Published: March 18, 2013

Must We Fence Parks to Save Lions?

Bruce Patterson, MacArthur Curator of Mammals, Integrative Research Center

Conservation is often complicated.

Lions have suffered dramatic population and geographic range collapse owing to human activities.  They now occur in less than 30% of their historic range and total numbers have fallen by 70% to 33,000 since 1980.  Retaliatory killing in the wake of livestock depredations, habitat loss and fragmentation, and prey loss are the main factors responsible for these declines.  As bad as things are, the problem is worsening.

Dr. Craig Packer (U. Minnesota) organized a host of scientists and managers who studied lion populations across 11 African nations and 42 protected areas, including me and my colleagues. Each of us furnished population trends over at least 8 years and details of their management budgets; some areas were enclosed by fences (black symbols) and others were not (red symbols).

Reserves varied in how closely lion populations approached the reserve's carrying capacity (horizontal red line in each plot, estimated by ecological models) and their population trends.  Generally, fenced reserves (black labels) held more stable populations and these were closer to carrying capacity than unfenced populations (red labels).  The Taita (Kenya) reserve documents the population studied by MacArthur Curator Bruce Patterson and his colleagues and volunteers.

Depressed growth should only characterize populations above the carrying capacity (100%), as was the case for the fenced reserves (line). The unfenced reserves were exposed to a variety of density-independent factors affecting growth.

Fenced reserves were far more likely to maintain lion populations over the medium and long-term.  This analysis shows the percentage of populations expected to persist at > 10% of their carrying capacity into the future.

The most remarkable finding was the effect of expenditures needed to manage the reserves.  $500 per km2 per year permitted a fenced reserve to maintain lions near 80% of capacity.  Four times(!) as much money was needed to maintain an unfenced population at only half its capacity.

There are many reasons to be unhappy with these results, but the study’s conclusions seem inescapable. Despite their detrimental effects on gene flow and migratory species, fences are effective in containing large predators--protecting surrounding communities from their depredations.  They also exclude human and livestock encroachment and resource extraction (via bushmeat and grazing) from reserves.  Fencing reserves requires substantial capital investment and entails additional management expenditures to ensure outbreeding, etc.  However, it may represent the only means to protect a growing African population from large and dangerous predators, and vice versa!

To read more about this work, read our recent article:

Packer, C. et al. (numerous co-authors including BDP). 2013. Conserving large carnivores: Dollars and fence. Ecology Letters  article  supplemental_material

To learn more about Bruce Patterson's research program, visit his webpages:

Bruce Patterson

I study several topics in evolutionary biology, focusing on the diversification, distribution and conservation of mammals. The breadth of my research is testimony to the facts that no interesting biological questions are ever fully answered and progress towards answering them invariably opens up a variety of others.  Curiosity, opportunity, and a bit of wanderlust have diversified my program and caused it to span two continents.


Density of terrestrial vertebrate species ( Wonder why I study tropical animals?!

For most of my career, I have used museum specimens to study the systematics and biogeography of Neotropical mammals.  Collaborating with scientists and students in Ecuador, Peru, Bolivia, Brazil, and Chile, I have worked throughout the Andes, Amazonia, as well as Atlantic, Valdivian, and Magellanic Forests. While documenting some of the world's richest and most highly endemic faunas, we regularly discover and describe new taxa of marsupials, rodents, and bats and use them in regional and continental reconstructions of phylogeny and biogeography. The program offers abundant training opportunities for American and Latin American students, both in the lab and in the field.  Beginning in 2011, I started a parallel project on the The Bats of Kenya with colleagues Paul Webala and Carl Dick.  This project is designed to document the distribution and status of more than 100 species of bats that occur in Kenya and to shed light on their ecological roles and current status.

Collecting parasites in the course of these systematic studies led to my interest in host-parasite coevolution.  Ectoparasites recovered from mammals and birds are used to reconstruct the radiation of parasite groups and to assess their distributions across hosts and geography.  These studies identify factors that govern the distribution, abundance, and host specificity of parasites.  Together with Carl Dick (until 2009 a post-doc here at the Museum, now at Western Kentucky University) and Katharina Dittmar (SUNY Buffalo), we have developed a broad range of studies on the ecology, coevolution, and phylogeny of these interesting flies.  Interest in the unstudied ectoparasite communities of African bats helped fuel our collaborations with Kenyan Paul Webala to survey the diverse bat communities of Kenya.        


A Hipposideros bat with an ectoparasitic Penicillidia bat fly

A second, derivative program focuses on host-parasite coevolution.  Ectoparasites recovered from mammal and bird specimens are used to reconstruct the evolutionary radiations of parasite groups and assess their current distributions across hosts and geography, factors governing their distribution, abundance, and host specificity.  Work on bat flies has been developed with Carl Dick (until 2009 a post-doc here at the Museum, but now at Western Kentucky University) and Katharina Dittmar (SUNY Buffalo) on their ecology and phylogeny. With NSF funding, we recently curated the world's largest collection of flies, which now guides our understanding of host associations and fuels the taxon-sampling in our phylogenetic work (also supported by NSF). Undergrad and grad students are involved in this work in Chicago, Buffalo, and Bowling Green. Interest in the mostly unexplored ectoparasite communities of African bats helped fuel my collaboration with Kenya Wildlife Service ecologist Paul Webala on surveying the diverse bat communities of Kenya (see above). 

Photo by B. A. Harney in Tsavo, Kenya (July 2007)

A research program that I am now concluding focused on the Tsavo lions, infamous as man-eaters a century ago but more remarkable because many of them lack manes. In a series of papers, I have explored the morphology, genetics, behavior, and ecology of lions in SE Kenya with Samuel Kasiki (Kenya Wildlife Service) and Alex Mwazo (Kenyatta University), Roland Kays (NY State Museum), Jean Dubach (Loyola University), Justin Yeakel (UC Santa Cruz), and others.  Our aim has been to understand this distinctive and environmentally-plastic trait (manelessness) at genetic, hormonal, histological, anatomical, and behavioral levels. Concurrently, we gathered information to mitigate the impacts of lion depredations on livestock to ensure their continued survival and the preservation of their habitats. Until 2009, this project had the help of volunteers from the Earthwatch Institute.

As detailed in Students, interactions with undergraduate and graduate students enrich, extend, and complement these studies. All four research arenas offer opportunities for student research projects and post-graduate collaborations alike.