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EVALUATION OF DAMAGE CAUSED BY ELEPHANTS
(Elephasmaximusmaximus) TO THE WOODY VEGETATION IN
UDAWALAWE NATIONAL PARK
INTRODUCTION
Despite its small size, island of Sri Lanka grass, low woody plants, and forest. Elephants
2rarely forage in one area for more than a few days
(65,610 km ) supports several viable populations
at a stretch (Kumar et al., 2010).Elephants eat a
of elephants estimated to number between 3,500
wide variety of species of vegetation. They
and 4,000 animals(de Silva et al., 2011). To
prefer grasses, but they also consume bark, roots,
conserve elephant and other wildlife, Sri Lanka
leaves, and stems of trees, vines, and shrubs.
has set aside about 12.5% of land under
Elephants' preference for certain plant species
protection (Santhipillai et al, 2003). Although it
appears to be an important factor dictating it's
is a well-known fact that elephants are
movements in some habitats (Osborn, 2002).
herbivores, a comprehensive study has not been
Sometimes, elephants consume the bark of
carried out to estimate the damage caused to
woody plants that can result in the death of trees
the woody vegetation by elephants in Sri
(Thomson, 1975). Most of an adult's activities
Lanka. However, few studies have been
involve moving toward the forest and eating
conducted concerning their food habits,
food. They eat in the morning, evening, and night
behavior and population structure (Santhipillai
but rest during the hottest part of the day. An
et al, 2003; Santhipillai and Jackson,
average day's intake is 150 kg of vegetation, of
1990; Vancuylenberg, 1977).
which only about 44% is actually digested (with
Asian elephants mainly prefer scrub forest,
the aid of symbiotic gut bacteria) and defecates
although their habitat can vary. They can be
about 80 kg of it per day (Sukumar, 2006). In
found in the jungle, but generally frequent in the
southeast Sri Lanka elephants spend about 17 to
open grasslands. They prefer areas that combine
ABSTRACT - Elephants can have profound effects on the structure and composition on
woodlands. In this study, the damage caused by elephants to woody plants in the Udawalawe
National Park was investigated. The study was carried out in three major habitat types in the
Udawalawe National Park, namely grasslands, scrub forests and tall forests. Five plots were
established in each habitat. Types of damages caused to the woody plants were categorized in to
six main groups viz, crown damage, bark removal, branch damage, pushing down, partially
damaged and totally damaged. Plant species which were highly vulnerable for elephant
damages and the areas in which elephant damages are high were identified. These results were
used to identify the food preferences of elephants, highly recorded damage types and the area
which they prefer to stay. Based on the intensity of damages the study revealed that, crown
damages, branch damages, pushing down and bark removal as highly recorded damage
categories in the three habitats. Bauhinia racemosa, Phyllanthus polyphyllus, Limonia
acidissima and Diospyros ovalifolia were the species that were more susceptible for elephant
damages and the grassland habitats were the areas where elephant damages were high.
1 2 3
N. ANGAMMANA , K.B. RANAWANA and G. ELLEPOLA
1 No.215/6, Hulangamuwa Road, Matale, Sri Lanka
2Department of Zoology, Faculty of Science, University of Peradeniya, Sri Lanka
3Open University of Sri Lanka, Nawala, Nugegoda
WILDLANKA Vol. 3, No. 1, pp. 20 - 30, 2015.
Copyright 2015 Department of Wildlife Conservation, Sri Lanka.
KEY WORDS : Elephas maximus maximus, Woody Vegetation, Grasslanda, Scrub Forests and
Tall Forests.
19 h/day feeding. Furthermore, their feeding ranges from about 100m on the plains to 373m at
cycle consists of three successive phases, namely top of Ulgala.
(1) rapid movement and low feeding rate, (2) Since the park is located in the dry zone,
little movement and high feeding rate, and (3) conditions are characterized by annual drought
certain amount of movement and relaxed feeding coinciding with the south-west monsoon. Mean
(Vancuylenberg, 1977). annual rainfall is about 1524mm. Mean day and
0 0
High elephant densities are associated with night temperatures are 29.4 and 23.9 C,
decline in large trees(Barnes, 1985; Osborn, respectively. The park was originally forested,
2002). A 25-year study in Africa shows that however due to anthropogenic activities the
elephants affected the size distribution of natural vegetation has been affected and now
savanna woody component much more than the grasslands and scrubs dominate a major part of
tree densities (Van de Vijver et al, 1999). The the area. Much of the forests were destroyed by
extent to which elephants affect the woody chena cultivation
vegetation will depend though on other factors
such as tree density, age structure (Barnes, 2. Methods
1985), other herbivores (Belsky, 1984) and fire Fifteen plots, each with an extent of 250
2
(Pellew, 1983). Elephants can have profound m were demarcated randomly (five in each area;
effects on the structure and composition on grasslands, scrub forests and tall forests) to cover
woodlands (Barnes, 1985). Despite this impact, the total extent of the study area. Study plots
relatively little is known about the factors, were selected close to park roads so as to avoid
nutritional or otherwise, that in fluence food and long walks across the park which is dangerous,
habitat selection in elephants (Holdo, 2003). due to the presence of large number of elephants
Knowledge of these factors can help determine in the park. By using the survey tape of 100 m
the role of elephant–tree interactions in shaping and nylon rope of 100 m, 50mx50m plots were
forest structure and species composition, and established (Figure 1). The coordinates of the
may assist managers seeking to address plots were obtained using the Global Positioning
problems associated with overexploitation of System (GPS). Subsequently all woody plants
certain tree species by elephants. over 10cm diameter at breast height (dbh) and
saplings which were in the study plots were
MATERIALS AND METHODS enumerated. Woody plants species less than 150
1. Study Site cm dbh formed part of the lowest canopy-layer.
The Udawalawe National Park is next only in All the plant species found in the experimental
popularity to the Yala National Park in the plots were identified to species level. Herbarium
Southern region, and acts as a refuge for a large specimens were prepared of the species that
number of herbivores, especially for elephants could not be identified in the field and they
where elephants can usually be observed even at were later identified comparing the to the
mid-day.There are about 275-350 elephants authenticated specimens at the National
living in the park currently (Department of herbarium.
Wildlife Conservation, 2010). Considering the To assess the damage caused to the plants the
extent of the Park which is about 32,315 ha affected plants were broadly categorized in to six
2
(323.15 km ), the elephant population density is main groups, namely, (1) Crown damage - main
fairly high compared to the other areas in the branch or the canopy of the tree being pulled or
country. The Udawa lawe National park twisted without completely broken away from
comprises of dry mixed ever green forests and the plant; (2) Bark removal - partial or complete
extends to Sabaragamuwa and Uva provinces. peeling of the bark of the main tree trunk or any
The park is surrounded by cultivated land and it of the branches; (3) Branch damage- complete
0
lies between geographical co-ordinates 6 24- breaking of branches other than the main tree
0 0 0 trunk or the leading stem of the shrub; (4)
6 35N', 80 44 -80 58'E. Altitude of the land
WILDLANKA [Vol. 3, No 1
21
FIGURE 1: Map of the Udawalawe National Park showing the study sites
ELEPHANT DAMAGED TO WOODY VEGETATION UNP
March, 2015] 22
Pushing down - trees and shrubs being partially damages recorded. Other than crown damage,
or completelyuprooted; (5) Partially damaged - the damages caused as branch damages, bark
part of the tree totally damaged; (6) Damaged removal and pushing away was fairly high in the
likely to die - plants which are severely damaged grassland (Figure 2).
and unable to recover from the damage.Any
woody plants showing one or more of these
damage types were assumed to be utilized by
elephants (Ishwaran, 1983). For the final
calculations, data from the 5 plots in each habitat
werepooled and all the damages were calculated
by using following equations.Collected data
were analyzed by using Microsoft excel.
In the scrub forest habitat, branch damages
and pushing down were the highest which,
accounted for 37.3% and 35.8% damages
respectively. Unlike in the grassland, crown
The most preferred species was determined damages were low (16.4%) in the scrub forest.
by the number of damages recorded. If the No totally damaged or partially damaged trees
recorded number of damages for a species is high were observed in the scrub forest habitat (Figure
then it was considered as a preferred species of 3)
food for elephants. After collecting data from
each habitat the total amount of damage was
compared with each area in order to get an idea
about the habitat where the damages are high. It
was done by using the following equation and the
results were compared:
RESULTS
Bauhinia recemosa was the most abundant
tree species in grasslands. Phyllanthus Crown damages were highest in the tall
polyphyllus which forms small islands of shrubs forest(40.47% of the total value). Other than
in the grasslands was the second most abundant crown damages, branch damages and pushing
species in grassland habitats. In comparison down were the damage types which accounted
Carmona retusa, Flueggea leucopyrus, and for higher level of damage accounting for
Memecylon umbellatum were the most abundant 27.78% and 24.07% of the damages respectively.
species in the scrub forests sampled. Further, Bark removal of trees, partially damaged trees,
Croton laccifer, Diospyros ovalifolia and and totally damaged trees were recorded in very
Mallotuseriocarpus were the dominant species low numbers (Figure 4).
in the tall forests sites sampled (Appendix I).
In the grasslands crown damage was more
prominent and it accounted for 34% of the
FIGURE 2: Percentage damage in the grassland habitat
FIGURE 3: Percentage damage in the scrub forests
WILDLANKA [Vol. 3, No 123
In the grasslands Bauhinia recemosawas
most affected by branch damages (75% damage).
Considerable amount of branch damage (12%)
wa s a lso ob serv ed in the P hyll anth us
polyphyllus. Damages caused to other plants
were of comparatively low in intensity (Figure
5a).In the scrub forest habitat branch damage
was heavy on Phyllanthus polyphyllus (32%).
Branch damage to Bauhinia recemosa and
Flueggea leucopyrus in the scrub forests were
also in high in ten sit y (16% a nd 12%
respectively). Damages caused to Polyalthia
Of all recorded crown damages in the korinti and Diospyros ovalifolia were of equal
grassland, 78% was observed in Bauhinia intensity, which was about 8% (Figure 5b).
racemosa species which is comparatively a
large value. Damages caused to the crowns of
Li m o n ia a c idissi m a a nd P h yllant h u s
polyphyllus were of equal intensity with8%.
Out of all recorded crown damages in the tall
forest habitat, 86% were observed in the
Phyllanthus polyphyllus species. Two species,
namely, Diospyros ferra, and Manilkara
hexandras howed an equal degree of intensity,
be i n g 5 % , w h ile Diosp y ros ova l ifolia
represented 4% of the total recorded damages
(Figure 5).
Furthermore, of all recorded branch damages in
the tall forest habitat, 80% damage was observed
in Phyllanthus polyphyllus. Bauhinia recemosa
and Premna tomentosa species also had high
degree of branch damages in the tall forests (13%
and 7% respectively).Other species found in the
tall forest habitat were relatively undamaged
(Figure 5c).
FIGURE 4: Percentage damage in tall forests
FIGURE 5: Intensity of crown damages in grassland
and tall forest habitats. (Crown damages for the
scrubland habitat were not considered due to its lower
intensity comparatively to other two habitats).
FIGURE 5a: Intensity of branch damages in grasslands
FIGURE 5b: Intensity of branch damages in Scrub
Forest
March, 2015] 24
ELEPHANT DAMAGED TO WOODY VEGETATION UNP
FIGURE 5c: Intensity of branch damages in Scrub
Forest
In the Scrub forest habitat, pushing down was had a notable extent of damage with the values of
prominent in Schleicheraoleosa, which claimed 7.41%, 7.41%, 3.70% and 3.70% (Figure 7a, 7b,
up to 17% of the total recorded value. The 7c).
damages ca used to Bauhinia recemosa ,
Diospyros ovalifolia and Carmona retusa were
of equal intensity which was 13%. In
comparison to that in the tall forest habitat,
pushing do wn wa s highly re cor ded i n
Phyllanthus polyphyllus which claimed up to a
38% of the total recorded value. Diospyros
ovalifolia claimed 23% of the total recorded
da m a g e s. C o rd i a di c h o t oma, Mallot u s
eriocarpus, Eugeiabracteata, Mischodonzey
lanicus and Vitexnugundo were damaged in
equal value which was 8% in each species
(Figure 6).
Considering the tree species found in
grassland, and the recorded extent of damages,
76% of the total recorded damages were
observed in the Bauhinia recemosas, 8%, 6% and
The main types of damages observed in the
sites include crown damage, branch damage,
pushing down and bark removal. In addition to
that trees with partially damaged and damaged
likely to cause tree death were observed in lower
4.67% of the total recorded damages were numbers (Table 1).
observed in Limonia acidissima, Phyllanthus Highest number of damages to the woody
polyphyllus and in Eucalyptus camaldulensis plants was observed in the grassland which was
respectively. The tree species found in scrub 55%. of the total recorded damages observed. In
forest habitat and the recorded extent of scrub forest habitat and tall forest habitat damage
damages, 16.92% of the total recorded damages percentages were 25% and 20% respectively
were observed in the Bauhinia recemosa, (Figure 8)
13.85%, 9.23% 7.69%, and 6.15% of the total
recorded damages were observed in Phyllanthus
polyphyllus, Schleichera oleosa, Diospyros
ov ali foli a and in Fl uegg ea leu cop yrus
respectively. In the tall forest habitat Phyllanthus
polyphyllus were the highly damaged species.
Out of all recorded damages 66.67% were
recorded in this species. Diospyros ovalifolia,
Bauhinia racemosa, Diospyros ferrea and
Cordia dichotoma were the other species which
FIGURE 6: Intensity of branch damages in Scrub
Forest
7a Grassland Habitat 7b Tall Forest Habitat
7c Scrub Forest Habitat
FIGURE 7: Intensity of total damages to the woody
plants recorded in all three habitats.
WILDLANKA [Vol. 3, No 125
FIGURE 8: Intensity of elephant damages to the
woody plants recorded in three habitats.
Discussion
The structure and composition of a forest can be of the damages in the grassland habitat where
changed due to elephants, fires and herbivore smaller plants existed.
activity (Thomson, 1975). Among these, In the Udawalawe National Park the grassland
elephants are major agents of habitat change, was dominated by Bauhinia recemosa and
regulating the balance between the woody over Phyllanthus polyphyllus while Carmona retusa,
story and the underlying grass swards (Laws, F l u egg e a leuc o p y r us a n d M e m e cylo n
1970). Elephants reduce the abundance of large umbellatum were recorded in higher numbers in
trees by pushing them over and stripping bark. the scrub forest. The relative density of Croton
Elephant- woody plant damages can convert laccifer, Diospyros ovalifolia and Mollotus
closed woodlands into open grassland in only a eriocarpus were high in the Tall forest habitat.
couple of decades (Mc Naughton et al., 1988). Analysis of the results reveals that Bauhinia
Various attempts have been made to study the recemosais the most preferred species in the
impact on woody vegetation by elephants (Laws, grassland habitat. It's higher abundance in the
1970; Struhsaker, 1996; Ishwaran, 1983; grassland habitat also may be another reason for
Osborn, 2002; Holdo, 2003). A study done in th is p refer e nce. Li m o nia acidi s sima,
Kibale, Africa (Wing and Buss, 1970) showed Phyllanthus polyphyllus, and Cassia fistula were
that 20.8% stems examine had damaged by the other species which were relatively abundant
elephants and it is consistent with our findings in in the study site. Eucalyptus camaldulensis were
the Udawalawe National Park with more than only confined to a certain area where these trees
50% damages to stems and branches. Usually in were planted by villagers during the chena
rainforests the greatest impact of elephants on cultivations in the area several years back. But
woody vegetation and forest dynamics is on the still certain extent of damage was observed in
smaller and younger plants (Wing and Buss, these plants.
1970) and it is true for a mixed evergreen forest Most preferred species in the scrub forest
like the Udawalawe National park showing 55% habitat was again Bauhinia recemosa. Unlike in
TABLE 1: Intensity of damage types observed among all woody plants
March, 2015] 26
ELEPHANT DAMAGED TO WOODY VEGETATION UNP
the grassland habitat Bauhinia recemosa was not fertile soils, such as species associated with
highly abundant in scrub forests (Appendix I), termite mounds (Holdo, 2003). Therefore, plant
but still higher feeding intensity was observed. nutrient analysis should be carried out in order to
Phyllanthus polyphyllus was also damaged to a get into clear conclusions of the food preference
certain extent, but still relative density of this of elephants.
species was low. Schleichera oleosa, Diospyros In this study, most elephant damage to
ovalifolia, Flueggea leucopyrus, Carmona trees can be classified as breakage (crown
retusa, Sapindus emerginata, Memecylon damage- 31% and branch damage- 29.89%) of
umbellatum and Cassia fistula were the other total utilization. This type of damages is usually
species which were damaged by elephants not fatal, but it probably affects the subsequent
showing their preference on these species as growth rate and form of the tree (Struhsaker,
fodder. 1995). As Laws et al., (1975) emphasize,
However, Phyllanthus polyphyllus was removal of the lead stem by elephants probably
the most preferred species in the tall forests. suppresses growth in young trees which results
Relative abundance of Phyllanthus polyphyllus in suppressed forest regeneration with all of its
was not very high even though large number of implications for species composition and
damages was observed. Higher extent of community ecology.
damages in Diospyros ovalifolia may be due to
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Appendix 1.Relative density of dominant tree species found in the study sites of Udawalawe National
Park
WILDLANKA [Vol. 3, No 129
Appendix I ctd;
March, 2015] 30
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