Forage Selection and Grouping Patterns of Male and Female Scimitar-horned Oryx (Oryx dammah) on Mason Mountain Wildlife Management Area, Mason, Texas

Abstract

Little is known about resource selection patterns of scimitarhorned oryx (Oryx dammaty in Texas, information that is vital for informed management decisions. Scimitar-horned oiyx are less dimorphic in body size (males approximately 12% larger than females) than most ruminants (males 20 - 50% larger than females). Ruminants dimorphic in body size display intersexual differences in diet and spatial patterns, presumably because of body size differences. Consequently, scimitar-horned oryx is an ideal species to test for intersexual differences in spatial patterns, diet and food selection. I hypothesized that male and female scimitar-homed oiyx associate in mixed-sex groups and do not exhibit intersexual differences in forage selection. My study was initiated in June 2006 at Mason Mountain Wildlife Management Area in central Texas and data collection was completed in April 2007. I measured grouping patterns from systematic vehicle surveys conducted at dawn and evening in six different months. I observed males and femalesthrough binoculars and collected fecal samples from known sex individuals in six different months. I determined food habits by identifying plant fragments in fecal samples. Forage availability was measured seasonally by establishing 100 m transects in areas where fecal samples were collected. Mixed-sex groups were encountered more commonly than other group types and most males and females encountered (> 0.69) were in mixed-sex groups. There were no differences between the diet of males and females. Scimitar-horned oryx displayed differences among months in forage selection. In summer and fall, there was an inverse correlation between availability and use of food items. In winter there was a positive correlation and no correlation between availability and use of food items in spring. The majority of the diet was grasses, such as Sporobolus sp., Eragrostis sp., and forbs. The findings of this study support expectations based on body size, males and females occur in the same groups and consume similar forages. Unlike many ruminants, managers do not have to consider separate habitat requirements of each sex when managing scimitar-horned oryx.