Why are baby elephants dying in The Secret Life of the Zoo?

The zookeepers at Chester Zoo discuss the recent death of Bala the elephant, and the disease that's plaguing our zoos

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Alongside his friend Bala, elephant calf Hari has entranced millions with his playful antics on Channel 4’s The Secret Life of the Zoo. But after Bala’s death in last week’s episode, it looks like Hari, too, may not reach his third birthday.

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Bala is the fourth elephant calf to die at Chester Zoo in the past seven years. She is just the latest casualty of a deadly, mysterious disease that is killing Asian elephants in captivity.

Bala, an Asian elephant calf, grew rapidly ill and eventually died from elephant endotheliotropic herpes virus (or EEHV). For most of us, this will be the first time we have heard of elephant herpes. But the disease poses one of the biggest threats to Asian elephants in captivity, and has killed 11 in the UK since 1995. With only 43 Asian elephants in British zoos at present, the disease is taking a huge toll.

There is no known cure for elephant herpes, which has an 80 per cent death rate. Between 1995 and 2013, 30 per cent of Asian elephants born in the UK died from it, putting breeding programmes – and the already endangered species – at risk.

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So what exactly is elephant herpes? Dr Jonathan Cracknell, a leading world expert in the disease and the current director of animal operations at Longleat, likens it to herpes in humans. “Cold sores are a good comparison for elephant herpes,” he says. “Most humans have the herpes virus, but it only flares up and causes a cold sore when you’re run down, and the immune system is weakened.”

Similarly, most elephants are thought to carry strains of EEHV – it’s believed to have been around since elephants first roamed the Earth – and is transmitted between elephants through trunk secretions and saliva. When the immune system is weakened in young Asian elephants, it can become deadly, predominantly causing illness in animals during weaning, which can be between 18 months and five years old. The symptoms develop fast, and include lethargy, a loss of appetite, a change in attitude, and a bruised tongue. Tragically, by the time these are apparent, the animals usually die within 24 to 72 hours.

Other diseases, breeding, and a move to a new location can bring on the illness, while changes in the herd dynamic caused by pregnancy or introducing a new animal are also very stressful for elephants. “There have been cases where a new elephant comes in and a calf dies within six months,” says Cracknell. Younger elephants are most vulnerable because until they’re weaned they receive antibodies from their mother’s milk. When this stops, there is a period when their immune systems are still developing and more susceptible to disease.

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Losing Bala has been devastating for the staff at Chester Zoo, as well as the remaining members of the herd.

“Elephants are playful, social animals,” explains Mike Jordan, the zoo’s director of animal and plant collections. “When you lose a youngster, the herd is changed. They’re very protective, and we notice a change in behaviour as soon as the calf is sick. Its mother knows, and the herd knows. When one dies, the others gather around it and there’s a period of grieving.”

At the zoo, animals are now given a blood test every week to test for the disease. “It gives us an early warning,” Jordan says. “We don’t wait until we see the sickness; if we know we have a positive result we immediately start treatment. There’s no prevention, and there’s still no definite treatment – all we and other zoos are able to do is give human antiviral drugs.” Most commonly, a shingles drug called Famciclovir is prescribed. But the dosage needed to treat one elephant can cost over £20,000 – and the chance of survival is still minimal.

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Is keeping elephants in captivity the problem? “Herpes virus is not brought on by captivity, but as in the wild there are always stress factors that can potentially lead to disease,” says Cracknell. “What we think is happening is that populations have been exposed to these viruses for millions of years, but in zoo herds, you can have an Asian elephant from Thailand and another from Burma. Captivity will have caused the mixing of these, and their different strains of herpes, faster than they ever would have in the wild.”

The predicament for conservationists is grave. Is it right to carry on breeding when so many of the calves are at risk? Asian elephants are an endangered species, and rely on the breeding programmes of zoos and research undertaken in captivity to keep the population viable. Bringing elephants in from the wild is deemed unethical, so breeding them in captivity is our only way to study the animals and try to ensure the species’s survival. Programmes in the UK at zoos like Chester and Whipsnade have enjoyed great success. With a gestation period of two years, elephant births are still relatively rare – and are cherished and celebrated, as we saw in the first episode of The Secret Life of the Zoo with the birth of Nandita.

“Our success in breeding is highlighting the gaps in our knowledge of this disease,” says Cracknell. “The loss of so many elephants isn’t a reflection of failure at a zoo, it’s the opposite. It’s the zoos that are successful at breeding that see the most cases. The good zoos breed, and if they breed there is a risk that the new elephants could die of the herpes virus. If you stop breeding, elephants are going to become extinct in captivity within our lifetime. It sounds horrible, but the only way to learn about this disease –which is also found in the wild – is to carry on breeding and learn from the ones that die.”

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PHOTO CREDIT: Marie Benjamin

The decision about whether or not to continue breeding has been debated by the ethics committee at Chester Zoo, and is something Jordan feels strongly about. “It would be very easy for me to say, ‘We will stop breeding elephants.’ It would be easier on the staff, because losing one is very hard and desperately sad, but I think, from a conservation perspective, breeding is our moral responsibility. If we stop, our knowledge of this disease will not advance at all. If it then goes on to become a major cause of death in the wild, we won’t have the tools to help conserve elephants.”

Cracknell agrees. “The way Asian elephants are going, they’ll be extinct within our lifetime, or at least at a point from which they can’t recover. This disease is shocking, it takes everything. It’s soul-destroying.”

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The Secret Life of the Zoo continues on Tuesday 1 March at 9pm on Channel 4