This month’s highlights blog features all the best content published in our research journals in July. This month we have: Elephants only signal when you see them, Hummingbird vs. helicopter, It’s in the bee’s genes, Hanging in the balance, City life causes sickness and Ant undertakers remove their dead.
This is just a small selection of the great content we publish every week. For more like this follow us on Twitter or like us on Facebook. You can also search our latest content here. We’d love to hear what you think. Tweet us to let us know!
Elephants only signal when you see them
It seems obvious to us that in order to communicate effectively, your audience needs to be able to receive your signals. So, if those signals are visual, they need to be able to see you. We know that non-human primates also understand this, and will usually only gesture at audiences who are watching them. This has now been proven for elephants too. Published in Biology Letters in July, new research shows that elephants can also infer visual attentiveness of their audience from body and head positioning. The elephants signalled for food significantly more often if the experimenter’s head was facing the elephant and she was therefore able to see the elephant’s signals.
The average hummingbird wing and the world’s most advanced micro helicopter rotor are remarkably similar. A recent paper published in The Journal of Royal Society Interface compared the aerodynamic performance of 26 wings from 12 hummingbird species to an advanced micro-drone (called the Black Hornet, used in battlefield surveillance) and found that, on average, hummingbird wings were equally as efficient. More slender wings, however, improved efficiency, and the best hummingbird wings (Calypte anna) outperformed the blades of the micro-helicopter by over 20%. This finding suggests that improvements to the performance of engineered micro-rotors could be modeled on the biomechanics of the hummingbird wing.
It’s in the bees genes
In the familiar Western honey bee, differential feeding with a potent diet known as royal jelly creates two contrasting types of females, highly reproductive and long-lived queens and short-lived sterile workers. This specialised nutrition affects a particular chemical modification known as methylation, of the bee’s DNA, causing the same genome to be deployed differently.
The in-depth study published in Open Biology shows that the bee’s cellular machinery includes an enzyme, thus far only described in mammals, that has the capacity to remove methyl marks. The novel findings explain how the dynamics of DNA methylation and de-methylation are regulated to influence global gene expression required for generating a different organism for the same genome.
Traditionally arm scales or spring balances have been used to measure weight. A paper in Proceedings A proposes a new type of scale with flexible arms exploiting the effects of partial frictionless confinement on the equilibria of elastic rods. The authors demonstrate that an elastic rod placed within a tube will adjust itself, by sliding along the sleeve, in order to balance two different end loads and can be used with or without a counterweight. Furthermore, a sensitivity analysis as well as the experiments performed on the prototypes indicate that the deformable arm balance works correctly and that it can perform better than traditional balances in certain load ranges.
City life causes sickness
Some of the poorest neighborhoods may be protected from Chagas disease. A new Proceedings B paper shows that along a transect of the city of Arequipa, Peru, the insects that transmit Trypanosoma cruzi, the parasitic agent of the disease, were common in established communities, but absent from those in which residents do not hold title to the land on which they reside. The increased land tenure security in established neighborhoods may lead residents to bring more animals into their homes, inadvertently creating conditions favorable to zoonotic diseases. Land invasions, in which residents live in fear of eviction, may not contain enough suitable habitats to maintain vector populations.
Exposure to pathogens is a significant hazard for populations living in high densities, particularly when individuals within the population are closely related, as is the case for social insects. Many social insects have been documented to participate in specific hygienic behaviours associated with social immunity and the reduction of pathogen exposure. For example, many social insects dispose of corpses, either through removal from the nest or burying. This prophylactic behaviour has been believed to decrease disease and therefore reduce the necessity for costly individual immunity. Published in Biology Letters last month, Diez et al show for the first time in an experimental setting that necrophoresis (removal of bodies from the nest) has a direct effect on brood survival rates, with nests which were prevented from removing corpses exhibiting reduced survival.