MORE STRATEGIC CONSERVATION OF GIANT BULLFROGS IN GAUTENG PROVINCE

1. MORE STRATEGIC CONSERVATIONOF GIANT BULLFROGS IN GAUTENG PROVINCE 1Caroline A. Yetman, 2Craig A. Whittington-Jones, 3Graham J. Alexander, 4Vincent Carruthers, 5Clayton L. Cook 1Centre For Environmental Studies, Department of Zoology and Entomology, University of Pretoria, Pretoria, 0002, South Africa, cayetman@zoology.up.ac.za; 2Fauna Unit, Directorate of Nature Conservation, Gauteng, Department of Agriculture, Conservation and Environment, P.O. Box 8769, Johannesburg, 2000, South Africa; 3School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Private Bag 3, WITS, Johannesburg, 2050, South Africa; 4VC Management Services CC, P.O. Box 368, Johannesburg, 2128, South Africa; 5Department of Biodiversity, University of Limpopo, Private Bag X1106, Sovenga, 0727, South Africa.

2. A valuable flagship & umbrella • Bullfrogs share their breeding habitat with many other anurans.

3. A valuable flagship & umbrella • Seasonal pans and vleis used by bullfrogs and other anurans for breeding represent important sources of ecosystem productivity, but often go unnoticed or are treated as expendable.

4. A valuable flagship & umbrella • The Giant Bullfrog is widely distributed across SA. Roughly a ¼ of its range coincides with the grassland biome. (du Preez & Cook 2004) • Our grasslands are highly threatened. (Mucina & Rutherford 2006) Minter et al. (2004)

5. A valuable flagship & umbrella • Bullfrogs have good public interest and support.

6. Bullfrog conservation to date

7. Bullfrog conservation to date

8. Bullfrog conservation to date N14 / R28

9. A bleak future • With expansion of Gauteng’s urban edge, and concomitant urban densification of land, persistence of the bullfrog populations at Glen Austin, Bullfrog and Sand Pan beyond the next 50 years is doubtful.

10. FUTURE EFFORTS TOEFFECTIVELY CONSERVE GIANT BULLFROGSIN GAUTENGNEED TO BE PROACTIVE AND STRATEGIC!

11. 1 Realize that… • In most semi-developed parts of Gauteng, individual bullfrogs can still be found. • These bullfrogs: • usually struggle to find a place to breed. • stand a high risk of mortality, e.g. from road traffic. • are highly unlikely to be replaced by juveniles. The longevity of mature resident bullfrogs masks poor juvenile recruitment. Eventually the species goes extinct.

12. 2 Realize that… • 10 000 breeding adult bullfrogs need to be protected within SA to prevent the species from being listed as “Vulnerable.” Gauteng is responsible for at least Ne = 1000. • To maintain evolutionary adaptability, “minimum viable populations” (MVPs) with Ne = 500 breeding adult bullfrogs should be protected. (Franklin 1980) (For bullfrog populations with a sex-ratio of 1:5+ N > 1000 adults). Bullfrog populations of > 1000 adults will only be able to persist on very large (i.e. > 400ha) tracts of undisturbed habitat. (C. Yetman, unpubl. data) (Without compensating for climate change).

13. Diepsloot

14. 3 Realize that… Given the extent of existing and proposed development within Gauteng’s urban edge, the feasibility of conserving sufficiently large tracts of terrestrial habitat to protect MVPs of bullfrogs around remaining breeding sites is LOW.

15. 1km

16. 1km

17. The proposed strategy

18. Inside the Gauteng urban edge • The focus must shift from bullfrog to wetland conservation. • Where a proposed development will impact on remaining bullfrogs and/or bullfrog habitat, “the polluter pays” principle should apply. • Bullfrogs remaining within Gauteng’s urban edge should be used as a tool to: • Raise public awareness about the plight of bullfrogs, wetlands and grassland in SA. • Encourage people to make their properties and neighbourhoods more inhabitable for wildlife in general.

19. Inside the Gauteng urban edge

20. Outside the Gauteng urban edge • All seasonal wetlands (and terrestrial habitat within a 1km radius of these) that lie within the bullfrog’s geographic distribution range (at the quarter degree scale) should trigger a bullfrog specialist assessment when threatened by transformation. • At least two minimum viable META-populations with Ne = 500 breeding adult bullfrogs should be protected and monitored. • The Benoni North/Bapsfontein and Dinokeng areas have been identified as being especially important for proactive bullfrog conservation efforts in Gauteng.

23. Concluding remark By targeting areas outside the Gauteng urban edge, where effective protection of viable populations of Giant Bullfrogs is still possible, the value of this species as a flagship and umbrella for frog, wetland and grassland conservation will be maximized.

24. References • du Preez, L.H. & Cook, C. (2004). Genus Pyxicephalus Tschudi, 1838 (Family Ranidae). In: Atlas and Red Data Book of the frogs of South Africa, Lesotho and Swaziland (L.R. Minter, M. Burger, J.A. Harrison, H.H. Braack, P.J. Bishop, & D. Kloepfer, eds) pp 298-303. SI/MAB Series #9, Smithsonian Institution, Washington DC, USA. • Franklin, I.A. (1980). Evolutionary change in small populations. In: Conservation Biology, an Evolutionary-Ecological Perspective (M.E. Soulé & B.A. Wilcox, eds) pp 135-149. Sinauer Associates, Sunderland, MA, USA. • Mucina, L. & Rutherford, M.C. (2006). The Vegetation of South Africa, Lesotho and Swaziland. Strelitzia 19, South African National Biodiversity Insititute, Pretoria.