Relative habitat- and browse-use of native desert mule deer and exotic oryx in the greater San Andres Mountains, New Mexico

Abstract

Introduced oryx (Oryx gazella gazella) have expanded into the San Andres Mountains of south-central New Mexico, but little is known of concurrent habitat used by oryx and desert mule deer (Odocoileus hemionus crooki); the latter in New Mexico is a species of special concern that has declined signifi cantly since the introduction of oryx. We used fecal-pellet and browse surveys in combination with presence modeling to identify differences in relative use of habitat types, distribution, and browsing of highly palatable, highly preferred (hereafter, key) plant species during 2004 to 2006 to assess the potential for direct competition in use of resources in the San Andres Mountains. Numbers of pellet groups per transect (hereafter referred to as relative use) of oryx was greatest in sandsage (Artemisia fi lifolia) shrublands and alkali sacaton (Sporobolus airoides) grasslands, whereas mule deer-use was greatest in oak- (Quercus spp.) mountain mahogany (Cercocarpus montanus) shrublands, and pinyon- (Pinus edulis) juniper (Juniperus spp.) woodlands. Use of key mule deer browse species was low (<4.0% of current annual growth browsed) in all habitat types. Relative use of oryx accounted for 42% of the variation in browse percentages in pinyon-juniper woodlands and 58% of the variation in mesquite (Prosopis glandulosa) shrublands, whereas mule deer-use accounted for 79% of the variation in oak-mountain mahogany shrublands and 27% in pinyon-juniper woodlands. Presence models similarly indicated that deer distribution was most positively associated with oak-mountain mahogany shrublands and pinyon-juniper woodlands, while oryx distribution was most positively associated with alkali sacaton grasslands, mixed lowland scrub, and sandsage shrublands. Presence models also indicated that areas closer to roads were positively associated with presence of mule deer and oryx, as were southern aspects for oryx and higher elevations for mule deer. Relationships with roads were likely driven by other attributes (e.g., water sources, arroyos, and canyons) associated with these areas in the San Andres Mountains. Current management strategies aimed at limiting oryx numbers in woodland and shrubland habitat types located in mountainous areas of the San Andres Mountains that show highest use by mule deer should continue to aide in recovery of mule deer populations.