Stephens & Foraging - Behavior and Ecology - Chapter 14 ppt

14
On Foraging Theory, Humans, and
the Conservation of Diversity: A Prospectus
Michael L. Rosenzweig

14.1

Prologue

The Tertiary is over. The world of our remote ancestors has nearly
vanished. No nostalgia can save it; no yearning can restore it. We have
entered the geological era of Homo sapiens. Like it or not, we are the
boss.
We take what we want where we want it. We take land and sea, water
and air. We corral a stupendous fraction of the earth’s productivity and
mineral resources (Vitousek et al. 1997). With clever apparatuses, we
adapt to an unprecedented variety of environmental conditions, turning
them all into a semblance of the semiarid tropical climate in which our
physiologies evolved. Where we have not yet learned to live, we dream
of living. No previous era in the history of life has seen our ilk.
We have not eradicated in ourselves the basic, acquisitive nature that
natural selection insists upon in all successful life forms. That was the real
flaw of Marxist thought: it dreamed that Man without unfulfilled needs
would become generous. But, while a competitive and exploitative
Mankind may confound socialist economics and disappoint theologians
and moralists, it looms as a death warrant for every ecosystem whose
resources we expropriate. The rest of life can do little to thwart us.
But we can do something. We can abstract. We can contemplate
what we are doing. We can even predict the consequences. And we can

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find alternatives. Our plans have already restructured the world of life unintentionally. Why should they not do so on purpose? And who is to say
whether that purpose need be malevolent or malicious?
Fortunately, evidence indicates that we would rather share our world with
other species, conserving at least patches of it as relics of our environmental
heritage (Kellert and Wilson 1993; Wilson 1984). We have developed a worldwide network of set-asides—national parks, wildlife refuges, nature reserves,
and the like. We restore ourselves in them, spending prodigious quantities of
money and time. We join and support organizations devoted to them and to
the preservation of specific species in them. As much as we can afford to, we
surround ourselves with nature (Orians 1998). We install parks in our cities
and towns. We tend our lawns; plant herbs, trees, and shrubs; and pay extra
for property that allows us to do so.

14.2

Introduction

This chapter assumes that we humans do care about preserving natural diversity. It will explore the ways in which foraging theory and studies of foraging may improve our ability to make a difference. Much of it will be a call
for focused research, rather than a synthesis or a review of what has already
happened.
The chapter has several themes. It views human beings as sophisticated
products of natural selection. We ourselves are optimal foragers. In that context, it asks how we should go about setting the rules for set-asides. It also
wonders about what people really want from nature. It notes the promise of
studies of foraging and habitat selection. These studies can reveal the underlying relationships among species, and they can also provide environmental
indicators and tools for further study. And the chapter calls attention to a
relatively new strategy for conservation, reconciliation ecology. Reconciliation ecology makes use of sophisticated methods for natural history research
in order to develop new habitats in which humans and the natural world can

coexist (Rosenzweig 2005).

14.3 Human Beings as Optimal Foragers

Can anyone imagine that selection has refined the foraging abilities of insects
and fish, spiders and reptiles, birds and mollusks—not to mention mammals—
but not of Homo sapiens? Yet I have sat on committees with first-rate minds


On Foraging Theory, Humans, and the Conservation of Diversity

in various human-oriented sciences, and I have heard their well-meaning lips
deny that human behavior has any genetic roots. Certainly, their opinions
stem from goodwill, from a determination to see that genetics is never again
used to oppress people. However, their reticence to view people as products
of natural selection can actually hurt people by negating the good that our
institutions and understanding can do. On the other hand, if we admit that
people do have innate tendencies toward certain behaviors, then we and our
world stand to gain.
Recent evidence presented by Morris and Kingston (2002) strongly reinforces the notion that people exhibit behaviors consistent with a long history
of selection to improve foraging abilities. Morris’s work depends on Fretwell
and Lucas (1969), who pointed out that individuals, when faced with choices
of habitats (see box 10.1), will distribute themselves and their activities so that
no individual can gain an advantage by unilaterally changing its habitat choice.
Their work established the connection between population size and habitat
selection because as population grows in a habitat, the advantage gained from
foraging there declines. Sometimes optimal habitat choices result in what
Fretwell and Lucas termed “ideal free distribution.” Conforming to the ideal
free distribution often means that more individuals use the richer habitat.
Human Isodars

Isodar plots, invented by Morris (1987), help us to compare the properties of
different habitats (see box 12.1). In an isodar plot, each axis is the population
size of a species in a specific habitat. Each point is the set of a species’ habitatspecific populations at a single time. The line fitting those points is the isodar.
Human population distributions conform to an isodar (Morris and Kingston 2002). Urban and rural populations form its axes. In 1995, in 154 nations,
large and small, rich and poor, authoritarian and free, people lived in urban
and rural habitats in proportions that follow it. Of course, there is statistical
noise in the relationship, much of which can be accounted for by subdividing
nations into high and low per capita CO2 emissions. In the 76 nations with
emissions below the median, more people lived in rural habitats than in urban
ones. In the 73 nations above the median, about half the people lived in rural
habitats.
The point is that the human isodar exists. People follow innate rules of
density-dependent habitat selection that manifest themselves in all societies.
No one claims that the isodar proves people achieved an optimal habitat distribution in 1995. The isodar of 1995 may reflect conditions of a past era and
be quite inappropriate for 1995, but it exists.

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Adjusting Costs and Benefits of Nature Reserve Exploitation

In yesterday’s world, people made their living by harvesting resources from
the bounty of environments resembling today’s set-asides. Thus, today’s nature reserves seem, to the very core of the human psyche, to be patches of beckoning abundance in a sterile world. Morris’s isodar comes to remind us that
our evolved psyches urge us to not let them lie unexploited!
Sometimes such urges afflict very rich individuals. The very rich may visit

a set-aside and find it releasing passions in them that perhaps they never knew
they had. Beyond better education and strict law enforcement, there’s not
much we can do to tame their atavistic selfishness.
Sometimes the urges are collective, infecting rich organizations of people
hell-bent on taking the last 1% of something. Although they are already making lots of profit, simple institutional greed moves them—probably reinforced
by groupthink ( Janis 1972). And what they do is rarely illegal; they buy legality with their profits. Harnessing the power of foraging theory cannot stop
them directly, although it may create a world in which their behavior loses
its profitability by virtue of an excessive cost in the courts of public opinion.
But sometimes very poor people, who happen to live nearby, threaten
set-asides. This scenario applies to many of the world’s richest set-asides. Exploiting such set-asides could make a great deal of difference in the lives of
their poor neighbors, at least for a time. In these cases, we must understand
people as foragers, which is to say, as rational beings behaving intelligently
to improve their lot. The set-aside is a resource-rich patch next to an impoverished one. It will attract foragers in substantial numbers.
Policymakers and conservationists know full well what they must do to
protect their country’s set-asides. They need to develop incentive-compatible
systems for reconciling human behaviors with conservation efforts (Gadgil
and Seshagiri Rao 1995). That is the strategy. Its tactics involve adjusting the
cost and benefit parameters of those behaviors. But many policymakers have
shown little imagination. Ignoring benefits, they act only to increase the costs.
Fines and prison terms for poaching go up. More wardens enforce the restrictions, with increased powers to injure, and even to kill, suspected violators.
Sadly, the proponents of such policies have greatly underestimated the
value of the contraband to poachers. So such policies generally fail, except
in rich countries where poachers gain comparatively little by their activities.
Escalating the cost of poaching usually leads poachers to increase their prices—
an enhanced reward to compensate them for the greater risks and higher costs.
Most perversely, such increases could even increase poaching, because people,
acting like perfectly sane foragers, ought to shift their activities to a resource
that has become more lucrative. (Ask yourself, how many narcotics dealers

On Foraging Theory, Humans, and the Conservation of Diversity

would there be if greengrocers sold hemp and coca leaves at the price of cabbage?) Hence, increasing the cost of poaching may also increase its benefits
and nullify some, all, or even more than the increase in costs.
Consider the following case from Zimbabwe (Muchapondwa 2002b):
Rhino . . . cause minimal damage to agriculture. . . . The virtual elimination
of the black rhino [in Zimbabwe] is due to the high value of the horn. . . . [Despite] the imposition of a complete embargo on trading in rhino parts and derivatives . . . the illegal trade has flourished. The [government] had increased its
surveillance.

Anti-poaching operations assumed the proportions of moderately intensive
anti-insurgency warfare, employing the same tactics and equipment, including automatic weapons, sophisticated radio and intelligence networks, vehicles, boats, helicopters, and fixed-wing aircraft. Law enforcement was, however, tackling the effect rather than the cause of the problem. Poaching was
motivated by the high price of rhinoceros horn on the illegal market, which
had been handed a monopoly by the prohibition on legal trade. Protecting
wildlife by giving it a value benefits landholders, often the rural poor, whereas
trade bans, if they are effective, destroy this benefit.
In a few cases, cost-increasing tactics have eliminated the benefit of wildlife
almost entirely. This negative tactic can work if it prevents the sale of the resources. When no one, not even a Russian nobleman or a Park Avenue matron,
may own a sea otter coat, sea otter populations rebound. When international
traffic in ivory becomes illegal, as does the sale of ivory artifacts, elephants
stand a chance.
Nevertheless, in the past 10 or 20 years, a fundamentally new kind of policy has surfaced. Instead of increasing the costs or reducing the benefits of
poaching, this policy seeks to increase the benefits of alternative non-poaching
activities to people who live close to set-asides. It replaces bureaucratic regulations with rewards (Gadgil and Seshagiri Rao 1995).
Residents may train to become wardens themselves, or they may learn
how to participate in managing the set-aside. Often hunting or ecotourism
provides the rewards. Residents become guides or involve themselves in the
supporting industries, such as food and lodging. Conservation can be profitable (Daily and Ellison 2002).
Yet, for all their benefits, ecotourism and trophy hunting are limited
industries. To make reserves successful in the long term, we must reject the
idea that we can manage reserves as hermetically sealed ecosystems. Instead,

we must learn how to integrate set-asides with other means for humans to
earn their livelihoods.

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In that regard, David Western’s approach in Kenya has been particularly
fruitful (Western 2001). It uses the set-asides to enrich economic opportunities
in surrounding areas. Outside the reserves, people engage in a wider variety
of legal and profitable activities than inside. Yet residents understand that
profits outside the reserve depend on the creatures within it. The result: areas
around reserves receive overflows of wildlife from the reserves themselves,
actually extending the ranges of the species in the reserves.
Policymakers can succeed if they take into account the intimate connections that nearby residents have to set-asides and to the conservation of wild
species. Again, consider the lessons learned in Zimbabwe (Muchapondwa
2002b): Because they received money from wildlife exploitation, the Mahenye community agreed to move some of its villages away from a portion of
its land, a small, fertile patch of excellent wildlife habitat. Most of the wildlife
were elephants (Loxodonta africana). The Mahenye got more from selling the
right to hunt an elephant than they lost through the crop losses they incurred
by the move. The community used the money for local infrastructure: a
school, a road, a borehole, and a grinding mill. As the community’s earnings
grew because of elephant conservation, it allocated more land to wildlife.
Then the community itself started to control poaching. People were reluctant to kill wildlife even to protect their crops. Finally, the community began
to use some of the wildlife profits to compensate its members for crops losses.
It had decided to use the wildlife to increase its income.
Now, the people of Zimbabwe are not crass materialists. Indeed, they are

poor, but they mix their respect for the profitability of elephants with a love
for them. Elephants are a destructive nuisance to them, yet they are actually
willing to pay something to preserve the elephants near them (Muchapondwa
2002a). Indeed, we must never expect people to be cold-hearted optimal
foragers. They will always combine their implicit foraging calculations with
a little bit of inexplicable mystery and aesthetics.

14.4 People as Bayesian Foragers: Shifting Baselines

As nature retreats, people rapidly accustom themselves to whatever nature
remains. They cannot imagine what they are missing and rarely even try.
The depauperate environments with which we have surrounded ourselves
during the past few centuries have deeply eroded our horizons. We expect to
see nothing more than house sparrows and a few house plants. When, at last,
we do take a trip to a national park or reserve, most of us depend on its wild
things being in predictable places at predictable times. We have disconnected


On Foraging Theory, Humans, and the Conservation of Diversity

ourselves from the world of nature and have learned to prefer it that way.
Nature makes us uneasy, even fearful.
But primarily, nature no longer holds promise for us. No promise of abundance. None of sustenance. Having conquered nature, we have lost both
our esteem for her and our faith in her wealth. We have stopped believing in
her robustness because we can no longer remember it.
Daniel Pauly (1995) calls this failure of intergenerational memory “the
shifting baseline” syndrome. He illustrates it with a story about the grandfather of one of his colleagues. In the 1920s, the grandfather was a fisherman,
drawing up his catch of mackerel from the waters of the Kattegat, an arm of the
sea between Denmark and Sweden. Poor grandfather, it seems, was plagued
by numerous, economically useless bluefin tuna that entangled themselves in

his nets! Today, of course, bluefin tuna are rarely, if ever, seen in the North
Sea. In those few places in the world’s oceans where their dwindled schools do
remain, experts meticulously monitor their population biology, and nations
carefully apportion the right to fish them. Their flesh sells for a fortune.
Jeremy Jackson (2001) found evidence of our shifted baseline in the Caribbean. Once, great maritime powers added remote island systems to their
far-flung empires because the abundance of turtles supported by those islands
helped to provender their sailing ships. In the Caribbean, a few hundred years
ago, green turtles were so abundant that ships struck vast shoals of them and
sank! Green turtles, manatees aplenty, and teeming multitudes of man-sized
herbivorous fishes kept Caribbean sea grasses closely cropped. Today, sea
turtles of all species are rare or threatened.
Our baseline expectations have shifted in fresh waters, too. Consider an
edible mussel, the giant floater, Pyganodon grandis. Living on the bottoms of
some North American freshwater streams and lakes, it can quickly grow to
be about 25 cm long. Ten generations ago, it was so abundant that in many
places in the middle of the continent, it was a staple food. Brandauer and Wu
(1978) estimate its population densities to have been six to twelve per square
foot. In contrast, today’s populations of giant floaters, like the majority of
North American freshwater animals, have nearly vanished. In the waters of
Colorado, they exist at population densities of less than one per hundred square
feet in the few sites where they still survive at all (Liu et al. 1996). Thus, they
are more than a thousand times scarcer than they were a century or two ago.
And then there is the principal pigeon of North America, the passenger
pigeon. The last one died in the Cincinnati Zoo in 1914. Her ancestors had
numbered in the billions just a century before (Schorger 1955). Professional
pigeoners shot them in hordes and supplied the cities of the eastern seaboard
with fresh pigeon meat for a century. But now they are gone, and their world

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is gone, and we can never imagine what it was like. That is the point. Our
ancestors lived on an earth where they took nature’s abundance and diversity
for granted. We live on one where we take her fragility and poverty for
granted. We simply have not experienced enough to know how different she
could be.
And, indeed, we cannot bequeath our memories to our children. If they
could but see what we saw when we were younger, they might be outraged
at what they have lost. Thus, the human species as a whole is like a Bayesian
forager, updating its expectations and estimates, generation after generation,
of the probabilities of coming across habitats of each type and quality.
From the perspective of natural selection, it makes as little sense to defend
a habitat that has ceased to exist as it does to search for one that contains an
abundance of a perfect, but imaginary, resource. No conservation strategy can
have long-term success if it merely tries to restore what a few doddering older
members of our species recall with fondness. A truly victorious conservation
plan will find a way to up the ante, to shift the baseline in the positive direction.

14.5 Reconciliation Ecology

Gordon Orians has dubbed the world we are creating “The Homogocene.”
Orians chose this word to reflect the breakdown in barriers between biogeographic provinces (Mooney and Cleland 2001). Nevertheless, it is an apt
designation for our new world. The Homogocene threatens to be a time of
mass, persistent loss of diversity, and not just because the world is losing its
biogeographic boundaries—a minor threat in my view (Rosenzweig 2001a).
To maintain diversity, we shall need to promote a sea change in our strategy

of conservation.
Our current strategy is “reservation with restoration.” We set aside what
we can as reserves, and we attempt to repair degraded environments until they
support some semblance of the natural flora and fauna (Rosenzweig 2003a).
The most sophisticated of these efforts—the hotspot tactic—recognizes that
not all areas of the world are equally valuable as set-asides. Some contain
many more species than others; some contain species found nowhere else. The
world’s 25 silver-bullet hotspots constitute only 1.4% of its land area, but 44%
of its vascular plant species and 35% of its vertebrate species are contained entirely within that 1.4% (Myers et al. 2000). (One guesses that they also contain
a large proportion of its invertebrate species, but that proportion is unknown.)
Reservation with restoration has slowed the bleeding. But it relies on a
static view of habitats and their distributions. Global warming may vitiate all
current reserves. And even if we do somehow manage to get that problem


On Foraging Theory, Humans, and the Conservation of Diversity

under control, both current biogeography and paleobiogeography leave no
doubt that area is as fundamental a property of an ecoregion as its precipitation
and temperature. Shrunken ecoregions can preserve species diversity only in
direct linear proportion to their size. In other words, lose about 95% of an
ecoregion and expect to lose about 95% of its species diversity (Rosenzweig
2001b).
However, not all species require set-asides. The German language calls
those that do, kulturmeider (culture avoiders), and those that do not, kulturfolger
(culture followers). A new strategy of conservation biology, reconciliation
ecology, seeks to convert kulturmeider into kulturfolger. As the first step in this
process, reconciliation ecologists study the habitat and resource requirements
of species. Next, they design new human-occupied habitats that offer the
requirements for these species to thrive (Rosenzweig 2003b). Reconciliation

ecology bulges with opportunities for the behavioral ecologist.
Not Your Grandfather’s Natural History

Research for reconciliation ecology often begins with natural history. Not
old-fashioned natural history, but natural history informed by modern techniques, modern theory, and conservation priorities. When reconciliation ecologists target a species for preservation, they study it carefully with a view
toward determining what it needs to succeed in the natural world. Finally,
they alter a human habitat in accordance with those needs. Notice: reconciliation ecology alters the habitat, rather than setting it aside in a reserve. Two
examples should serve to illustrate how easy this can be in some cases, and
how difficult in others.
The easy case is a bird, the loggerhead shrike (Lanius ludovicianus). Populations of this species and many others of its family are declining and disappearing over much of their range (Yosef and Lohrer 1995). Yet one imaginative
person quickly discovered a way to reverse the trend.
Ruven Yosef began by observing the natural feeding behavior of the loggerhead shrike in southern Florida. From its perch on a fence or in a cabbage
palm, a foraging shrike would scan its immediate surroundings for the large
invertebrate prey that form the bulk of its diet. It would pounce only if that
prey lay within a certain restricted distance (6.5 m from a fence; 9.3 m from
a palm) (Yosef and Grubb 1992). One may speculate that this attack distance
reflects a well-adapted forager. Foraging from farther away might give the
targets so much time to react that they would too often escape. Marginal
benefit would fall beneath a critical threshold, and natural selection would
force the shrikes to ignore prey beyond the critical distance. Whether or not
this speculation proves true, the foraging behavior is real, and the biologist

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can work with it (see also Cresswell and Quinn 2004 for the hunting tactics

of sparrowhawks on redshanks).
Yosef mapped shrike perches on a working cattle ranch and discovered
that, despite abundant prey, much of it was unavailable to shrikes because
it was beyond their attack distance (Yosef and Grubb 1994). Yosef installed
simple wooden posts in the patches of pasture that lacked perches. The shrikes
responded immediately. Within the first spring, territories with the extra posts
shrank an average of 77%, and the loggerhead shrike population increased
60%. The smaller territories also helped nestlings survive. Parent birds in
smaller territories had 33% more successful clutches than controls, and raised
29% more chicks per successful clutch (Yosef and Grubb 1994).
South African ecologists have successfully applied Yosef’s method to fiscal
shrikes (Devereux 1998). German biologists used a similar method to restore
a population of great grey shrikes (Lanius excubitor), in which small piles of
rock took the place of the posts (Schă n 1998). Van Nieuwenhuyse (1998) is
o
applying a similar approach to populations of red-backed shrikes (Lanius collurio). Adding hunting perches to land already used for agriculture tweaks the
habitat only a bit and does nothing to reduce its use by humans. It is also cheap.
The natterjack toad (Bufo calamita) in England proved a more difficult case.
To learn how to rescue this threatened species, a veritable company of some
50 researchers and their assistants spent 25 years refining their understanding
of natterjack toad natural history (Denton et al. 1997).
This team first focused on characterizing the natterjack’s niche. The natterjack is a pioneer amphibian. It lives in open vegetation surrounding eutrophic
pools of coastal dunes or oligotrophic pools of inland heaths. Unlike its chief
competitor, Bufo bufo, it burrows in sand. When foraging at night, it operates
at a body temperature 1.4◦ C higher than B. bufo, and it loses weight if forced
to forage in dense, cooler vegetation. This helps to explain why its population
declines when tall vegetation—such as birch, gorse, and bracken—begins to
invade and shade its habitat. The increased shade also lowers the water temperature of the pools, slowing the development of natterjack tadpoles and
subjecting them to damaging competition from B. bufo.
The company studied many other aspects of natterjack ecology. They

looked at a unicellular gut parasite, Prototheca richardsi, and at predation by
salamanders, Odonata, water beetles, water bugs, and Notonecta larvae. They
studied pond chemistry and water quality (chlorides, sulfates, orthophosphates, ammonia, iron, sodium, potassium, calcium, magnesium, alkalinity, conductivity, color, and turbidity). They even studied pond depth and the contour of pond slopes.
Simply knowing the detailed natural history of B. calamita has supported
the reestablishment of many healthy natterjack toad populations (Denton et al.


On Foraging Theory, Humans, and the Conservation of Diversity

1997). The toad biologists increased grazing to maintain the early stages of
succession. For the same reason, they cleared dense vegetation. They fought
acidification by adding Ca(OH)2 to natterjack ponds every year or two, or by
scraping the sulfate-rich silt from their bottoms. They removed some B. bufo
to give the natterjacks a fair start. And they built some 200 new ponds, not too
deep—for that would have encouraged invertebrate predation—and not too
steep, and sometimes lined with concrete to fight acidification. They used old
bomb craters and active golf courses. At all sites with new ponds, B. calamita
used at least one and usually most within a year or two. The new ponds reestablished, rescued, or increased natterjack populations at two-thirds of the sites.
Sophisticated Preference Studies

We can do better than to discover what a species needs. Using sophisticated
foraging studies, we can actually discover what a species wants. Many ecologists continue to believe that a proper way to do this is to develop a utilization
distribution for a species; that is, to accumulate information about the resources and habitats used by individuals and then rank these according to the
intensity of their use. A slightly more sophisticated version of this method
involves comparing these intensities with the proportions available in the
natural environment. For example, habitat used 10% of the time by a species
and extending over only 5% of its range would be viewed as twice as beneficial
as a habitat used 50% of the time that covers 50% of the range.
But foraging ecology teaches us that we can rely on none of the above methods (Rosenzweig 1981). Observing where a species lives and what it does
depicts merely its realized niche. Its fundamental niche may be quite a bit

larger. Moreover, competitors and predators can profoundly affect the proportional use of habitats within the realized niche, so proportional use data
may be an unreliable guide to the relative value of habitats. In the worst-case
scenario, a habitat that is heavily used by a species may not even be part of
its fundamental niche. It may instead harbor only sink populations of that
species. The largest populations of the annual Cakile edentula grow in such
sink habitats (Keddy 1981).
Foraging ecology allows us to compare and rank a species’ habitats and
resources more reliably. If one assumes that natural selection produces competent individuals, then one can study their choices to discover what benefits
them most. Microeconomists often use such an approach to human behavior,
calling it the study of “revealed preference” (see chap. 6). Students of animal behavior may estimate revealed preferences using the worldview of the
ideal free distribution (Fretwell and Lucas 1969). They may equally well use
patch use theory, which Charnov (1976b) introduced to ecology. Charnov

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asked how long a forager should remain in a patch—its giving-up time.
Brown (1988) extended patch use theory by asking what foraging conditions
in a patch should prompt a well-adapted forager to leave it—the giving-up
density (GUD) of its resources (see box 13.2).
My colleagues and I use these ideas to structure our research programs, and
our results have often surprised us. If a species experiences strong interspecific
competition, then members of the species may use secondary habitats almost
to the exclusion of primary habitats (Abramsky et al. 1990; Reynoldson
1983). Using extensions to ideal free distribution theory (see chap. 12), we
can compare disparate rewards and threats, determining, for example, that

the advantage of foraging without the threat of predation from barn owls
has about ten times the effect on a foraging gerbil’s behavior as does the very
important advantage of foraging in semi-stabilized sand (Abramsky et al.
2002a, 2002b). Previously, with similar field experiments, colleagues had
shown that the advantage of semi-stabilized sand was very subtly linked to
time (i.e., sunset to midnight) as well as to space (Kotler, Brown, and Subach
1993; Ziv and Smallwood 2000). Reconciliation ecologists will need just this
sort of knowledge to do their jobs.
We need to find out about our own (that is to say, human) habitat preferences, too (Orians 1998). Layer upon layer of civilization may obscure human
preferences, but they are nonetheless real; we must take them into consideration when tinkering with the habitats in which we live. Human behavioral
ecology remains an inchoate science, and I cannot foretell the extent to which
optimal foraging principles will be useful to it. Perhaps the answers are already available, but lie embedded in the literatures of marketing, landscape
architecture, and interior decoration.
In any case, reconciliation ecology does not seek to impose habitats on
people. For its designs to be successful, people will have to appreciate them.
It is one thing to establish a forest of shrike perches in a cow pasture, but quite
another to do the same thing in someone’s front lawn.
Studies of Guild Organization

Most of the reasons why conservation biologists need to know about community organization are perfectly clear. One cannot be a good steward without
being aware of the potential hazards to one’s charges. I believe that the great
difficulty with the hotspot strategy is that it pays too little attention to this
principle of stewardship. It tacitly assumes that things will always be the way
they are. Yes, we must save hotspots. But we cannot rely on them staying hot
without understanding what makes them that way. As I have already pointed
out, a species may be present in an area—even abundant there—despite having


On Foraging Theory, Humans, and the Conservation of Diversity

no source populations in it. In addition, a species may be absent because it
interacts with another species in some negative way. Thus, conservation of
diversity calls for intensive study of how population dynamics and species
interactions determine the geographic ranges of species.
Methods relying on foraging theory have done better than any others in
elucidating interspecies relationships (see chap. 12). First, they have enabled us
to predict the behavioral and dynamic consequences of several forms of guild
organization. At least one form of these predicted dynamics is baroque and
unique (the so-called “ghost of competition past” model). Yet the behavior
of gerbils in field experiments supports it (Rosenzweig and Abramsky 1997).
This suggests that studying foraging behavior in the field may actually help us
diagnose population interactions and may help to reveal how guilds of similar
species are organized.
The tactic of measuring giving-up densities (see chap. 13) has also proved
invaluable in dissecting guild organization (Brown 1989b). It helps us to compare habitat qualities. It determines the relative tolerances and efficiencies of
species. It provides an alternative way to look at the influence of predation
threats. Finally, GUDs have even reached across taxonomic boundaries, revealing the intimate interaction between gerbils and a common species of lark
(Brown et al. 1994).
Using Guild Organization

In addition to helping us save species in reserves, understanding guild organization may tell us which species need reserves in the first place. A species’
position in its guild may help us determine whether we can develop a reconciled habitat to save it.
Some species never live outside reserves. For example, Little and Crowe
(1994) showed that six species of South African birds were seen only within
reserves of fynbos. We will probably never discover a compromise habitat
that suits these species. They will always be kulturmeider and require relictual
habitats. They will probably resist reconciliation ecology forever.
Which species are kulturmeider? The example of the fynbos birds tells us
that taxonomy provides no clue. Species found only in reserves have close
relatives that live elsewhere. But the lessons of optimal behavior studies for

community organization may well provide a clue.
Tolerance-Intolerance Organization

Methods derived from foraging models (including optimal habitat selection models) have focused our attention on “shared preference” community
organization (also termed “tolerance-intolerance” organization) (Rosenzweig
1991). In shared preference organization, species divide a quantitative niche

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axis; that is, an axis whose values differ merely because the measure of a
single variable changes. All species do best at a certain value of this measure
(frequently, the largest possible value). But species differ in their ability to
dominate habitats representing the best portion of the axis. In the simplest
case, one species, often because it is the more efficient forager, is more tolerant
of the poorer habitats along the axis. The other, the intolerant species, requires the richer ones. There it can dominate, perhaps by aggressive behavior,
perhaps by better dispersal or mobility, perhaps by some other means.
Because the intolerant species requires the best habitats, it often tends to
have a smaller geographic range, less dense populations, and therefore, a greater risk of extinction. In contrast, species capable of profitably using the poorer
habitats should be the behavioral opportunists, flexible enough to go wherever
they have the chance to go. In one sense, they do not require the poorer
habitats—they do even better as individuals when they get the opportunity
to use the richer habitats. But in another sense, they do require the poorer
habitats. Without them, they could not coexist with the intolerant species.
Consider the Amani sunbird, which is abundant within and restricted to
about 5,000 ha of Brachystegia forest in coastal Kenya. Is its habitat its prison or its refuge? Joseph Oyugi (2005) answered this question with a foraging approach based on patch use, density-dependent habitat selection, and

interspecific interactions.
The collared sunbird—a widespread kulturfolger—shares the forest with
the Amani sunbird. But the collared sunbird uses all surrounding habitats,
too. In his habitat selection studies, Oyugi discovered that these two sunbird
species allocate foraging heights in Brachystegia trees. The Amani sunbird
forages high, the collared sunbird forages low, and both species overlap in the
mid-canopy.
When Oyugi examined foraging at the scale of patch use (individual branches), he found that the mid- and lower canopies offer better foraging opportunities than does the high canopy. Collared sunbirds interfere with the
mild-mannered Amani sunbirds. The interference raises Amani foraging costs
in the richer habitats and prevents them from using those habitats.
Overall, we see a case of shared preference habitat selection, with the less
preferred but critical habitat being the crowns of mature Brachystegia. The
Amani is actually the habitat generalist, and the crowns of Brachystegia its refuge. Lose these trees, and we lose the Amani sunbird to competitive exclusion
by the collared sunbird.
The differences between the sunbirds remind me of the many cases of
shared preference organization that I have seen in the field and the literature—
beginning with the classic case of Chthamalus and Balanus in the intertidal zone
of Scotland (Connell 1961). The story of Bufo bufo and B. calamita fits, too. The


On Foraging Theory, Humans, and the Conservation of Diversity

natterjack toad is the intolerant species, needing the warmer waters where its
larvae can grow rapidly. But, in contrast to the unusual case of the sunbirds, the
intolerant species (the natterjack) has the smaller population and narrower range.
I am speculating, of course, but I believe that studying shared preference
organization may be the easiest way to predict which species can be fitted with
a reconciled habitat. Dominant species in a shared preference system may be
entirely incapable of succeeding in any but the richest, most pristine habitats.
If they require relictual habitats, dominant species may be kulturmeider forever.

Tolerant species, on the other hand, may be among those most likely to take
advantage of new habitats. Tolerant species may provide the best targets for
us to turn into kulturfolger.
But the reverse hypothesis also has merit. Human-dominated habitats often have an unnaturally steady supply of abundant resources. For example,
in Tucson, total bird populations are about thirty times as large as they are in
the surrounding national park (Emlen 1974). Whether accidentally or intentionally, Tucsonans supply water and food to those species that can stand to
live alongside us. Under such circumstances, the intolerant species may be the
most successful kulturfolger.
Regardless of which hypothesis succeeds in a given case, I suggest that
a good way to recognize inveterate kulturmeider will be to examine the tolerance-intolerance organization of natural communities.

14.6 Management of Relictual and Novel Habitats

During the Homogocene, the hand of Man will be everywhere. We might
as well admit that, although it may require getting over an emotional hurdle
to do so. Intentionally or not, we are destined to manage life on this planet.
We might as well try to do a good job, and what we learn about foraging behavior can help us. In fact, we can use behaviors as leading indicators of
environmental quality and population change.
Monitoring Species and their Habitats by Measuring Behavior

Well-adapted behaviors are good indicators of both food quality and habitat
quality. The forager that leaves a lot of food behind (has a high giving-up
density) is telling us that it perceives a relatively rewarding set of habitats.
In contrast, stressed animals faced with a poorer environment will extract
almost all the available food from a patch (have a low giving-up density) in
habitats they always use, may accept lesser habitat types, and may use habitats
with an elevated threat of predation.

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Because a well-adapted species expands its choice of habitats as its population grows, the variety of habitats it uses can help us monitor its population
size (Rosenzweig 1987). Use of low-ranking habitats suggests large populations. The manager armed with a ranked list of habitats can census them in
inverse quality order. When she knows the poorest habitat that the target
species currently uses, she can infer the current population size. For species
whose overabundance could pose a problem, a quick census of only a few
inferior habitat types could reveal the threat quickly and cheaply. For exploited species, whose overabundance would represent an opportunity for a
large yield, a census based on optimal habitat selection would allow an earlier
and more efficient harvest. For species whose recent population sizes create a
concern for their future, managers could start censusing in the poorest habitat in which observers last reported them. Then higher- or lower-ranking
habitats would be censused, depending on whether the first census found
any individuals. The census would proceed up-rank until individuals were
detected or down-rank until they were no longer detected.
Sometimes we can use the foraging behavior of one species to monitor
another. For example, although preservation efforts often target large carnivores, most large carnivores are scarce and difficult to observe. But their prey
are not so scarce. And their prey are experts; they have been in the business
of detecting predators for untold generations. So if we can learn to interpret
their behavior as a reflection of predation threat, we can indirectly census the
predators.
Changes in the foraging behavior of a potential prey individual seem
straightforward (Brown 1999; Brown et al. 1999). With a predator nearby,
the individual should spend more time being vigilant. It should also reject
some riskier habitats entirely and exhibit higher giving-up densities in those
it continues to use. Foraging time proportions should shift asymmetrically:
away from more dangerous habitats and toward safer ones. Abundant evidence
confirms such changes (e.g. Abramsky et al. 1996; Brown 1988; Brown and

Alkon 1990; Dall et al. 2001; Dill and Fraser 1984; Fraser and Cerri 1982;
Kotler, Brown, Slotow et al. 1993; Kotler et al. 1994; Lima 1985a; Milinski
and Heller 1978; Nonacs and Dill 1990; Rosenzweig et al. 1997; Sih 1982;
Werner et al. 1983).
So we know that foraging behavior changes predictably in response to
predation threat. People studying rare and elusive carnivores in the field now
apply this knowledge to their work. For example, mule deer (Odocoileus hemionus) foraging behavior signals the presence and threat of mountain lions
(Puma concolor) nearby (Altendorf et al. 2001) (see chap. 13). The behavior of
Nilgai antelope (Boselaphus tragocamelus) at water holes helps rangers in India
to monitor tigers (Panthera tigris) (Brown, personal communication). And the


On Foraging Theory, Humans, and the Conservation of Diversity

behavior of blue sheep (Pseudois nayaur) in Nepal reveals the proximity of snow
leopards (Panthera uncia) (Gurung 2003). Recently, the vigilance behaviors of
Himalayan tahr helped Som Ale (unpublished data) to find and see two snow
leopards in a span of weeks, providing the first confirmed records in 40 years
of snow leopards in the region of his work.
Managing Reserves for Kulturmeider

Even after we successfully deploy reconciled habitats all over the earth, our
reserves will retain great importance (Rosenzweig 2006). Although big fierce
species sometimes find surprising places among us (Gaby et al. 1985; Dinerstein 2002), I guess that some never will. And our reserves will also provide
the only habitats for inveterate kulturmeider. We shall probably wish to maximize the ability of those reserves to support those species that cannot find
natural homes elsewhere (Rosenzweig 2005).
Suppose, for example, that careful work reveals the population of a kulturmeider (recall the Amani sunbird) to be suffering from competition with
other members of its guild that are kulturfolger (like collared sunbirds). The
manager may want to take steps to restrict the kulturfolger in the reserve. I
doubt that he will find this easy to do. There may never be general rules to

guide us. The job will require perceptive observation of behaviors and considerable inventiveness. And some well-meaning people may not understand.
But the result will make the most of the environmental relicts that we save.
One might readily summarize my attitude toward enlightened management of reserves thus: Behaviors are the shadows of natural selection, of population dynamics, and of community processes (Rosenzweig 2001c). Optimality theories teach us how to ponder these shadows, revealing the state, the
genesis, and the fundamental workings of the natural assemblages that have
cast them. Because they give us some basic understanding of what is going
on, they also provide other valuable services. Optimality theories suggest
what we must do to achieve our conservation goals. They also give us some
confidence that what we do will turn out as we intend. And they constitute
an organizing system that will help us when, inevitably, we struggle to understand our mistakes and to correct them.

14.7 Coevolution in the Homogocene

Conservation ecology—both types, reservation and reconciliation—will supply a new set of ecological theaters for G. E. Hutchinson’s evolutionary plays.
That is, after all, the idea; the old theaters are vanishing so rapidly that if we do

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not supply new theaters, most of the players will vanish. The existing players
may not know exactly how to act in the new theaters. That is to say, most
or all will have to learn a new part. Yet at least the new theaters give them
the chance to rehearse and improve. Natural selection being the consummate
teacher that she is, we can expect them to improve a great deal. Much evidence indicates that evolution can occur quite rapidly in an anthropogenic
environment (Ashley et al. 2003).
How will species change? What will happen to their niches and their behaviors? How will life in the new communities function? Optimal foraging
was set up to answer exactly such questions (MacArthur and Pianka 1966).

So far, progress in answering them has come from a growing body of theory
with exciting potential.
One may tap into the literature of this work in several places (Abrams
2001; Cohen et al. 2001; Holt and Gomulkiewicz 1997b; Rosenzweig and
Ziv 1999). This work asks a basic question: How can we predict the evolution
of fundamental niches? Many subquestions arise, including the following:
How does diversity affect the shape of niches (especially their breadths)?
What prevents niches from evolving in response to environmental change?
Does competition restrict the degree of specialization, and if so, how can we
predict its upper limit? The work has only begun.
Nevertheless, we can depend on one aspect of change during the Homogocene. Not change directed by natural selection, but change elicited by the
environments we provide for ourselves. If we continue down our current
path, nature will wither and diminish. We will scarcely notice. Our baseline
will decline each generation, and our disappointment will occupy a low
priority in our lives. Sad Bayesians though we be, natural selection has made
us Bayesians. We cannot be anything else.
But if we resolve to take advantage of what we already know, to learn more,
to invent new environments and inject life into the sterility with which we
now surround ourselves, then our baseline will shift upward. Reconciliation
ecology will become the great environmental educator. Encompassing us in
beauty, it will teach us what we can have and what to work for. That change
in behavior will be most welcome.

14.8

Summary

Foraging and habitat selection theories provide a sound basis for conservation
of species diversity. Optimality-grounded research can efficiently and rapidly
monitor the population sizes of species. It can reveal underlying habitat

needs and preferences as well as fundamental community organization. Homo


On Foraging Theory, Humans, and the Conservation of Diversity

sapiens is the single indispensable species whose optimal behaviors we must
understand. People set the rules for managing biotic diversity, and those
rules must not oppose the natural, evolved behaviors of our species, particularly those that judge—however subconsciously—the costs and benefits
of what we do and might do. In addition, people will increasingly engage
in reconciliation ecology, redesigning their own habitats to welcome more
and more nonhuman species. Those redesigned habitats must do more than
sustain us in health and comfort. We will deploy them only if they satisfy us
aesthetically. Once we do, they will reverse the intergenerational decline in
human environmental expectations known as the shifting baseline.

14.9 Suggested Readings

Rosenzweig (2005) provides an article that complements this chapter. Heerwagen and Orians (1993) discuss attempts to understand what people like.
Penn (2003) speculates on the evolutionary roots of human-environment interactions. Rosenzweig (2003b) provides a manifesto for reconciliation ecology. Daily and Ellison (2002) explore the problem of bringing profit under
the tent of conservation. McNeely and Scherr (2002) review the crucial task
of combining farming with conservation in the world’s tropics. Dinerstein
(2002) reviews World Wildlife’s massive and inspiring undertaking to integrate some quite dangerous mammals into productive human habitats.

501



Contributors

Melissa M. Adams-Hunt

Psychology Department
University of California at Berkeley
3210 Tolman Hall #1650
Berkeley, CA 94720-1650
USA
m

Thomas W. Castonguay
Nutrition and Food Science
University of Maryland
0112 Skinner Building
College Park, MD 20742-7521
USA


Peter A. Bednekoff
Biology Department
Eastern Michigan University
Ypsilanti, MI 48197
USA


Colin W. Clark
Department of Applied Mathematics
University of British Columbia
Vancouver, British Columbia V6T 1Z2
Canada
colin

Anders Brodin

Department of Theoretical Ecology
Lund University
Ecology Building
S-223 62 Lund,
Sweden


Kristin L. Field
Department of Evolution, Ecology, and
Organismal Biology
Ohio State University
318 W. 12th Avenue
Columbus, OH 43210-1293
USA
fi

Joel S. Brown
Department of Biological Sciences
University of Illinois at Chicago
845 West Taylor St
Chicago, Illinois 60607-7060
USA

503


504

Contributors

Ian M. Hamilton
Department of Evolution, Ecology and
Organismal Biology
Ohio State University
318 W. 12th Avenue
Columbus, OH 43210-1293
USA

Robert D. Holt
Department of Zoology
University of Florida
P.O. Box 118525
Gainesville, FL 32611-8525
USA
fl.edu
Alasdair I. Houston
Department of Biological Sciences
University of Bristol
Bristol, BS8 1UG
UK

Lucia F. Jacobs
Psychology Department
University of California at Berkeley
3210 Tolman Hall #1650
Berkeley, CA 94720-1650
USA

Tristan Kimbrell
Department of Zoology

University of Florida
P.O. Box 118525
Gainesville, FL 32611-8525
USA
kimbrell@ufl.edu
Burt P. Kotler
Mitrani Department of Desert Ecology
Ben-Gurion University of the Negev
Jacob Blaustein Institute for Desert
Research,
Midreshet Ben-Gurion, 84990
Israel



Ake Lindstră m
o
Department of Animal Ecology
Lund University
S-223 62 Lund,
Sweden

Georgia Mason
Department of Animal and Poultry
Science
University of Guelph
Guelph, Ontario N1G 2W1
Canada

John M. McNamara

Department of Mathematics
University of Bristol
University Walk
Bristol, BS8 1TW
UK

John B. Mitchell
Department of Social Science
Brescia University College
University of Western Ontario
London, Ontario N6G 1H2
Canada

Jonathan A. Newman
Department of Environmental Biology
University of Guelph
Guelph, Ontario N1G 2W1
Canada

Vladimir V. Pravosudov
University of Nevada, Reno
Biology Department m/s 314
Reno, NV 89557



Contributors

Frederick D. Provenza
Department of Wildland Resources

Utah State University
Logan, UT 84322-5230
USA

David Raubenheimer
School of Biological Sciences and
Liggins Institute
University of Auckland
Private Bag 92019
Auckland
New Zealand

Michael L. Rosenzweig
Department of Ecology & Evolutionary
Biology
University of Arizona
Tucson, AZ 85721
USA

Kenneth A. Schmidt
Department of Biological Sciences,
Texas Tech University
MS 3131
Lubbock, TX 79409
USA

David F. Sherry
Department of Psychology, University
of Western Ontario
London, Ontario N6A 5C2

Canada

Peter Shizgal
Center for Studies in Behavioral
Neurobiology
Concordia University
7141 Sherbrooke St. W.
Montreal, Quebec H4B 1 R6
Canada


David W Stephens
Ecology, Evolution and Behavior
University of Minnesota
1987 Upper Buford Circle
St. Paul, MN 55108
USA

Thomas A. Waite
Department of Evolution, Ecology, and
Organismal Biology
Ohio State University
318 W. 12th Avenue
Columbus, OH 43210-1293
USA

Christopher J. Whelan
Illinois Natural History Survey
Midewin National Tall Grass Prairie
South State Highway 53

Wilmington, IL 60481
USA

Stephen C. Woods
Obesity Research Center
University of Cincinnati
2170 East Galbraith Road
Cincinnati, OH 45237

Ron Ydenberg
Department of Biological Sciences
Simon Fraser University
8888 University Drive
Burnaby, British Columbia V5A 1S6
Canada


505



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