Dear Readers, before we finally say goodbye to 2020, here are a few final stories from New Scientist that caught my eye.
The first is pandemic-related, as nearly everything seems to be at the moment. White-crowned sparrows (Zonotrichia leucphrys) were found to be singing differently during the Covid lockdown in San Francisco, and scientist Elizabeth Derryberry, from the University of Tennessee, wondered how, and why.
The birds were found to be singing more quietly and at a deeper pitch – it’s known that birds react to the low-frequency background drone of traffic and air conditioners by singing not only louder, but at a higher frequency so that they can be heard over the racket. The noise level in San Francisco had dropped by a full 7 decibels, and so the birds seem to have reverted to their older, sexier songs – birds actually seem to prefer deeper sounds (think Barry White as opposed to Tiny Tim). If you go to the full article here, you can hear both birdsongs. The scientist says that ‘they sing like they used to thirty years ago’. I suppose this is both sad, but also hopeful – birds and other urban animals seem to be so much more adaptable than we thought.
But not all animals are able to adapt. The prehistoric cave bears (Ursus spelaeus) that used to weigh over 1000 kilograms, and existed alongside our present-day brown bears (Ursus arctos), probably became extinct because they had over-large sinuses. Who knew? These huge animals, who disappeared about 24,000 years ago, lived on a largely plant-based diet. When the ice-ages made vegetation difficult to come by, the cave bears couldn’t switch to a meat-based diet, because their sinuses meant that they could only chew food with their back teeth, while carnivores typically cut up their food with their incisors and canines at the front. The brown bears had smaller sinuses, and hence could switch from a herbivorous to a carnivorous diet.
But why have such big sinuses in the first place? They are thought to play an important role in gas-exchange during hibernation, allowing the bears to hibernate for longer. However, as the poor cave bears wouldn’t have been able to fatten up due to the lack of plant food, they probably starved while they were sleeping. It was one of those evolutionary trade-offs that failed.
You can read the whole article here.
Hagfish are extraordinary animals. Early ancestors of the eel, they have four times as much blood compared to their volume as any other fish, four hearts and only half a jaw. When trapped by a predator or accidentally stuck in a tight spot, they throw complex knots and shapes in an attempt to escape. Because this is a very slippery fast-moving process, it’s taken modern technology and a slow-motion camera to decipher what’s going on. Now, scientist Theodore Uyeno has discovered that the animals prefer more complex knots – the hypothesis is that the simpler ones may be more uncomfortable because the loops are so tight.
So, 45 percent of the time the hagfish do a trefoil knot:
33% of the time they do a figure-of-eight knot…
and 4% of the time they manage a three-twist knot, the only animal able to do so (Moray eels can knock up a knot, but nothing this complicated). Kompologists rejoice!
And finally, how about this little creature with its ‘hats’?
Each ‘hat’ is the moulted skin of the caterpillar’s head – they moult up to thirteen times before they metamorphose into moths, and from the fourth moult on, each ‘hat’ stays stuck. You can see how the size of the head gets bigger from the top down, as the larva munches on eucalyptus leaves: an alternative name is the ‘gumleaf skeletoniser’ because the foliage is eaten right back to the veins.
The ‘hats’ seem to fulfil a useful purpose: biologists have watched the caterpillar using them to swat away predators, and they may also serve to distract a curious bird who will hopefully peck at the wrong ‘head’. You can read the whole article here.
And so, dear readers, onwards and into 2021. Who knows what those scientists will discover next?
Photo One by Gerry Matthews (Alamy) from https://www.newscientist.com/article/2255352-coronavirus-lockdown-changed-how-birds-sing-in-san-francisco/
Photo Two By Ra’ike (see also: de:Benutzer:Ra’ike) – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=4540111
Photo Four By Jim.belkAnimation: MichaelFrey (talk) – Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=75360346
Photo Five By Lucasbosch – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=17249329
Photo Six by Original: Jim.belk Animation: MichaelFrey, CC0, via Wikimedia Commons
Photo Seven by Alan Henderson at Cover Images. Photo from https://www.newscientist.com/article/mg24632881-200-weird-caterpillar-uses-its-old-heads-to-make-an-elaborate-hat/