Diet Composition, Resource Availability, and Food Preferences of New England Cottontail on Cape Cod, Massachusetts

Abstract

Habitat management efforts for the New England cottontail, a species of conservation concern, are primarily focused on creating and maintaining dense understory vegetation. Native shrublands and forest types on Cape Cod provide large expanses of potential habitat for New England cottontail, but populations remain low in many of these areas. To improve understanding of the habitat requirements for this threatened species, I explored the diet composition of New England cottontail on Cape Cod, surveyed available forage resources, and determined food preferences within scrub oak shrublands and other utilized vegetation types. I hypothesized that while dense scrub oak shrublands may provide excellent protective cover, food species preferred by New England cottontail are not limited to this habitat type and may be found in greater abundance within openings and along the edges of this vegetation community.

To analyze food preferences of the New England cottontail on Cape Cod, I compared diet composition with resource availability. Diet composition was determined using microhistological analysis of fecal pellets collected during previous habitat occupancy surveys. A subset of diet composition data from six pellet collection sites was combined with resource availability sampling and browse observations at these sites to evaluate food preferences. The relative availability of food resources for New England cottontail was determined through intensive vegetation sampling that counted the total number of available stems of each species within randomly stratified sampling plots at pellet collection sites. A modified Johnson’s rank preference index was calculated that compared the relative use of different plant species by New England cottontail, represented by the relative percentages of different plants in the diet, with the relative abundance of different plant species available in occupied habitat. Geographic analysis provided further information regarding how past disturbances and the implementation and timing of land management practices may relate to the availability of preferred food, vegetation structure, and New England cottontail utilization.

At least 50 genera of plants comprised the diet of New England cottontail on Cape Cod, with native ericaceous shrubs comprising the largest portion of the diet. Preferred foods included native trees, shrubs, and vines, such as aspen (Populus), dewberry (Rubus), hawthorne (Crataegus), grape (Vitis), birch (Betula), maple (Acer), holly (Ilex), huckleberry (Gaylussacia), pine (Pinus), and wintergreen (Gaultheria). In addition, several grass species are preferred including Poa, Panicum, Bromus, Agrostis, Festuca, and Andropogon. The habitat analysis showed that a wider range of preferred food species were available where there was more variation in habitat structure and disturbance history. I concluded that in areas where there is large expanses of existing native shrublands, the availability of preferred forage may play a role in successful habitat restoration. By incorporating information about preferred food resources into the planning process for habitat management projects, prescriptions for prescribed fires and timber harvests can be adjusted to improve the success of these efforts in maintaining or restoring habitat. Land management that increases the accessibility of preferred foods within existing native shrublands may enhance opportunities to assist in the conservation of viable populations of New England cottontail on Cape Cod.