Invasive Biology: The Cane Toad

1. Invasive Biology:The Cane Toad By: Adriana Carpio and Juan Escobar

2. The Cane Toad • Spread of the Cane Toad threatens biodiversity • Intraspecific competition • Poisoning of native species • Consumption of small native animals • Combat invasion through knowledge • Mode of dispersal • Rate of spread • Preferred habitat

3. Toads on Roads • Hypothesis: • Use of roads enable toads to disperse more rapidly than densely vegetated areas

4. Background • Previous radio tracking showed that toads prefer open areas, especially roads • Avoids areas with dense vegetation, except for retreat sites

5. Location of Study • Northern Territory of Australia • Wet-dry Tropics • Varied types of habitats • Seasonally flooded plains • Small hills • Woodland • Pastures • Climate • Hot year round • 31-34 C maximum • 15-24 C minimum • 80% of annual precipitation in wet season

6. Australia

7. Tracking • Size of location: 2800 ha • Duration: Feb 2005 – Feb 2006 • 49 adults toads fitted with radio tracking device • Radio device placed around the waist then released • Exact location was recorded daily with GPS • Inspection of the toad locations suggested they preferentially moved along roadways and fence lines

8. Tracking Device

9. Orientation • Toads selectively disperse along roads • Generally they position themselves along side the road • NOT facing the road

10. Results • Radio Tracking Test • All toads moved in the same direction, NW along the side of the road • Toad routes overlapped strongly • Toads did NOT spread out

11. Tracking Results

12. Locomotion • Toads were placed in two different settings: • Open areas with hard-packed gravel • Areas with dense pasture grass • Toads were capture and kept for a period of 24 hrs • Each toad was tested once • Testing took placed during the evening, when toads are most active

13. Speed Test • Toad was placed in the center of two circles, each with different settings • Inner circle of each had radius of 1m • Outer circle had radius of 2m • Toads were poked on the back with stick to make them move • Number of hops were recorded as well as time it took to travel through each circle

14. Results • Locomotion and Speed • Toads tested on hard substrate: • Had longer jumps on second meter than first • Waited less time between jumps on second meter than on first • Toads tested on grassy substrate: • Had shorter jumps on second meter than first • Jumped less often on second meter than first

15. TOADS PREFER OPEN SPACES!!!

16. Proposal • Prior to the introduction of the Cane Toad Australia had no native toad species • Only frogs were native • Frogs and toads are genetically different • Recently a gene was isolated from the Cane Toad • This gene is responsible for triggering sexual maturity

17. Proposal • The gene will be modified • It will be inserted into a virus • The virus will not cause disease, but will act as a vector • The virus will then be introduced to the environment • The virus will multiply, consequently multiplying the gene

18. Proposal • The gene would insert itself into the toad gene sequence • This gene would then be reproduced in the toad and passed on to the offspring • The offspring would have the active gene • Not being able to reach sexual maturity

19. The End

20. Bibliography • Brown G.P., Phillips B.L., Webb J.K, Shine R. (2006) Toad on the road: Use of roads as dispersal corridors by cane toads (Bufo marinus) at an invasion front in tropical Australia. Biological Conservation 1 3 3: 8 8 –9 4. • http://www.fdrproject.org/