Surasinghe, T. D. and Baldwin, R. F. (2012). Exploitative competition among stream salamanders along a land-use gradient. The Annual meeting of the Southeastern Partners in Amphibian and Reptile Conservation, Pikesville, TN.

1. EXPLOITATIVE COMPETITION AMONG STREAM SALAMANDERS ALONG A LAND-USE GRADIENT
Thilina Surasinghe, Mark McAllister, Robert Baldwin
Dept of Biological Sciences, School of Agricultural, Forest, and Environmental Sciences, Clemson University, SC
Objectives
Study spatial occupancy of D. quadramaculatus & D. fuscus under four riparian land-uses: forested, urban, agricultural, residential areas.
Study competition between D. quadramaculatus and D. fuscus.
100
100
Agricultural Riparian Land-Use
Urban Riparian Land-Use 90
BB with ND
90
Black-Bellied Northern Dusky BB with ND
80
salamander Salamander 80 ND with BB
ND with BB
70 BB only 70 BB only
Percentage Occurrence
Percentage Occurrence
Introduction 60 ND only 60 ND only
Target species: Two species of stream salamanders- the Black-bellied salamander (Desmognathus quadramaculatus) and the Northern Dusky 50 50
Salamander (Desmognathus fuscus).
40 40
D. fuscus is a small-sized subordinate species among stream salamanders (SVL: 50-60 mm ).
30
30
D. Quadramaculatus is a large bodied (SVL: 70-80 mm ) species hypothesized to dominate stream salamander communities
20
20
10
20 20 10
Agricultural Riparain Land-Use
18 18 0
Urban Riparain Land-Use Bank Crevices Channel Bottom Channel-Bank Interface Bank Surface 0
16 16 Microhabitat Types Bank Crevices Channel Bottom Channel-Bank Interface Bank Surface
Microhabitat Types
14 14
100 120
12 12
Residential Riparain Land-Use Type
Short Wall
short wall
10 10 90 Forested Riparian Land-Use
8 8 100
80
BB with ND BB with ND
6 6
70
4 4 ND with BB ND with BB
80
Percentage Occurrence
2 2
60
Percentage Occurrence
BB only BB only
0 0
0 5 10 15 20 25 30 35 40 45 50 0 5 10 15 20 25 30 35 40 45 50
Long wall
50 ND only
Long wall ND only 60
Blabk-bellied Northern-dusky Black-bellied Northern-dusky
40
20 20
30 40
Residential Riparain Land-Use 18
18 Forested Riparain Land-Use
20
16 16
14 14
10 20
Short Wall
12 12
Short Wall
0
10 10
Bank Crevices Channel Bottom Channel-Bank Interface Bank Surface
0
8 8 Microhabitat Types
Bank Crevices Channel Bottom Channel-Bank Interface Bank Surface
6 6 Microhabitat Types
4 4
2 2
Microhabitat selectivity of the Black-bellied salamander (Desmognathus quadramaculatus) and the Northern Dusky Salamander
0 0
0 5 10 15 20 25 30 35 40 45 50 0 5 10 15 20 25 30 35 40 45 50
Long wall Long wall (Desmognathus fuscus) along the riparian land-use gradient
Northern-dusky Black-bellied Black-bellied Northern-dusky
Results & Conclusion
Methodology
D. quadramaculatus: In each land-use simulation, occupied the stream banks and chose rock crevices as their preferred microhabitat.
The experiment simulated four riparian land-use types : forested, agricultural, residential, and urban.
Showed high site fidelity.
The artificial streams were filled with native stream substrates and water. Air pumps were used to mimic the streams oxygen conditions.
D. fuscus: Broad microhabitat selectivity including interstitial space beneath rocks and logs, leaf litter, sand and gravel. Mostly occupied
The target species were captured from the wild.
the stream channel, notably in the forested tank. Observed in areas of the bank unoccupied by D. quadramaculatus in other land-use
Only males of the same SVL size class were used (50 - 60 mm for D. fuscus and 70 - 80 mm for D.qudramaculatus).
simulations,
The salamanders were fed with live invertebrates (mealworms, red worms, bloodworms, and crickets).
No aggression or predation was observed.
Observations were made under species co-existence and species isolation, each phase phase lasted 5 days.
No evidence on D. fuscus competitively displacing D. quadramaculatus.
Each land use type was duplicated in the same channel with different individuals.
Once D. quadramaculatus is removed from the tanks, D. fuscus moved to the microhabitats previously occupied by D. quadramaculatus
20 min Observations were made daily in every third hour (0900 to 2100 hours).
indicating that they are dominant in competition for space and microhabitat.
Records were taken on salamander’s aggressive behavior on an ordinal scale.
The study is still continuing and more replications will be done in future.
The microhabitat occupied and the precise location of all the animals in the artificial streams were recorded.