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Similar to Distribution of Endangered Santa Cruz Kangaroo Rat May Be Limited to Single Park
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Distribution of Endangered Santa Cruz Kangaroo Rat May Be Limited to Single Park
- 1. Current and historical distribu1on of the endemic Santa Cruz kangaroo rat, Dipodomys venustus venustus Deanna Rhoades Ecology & Evolu1on UCSC Undergraduate Abstract Over the last century, the range of the Santa Cruz kangaroo rat (Dipodomys venustus venustus) has contracted and may now be restricted to a single loca1on: Henry Cowell State Park in Felton, California. Although records support a dras1c contrac1on, few surveys have been conducted since 1990. To further the sampling efforts, I gathered records and live-trapped at three poten1al habitats near Felton. My trapping survey found no kangaroo rats. These results, combined with past records, suggest that D. v. venustus may be restricted to Henry Cowell. A comparison of habitats suggests poten1al causes, including reduced habitat size and encroaching residen1al development. An expanded trapping effort would help confirm their ex1rpa1on outside of Henry Cowell and addi1onal analysis of their poten1al habitat may provide insight into management prac1ces. Introduc1on Only in sandhill chaparral, habitat sparse, limited data on current range, possibly only Henry Cowell: D. v. venustus is an endemic subspecies that lives only in sandhill chaparral habitat. Sandhills are a naturally unique and fragmented ecosystem. In the last century, D. v. venustus range has shrunk due to anthropogenic effects. Data on the current range of D. v. venustus is limited, but they may now be restricted to Henry Cowell State Park. Objec1ves Range severely contracted since 1900, limited data on exactly how severe. My study gathered historical data on D. v. venustus and sampled for their current distribu1on. Methods Results Limited intact habitat, Recent records nega1ve, no kangaroo rats captured: Historical Records and Intact Habitat: • Historical records indicate dras1c range contrac1on • Aerial images suggest limited intact habitat Trapping for Presence/Absence: (Table 1.) • No kangaroo rats were captured & no tracks or burrows detected • Two pocket mice (Chaetodipus californicus) caught at Olympia (see photos above) • Ecologically similar rela1ve of D. v. venustus Conclusion Results suggest may only be at Henry Cowell & not limited by just sand and vegeta1on presence: • My sites appeared suitable and nearby Henry Cowell but no D. v. venustus • Suggests factors besides soil and vegeta1on prevented D. v. venustus from persis1ng and/or recolonizing sites outside of Henry Cowell. • Possibly from habitat destruc1on, domes1c cat preda1on, fire suppression, and habitat size reduc1on. • Increased patch distance likely prevented recoloniza1on. Likely local site ex1nc1on, then couldn’t recolonize. Acknowledgements Funding provided by the Kenneth S. Norris Center for Natural History. I am grateful for the instrumental help given by my advisor Gage H. Dayton, graduate student Tina L. Cheng, and members of the SMURF project. I am also thankful for guidance given by sandhill experts, Jodi M. McGraw and Caitlin E. Bean. Made possible by fieldwork assistance from interns and volunteers. Photo by Deanna Rhoades Photo by Jodi M. McGraw Map of records & sandhills Historical records: literature & museum specimens Sandhill GIS data Trapped likely habitat near Henry Cowell Zayante Preserve 300 trap nights Bias Property 287 trap nights Olympia Quarry 280 trap nights Aerial images Site DI Ve CH Ca PE Ca PE Tr NE Fu Zayante 0 0 85 5 1 Bias 0 0 47 5 0 Olympia 0 2 30 55 0 Table 1. Small mammal captures, by species. DI Ve = Dipodomys venustus venustus, CH Ca = Chaetodipus californicus, PE Ca = Peromyscus californicus, PE Tr = Peromyscus truei, NE Fu = Neotoma fuscipes Historical Records and Intact Habitat: I collected historical records & put on sandhill map, then used aerial images & my map to choose 3 poten1al D. v. venustus sites. Trapping for Presence/Absence: Sampled for three nights at each site using Sherman live-traps. Captured animals were iden1fied, marked with ink, and released. Pocket mice; photos by Deanna Rhoades Photo by Deanna Rhoades ! # ! # # # $ ! ! ! ! # # # " " # # ! ! # # $ ! # # # # $ # Esri, HERE, DeLorme, MapmyIndia, © OpenStreetMap contributors, and the GIS user community ± 0 1 2 3 4 5 Miles # Historical Sites $ My 2017 sites ! Captures since '60s ! Failure since '60s " Henry Cowell " Across rd from H. C. Sandhill Soils Sites by type Sites with captures since the 1960s are now empty. Sources: Bean 2003, Biosearch 2014, MVZ collection, CAS collection, Santa Cruz County Information Services Datum: WGS 84 Esri, HERE, DeLorme, MapmyIndia, © OpenStreetMap contributors, and the GIS user community Area Enlarged Dipodomys venustus venustus records, past and present Deanna Rhoades, 2017 Photo by Deanna Rhoades Photo by Deanna Rhoades Photo by Deanna Rhoades Photo by Deanna Rhoades References: Bean 2003; Franco 2012; Grinnell 1922; Kauffman et al. 2015; McGraw 2004; Lee 1994; Roest 1984; Museum of Vertebrate Zoology at Berkeley (MVZ); California Academy of Sciences (CAS)