Niche partitioning mechanisms of desert heteromyid rodents
Weeks, Brian Edward
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Desert rodent communities are complex and are important in studies examining community ecology and niche partitioning. Although some reasonable models have been proposed for how desert rodents partition resources, there still remains a paucity of data for explaining niche partitioning in these communities. This thesis explores niche partitioning mechanisms for 4 species of Heteromyid rodents: Dipodomys ordii, Dipodomys merriami, Chaetodipus penicillatus, and Perognathus flavus. Foraging time is examined as a potential niche partitioning mechanism in the Tularosa Basin of south-central New Mexico during 4 June to 27 July 1996. Two unique habitats were chosen in which to place the traps: a mesquite habitat (Prosopsis glandulosa) and a saltbush habitat (Atriplex canescens). Eight replicates of these habitat types were located and spaced greater than 500 m apart. A total of 125 traps equipped with digital timers were placed on each of these replicates and trapped for 4 nights. Foraging patterns were compared for first captures between species by habitat. Differences were found between EL merriami and C penicillatus (P < 0.05) in the mesquite habitat and between D. merriami and P. flavus (P < 0.05) in the saltbush habitat. Seed moisture was examined as a potential niche partitioning mechanism in the Tularosa Basin of south-central New Mexico during 20 April to 2 May, 1996. The study was conducted in a sand sage habitat (Artemisia filifblia). There were two phases to the experiment; a detection phase and a preference phase. In the detection phase, a rosette of six traps spaced 15 m apart were placed in open microhabitats representing experimental units. One of six treatments: (1) wet seeds, (2) dry seeds, (3) wet substrate, (4) dry substrate, (5) wet substrate with seeds, and (6) dry substrate with seeds were placed in each of the traps. There were 145 of these experimental units spaced 100 m apart. In the preference phase an experimental unit was a block with each trap being spaced 0.5 m apart. Treatments were the same for the preference phase. There were 100 blocks each spaced 100 m apart. No pattern in treatment detection or preference arose from these experiments except in those comparisons among treatments containing seeds and those without seeds. These studies were conducted to determine if any separate niche axes exist in desert rodent populations besides the traditional models of microhabitat preference and responses to predation risk. The study involving foraging time patterns suggests that foraging time may be the mechanism by which sympatrics limit competitive interactions. The study involving seed moisture suggests that desert rodents may not be able to detect wet seed versus dry seeds via detection or preference in a field setting. Thus seed moisture may not play a viable role in niche partitioning among desert rodent species.