College - Author 1
College of Science and Mathematics
Department - Author 1
Biological Sciences Department
Degree Name - Author 1
BS in Biological Sciences
Francis Villablanca, College of Science and Mathematics, Biological Sciences Department
Lompoc kangaroo rats (LKR, Dipodomys heermanni arenae) are small rodents that reside in sand dunes from Pismo to Orcutt, including the Oceano Dunes State Vehicular Recreation Area (SVRA), in Oceano, CA. In the SVRA, some of these individuals live in habitat islands, which are habitat fragments of dense vegetation disrupted by empty, bare sand in between them. Recreational vehicle activity is permitted in the Oceano Dunes, which has caused persistence habitat fragmentation. Kangaroo rats are known to disperse between habitat islands and are suspected to do so via a special type of dispersal: cryptic dispersal. This dispersal mode, if it occurs in LKR, should be recognizable because first captures of new individuals should not be juveniles, but should be older.
I wanted to see if these LKR do indeed display cryptic dispersal and establish home ranges, despite the anthropogenic habitat fragmentation. Data was collected through quarterly, live trapping sessions, which occurred over a three-day period every three months, and covers multiple years. Individuals were ear-tagged and cataloged into a database. The information gathered from these trappings were used to test my hypotheses. I ran a variety of statistical analyses (t-tests, chi-squares, contingency table) and discovered interesting outcomes.
Heavier, more mature (non-juvenile) male kangaroo rats were commonly trapped as new individuals (i.e., first captures). There was a lack of evidence supporting or refuting a pattern of cryptic dispersal for females. When conducting chi-squares, significance was detected via a disproportionately high subadult new capture (non-juvenile) and recaptures disproportionately attributed to adults. Both of these results reinforce an inference of cryptic dispersal.
I also utilized the dataset to construct visuals to see if movement patterns were present. These visuals enlightened me on age-related time and pattern of movement. For example, new juvenile captures were highest in June, which could reflect seasonal reproduction. Adults were caught most frequently in December which might be the time that they would be fully mature. The lack of new juveniles trapped also backs up cryptic dispersal. The other visuals displayed how kangaroo rats typically stay on one habitat island and do not move to others. The few that did disperse provided interesting contrasts. Subadults did not disperse far distances and went back and forth between islands. Adults dispersed further and more directly; they did not “hop” to and from islands. Collectively, this information helps inform kangaroo rat movement and seemed to support my hypotheses.