From ferret electricians to landmine-sniffing rats – meet the extraordinary animals that work for a living
Our relationship with animals is deeply peculiar, spanning the spectrum from besotted to breezily exploitative. Whether they are friends, pests, assets, dinner or catnip content creators, the relationship tends to be heavily skewed in our favour. We might look after our pets devotedly, but most animals aren’t so lucky in their encounters with us.
There are a few instances, however, where human interests and animals’ natural behaviours and inclinations more or less align. Most aren’t technically “mutualistic” interactions between two species that benefit both, like a clownfish hiding in and cleaning up its sea anemone. Even so, there is a cheering amount of win-win in a handful of our relationships with the natural world. Let’s take a look at some of that mutual back-scratching.
Bat librarians
The baroque Joanina Library at the University of Coimbra in Portugal is well known for its exquisitely detailed gilding and woodwork, but also for what its deputy director, António Maia do Amaral, calls its “honorary librarians”: bats. Amaral explains that there are two small colonies – free-tailed bats and pipistrelles – living in Joanina. They have been there for centuries: 18thcentury library paperwork documents an order of large leather sheets from Russia; these sheets, known as “moscovias”, are still unrolled at night to protect the huge embossed tropical wood tables from bat droppings.
Whether the bat librarians are actually helping is a moot point. The assumption is that they feed on bookeating insects that could damage the library’s precious collection, but their droppings have never been analysed to check. “As far as I know, it has always been a peaceful coexistence, even if their role in pest control is maybe marginal,” says Amaral. “We cannot trust bats alone to preserve the books from flying insects. For that purpose, we have a six-cubic-metre anoxic chamber for cleaning the books.”
The bats are part of the library anyway, even if they are only occasionally spotted (usually at evening events, when they flutter out from the shelves to entertain guests). Visitors are intrigued – you can even get a baseball cap with a Joanina bat on it – but opinions within the library vary. “My first director was always very annoyed when asked about the bats’ existence,” says Amaral. “He felt that bats were the least important thing in the library, because he was such a cultured man. Nowadays, people are more often benevolent and amused with the bat story. Personally, I’m very happy with the bats and pray for their good health.”
The bats weren’t the only honorary librarians in previous centuries, Amaral adds. Historical library records included an annual sum in the budget for feeding Joanina’s mouse-hunting cats; you can still spot “cat doors” cut into the woodwork.
Ferret electricians
“Ferrets are, if you want to be polite, inquisitive; if you want to be blunt, they’re nosy little devils,” says James McKay of the National Ferret School. “When you put them in any opening, they want to go through and see what’s at the other end.” Their curiosity, shape and sinuous flexibility mean they can get to places and do jobs no human could manage. Felicia the ferret became a furry pipe cleaner for the Fermilab particle accelerator in Illinois in 1971; ferrets wriggled under the floor of St Paul’s Cathedral to enable TV transmission of the royal wedding in 1981 and cabled the Millennium Dome (the work of three called Beckham, Posh and Baby).
How does the cabling work? The ferret wears a harness attached to a long, light nylon line. Once it has threaded the line through a duct, the line is attached to a heavier pull rope to thread the cable. Although there is some training involved – the school has a training area with a range of vertical and split pipes and cul-de-sacs – it is really a case of capitalising on the ferrets’ natural inclination to investigate holes. A bit of salmon oil at the far end of a long pipe as a reward can help them find their way. The furthest one of McKay’s ferrets has travelled is about 250 metres: “We’ve never had one get halfway and decide to come back.”
The school’s business (the delightful collective noun for ferrets) numbers about 50 and McKay usually takes half a dozen along on a job in case someone isn’t in the mood. The hobs (males, which are larger) can pull lines longer distances, while the smaller jills (females) are better at wriggling through the narrowest spaces. Does he have a favourite ferret? “They’re all as good as each other.”
Winemaking ducks and spiders
At the Vergenoegd Löw winery in South Africa, pest control on the vines is the responsibility of a flock of more than 1,000 Indian runner duck “soldiers”. They emerge in a cacophony of honks every morning and spend the day eating aphids, snails and worms, keeping the vines pest-free and healthy. They circulate in a 14-day loop around different areas of the vineyard, with their droppings providing a bonus fertiliser. The ducks take a break only during harvest – grapes are just too tempting – when they get a holiday to swim in a nearby lake, forage on farmland and, er, work on producing the next generation of vineyard soldiers.
Meanwhile, at the R López de Heredia winery in La Rioja, gigantic cobwebs drape the cellar walls and yet more cover the bottles. They aren’t Halloween props or atmospheric decor: they are home to the spiders who help the López de Heredia family keep their barrels and corks free from corkeating moths – “the mortal enemy of long-ageing wine”.
Diagnostic technician and demining rats
The 300 African giant pouched rats employed by the NGO Apopo are multitalented. Not only have they worked on mine clearance in south-east Asia and Africa, but they also sniff out positive tuberculosis sputum samples.
Why are they so good at the job? “They’ve very smart; they’re sociable; they have an excellent sense of smell,” says Lily Shallom of Apopo. “In the past, we’ve found that they can smell a picogram of TNT – a trillionth of a gram.” The rats are “very motivated by food. They like to stuff their cheeks; they have a sweet tooth and they love anything that’s got a really high fat and protein content.” Peanuts and bananas are particular favourites.
The rats signal when they have found a mine by scratching at the surface of the ground. (Weighing a maximum of 1.5kg, the rats are much too light to set off a mine; none have been hurt in the field.) A TB sample, meanwhile, is flagged as potentially positive if a rat hovers over it for three seconds.
It’s a nice life for these highly sociable creatures. Training (which takes nine months on average) or work make up a tiny portion of the rats’ day: mine detection sessions last about 20 minutes, building up to half an hour. Assessing
100 TB samples – the standard batch size – takes a maximum of 20 minutes, but could take a human technician up to four days. The rest of the rats’ day is devoted to free play, hanging out with other rats, snacking and napping.
Apopo is always exploring potential uses for the rats’ special skillset at its training and research centre in Tanzania. Projects include searching for survivors of natural disasters, detecting illegally trafficked pangolin scales and decontaminating land, with the rats deployed to detect specific concentrations of hydrocarbons in soil.
Honey-hunting birds
Humans and greater honeyguides have a genuinely mutualistic relationship: the small, brown-ish African relative of the woodpecker flutters in front of people, tweeting to guide them to bees’ nests in hollow tree trunks. The humans then smoke out the potentially dangerous bees and take the honey. The honeyguide watches and waits until they have finished, then enjoys its preferred food: beeswax.
In 2016, a research team at the University of Cambridge discovered that communication between honeyguides and humans goes both ways. They learned that honey hunters from the Yao community in Mozambique have a better chance of attracting honeyguides, and finding honey, if they use a specific sound: “A loud trill followed by a short grunt: brrr-hmm.” The call increased the overall chance of finding honey from 16% to 54% compared with control sounds. “The