Journal of Threatened
Taxa | www.threatenedtaxa.org | 26 February 2025 | 17(2): 26487–26493
ISSN 0974-7907 (Online)
| ISSN 0974-7893 (Print)
https://doi.org/10.11609/jott.9220.17.2.26487-26493
#9220 | Received 19 June
2024 | Final received 26 December 2024 | Finally accepted 20 January 2025
Diet and nutrient
balance of wild Asian Elephants Elephas maximus in Nepal
Raj Kumar Koirala
1 & Sean C.P. Coogan
2
1 Department of Park
Recreation and Wildlife Management, Institute of Forestry, Tribhuvan University,
Pokhara, Nepal.
2 Department of Natural
Resource Science, Thompson Rivers University, Kamloops, BC V2C 0C8, Canada.
1 raj.koirala@pc.tu.edu.np
(corresponding author), 2 sean.c.p.coogan@gmail.com
Editor: Heidi Riddle, Riddle’s Elephant and Wildlife
Sanctuary, Arkansas, USA. Date of publication: 26 February
2025 (online & print)
Citation: Koirala, R.K. & S.C.P. Coogan (2025). Diet and nutrient balance of wild Asian
Elephants Elephas maximus in Nepal. Journal
of Threatened Taxa 17(2): 26487–26493. https://doi.org/10.11609/jott.9220.17.2.26487-26493
Copyright: © Koirala & Coogan 2025. Creative Commons Attribution 4.0 International License. JoTT allows unrestricted use, reproduction, and
distribution of this article in any medium by providing adequate credit to the
author(s) and the source of publication.
Funding: None.
Competing interests: The authors declare no competing interests.
Author details: Raj Kumar Koirala, PhD, is a professor at the Institute of Forestry, Pokhara Campus, Tribhuvan University, Nepal. He specializes in teaching courses on conservation biology, wildlife and protected area management, forest zoology, ornithology, and mammalogy. Dr
Sean Coogan
is a postdoctoral researcher, Department of Natural Resource Science, Thomson Rivers University, British Columbia, Canada. He specializes in wildlife, nutritional, and fire ecology.
Author contributions: RKK—conceptualized the project, Written the ms, data analysis. SC—analysed, reviewed.
Acknowledgements: We gratefully acknowledge the Rufford Foundation for their generous support of our previous research on elephants, which served as a significant source of inspiration for the completion and publication of this work. Their encouragement and commitment to conservation research have been invaluable in advancing our understanding and efforts in this field.
Abstract: We estimated the
nutritional content of major wild (n = 22) and agricultural crop plants (n = 3)
consumed by Asian Elephants Elephas maximus in Nepal during the wet and
dry seasons, respectively. We then used nutritional geometry to explore the
macronutrient balance of these plant species, as well as the overall diet of
elephants in both the dry and wet seasons. Furthermore, we compared the diet of
the Nepal elephants with the previously published diet of Indian population of
elephants. We found that despite intraspecific and seasonal variation, the overall
diet of elephants was relatively stable in protein (P) intake relative to
non-protein macronutrients (fat + carbohydrate; non-protein (NP)), and neutral
detergent fibre (NDF) between the wet (16% crude
protein (CP): 26.7 % NP: 57.3% NDF; and, 10.4% CP: 13.7% NP: 75.7% NDF) in dry
season, which suggests protein intake prioritization in support of previous
work on captive elephants. Furthermore, the diet of Indian population of
elephants (wet season: 16.0%P: 22.5%NP: 61.4%NDF and dry season: 11.1%P: 18.0 %NP:
70.7 %NDF)
showed a similar pattern to the Nepal elephants, suggesting active regulation
of macronutrient and NDF intake across populations despite differences in food
consumed as part of their diets. Importantly, NDF intake in addition to
non-protein macronutrients is likely necessary for elephants to stabilize their
protein intake balance; thus, it is important to consider a multidimensional
nutritional perspective in elephant conservation planning. The study has
concluded that in a well-managed seasonal habitat, elephants can regulate their
preferred macronutrient and NDF intake from available natural food plants
without resorting to agricultural crop depredation.
Keywords: Crop, depredation, Elephantidae, macronutrient balance, Mammalia, NDF, nutritional
geometry, right angled mixture triangle.
Introduction
The diet and
nutritional demands of wildlife are crucial aspects to consider when
formulating conservation and management strategies. Foraging, however, is a
complex process, involving the inter play of physiological and behavioural factors with an animal’s multidimensional
nutritional environment (Raubenheimer et al. 2009;
Simpson & Raubenheimer 2012). The Asian Elephant Elephas
maximus is a species of conservation concern often involved in food-related
human-elephant interactions (Desai 1991) through crop depredation (Santiapillai & Jackson 1990; Nyhus
& Sumianto 2000). Recently, studies of captive
Asian Elephants suggest that they regulate their intake of multiple nutrients,
with protein (P) intake more tightly regulated relative to non-protein
macronutrients (fat + carbohydrate; NP) and fibre
(NDF; (Koirala 2018). This type of nutrient regulation, however, has not been
explored in wild elephant populations.
In this paper, we
estimated the proximate nutritional content of plants consumed by migratory and
resident elephants during the wet and dry seasons in the far eastern region and
central region of Chitwan National Park (CNP) and Parsa
National Park (PNP) of Nepal. The consumed plants were identified through
feeding sign survey and micro-histological analysis of dung, and also based on
a previous study (Koirala et al. 2016). We used nutritional geometry (i.e.,
right-angled mixture triangle (RMT); Raubenheimer
2011) to explore the proportions of macronutrients and fibre
in the seasonal food plants and diets of elephants, including both natural and
agriculture crop plants, to evaluate evidence for nutrient intake regulation
similar to previous studies. Furthermore, we used published literature on the
diet of wild elephants in India (Das et al. 2014) to evaluate if they showed
similar dietary patterns to the Nepal elephants, which might suggest active
regulation of macronutrient and NDF intake across populations despite consuming
different diets.
Materials and Methods
The CNP (952.632 km2)
and PNP (637.37 km2) are two of Nepal’s protected areas,
and are situated in the south-central region of the country (Koirala et
al. 2016). On the other hand, Nepal gets migratory elephants from northern Bengal
of India (Koirala et al. 2015) in the forests of the eastern district of Jhapa. We collected food plant species of elephants’ diets
for nutritional analysis based on our previous study on food preference, which
identified 57 plant species (12 grasses, five shrubs, two climbers, one herb,
and 37 tree species) consumed by elephants (Koirala et al. 2016
). However, only the most preferred species (n = 22) and three
agriculture crop plants were collected for proximate nutrient analysis (Table
1). Plant and crop samples were collected during the late rainy (“wet”) season
(August/September 2013) and summer “dry” season (March/April 2014) from
elephant habitat, where habitat was determined by the presence of elephant
foraging signs and direct observation. The wet season collection period
coincided with the beginning of crop raiding time in late monsoon season with a
peak in pre-winter, while April/May was the beginning of crop raiding in the
dry season. After collection, samples were air-dried and kept in paper bags for
transport to the laboratory. The proximate nutritional estimates were analysed in the laboratory of Nepal Agricultural Research
Centre and Nepal Environmental and Scientific Services, Kathmandu, Nepal,
following standard methods (AOAC 2012) for crude protein (Kjeldahl;
CP), ether extract for lipid (Soxhlet extraction; EE), fiber (digestion method;
NDF), and ash. Non-structural carbohydrate (NSC) was calculated by difference.
To correct for indigestible waxes and lipids in plants consumed, we subtracted
1% from EE to estimate crude fat (CF) following Rothman et al. (2012).
Proportional data were transformed using a “logit” transformation to
approximate normality before running the stat test.
We used the Right angled mixture triangle (RMT) to investigate the
proportion of macronutrients and NDF in the food plants and seasonal diet of
elephants. Following Koirala et al. (2016), we plotted NP and NDF on the x- and
y-axis of the RMT, respectively, while CP was represented on the implicit axis
(z) which varies inversely with distance from the origin (Raubenheimer
2011). Macronutrients and NDF were expressed as a percentage of the sum of each
(i.e., non-structural carbohydrate + neutral detergent fibre
+ lipid + protein) on a dry matter basis. NDF was included in the analysis,
because elephants derive energy from fibre through
hindgut fermentation (Anguita et al. 2006). We
estimated the seasonal mixture space provided by the plant foods by forming
minimum convex polygons around food points for each season.
We determined the
overall macronutrient balance of seasonal diets by weighing the nutritional
estimates for each plant species by the relative utilisation
percentage determined as described by Koirala et al. (2016), which is the
product of the frequency of occurrence and rank score of each plant in the
micro-histological analysis (Holechek & Gross
1982) and feeding-sign survey respectively (Koirala et al. 2016). We also used
RMT analysis to compare the balance of CP, NP, and NDF (Koirala 2018) in the
diet of elephants in our study area with existing data on the available diets
of wild elephants in India (Das et al. 2014).
Independent sample t-
test was performed to see the seasonal difference in the nutrient dry matter/
balance in the plants. Pearson correlation was performed to see the
relationship between utilisation and availability of
protein and NDF in the diet. All tests were done using Excel and IBM SPSS
statistical package version 22.
Results
The nutrient contents
of the leaves of plants consumed by elephants didn’t vary with species and
season (Table 1). The highest estimates for CP (Lagerstroemia parviflora; 25.97%), NSC (Litsea
monopetala; 31.85%), and NDF (Saccharum
bengalensis; 88.62%) were found in the wet
season. The average percent dry matter CP content of food plants was 12% in the
wet season and 11 % in the dry season (t37 = 0.372, p = 0.712). The
average NDF content was 55.9% (wet season) and 66% (dry season) (t37
= -1.556, p = 0.128), and average EE content was 1.7 % and 1.2% (t37
= 1.427, p = 0.162) in wet and dry seasons, respectively.
The proportion of P:
NP: NDF in plants was variable between seasons (Figure 1). For example, the
protein balance of most frequently consumed plants Spatholobus
parviflorus and Mallotus
philippensis was higher during the wet season. In
both seasons, however, most of the dominant plant species consumed were
similar, for example, Spatholobus parviflorus, Mallotus
philippensis (Koirala et al. 2016). In the case of agricultural crops, in the wet
season paddy was 12.34 % P: 18.31% NP: 69.35% NDF, and in the dry season 9.55%
P: 15.42% NP: 75.03% NDF (Figure 1).
The estimated
seasonal diets of elephants was (Figure 2): 16 % CP: 26.7 % NP: 57.3% NDF in wet season; and, 10.4% CP: 13.7%
NP: 75.7 NDF in dry season.
Discussion
The utilisation pattern of food plants showed that browse forms
the major diet of elephants in the dry season in both PWR and CNP. While the
wet season diet was slightly dominated by grass in PWR and browse in CNP
(Koirala et al. 2016). The nutritional content (Table 1) of plant species was
stable between seasons.
The combined dry
season diet was greater in NDF than the wet season diet. The combined wet
season diet was greater in protein and non-protein than the dry season diet.
However, both summer and winter diets were somewhat similar in nutrient
balance. NDF balance was the highest difference of 12% (±2.09 SE) while
non-protein showed a difference of 11.6% (±2.04 SE) and protein at the least
difference of 6% (±1.05 SE).
During the wet season,
the protein content of food plants like Acacia catechu, Litsea
monopetala, and Lagerstroemia parviflora was high to compensate for the deficiency of
protein from Saccharum bengalensis,
Saccharum spontaneum,
and Phragmites karka, suggesting that these
foods were complementary to each other (Figure 1A).
Similarly, in dry
season, the protein balance of diet of highly utilised
browse and agricultural crops like paddy and wheat were similar. Although there
was less protein in Spatholobus parviflorus, a highly preferred plant in the dry
season, so elephants may be using plants species like Phragmatus
karka, Acacia catechu, Litsea
monopetala, and Ficus
semicordata to slightly increase protein content
to balance the deficit of protein from Spatholobus
parviflorus, Cymbopogon
sp., Saccharum spontaneum,
and Saccharum bengalensis
(Figure 1B).
Moreover, there was
no significant relationship between utilisation and
availability of protein (r=-0.146, p=0.418 and NDF (r = -0.188, r = 0.293) in
the weighed diet. The preference of plants is different irrespective of their
presence and frequencies in the diet. The utilisation
of these plants varies with season and localities (Koirala et al. 2016).
Subsequently, the combined macronutrient balance of dry and wet season food
plants was almost similar. The balance of different macronutrients showed no
significant seasonal difference (t30 = 1.030, p = 0.311) protein;
(t=30 0.760, p = 0.453) and non-protein t30=-2.039, p=
0.050 NDF. This gives an indication that although elephants utilised
many types of food plants with different nutritional content, the animals
compose their diet to achieve a preferred macronutrient intake target (Raubenheimer 2011; Coogan 2014).
At the time of this
study in both of these study periods, crops act as a complementary food source
to replace low protein grasses. The lower protein in grasses like Cymbopogon sp., Saccharum
spontaneum, S. bengalensis,
and Digitaria spp. in in the dry season
and higher accessibility and protein content in crops may lead to crop raiding.
This is consistent with the assertion that the nutritional composition of crops
could be related to the crop raiding behaviour of
elephants (Sukumar & Gadgil 1988; Sukumar 1989,
1991, 2006).
Our previous study
has found that there was a negative relationship between utilisation
and availability. As such there could be a reasonable selection of foods. The
present study attempted to validate our hypothesis that the elephants are
selectively feeding with a null hypothesis of feeding proportional to
availability through the pattern of use seen in some of the highly preferred
food plants like Mallotus philippensis, Bambusa
sp., Bombax ceiba, Spatholobus perviflorus, and Thysanolaena
maxima. The difference shown in the availability and utilisation
in dry and wet season diet showed that there is selective mode of feeding. The
availability of plant foods and their utilisation
determines the preference. The preference based on availability and usage may
be primary information in relation to conservation of probable food plants in
the habitat. However for the long term population
sustainability of elephants, utilisation information
based on nutritional content of plants is vital for the conservation and
management of habitat for elephants. Further, the geometric analysis of food
plants has revealed that besides the relationship between utilisation
and macro nutrient content, the balance of nutrients of different diets plays a
vital role in food selection. The ratio focused selection was located by this
study as the diagonal clustering of expected dry and wet seasonal diet points,
together with similar seasonal diet points of Indian wild elephants. The
significant relationship of utilisation and
macronutrient balance of highly preferred browse, grasses, and crops at least
in these periods of the year have revealed that crop raiding can be seen as
part of protein makeup of elephants due to lower protein in grasses and some
browse. In nutrient space, crops have been found to be occupying a place in between
browse and grass. Thus, the elephants move away from their natural habitat to
seek an alternative source of fodder with a high nutritive value such as crops.
Table 1.
Nutritional composition (percent dry matter) of major plants consumed by Asian
elephants, including crude protein (CP), ether extract (EE), ash, neutral
detergent fibre (NDF), acid detergent lignin (ADL),
and non-structural carbohydrates (NSC).
|
Plant species |
CP |
(EE) |
Ash |
NDF |
ADF |
ADL |
NSC |
|
Wet season |
|
|
|
|
|
|
|
|
Lagerstroemia parviflora |
25.97 |
1.20 |
5.82 |
62.32 |
52.14 |
24.32 |
4.69 |
|
Ficus religiosa |
13.99 |
1.40 |
16.90 |
43.86 |
35.79 |
12.98 |
23.85 |
|
Thysanolaena maxima |
10.20 |
0.87 |
8.67 |
76.35 |
57.30 |
12.90 |
3.91 |
|
Musa sp. |
15.89 |
6.25 |
12.62 |
63.65 |
59.89 |
11.58 |
1.59 |
|
Saccharum bengalensis |
2.07 |
0.80 |
5.73 |
88.62 |
62.22 |
32.58 |
2.77 |
|
Saccharum spontaneum |
5.76 |
0.80 |
11.00 |
57.67 |
49.15 |
39.30 |
24.76 |
|
Sterculia villosa |
12.80 |
1.00 |
6.40 |
49.60 |
46.50 |
19.50 |
31.20 |
|
Bomax ceiba |
14.04 |
0.86 |
11.10 |
56.57 |
41.36 |
19.09 |
18.29 |
|
Acacia catechu |
24.15 |
1.30 |
6.35 |
65.94 |
43.65 |
12.40 |
2.26 |
|
Digitaria ciliaris |
10.80 |
0.86 |
14.04 |
61.55 |
43.13 |
9.07 |
12.75 |
|
Paspalum scrobiculatum L |
5.00 |
3.00 |
7.18 |
7.77 |
2.50 |
2.05 |
4.71 |
|
Murrya coenigii |
13.70 |
0.90 |
6.60 |
54.32 |
41.22 |
14.25 |
24.48 |
|
Bridelia retusa |
13.75 |
1.20 |
8.36 |
46.95 |
41.04 |
16.74 |
29.74 |
|
Mallotus philippensis |
14.35 |
2.30 |
11.25 |
63.54 |
53.98 |
25.62 |
8.56 |
|
Spatholobus parviflorus |
14.69 |
2.85 |
11.70 |
41.99 |
35.02 |
11.18 |
28.77 |
|
Phragmites karka |
6.60 |
0.60 |
10.36 |
80.99 |
64.97 |
40.88 |
1.45 |
|
Saccharum spontaneum |
6.10 |
0.65 |
6.32 |
82.45 |
66.02 |
13.20 |
4.48 |
|
Bambusa sp. |
12.50 |
2.00 |
13.80 |
70.91 |
51.85 |
17.52 |
0.79 |
|
Litsea manopetala |
17.44 |
3.22 |
10.22 |
37.27 |
28.22 |
13.12 |
31.85 |
|
Saccharum bengalensis |
3.56 |
1.87 |
7.31 |
60.84 |
1.31 |
6.62 |
27.42 |
|
Desmostachya bipinnata |
12.17 |
1.78 |
9.59 |
55.95 |
43.86 |
17.75 |
14.42 |
|
Paddy |
11.25 |
0.60 |
8.20 |
63.25 |
52.35 |
24.30 |
16.70 |
|
Maize |
9.69 |
0.90 |
10.00 |
54.00 |
42.00 |
34.00 |
25.41 |
|
Dry season |
|
|
|
|
|
|
|
|
Spatholobus parviflorus (bark) |
6.50 |
0.34 |
15.03 |
54.73 |
48.19 |
21.43 |
23.40 |
|
Saccharum spontaneum |
7.56 |
1.25 |
9.92 |
77.97 |
54.13 |
11.95 |
3.30 |
|
Saccharum bengalensis |
7.94 |
1.0 |
8.88 |
77.46 |
50.47 |
7.1 |
4.72 |
|
Acacia catechu |
18.50 |
1.40 |
5.30 |
66.65 |
59.89 |
11.58 |
8.15 |
|
Cymbopogon sp. |
3.55 |
0.50 |
8.36 |
82.45 |
81.48 |
12.92 |
5.14 |
|
Spatholobus parviflorus |
8.70 |
0.34 |
12.03 |
64.73 |
47.11 |
21.46 |
14.20 |
|
Mallotus philippensis |
12.35 |
3.78 |
10.40 |
62.50 |
51.78 |
22.72 |
10.97 |
|
Ficus semicordata |
15.56 |
0.73 |
10.99 |
51.35 |
47.16 |
19.90 |
21.37 |
|
Ficus racemosa |
12.61 |
1.20 |
13.53 |
65.54 |
49.97 |
29.08 |
7.12 |
|
Phoenix humilis |
6.00 |
1.50 |
0.96 |
64.23 |
53.12 |
19.20 |
27.31 |
|
Phragmites karka |
20.56 |
1.31 |
6.98 |
70.68 |
34.79 |
7.48 |
0.47 |
|
Litsea monopetala |
20 |
2.56 |
6.56 |
63.10 |
49.34 |
27.85 |
8.82 |
|
Paddy |
8.53 |
0.7 |
10 |
67 |
* |
* |
13.77 |
|
Maize |
5.76 |
0.80 |
11.00 |
57.67 |
49.15 |
39.30 |
24.76 |
|
Wheat |
9.75 |
0.6 |
9.5 |
69 |
* |
* |
11.15 |
|
Unidentified |
10.66 |
1.26 |
9.39 |
65.73 |
51.89 |
17.81 |
12.95 |
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