Journal of
Applied Ecology
1999, 36,
564±572
Butter¯y spatial distribution and habitat requirements in
a tropical forest: impacts of selective logging
JANE K. HILL
Centre for Tropical Ecology, Department of Biological Sciences, University of Durham, Durham DH1 3LE, UK
Summary
1. Spatial distribution, abundance and habitat requirements of Ragadia makuta
(Satyrinae) were studied in Sabah (Borneo) in 1997, in unlogged forest and forest
that had been selectively logged 8±9 years ago.
2. Measurement of vegetation structure showed that unlogged forest had signi®cantly larger trees and greater canopy cover than logged forest. A principal components analysis extracted two factors related to forest density and tree size that were
also signi®cantly higher in unlogged forest. However, there was signi®cant spatial
heterogeneity in vegetation structure within logged forest.
3. In undisturbed forest, a logistic regression model identi®ed suitable habitat for
R. makuta as areas of less dense forest close to streams. There were no di€erences
between logged and unlogged habitats in spatial distribution and abundance of R.
makuta. Availability of suitable habitat and habitat requirements of butter¯ies also
did not di€er between habitats. There was, however, signi®cant heterogeneity in
butter¯y abundance within logged forest, corresponding with availability of suitable habitat.
4. Fieldwork in 1997 coincided with a severe drought on Borneo, and butter¯y
spatial distribution and abundance were signi®cantly reduced compared with a
year of more normal rainfall (1996); populations in 1997 contracted to areas
around streams and to areas with high cover of host-plant.
5. Selectively logged areas can be highly heterogeneous in relation to levels of disturbance. Quantifying the e€ects of selective logging on forest structure and the
availability of suitable habitat was crucial to understanding the responses of
R. makuta to habitat disturbance.
Key-words: Borneo, drought, Lepidoptera, Sabah, transect.
Journal of Applied Ecology (1999) 36, 564±572
Introduction
Throughout South East Asia, forests are rapidly
being logged, and in Malaysia most remaining rain
forest is reserved for production and subjected to
selective logging on a 35-year cycle (Whitmore 1984,
1991). The Malaysian State of Sabah (Borneo) was
originally entirely covered by rain forest, of which
36 000 km2 (50%) was estimated to be remaining in
1985 (Collins, Sayer & Whitmore 1991).
Approximately 15% of this forest is under some
form of protection, but many protected areas have
already been selectively logged, and there will be
increasing pressure on remaining areas of forest as
timber resources run out (Collins, Sayer &
# 1999 British
Ecological Society
Correspondence: fax 0191 3742417; e-mail J.K.Hill@
Durham.ac.uk.
Whitmore 1991). The consequences of selective logging for species and ecosystems are therefore of
great current concern. Clear felling and conversion
of forest to plantations and agriculture generally
results in decreased insect diversity (Holloway,
Kirk-Spriggs & Chey 1992), but e€ects of less severe
disturbance are less clear (Wolda 1983; Morse,
Stork & Lawton 1988; Barlow & Woiwod 1989;
Eggleton et al. 1995, 1996).
Tropical butter¯y assemblages are particularly
diverse, with many endemic species, most of which
are dependent to some extent on forest (Collins &
Morris 1985; Sutton & Collins 1991). Data on the
e€ects of selective logging and other forms of forest
disturbance on butter¯y assemblages (species richness and relative abundance) are accumulating
(Bowman et al. 1990; Raguso & Llorente-Bousquets
1990; Kremen 1992; Spitzer et al. 1993, 1997; Hill
565
J.K. Hill
# 1999 British
Ecological Society
Journal of Applied
Ecology, 36,
564±572
et al. 1995; Hamer et al. 1997; Lawton et al. 1998),
and both increased and decreased butter¯y diversity
have been reported in response to disturbance. A
more consistent response to disturbance, however, is
the loss of species with more restricted distributions,
and therefore high conservation value, from disturbed areas (Hill et al. 1995; Hamer et al. 1997),
probably because these species have more restricted
habitat requirements (Thomas 1992). However,
these studies have assumed that the presence of
adult butter¯ies in an area re¯ects local availability
of butter¯y resources, although availability of these
resources was not quanti®ed, and the relationship
between the presence of butter¯ies and their
resources, in particular their larval host-plants, has
not been tested. Moreover, it has been assumed that
butter¯y habitat requirements do not vary in relation to disturbance, and the e€ects of disturbance on
resources and habitat requirements have not been
considered, making it dicult to interpret changes in
species' distributions following forest disturbance.
Despite being highly diverse, tropical butter¯y
communities typically contain few species present in
large enough numbers for the autecological studies
necessary for investigating resource requirements;
most common species are usually either widespread
generalist species of low conservation value, or
migrants (Hill et al. 1995). An exception comprises
species of the satyrid genus Ragadia, which are
often relatively common and are dependent on
closed-canopy forest (Corbet & Pendlebury 1992;
Spitzer et al. 1993). This study investigated the habitat requirements of Ragadia makuta Fruh. Its distribution is con®ned to Sundaland (Borneo, Sumatra,
Java and peninsular Malaysia; Corbet & Pendlebury
1992) and it is reported to be a poor ¯ier (Corbet &
Pendlebury 1992), suggesting particular vulnerability
to forest disturbance. In addition, both adult butter¯ies and larval food plants (Selaginella spp.) can be
recorded reliably from ground-based surveys, making them excellent model organisms for this type of
study. Transect techniques were used to investigate
butter¯y spatial distribution and abundance and to
quantify habitat requirements in undisturbed forest
habitats. Changes in availability of suitable habitat,
butter¯y spatial distribution, and butter¯y habitat
requirements were studied in areas that had been
selectively logged 8±9 years previously. Field work
coincided with one of the most serious droughts in
recent years on Borneo (coinciding with a marked
El NinÄo event), and although this drought was
severe, such droughts are by no means uncommon
in this region (Walsh 1996). Many satyrid butter¯y
species are known to be sensitive to changes in
humidity (Braby 1995), and butter¯y distributions
and abundances during the drought were compared
with data from a year of more normal rainfall
(1996).
Materials and methods
STUDY SITE
Fieldwork took place at Danum Valley Field
Centre, adjacent to the Danum Valley Conservation
Area and the Ulu Segama Forest Reserve, Sabah
0
(5 N, 117 50 E), between 22 August and 29
September 1997. The study area is within lowland
evergreen rain forest, dominated by dipterocarp tree
species (Marsh & Greer 1992), and average temperatures (26´7 C annual mean) and rainfall (2822 mm
year±1) are typical of the moist tropics (Marsh &
Greer 1992), with little monthly variation (Heydon
& Bulloh 1997). The Danum Valley Conservation
Area covers approximately 428 km2 of protected,
unlogged forest (Collins, Sayer & Whitmore 1991),
and is surrounded by extensive areas of production
forest, most of which have been selectively logged.
During the 1980s, logging methods in the study area
followed a modi®ed uniform system (Whitmore
1984) in which all commercial stems > 0´6 m diameter were removed using high lead cable and tractor extraction methods. Sabah timber yields are
generally high (averaging 118 m3 ha±1; Marsh &
Greer 1992), and although only about 7% of trees
are taken for commercial purposes, associated
damage can be severe, with between 60% and 80%
of remaining trees destroyed (Lambert 1992).
SURVEY TECHNIQUES
Transects were established along existing paths and
trails in two areas of forest: undisturbed forest
(transects 1 and 2, total length 4´3 km) and forest
that had been selectively logged 8±9 years previously, in 1988 and 1989 (transects 3 and 4, total
length 4´2 km; Fig. 1). Observation stations were
marked at 100-m intervals along each transect (81
stations in total). To allow ordination of di€erences
in disturbance and vegetation structure in the two
areas, the following data were recorded within a 30m radius of every station: number, circumference at
breast height, and distance from the station of the
10 nearest trees (excluding trees with circumference
less than 0´6 m at breast height), and estimated vegetation cover (%) at ground, low (2 m above ground),
understorey and canopy levels. In addition, estimated cover (%) of larval host-plant (Selaginella
spp.) within 10 m of every station and distance (m)
to the nearest stream were also measured at every
station. These measurements were used to calculate
nine variables (Table 1) which were normalized
where necessary (including arc-sine transformation
of percentages) and analysed by a principal components analysis (PCA), nested ANOVA and logistic
regression.
Ragadia makuta was surveyed along transects
using methods similar to those described for butter-
566
Selective logging
and butter¯y
distribution
Fig. 1. Location of transects (1±4) around Danum Valley Field Centre (star). Logged areas (with dates) to the east of the
River Segama are shown. All areas to the west of the River Segama are unlogged and lie within the Danum Valley
Conservation Area.
# 1999 British
Ecological Society
Journal of Applied
Ecology, 36,
564±572
¯ies in temperate regions by Pollard (1977) and used
in previous studies (Hill et al. 1995; Hamer et al.
1997). All adults of R. makuta observed during a 5min period within a 10-m radius of stations were
recorded, and butter¯ies seen within 5 m of the path
were also recorded whilst the observer was walking
between stations. Surveys were only carried out
between 10.00 and 14.00 h, corresponding with peak
¯ight activity, and only during good weather.
Although R. makuta is one of the most common
butter¯y species locally, it is nonetheless recorded
relatively rarely and, to avoid possible errors in estimates of presence/absence and relative abundance,
each survey was repeated four times and data were
combined for analysis. Total numbers of butter¯ies
recorded at each station also included butter¯ies
seen from paths, up to 50 m either side of stations.
Data from transects were used to investigate butter¯y habitat requirements and changes in butter¯y
spatial distribution and abundance resulting from
selective logging.
HABITAT REQUIREMENTS
Habitat requirements of R. makuta were investigated
in undisturbed forest using logistic regression, by
relating presence/absence of butter¯ies at each station to ®ve habitat variables: three factor scores
from the PCA, percentage cover of Selaginella and
distance to nearest stream. Variables were entered
into the model by forward stepwise selection, with
the signi®cance level of inclusion/removal of variables set at 5%.
567
J.K. Hill
Table 1. Mean scores for nine variables relating to vegetation structure and distribution of larval host-plants, and mean
scores for three main factors from PCA. Means followed by * are signi®cantly di€erent at the 5% level (ANOVA nesting
transect within habitat)
Unlogged
Variable
Mean
SD
Mean
SD
Number
Density (m±1)
Girth (m)
Ground cover (%)
Low-level cover (%)
Understorey cover (%)
Canopy cover (%)
Factor 1 (forest density)
Factor 2 (tree size)
Factor 3
Selaginella cover (%)
Distance to stream (m)
9´93
0´95
1´72*
0´40
0´58
0´65
0´41*
0´26*
0´32*
0´13
0´07
76´85
0´35
0´33
0´64
0´24
0´19
0´27
0´22
0´85
0´98
0´87
0´10
72´15
9´65
0´97
1´47*
0´43
0´55
0´60
0´17*
±0´26*
±0´33*
±0´14
0´07
68´05
1´27
0´28
0´48
0´29
0´19
0´22
0´15
1´09
0´92
1´11
0´10
77´95
The e€ects of selective logging on habitat requirements of R. makuta were investigated by comparing
its observed distribution within logged forest with
that predicted on the basis of habitat availability.
This was to investigate whether any changes in
abundance in di€erent habitats were due to di€erences in availability of suitable habitat, or to butter¯ies altering their requirements in di€erent habitats.
EFFECTS OF DROUGHT
Data on the distribution of R. makuta were also collected on transects in September 1996, using the
same protocol as that described above, at 65 of the
81 stations in logged and unlogged forest. These
data were compared with data collected in 1997, to
investigate the e€ects of drought on butter¯y distribution and abundance. Because data had been collected from fewer stations in 1996, and because no
habitat variables were measured in 1996, habitat
requirements of R. makuta were determined using
data from 1997 only. Data for mean monthly rainfall from March 1996 to August 1997 were obtained
from a meteorological station at the Danum Valley
Field Centre.
Results
FOREST STRUCTURE
# 1999 British
Ecological Society
Journal of Applied
Ecology, 36,
564±572
Logged
Table 1 shows the mean values for variables relating
to vegetation structure, distance to nearest stream
and cover of larval host-plants in the two forest
areas. Unlogged forest had signi®cantly larger trees
(as measured by girth) and greater canopy cover
(ANOVA nesting transect within habitat). Seven vegetation variables were analysed by a PCA. Distance
to the nearest stream was not included as a variable
in the PCA because it was not a direct measure of
vegetation structure. Percentage cover of Selaginella
was not closely correlated with any of the other
vegetation variables and so was also not included in
the PCA (Norusis 1990). PCA extracted three components of variation from seven vegetation variables
which accounted for 74´9% of the variability in the
data set. Factor 1 accounted for 38% of the variance and increased with (in order from greatest to
least important) increasing canopy and understorey
cover, decreasing cover at ground level and increasing number and density of trees. A high factor 1
score thus represented dense forest with a closed
canopy. Factor 2 accounted for a further 22% of
the variability of the data set and increased with
increasing girth of trees and increasing canopy
cover. Factor 1 therefore primarily measured density
of forest whereas factor 2 measured tree size. Factor
1 and factor 2 scores were signi®cantly higher in
unlogged forest than logged forest (ANOVA nesting
transect within habitat; Table 1). Factor 3 accounted
for a further 15% of the variance in the data set but
did not di€er between areas.
Results from ANOVAs showed signi®cant di€erences in vegetation measures within transects after
accounting for habitat e€ects. There were no di€erences in vegetation structure between transects in
unlogged forest (P > 0´1 in all cases), but in logged
forest transect 3 was in forest with signi®cantly larger but fewer trees, and was closer to streams, compared with transect 4 (Table 2). In addition, factor 2
from the PCA, which is also a measure of tree size
(see above), was also higher on transect 3 compared
with transect 4.
DISTRIBUTION AND ABUNDANCE OF
R. MAKUTA
Sixty R. makuta adults were seen at 32 of the 81 stations surveyed. There was no di€erence between
habitats in the number of stations where butter¯ies
568
Selective logging
and butter¯y
distribution
Table 2. Mean scores for nine variables relating to vegetation structure and distribution of larval host-plants, and mean
scores for three main factors from PCA from two transects in logged forest. Means followed by * are signi®cantly di€erent
at the 5% level (t-test following nested ANOVA)
Transect 3 (logged 1989)
Transect 4 (logged 1988)
Variable
Mean
SD
Mean
SD
Number
Density (m±1)
Girth (m)
Ground cover (%)
Low-level cover (%)
Understorey cover (%)
Canopy cover (%)
Factor 1 (forest density)
Factor 2 (tree size)
factor 3
Selaginella cover (%)
Distance to stream (m)
9´46
0´85*
1´62*
0´48
0´55
0´61
0´17
±0´42
0´07*
±0´33
0´08
44´04*
1´62
0´24
0´42
0´45
0´23
0´29
0´13
1´32
0´69
1´26
0´09
49´0
9´94
1´16*
1´24*
0´50
0´68
0´76
0´18
±0´02
±0´92*
0´16
0´06
104´06*
0´25
0´24
0´49
0´33
0´23
0´21
0´19
0´53
0´91
0´81
0´13
99´11
occurred (chi-square = 1´00, 1 d.f., P = 0´32) or
mean number of butter¯ies per station (ANOVA nesting transect within habitat, F1,77 = 1´25, P = 0´3).
However, there was a signi®cant di€erence between
transects within habitats (F2,77 = 4´81, P = 0´011)
and butter¯ies occurred most frequently on transect
3 in logged forest (chi-square = 9´15, 3 d.f.,
P = 0´027) but least frequently on transect 4, also in
logged forest, with transects in unlogged forest having intermediate values.
EFFECTS OF LOGGING ON HABITAT
REQUIREMENTS OF R. MAKUTA
Habitat requirements of R. makuta in unlogged forest (n = 41 stations; 14 occupied vs. 27 unoccupied
stations) were described from transect data using
logistic regression. Variables included in the analysis
were three factor scores from the PCA (see above),
percentage cover of Selaginella, and distance to
nearest stream. The model predicted 82´9% of presence/absences correctly (chi-square = 19´22, 2 d.f.,
P < 0´001). Ragadia makuta was more likely to
occur at stations close to streams in less dense forest, and the probability ( p) of R. makuta presence
was described by the following equation:
ln (1 ± p)/( p) = ±2´58 log stream distance (m)
(SE = 0´57) ±1´12 forest density (PCA factor 1)
(SE = 0´98) + 3´46 (SE = 1´53).
eqn 1
# 1999 British
Ecological Society
Journal of Applied
Ecology, 36,
564±572
The predicted probability (P) of R. makuta being
present at each station in logged and unlogged habitats was then calculated as:
P = 1/1 + e±z
eqn 2
where z = habitat requirements of R. makuta in
unlogged forest (equation 1).
Using equation 2, the predicted probability of R.
makuta being present did not di€er signi®cantly
between logged and unlogged areas (ANOVA nesting
transect within habitat, F1,77 = 1´19, P = 0´3) but
di€ered between transects (F2,77 = 4´85, P = 0´01)
and was signi®cantly higher on transect 3 in logged
forest than elsewhere (Table 3). In order to investigate whether habitat requirements were di€erent in
logged forest compared with unlogged forest, the
predicted probability of R. makuta being present
was set at P > 0´5 (there were only six stations with
probability values 2 0´05 of this cut-o€ point), and
the probability of R. makuta being present/absent
was compared with recorded presence/absence data
from transects. There was no di€erence between
habitats in predicted and recorded presence/absence
of R. makuta (chi-square = 2´59, 1 d.f., P = 0´11)
but there was a di€erence among transects (Table 3;
Table 3. Di€erences among four transects in unlogged and
logged forest in predicted and recorded presence/absence
of R. makuta at 81 observation stations. P is mean probability of occurrence. Means followed by the same letter
are not signi®cantly di€erent at the 5% level. `Correct' is
the number of stations where R. makuta was both recorded
and predicted present (using P > 0´5 as criterion for occurrence, see text), and also stations where it was not observed
and not predicted to occur. `Wrong' are cases when either
R. makuta was present but not predicted to occur, or when
it was absent but predicted to occur
Unlogged forest
Logged forest
Transect
1
2
3
4
P
Correct
Wrong
0´32a
18
3
0´40ab
16
4
0´55b
13
11
0´30a
14
2
569
J.K. Hill
chi-square = 8´51, 3 d.f., P = 0´037). Transect 3 in
logged forest had a greater number of stations
where the predicted presence of R. makuta did not
agree with recorded presence (`wrong' in Table 3).
These instances (11 stations) included both stations
where the butter¯y was predicted to occur but did
not (four stations), and stations where the butter¯y
was recorded but was not predicted to occur (seven
stations). Di€erences between observed and predicted occurrences on transect 3 indicate changes in
habitat requirements, and so di€erences between
these 11 `wrong' stations and 13 `correct' stations
were investigated in more detail. Stations where the
butter¯y was present but predicted absent had signi®cantly higher probabilities of occurrence (mean
probability = 0´34) than stations where the butter¯y
was both predicted and recorded absent (mean
probability = 0´22; t = ±3´09, 10 d.f., P = 0´012). In
contrast, there was no signi®cant di€erence in probability values between stations where the butter¯y
was predicted and recorded present, and stations
where it was predicted to occur but was absent
(mean probability = 0´81 and 0´78, respectively).
EFFECTS OF DROUGHT
During the 6 months from March to August 1997,
total rainfall at Danum was approximately 27% less
and there were approximately 28% fewer raindays
compared with the same period in 1996 (Table 4).
Corresponding with changes in rainfall, R. makuta
was nearly three times more abundant in 1996 (total
number recorded in 1996 = 71; total in 1997 = 26)
and was more widely distributed, being present at
26 stations (40%) in 1996, compared with only 14
stations (17%) in 1997. Stations where R. makuta
occurred were also more isolated in 1997 (mean distance between occupied stations = 313´3 m,
SD = 292´5) compared with 1996 (mean = 142´3 m,
SD = 98´7; t-test with unequal variance, t = ±2´19,
15´86 d.f., P = 0´043). The pattern of presence/
absence of R. makuta along the transect was not signi®cantly di€erent from a random distribution in
1997 (runs test, z = ±0´38, P = 0´7), but occupied
stations had a signi®cantly clumped distribution in
1996 (z = ±2´40, P = 0´017).
There was no di€erence between logged and
unlogged habitats in the proportion of stations
where R. makuta was present/absent both years and
stations where it disappeared/appeared in 1997
(P > 0´3 in both cases). Stations where R. makuta
had been present in both years (n = 10) were compared with stations where it had disappeared in
1997 (n = 16) using logistic regression to investigate
the importance of four habitat variables [percentage
cover of Selaginella, distance to nearest stream, forest density (PCA factor 1) and tree size (PCA factor
2)]. The regression model predicted 77% of presence/absence correctly (chi-square = 16´40, 1 d.f.,
P < 0´001) and R. makuta was more likely to have
disappeared from a station in 1997 if the station was
far from a stream. The probability of disappearance
( p) is described by the following equation:
ln (1 ± p)/( p) = 3´62 log stream
(SE = 1´43) + 4´37 (SE = 2´04).
distance
(m)
eqn 3
In contrast, stations where R. makuta was present
in 1997 only (n = 5) had a higher cover of larval
food plant compared with stations where butter¯ies
were absent in both years (n = 34; chi-square =
4´36, 1 d.f., P = 0´037; model predicted 90% presence/absences correctly, although these results
should be treated with caution given the small sample size in one category). The probability of appearance ( p) is described by the following equation;
ln
(1 ± p/p) = 16´96
Selaginella
(SE = 11´43) ± 2´46 (SE = 0´63).
cover
(%)
eqn 4
Discussion
EFFECTS OF SELECTIVE LOGGING
There were signi®cant di€erences in vegetation
structure between logged and unlogged areas showing that the e€ects of disturbance were still evident
8±9 years after selective logging. Unlogged forest
had signi®cantly larger trees (measured as girth at
breast height) and greater canopy cover, and two
PCA factors measuring forest density and tree size
were signi®cantly higher in unlogged forest, compared with selectively logged areas. There was also
signi®cant heterogeneity in vegetation structure
Table 4. Rainfall data from Danum Valley Field Centre during March±August in 1996 and 1997 (data kindly supplied by
the Hydrology Project, University of Manchester, UK)
Monthly rainfall (mm)
# 1999 British
Ecological Society
Journal of Applied
Ecology, 36,
564±572
1996
1997
Mean
SD
Total
Mean
Number of raindays per month
SD
Total
173´8
127´5
81´0
68´3
1042´6
764´7
18´8
13´5
5´5
5´9
113
81
570
Selective logging
and butter¯y
distribution
# 1999 British
Ecological Society
Journal of Applied
Ecology, 36,
564±572
between transects within logged forest. Logging
records indicated that similar timber volumes were
extracted from areas around transects 3 and 4 (75±
95 m3 ha±1; Costa & Karolus 1992), but these data
were averaged over areas of approximately 2000 ha,
which obscures small-scale di€erences in logging
intensity at a scale relevant to this study. Selective
logging typically results in a mosaic of forest disturbance ranging from areas of severe disturbance
along tractor tracks and around timber collection
points, to areas of minimal disturbance and relict
patches of primary forest (Whitmore 1991).
Transect 3 was close to streams and passed through
a river catchment area containing areas that were
less severely logged (Steyshen Baru; Douglas et al.
1992). Di€erences among transects in logged forest
in this study thus probably largely re¯ected this variation in disturbance, and the presence of smaller
trees on transect 4 suggests that a larger volume of
timber was extracted from around transect 4.
However, transects in logged forest were also
slightly further apart than in unlogged forest
(Fig. 1), and although the distance between transects
in logged forest was small (< 500 m at the nearest
point), this may also have contributed to observed
heterogeneity between transects within logged forest.
Levels of disturbance within logged forests are also
related to other topographical and landscape features, and high habitat heterogeneity is typical of
selectively logged areas throughout the tropics
(Whitmore 1991).
The importance of sampling widely to take
account of habitat heterogeneity has been recognized (Sparrow et al. 1994). In this study, butter¯ies
were recorded from an area of approximately 10 ha
(combining areas of observation stations and walks
between stations), and the use of transects (total
length 8´5 km) meant that a wide variety of habitats
and microclimates (riverine, canopy gaps, di€erent
aspects, etc.) was surveyed. Results from this study
highlight the importance of sampling over a large
area for a relatively sedentary subcanopy species
such as R. makuta, and sampling widely may be
even more important for more mobile species.
Transect data showed that R. makuta adults were
always recorded in areas of closed-canopy forest,
and within this habitat they preferred sites in damper areas (close to streams) with high cover of
Selaginella and, to a lesser extent, sites with less
dense forest (low PCA factor 1 score). There was no
di€erence between logged and unlogged habitats in
spatial distribution or abundance of butter¯ies, and
also no di€erence in cover of Selaginella or proximity to streams, although logged forest had lower
PCA factor 1 scores. However, abundance of R.
makuta di€ered among transects and was highest on
transect 3 in logged forest, where stations were closer to streams, but was lowest in more severely
logged forest (transect 4), indicating that the e€ects
of selective logging may have been apparent in this
species in some areas 8±9 years after logging. In this
study, measuring vegetation structure and availability of larval resources in di€erent areas within each
habitat was crucial to understanding the responses
of R. makuta to habitat disturbance. These results
stress the importance of quantifying vegetation
structure in order to determine the severity of forest
disturbance and to allow interpretation of the e€ects
of disturbance on di€erent species.
HABITAT REQUIREMENTS AND
DISTURBANCE
Habitat requirements of R. makuta did not di€er
between logged and unlogged areas, as measured by
the proportion of stations where the butter¯y was
both predicted to occur and was recorded present.
This suggests that a lack of any observed di€erences
in abundance and distribution between logged and
unlogged areas was not due to butter¯ies changing
their habitat requirements in response to disturbance. There was, however, a signi®cant di€erence
among transects, and transect 3 in logged forest had
a larger number of stations where the prediction of
presence/absence of butter¯ies did not agree with
the recorded distribution. These cases included both
stations where the butter¯y was predicted present
but was absent, and stations where the butter¯y was
present but predicted absent, making any e€ects of
logging on habitat requirements dicult to interpret.
Although sample sizes were small, there is some evidence that butter¯ies were occupying stations in
more marginal habitats in logged forest, but that
they were not moving into areas of very unsuitable
habitat (predicted occurrence was signi®cantly
higher at stations where the butter¯y was present
but predicted absent compared with stations where
the butter¯y was both predicted and recorded
absent). This indicates some degree of ¯exibility in
habitat requirements in this species. Such ¯exibility
could potentially reduce the impacts of selective
logging, but any e€ect in this study was relatively
small and broad habitat requirements did not di€er
between habitats.
EFFECTS OF DROUGHT
A marked decrease in rainfall in 1997 corresponded
with signi®cant declines in both abundance and
local distribution of R. makuta. Compared with a
year of more normal rainfall, populations contracted to damper areas close to streams and to
areas with high cover of the larval host-plant,
although there was no di€erence between logged
and unlogged areas in the e€ects of the drought.
Similar patterns of population contraction in
571
J.K. Hill
response to a reduction in humidity and moisture
availability have been observed in other satyrid species from temperate areas (Sutcli€e et al. 1997) and
from tropical areas with marked wet/dry seasons
(Braby 1995), but have not been previously recorded
from less seasonal tropical regions. Compared with
a year of more normal rainfall, butter¯y distribution
was not clumped in 1997, and stations with butter¯ies were further from other occupied stations, suggesting increased fragmentation and isolation of
local populations. In temperate regions, small isolated populations are more prone to local extinction
(Thomas, Thomas & Warren 1992) and, although
the degree of isolation in this study was relatively
small (the maximum distance between occupied stations was 1´1 km), the reported poor ¯ight of R.
makuta (Corbet & Pendlebury 1992) suggests that it
may be vulnerable to population fragmentation at
this scale. Few studies investigating the e€ects of
disturbance have taken place over sucient time to
take account of widespread changes in environmental conditions, and whether populations in logged
and unlogged areas recover at an equal rate from
such events has not been investigated.
BUTTERFLY CONSERVATION IN MALAYSIA
The consequences of degrading large forest areas for
the survival of insect species are poorly understood
(Sayer & Whitmore 1991), and the ability of di€erent species to survive and reproduce in disturbed
forest is therefore of great interest. In the near
future, most remaining production forest in
Malaysia will have been through one cycle of selective logging and will be in a period of regeneration
before being selectively logged again (Lambert
1992). In Indonesia, butter¯y diversity and biogeographic distinctiveness were signi®cantly lower 5
years after selective logging compared with undisturbed forest (Hill et al. 1995), and results from this
study show that 8±9 years after logging di€erences
in vegetation structure were still evident and butter¯y distribution and abundance were lower in the
most severely disturbed areas. Further work is
needed to see if populations and communities come
to resemble those in unlogged forest after longer
periods of recovery, or whether repeated selective
logging will result in a reduction of diversity and
loss of species with high biogeographic and/or taxic
distinctiveness
(Vane-Wright,
Humphries
&
Williams 1991), a more important consideration
than diversity per se in terms of conservation of global biodiversity.
# 1999 British
Ecological Society
Journal of Applied
Ecology, 36,
564±572
Acknowledgements
This work was in collaboration with Dr Chey Vun
Khen, Forestry Research Centre, Sepilok. I thank
Keith Hamer, Tom Sherratt and Helen White, and
also Andrew Davis and all at Danum Valley for
making my stay so enjoyable. I also thank Yayasan
Sabah (Forestry Upstream Division), the Danum
Valley Management Committee, the State Secretary
(Internal A€airs and Research Oce), Sabah Chief
Minister's Department, and the Economic Planning
Unit of the Prime Minister's Department of Kuala
Lumpur for permission to conduct research in the
Danum Valley, Sabah. This study is project number
DV157 of the Danum Valley Rainforest Research
and Training programme and was supported by a
British Ecological Society research travel grant. This
is publication A/224 of the Royal Society SouthEast Asia Rainforest Research Programme.
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