Why do some biologists keep the most unusual pets?

On World Animal Day, everyone pays a little extra attention to their pets. These are usually cats or dogs – but why do some biologists keep such eccentric animals at home?

Hundred years ago, World Animal Day was celebrated for the first time, when the Polish journalist and animal welfare advocate Heinrich Zimmermann organised an event in Berlin focused on animal rights and welfare. On 24 March 1925, more than five thousand people attended, and the idea was born to hold an annual, worldwide Animal Day. In 1929, a meeting in Vienna decided to move World Animal Day to 4 October – in keeping with Zimmermann’s original wish – the feast day of animal lover and saint Francis of Assisi (1181–1226).

On this day, pet owners around the world spoil their animals and give them a little extra attention. According to an annual pet survey by industry associations, 44 per cent of Dutch households own a pet, including 3 million cats (in 23 per cent of households), 1.7 million dogs (in 16 per cent) and 6 million aquarium fish (in nearly 4 per cent). Around 150,000 reptiles also spend their lives in Dutch terrariums. Bionieuws sought out biologists who deliberately keep unusual animals at home and asked them about the how and why of their hobby.

‘At the moment I have six ant colonies – three of exotic species and three started from queens of black garden ants I caught in the street. I got into it because I was working as a postdoc on metabolism in the Florida carpenter ant. It seemed like a great way to get to know the hosts of my research better, alongside the computational models of metabolism. It gives me satisfaction and inspiration.’

‘It’s not difficult to get started: all you need is a mated queen, a test tube, a damp cotton plug and – once they have workers – sugar water or seeds as food. This summer I also brought in a few queens of pavement ants from my front door. The exotic ants are kept in a kind of terrarium made of transparent tubes, and the street ants are still simply living in test tubes.’

‘The main thing you have to learn is to leave them alone: it’s completely unlike having a cat or dog, but you do build a bond with them because they depend on you. I also had a shock when, after a weekend away, an entire colony had disappeared from the box they were living in. I searched everywhere, but eventually found them in a box nearby – apparently they preferred that one. Things are about to get interesting: I’m starting a new job in Germany soon, and we’re all moving together, because the ants are obviously coming with me.’

‘You could perhaps call it a hobby that got out of hand, but I see it more as a passion pursued in a professional manner. These little frogs offer me everything that made me want to study biology in the first place: they have a fascinating life cycle, lifestyle and parental care. For me it started with fish in an aquarium, but during my biology degree – inspired by a fellow student – I switched to poison dart frogs and terrariums. I put a great deal of effort into making it my professional field as well, but couldn’t do a PhD on them. I did my doctorate on insect–plant interactions, and that has become my current research area. I’m actually glad that my work and hobby have remained separate as a result: after a busy day at work I can completely retreat and unwind with my frogs. We even took them into account when choosing our home: the frogs are kept in a separate section near the basement – a fully heated and tiled room, so that the living areas aren’t affected by damp. I’ve automated a great deal, which means I can still be away from home for three to four weeks at a time. I write articles for the colour magazine of the association Dendrobatidae Nederland and am co-author of the handbook Gifkikkers. It is packed with knowledge about poison dart frogs, and make no mistake: worldwide, it is primarily enthusiasts who conduct research on this group of animals, discover new species and work to protect their habitats in South America. They’re not cuddly creatures, but I get an enormous amount of pleasure from them.’

‘Alongside all sorts of fish, I keep Madagascar hissing cockroaches, which I’ve named the Zaza family. It’s already handy that I can give them all my vegetable scraps, and it’s great fun watching them munch away. They also look incredibly cool. We had a tank of hissing cockroaches at school, which I once took home during the holidays to look after. That was so enjoyable that I thought: I want some of my own. So I built a new terrarium and split the colony; part went back to school and part I kept. That was no problem at all, because they reproduce at a tremendous rate. Every now and then I have to thin the population out a bit. I believe a lot of people feed them to their reptiles, but these cockroaches are of course far more interesting than reptiles themselves.

‘They’re very easy to keep otherwise – I really don’t have any problems with them. Visitors find it strange, but then, they know me. I often get asked “but what if they escape?”, though that wouldn’t actually be a problem. These are not pest cockroaches, and they need a humid, tropical climate. Outside the terrarium they certainly wouldn’t reproduce successfully.’

‘The axolotls, giant snail and fish in the UBV room in the Koningsberger building are a real draw for students: there’s always something to see. Students love coming to look at our pets, and sometimes they also take water samples from the aquaria for microbiology practicals. Animals and plants are part of studying biology, and axolotls are especially remarkable because they are salamanders that have evolutionarily become stuck in a larval stage. We once had two small water turtles here as well, but they didn’t survive and ended up mummified.

‘As an association, we try to manage this living legacy as well as we can. There are around ten people in the working group who, via a group chat, make sure the aquaria and terraria stay clean and that the animals are fed even during the holiday period. The axolotls were taken over from the Faculty of Veterinary Medicine about ten years ago, when they didn’t know what to do with them. And the giant snail is at least twelve years old, even though they are said to live for ten years at most. Apparently we once had two, but that’s not a good idea: before you know it you have hundreds of tiny snails. The university was a little wary that the giant snail might escape, but we managed to convince them that things wouldn’t get out of hand.’