Journal of Threatened Taxa |
www.threatenedtaxa.org | 26 September 2022 | 14(9): 21776–21785
ISSN 0974-7907 (Online) | ISSN 0974-7893 (Print)
https://doi.org/10.11609/jott.8074.14.9.21776-21785
#8074 | Received 29 June 2022 | Final received 02 August 2022
| Finally accepted 11 August 2022
Effects
of visitor disturbance on tetrapod vertebrates in the
Horton
Plains National Park, Sri Lanka
D.M.T.
Dhananjani 1 &
W.A.D. Mahaulpatha 2
1,2
Department of Zoology, Faculty of Applied Sciences,
University of Sri Jayewardenepura Gangodawila,
Nugegoda, 10250 Sri Lanka.
1 td123dasanayake@gmail.com, 2 mahaulpatha@sjp.ac.lk (corresponding
author)
Abstract:
Effect of visitor disturbances on tetrapod vertebrates
was studied from December 2017 to October 2018 in the Horton Plains National
Park (HPNP), which is one of the world’s best nature reserves and a popular
tourist destination of Sri Lanka. Roads and nature trails with cloud forest,
aquatic and grasslands habitats inside the HPNP were selected to compare the
effect of visitor disturbances. Three 100 meter fixed
length line transects were marked along the roads and the nature trails in each
habitat. Vehicle noise was measured using sound meter software. Visitor
activities that cause disturbance included road kills, photography, trampling
and animal feeding. Amphibian and reptile road kills were higher compared to
other tetrapod road kills during vacation periods. Behavioral
response of species to visitor disturbances included avoidance, habituation and
attraction. When the vehicle noise range was from 63±2.11 dB to 69±2.11 dB,
habituation behavior was displayed. When the vehicle
noise range increased to the range of 70±4.71 dB to 88±4.71 dB, avoidance behavior was displayed. Animals display a propensity to
habituation behavior compared to avoidance behavior when vehicle speed was less than 30 kmh/hr. The results of this study can be used to integrate
with the future visitor, park and wildlife management practices of the
park.
Keywords:
Behavioral response,
disturbance, habitat, HPNP, nature reserves, road kills, tourist destination.
Editor:
Mewa Singh, University of Mysore, Mysuru, India. Date of publication: 26 September
2022 (online & print)
Citation:
Dhananjani, D.M.T. & W.A.D. Mahaulpatha
(2022). Effects of visitor disturbance on tetrapod vertebrates
in the Horton Plains National Park, Sri Lanka. Journal of Threatened Taxa
14(9): 21776–21785. https://doi.org/10.11609/jott.8074.14.9.21776-21785
Copyright:
© Dhananjani & Mahaulpatha
2022. 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: D.M.T. Dhananjani is a
graduate student from University of Sri Jayewardenepura with BSc (special) in
Zoology and working as a graduate research assistant on wildlife
management and conservation engaged with the “Wildlife Circle”, Department of
Zoology, University of Sri Jayewardenepura.
Prof (Mrs.) W.A.D. Mahaulpatha, Head of the Department of Zoology,
University of Sri Jayewardenepura works as a researcher and a professor, Prof.
W.A.D. Mahaulpatha is well versed and highly
experience regarding of wildlife conservation and management covering
ornithology, herpetology and mammalogy with more than hundred publications. As
result of that she was got the Presidential award involuntarily in 2018.
Author contributions: DMTD—main
researcher on this research findings, field sampling, data collection, data
analysis and preparation of the paper were the main contribution. WADM—main
supervisor of this research and who gave me the guidance, support and
encouragement throughout my research with sharing her valuable experience and
knowledge.
Acknowledgements: I highly appreciate the support
received from the staff of Horton Plains National Park and “Department of
Wildlife Conservation” for granting permission (Permit No: WL/3/2/04/18) to
conduct this research. I would like to express my warm gratitude to the University
of Sri Jayewardenepura and Department of Zoology for the facilities granted to
conduct this research.
Introduction
Sri Lanka is an island nation in
the Indian ocean, and is considered a global hotspot for biological diversity
along with the Western Ghats of India (Myer et al. 2000). Protected areas of
the island spread over 1,710,000 ha. There are 22 national parks (NPs) in Sri
Lanka governed by the Department of Wildlife Conservation (Newsome 2013). NPs
are one of the protected areas to allow in park recreational activities with
limited opportunities that are provided for the public to observe and study
wildlife within these areas (Senevirathna et
al. 2013). Despite the economic gains obtained, a number of negative
impacts may arise due to heavy visitor arrivals to NPs which keeps increasing
day by day.
According to Knight & Cole
(1995) human disturbance is an anthropogenic activity that causes a change in
metabolism and/or behavior of an animal. It can
produce short-term or long-term effects on individuals, populations, and
communities. Many studies have been conducted worldwide related to impact of
human disturbance on animal populations (Bélanger
& Bédard 1989; Stockwell et al. 1991; Poster et al. 1992; Reijnen et al. 1995; Andersen et al. 1996; Gill et
al. 1996).
Behavioral response
Most reported disturbances occur
related to viewing of wildlife which results in behavioral
change as a response by the animal. Behavioral
changes may arise when animals are approached for viewing, touching, feeding,
and photographing (Valentine & Birtles 2004; Lemelin
& Wiersma 2007). Nineteen out of 27 studies have proven that birds are
negatively affected by wildlife observation and photography (Boyle & Samson
1985). However, it is not only birds, other wildlife also gets affected by such
activities in varying degrees. Disturbance occurred by photography is greater
than that of nature observations (Klein 1993; Tershy
1997).
Road-kills
The greatest non-natural source
of vertebrate death is road mortality which is increasing even within protected
areas (reserves and parks) (Bernardino & Dalrymple 1992; Kline & Swann
1998). The continuation and prevalence of natural habitats can be disrupted by
the presence of trails and roads. There is evidence that recreational trails
can change breeding bird communities in both grassland and forest ecosystems
(Miller et al. 1998). Width of the road, vehicular traffic and speed level can
affect the road kill rates. Mortality of wildlife due to vehicular traffic is
among the direct impacts when natural habitats are replaced with roads
(Laurance et al. 2009). Despite a number of studies that have
been conducted regarding the impact of roads on animals, only two studies have
been reported (Maduwage et al. 2003; Amarakoon et al. 2010) from Sri Lanka. Horton Plains
National Park (HPNP) was included in the study conducted by Karunarathna
et al. (2013) on the impact of road traffic mortality of reptiles.
Noise
Noise is one of the most
negatively affecting road disturbance types (Forman & Alexander 1998;
Forman et al. 2003; Coffin 2007). Many animals use acoustic communication to
communicate with each other via acoustic signals (e.g., amphibians, birds, and
mammals). Those acoustic signals get interfered in areas affected by traffic
noise (Collins 2004; Marler 2004). The disturbance of
anthropogenic noise on wildlife can be quantified (Brumm
& Slabbekoorn 2005; Morley et al. 2014). A number
of studies highlight the negative and adverse impacts of anthropogenic noise on
wildlife (Stone 2000; Barber et al. 2010; Verzijden
et al. 2010; Hanna et al. 2011).
At present, Sri Lanka’s NPs are
becoming prime tourist destinations for both international and domestic
tourists. Hence, HPNP was selected to conduct this research which demonstrated
the second highest visitor rate within the period concerned. Total number of
visitors at HPNP in 2019 was 329,792 (STDA 2019). A total of 109 species of
indigenous plants species can be observed in the park. The vertebrate fauna of
the park includes five out of 19 mammal species that are endemic, nine mammal
species are nationally threatened and five among them are globally threatened,
thirteen out of 64 bird species are endemic and three globally threatened
species, five out of six species of reptiles are endemic, 13 out of 14 species
of amphibians are endemic species; the point endemism within the park is highly
remarkable for both fauna and flora (De Alwis et al.
2007). The vegetation consists of cloud forest and wet patana
grasslands, with a narrow ecotone belt of shrubs and herbs between them (Gunatilleke & Gunatillke
1990). In HPNP, visitors are allowed to walk along the nature trails in the
unique scenic landscape. Road access of 5 km through the park area is also
available where visitor vehicles are allowed. Baker’s fall, Small World’s End,
and Greater World’s End are popular attractions of the park (Rathnayake 2015). Therefore, over a long period of time,
anthropogenic activities have been concentrated within HPNP through the process
of ecotourism activities. This research was focused on identifying and
quantifying the impact of roads and nature trails from visitors in HPNP. It
will also highlight the management and conservation steps that need to be taken
in order to conserve the country’s remaining wildlife within protected areas.
Study sites
Present study was conducted from
December 2017 to October 2018 covering three main habitats types in HPNP
(6.78–6.83 N & 80.76°–80.83 E) including cloud forest, grasslands, and
aquatic habitat. The selected three habitat types were identified, based on the
base line survey in HPNP (DWC 2007) (Image 1).
Method and materials
Disturbances were surveyed using
line transects in the three selected habitats along the roads and nature
trails. For each month, a total of 18 transects were monitored (Appendix 1)
with triplicates of survey attempt in the time periods: morning (0800–1100 h),
mid-day (1130–1430 h) and evening (1500–1800 h) in an expansion four
consecutive days. Each transect was 100 m in length and width of transect line
was 20 m, and three such transects were laid in each habitat on the road as well
as the nature trail.
Road-kills
On each sampling day, road-kills
were recorded while walking in transects. Throughout the survey, in both
vehicle road and nature trail, surface and verges (50 cm on either side of the
road and nature trails) were scanned. The specimens were identified using field
guides (Wijeratne 2008; De silva 2009; Somaweera
& Somaweera 2009; Harrison 2011). All specimens
were photographed and identifications were verified (Karunarathna
et al. 2013). These monthly data were converted for vacation (December,
April, and August) and non-vacation periods (February to November).
Visitor activities
Visitor activities were recorded
under photography, trampling and animal feeding in the roads and nature trails
((Valentine & Birtles 2004; Lemelin & Wiersma
2007).
Behavioral changes
Animal behavioral changes
were monitored under habituation, attraction, and avoidance (Knight & Cole
1995). These behavioral responses were recorded at
stopping the vehicles within the sight of animal, then not get out and stopping
the vehicle within sight of animal, and then getting out. Habituation is
defined as a declining of a response to a repeated stimulus. It does not
display either a positive or a negative reward. Attraction is defined as the
strengthening of an animal’s behavior. It displays
positive rewards. Avoidance is defined as moving away from humans. It displays
negative reward (Knight & Cole 1995).
Noise
Vehicle noise was measured using sound level meter
(UNI-T UT353) along transect lines in all habitat of vehicle road sites (Murphy
& King 2016). While measuring noise, animal behavioral
response was observed whether it was avoidance or habituation. The noise level
was recorded in decibels (dB).
Vehicle
speed
Vehicle speed was recorded, using radar gun (Montella et al. 2013) to observe avoidance and habituation behavioral responses of species. Speed level was recorded
in km/h.
Results
Amount
of tetrapod vertebrate road kills during vacation and non-vacation period in
the nature trails
Highest average number of road-kills was recorded in
vacation months than non-vacation months. Highest average number (2.67±0.46) of
road-kills belonged to reptiles. During the vacation time period, and amphibian
road-kills (1.00±0.40) were recorded. No road-kills were recorded for mammals
and birds within the trail site habitats (Figure 1A).
Amount
of tetrapod vertebrate road kills during vacation and non-vacation period in
the roads
Highest average number of road kills was recorded in
vacation months compared to non-vacation months for all tetrapods.
Birds (0.33±0.12) were the lowest road kills during vacation periods. Highest
road kills was recorded for retiles (4.33±0.88) during
vacation periods. A value of 2.00±0.14 was recorded of mammals and 2.67± 0.33
was recorded for amphibians during vacation period. No road kills were recorded
in non-vacation months for birds (Figure 1B).
Road-kill
specimens recorded in the nature trails and roads
Amphibians and reptiles
road-kills were generally higher on roads. Taruga
eques road-kills were higher in trail site than road site. Minervarya
greenii road-kills were only recorded in road
site. Highest percentage of road-kills recorded were Calotes
nigrilabris, Ceratophora
stoddartii, and Aspidura
trachyprocta road-kills were also recorded. Eumyias sordidus and Rattus montanus were two bird and mammal species that were
road-killed (Figure 1C).
Categories
of disturbance in the nature trails and roads
Photography (33.5±10.72%) followed by animal feeding
(32.78±13.25%) were the most prominent disturbance types recorded in roads,
whereas, trampling was more common in roads rather than in trails (Image
3). Average percentage of disturbances
were significantly higher in roads than in nature trails (Mann-Whitney U test,
P >0.05) (Figure 2).
Variation of behavioral
responses in the presence of visitors
Behavioral responses
of amphibians
All species recorded displayed only avoidance and
habituation behavioral responses. Attraction behavioral response was absent in amphibians. M. greeni (73%), T. eques (82%), and P. schmarda
(88%) displayed habituation behavioral response as
the more prominent response. Avoidance behavioral
response was shown in lower percentages despite being shown by all three
species (Figure 3A).
Reptiles behavioral response
Only habituation behavioral
response (100%) was recorded from Cophotics
ceylanica. Both avoidance and habituation behavioral responses were observed from C. nigrilabris (85–15 %), C. stoddartii
(88–12 %), and A. trachyprocta, avoidance
being more prominent (Figure 3B).
Behavioral responses
of birds
Only avoidance behavioral
response (100%) was observed from E. sordidus, Pericrocotus
flammeus, Dicaeum erythrorhynchos, Rhopocichla atriceps, Turdoides rufescens, Pomatorhinus melanurus, Zosterops ceylonensis, Mortacilla flava, Hirundo domicola, and Lonchura malacca.
Only habituation behavioral response (100%) was
observed from Gallus lafayetii (Figure 3C).
Behavioral responses
of mammals
A mixture of behavioral
responses was observed in most of the animals. Rusa
unicolor and Funambulus obscurus were
recorded as the species that showed all three behavioral
responses. Attraction behavioral response was
observed from R. unicolor (78%) and F. obscurus (75%) rather than
other behavioral responses. Lowest percentage of
individuals was recorded showing avoidance behavioral
response in both these species (Figure 3D).
Behavioral responses
under vehicle noise
Average values of vehicle noise were 66.5 dB and 79.0
dB for habituation and avoidance respectively. The vehicle noise recorded was
in the range of 63±2.11 dB to 69±2.11 dB under habituation behavior.
It ranged from 70±4.71 dB to 88±4.71 dB where avoidance behavior
was observed (Figure 4).
Behavioral response
of tetrapod vertebrates under vehicle speed
When tetrapod vertebrates show behavioral
responses to vehicle speed, the average values of vehicle speed for habituation
and avoidance behaviors were 18.73 km/h1 and 38.45
km/h, respectively. Vehicle speed range was from 11±6.07 km/h to 29±6.07 km/h
under habituation behavior. Vehicle speed range was
from 30±5.01 km/h to 45±5.01 km/h under avoidance behavior
(Figure 5).
Discussion
Most studies of the effects of
roads on wildlife emphasize upon traffic mortality which has revealed that
roads act as complete or partial barriers to movement for some species (Rondinini & Doncaster 2002; Shine et al. 2004;
Whittington et al. 2004). Average number of road-kills recorded was higher
during vacation period in nature trails as well as roads than in non-vacation
period. However, road-kills were greater on roads than nature trails. The
reason for this is obviously the speed of the vehicles which have a higher
probability of colliding with animals when compared to the slow-moving human
visitors. However, the occasional road-kills were observed even on the nature
trails due to the faults of unaware visitors.
Amphibian road-kills were higher
on the roads as well as nature trails adjacent to aquatic habitats than in
other areas. Immobilization behavior of amphibians
(Mazerolle et al. 2005) on road and nature trails leads to increased mortality
rate. Pond-breeding amphibians (Rana arvalis)
that migrate in large numbers to and from breeding sites, are particularly
vulnerable to ‘‘collisions’’ with vehicles (Fahrig et
al. 1995).
Reptile road-kills were also
recorded in nature trails and roads. The possible reason could be snakes and
lizards getting attracted to open patches created by roads to use as basking
sites (Bambaradeniya et al. 2001; Karunarathna
& Karunarathna 2005) which consequently improves
foraging efficiency. Road-kills of birds were only recorded nearby the cloud
forest of road site. Throughout the survey, the only recorded road-kill was of
a Dull Blue Fly Catcher during its breeding months. Their nest sites being
located in road banks and tree holes (Dharmarathne
2018) become a possible threat to this species, particularly by the visitor
vehicles. Present study indicates that all road killed specimens of mammals
were of small mammals.
Most amphibian and reptile
road-kills were not identified to the species level due to rapid deterioration
of carcasses by travelling vehicle and weather conditions. Present study
indicated that C. nigrilabris has the highest
average percentage of nature trail mortality compared to other lizards species in HPNP. The results highlight that
road-kills occurred on road and nature trails are a threat to endemic species
vertebrate fauna of HPNP, especially the amphibians and reptiles.
Highest photography disturbance
was recorded on the nature trails. A lot of visitors preferred to take
photographs in aquatic habitat and cloud forest of nature trails. Visitors were
interested in taking photographs of chimney pool associated habitats and
tetrapod vertebrates that lived in there. Visitors often involve in close
approaches to wildlife for purposes of identification or photography (Green
& Giese 2004), hence there is potential negative impact on animals,
especially if flashes are used. Klein (1993) identifies photographers as the
most disruptive disturbance. Display of attraction behavior
of sambar was noticed due to animal feeding. Animal feeding was more prominent
disturbance on roads than in nature trails.
All amphibians were displaying
high amount of avoidance behavior indicating their
high sensitiveness for the human presence. Black-lipped lizards, Rhino horn
lizards and Common rough sided snake showed both avoidance behavior
and habituation behavior. Habituation behavioral response was mostly recorded from Pygmy lizard
which is a cryptic species that depends highly on its camouflage (Keerthiratne 2019). However, except for the Red Vented
Bulbul, Pied Bush Chat, and Sri Lanka Jungle Fowl, most other species more
frequently avoid the approaching visitors. Therefore, in general birds were one
group that were highly disturbed by the human presence in these habitats. Dusky
striped squirrel and Sambar displayed habituation, avoidance as well as
attraction behavioral responses. These two species
were frequently fed by visitors in the nature trail and could be identified as
two species that prefers human feeding over their natural foraging. Certain
individuals of these species could be observed habituated to sites where more
visitors gather.
Avoidance behavior
was recorded at high traffic noise level. High traffic noise poses a large
impact on birds, making it difficult for them to establish and maintain their
territory and attract mates. Moreover, Parris & Schneider (2009) suggest
that it reduces their reproductive success. Due to the inability of detecting
low frequency songs under traffic noise interference, they tend to sing at high
frequencies (Slabbekoorn & Peet 2003).
Trampling disturbance was posing
more danger to C. nigrilabris which more often
have their nest sites in the grassland habitat. Natural grazing ecosystem of R.
unicolor was also damaged by trampling of grassland habitat. Egg masses of
amphibians and some amphibians may be destroyed while trampling in aquatic
habitat and cloud forest.
Management implications
Since HPNP is a national park,
visitor disturbance and vehicle disturbance are always present in different
levels in cloud forest, aquatic habitat and grassland of nature trail and road
within HPNP. Effective visitor education is crucial in this regard whereby they
understand how to protect wildlife while enjoying wildlife. Previous posters
had displayed only sentences. If pictures are used to convince the humans
regarding their restrictions within HPNP it will be more effective since people
can quickly understand the pictures than sentences (without any language
barrier). According to present data, a maximum vehicle speed limit of 30 km/h
is recommended within HPNP. Road signs can be used to indicate that amphibians
are crossing a road and indicate the vehicle drivers to drive carefully and
slowly around aquatic habitats. If these measures do not reduce road mortality
effectively, a shuttle service should be established especially during vacation
periods. It can reduce the number of vehicles that enter HPNP. If medium sized
buses are used as shuttles, a group of visitors could be served at one round.
Moreover, some implementation should be applied in the vacation period to
reduce vehicular disturbances such as parking reservations for private vehicles
outside of the park. Animal feeding and trampling should be strictly prohibited
within the park and if people contravene this rule that could be fined by
department of wildlife conservation.
Appendix
1. Lat.-long. of starting to ending point within each transect of habitats.
Study
sites |
Cloud
forest |
Grasslands |
Aquatic
habitat |
|||||||
Nature
trails |
Transect |
A |
B |
C |
D |
E |
F |
G |
H |
I |
Start
points |
6.793160° 80.805249° |
6.792020° 80.805369° |
6.790795° 80.805298° |
6.796226° 80.805046° |
6.795560° 80.805128° |
6.794735° 80.804905° |
6.793655° 80.802986° |
6.793006° 80.802009° |
6.792414° 80.801383° |
|
End
points |
6.792394° 80.805579° |
6.791502° 80.805230° |
6.789718° 80.805417° |
6.795560° 80.805128° |
6.794735° 80.804905° |
6.793867° 80.804257° |
6.793086° 80.802415° |
6.792409° 80.801318° |
6.791904° 80.800601° |
|
Roads |
Start
points |
6.826310° 80.805438 |
6.826915° 80.806135° |
6.829553° 80.806104° |
6.806246° 80.805426° |
6.808065° 80.804211° |
6.810245° 80.802119°
|
6.830929° 80.806961° |
6.832925° 80.807812° |
6.838810° 80.811630° |
Ends
points |
6.826915° 80.806135° |
6.827565° 80.806488° |
6.830460° 80.806806° |
6.807325° 80.805243° |
6.808932° 80.803578° |
6.811071° 80.801873° |
6.831927° 80.807382° |
6.833247° 80.808554° |
6.839460° 80.812393° |
For figures and images—click here for full PDF.
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