All living organisms are biological beings and share a common and intertwined biological heritage. We, humans are mere one of the thousand species of organisms to inhabit this planet. Yet, we control the existence of all other living beings to an extent we decide who will live and who will die. Since evolution, humans have been in relationship with other animals in the form of companionship or sources of food, labor, clothing and recreation. This relationship is based on various religious and cultural preferences. Unfortunately, we have also relied significantly on culling as a conservation method
Culling of animals for a variety of reasons is often practised worldwide as a cost effective method. The ecological value it offers and the justification given for its practice are often vague and unscientific. To those with humanitarian views, this oftens comes out as a barbaric, human centered and selfish procedure which views animals as commodities to be used by humans.
Especially when the practice of One Health, a bioethical, social , scientific and environment friendly approach to improve the wellbeing of every living species of the earth is slowly gaining momentum, it is time to review the effectiveness of culling and the benefits reaped by it.
What exactly is the meaning of culling?
Biologically culling is defined as the process of separating organisms from a group according to desired or undesired characteristics. It is also used as a term to describe indiscriminate killing within one particular species which can be due to various reasons such as disease prevention or controlling population.
The History of mass Culling of Wildlife
Culling of animals has been a common public health intervention for preventing spread of zoonotic diseases for many centuries. The first written documentation of the practice was done by Dafoe in his fictitious reporting of the outbreak of plague in 1664. After fifty years in 1714, Royal Surgeon Thomas Bates suggested isolation, culling and burning the carcasses of cattle infected with rinderpest.
Around 300,000 dogs were culled in Flores, Indonesia, over a four-year period in response to a rabies outbreak on that island in 1997. Inspite of this rabies still remains endemic in that region. In June 2019, millions of pigs were culled in China and Vietnam to curb the spread of African Swine Fever as the Food and Agricultural Organization(FAO) urged Asian governments to make this their top priority.
Recently the world saw global outbreaks of H1N1 and H5N1 viruses within a span of two years requiring millions of poultry animals to be culled. Although culling has become a popular intervention, it is not the evidence-based solution for curbing disease spread.
What are the advantages of culling?
Economic benefits
In commercial farming such as dairy or meat industry culling helps to increase the yield of the produce. Culling is done based on factors affecting animal’s performance, such as milk production, reproductive status, and diseases. Those with undesirable traits are culled, allowing farmers to drive profitability.
Achieving a sustainable population
Culling is done to achieve a sustainable population in an ecosystem. Overpopulation may increase conflicts amongst animals and also with humans. In 2016 South Africa culled hippos in Kruger National Park after a drought. Without culling, all or most of them would have died of starvation.
Reducing spread of viral diseases
Animals, birds and insects act as a host to many zoonotic diseases which can be fatal to them and humans. This requires culling of infected hosts. The 1997–98 outbreak of the Nipah virus in Malaysia, claimed the lives of over a hundred pig farmers. It was curtailed by the culling of more than one million pigs. In India, animal culling is practiced to prevent zoonotic diseases (H1N1, H5N1, etc.) and to reduce the number of pests..
For instance, in the year 2008, a sudden outbreak of H5N1 resulted in the death of around 10000 poultry chickens in three districts of West Bengal. The State government ordered complete culling within 5 km radius in 13 districts. The total losses were estimated to be 4 million birds. Farmers and poultry owners suffered a greater loss in terms of income and a source of livelihood
Eliminating the risk of pests
Some animals pose a serious threat to or interfere with human activities. In New Zealand, after WWI, the emus had multiplied so fast that they were a danger to farmers. They were eventually brought under control when over 60,000 emus were culled in 6 months. In Denver, Colorado, the famed Canadian geese became a public nuisance at some point. Eventually, the state government decided to cull them.
Strengthening the genetic pool of animals
By culling , animals or birds with undesirable qualities or genes are exterminated. The survivors are healthy with strong genes.
Ethical dilemma surrounding the practice of culling
Humans and animals have shared a deeper relationship with animals since their existence. Unfortunately, humans are the dominant species of this planet and have used their dominance over all other species from time to time. As a result, humans can label any other species as pests and decide to terminate their existence.
Should we leave them alone, unless we need to farm them. We use them as laborers, eat them, hunt them, and kill them if their numbers increase. We seldom recognize their existence as co-species sharing this planet. Hence many people argue over the rationale behind culling used for population control or selective breeding as done in dairy, meat and poultry industries.
Poultry industry as a norm requires culling of hens every 3 years and only male cocks are kept. On the contrary, often female chicks stays and males are culled since they cannot lay eggs. Similarly in dairy industry , if a particular cow is not giving good yield of milk, has poor reproductive health or is found to be diseased ,the animal is included in the culling list. Very old animals are culled, as their maintenance will be uneconomical. Male calves, calves born with low birth weight, those born with congenital deformities are culled straight away.
How is culling practiced?
Culling has to be carried out according to International health regulations. In India, culling of poultry animals after an outbreak of epidemic is done by government appointed veterinary doctors. “The birds should be culled by a quick twisting of the neck (cervical dislocation), taking care that the process is humane,” states the Action Plan for Prevention, Control and Containment of Avian Influenza.
Currently the process requires birds above 3 kg to be administered oral anaesthesia. The caracass of dead birds should be buried or incinerated in a deep pit.
Dairy animals are often transported to meat processing units to be slaughtered. Other big animals and birds targeted for culling should be hunted down by licensed hunters. However, in reality humane approach are seldomly used by farmers or dairy owners. Male chicks are often suffocated or brutally electrocuted. During the Avian influenza pandemic a Indian poultry owner panicked and buried alive around one lakh chickens inside a pit just by throwing them one by one without remorse!
Does culling really help in managing overpopulation of a particular species
A ‘legitimate’ mass culling of crows
A case study conducted by Heinemann K et al on the efficacy of culling of Hooded crows(Corvus cornix) and European magpies ( pica pica) in the Turkish Republic of Northern Cyprus (TRNC) showed contradictory results. Every year about 15000 – 20000 corvids are culled in Northern Cyprus, since they prey on the eggs of the regular game birds and harm animals such as hares in a game reserve. This is done through licensed hunters from hunting clubs and termed as ‘ legitimate’ method of population control.
The authors found that the culling season falls during the breeding season of the crows and the male crows are accidentally being targeted since the females are usually in the nests. This should have led to disruption in social structures. However, the corvids quickly adapted by increasing their breeding density and have stabilized their population number.
Similar case study done by Lazenby et al in 2014 on feral cats of Tasmania. It was decided to reduce the population of feral cats. Hence the cats were trapped and killed. After an initial dip in their numbers, the population of cats began to increase significantly. The removal of some individuals makes space for more food and increased reproduction rates in those left.
What about other taxa?
Another study conducted by Tsutomu Enoki et al on population of Sika deer(Cervus nippon) before and after culling showed a temporary decrease in density of Sika deer and the damage caused. However, the population increased after several months after culling. This was because the area was repopulated with deers from the surrounding areas.
The Randomized Badger Culling Trial (RBCT) in the UK is the best-documented example of wildlife culling for disease control and the after effects of culling badgers on bovine tuberculosis levels. This field experiment was carried out between 1998 -2005 and spanned across 3000 kms in England.
It was found that culling could increase disease incidence in cattle populations, increase disease prevalence in badgers in the target area and also in surrounding areas.
During the culling period, the level of disease within infected groups typically decreases. Continued culling then leads to a decline in the number of infected individuals. When population reduction ceases, there is a small increase in infected groups. Disease levels in the newly infected groups increase towards an equilibrium level.
This badger culling has garnered a lot of public criticism since last ten years. The British government has also received many petitions to ban this unethical practice.
Alternative methods of population control
In recent years, fertility control has emerged as a non-lethal alternative to culling, especially where hunting and use of toxins is banned.
Croft S et al led a team to conduct a study on efficacy of contraception as complementary to culling methods in controlling the closed population of wild boars in U.K and Italy.
The results showed that fertility control alone was not enough to reduce populations of wild boars( Sus scrofa) but that the addition of fertility control was more effective than culling alone. Specifically, when contraception was used on 40% of the population in addition to culling 60% of the animals, the time to reach the reduction target was halved compared to culling alone.
Similar results were obtained in a white-tailed deer (Odocoileus virginianus) model (Raiho et al). Annually 40% of females were treated with contraceptives after reducing the number of animals to the desired target with the help culling.The population remained below the carrying capacity.
Castration also an alternative!
The alternative methods of population control also use the method of controlling sexual behavior and reproduction of animal species.
In agricultural animals, castration has served to control aggressive male sexual behavior, for animals to reach slaughter weight more quickly and therefore cheaply, and to improve meat quality. Horses who are not required to breed are also castrated.Similarly spaying female cats can control the sexual behavior when in heat. However many times such procedures are done without anaesthesia causing immense pain to the poor animal. Such procedures and methods are being targeted by animal right activists and NGO’s.
Due to rise in ethical concerns a non surgical method like vaccine against GnRH( Gonadotropin releasing hormone) which is commercially used in mares and keeps them in non estrous period for long time. This vaccine is also tested to be used in pigs and white tailed deers.
How indiscriminate culling has endangered some wild species?
In South America, many governments called for culling of vampire bats since they were associated with fatal rabies virus. However, people were not able to distinguish between the different types of bats. As a result of many insectivorous bats, which help to reduce crop pests, have been killed in the process.
In Mauritius, the flying fox was cause of great losses for farmers, as a result significant population was killed. Later it was discovered that the flying fox was the chief agent of pollination for more than half of the island’s plant life. In a paper published by Lederman et al, the authors put forth that public health policies primarily based on culling fail to adequately consider the interests of those involved other than humans and that we need to move from an anthropocentric approach to disease control towards a One Health ethic.
Conclusion
To conclude, culling as a method to curb population can often lead to undesirable side effects. The world needs to move on towards more humane and ethical approaches which are scientifically proven.
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Written by: Dr. Nupur Sawant