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Developing the Relationship between Relative and Actual Abundance to Estimate Population Size of the Relict Leopard Frog
Rebeca Rivera and Jef R. JaegerSchool of Life Sciences, University of Nevada, Las Vegas
Colorado River Terrestrial and Riparian Meeting 2014, January 28-30
Background Known Historical Locations
1990s Frogs known from 3 areas
2001 Frogs known at only two areas
~ 1100 adults
2002 Petitioned for listing under ESA
From Bradford, Jaeger, & Jennings 2004
Monitor populations
Establish additional populations in existing or created habitat
Voluntary Conservation Agreement and Strategy
ESA Listing Revisited
2011 USFWS submitted a MDL plan
2016 Review of Relict Leopard Frog status
Population size
Conservation Agreement and Strategy
Sites: ~ 6 historical 11 Extant Experimental
Upper & Lower Blue Point
Rogers
Black Canyon Sprs.
Bighorn Sheep
Salt Cedar
Historical Experimental Failed Experimental
Boy Scout & Dawn’s
Tassi Pupfish Refuge Goldstrike
Sugarloaf
Red Rock
Grapevine, NV
Perkins Pond
Lime
Bearpaw
Quail
Grapevine, AZ
Horse
Wetland Park
Union Pass
Double Sampling Technique Calibrate indices of relative abundance by finding the
relationship between 2 survey methods
Relative abundances from Visual Encounter Surveys (VES)
Estimates of true abundance from Mark-recapture Provides ratio estimates Applied to sites where only VES data is available
YEst=XMR Est
XRA
YRA
Ratio Estimate
( )Relative Abundance
PopulationEstimate
Sampling Conducted efforts during Fall 2011 and Spring 2012
Visual encounter surveys at all sites
Mark‐recapture sampling at 5 sites
Ratio estimates from 4 sites
Upper & Lower Blue Point
Rogers
Black Canyon Sprs.
Bighorn Sheep
Salt Cedar
Historical
Experimental
Boy Scout & Dawn’s
Tassi Pupfish Refuge
Goldstrike
Red Rock
Perkins Pond
Lime
Bearpaw
Quail
Grapevine, AZ
Horse
Union Pass
Occurred at night
Mark-recapture
Multiple site visits/events
(Schnabel approach)
2-5 surveyors using floodlights
PIT tags adult frogs (≥ 45mm SVL)
VES
Count observed frogs
2-3 surveyors using floodlights
Sampling
Red Rock Spring
Ratio EstimatesRed Rock Spring
Relative abundance of adults during sampling events
Fall 2011 Spring 2012
Period Marked N 95% CI CV(N) Average Ratio Estimate
Fall 2011 17 17.5 17.0-22.7 0.055 1.27 (1.23-1.64)
Spring 2012 18 18.6 18.1-24.3 0.058 1.49 (1.45-1.94)
Rel
ativ
e ab
un
dan
ce
Mark-recapture estimates
0
5
10
15
20
Sampling Events
Pupfish Refuge Spring
Ratio Estimates
Period Marked N 95% CI CV(N) Average Ratio Estimate
Spring 2012 66 67.9 66.4-75.2 0.027 2.31 (2.26-2.56)
Rel
ativ
e ab
un
dan
ce
Mark-recapture estimates
Relative abundance of adults during sampling events
Pupfish Refuge Spring
0
10
20
30
40
50 Spring 2012
Sampling Events
Grapevine Canyon Spring
Ratio Estimates
Period Marked N 95% CI CV(N) Average Ratio Estimate
Spring 2012 296 456 410-521 0.062 4.07 (3.66-4.65)
Rel
ativ
e ab
un
dan
ce
Mark-recapture estimates
Relative abundance of adults during sampling events
Grapevine Canyon Spring
Spring 2012
Sampling Events
0
50
100
150
200
Upper Blue Point Spring
Ratio Estimates
Rel
ativ
e ab
un
dan
ce
Mark-recapture estimates
Relative abundance of adults during sampling events
Upper Blue Point Spring
Period Marked N 95% CI CV(N) Average Ratio Estimate
Fall 2011 39 47.3 42-61.4 0.095 2.57 (2.29-3.34)
Spring 2012 48 51 48.8-59.1 0.044 2.43 (2.32-2.81)
0
10
20
30 Spring 2012Fall 2011
Sampling Events
Average Ratio Estimates – Used to estimate overall population in Spring 2012
MR Site N/VES
Red Rock 1.49
Pupfish Refuge 2.31
Upper Blue Point 2.43
Grapevine Canyon 4.08
Overall Population Estimate Selectively applied
Average Ratio Estimates to calibrate relative abundances at 11 other sites
Estimate in Spring 2012: 1,387 adult frogs (Range 1,318 – 1,595)
Bradford et al. 2004: 1,100 adult frogs (Range 693 – 1,833)
Upper & Lower Blue Point
Rogers
Black Canyon Sprs.
Bighorn Sheep
Salt Cedar
Boy Scout & Dawn’s
Tassi Pupfish Refuge
Goldstrike
Red Rock
Quail
Grapevine, AZ
Union Pass
Management zone
Conclusion Relative abundance of adults and juveniles during VES from 2004‐2012 at all active sites
700
600
500
400
300
200
100
0 Spr Spr Spr Spr Spr Spr Spr Spr Spr 04 05 06 07 08 09 10 11 12
Storm event
Horse Lime Bearpaw Poppy Union Pass Perkins Pond Quail Tassi Red Rock Grapevine, AZ Pupfish Goldstrike Salt Cedar Dawns Cyn Boy Scout Black Cyn Sprs Bighorn Sheep Rogers Blue Point
Acknowledgements
Special Mention:
Michael Burroughs
Alejandra Cortes
D. Tyler Harrison
Alex Jones
Heidi McMaster
Mark Maynard
Simon Madil
Amelia Savage
Mike Sredl
Mitch Urban
Paul van Els
Michael Webber
Everyone on the Relict Leopard Frog Conservation Team…and many others…
Photo credits: Jef Jaeger & Rebeca Rivera
U.S. Fish and Wildlife Service
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