Lion populations may be declining in Africa but not as Bauer et al. suggest Jason Riggioa,1, Tim Caroa, Luke Dollarb,c, Sarah M. Durantd, Andrew P. Jacobsond,e, Christian Kiffnerf, Stuart L. Pimmc, and Rudi J. van Aardeg
Historical knowledge and recent surveys attest that lions are declining across parts of Africa (1, 2). We applaud Bauer et al. (3) for assembling available counts because they motivate better monitoring and conservation support. Their own data, however, rejects their claims that lions are “declining everywhere, except in four southern countries” and that lions increase only where “intensively managed.” First, there are some stable and increasing populations in all regions. Moreover, not weighting for population size strongly biases regional population projections. By treating all populations, small and large, equally, Bauer et al. (3) mislead on the overall trend of lion populations. Of 21 populations in southern Africa, only one (Okavango) shows a decline, but the increasing populations are mostly in small, fenced reserves that, combined, support few lions. Niassa is a large, increasing population but is considered a “special case.” Of nine West and Central African lion populations, the largest are stable (Bénoué, 200) or increasing (Pendjari, ∼100). The declining populations are the smallest, with starting populations of fewer than 70 lions. In East Africa, of 15 populations, four are increasing and four are stable. Only four populations show declines strong enough to halve in 20 y (λ < 0.965). Masai Mara and Katavi are the only large populations showing such strong declines. Second, Bauer et al. (3) misrepresent the data from these two sites: Masai Mara: Dataset S1 in ref. 3 records 483 lions in 1991 and 286 lions in 2005. The corresponding dates and densities (4), 31.56 lions per 100 km2 and 18.69 lions per 100 km2, do not match those dates and densities in their assumed respective citations (5, 6): 29.4 lions per 100 km2 in 1992 and
36.9 lions per 100 km2 in 2003 [lions are not mentioned by Ogutu et al. (7)]. Two references (5, 6) actually show lions increasing from 450 to 560 individuals between 1992 and 2003. Katavi: The Katavi data are from road transect surveys designed for herbivores (8). Extrapolating from these transects of limited length and frequency, and hence few lion observations, to the whole park distorts the data. This fact is evidenced by a 2005 playback survey that estimated 168 (range: 77–468) lions in the park (9) and continuing recent documentation of lion prides.* Bauer et al. (3) neglect these data and report zero from 2002 onward. Finally, claims of the efficacy of fencing for lion conservation are misplaced (10). For example, contrary to statements (figure 4 in ref. 3), Kgalagadi is partially fenced, whereas the eastern side of Kruger National Park has not been fenced since 2002. Moreover, small fenced reserves make questionable contributions to lion conservation (10). Certainly, serious threats are mounting and demand attention. That said, it is premature, indeed inappropriate, to level blanket criticism at countries outside southern Africa. The data show that authorities have maintained effective protection for many lion populations and should be congratulated where they have succeeded. Conservationists should also be wary of overstating widespread declines. If such claims are later rejected, science loses credibility. Conservation needs transparency in methods and data, and honest appraisal of the evidence and considerable uncertainties. Bauer et al. (3) have not satisfied these essential requirements.
a
Department of Wildlife, Fish, and Conservation Biology, University of California, Davis, CA 95616; bDepartment of Biology, Pfeiffer University, Misenheimer, NC 28109; cNicholas School of the Environment, Duke University, Durham, NC 27708; dInstitute of Zoology, Zoological Society of London, Regents Park, London NW1 4RY, United Kingdom; eGeography Department, University College London, London WC1E 6BT, United Kingdom; fCenter for Wildlife Management Studies, The School for Field Studies, Karatu, Tanzania; and gConservation Ecology Research Unit, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa Author contributions: J.R., T.C., L.D., S.M.D., A.P.J., C.K., S.L.P., and R.J.v.A. wrote the paper. The authors declare no conflict of interest. 1 To whom correspondence should be addressed. Email: [email protected].
*www.nomad-tanzania.com/blogs/chada-katavi. Accessed October 29, 2015.
www.pnas.org/cgi/doi/10.1073/pnas.1521506113
PNAS | January 12, 2016 | vol. 113 | no. 2 | E107–E108
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LETTER
1 Henschel P, et al. (2014) The lion in West Africa is critically endangered. PLoS One 9(1):e83500. 2 Riggio J, et al. (2013) The size of savannah Africa: A lion’s (Panthera leo) view. Biodivers Conserv 22(1):17–35. 3 Bauer H, et al. (2015) Lion (Panthera leo) populations are declining rapidly across Africa, except in intensively managed areas. Proc Natl Acad Sci USA 112(48): 14894–14899. 4 Packer C, et al. (2013) Conserving large carnivores: Dollars and fence. Ecol Lett 16(5):635–641. 5 Ogutu JO, Dublin HT (1998) The response of lions and spotted hyaenas to sound playbacks as a technique for estimating population size. Afr J Ecol 36(1):83–95. 6 Ogutu JO, Bhola N, Reid R (2005) The effects of pastoralism and protection on the density and distribution of carnivores and their prey in the Mara ecosystem of Kenya. J Zool (Lond) 265(3):281–293. 7 Ogutu JO, Owen-Smith N, Piepho H-P, Said MY (2011) Continuing wildlife population declines and range contraction in the Mara region of Kenya during 19772009. J Zool (Lond) 285(2):99–109. 8 Caro T (2011) On the merits and feasibility of wildlife monitoring for wildlife conservation: A case study from Katavi National Park, Tanzania. Afr J Ecol 49(3): 320–331. 9 Kiffner C, Meyer B, Mühlenberg M, Waltert M (2009) Plenty of prey, few predators: What limits lions Panthera leo in Katavi National Park, western Tanzania? Oryx 43(1):52–59. 10 Creel S, et al. (2013) Conserving large populations of lions - the argument for fences has holes. Ecol Lett 16(11):1413–e1–e3.
E108 | www.pnas.org/cgi/doi/10.1073/pnas.1521506113
Riggio et al.
Historical knowledge and recent surveys attest that lions are declining across parts of Africa (1, 2). We applaud Bauer et al. (3) for assembling available counts because they motivate better monitoring and conservation support. Their own data, however, rejects their claims that lions are “declining everywhere, except in four southern countries” and that lions increase only where “intensively managed.” First, there are some stable and increasing populations in all regions. Moreover, not weighting for population size strongly biases regional population projections. By treating all populations, small and large, equally, Bauer et al. (3) mislead on the overall trend of lion populations. Of 21 populations in southern Africa, only one (Okavango) shows a decline, but the increasing populations are mostly in small, fenced reserves that, combined, support few lions. Niassa is a large, increasing population but is considered a “special case.” Of nine West and Central African lion populations, the largest are stable (Bénoué, 200) or increasing (Pendjari, ∼100). The declining populations are the smallest, with starting populations of fewer than 70 lions. In East Africa, of 15 populations, four are increasing and four are stable. Only four populations show declines strong enough to halve in 20 y (λ < 0.965). Masai Mara and Katavi are the only large populations showing such strong declines. Second, Bauer et al. (3) misrepresent the data from these two sites: Masai Mara: Dataset S1 in ref. 3 records 483 lions in 1991 and 286 lions in 2005. The corresponding dates and densities (4), 31.56 lions per 100 km2 and 18.69 lions per 100 km2, do not match those dates and densities in their assumed respective citations (5, 6): 29.4 lions per 100 km2 in 1992 and
36.9 lions per 100 km2 in 2003 [lions are not mentioned by Ogutu et al. (7)]. Two references (5, 6) actually show lions increasing from 450 to 560 individuals between 1992 and 2003. Katavi: The Katavi data are from road transect surveys designed for herbivores (8). Extrapolating from these transects of limited length and frequency, and hence few lion observations, to the whole park distorts the data. This fact is evidenced by a 2005 playback survey that estimated 168 (range: 77–468) lions in the park (9) and continuing recent documentation of lion prides.* Bauer et al. (3) neglect these data and report zero from 2002 onward. Finally, claims of the efficacy of fencing for lion conservation are misplaced (10). For example, contrary to statements (figure 4 in ref. 3), Kgalagadi is partially fenced, whereas the eastern side of Kruger National Park has not been fenced since 2002. Moreover, small fenced reserves make questionable contributions to lion conservation (10). Certainly, serious threats are mounting and demand attention. That said, it is premature, indeed inappropriate, to level blanket criticism at countries outside southern Africa. The data show that authorities have maintained effective protection for many lion populations and should be congratulated where they have succeeded. Conservationists should also be wary of overstating widespread declines. If such claims are later rejected, science loses credibility. Conservation needs transparency in methods and data, and honest appraisal of the evidence and considerable uncertainties. Bauer et al. (3) have not satisfied these essential requirements.
a
Department of Wildlife, Fish, and Conservation Biology, University of California, Davis, CA 95616; bDepartment of Biology, Pfeiffer University, Misenheimer, NC 28109; cNicholas School of the Environment, Duke University, Durham, NC 27708; dInstitute of Zoology, Zoological Society of London, Regents Park, London NW1 4RY, United Kingdom; eGeography Department, University College London, London WC1E 6BT, United Kingdom; fCenter for Wildlife Management Studies, The School for Field Studies, Karatu, Tanzania; and gConservation Ecology Research Unit, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa Author contributions: J.R., T.C., L.D., S.M.D., A.P.J., C.K., S.L.P., and R.J.v.A. wrote the paper. The authors declare no conflict of interest. 1 To whom correspondence should be addressed. Email: [email protected].
*www.nomad-tanzania.com/blogs/chada-katavi. Accessed October 29, 2015.
www.pnas.org/cgi/doi/10.1073/pnas.1521506113
PNAS | January 12, 2016 | vol. 113 | no. 2 | E107–E108
LETTER
LETTER
1 Henschel P, et al. (2014) The lion in West Africa is critically endangered. PLoS One 9(1):e83500. 2 Riggio J, et al. (2013) The size of savannah Africa: A lion’s (Panthera leo) view. Biodivers Conserv 22(1):17–35. 3 Bauer H, et al. (2015) Lion (Panthera leo) populations are declining rapidly across Africa, except in intensively managed areas. Proc Natl Acad Sci USA 112(48): 14894–14899. 4 Packer C, et al. (2013) Conserving large carnivores: Dollars and fence. Ecol Lett 16(5):635–641. 5 Ogutu JO, Dublin HT (1998) The response of lions and spotted hyaenas to sound playbacks as a technique for estimating population size. Afr J Ecol 36(1):83–95. 6 Ogutu JO, Bhola N, Reid R (2005) The effects of pastoralism and protection on the density and distribution of carnivores and their prey in the Mara ecosystem of Kenya. J Zool (Lond) 265(3):281–293. 7 Ogutu JO, Owen-Smith N, Piepho H-P, Said MY (2011) Continuing wildlife population declines and range contraction in the Mara region of Kenya during 19772009. J Zool (Lond) 285(2):99–109. 8 Caro T (2011) On the merits and feasibility of wildlife monitoring for wildlife conservation: A case study from Katavi National Park, Tanzania. Afr J Ecol 49(3): 320–331. 9 Kiffner C, Meyer B, Mühlenberg M, Waltert M (2009) Plenty of prey, few predators: What limits lions Panthera leo in Katavi National Park, western Tanzania? Oryx 43(1):52–59. 10 Creel S, et al. (2013) Conserving large populations of lions - the argument for fences has holes. Ecol Lett 16(11):1413–e1–e3.
E108 | www.pnas.org/cgi/doi/10.1073/pnas.1521506113
Riggio et al.
