Effects of Wetland Fragmentation on Freshwater Turtle ...
Effects of Wetland Fragmentation on Freshwater Turtle Populations in the Delaware Estuary Harold W. Avery1 James R. Spotila1 Walter F. Bien1 1Department
of Bioscience and Biotechnology Drexel University
Hypothesis: Why is SCPD-4 Better? - Connectivity to Delaware River, a Source Population for red-bellied turtles
32 wetlands were studied at PHL to determine turtle densities and nest sites during 2004 and 2005. Most wetlands have been searched for nesting sites and trapped for turtles.
State-Threatened Adult Female Red-bellied Turtle (Pseudemys rubriventris)
Other Native Turtle Species at Philadelphia International Airport:
common snapping turtle (Chelydra serpentina)
painted turtle (Chrysemys picta)
musk turtle (Sternotherus odoratus)
Invasive red-eared slider (Trachemys scripta)
Baited traps
Dried Corn Mixed Veg. Sardine
Turtle Captures 32 Wetlands at PHL (2004 and 2005 Field Seasons) • > 40,000 trap-hours • 2,611 turtle captures (all species) • 1,911 individual turtles processed • 113 state-threatened red-bellied turtles marked, measured and released
3 Types of Wetlands at Philadelphia International Airport:
Isolated Canals narrow steep-banked highly modified
Isolated Canals narrow steep-banked highly modified
Estimated Popn Density: 0 – 2 red-bellied turtles ha-1
Isolated Larger Wetlands - highly modified upland areas
Isolated Larger Wetlands - highly modified upland areas
Estimated Popn Density: 44.4 red-bellied turtles ha-1
Interconnected Wetlands-
comparatively less disturbed adjacent upland areas
Interconnected WetlandsPublic Access
comparatively less disturbed adjacent upland areas
Estimated Popn Density: 99.2 red-bellied turtles ha-1
“SCPD4” – Density of 159.1 ha-1 !
Culvert Interconnections Exist from SCPD4 to Delaware River
e r a aw l e D
er v i R
Size distributions of red-bellied turtles inhabiting wetlands at Philadelphia International Airport
Interconnected large wetlands (outside Airport grounds)
Interconnected large wetlands (inside Airport grounds)
Isolated canals (inside Airport grounds)
Movements of Turtles Between Wetlands at the Philadelphia International Airport
Red-bellied Painted Snapping Stinkpot
Arrows indicate direction of travel. Lines indicate minimum distance traveled; actual routes are not known
Movements of Turtles Between Wetlands at the Philadelphia International Airport John Heinz Nat’l Widlife Refuge
Red-bellied Painted Snapping Stinkpot
Arrows indicate direction of travel. Lines indicate minimum distance traveled; actual routes are not known
Turtle movements: Inter-connected Wetland Landscape Red-bellied Painted Snapping Stinkpot
Arrows indicate direction of travel. Lines indicate minimum distance traveled; actual routes are not known
DR9 (Ft. Mifflin)
Nest Sites are Limited to Wetland Margins
2004 P. rubriventris 2004 C. picta 2004 C. serpentina
2005 P. rubriventris 2005 C. picta 2005 C. serpentina
Nest sites are Limited to Wetland Margins
2004 P. rubriventris 2004 C. picta 2004 C. serpentina
2005 P. rubriventris 2005 C. picta 2005 C. serpentina
Problem: Turtles crossing roads to nest in upland areas have elevated risks of mortality
Locations of adult turtle mortalities along boundary road of PHL during 2004 and 2005
Results: • Turtles crossing roads to nest in upland areas have elevated risks of mortality • Decreased adult survivorship reduces probability of viability and recovery of populations ~ 98% adult survivorship = stable popn (Congdon et al. 1993)
Solution: Identify and “Augment” Movement Corridors
Results: Populations of red-bellied turtles inhabiting interconnected wetlands have greater densities of individuals, and have more size classes represented, than populations inhabiting isolated and highly modified wetlands.
Conclusion: “Wetland landscapes” are important to red-bellied turtle populations and potential recovery
Implications: “Wetland landscapes” are important
to red-bellied turtle populations and potential recovery Recovery of red-bellied turtle populations will require protection of remaining interconnected wetland landscapes within the Delaware Estuary.
Mark – Recapture Short-term (1-2 yr): - Where are turtles located? - How many turtles are there? - What movements are occurring? Long-term (5 + yr): - What is survivorship of different size / age classes? - What are rates and causes of mortality? - Are populations viable?
Drexel Field Researchers
Number of Personnel
Faculty
Graduate Undergraduate Students students
Other assistants
3
11
4
14
Nest sites were located along steep open banks of canal wetlands (e.g.,SCPD4) regardless of less disturbed adjacent areas
2004 P. rubriventris 2004 C. picta 2004 C. serpentina
2005 P. rubriventris 2005 C. picta 2005 C. serpentina
Nest predation high along wetland margins Wetland fences used to constrain wildlife cause turtles to nest along inside of fences resulting in high rates nest predation.
Bank mowing during nesting season (May – July) and nest incubation (May – September) pose risks to nesting females, nests, and emerging hatchlings
Unmowed Banks
Mowed Banks
Proposed Solution: Mowing risks can be minimized and may be BENEFICIAL to nesting if done at non-nesting times of the year (e.g., Oct. – March).
Unmowed Banks
Mowed Banks
Public Access and the Population Status of Invasive Red-eared Sliders: Red-eared slider turtles are more abundant and have more size classes represented in populations located outside Airport grounds than inside.
57 Captured and Removed From Wetlands
Problem: Wetlands with Public Access Have More Invasive Red-eared Sliders
Solution: Educate the Public on the Impacts of Invasive Species to Native Species • Conduct further research on impacts • Disperse findings widely via brochures, outreach, news media, etc. to reduce rate of captive releases
Interconnected Wetlands - Closed to Public Access
Size distributions of red-eared slider turtles inhabiting wetlands at Philadelphia International Airport
Interconnected large wetlands outside Airport grounds
Interconnected large wetlands inside Airport grounds
Isolated canals inside Airport grounds
Interconnected Wetlandsless modified
of Bioscience and Biotechnology Drexel University
Hypothesis: Why is SCPD-4 Better? - Connectivity to Delaware River, a Source Population for red-bellied turtles
32 wetlands were studied at PHL to determine turtle densities and nest sites during 2004 and 2005. Most wetlands have been searched for nesting sites and trapped for turtles.
State-Threatened Adult Female Red-bellied Turtle (Pseudemys rubriventris)
Other Native Turtle Species at Philadelphia International Airport:
common snapping turtle (Chelydra serpentina)
painted turtle (Chrysemys picta)
musk turtle (Sternotherus odoratus)
Invasive red-eared slider (Trachemys scripta)
Baited traps
Dried Corn Mixed Veg. Sardine
Turtle Captures 32 Wetlands at PHL (2004 and 2005 Field Seasons) • > 40,000 trap-hours • 2,611 turtle captures (all species) • 1,911 individual turtles processed • 113 state-threatened red-bellied turtles marked, measured and released
3 Types of Wetlands at Philadelphia International Airport:
Isolated Canals narrow steep-banked highly modified
Isolated Canals narrow steep-banked highly modified
Estimated Popn Density: 0 – 2 red-bellied turtles ha-1
Isolated Larger Wetlands - highly modified upland areas
Isolated Larger Wetlands - highly modified upland areas
Estimated Popn Density: 44.4 red-bellied turtles ha-1
Interconnected Wetlands-
comparatively less disturbed adjacent upland areas
Interconnected WetlandsPublic Access
comparatively less disturbed adjacent upland areas
Estimated Popn Density: 99.2 red-bellied turtles ha-1
“SCPD4” – Density of 159.1 ha-1 !
Culvert Interconnections Exist from SCPD4 to Delaware River
e r a aw l e D
er v i R
Size distributions of red-bellied turtles inhabiting wetlands at Philadelphia International Airport
Interconnected large wetlands (outside Airport grounds)
Interconnected large wetlands (inside Airport grounds)
Isolated canals (inside Airport grounds)
Movements of Turtles Between Wetlands at the Philadelphia International Airport
Red-bellied Painted Snapping Stinkpot
Arrows indicate direction of travel. Lines indicate minimum distance traveled; actual routes are not known
Movements of Turtles Between Wetlands at the Philadelphia International Airport John Heinz Nat’l Widlife Refuge
Red-bellied Painted Snapping Stinkpot
Arrows indicate direction of travel. Lines indicate minimum distance traveled; actual routes are not known
Turtle movements: Inter-connected Wetland Landscape Red-bellied Painted Snapping Stinkpot
Arrows indicate direction of travel. Lines indicate minimum distance traveled; actual routes are not known
DR9 (Ft. Mifflin)
Nest Sites are Limited to Wetland Margins
2004 P. rubriventris 2004 C. picta 2004 C. serpentina
2005 P. rubriventris 2005 C. picta 2005 C. serpentina
Nest sites are Limited to Wetland Margins
2004 P. rubriventris 2004 C. picta 2004 C. serpentina
2005 P. rubriventris 2005 C. picta 2005 C. serpentina
Problem: Turtles crossing roads to nest in upland areas have elevated risks of mortality
Locations of adult turtle mortalities along boundary road of PHL during 2004 and 2005
Results: • Turtles crossing roads to nest in upland areas have elevated risks of mortality • Decreased adult survivorship reduces probability of viability and recovery of populations ~ 98% adult survivorship = stable popn (Congdon et al. 1993)
Solution: Identify and “Augment” Movement Corridors
Results: Populations of red-bellied turtles inhabiting interconnected wetlands have greater densities of individuals, and have more size classes represented, than populations inhabiting isolated and highly modified wetlands.
Conclusion: “Wetland landscapes” are important to red-bellied turtle populations and potential recovery
Implications: “Wetland landscapes” are important
to red-bellied turtle populations and potential recovery Recovery of red-bellied turtle populations will require protection of remaining interconnected wetland landscapes within the Delaware Estuary.
Mark – Recapture Short-term (1-2 yr): - Where are turtles located? - How many turtles are there? - What movements are occurring? Long-term (5 + yr): - What is survivorship of different size / age classes? - What are rates and causes of mortality? - Are populations viable?
Drexel Field Researchers
Number of Personnel
Faculty
Graduate Undergraduate Students students
Other assistants
3
11
4
14
Nest sites were located along steep open banks of canal wetlands (e.g.,SCPD4) regardless of less disturbed adjacent areas
2004 P. rubriventris 2004 C. picta 2004 C. serpentina
2005 P. rubriventris 2005 C. picta 2005 C. serpentina
Nest predation high along wetland margins Wetland fences used to constrain wildlife cause turtles to nest along inside of fences resulting in high rates nest predation.
Bank mowing during nesting season (May – July) and nest incubation (May – September) pose risks to nesting females, nests, and emerging hatchlings
Unmowed Banks
Mowed Banks
Proposed Solution: Mowing risks can be minimized and may be BENEFICIAL to nesting if done at non-nesting times of the year (e.g., Oct. – March).
Unmowed Banks
Mowed Banks
Public Access and the Population Status of Invasive Red-eared Sliders: Red-eared slider turtles are more abundant and have more size classes represented in populations located outside Airport grounds than inside.
57 Captured and Removed From Wetlands
Problem: Wetlands with Public Access Have More Invasive Red-eared Sliders
Solution: Educate the Public on the Impacts of Invasive Species to Native Species • Conduct further research on impacts • Disperse findings widely via brochures, outreach, news media, etc. to reduce rate of captive releases
Interconnected Wetlands - Closed to Public Access
Size distributions of red-eared slider turtles inhabiting wetlands at Philadelphia International Airport
Interconnected large wetlands outside Airport grounds
Interconnected large wetlands inside Airport grounds
Isolated canals inside Airport grounds
Interconnected Wetlandsless modified
