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How New Method Of Contraception Could Prevent Human-Elephant Conflict

01/06/2015 8:09 AM IST | Updated 15/07/2016 8:25 AM IST
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Section Ranger Gary Bawden HSUS

Elephants feature prominently in the religious, social and cultural history of India, evoking emotions that range from wonder, respect, love and fear. However, this elephant-sized space of reverence that they occupy in the Indian imagination is jeopardized by Human-Elephant Conflict (HEC).

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Audrey Delsink Kettles/HSUS

Asian elephants (Elephas maximas) inhabit tropical, deciduous or scrub forests interspersed with grasses and adequate water sources. They live in tightly-knit herds that comprise of related cows and their calves. Males leave the herd at 10 to 15 years of age. As elephants consume large quantities of food daily, they migrate seasonally to ensure optimal usage of resources within their habitat, thus allowing the environment to replenish itself. Being creatures of habit, their quest for food occurs along fixed paths.

However, as large swathes of contiguous forests are destroyed for infrastructural and agricultural activities, India's estimated population of 30,000 elephants survives in isolated forest patches. Dwindling food resources diminish the carrying capacity of these patches, triggering elephant migration in greater numbers and frequency, thereby increasing the rate and intensity of conflicts with humans.

"According to the Ministry of Environment and Forests approximately 400 humans and 100 elephants die annually due to HEC [human-elephant conflict]."

According to the Ministry of Environment and Forests approximately 400 humans and 100 elephants die annually due to HEC. As per the Wildlife Trust of India, train accidents in elephant habitats have caused 110 elephant fatalities since 1987. Hungry elephants may raid croplands that lie in their migratory paths or along forest edges. Scientists believe that "problem elephants" aren't born; they're made. Apart from migratory routes and behaviour, elder elephants teach calves foraging patterns that may include crop-raiding. The ensuing conflict results in a considerable loss of lives and livelihoods. People have employed short-term methods to contain conflict such as the use of chilli bombs, firecrackers and electric fences, but these practices lose their efficacy over time.

HEC may only be mitigated through population management. In India, elephant populations are managed through translocation and capture of wild elephants for captivity. While some translocated elephants return to the site of conflict, others may cause trouble in their new locations. Capturing elephants for captivity is a contentious issue as it can only be done under explicitly detailed circumstances and may involve cruel methods like confinement, starvation and the use of brutal force.

In South Africa, a novel approach called immunocontraception has been successfully used to manage populations of wild elephants. First developed at the University of Tennessee in 1972, it has worked effectively on 80 mammalian species including the African elephant (Loxodonta africana). It is a reversible, non-steroidal, non-hormonal, non-invasive contraceptive that is administered through a vaccination. The drug comprises protein-based components called porcine zona pellucida (PZP) extracted from the ovaries of domestic pigs. The zona pellucida is the capsule that surrounds all mammalian eggs. When PZP is injected into a breeding female, her body produces antibodies that bind to sperm receptor sites of the capsule. Since the sperm has nowhere to attach, fertilisation and pregnancy are prevented.

"It is a reversible, non-steroidal, non-hormonal, non-invasive contraceptive that is administered through a vaccination."

This study was carried out under the aegis of the University of Pretoria (UP), with considerable financial support by Humane Society International (HSI). Following the reasonable success achieved in the two field trials in Kruger National Park in South Africa, immunocontraception was applied in the Greater Makalali Private Game Reserve (GMPGR). The project commenced here in 2000 and was first tested on 18 elephants. As of 2015, 26 cows were treated in GMPGR; the treatment has been reversed in five of these. So far, the method has shown almost 100% efficacy.

In GMPGR, cows aged 10 years and older were administered a single dose of the PZP vaccine followed by two booster shots within five to seven weeks. Treatment was prolonged with a single annual booster for as long as required. (Since calves play an integral role in elephant herd dynamics, the technique was later reversed in some cows who were allowed to breed.) Even if a pregnant cow was darted at any stage of pregnancy, both cow and offspring remained unharmed. The study at GMPGR showed that immunocontraception was a safe method to manage elephant populations. Individual elephants showed no physical or behavioural abnormalities either in the short- or medium-term; HSI and UP are currently monitoring long-term use. Studies showed that herd and population behaviour remained unaffected despite the decline in the number of calves within. While oestrus cycles were more frequent, copulation and ovulation were unaffected. Once administered, PZP is metabolised by the body and doesn't pass into the food chain and hence, has no effect on any other species in the same habitat.

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Section Ranger Gary Bawden/HSUS

Currently, immunocontraception is used to manage growth rates in 20 elephant populations in South Africa. So far, more than 500 cows have been treated. Whilst vaccination rates are dependent on site-specific management objectives, researchers in GMPGR chose to increase the inter-calving period instead of aiming for a zero growth rate in population. (Among elephants, inter-calving intervals tend to increase during adverse conditions like drought when availability of food and water dictate that the population needs to be controlled. Application of immunocontraception is designed to mimic such natural, episodic catastrophic events.) Thus, the growth rate of populations was managed in accordance with the carrying capacity of their habitat as well as the innate social and spatial nature of the species.

This method was tested successfully on captive Asian elephants. It is currently being reviewed for its potential in controlling HEC in India. Moreover, this method may be applied to nilgai, blackbuck, wild boar, langurs and other mammals which are responsible for crop depredation. Although immunocontraception as a mechanism of conflict mitigation may seem radical, it has the potential to form the framework of a conservation policy that relies less on emotion and rhetoric and more on sound science as it allows both elephants and humans their space and helps in alleviating conflict.

When elephant-sized spaces become empty, they are very hard to fill -- both within the human imagination as well as the ecosystem.

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