolis International Airport was above average in Dec. 1995 and Jan. 1996, but below average in Feb. and Mar. 1996.

Early winter deer densities within TCAAP were estimated by standard helicopter counts for 1993, 1994 and 1995 to be 17.4, 23.9 and 11.4 deer/km^sup 2^, respectively. During each of those same winters, 33, 100 and 30 deer, respectively, were removed by sharpshooting between Nov. …

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