Organisation - June 7, 2019

Stage of swan lake left empty

Text:
Roelof Kleis
1

At first, there were eight balls of fluff. Then three, and suddenly one. Now they are all gone. The swan couple in the Forum pond is left childless. The perpetrator most probably swims at large.

The swan couple in happier days. © Askhat Zhanibekov

Askhat Zhanibekov, second-year master’s student in Business Economics from Kazakhstan, closely follows the swan couple. Just like many others with him who reach the campus every day by crossing the bridge across the pond. The swan couple breeds there every year, with varying degrees of success. At first, this year seemed to be a great year. ‘They had no fewer than eight beautiful chicks.’ The student took gorgeous pictures of them.

Stolen?
‘But two weeks later, I saw only three’, he e-mailed Resource. ‘I thought - okay, that must be natural selection. The strongest survive.’ But a few days later, only one was left following its parents. And it has now been missing for a week. Zhanibekov wants to know what’s going on here. ‘Is it a shortage of food, are natural enemies involved, or have they been stolen?’

Chicks are on the menu. It is natural selection, and we do not intervene.
Elike Wijnheijmer

‘It’s the pikes’, says park manager Elike Wijnheijmer resolutely. ‘Since the ponds were laid out, some 15 to 20 years ago, an ecosystem has developed – including pike at the top of the food chain. And chicks are on the menu. It is natural selection, and we do not intervene. According to experts, pike are part of a healthy ecological balance of a pond.’

leeg zwanennest.jpg

‘That’s right’, agrees aquatic ecologist John Beijer. He knows the ponds at Forum and Orion like the back of his hand. He often takes students there to do practical courses. ‘Pike are the top predator in an aquatic system. They eat fish, maintain the pond and ensure the water stays clear.’ And they won’t turn down a chick snack. ‘Especially the larger pikes, those are usually the ladies, can get hungry’, says Beijer.

Culprit
The fact that there are such large pikes in the Forum pond is beyond doubt. ‘Last year, I saw a pike between 70 and 80 centimetres under the bridge. It is most certainly still there. That could be the culprit. I saw a pike grabbing a coot chick in a lake nearby my house. But it could also have been herons or buzzards that took the swan chicks.’

I was looking at the swans, when suddenly the mouth of a fish popped up and pulled the chick right down.
Ellen Torfs

That could be, but it does not rhyme with what Ellen Torfs (Education Support Centre) saw last week. By chance, she stood on the bridge in the afternoon when a pike grabbed the last chick. ‘I was looking at the swans, when suddenly the mouth of a fish popped up and pulled the chick right down.’ It wasn’t until 15 seconds later, while she was still staring at the crime scene, that the chick suddenly reappeared. Seemingly unharmed.

Catch
The following day, the bird had disappeared after all, as Zhanibekov noted with regret. He believes that something should be done to protect the young. If only because the swans bring some charm to the campus. Ecologist Beijer does not by definition reject intervention. ‘If the pike is the perpetrator, and we all find it sad that he eats the swan chicks, we could choose to catch the animal.’

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  • Cristina

    Maybe the solution, instead of catching the pike, could be protecting closely a couple of the chicks next year, in order to ensure that they would reach adulthood. It would be sad that eventually the swans died and we would end up without any of them in WUR. Moreover, if pikes are so important for the ecosystem, it would be very unwise to catch it.

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