Primate conservation along the Tana River, Kenya: an examination of the forest habitat


Medley, Kimberly, E.

Conservation Biology 7(1): 109-121

1993


implementing management plans that integrate economic (productivity and growth), social (equity

Primate
Conservation
along
the
Tana
River,
Kenya:
An
Examination
of
the
Forest
Habitat
KIMBERLY
E.
MEDLEY*
Department
of
Botany
and
Plant
Pathology
Michigan
State
University
East
Lansing,
MI
48824,
U.S.A.
Abstract:
The
Tana
River
National
Primate
Reserve,
Kenya,
was
established
in
1976
to
preserve
the
endemic
and
endan-
gered
Tana
River
red
colobus
(Colobus
badius
rufomitratus)
and
crested
mangabey
(Cercocebus
galeritus
galeritus).
Be-
tween
1975
and
1985
their
populations
declined
by
80%
and
45%,
respectively.
A
study
addressing
primate-to-habitat
relationships
was
conducted
in
12
forest
areas
to
determine
what
attributes
appear
most
important
to
the
in
situ
preser-
vation
of
both
endangered
primates.
Correlations
among
the
abundances
of
primate
groups
their
group
sizes,
and
the
structural
resource,
disturbance,
and
spatial
attributes
of
the
forest
were
used
to
distinguish
the
quality
of
forest
patches
Intraforest
habitat
quality
was
examined
using
ca-
nonical
variate
analysis
to
discriminate
primate
ranging
patterns
based
on
canopy
and
subcanopy
tree
composition.
The
colobus
and
mangabey
show
positive
relationships
to
interior-forest
habitat
and
appear
susceptible
to
forest
dis-
turbances
that
reduce
forest
area
or
that
increase
forest
edge
and
intraforest
disturbance.
Forest
loss
fragmentation,
and
consequent
reduction
in
the
area-to-perimeter
ratio
of
the
remaining
forests
measured
from
1960
to
1975
provide
a
partial
explanation
for
the
decline
in
primate
populations.
The
results
suggest
that
a
combination
of
primary
food
items
and
seasonal
food
resources
in
large
high-stature
closed-
canopy
forests
is
the
best
predictor
of
high-quality
habitat
for
these
monkeys.
Stewardship
should
be
directed
at
the
preservation
of
these
areas
or
the
restoration
of
forests
to-
ward
this
habitat
model
Current
address:
Department
of
Geography,
217
Shideler
Hall
Mi-
ami
University,
Oxfor4
OH
45056,
U.S.A
Paper
submitted
March
15,
1991;
revised
manuscript
accepted
May
20,
1992.
Conservacion
de
primates
a
lo
largo
del
rio
Tana,
Kenya:
examen
del
habitat
selvatico
Resumen:
La
Reserva
de
Primates
del
Rid
Tana;
en
Kenya,
fue
establecida
en
1976
para
preservar
el
colobus
rojo
del
rio
Tana
(Colobus
badius
rufomitratus)--endemico
de
esta
re-
gi6n
y
en
peligro
de
extincia—y
el
mangabey
crestado
(Cer-
cocebus
galeritus
galeritus).
Entre
1975
y
1985
sus
pobla-
ciones
declinaron
en
un
80%
y
un
45%,
respectivamente.
Se
condujo
un
estudio
dirigido
a
evaluar
la
relaciOn
primate-
habitat
en
12
areas
selvaticas
para
determinar
que
atributos
serz'an
los
mas
importantes
para
la
preservaci6n,
in
situ,
de
ambas
especies
de
primate
en
peligro
de
extincion
Se
usaron
correlaciones
entre
la
abundancia
de
los
grupos
de
primates
su
tamalio
grupal
y
atributos
estructurales,
de
recursos
de
perturbacion
y
espaciales
de
la
selvg
para
distinguir
la
cal-
idad
de
los
parches
de
selves
Se
examin6
la
calidad
del
hab-
itat
intra-forestal
usando
analisis
can6nico
de
variables
para
discriminar
los
patrones
de
desplazamiento
de
los
pri-
mates
basados
en
la
composicion
arborea
del
canopeo
y
subcanopeo.
El
colobus
y
el
mangabey
muestran
relaciones
positivas
con
respecto
al
habitat
selvatico
interior
y
parecen
susceptibles
a
perturbaciones
de
la
foresta
que
reducer
el
area
foresta4
o
incrementan
el
borde
forestal
y
la
perturba-
cion
infra
forestal
La
perdida
de
selvg
la
fragmentacion
y
la
consecuente
reducci6n
en
la
relaci6n
area-perimetro
de
las
selvas
remanentes
medidas
entre
1960
y
1975
proveen
una
explicaci6n
parcial
para
la
declinacion
de
las
pobla-
ciones
de
primates.
Los
resultados
sugieren
que
una
combi-
nacion
de
items
de
alimentos
primarios
y
recursos
alimen-
ticios
estacionales
en
canopeos
selvaticos
cerraclos
grandes
y
de
gran
porte
son
los
mcjores
predictores
del
habitat
de
alta
calidad
para
estos
monos.
El
mancyo
tendria
que
estar
di-
rigido
a
la
preservaci6n
de
estas
areas
o
a
la
restauracion
de
las
selvas
hacia
este
modelo
de
habitat.
109
Conservation
Biology
Volume
7,
No.
1,
March
1993
110
Tana
River
Primate
Habitat,
Kenya
Medley
Introduction
The
endangered
Tana
River
red
colobus
(Colobus
ba-
dius
rufomitratus)
and
crested
mangabey
(Cercocebus
galeritus
galeritus)
are
endemic
to
an
isolated
mosaic
of
forest
patches
along
the
lower
floodplain
of
the
Tana
River,
Kenya.
In
1976
the
Tana
River
National
Primate
Reserve
(TRNPR)
was
established
to
preserve
the
best
remaining
populations
(the
largest
number
of
groups
within
a
contiguous
area)
of
these
two
primates
and
their
riverine
forest
habitat
(Marsh
1976).
Prior
re-
search
conducted
on
the
red
colobus
(Marsh
1978)
and
the
crested
mangabey
(Homewood
1976)
provided
baseline
information
from
which
to
monitor
population.
changes.
Recent
primate
censuses
have
revealed
a
de-
cline
of
approximately
80%
in
the
red
colobus
popula-
tion
(from
1200-1800
in
1975
to
200-300
individuals
in
1985;
Marsh
1986)
and
a
45%
decline
in
the
crested
mangabey
population
(from
1100-1500
in
1975
to
620-780
individuals
in
1988;
Kirmaird
1990).
Marsh
(1986)
suggested
that
the
significant
decline
in
their
populations
may
be
a
consequence
of
a
corresponding
decline
in
forest
habitat.
Furthermore,
it
was
clear
that
long-term
preservation
of
the
primates
would
depend
on
the
maintenance
of
suitable
forest
habitat.
I,
there-
fore,
conducted
an
ecological
investigation
of
the
for-
ests
as
habitat
for
the
two
endangered
primates
(Medley
1990).
A
primary
objective
was
to
identify
the
habitat
attributes
most
important
to
their
survival
within
the
riverine
forests
and
thereby
to
determine
if
vegetation
changes
explain
their
population
declines.
Studies
of
wildlife-to-vegetation
relationships
gener-
ally
have
focused
on
the
development
of
habitat
models
that
predict
animal
presence,
diversity,
or
abundance
(Verner
et
al.
1986).
These
models
are
based
on
as-
sumed
relationships
between
the
animal
and
its
envi-
ronment
and
usually
are
a
compilation
of
simple
corre-
lations
between
animal
and
habitat
attributes
(Hamel
et
al.
1986;
Schamberger
&
O'Neil
1986).
In
primate
stud-
ies,
abundances
or
behavioral
patterns
have
been
re-
lated
to
habitat
degradation
(Struhsaker
1976;
Altmann
et
al.
1985;
Berenstain
1986),
human
land
use
(Johns
1986;
Skorupa
1986;
Tarara
1986)
food
resources
(Struhsaker
1975;
Wrangham
1977;
Marsh
1981a;
Marsh
1981b;
Homewood
1978;
Terborgh
&
Janson
1986)
or
forest
structure
(Whitten
1982;
Skorupa
1986,
1988).
Habitat
management
recommendations
are
de-
rived
from
the
contrasting
behavioral
or
demographic
responses
observed
in
each
species.
Primate
habitat
is
defined
in
this
study
by
forest
struc-
ture,
food-resource
abundance,
level
of
disturbance,
and
the
shapes
and
sizes
of
riverine
forest
patches
within
the
range
of
the
Tana
River
red
colobus
and
crested
mang-
abey.
Relative
habitat
quality
is
determined
by
the
rela-
tionships
between
these
attributes
and
primate
abun-
dances,
or
their
annual
ranging
patterns
within
a
forest
patch.
Van
Horne
(1983)
suggests
that
density-habitat
correlations
may
be
confounded
in
a
heterogeneous
area
by
seasonal
and
multi-annual
environmental
vari-
ability,
or
by
social
interactions
among
species.
Between
1985
and
1988,
concurrent
with
the
field
research,
there
were
no
significant
changes
in
the
numbers
of
groups
or
group
sizes
of
colobus
and
mangabeys
(Decker
&
Kinnaird
1992)
within
the
TRNPR.
These
findings
suggest
that
the
populations
may
have
stabi-
lized
and
that
their
current
abundances
reflect
the
rel-
ative
carrying
capacities
of
the
existing
forests.
In
view
of
the
absence
of
long-term
demographic
data
for
a
large
number
of
forests,
the
primate
abundance
data
for
the
forest
patches,
coupled
with
their
annual
ranging
pat-
terns
within
occupied
patches,
are
used
to
depict
the
forest
habitat
preferences
of
the
Tana
River
red
colobus
and
crested
mangabey.
The
primate-to-habitat
relation-
ships
determined
from
this
study
are
incorporated
into
a
model
that
establishes
criteria
useful
in
assessing
the
habitat
quality
of
existing
riverine
forests
and
that
pro-
vides
a
basis
for
protection
and
restoration
of
suitable
habitat.
The
conservation
goal
is
the
long-term
preser-
vation
of
both
endangered
primates
within
the
pro-
tected
area.
The
Study
Area
The
TRNPR
is
located
in
Eastern
Kenya
along
the
flood-
plain
section
of
the
Tana
River
(1°
55'
S,
40
°
07'
E).
The
Tana
flows
from
the
humid
highlands
near
Mt.
Kenya
and
the
Aberdare
mountain
range,
through
an
arid
flood-
plain
between
Garissa
and
Garsen,
and
to
the
Indian
Ocean
north
of
Malindi.
Long-term
climatic
records
for
Hola,
approximately
40
km
upstream
from
the
Reserve,
indicate
an
average
annual
precipitation
of
470
mm,
with
no
months
with
>100
mm,
and
a
growing
season
of
40
days
coincident
with
the
rains
between
October
and
December
(FAO
1984).
The
site
is
equatorial,
with
minimum
and
maximum
temperature
averages
equal
to
21.4°
C
and
33
°
C,
respectively
(Muchena
1987).
The
life
zone
is
thorn
woodland
(sensu
Holdridge
1967).
Forest
vegetation
along
the
Tana
is
groundwater-
dependent,
and
its
lateral
extent
is
determined
sharply
by
the
declining
water-table
gradient
from
the
river
(Hughes
1988).
Periodic
disturbances
by
river
mean-
ders,
flooding,
and
human
activity
have
created
a
patchy
distribution
of
forest
vegetation
(Fig.
1).
The
riverine
forest
is
composed
of
isolated
forest
patches,
which
to-
gether
are
an
isolated
island
of
evergreen-
semievergreen
forest
in
a
semiarid
habitat
(Hamilton
1974).
The
Tana
River
red
colobus
and
crested
mang-
abey
are
endemic
to
the
riverine
forests
extending
from
the
delta
at
Garsen
to
the
northern
border
of
the
TRNPR
(Decker
&
Kinnaird
1992).
Conservation
Biology
Volume
7,
No.
1,
March
1993
TRNPR
,
Mnazini
GARISSA
Lair
Totaru
gn
RESEARCH
CAMP
tichelclo
WcAt
mw
EEAOMO
S
nalPItill
Sind
b
sa
bsb
S
1
Sampled
forest
areas
Settlements
S
o
km
Abianns
,%'orth
Lair
.Allah
mn
KETERE
S
m
Kenya
S
Rice
Scheme
MALINDI
kg!,1A.70
,
41
Medley
Tana
River
Primate
Habitat,
Kenya
111
Figure
1.
The
study
area
in
the
south-central
sector,
TRNPR
The
12
forest
areas
sampled
include:
Guru
North
(gn),
Guru
South
(gs),
Mchelelo
West
(mw),
Congolani
Central
(cc),
Congolani
West
(cw),
Sifa
West
(sw),
Baomo
North
(bn),
Baomo
South
a
(bsa),
Baomo
South
b
(bsb),
Kitere
West
(kw),
Mnazini
North
(mn),
and
Mnazini
South
(ms).
The
top
inset
map
shows
the
reserve
boundary
and
riverine
forest
patches (shaded).
The
bottom
left
map
shows
the
po-
sition
of
the
Tana
River
watershed
in
Eastern
Kenya
Figure
is
reprinted
from
Medley
(1992).
Methods
Data
Acquisition
I
selected
12
study
areas
that
were
representative
of
the
variation
in
forest
types
and
for
which
data
were
avail-
able
on
the
endangered
primates
(Table
1
and
Fig.
1).
Data
on
the
primate
populations
have
been
compiled
from
recent
censuses
and
include
the
number
of
colo-
bus
and
mangabey
groups
in
each
forest
area
and
their
group
sizes
(Kinnaird
1990;
Odhiambo
1990;
Kinnaird
&
O'Brien
1991;
Decker
&
Kinnaird
1992).
In
three
forest
patches,
I
was
provided
data
on
primate
ranging
patterns
from
concurrent
studies
on
the
red
colobus
by
B.
S.
Decker
(1989)
and
on
the
crested
mangabey
by
M.
F.
Kinnaird
(1990):
Mchelelo
West
(1
colobus
group;
2
mangabey
groups),
Baomo
South
a
(1
colobus
group),
and
Mnazini
North
(1
mangabey
group).
Ranging
data
were
compiled
as
the
annual
sum
of
all
location
records,
by
0.25-ha
quadrats,
collected
during
the
half-hourly
scans
of
all-day
follows
(see
Decker
1989;
Kinnaird
1990).
Vegetation
data
were
collected
from
two
structural
layers,
using
point-centered
quadrat
sampling
for
can-
opy
trees
(>20
cm
dbh)
and
complete
enumeration
in
112
m
2
plots
for
subcanopy
trees
and
lianes
(10-20
cm
dbh)
and
palms
(>1
m
in
height)
(Grieg-Smith
1983).
Sampling
points
(n
=
363)
were
located
systematically
within
the
12
forest
areas,
and
the
quadrats
or
plots
were
randomly
oriented
from
each
point.
Plant
species'
densities
and
basal
areas
by
structural
layer,
clinometer
measurements
of
canopy
height,
and
mean
distances
among
the
crowns
of
trees
more
than
10
m
in
height
were
averaged
for
the
sampling
points
in
each
study
area.
Forest
disturbance
was
compiled
as
the
mean
basal
area
of
stems
that
were
cut,
dead,
or
damaged
(de-
barked
or
broken)
by
animals.
Correlation
Analyses
Spearman's
rank
correlations
were
computed
between
selected
ecological
attributes
summarized
for
a
forest
area
and
the
respective
primate
abundances
(Conover
1971;
Hinze
1987).
The
forest
characteristics
examined
have
been
categorized
as
structural,
resource,
and
spa-
tial
attributes
and
forest
disturbance
(Table
2).
Impor-
tant
food
resources
are
derived
from
behavioral/
ecological
studies
conducted
on
the
red
colobus
by
Marsh
(1981a)
and
Decker
(1989)
and
on
the
crested
mangabey
by
Homewood
(1978)
and
Kinnaird
(1990).
Based
on
their
studies
in
four
forest
areas
(Mchelelo
West,
Baomo
South
a,
Mnazini
North,
and
Mnazini
South;
see
Fig.
2),
plant
species
were
identified
that
to-
gether
account
for
more
than
50%
and
more
than
30%
of
the
feeding
time
by
the
colobus
and
mangabey,
re-
spectively:
Ficus
spp.
sycomorus
L,
F
natalensis
Hochst,
F.
bussei
Mildbr.
&
Burret,
F.
scasellattii
[Pamp.]
Stapf,
and
F
bubu
Warb),
Sorindeia
madagas-
cariensis
DC.,
Pachystela
msolo
(Engl.)
Engl.,
Diospy-
ros
mespiliformis
A.
DC.,
Acacia
robusta
subsp.
usam-
barensis
(Taub.)
Brenan,
and
Saba
comorensis
(Boj.)
K
Schum.
Food
resource
abundance
was
measured
as
the
summed
basal
areas
of
mature
trees
(>20
cm
dbh)
and
lianes
(Saba
comorensis;
>10
cm
dbh),
thereby
provid-
ing
an
estimate
of
current
availability.
Canopy-tree
di-
versity
was
measured
using
Simpson's
index
(D
s
=
1-(En
1
(n
i
-1)/N(N-1))),
where
n
equals
the
number
of
Conservation
Biology
Volume
7,
No.
1,
March
1993
112
Tana
River
Primate
Habitat,
Kenya
Medley
Table
1.
Forest
study
areas.
Primate
Populations
Forest
Area
(ha)
Colobus
Mangabey
Forest
Area
73-74
1988
73-74
1988
Forest
Characteristics
Mnazini
South
(ms)
50.1
Mnazini
North
(mn)
36.2
Kitere
West
(kw)
18.3
Baomo
South
a
(bsa)
Baomo
South
b
(bsb)
Baomo
North
(bn)
16.4
Sifa
West
(sw)
2.8
Congolani
West
(cw)
37.2
Congolani
Central
(cc)
52.4
Michelelo
West
(mw)
16.8
Guru
South
(gs)
46
Guru
North
(gn)
4.9
3
1(13)
2
1(15)
Mimusops-Garcinia;
Homewood
(1978)
study
area
3
2(25)
2
2(41)
Pachystela-Ficus;
mangabey
study
area
(Kinnaird
1990)
2
1(5)
1
1
Pachystela-mixed,
colobus
absence
1985-1986
1(23)
1(16)
Pachystela-Ficus;
Pachystela
tree
death
(Medley
1990);
colobus
study
area
(Decker
1989)
1(22)
1(13)
Pachystela-Sorindeia
2-3
1(2)
1-2
1(25)
Ficus-Pachystela
1
0
1
0
Sorindeia-Hyphaene
1
0
1
0
Mimusops-Acacia
3-4
2(22)
2
2(48.5)t
Hyphaene-mixed
2
1(12)
2
2(46)
Hyphaene-Sorindeia-Diospyros;
primate
study
area
(Homewood
1976;
Marsh
1978;
Decker
1989;
Kinnaird
1990)
6--8
1(11)
3-4
2(38.5)1-
Hyphaene-mixed
*
1(5)
*
0
Ficus-mixed
1-
Number
of
individuals
for
the
two
groups
equal
the
sum
of
one
known
group
size
and
an
estimate
of
the
mean
group
size
(20.5;
Kinnaird
&
O'Brien
1991)
for
the
second
group.
Patch
areas
(ha)
have
been
measured
from
1975
aerial
photos
and
ground
surveys.
Group
counts
and
the
estimated
number
of
individuals
(in
parentheses)
are
provided
for
the
red
colobus
(Decker
&
Kinnaird
1992;
Odhiambo
1990)
and
crested
mangabey
(Kinnaird
1990).
Baomo
South
a
(Bsa)
and
b
(Bsb)
are
located
in
a
single
forest
patch
(total
area
=
122.8
ha).
Guru
North
(gn)
was
not
included
in
the
1973-1974
primate
survey.
Table
2.
Forest
attributes
examined
in
the
correlation
analyses
and
the
hypothesized
primate-habitat
relationships.
Forest
Attributes
Hypothesized
Relationships
The
colobus
is
arboreal
(restricted
to
above
10
m),
and
the
mangabey
relies
on
the
forest
canopy
for
protection.
A
higher
mean
canopy
height
is
related
to
a
better-developed
arboreal
habitat
(positive).
Movement
through
the
forest
can
be
more
effectively
achieved
in
a
closed
upper
canopy.
A
greater
distance
between
the
crowns
of
trees
would
inhibit
travel
for
both
primates
and
decrease
the
area
of
forest
available
to
the
colobus
(negative).
A
higher
basal
area
of
canopy
trees
(>20
cm
dbh)
is
related
to
a
better-developed
canopy
forest,
providing
a
better
arboreal
habitat
for
both
primates
(positive).
A
greater
coverage
of
high-quality
primate
food
items
would
improve
the
carrying
capacity
of
the
forest
area
(positive).
Overall
food
diversity,
including
infrequently
used
items,
is
directly
related
to
the
diversity
of
the
upper
canopy.
A
greater
variety
of
food
resources
would
enhance
the
food-resource
quality,
hence
the
carrying
capacity
of
the
forest
area
(positive).
Fruit
produced
by
mature
female
individuals
is
a
primary
food
item
for
the
crested
mangabey
(see
Kinnaird
1992),
not
utilized
by
the
colobus,
and
most
frequent
along
disturbed
edges
or
within
forest
gaps
(positive
for
mangabeys,
negative
for
colobus).
The
combined
effects
of
forest
senescence,
human
utilization,
and
damage
by
large
mammals
are
a
negative
impact
on
forest
structure
(negative).
More
abundant
food
resources
and
a
better
arboreal
habitat
would
be
available
in
a
larger
forest
(positive).
The
colobus
and
mangabey
are
forest
primates,
suggesting
that
their
populations
would
be
highest
in
patches
with
little
edge
and
much
interior
forest
(positive).
Intraforest
heterogeneity
would
improve
or
degrade
habitat
quality
by
the
presence
of
clustered
food
resources
in
otherwise
unsuitable
habitat
(positive),
or
large
disturbed
areas
in
a
forest
of
high
quality
(negative),
respectively.
Forest
Structural
Attributes
Mean
canopy
height
Distance
between
tree
crowns
Canopy
tree
basal
area
Forest
Resource
Attributes
Food
Resources
Canopy
tree
diversity
Phoenix
reclinata
density
Forest
Disturbance
Forest
Spatial
Attributes
Forest
Area
Forest
area-to-perimeter
ratio
Intraforest
heterogeneity
Conservation
Biology
Volume
7,
No.
1,
March
1993
1..............
C
=
1
m
=
1
c
=
2
.....
..
m
=
2
11
'
1
'
1
7
i
ic
=
1
1m
=
2
i..
...
c..z....1........
...
.
m
=
2
C
=
2
m
=
2
Z-'`
.
...1".2.
ISM
III
MN
III
..
-
\\.N
Medley
Tana
River
Primate
Habitat,
Kenya
113
50
c
.
=
40
-
cN
E
m
CD
3
0
-
a
L..
CD
>
0
U
0
20
-
a)
iti
15
u)
10
-
c=1
.
c
t
O
0
0
m
=
1
O
MI
T
tigE
,
C
=
1
m
=
1
1=
1
1
cw
sw
gn
bn
ms
bsb
bsa
kw
mw
gs
mn
cc
Forest
Areas
IIIII
Ficus
Pachystela
Acacia
M
Sorindeia
Diospyros
MI
Saba
iiiii
IN
MI II
Figure
2.
Basal
areas
of
important
food
resources
in
the
12
forest
areas:
Ficus
sycomorus,
Acacia
robusta,
Sorin-
deia
madagascariensis,
Pachystela
msolo,
Diospyros
mespiliformis,
and
Saba
comorensis.
The
numbers
of
colobus
(c)
and
mangabey
(m)
groups
occurring
in
each
forest
(Table
1)
are
indicated
above
the
bar&
individuals
for
each
species
and
N
equals
the
total
num-
ber
of
individuals
(Peet
1974).
Forest
disturbance
was
examined
relative
to
current
primate
populations
and
also
relative
to
the
change
in
primate
group
abundance
between
1975
and
1988
(see
Table
1).
Forest
area
(circa
1987)
and
the
area-to-perimeter
ratios
were
com-
puted
from
digitized
maps
based
on
1975
aerial
photo-
graphs
and
ground
survey,
using
a
geographic
informa-
tion
system
(Arc/Info;
ESRI
1987)
available
on
a
VAX
8650.
Intraforest
heterogeneity
was
computed
as
the
mean
euclidean
distance,
or
dissimilarity,
among
points
within
a
forest
area
based
on
mean
canopy
height,
dis-
tance
between
tree
crowns,
food
resources,
and
distur-
bance.
The
measure
was
adapted
from
Belsky
(1988)
and
computed
using
SYSTAT
(Wilkinson
1987).
Discrimination
of
Intraforest
Primate
Ranging
Patterns
Canonical
variate
analysis
was
used
to
reduce
the
di-
mensionality
of
plant
species
abundance
data
as
applied
to
the
discrimination
of
intraforest
primate
ranging
pat-
terns
(Williams
1981;
Gittens
1985;
James
1985).
The
number
of
site
records
given
for
the
primates
was
the
criterion
variable
used
to
categorize
vegetation
sam-
pling
points
into
three
ranks
of
relative
habitat
use
for
the
three
forest
areas
in
which
the
primates
were
fol-
lowed
(a
total
of
109
points):
high
=
>3%
of
total
records
within
a
forest
(40
points),
medium
=
>1%
and
<3%
of
total
records
(38
points),
and
low
=
<1%
of
total
records
(31
points).
A
line,
or
canonical
variate,
was
located
in
the
space
of
p
attributes
(species
abun-
dances),
for
which
group
separation,
defined
by
the
cri-
terion
variable,
was
optimized
(Cooley
&
Lohnes
1971;
James
1985).
Standardized
species
abundance
data
were
log-transformed
(log(xt
+
1))
(Gauch
1982;
Jongman
et
al.
1987).
The
total
number
of
tree
species
present
at
the
canopy
and
subcanopy
layers
was
60.
An
analysis
of
relative
species
abundances
among
the
three
habitat
ranks,
stepwise
discriminant
procedures,
and
an
assess-
ment
of
the
variance
explained
by
each
species
used
in
preliminary
models
(measures
of
communality)
were
three
techniques
used
to
reduce
the
original
number
of
plant
species
to
a
total
of
24
(Gittens
1985;
James
1985).
The
results
were
used
to
determine
the
degree
to
which
plant
species
can
be
discriminated
among
three
ranks
of
habitat
use,
as
shown
by
a
graph
of
the
first
two
canonical
variates,
and
to
characterize
the
dis-
crimination
through
interpretation
of
the
correlations
between
the
species
and
the
variates.
Multivariate
anal-
yses
were
completed
using
the
SAS
statistical
package
available
on
an
IBM
3090
(SAS
1985).
Results
and
Discussion
Correlation
Analyses
Positive
correlations
exist
between
primate
abundances
and
mean
canopy
height
and
total
tree
coverage,
and
Conservation
Biology
Volume
7,
No.
1,
March
1993
Colobus
and
Mangabey
Groups
(n
=
12)
Colobus
Individuals
Mangabey
Individuals
(n
=
12)
Total
Colobus
Mangabey
(n
=
12)
114
Tana
River
Primate
Habitat,
Kenya
Medley
negative
correlations
exist
between
primate
abun-
dances
and
the
distance
between
tree
crowns
(Table
3).
These
results
suggest
the
importance
of
forest
structure
to
the
endangered
primates.
Calculated
correlations
were
significant
between
the
number
of
endangered
pri-
mate
groups,
or
the
number
of
colobus
individuals,
and
the
mean
height
of
the
canopy.
It
is
understandable
that
group
sizes
of
colobus,
an
arboreal
primate
that
rarely
descends
below
10
meters
in
the
canopy
(Marsh
1978),
would
have
higher
correlations
to
canopy
height.
In
contrast,
the
mangabeys
spend
much
time
foraging
along
the
ground
(Homewood
1976;
Kinnaird
1990).
The
mangabeys
may
prefer
a
forest
of
high
stature,
but
their
range
of
available
resources
is
not
necessarily
re-
lated
to
a
closed
canopy.
The
relationships
between
pri-
mate
abundances
and
basal-area
coverage
of
canopy
trees
are
positive
but
nonsignificant.
The
colobus
pop-
ulations
show
highest
correlations
with
forest
structural
parameters,
and
their
preference
is
a
high,
closed-forest
canopy
(Table
3).
Originally
I
hypothesized
that
if
highly-utilized
food
resources
are
abundant,
then
a
higher
number
of
pri-
mates
would
be
present.
The
correlations
are
positive
but
nonsignificant
(Table
3).
A
graph
depicting
the
basal-area
coverages
of
important
food
resources
in
the
12
forest
areas
suggests
that
adequate
food
resources
are
available
at
low
coverages
(Fig.
2).
Sifa
West
and
Congolani
West
have
no
colobus
or
mangabeys,
indicat-
ing
that
a
threshold
level
in
food
resources
may
exist,
below
which
a
forest
becomes
unsuitable.
Although
food-resource
abundances
vary
in
the
different
forests,
a
Ficus
species
is
present
in
all
forests,
was
highly
utilized
in
the
studied
forests
(Homewood
1978;
Marsh
1981a;
Decker
1989;
Kinnaird
1990),
and
may
indeed
be
a
"keystone"
plant
resource
(see
Terborgh
1986;
Skorupa
1988
for
Kibale
Forest,
Uganda).
A
descriptive
summary
of
seven
0.25
ha
quadrats
in
three
forests
that
have
the
highest
number
of
within-forest
site
records
for
the
pri-
mates
supports
this
conclusion
(Medley
1990).
Ficus
sycomorus
occurred
in
four
of
the
seven
plots,
and
other
figs
(F.
bussei,
F.
natalensis,
and
F.
bubu),
despite
their
low
overall
occurrence
in
the
TRNPR
(4
out
of
363
points),
are
present
in
six
of
the
seven
quadrats.
The
relationship
to
canopy-tree
species
diversity
is
opposite
to
that
predicted.
Low
diversity
forests
occur
within
the
reserve,
primarily
due
to
the
monodomi-
nance
of
Pachystela
msolo,
that
have
high
primate
num-
bers.
This
is
particularly
demonstrated
by
the
number
of
colobus
individuals.
Decker
(1989)
found
that
in.
Baomo
South
(Bsa)
27.2%
of
the
colobus
diet
was
con-
tributed
by
P.
msolo,
the
forest
dominant,
and
80%
of
the
colobus
diet
was
contributed
by
only
five
plant
spe-
cies.
In
contrast
to
studies
of
Colobus
badius
in
tropical
moist
forests,
the
Tana
River
red
colobus
appear
adapted
to
a
lower
diversity
of
food
resources
(March
1981a).
As
in
Skorupa's
(1986)
study
of
C
badius
in
the
Kibale
Forest,
they
may
become
"linked"
to
the
occur-
rence
of
particular
food
items,
such
as
the
fairly
contin-
uous
production
of
flowers
in
Pachystela
msolo
or
of
fruit
among
individuals
of
Ficus
sycomorus
(Decker
1989).
In
contrast,
the
frugivorous
(and
insectivorous)
mangabeys
often
maintain
a
more
varied
diet,
not
re-
stricted
to
flowering
plants,
even
in
low-diversity
forests
(Homewood
1978;
Kinnaird
1990;
see
Struhsaker
1969).
Finally,
a
significant
positive
relationship
was
cal-
culated
between
the
mangabey
group
sizes
and
Phoenix
reclinata
Jacq.,
a
documented
primary
food
resource
for
that
primate
(see
Kinnaird
1992).
Its
positive
rela-
tionship
to
colobus,
opposite
to
that
predicted,
is
prob-
ably
spurious;
the
palm
species
occurs
in
forests
that
possess
other
adequate
food
resources
and
a
suitable
forest
structure.
When
the
varied
composition
of
the
12
Table
3.
Spearman
correlations
between
primate
population
characteristics
and
selected
forest
attributes.
Primate
Population
Characteristics
Forest
Structural
Characteristics
Mean
canopy
height
0.616* 0.669*
0.551*
0.657*
0.505
Distance
between
tree
crowns
Canopy
tree
coverage
Forest
Resource
Attributes
Primary
food
resources
Canopy
tree
diversity
Phoenix
reclinata
density
Forest
Disturbance
Forest
Spatial
Attributes
Forest
area
(n
=
10)
Forest
area-to-perimeter
ratio
(n
=
10)
Intraforest
heterogeneity
-
0.347
0.126
0.325
0.293
0.361
0.418
-
0.455
-0.481
0.335
0.376
-
0.492
-0.334
0.632*
0.440
0.768*
0.606*
-
0.689*
-0.669*
-
0.218
0.305
0.280
-0.313
0.446
-
0.569*
0.520
0.693*
-
0.715*
-
0.454
0.432
0.425
-
0.684*
0.179
-
0.130
0.585*
0.756*
-
0.429
-
0.097
0.284
0.239
-
0.317
0.523*
-
0.596*
0.509
0.661*
-
0.789*
Significant
correlations
(p
<
0.05)
are
indicated
with
an
asterisk
Conservation
Biology
Volume
7,
No.
1,
March
1993
Medley
Tana
River
Primate
Habitat,
Kenya
115
forests
is
considered,
the
relationships
to
food
resources
are
positive
but
are
relatively
low
and
nonsignificant.
These
results
may
be
partially
explained
by
an
absence
of
specificity
in
the
primates'
food
requirements
and/or
by
their
adaptability
in
some
forests
to
low
resource,
diversity.
Negative
correlations,
significant
for
the
mangabeys,
are
found
between
the
primate
abundances
and
forest
disturbance
(Table
3).
A
graphic
representation
of
each
measure
(forest
senescence,
human
forest
utilization,
and
animal
damage)
shows
their
relative
contribution
to
the
total
disturbance
value
and
the
importance
of
their
impact
on
the
studied
forests
(Fig.
3).
The
highest
mea-
sures
of
disturbance
are
related
to
forest
senescence,
and
the
highest
levels
of
forest
senescence
are
the
result
of
natural
floodplain
dynamics.
A
major
flood
event
in
1961
resulted
in
a
meander
cut-off
and
the
positioning
of
the
Congolani
West
forest
at
a
distance
greater
than
1
km
from
the
river.
Consequently,
the
groundwater
level
is
lower
and
the
forest
is
changing
toward
bush
vegeta-
tion.
Another
major
flood
occurred
in
1969
that
brought
high
water
into
a
large
monodominant
stand
of
P.
msolo
in
Baomo
South,
resulting
in
immediate
tree-
falls
or
the
decline
and
death
of
many
trees.
The
graph
also
indicates
that
high
levels
of
pole
cutting,
such
as
those
measured
in
Baomo
North
and
Sifa
West,
may
have
a
negative
impact
on
the
suitability
of
an
area
as
primate
habitat.
Large
animal
disturbance
shows
little
relationship
to
primate
abundances
in
the
studied
for-
ests.
A
negative
correlation
is
also
found
between
the
change
in
primate
group
abundance
between
1975
and
1985
and
forest
disturbance
(R,
=
—0.445,n
=
9;p
>
0.05).
Forest
disturbance
appears
to
be
related
to
the
primate
decline,
but
the
nonsignificant
correlation
sug-
gests
that
it
is
coupled
with
other
negative
impacts
(such
as
disease
or
drought;
see
Marsh
1986).
The
cor-
relations
between
primate
abundances
and
current
lev-
els
of
forest
disturbance
do
not
account
for
temporal
responses
that
may
be
revealed
in
long-term
demo-
graphic
data
on
births
and
survivorship
(see
Van
Home
1983;
Pulliam
1988).
They
do
demonstrate,
however,
the
relative
importance
of
natural
and
human-induced
disturbances
within
this
ecosystem
that
must
be
consid-
ered
when
management
is
restricted
to
a
small
pro-
tected
area.
Primate
abundances
are
highly
correlated
with
the
spatial
characteristics
of
the
forest
(Table
3).
The
neg-
ative
correlations
with
intraforest
heterogeneity docu-
ment
the
negative
relationship
between
intraforest
dis-
turbance
(such
as
large
gaps
or
forest
edge)
and
primate
abundance.
The
high
positive
correlations
between
for-
est
area
and
the
area-to-perimeter
ratio
suggest
that
changes
in
these
attributes
may
have
a
significant
impact
on
primate
populations.
Both
primates
appear
to
prefer
interior-forest
patches,
so
their
habitat
is
not
enhanced
by
forest
fragmentation.
20
13
_c
cNI
1
5
E
w
cr)
0
L
a)
>
1
0
0
0
0
U)
L.
1
TI
0
v)
co
3
cw
sw
gn
bn
ms
bsb
bsa
kw
mw
gs
mn
cc
Forest
Areas
III
Dead
Cut
Mi
Animal
Damaged
Figure
3.
Forest
disturbance
in
the
12
forest
areas.
Disturbance
is
shown
as
a
summed
measure
of
the
basal
area
of
wood
that
is
dead
(forest
senescence),
cut
(human
forest
use),
and
damaged
by
large
mammals
(ani-
mal
impact).
The
number
of
primate
groups
occurring
in
each
forest
(Table
1)
is
indicated
above
the
bars.
Conservation
Biology
Volume
7,
No.
1,
March
1993
116
Tana
River
Primate
Habitat,
Kenya
Medley
Since
the
establishment
of
the
TRNPR,
forest
loss
has
been
less
than
5%
within
the
study
area
(south-central
TRNPR).
From
an
analysis
of
aerial
photographs,
how-
ever,
I
was
able
to
compare
the
area
of
forest
(
>10
m
ht)
in
1960
to
that
present
in
1975
(Fig.
4).
During
that
15-year
period,
forest
area
decreased
by
56%
within
the
study
area.
Perhaps
more
significant,
five
forest
areas
were
fragmented
into
15
forest
patches,
with
a
decline
in
the
overall
area-to-perimeter
ratio
from
0.292
to
gn
bn
III
Old
River
Course
and
Oxbows
1960
Forest
Area
III
1975
Forest
Area
and
River
Course
rN
I
Figure
4
Map
overlay
depicting
the
forest
and
river
position
changes
between
1960
and
1975
in
the
south-central
sector
of
the
TRNPR
Forest
study
areas
include:
Guru
North
(gn),
Guru
South
(gs),
Mchelelo
West
(mw),
Congolani
Central
(cc),
Congolani
West
(cw),
Sifa
West
(sw),
Baomo
North
(bn),
Baomo
South
a
(bsa),
Baomo
South
b
(bsb),
Kitere
West
(kw),
Mnazini
North
(mn),
and
Mnazini
South
(ms).
0.163.
It
is
very
likely
that
the
primates
surveyed
in
1975
were
compressed
into
small
forest
patches
at
a
density
much
higher
than
their
respective
carrying
ca-
pacities.
Recent
behavioral
and
demographic
studies
on
the
primates
suggest
that
the
sharp
population
reduc-
tions
may
have
been
a
decline
toward
more
stable
car-
rying
capacities
(Decker
&
Kinnaird
1992).
Discrimination
of
Intraforest
Primate
Ranging
Patterns
The
mean
abundance
values
for
the
24
canopy
and
sub-
canopy
trees
within
the
low-,
medium-,
and
high-use
classes
document
differences
among
the
habitat
rank-
ings
(Table
4).
Two
canonical
variates
were
extracted.
The
first
canonical
variate
accounts
for
45%
of
the
vari-
ance
(correlation
=
0.67)
in
the
habitat
discrimination,
and
the
second
canonical
variate
accounts
for
37%
of
the
variance
(correlation
=
0.57).
A
two-dimensional
graph
of
50
points,
selected
randomly,
shows
the
point
distribution
as
determined
by
the
canonical
variates
(Fig.
5).
The
first
canonical
variate
discriminates
the
low-use
areas,
or
poorer
habitat,
from
the
more
suitable
habitat,
while
the
second
canonical
variate
discrimi-
nates
the
medium-use
plots
from
the
low-
and
high-use
plots.
The
interpretation
of
the
discrimination
is
based
on
the
correlations
between
the
variables
(the
plant
spe-
cies)
and
each
canonical
variate.
The
first
canonical
vari-
ate
distinguishes
the
interior
forest
from
the
forest
along
an
edge
or
area
of
disturbance
(Fig.
6).
Antidesma
veno-
sum
Tul.
as
a
canopy
and
subcanopy
tree
and
Ficus
sycomorus
as
a
nonreproductive
subcanopy
tree
oc-
cupy
areas
along
depositional
river
banks
and
old
ox-
bows.
Terminalia
brevipes
Pampan.
and
Spirostachys
venenifera
(Pax)
Pax
occur
on
the
levee
along
an
ero-
sional
bank,
along
the
savanna
in
association
with
the
palm
Hyphaene
compressa
H.
Wendl,
or
in
areas
of
dis-
turbance.
Ficus
sycomorus
and
Diospyros
mespili-
formis,
as
subcanopy
trees,
are
indicative
of
poorer
hab-
itat.
When
these
two
tree
species
are
reproductively
mature,
they
are
used
as
food
resources
by
both
pri-
mates
(Decker
1989;
Kinnaird
1990).
Only
four
cur-
rently
available
food
resources
proved
useful
in
the
hab-
itat
discrimination,
and
one,
Phoenix
reclinata,
is
a
resource
only
for
the
crested
mangabey.
The
areas
of
medium
use
are
discriminated
along
the
second
canonical
variate
from
the
high-
and
low-use
areas
on
the
basis
of
seasonal
food
resources
or
species
associated
with
those
resources
(Fig.
6).
Fruit
or
leaf
production
by
individuals
of
Ficus
natalensis,
Sterculia
appendiculata
K.
Schum.,
Apporhiza
paniculata
Ra-
dlk.,
Cordia
goetzii
Guerke,
and
Diospyros
mespili-
formis
are
important
seasonal
food
resources
for
the
primates
(see
Decker
1989;
Kinnaird
1990)
in
areas
possessing
characteristics
that
may
limit
continual
use.
Ficus
bussei
is
also
an
important
seasonal
resource
for
b
bsb
Conservation
Biology
Volume
7,
No.
1,
March
1993
2
/-
2
5
4
-
2
3
-
2
2
2
inedium
2
2
,
1
3
22
h
igh
3
low
i
2
33
3
,
1
3
3
3
3
3
3
2
2
1
1
.
-2
3
Medley
Tana
River
Primate
Habitat,
Kenya
117
Table
4.
Mean
species
abundances,
by
habitat
rank,
for
the
24
tree
species
used
in
the
canonical
variate
analysis.
Habitat
Ranks
Medium
(n
=
30)
Low
(n
=
31)
Tree
Species
Canopy
Trees
Alangium
salvitfolium
Antidesma
venosum
Pachystela
msolo
Albizia
gummifera
Pavetta
sphaerobotrys
Ficus
natalensis
Sterculia
appendiculata
Ficus
bussei
Bridelia
micrantha
Borassus
aethiopum
Cordia
goetzii
Polysphaeria
multiflora
Diospyros
mespiliformis
Cola
clavata
Standing
Snag
Subcanopy
Trees
Phoenix
reclinata**
Hyphaene
compressa*
Terminalia
brevipes
Diospyros
mespiliformis*
Apporhiza
paniculata**
Ficus
sycomorus*
Antidesma
venosum**
Spirostachys
venenifera
Rauvolfia
mombasiana
High
(n
=
40)
0.86
0.24
25.62
0.40
0.01
0
0
0
0
0
0
0
1.41
0.03
0
316.97
2.23
0
2.23
0
0
0
2.23
6.70
Code
As
Av
Pm
Ag
Ps
Fn
Sa
Fb
Bm
Ba
Cg
Pm
Dm
Cc
S
Pr
He
Tb
Dm
Ap
Fs
Av
Sy
Rm
0.34
0.28
0.14
1.51
9.51
9.60
0
0.15
0
0
0.13
0
2.30
0.01
0
0.05
0
0.10
0
1.30
0.20
0.14
0.03
0
2.07
0.76
0
0.02
0.67
0.02
253.76
106.57
0
34.56
0
11.52
0
2.88
9.40
0
0
34.56
7.05
23.04
18.79
28.80
0
0
Abundances
for
the
canopy
trees
(>20
cm
dbh)
are
recorded
as
basal
area
coverages
(m
2
/ha),
and
abundances
for
the
subcanopy
trees
(10-20
cm
dbh,
and
palms
>1
m
in
height)
are
recorded
as
densities
(#
individuals/ha).
Species
identified
with
an
asterisk
(*)
are
mostly
nonre-
productive
or
include
both
reproductive
and
nonreproductive
individuals
(**).
-4
-3
-2
-1
0
2
3
Canonical
Vatiate
1
Figure
5.
Canonical
variate
analysis
using
24
can-
opy
and
subcanopy
trees
(see
Table
4).
The
graph
shows
the
distribution
(or
discrimination)
of
a
ran-
dom
selection
of
points
based
on
the
extraction
of
two
canonical
variates
Group
centroids
determined
from
all
points
are
identified
for
the
low
(1),
me-
dium
(2),
and
high
(3)
ranks
of
relative
use
based
on
ranging
patterns
the
primates,
but
its
very
infrequent
occurrence
ob-
scures
its
relationship
to
the
primate
ranging
patterns.
The
canonical
variate
analysis
further
emphasizes
the
importance
of
forest
edge
and
intraforest
disturbance
to
the
overall
quality
of
the
forest
patch.
Although
these
areas
are
at
present
unsuitable
for
the
primates,
they
demonstrate
some
potential
for
the
provision
of
future
resources.
In
contrast,
the
composition
of
high-quality
habitat
is
not
easily
defined.
This
may
be
due
to
certain
behavioral
characteristics
of
the
primates
or
to
their
adaptation
to
a
wide
variety
of
food
resources
and
var-
ied
forest
composition.
Conclusions
A
primary
objective
of
these
statistical
and
descriptive
analyses
was
to
develop
a
habitat
model
that
reflects
the
preferences
of
the
two
endangered
primates.
The
results
identify
some
differences
between
the
Tana
River
red
colobus
and
the
crested
mangabey,
but
their
similar
trends
in
most
correlations
and
the
discrimination
of
their
ranging
patterns
suggest
that
a
single
model
will
complement
both
species.
The
arboreal
colobus
show
greater
relationships
to
the
structural
characteristics
of
Conservation
Biology
Volume
7,
No.
1,
March
1993
1
food
/
1
.C.
0.51
a
a
1;
0
a
c
0
ra
a
8
(.)
-0.5'
food
/
food
/
food
/
i
118
Tana
River
Primate
Habitat,
Kenya
Medley
Canonical
Variate
One
_
.,
I 1 T
I
,
i
1
I
f
1
T
I
I
I
1
As
Av
Pm
Ag
Ps
Fn
Sa
Fb
Bm
Cg
Pm
Dm
Cc
S
Ba
Pr
Hc
Tb
Dm
Ap
Fs
Av
Sv
Rm
Plant
Species
Ell
Canopy
Trees
I
Subcanopy
Trees
Canonical
Variate
Two
.,.i
i
I
I
..........,
T
I
T
i I
As
Av
Pm
Ag
Ps
Fn
Sa
Fb
Bm
Cg
Pm
Dm
Cc
S
Ba
Pr
Hc
Tb
Dm
Ap
Fs
Av
Sv
Rm
Plant
species
MI
Canopy
Trees
7
-
1
Subcanopy
Trees
Figure
6
Correlations
between
the
variables
(tree
species)
and
the
two
canonical
variates.
Abundances
of
can-
opy
and
subcanopy
trees
are
listed
in
Table
4
and
include,
from
left
to
right:
canopy
trees
As
=
Alangium
salvii-
folium,
Av
=
Antidesma
venosum,
Pm
=
Pachystela
msolo,
Ag
=
Albizia
gummifera,
Ps
=
Pavetta
sphaerobotrys,
Fs
=
Ficus
natalensis,
Sa
=
Sterculia
appendiculata,
Fb
=
Ficus
bussei,
Bm
=
Bridelia
micrantha,
Ba
=
Borassus
aethiopicum,
Cg
=
Cordia
goetzii,
Pm
=
Polysphaeria
multiflora,
Dm
=
Diospyros
mespiliformis,
Cc
=
Cola
clay-
ata,
and
S
=
standing
snags;
subcanopy
trees
Pr
=
Phoenix
reclinata,
Hc
=
Hyphaene
compressa,
Tb
=
Termi-
nalia
brevipes,
Dm
=
Diospyros
mespiliformis,
Ap
=
Apporhiza
paniculata,
Fs
=
Ficus
sycomorus,
Av
=
An-
tidesma
venosum, Sv
=
Spirostachys
venenifera,
and
Rm
=
Rauvolfia
mombasiana.
Important
primate
food
resources
are
identified
on
the
graph
for
the
first
canonical
variate.
coe
f
f
ic
ien
t
1
0.5
Conservation
Biology
Volume
7,
No.
1,
March
1993
Medley
Tana
River
Primate
Habitat,
Kenya
119
the
forest,
with
preferences
for
a
high-stature
forest
with
a
closed
canopy. Highest
mangabey
densities
are
also
associated
with
a
similar
forest
structure,
suggesting
that
protection or
restoration
of
forests
satisfactory
to
the
colobus
will
also
promote
conservation
of
the
mang-
abey
populations.
Although
the
Tana
River
red
colobus
and
crested
mangabey
are
apparently
adapted
to
a
dynamic
riverine
environment,
within
this
fragmented
landscape
they
prefer
interior-forest
patches
and
are
susceptible
to
dis-
turbances
that
reduce
forest
area
or
that
increase
forest
edge
and
intraforest
disturbance.
Indeed,
forest
frag-
mentation
and
the
decline
in
forest
area
that
occurred
prior
to
the
establishment
of
the
TRNPR
may
partially
explain
the
population
declines
between
1975
and
1985.
In
contrast
to
other
primates,
such
as
the
black-
and-white
colobus,
these
populations
are
not
enhanced
by
natural
or
human-induced
gap-forming
disturbances
(see
Tarara
1986).
The
better
quality
habitat
is
primarily
restricted
to
the
forest
core.
The
riverine
forests
provide
a
variety
of
food
re-
sources
for
the
primates,
and
their
adaptation
to
low-
diversity
forests
suggests
that
food
requirements
may
be
easily
satisfied
within
a
forest
of
suitable
structure.
Crit-
ical
food
items,
or
certainly
superior
food
items,
would
include
all
species
of
Ficus
and,
for
the
crested
mang-
abey,
Phoenix
reclinata
The
ranging
patterns
of
the
primates
are
related
to
the
distribution
of
seasonal
food
resources,
indicating
the
importance
these
food
items
may
have
for
their
long-term
survival.
Overall,
the
results
suggest
that
a
combination
of
pri-
mary
food
items
and
seasonal
food
resources
in
a
high-
stature,
closed-canopy
forest
with
a
high
area-to-
perimeter
ratio
and
low
intraforest
disturbance
is
the
preferred
habitat
for
the
colobus
and
mangabey.
Stew-
ardship
should
be
directed
at
the
preservation
of
these
areas
or
the
restoration
of
forests
toward
this
habitat
model.
Effective
resource
conservation,
however,
de-
pends
on
how
closely
forest
management
complements
or
coincides
with
the
natural
patterns
of
vegetation
change
characterizing
this
dynamic
riverine
landscape.
Acknowledgments
Wildlife
Conservation
International
of
The
New
York
Zoological
Society
sponsored
the
field
research,
with
assistance
and
language
training
provided
by
the
Mich-
igan
State
University
African
Studies
Center
through
a
Department
of
Education
National
Resource
Fellowship.
The
study
was
affiliated
with
the
National
Museums
of
Kenya,
Institute
of
Primate
Research,
under
permission
granted
by
the
Office
of
the
President
(permit
#0P.
13/001/17
C
2
4
/
9
).
I
thank
Barbara
Decker
and
Margaret
Kinnaird
for
the
data
and
insight
provided
by
their
con-
current
studies
on
the
colobus
and
mangabey,
respec-
tively.
Richard
Ostfeld,
Joseph
Skorupa,
Thomas
Struh-
saker,
Margaret
Kinnaird,
and
Peter
Waser
kindly
provided
constructive
comments
on
the
manuscript.
I
prepared
the
manuscript
while
working
as
a
postdoc-
toral
associated
at
the
Institute
of
Ecosystem
Studies
of
The
New
York
Botanical
Garden,
and
at
Miami
Univer-
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