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Vocalization Repertoire of the Five Striped Palm Squirrel, Funambulus

pennantii pennantii: An Ethological Study

Deepali Agarwal

1

and Reshma Bhatnagar

2

Department of Zoology Dayalbagh Educational Institute

(Deemed to be University) Agra

DOI:

https://doi.org/10.51583/IJLTEMAS.2026.150100082

Received: 30 January 2026; Accepted: 04 February 2026; Published: 10 February 2026

ABSTRACT

The five striped palm squirrel, Funambulus pennantii pennantii is native to Northern India, Iran, Pakistan and

Bangladesh. The vocal communication of F. p. pennantii was studied at four different sites at Agra district of

Uttar Pradesh, India. These sites were selected on the basis of maximum cluster locations and movements of

squirrels tracked by the GPS tracking device GARMIN eTrex 10. The locations data was uploaded on QGIS

open access software to map the sites. To record the vocalizations of squirrels, the AE mini digital recording

device was used. Since this species enjoys the Least Concern (LC) status, Godden’s formula for infinite

population was employed to determine the sample size, which was approximately 400 squirrels. To generate the

audio spectrograms of squirrel vocalizations, MATLAB software version R2019b was used. Photography and

videography were done through ad libitum sampling technique with NIKON COOLPIX 500 camera. Four

distinct patterns emerged in the audio spectrograms, and they were identified as four distinct call types. The

Buzz is a mating and play call. It is also used by mothers to communicate with their juveniles. The Growl is a

threat call and is followed by chase or attack. The Bark is an alarm call which is of two types- a predator class

specific alarm call for aerial predators and another predator class specific alarm call for terrestrial predators. The

Rattle is a territorial declaration by squirrels as their routine at a specific time of a day. This is the first report of

acoustic identification and analysis of calls of F. p. pennantii in their behavioral contexts.

Key words: Funambulus, Vocalization, MATLAB, Acoustic, Ethology.

INTRODUCTION

Communication is the way by which animals of same or different species interact with each other. The animals

communicate with each other for many reasons like foraging, mating, playing, intraspecific and interspecific

interactions, mother-child interactions, territoriality and vigilance (Rogers and Kaplan, 2002). Visual displays,

olfactory markers, scent deposits, urine marking, tactile signals and sound signals are the means through which

the animals communicate (Rogers and Kaplan, 2002). Vocalizations or sound signals are produced by an

animal to communicate with conspecifics or members of other species. Vocalizations of animals and responses

they give in different situations provide insights into their behavior.

Vocalizations may be used by territorial animals that don't often engage physically as long- distance signals to

aid in discrimination (Wilson et al., 2015). In rodents, acoustic communication signals serve a wide range of

purposes, such as eliciting conspecifics to approach, warning adjacent animals of the presence of a predator, and

drawing mothers' attention to their juveniles (Okanoya and Screven, 2018). The five striped palm squirrel,

Funambulus pennantii pennantii native to Northern India, Iran, Pakistan, Bangladesh and is considered as an

exotic species in Australia, Oman and UAE (Rajaratnam and Redman, 2001; Judas and Hellyer, 2016;

Victor and Soto, 2020). According to the IUCN Red list, it is listed under Least Concern category (LC). It is

diurnal (Khan and Khan, 1980; Malhi and Kaur, 1995; Rajaratnam and Redman, 1997; Rajaratnam and

Redman, 1998; Sharma, 2016) and is successfully thriving in varied habitats such as residential areas, gardens,

crop lands (Agarwal and Bhatnagar, 2019). They are semi-arboreal in nature and spend most of the time on

trees. They descend on grounds for foraging, playing and mating (Ghose et al., 2004; Csurhes, 2016). They

communicate through the different sounds they produce. Acoustic behavior of four species of ground squirrels

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was studied by Koeppl et al., (1978). Greene and

Meagher (1998) analysed the predator class specific alarm calls in red squirrels in Montana. Vocalization

function of tree squirrels of Columbia was studied by Smith (1978). Vocalizations of the Belding’s ground

squirrel, Spermophilus beldingi, were studied by Leger et al., (1984) in California. There are many studies on

the acoustic behavior of various squirrels, but no such work has been reported for F. p. pennantii. Thus, the

present work is an attempt to study the vocalizations of F. p. pennantii and analyse the situations in which they

are used.

METHODS

Sampling area

The study was conducted in the Agra District (27.1767°N, 78.0081°E) of Uttar Pradesh, India. Firozabad district

lies on its East and Bharatpur on its West. To the North, the boundary touches the Mathura District. It is

surrounded by Dholpur district towards South (agra.nic.in, Government of Uttar Pradesh). Agra has semi-

arid type of climate (Deshwal et al., 2017) which is enriched with varied habitats. Temperature of Agra city

shows broad variation range in day and night. Summers occupied maximum part of the year. January is the

coldest month of the year with average maximum temperature of 14℃. It gradually increases and reaches

average maximum temperature about 45℃ during summers. The average annual rainfall of Agra is 523mm and

humidity remains high during the monsoon season.

Sampling sites

Four different sites were selected on the basis of availability of the squirrels- Balkeshwar, Sikandra, Dayalbagh

and Shahjahan Gardens. To track the movements and maximum availability of clusters of squirrels, GPS tracking

device GARMIN eTrex 10 was used. Then the data was uploaded to QGIS open access software and the positions

of squirrels were imposed (Figure 1). The timings of field visits were usually 6-8 am in the morning and 6-7pm

in the evening as squirrels are most active during these hours. However, time varies also according to the

changing weather conditions in Agra. The study was conducted in 2018 and 2019 throughout the year.

Sampling tools

To record the vocalizations of squirrels, AE mini digital recording device with mp3 audio format, microSD,

USD 2.0 and secure digital card was used. To map the locations of squirrels, GARMIN eTrex10 and QGIS

software was used. To prepare the audio spectrograms of the squirrel vocalizations, MATLAB version R2019b

was used. Photography and videography

were done through ad libitum sampling technique (Altman, 1974) with NIKON COOLPIX 500 camera.

Sampling method

Observations were made at the selected sites of Agra. Sites were visited regularly. We visited a site only once a

week so that the squirrels did not get habituated with the presence of observers. To record the vocals and identify

the producer of vocals, we tracked solitary squirrels only. To avoid bias, we preferred only natural encounters

of squirrels with conspecifics or predators. If under any circumstances, the squirrel got disturbed by the presence

of observers or other factors, the recording was discarded. Audios with maximum clarity of squirrel vocalizations

were analyzed and rest of the audios were discarded. The selected recordings were run repeatedly and then

uploaded to MATLAB software to generate audio spectrograms.

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Figure 1: Location of clusters of squirrels at selected sites of Agra

Sample Size

There was no information on population trends at different sites. Thus, sample size was determined by applying

Godden’s formula for infinite population size (Godden, 2004).

SS = Z

2

x P x (1-P)

C

2

Where, SS = Sample size

Z = Z value (1.96 at 5% confidence level) P = Percentage of population

C = confidence interval

Sample size obtained was approximately 400

RESULTS & DISCUSSION

This is the first report on vocalization patterns of F. p. pennantii. At all the four sites, the vocalization behavior

was same and no differences were recorded. Squirrels actively communicated with the conspecifics and with

individuals of other species viz House Crow (Corvus splendens), Human (Homo sapiens), Laughing Dove

(Spilopelia senegalensis) and Rose ringed Parakeet (Psittacula krameri). Usually, squirrels vocalized from the

top of trees or walls. According to Davis (1964), “Syllable” is defined as a pattern separated from other such

units in time. A "Preface syllable" is described as the first two or more syllables of a call that are significantly

distinct from the rest of the call. The term “Call” is used for different and distinct types of acoustic signals. The

vocalizations were identified as four distinct call types. Each pattern clearly translated into a distinct type of call.

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No intraspecific variations were observed. The frequency and duration, two basic characteristics of acoustic

signals were different for each type of call as clearly identifiable patterns in the audio spectrograms.

Buzz calls

The preface syllables of this sound, which has a low frequency and pitch, remained between 2 and 5 kilohertz.

This call is utilized by mother squirrels as a teaching tool to employ with their litter and juveniles. This sound is

also produced by F. p. pennantii to interact with

conspecifics for mating chase and play. It is a long, looping sound that is frequently heard in quiet settings, like

in the early morning (Graph 1; Plate I).

Our findings are supported by similar findings in the North American red squirrels. The mothers of this species

use buzz calls to communicate with their young ones. It is a call related to juvenile play and considered under

non aggressive behavior (Lair, 1990). According to Smith (1978), low frequency of this call indicates that the

approaching squirrel is close by and that the caller is engaged in activities other than predator avoidance.

Growl calls

The preface syllables have frequencies that range from 2-4 kHz at their lowest and up to more than 9 kHz at

their highest (Graph 2; Plate II). It is a warning before a chase or assault on other species or conspecifics. When

squirrels get ready to attack or chase away members of their own species or members of other species, they elicit

this threat call. It is a short, sharp, and aggressive call that keeps repeating. After every syllable, there is a pause

of 5–6 seconds. The squirrels fluff up and flick their tails during growls in order to appear bigger, imposing and

frightening during assault or pursuit. This is because they typically pair their calls with visual signals. As a result,

vocalization behaviour is displayed in a clear space, making it simple for the receiver to identify the caller

visually.

Our findings are like those among ground squirrel species of the genus Spermophilus frequently (Koeppl et al.,

1978). Unreceptive estrous females of North American red squirrel (Tamia sciurus) produce growl calls when

any male tries to approach them (Smith, 1978; Lair, 1990).

Bark calls

It is a cry with very high frequency notes. 3 kHz is the lower frequency and 7 to 10 kHz are the higher frequency

notes. Each second, 2-3 syllables are created. The Bark is an alarm call and it is a predator class specific alarm

call produced by F. p. pennantii which is of two types:

a) Aerial danger bark: When squirrels see an aerial predator, they emit an aerial danger bark at a frequency of

7-8 kHz to alert conspecifics (Graph 3a; Plate IIIa).

b) Terrestrial danger bark: When a terrestrial predator or intruder is sighted, squirrels emit a loud, intense

bark in order to warn nearby conspecifics. The frequency ranges between 8 to 10 kHz (Graph 3b; Plate

IIIb).

There is a good chance that F. p. pennantii alarm calls indicate the level of risk or the urgency of the response.

Funambulus palmarum produces whistle alarm calls due to the presence of humans in their vicinity probably

due to fear (Koli et al., 2011). Our findings are supported by a report on red squirrels by Greene and Meagher

(1997) in which they identified acoustically different alarm calls in response to aerial danger and terrestrial

danger. Southern Amazon red squirrels, Sciurus spadiceus have also been reported to use alarm calls to alert

their conspecifics (Eason, 2010). Among the vocalization of all squirrel species, alarm calls are the most

frequently produced vocalizations (Diggins, 2021). According to Shelly and Blumstein (2004), there is a link

between alarm calling and diurnality as it becomes easy for the caller to detect the predator visually.

Similarly, Magpie robins (Copsychus saularis ceylonensis) produce mobbing calls in the presence of predators

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which also help other animal species to detect the location of the predator (Wanniarachchi and Wijesundara,

2016). Alarm calls communicate with predators also, after giving an alarm call by marmots, foxes are less likely

to approach (Lenti Boero, 1992). In our study, no predator specific calls were identified. Contradictory to our

findings, Prairie dogs (Cynomys gunnisoni) produce distinct alarm calls to convey descriptive information about

the size, color and body shape of every individual predator as well as every human they detect (Loughry et al.,

2019).

Rattle calls

In this type of sound, 4-5 syllables are produced every second. Lower frequency is about 4- 5kHz and higher

frequency is 10-12kHz. Even in the absence of apparent intruders, F. p. pennantii can be heard making this

sound from the top of the wall or tree marked by the squirrel as its territory. This sound is typically made by

squirrels every day at a specific time for a long duration of about half an hour. It can continue even longer. It is

produced at a specific time of the day and it is a daily routine (Graph 4; Plate IV). This call's message

transmission features built-in redundancy, ensuring that it reaches a wider area. Acoustic signals that are repeated

typically have a higher chance of being heard. This call also included information on the caller's location,

therefore it qualifies as aggressive behaviour.

According to Koli and Bhatnagar (2014), Indian giant flying squirrel, Petaurista philippensis, emits the

territorial call around the nest tree before entering the nest. North American red squirrels also produce rattle calls

to advertise their territory (Gurnell, 1987). Red squirrels produce the call to advertise their boundary throughout

the day (Siracusa, 2017).

All our sampling locations are very complex urban or semi-urban environments with large branch networks, tree cavities,

tree trunks as well as grounds, fields, roadsides, gardens, buildings, homes and public areas with human footfall as well as

traffic. Therefore, a signal escape or defensive behavior tactic would not be suitable against all dangers and predators. The

squirrels would require various escape strategies. In this case, selection might work in favour of the development of

referential acoustic communication as stated by Macedonia and Evans, 1993.

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Plate IV: Rattle

GRAPH 1: SOUND ANALYSIS- BUZZ

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GRAPH 2: SOUND ANALYSIS- GROWL

GRAPH 3A: SOUND ANALYSIS- AERIAL DANGER BARK

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Graph 3b: Sound analysis- Terrestrial danger bark

Graph 4: Sound analysis- Rattle

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REFERENCES

1.

Agarwal, D., & Bhatnagar, R. (2019). Comprehensive review of the current status of ethological studies

on Funambulus pennantii (Wroughton, 1905), the five striped northern palm squirrel.

2. Altmann, J., 1974. Observational study of behaviour. Behaviour 49:227-267.

3. Csurhes, S. (2016). Invasive plant risk assessment. Bitou bush. Department of Agriculture and Fisheries

Biosecurity Qld.

4. Davis, L. I. (1964). Biological acoustics and the use of the sound spectrograph. Southwestern Nat., 9:118-

145.

5.

Deshwal, R., Tiwari, D., & Singh, R. (2017). Clinical and biochemical characteristics of exertional heat

stroke among paratroopers in Agra, India. J Assoc Physicians India, 65(2), 57-61.

6.

Diggins, C. A. (2021). Behaviors associated with vocal communication of squirrels. Ecosphere, 12(6),

e03572.

7. Eason, P. 2010. Alarm signaling in a facultatively social mammal, the southern Amazon red squirrel

Sciurus spadiceus. Mammalia 74:343–345.

8. Ghose, R. K., Mandal, A. K., & Ghosh, P. S. (2004). A contribution to the taxonomy of Indian five striped

squirrel (Funambulus pennanti, Wroughton), with description of two new subspecies. Records of the

Zoological Survey of India, 102(3-4), 89-103.

9. Godden, B. (2004). Sample size formula, Journal of statistics, 3(66), 1.

10. Greene, E., & Meagher, T. (1998). Red squirrels, Tamiasciurus hudsonicus, produce predator-class specific

alarm calls. Animal Behaviour, 55(3), 511-518.

11.

Gurnell, J. 1987. The natural history of squirrels. Facts on File Publications, New York, New York, USA.

12. Judas, J., & Hellyer, P. (2016). Five-striped Palm Squirrel, Funambulus pennantii (Wroughton, 1905)-a

new addition to the UAE's exotic fauna. Tribulus, 24, 126-130.

13. Khan, Z. & Khan, J. A. (1980). food preferences of" five-stripe" squirrel, Funambulus pennanti pennanti

Wroughton.

14. Koeppl, J. W., Hoffmann, R. S., & Nadler, C. F. (1978). Pattern analysis of acoustical behavior in four

species of ground squirrels. Journal of Mammalogy, 59(4), 677-696.

15. Koli, V. K., and C. Bhatnagar. 2014. Calling activity of Indian giant flying squirrel (Petaurista philippensis

Elliot, 1839) in the tropical deciduous forests, India. Wildlife Biology in Practice 10:102–110.

16. Koli, V. K., Bhatnagar, C., & Sharma, S. K. (2011). A Note on Whistle Alarm Calls of Three-striped Palm

Squirrel Funambulus palmarum linnaeus in Sitamata Wildlife Sanctuary, Rajasthan, India. Journal of the

Bombay Natural History Society (JBNHS), 108(1), 53-55.

17. Lair, H. 1990. The calls of the red squirrel: a contextual analysis of function. Behavior 115:254–282.

18. Leger, D. W., Berney-Key, S. D., & Sherman, P. W. (1984). Vocalizations of Belding's ground squirrels

(Spermophilus beldingi). Animal Behaviour, 32(3), 753-764.

19.

Lenti Boero, D. 1992. Alarm calling in Alpine marmot (Marmota marmot L.): evidence for semantic

communication. Ethology, Ecology, and Evolution 4:125–138.

20.

Loughry, W. J., M. Oeser, C. D. Anderson, and J. L. Hoogland. 2019. The importance of individual

variation in the alarm calls of Gunnison’s prairie dogs. Animal Behaviour 150:59–68.

21.

Macedonia, J. M. & Evans, C. S. 1993. Variation among mammalian alarm call systems and the problem

of meaning in animal signals. Ethology, 93, 177–197.

22. Malhi, C. S., & Kaur, K. (1995). Responses of Funambulus pennanti Wroughton (Rodentia, Sciuridae)

towards different food additives.

INTERNATIONAL JOURNAL OF LATEST TECHNOLOGY IN ENGINEERING,

MANAGEMENT & APPLIED SCIENCE (IJLTEMAS)

ISSN 2278-2540 | DOI: 10.51583/IJLTEMAS | Volume XV, Issue I, January 2026

www.ijltemas.in Page 938

23. Okanoya, K., and L. A. Screven. (2018). Rodent vocalizations: adaptations to physical, social, and sexual

factors. Pages 13–41 in M. L. Dent, R. R. Fay, and A. N. Popper, editors. Rodent bioacoustics. Springer,

Cham, Switzerland.

24. Rajaratnam, S. M., & Redman, J. R. (1997). Effects of daily melatonin administration on circadian activity

rhythms in the diurnal Indian palm squirrel (Funambulus pennanti). Journal of biological rhythms, 12(4),

339-347.

25. Rajaratnam, S. M., & Redman, J. R. (1998). Entrainment of activity rhythms to temperature cycles in

diurnal palm squirrels. Physiology & behavior, 63(2), 271-277.

26. Rajaratnam, S. M., & Redman, J. R. (2001). Circadian locomotor activity rhythms of the diurnal Indian

palm squirrel in constant light. Chronobiology international, 18(1), 47-60.

27. Rogers, L. J., Kaplan, G. T. (2002). Songs, Roars, and Rituals: Communication in Birds, Mammals, and

Other Animals. United States: Harvard University Press.

28. Sharma, R. (2016). Reproductive behavior of Funambulus pennantii A case study of Ajmer Rajasthan.

IOSR Journal of pharmacy and biological sciences, 11(4), 51-53.

29. Shelly, E. L., and D. T. Blumstein. 2004. The evolution of vocal alarm communication in rodents.

Behavioral Ecology 16:169–17.

30. Siracusa, E., M. Morandini, S. Boutin, M. M. Humphries, B. Dantzer, J. E. Lane, and A. G. McAdam.

2017. Red squirrel territorial vocalizations deter intrusions by conspecific rivals. Behavior 154:1259–

1273.

31.

Smith, C. C. (1978). Structure and function of the vocalizations of tree squirrels (Tamiasciurus). Journal

of Mammalogy, 59(4), 793-808.

32. Victor, R., & Cuellar Soto, E. (2020). A preliminary study on the status of invasive palm squirrels in Oman.

International Journal of Environmental Studies, 77(5), 727-738.

33.

Wanniarachchi, S., & Wijesundara, C. S. (2016). The repertoire and structure of vocalizations of the

Southern Magpie Robin (Copsychus saularis ceylonensis) in the Kandy region, Sri Lanka. Ceylon Journal

of Science, 45(3).

34. Wilson DR, Goble AR, Boutin S, Humphries MM, Coltman DW, Gorrell JC, Shonfield J, McAdam AG

(2015) Red squirrels use territorial vocalizations for kin discrimination. Animal Behaviour, 107: 79–85.

35.

www.agra.nic.in, Government of Uttar Pradesh.