MORE STRATEGIC MORE STRATEGIC CONSERVATIONCONSERVATION

OF GIANT BULLFROGS IN OF GIANT BULLFROGS IN GAUTENG PROVINCEGAUTENG 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.

A valuable flagship & umbrellaA valuable flagship & umbrella

• Bullfrogs share their breeding habitat with many other anurans.Bullfrogs share their breeding habitat with many other anurans.

• 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.

A valuable flagship & umbrellaA valuable flagship & umbrella

A valuable flagship & umbrellaA valuable flagship & umbrella

• The Giant Bullfrog is widely distributed across SA. The Giant Bullfrog is widely distributed across SA. Roughly a ¼ of its range coincides with the grassland biome.Roughly a ¼ of its range coincides with the grassland biome.(du Preez & Cook 2004)(du Preez & Cook 2004)

• Our grasslands are Our grasslands are highly threatened.highly threatened.(Mucina & Rutherford 2006)(Mucina & Rutherford 2006)

Minter et al. (2004)

A valuable flagship & umbrellaA valuable flagship & umbrella

• Bullfrogs have good public interest and support.Bullfrogs have good public interest and support.

Bullfrog conservation to dateBullfrog conservation to date

Bullfrog conservation to dateBullfrog conservation to date

Bullfrog conservation to dateBullfrog conservation to date

N14 / R28

A bleak futureA bleak future

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

FUTURE EFFORTS TOFUTURE EFFORTS TOEFFECTIVELY CONSERVEEFFECTIVELY CONSERVE

GIANT BULLFROGSGIANT BULLFROGSIN GAUTENGIN GAUTENGNEED TO BE NEED TO BE

PROACTIVEPROACTIVE AND AND STRATEGIC!STRATEGIC!

Realize that…Realize that…

• In most semi-developed parts of Gauteng, individual bullfrogs In most semi-developed parts of Gauteng, individual bullfrogs can still be found.can still be found.

• These bullfrogs:These bullfrogs:– usually struggle to find a place to breed.usually struggle to find a place to breed.– stand a high risk of mortality, e.g. from road traffic.stand a high risk of mortality, e.g. from road traffic.– are highly unlikely to be replaced by juveniles.are highly unlikely to be replaced by juveniles.

The longevity of mature resident bullfrogs masksThe longevity of mature resident bullfrogs maskspoor juvenile recruitment.poor juvenile recruitment.Eventually the species goes extinct.Eventually the species goes extinct.

1

Realize that…Realize that…

• 10 000 breeding adult bullfrogs need to be protected within SA to 10 000 breeding adult bullfrogs need to be protected within SA to prevent the species from being listed as “Vulnerable.”prevent the species from being listed as “Vulnerable.”

Gauteng is responsible for at least Gauteng is responsible for at least NNee = 1000. = 1000.

• To maintain evolutionary adaptability, “minimum viable To maintain evolutionary adaptability, “minimum viable populations” (MVPs) with populations” (MVPs) with NNee = 500 breeding adult bullfrogs should = 500 breeding adult bullfrogs should be protected.be protected.(Franklin 1980)(Franklin 1980)

(For bullfrog populations with a sex-ratio of 1:5+ (For bullfrog populations with a sex-ratio of 1:5+ NN > 1000 adults). > 1000 adults).

Bullfrog populations of > 1000 adults will only be able to persist on Bullfrog populations of > 1000 adults will only be able to persist on very large very large (i.e. > 400ha)(i.e. > 400ha) tracts of undisturbed habitat. tracts of undisturbed habitat.(C. Yetman, unpubl. data)(C. Yetman, unpubl. data)

(Without(Without compensating for climate change). compensating for climate change).2

Diepsloot

Realize that…Realize that…

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

3

1km

1km

The proposed strategyThe proposed strategy

Inside the Gauteng urban edgeInside the Gauteng urban edge

• The focus must shift from bullfrog to wetland conservation.The focus must shift from bullfrog to wetland conservation.

• Where a proposed development will impact on remaining Where a proposed development will impact on remaining bullfrogs and/or bullfrog habitat, bullfrogs and/or bullfrog habitat, ““the polluter paysthe polluter pays”” principle principle should apply.should apply.

• Bullfrogs remaining within Gauteng’s urban edge should be used Bullfrogs remaining within Gauteng’s urban edge should be used as a tool to:as a tool to:– Raise public awareness about the plight of bullfrogs, wetlands Raise public awareness about the plight of bullfrogs, wetlands

and grassland in SA.and grassland in SA.– Encourage people to make their properties and Encourage people to make their properties and

neighbourhoods more inhabitable for wildlife in general.neighbourhoods more inhabitable for wildlife in general.

Inside the Gauteng urban edgeInside the Gauteng urban edge

Outside the Gauteng urban edgeOutside the Gauteng urban edge

• All seasonal wetlands (and terrestrial habitat within a 1km radius All seasonal wetlands (and terrestrial habitat within a 1km radius of these) that lie within the bullfrog’s geographic distribution of these) that lie within the bullfrog’s geographic distribution range (at the quarter degree scale) should trigger a bullfrog range (at the quarter degree scale) should trigger a bullfrog specialist assessment when threatened by transformation.specialist assessment when threatened by transformation.

• At leastAt least two minimum viable META-populations with two minimum viable META-populations with NNee = 500 = 500 breeding adult bullfrogs should be protected and monitored.breeding adult bullfrogs should be protected and monitored.

• The Benoni North/Bapsfontein and Dinokeng areas have been The Benoni North/Bapsfontein and Dinokeng areas have been identified as being especially important for proactive bullfrog identified as being especially important for proactive bullfrog conservation efforts in Gauteng.conservation efforts in Gauteng.

Concluding remarkConcluding remark

By targeting areas By targeting areas outsideoutside the Gauteng urban edge, the Gauteng urban edge, where effective protection of viable populations of Giant where effective protection of viable populations of Giant Bullfrogs is still possible, the value of this species as a Bullfrogs is still possible, the value of this species as a flagship and umbrella for frog, wetland and grassland flagship and umbrella for frog, wetland and grassland

conservation will be maximized.conservation will be maximized.

ReferencesReferences• 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.