ANIMAL NEWS
Hermit crabs turn plastic pollution to good use, plus a tortoise murder mystery
Szulkin’s study found a total of 386 individuals using human junk as shells
SHELL SHOCK
Marine creatures are making use of human pollution in creative ways. Two-thirds of hermit crab species have been found using debris that humans have discarded as ‘artificial shells’, instead of those left behind by molluscs.
In a study of hermit crab residences using photos taken by tourists and posted on social media and photosharing websites, Marta Szulkin, an urban ecologist from the University of Warsaw, explained, “We started to notice something completely out of the ordinary… Instead of being adorned with a beautiful snail shell, which is what we’re used to seeing – they would have a red plastic bottle cap on their back or piece of light bulb.”
Szulkin’s study found a total of 386 individuals using human junk as shells – mainly plastic caps. “According to our calculations, 10 out of the 16 species of land hermit crabs in the world use this type of shelter and it’s been observed in all tropical regions of the Earth,” she said. It is not clear whether using human debris as shells is harmful to the animals, and it may be helping them. As natural snail shells are in decline, it is possible that it might be becoming easier for the animals to find an artificial alternative, and the lighter, plastic ‘shells’ might even help smaller, weaker crabs to survive because they are easier to carry. standard.co.uk, 27 Jan 2019; BBC News, 26 Jan 2024.
DEVON TORTOISE APOCALYPSE
National Trust staff at their Ashclyst Forest property near Exeter in Devon were reported to be “horrified” after discovering nine dead giant tortoises in their woodland. Two turned up on 8 January, then another five on 12 January, and two more in early February. The dead reptiles were identified as Aldabra giant tortoises, an endangered species found in the Galapagos Islands that can live up to 150 years and reach 1m (3.2ft) in length, making them one of the largest tortoise species in the world. They are not usually kept in captivity in the UK due to their challenging environmental and dietary needs, although there are a few in wildlife parks and private collections. None of the known owners, however, reported any animals missing. Police could find no immediate leads and said, “We would like to hear from anyone who has recently purchased a giant tortoise in the area or knows of anyone who normally has a large number of tortoises but has fewer now,” and appealed to the public for further information.
As part of the investigation, vets planned to carry out autopsies on the dead reptiles to establish a cause of death and police were working with the RSPCA Wildlife Crimes Unit to try and find who was responsible. They suspect wildlife smugglers, but are baffled as to why they should be dealing in such
large, difficult, and conspicuous creatures for which there seems to be no obvious demand. Police later interviewed a man in relation to the incident, but no charges were brought, so how and why so many giant tortoises ended up dead in a Devon wood remains a mystery.
However, it is not the first time, though, that bizarre animal corpses have made an inexplicable appearance in the UK: in 1981 the headless skinned corpses of two 6ft (1.8m) bears were found floating in a canal in Hackney (FT37:45, 200:30) in an incident that has never been adequately explained. BBC News, 17 Jan; devonlive.com, independent. co.uk, 8 Feb 2024.
SERIOUS CICADAS
Cicadas are tree dwelling insects about two inches (5cm) long that spend almost all their lives as larvae among the roots of trees, only emerging periodically in great numbers to mate and then die. They do so at intervals based on prime numbers, believed to have evolved to make it difficult for predators to match their breeding cycles. There are different “broods” of cicada found across the US, named with Roman numerals, based on their year of emergence and their location. Broods I to XVII are 17-year cicadas, while XVIII to XXX follow a13-year cycle. At each brood emergence, billions, and possibly trillions, of cicadas appear, and the males make a strident buzzing sound to attract mates; with such huge numbers of insects, this can be louder than a jet engine. After having spent so long underground, adults live just four weeks, and, according to the University of Illinois Urbana-Champaign, a 1990 cicada emergence resulted in “people in Chicago having to use snow shovels to clear their sidewalks of the dead cicadas”.
April 2024 will see the simultaneous emergence of Brood XIX, the Great Southern Brood, and Brood XIII, known as the Northern Illinois Brood. These occupy adjacent territories, and it is the first time that their respective 13- and 17-year cycles have coincided since 1803. It will be another 221 years before they coincide again. “Nobody alive today will see it happen again,” said Floyd W Shockley from the Smithsonian National Museum of Natural History. “That’s really rather humbling.”
Shockley estimates that the 16 states covered by the two broods will see more than one trillion cicadas emerge, which, if laid end to end “would reach to the Moon and back 33 times.” Given that the two broods live adjacent to each other, Shockley says that: “Under just the right circumstances and with just the right number of individuals cross breeding, you have the possibility of the creation of a new brood set to a new cycle. This is an extremely rare event.” For the appearance of Brood X in 2021, see FT408:5. dnyuz.com, 19 Jan 2024.
SNAKE KNOBBLED
A rat snake found in Maryland is being nursed back to health by the Second Chance Wildlife Centre in Gaithersburg, having been found with a gear stick knob stuck in its gut. Rat snakes love chicken eggs and will go for anything that is remotely eggshaped, often being found with golf balls in their guts. In this case it was a two-inch diameter cue ball-like gear stick knob, which appears to have come from something like a tractor. As these objects cannot be digested, they block the snake’s gut and are inevitably fatal unless surgically removed. In this case the snake had managed to survive so long with the knob in its gut that it had worn a hole through the snake’s skin. Second Chance removed the knob and stitched the snake up, after which it made a full recovery. They are keeping it at the centre over winter and plan to release the now-healthy snake back into the wild in the spring. thedrive.com, 29 Jan 2024.