Journal of Threatened Taxa |
www.threatenedtaxa.org | 26 February 2021 | 13(2): 17827–17831
ISSN 0974-7907 (Online) | ISSN 0974-7893
(Print)
https://doi.org/10.11609/jott.6202.13.2.17827-17831
#6202 | Received 21 May 2020 | Final received
22 November 2020 | Finally accepted 02 February 2021
Food habits of the Dusky-striped
Squirrel Funambulus sublineatus
(Mammalia: Rodentia: Sciuridae)
Palassery Suresh Aravind 1,
George Joe 2 , Ponnu Dhanesh 3 & Rajamani
Nandini 4
1–4 Indian Institute of Science
Education and Research Tirupati (IISER Tirupati), Andhra Pradesh 517507, India.
1 aravind.ps@students.iisertirupati.ac.in
(corresponding author), 2 joegeorge@students.iisertirupati.ac.in,
3 dhaneshp@students.iisertirupati.ac.in,
4 nandini@iisertirupati.ac.in
Editor: Giovanni Amori, CNR-Research Institute on Terrestrial Ecosystems,
Rome, Italy. Date
of publication: 26 February 2021 (online & print)
Citation:
Aravind, P.S., G. Joe, P. Dhanesh & R. Nandini (2021). Food habits
of the Dusky-striped Squirrel Funambulus sublineatus (Mammalia: Rodentia: Sciuridae).
Journal of Threatened Taxa 13(2): 17827–17831. https://doi.org/10.11609/jott.6202.13.2.17827-17831
Copyright: © Aravind et al. 2021. 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: DST-SERB ECR,
ECR/2016/002041.
Competing interests: The authors declare no competing interests.
Acknowledgements: The work was funded by a DST-SERB ECR grant to
RN. We are grateful to Tamil Nadu Forest
Department for permissions. We thank the
Kodaikanal International School and IISER Tirupati
for support. We appreciate Ravi Kiran Arigela for helping with plant identification, and V.V.
Robin and his field team for shared field logistics. We thank Sanjay Prasad, Harsha Kumar, Viral
Joshi, Swati Udayaraj, Senan
D’ Souza, Nivetha Murugesan, Jobin Varughese, Ritobroto Chanda, Harikrishnan
C.P., and Suyesh Sawant for sharing sighting details
and photographs, and all the Sciurid Lab members for their comments on the
manuscript.
Abstract: We report the first observations
of feeding behaviour of the Dusky-striped Squirrel Funambulus
sublineatus in the Western Ghats. It was observed feeding on eight plant
species, including four non-native species.
Feeding was observed in forests as well as in plantations and
agricultural habitats, indicating the urgent need for studies in such
human-modified landscapes.
Keywords: Feeding behaviour, modified
landscape, Palani Hills, small mammal, Western Ghats.
The Dusky-striped Squirrel (Funambulus
sublineatus Waterhouse, 1838) is a poorly studied
small mammal, due to quick and cryptic behaviour that makes field observations
challenging (Datta & Nandini 2014). This species of palm squirrel is endemic to
the Western Ghats of southwestern India and Sri Lanka, and is listed as
Vulnerable by the IUCN owing to a declining population trend (Rajamani et al. 2008).
Dissanayake & Oshida (2012) propose that
the Indian and Sri Lankan populations are split as distinct species, but for
this note we follow the IUCN taxonomy, which is not updated. In India, it has been recorded mostly in
tropical evergreen and moist deciduous forests of Karnataka, Kerala, and Tamil
Nadu (Menon 2014). No targeted studies
exist on the ecology and behaviour of this species, with only a couple of
opportunistic published records on feeding habitats. Vivek et al. (2011)
noted that this squirrel was often part of mixed-species bird flocks, gleaning
on bark and flushing insects that were consumed by insectivorous birds. Ganesh & Devy
(2006) record infrequent predation on flowers of Cullenia
exarillata.
An opportunistic record describes feeding on wild raspberry fruits Rubus fairholmianus
(Datta & Nandini 2014).
The current note presents the first record of feeding
habits of the Dusky-striped Squirrel in the Western Ghats. These observations are part of an ongoing
study on squirrels in the Upper Palani Hills (above 1,400m contour), which is
the easternmost spur of the Western Ghats biodiversity hotspot (Myers et al.
2000). The study area occurs in the Dindigul District in Tamil Nadu, between 10.000–10.333N
& 77.266–77.400E. The terrain of the
Upper Palanis is mountainous, comprising grasslands
interspersed with forest patches, categorized as southern montane wet temperate
forests or “shola forests” by Champion & Seth (1968). Shola forests are predominantly made up of
stunted, branched, and dense crown trees which have rainforest origins (Davidar et al. 2007).
The dominant tree species are Syzygium
densiflorum, Magnolia nilagirica,
Gordonia obtusa,
and Eurya japonica (Matthew 1962).
Shola-grassland habitats harbour high biodiversity (Robin & Nandini 2012),
but they have undergone significant habitat loss due to timber plantations,
agriculture, and other developmental activities (Arasumani
et al. 2018) (Figure 1). Prominent
exotic species include Acacias, conifers, and Eucalyptus sp. (Matthew
1962).
Opportunistic records of feeding behaviour of
Dusky-striped Squirrels were noted during a systematic landscape-level
study on occurrence of sympatric squirrel species on the plateau between
January 2019 and July 2019. Squirrels
were located both by their calls and movements.
When a Dusky-striped Squirrel was seen feeding, we recorded details of
behaviours until the animal moved out of sight.
The part of the plant consumed and the plant species were
identified. We characterised each
feeding instance as a bout of activity of one or more animals feeding on the
same food source. Bouts ended when the
animal moved out of sight. While no data
on the amount of food consumed were recorded, this method provides the
diversity of food consumed (Paschoal
& Galetti 1995). Unique behaviours were recorded with a video
camera, when possible.
Dusky-striped Squirrels were encountered on 66
occasions at 30 distinct locations. Most
sightings were of single animals, though on 12 occasions two animals were
sighted together, three animals on two occasions and four were sighted together
three times (1.38 ± 0.76 SD). The age and sex of animals could not be
determined. Twenty-one foraging bouts
were recorded over the study period (Table 1).
Squirrels were seen foraging on eight plant species from seven different
plant families (Table 1). Almost 40% of
the foraging observations were of Dusky-striped Squirrel feeding on the nectar
of Lobelia leschenaultiana, a native
understory shrub common along habitat ecotones (Image 1a). Over a five–day period in February 2019, two
to four individuals were observed feeding on nectar, and not on any other
flower parts. We confirmed that they
were feeding on nectar by examining video recordings of the bouts (Video 1; using Canon EOS 700D; number of recordings= 6, mean
length of recording= 57.17 ± 22.66 SD seconds).
The squirrels were seen on this plant only when flowering (February), and
not at any other time of the year.
On four occasions, squirrels were observed foraging on
the nectar of Erythrina variegata, a
non-native tree planted along roads and boundary walls (Image 1b). Fruits of Memecylon
randerianum (Image 1c), Lantana camara, and Rubus ellipticus, were consumed on two occasions each. The only time we observed seeds being
consumed during this study was of Acacia mearnsii
(Image 1d). The squirrel was seen
peeling the pod with its mouth and consuming the seeds (Video 2; using Nikon COOLPIX P900; number of recordings = 1,
length of recording= 40 seconds).
Dusky-striped Squirrels were observed on single occasions consuming bark
of Elaeocarpus tuberculatus
and Symplocus foliosa. We observed squirrels sniffing tree bark on
eight occasions, but could not confirm if they were foraging on insects or
bark. Though exact heights used by
squirrels were not noted, all squirrels were seen foraging in the understory
(0–8 m) and mid-canopy (8–15 m) strata only.
Overall, we observed Dusky-striped Squirrels feeding
on fruit, nectar, and bark of native evergreen forest species as well as on
introduced and invasive plant species, in a variety of habitats. Squirrels were observed to feed on nectar
more than any other plant part (χ2= 14.238, df=
3, p-value= 0.003), but on non-native and native plant species equally (χ2=
0.428, df= 1, p-value= 0.513). In this note, present observations that the
Dusky-striped Squirrel feeds on nectar, a behaviour similar to nectar-robbery
seen in Swinhoe’s Striped Squirrels (Deng et al.
2004, 2015). Other squirrel species in
the Western Ghats are known to feed largely on leaves and fruit, while also
feeding on other plant parts. The Indian
Giant Squirrel is known as a facultative frugivore that feeds on seeds, leaves,
flowers, pith, and bark (Borges 1992; Sushma & Singh 2006), while the
Indian Giant Flying Squirrel is reported to feed on fruit, leaves, flower, and
bark (Nandini & Parthasarathy 2008).
We report observations of feeding in shola forests (n=
6), but also in timber plantations (n= 9) and agriculture fields (n= 6) (Table
1). Our study reinforces findings from
other studies, which have recorded the presence of the species outside
forests. In the Western Ghats, the
Dusky-striped Squirrel has been observed in coffee plantations (Bali et al.
2007; Sidhu et al. 2015), tea plantations (Sidhu et al. 2015) and in evergreen
forests at the edge of tea plantations (Anamalais –
Nandini Rajamani pers. obs. 2005,2006 &
2007). Sridhar et al. (2008) found the
species in rainforest fragments, but detections were higher in contiguous
protected rainforests.
While this note illustrates that the Dusky-striped
Squirrel does use food resources outside forests, we suggest that this may not
reflect the true use of modified habitats in the Upper Palanis
landscape. The probability of detection
of the species is likely higher in open habitats compared to the dense forest
interior. We would like to state,
however, that the observations of Dusky-striped Squirrel feeding on non-native
plant species is a significant finding.
This implies that the species shows a certain degree of flexibility
regarding using resources in modified landscapes, as seen in several other
small mammal species (Kellner et al. 2019). Future research efforts
should specifically target ecotonal regions, including forest borders, to
understand the distribution, population status, habitat requirements, and
ecology of this cryptic lesser-known species.
Table 1. Details of feeding behaviour of the
Dusky-striped Squirrels in the Upper Palanis.
Plant species |
Habitat |
Parts eaten |
Month eaten |
Number of feeding bouts |
Number of squirrels in each feeding bout |
Lobelia leschenaultiana (Campanulaceae) |
Timber plantation edge |
Nectar |
February |
8 |
4,2,2,2,1,1,2,2 |
Erythrina variegata (Fabaceae) |
Agriculture |
Nectar |
January, March |
4 |
1,4,1,1 |
Memecylon randerianum (Melastomataceae) |
Shola forest |
Fruit |
June |
2 |
2,1 |
Lantana camara (Verbenaceae) |
Agriculture |
Fruit |
July |
2 |
1,2 |
Rubus ellipticus (Rosaceae) |
Shola forest edge |
Fruit |
May |
2 |
1,1 |
Acacia mearnsii (Fabaceae) |
Timber plantation |
Seed |
February |
1 |
1 |
Elaeocarpus tuberculatus (Elaeocarpaceae) |
Shola forest |
Bark |
June |
1 |
1 |
Symplocus foliosa (Symplocaceae) |
Shola forest |
Bark |
December |
1 |
1 |
For
figure, images & videos - - click here
References
Arasumani, M., D. Khan, A. Das, I. Lockwood, R. Stewart, R.A.
Kiran, M. Muthukumar, M. Bunyan & V.V. Robin
(2018). Not seeing the grass for the
trees: timber plantations and agriculture shrink tropical montane grassland by
two-thirds over four decades in the Palani Hills, a Western Ghats sky island. PLoS ONE 13(1): e0190003. https://doi.org/10.1371/journal.pone.0190003
Bali, A., A. Kumar & J.
Krishnaswamy (2007). The
mammalian communities in coffee plantations around a protected area in the
Western Ghats, India. Biological Conservation 139(1–2): 93–102. https://doi.org/10.1016/j.biocon.2007.06.017
Borges, R.M. (1992). A nutritional analysis of foraging in the Malabar
Giant Squirrel (Ratufa indica).
Biological Journal of the Linnean Society 47(1):
1–21.
Champion, H.G. & S.K. Seth
(1968). A revised survey of the forest
types of India. Government of India Press, New
Delhi, 404pp.
Datta, A. & R. Nandini (2014). Sciurids, pp. 534–535. In: Johnsingh A.J.T. & N. Manjrekar (eds.). Mammals of
South Asia, Volume 2. University Press, Hyderabad, India.
Davidar, P., D.M. Dass & S.L.
Vijayan (2007). Floristic inventory of woody
plants in a tropical montane (shola) forest in the Palni
hills of the Western Ghats, India. Tropical Ecology 48(1): 15–26.
Deng, X. B., P.Y. Ren, J.Y. Gao
& Q.J. Li (2004). The Striped Squirrel (Tamiops
swinhoei hainanus) as a
nectar robber of ginger (Alpinia kwangsiensisy). Biotropica
36(4): 633–636. https://doi.org/10.1111/j.1744-7429.2004.tb00357.x
Deng, X., D. Mohandass,
M. Katabuchi, A.C. Hughes & D.W. Roubik (2015).
Impact of striped squirrel nectar-robbing behaviour on gender fitness in Alpinia roxburghii
Sweet (Zingiberaceae). PloS
ONE 10(12): e0144585. https://doi.org/10.1371/journal.pone.0144585
Dissanayake, R. & T. Oshida (2012). The
systematics of the Dusky Striped Squirrel, Funambulus
sublineatus (Waterhouse, 1838) (Rodentia: Sciuridae) and its relationships to Layard’s Squirrel, Funambulus layardi Blyth,
1849. Journal of Natural History 46(1–2): 91–116. https://doi.org/10.1080/00222933.2011.626126
Ganesh, T. & M.S. Devy (2006). Interactions
between non-flying mammals and flowers of Cullenia
exarillata Robyns (Bombacaceae), a canopy tree from the wet forests of Western
Ghats, India. Current Science 90(12): 1674–1679.
Kellner, K.F., J.E. Duchamp &
R.K. Swihart (2019). Niche breadth and vertebrate sensitivity to habitat
modification: signals from multiple taxa across replicated landscapes. Biodiversity
and Conservation 28(10): 2647–2667. https://doi.org/10.1007/s10531-019-01785-w
Matthew, K.M. (1962). The flora of Kodaikanal. Nelumbo 4(1–4): 95–104. https://doi.org/10.20324/nelumbo%2Fv4%2F1962%2F76481
Menon, V. (2014). Indian Mammals: A Field Guide. Hachette India,
India, 386pp.
Myers, N., R. A. Mittermeier, C.G.
Mittermeier, G.A. Da Fonseca & J. Kent (2000). Biodiversity hotspots for conservation priorities. Nature
403(6772): 853–858.
Nandini, R. & N. Parthasarathy (2008). Food habits of the Indian Giant Flying Squirrel (Petaurista philippensis)
in a rain forest fragment, Western Ghats. Journal of Mammalogy 89(6):
1550–1556. https://doi.org/10.1644/08-MAMM-A-063.1
Paschoal, M. & M. Galetti
(1995). Seasonal food use by the
neotropical squirrel Sciurus ingrami in southeastern
Brazil. Biotropica 27(2): 268–273. https://doi.org/10.2307/2389006
Rajamani, N., S. Molur & P.O. Nameer (2008). Funambulus sublineatus. The IUCN Red List of Threatened
Species.e.T8703A12926423. Downloaded on
15 May 2020. https://doi.org/10.2305%2FIUCN.UK.2008.RLTS.T8703A12926423.en
Robin, V.V. & R. Nandini
(2012). Shola habitats on sky islands:
status of research on montane forests and grasslands in southern India. Current
Science 103(12): 1427–1437.
Sidhu, S., T.R.S. Raman & D. Mudappa (2015). Prey abundance and leopard diet in a plantation and
rainforest landscape, Anamalai Hills, Western Ghats. Current
Science 109(2): 323–330. https://www.currentscience.ac.in/Volumes/109/02/0323.pdf
Sridhar, H., T.R.S. Raman & D.
Mudappa (2008). Mammal persistence and abundance in tropical
rainforest remnants in the southern Western Ghats, India. Current Science 94(6):
748–757.
Sushma, H.S. & M. Singh (2006).
Resource partitioning and
interspecific interactions among sympatric rain forest arboreal mammals of the
Western Ghats, India. Behavioral Ecology
17(3): 479–490. https://doi.org/10.1093/beheco/arj058
Vivek, R., P.R. Agarwal & R. Sreekar
(2011). Dusky Striped Squirrel Funambulus sublineatus
as a part of mixed–species bird flocks. Indian BIRDS 7(2): 51.