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Good Fences Make Good Neighbors:
The Efficacy of Predator-Proof Boma Fortification in Reducing Human-Lion Conflict in Kenya
Alexandra E. Sutton, Nicholas School of the Environment, Duke University (Alexandra.Sutton@Duke.edu)
PROJECT GOAL
To find evidence for or against the use of boma fortification as a means of preventing lion
depredation of livestock, thereby avoiding human-lion conflict and preventing retaliatory killings.
INTRODUCTION
Human-wildlife conflict is one of the greatest challenges facing large mammal conservation
worldwide. In East Africa, the ranges of large predators like lions often overlap with human
landscapes, and human-wildlife conflict arises most often in the form of livestock depredation.
Because depredation poses a significant threat to livelihoods, it often leads to the retaliatory killing
of predators – a major conservation challenge.
Over the past five years, conservationists working throughout East and Southern Africa
have sought to reduce the threat posed by large predators by implementing projects to help fortify
or redesign livestock enclosures (“bomas”). Several organizations have reported anecdotal success in
predation reduction through the creation of these fortified bomas; however, these structures can
vary greatly in style, material, size, etc., and to date, no published studies have examined these
variations’ quantitative impacts.
Although boma fortification currently appears to be a cheap, sustainable, and humane
solution to predator conflicts in East Africa, the lack of scientific evaluation has limited its perceived
legitimacy. My study sought critical evidence to support the widespread use of boma fortification as
a conservation intervention, and my results are detailed in the following report.
About the Maasai Mara
One of the last, most beautiful wild landscapes of
East Africa, the Maasai Mara holds a special
significance – both environmentally and culturally –
for the people of Kenya. It is home to more than
1,000 wildlife species, as well as Kenya’s last
stronghold of lions – a population estimated to
number just a few hundred. The Mara is also home
to the Maasai, a semi-nomadic, pastoral people for
whom cattle are a critical part of both livelihood and
cultural legacy4.
This overlap in human and lion activity has
led unfortunately to conflict: losing livestock to
hungry lions threatens Maasai economic well-being
and incites the retaliatory or preventative killing of
lions123. Reliance on cattle is so high in the heavily
rural county that surrounds the Mara that less than
8% of all residents live in urban centers, and the
cattle-owning populace possesses more than three
million heads of livestock in total4.
Figure 1. Map of Kenyan National Reserves and Parks
What is a Boma?
Bomas are fenced livestock enclosures, meant
to keep cattle secure during the night. Over
the past decade, several conservation
organizations have worked to reduce the
potential threat of livestock loss by helping
cattle owners fortify or redesign their bomas;
the Anne K. Taylor Fund has been one such
organization at the forefront of this work.
Now, after five years of work and over 425
completed bomas (Figure 2), my evaluation
has confirmed what the Fund has long claimed
– that these bomas are indeed effective at
stopping livestock loss and breaking the
predation-retaliation cycle5. The AKTF project
can therefore become a model for the
widespread use of boma fortification as a
cheap, sustainable, and humane solution to predator conflicts in East Africa.
Figure 2 A fortified boma with protective vegetation, built by the
Anne K. Taylor Fund.
1
Ogada, M.O., Woodroffe, R., Oguge, N., and Frank, L.G. 2003. Limiting depredation by African
carnivores: the role of livestock husbandry. Conservation Biology 17: 1521 - 1530.
2
Kolowski, J.M., and Holekamp, K.E. 2006. Spatial, temporal, and physical characteristics of livestock
depredations by large carnivores along a Kenyan reserve border. Biological Conservation 128: 529 – 541.
3
Hazzah, L. Borgerhoff Mulder, M., and Frank, L. 2009. Lions and Warriors: Social factors underlying declining
African lion populations and the effect of incentive-based management in Kenya. Biological Conservation 142:
2428 – 2437.
4
Kenya Open Data. 2009. Livestock population by type and district. Accessed from https://www.opendata.go.ke
5
Sutton, A. 2013. Unpublished data.
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ON THE GROUND IN KENYA
My work coincided with beginning of
the rainy season in the Mara, an
occurrence that earned me the Maasai
nickname of ‘Nolari’ (the one who
brings the rain), and also offered a
fortunate glimpse into the landscape
of conflict in the Mara.
The rainy season appears to be
invariably a period of heightened
human-lion conflict in the area,
perhaps because climatic and
vegetation shifts drive prey animals to
migrate and make hunting more
difficult for predators.
Figure 3 From left: Elias Kamande, Myself, Kimoro Sakui
UNCOVERING THE ANSWERS
In order to understand the effectiveness of
fortification, I needed to compare annual
predation rates (i.e. the number of cattle,
sheep, and goats lost per year) at fortified and
unfortified bomas, and I needed to talk to
homeowners to find out how many animals
they’d lost in the past 12 months. Spotty
records and some limited reports were
available to help provide correlating evidence
for the worst attacks – particularly memorable
ones (such as the gentleman who lost 89 goats
in one night) were both recorded by park
managers and burned into the collective
community memory. But for smaller, more
everyday attacks, I had to rely on people’s
knowledge – so I limited my focus to a 12month retrospective (i.e. “How many sheep
have you lost in the last year to lions?”) I also
gathered data on people’s general wildlife
knowledge by having everyone take a picture
identification test of wildlife – which turned
out to be the most popular part of the
interview!
Figure 4. A summary of trends found in surveyed bomas.
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Figure 4 Conducting Wildlife ID Tests
Figure 5 Handwritten park ranger records of predation
So Do the Fences Work?
Preliminary results indicate that fences definitely help! In fact, in addition to reducing predation
overall, they have a prophylactic impact that we’ve nicknamed the ‘smoke detector effect’ – even
when they may not prevent the fire from ever starting, they still minimize the impact and cut down
on losses. In fact, my data shows that bomas with a fortified fence experienced a lower average
annual loss of sheep and goats (p=0.0178) than those without one. That’s great! But what stands out
more is the fact that bomas with a fortified fence never experienced extreme predation events
(‘surplus kills’ or ‘killing sprees’) on sheep, goats, or cattle. By contrast, about one quarter (23%) of
unfortified bomas had at least one spree (over 40 animals lost in one event) over a 12-month period.
Knowing that fortifying bomas is an effective method to break the predation-retaliation
cycle, I next wanted to understand whether they might also be a cost-effective method. To determine
this, I collected full financial data from the Anne K. Taylor Fund and worked with a collaborator
specializing in environmental economics to run a few numbers. These are presented below:
The Cost of Building the Average Boma
The total cost of a fortification is
approximately $863.15 per boma in
Kenya. The net cost borne by AKTF,
after contributions from our partner
organizations, is approximately $600. The
exact cost of building a single boma
varies, but on average requires nine (9)
rolls of 8’ chain link wire, at a cost of
USD$65 each; ten (10) sheets of
hammered metal, at a cost of USD$6
each; one (1) roll of galvanized wire, at a
cost of USD$65 each; twelve (12)
anchoring posts, at a cost of USD$6 each;
and one (1) metal door, at a cost of
USD$45 each. Construction requires an
average of twelve (10) hours of work by at
least two adults, and typically takes place
in phases over two or three days.
Figure 5 A fortified cow boma, without a hammered metal roof.
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How To Build An Ideal Boma
First, builders must dig trenches at least 15 cm deep to anchor and bury the wire; this depth prevents
hyenas, honey badgers, and some leopards from digging under the fence. Next, builders must dig
four holes at least 30 cm deep in which to anchor the corner posts, against which the fence wire will
be tightened. Once anchor posts and wire are in place, additional posts (eight, on average) will be
used to strengthen the fence.
Builders must then run two lines of galvanized wire around the fence; one at approximately
10 cm from ground and one at approximately waist-height. These deter lions, buffalo, and other
large animals from using their body weight to weaken the fence. Builders can then add metal roofing
to sections of the boma which will house calves, sheep, and goats – the smaller nature of these
animals make them easier prey for leopards, which typically kill after leaping into bomas; a metal
roof prevents leopards from gaining access. Last, boma owners have the option of planting thorny
bushes around the fence perimeter; this adds another layer of protection, preventing visual contact
between predators and cattle.
The Efficacy of Fortified Bomas
In the Mara North Conservancy (MNC), fortified bomas cut predation by 30% for cows and 74%
for sheep and goats – reducing the average annual livestock lost from seventeen (17) to five (5). In
the Trans-Mara Region (TMR), they cut predation by 41% for cows and 34% for sheep and goats –
reducing the average annual livestock lost from eleven (11) to seven (7).
Using a discount rate of 15% and assuming a fortified boma lifespan of 5 years, the cost of
building a boma leads to returns on total project investment of 409% in the Mara North
Conservancy and 218% in the Trans-Mara region, given the average cost of a cow (USD$450) and
the average cost of a sheep or goat ($80) saved from loss.
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These ROIs could be greatly increased if the bomas’ efficacy were improved; the addition of
a monitoring component would ensure consistency in boma construction, improve homeowner
capacity for repairs, and thus extend the life of the structure such ROI would increase from current
levels (409% in the MNC and 218% in the TMR) to 519% in the MNC and 456% in the TMR.
THE FUTURE OF THE BOMA PROJECT
So what’s next for human-wildlife peacekeeping in the Mara region? Certainly, the project to this
point has been a resounding success and is cause for celebration as a conservation victory. But is this
model of charitable intervention sustainable in the face of increasing development in Kenya?
The shifting landscape of donations and development in Kenya have produced greater
pressure to shift from subsidization approaches to self-sufficiency initiatives, migrating responsibility
for resolution & improvement to the members of the community which it impacts. For the Boma
Project, that would mean identifying opportunities for Maasai microfinance; shifting ownership of
the construction, design, supply chain process to local community members; and providing support
and mentorship to the development of small-scale business ventures. Some examples are below:
Sourcing Boma Materials
The metal doors used in fortified boma construction are produced by local manufacturers,
and are made of recycled water drums – this provides support for local businesses and has the
potential to become a small-scale microfinance project in itself. The necessary treated bluegum posts
are sustainably produced in Nairobi and shipped to the Mara; at present, these are donated
generously by the Eden Wildlife Trust. And although AKTF supports the use of living plants as part
of the fence structure, it does not provide seedlings or adult plants to boma owners; both the
bluegum posts and plant operations hold potential to develop into small-scale Maasai businesses.
MY FUTURE IN KENYA
As a million travelers before me, I’ve fallen in love with Kenya and the incredible natural bounty of
the Mara region and the boundless hospitality and kindness of Kenyans. I’ll be returning to the Mara
for one more field season (hopefully in the summer of 2014) before completing this work.
As I look forward to graduation, I’m planning for one further field season and a series of
visits related to the launch of my microfinance enterprise, Kedge, which would aim to support small
business entrepreneurship among rural communities through business education and conservation
literacy training. If you’d like to support Kedge or help us build partnerships throughout East Africa,
we can always be reached by email (info@kedgeconservation.com) or Twitter (@KedgeConserv).
ACKNOWLEDGEMENTS & APPRECIATION
Obviously, none of this work would be possible without the very generous support of the following:
The Maasai communities of the western Mara, whose unparalleled generosity, openness, and kindness made
my work possible.
Anne Kent Taylor & Jim Taylor (Anne K. Taylor, International) and the staff of AKT Int’l and the Anne K.
Taylor Fund, especially Mary Zrubek, Bernie Githigi, Felix Munyao, and Elias Kamande.
Marc Goss, Madeline Goss, James Hardy and the fantastic staff at the Mara North Conservancy, as well as
Brian Heath & the hardworking staff of the Mara Triangle.
Joss Kent (&Beyond) and the incredible staff of Kichwa Tembo, especially Tony Adams, Les Carlisle, Jason
King, Magdelle Dempers, Stanley Mpakany, James Chege, and Rufus Kimani.
Geoffrey Kent (Abercrombie & Kent) and the fantastic staff of Sanctuary Olonana, especially Maurice Simiyu
& Christine Rukwaro.
Stefano & Liz Cheli (Cheli & Peacock) and the amazing staff of Elephant Pepper Camp, especially Patrick &
Sophie Dessy.
And a very special thanks to the great auto maintenance team led by Brian Gow at the A&K workshop.
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