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Not just us, animals too face the brunt of noisy vehicles

Read time: 6 mins
Noisy vehicles cause distress to animals. [picture credits leopard and safari vehicle via Wikimedia Commons]

Noisy vehicles cause distress to animals. [Picture credits: leopard and safari vehicle via Wikimedia Commons]

Nestled among the Aravali mountain range and in the heart of Jaipur city in Rajasthan is a 29 sq km spread of raw wilderness - the Jhalana Reserve Forest. Once teeming with wildlife -- tigers, leopards, boar, deer and various birds -- Jhalana was a favourite hunting ground for the Maharajas of Jaipur. Sadly, human ravages have wiped away most of the big cats; About  35 leopards remain today as the only surviving apex predators in the forest.

Leopards are shy and territorial. However, at Jhalana, they are seen roaming freely and even crossing paths with human activity zones. The surprising behaviour of the prowling cats presents a unique human-carnivore interaction situation, drawing the attention of wildlife researchers.

The Rajasthan Forest Service restricted vehicles in the Reserve, installed CCTV cameras and scaled up patrolling to check human intrusions. "However, despite these measures, the department lacked scientific baseline data for managing and maintaining the Reserve, which has a delicate situation: an absence of human-carnivore conflicts," says Mr Swapnil Kumbhojkar, a researcher at Jhalana Wildlife Research Foundation, Pune.

So, Mr Kumbhojkar, along with a team of global wildlife experts, presented a proposal to employ scientific methods to manage the reserve and study the effect of developmental changes on the wildlife of Jhalana. Recently, the team assessed how noise levels of safari vehicles impact the behaviour and response of some mammals and birds. Their observations, published in the journal European Journal of Wildlife Research, establish that the quieter electric safari vehicles make a significant difference to the disturbance caused to wildlife. Their study has set a benchmark for ecotourism methods. As a result of this study, an upcoming Reserve near Jhalana is in the process of procuring electric vehicles for plying in the forest.

In 2017, the forest department declared Jhalana a forest reserve and opened its gates for leopard safaris. The forest department mandated the use of customised safari vehicles (Gypsy - off-road vehicles). In 2019, they added six electric vehicles (Mahindra e-vehicles) to their fleet.

Over a week-long observation, the team recorded how several species of birds and mammals respond to the noise caused by safari vehicles. "Animals react to noise and sounds in three ways - a) initial alertness b) observe and watch briefly and c) when threat is perceived, take flight," says Prof Reuven Yosef, first author of the study and wildlife researcher at Ben Gurion University of the Negev-Eilat Campus, Israel. The researcher has previously worked extensively on tigers at Bor, Maharashtra.

Global studies have shown that animals become wary of human presence and respond by halting grazing, resting or foraging and standing still. If such reactions prolong for longer durations, they can alter the animals' normal behavioural patterns.

Hence, the researchers hypothesised that with e-vehicles, the noise level would be lower and therefore cause less disturbance to the animals' normal behaviour.

Using a mobile application called the Sound Meter App, the researchers measured the engine noise of all the vehicles in three different conditions - in idling, running, and revving modes. The App also enabled measuring the noise's minimum, maximum, and average levels (in decibels). Then they measured the total noise level of all the vehicles for the three states.

A read-out from the App showing the the noise levels of regular safari vehicles (L)  v/s e-vehicles (R)

The primary animal response aspect of significance in their study was the Flight Initiation Distance, FID. The FID is the closest distance the vehicle can get to an animal before it takes flight. Binoculars with rangefinders helped the team measure these flight distances for each species under scrutiny. They made daily measurements for all the 13 vehicles in the three modes of operation. In all, they observed 227 FIDs -- 174 for five bird species and 53 for three mammal species.

However, wildlife observation can have multiple parameters leading to complex datasets and analysis. For example, different species perceive sounds differently; the weather and tyres rubbing on the gravel on the forest trail can add to the noise. Besides, species-dependent aspects, such as familiarity with humans as a perceived threat, also come into play in the forest.

Therefore, the researchers used statistical and graphical methods to normalise and eliminate the irrelevant parameters in the observation data. They employed the General Linear Mixed Model (GLMM) approach to analyse complex data. GLMM is a sequential analysis technique wherein the unwanted data are removed at each successive step of the analysis, narrowing down the data set to the most reactive parameter.

"By this method, we can start isolating the not so significant parameters and narrow down the analysis to the significant parts. Then, we concentrate on those reactions of the species that are giving us a significant relationship," says Prof Yosef.

He adds that animal reaction is the statistically significant parameter in this study, not environmental factors. For example, initially, the analysis encompassed a large dataset of both birds and animals. However, they found that the birds were not so affected by the noise levels as they were arboreal and perceived the ground disturbance as a low threat. Hence, they filtered out the birds' response data for the subsequent analysis. 

The team observed that for regular off-road vehicles, the distance at which the noise was perceived as a threat that made the animals scoot off to safety was longer than for the electric vehicles. In other words, the Flight Initiation distance was closer for e-vehicles compared to regular vehicles.

The less noisy e-vehicles accord a shorter Flight Initiation Distance of the animal (pictures courtesy authors)

"From these analyses, we concluded that the type of vehicle was a key parameter that elicited a reaction from the animals," say the authors.

When they analysed species' responses, they found that the most significant reaction was obtained from the leopards (shy creatures). 

The researchers posit that scientific methods are imperative to managing ecotourism. "Wildlife study cannot be a populistic project or be left to lay-understanding. On the contrary, the real understanding of wildlife can be done only scientifically, studied thoroughly and professionally," avers Prof Yosef.

The experts emphasise that any change made to the existing situation should be thoroughly backed up scientifically. Any development activity will bring a difference in the environment, which must be studied beforehand. Hence even if declared a reserve, the area should not be left to the local jurisdiction. Instead, the governing body must work with scientists to keep the delicate balance going. "Because if they do the wrong thing and tip the balance, a coexistence will soon turn into a conflict," caution the authors.


This article has been run past the researchers, whose work is covered, to ensure accuracy.