Birds can sing louder at higher frequencies to make themselves heard over traffic noise

Animals have developed a variety of strategies for dealing with increasing noise pollution in their habitats. It is known, for example, that many urban birds sing at a high pitch to differentiate their song from the low-frequency sound of road traffic. However, as scientists discovered, this is just a useful side effect. The real reason for this behaviour is that songs at a higher pitch are also automatically louder. The birds can make themselves heard far better in city noise by increasing the volume of their song than by raising its frequency according to Science daily.

Despite the numerous unfavourable environmental conditions they encounter there, many wild animals have colonised cities as a new habitat. In cities they must deal with greater numbers of humans and with more light and noise pollution than they encounter in rural settings. However, the urban habitat also offers certain advantages, for example a more abundant supply of food and new breeding options. Many animals have thus adapted surprisingly well to city life.

Trees recognize roe deer by saliva

In spring, the young, delicate shoots in the forest light up, bright and May green. The buds and shoots are the future of the forests as they allow young trees to grow. The problem for the trees is: Roe deer like to eat them, and especially their buds. With a bit of luck, the young, gnawed saplings will only take a few more years to grow than their non-bitten conspecifics. In the worst case, they will become stunted trees, or they will have to give up their fight for survival after a number of years. In this respect, roe deer can cause a great deal of damage and hinder the regeneration of many deciduous tree species according to Science daily.

In order to protect themselves against roe deer browsing, trees purposely put up a fight. By studying young beeches (Fagus sylvatica) and maples (Acer pseudoplatanus), biologists have now found out that trees are able to recognise precisely whether a branch or bud has been purposefully nibbled off by a roe deer -- or just randomly torn off by a storm or other mechanical disturbance. The saliva of the animals gives them the signal. If a deer feeds on a tree and leaves its saliva behind, the tree will increase its production of salicylic acid. This hormone, in turn, signals to the plant to increase the production of specific tannins. It is known for some of these substances that they influence the feeding behaviour of roe deer, with the result that the deer lose their appetite for the shoots and buds. In addition, the saplings increase their concentrations of other plant hormones, growth hormones in particular. These hormones enhance the growth of the remaining buds to compensate for the lost ones.

Research confirms how global warming links to carbon emissions

Research has identified, for the first time, how global warming is related to the amount of carbon emitted.

A team of researchers have derived the first theoretical equation to demonstrate that global warming is a direct result of the build-up of carbon emissions since the late 1800s when human-made carbon emissions began. The results are in accord with previous data from climate models.

The theoretical equation reveals the complex relationship between carbon dioxide levels and the ocean system. Burning fossil fuels increases atmospheric carbon dioxide levels leading to global warming and the greenhouse effect, which is partly offset by the oceans taking in both heat and carbon.

More to rainbows than meets the eye?

In-depth review charts the scientific understanding of rainbows and highlights the many practical applications of this fascinating interaction between light, liquid and gas.

There's more to rainbows than meets the eye. Knowledge gained from studying these multicoloured arcs of scattered light can be incredibly useful in ways that may not immediately spring to mind. Rainbow effects can warn of chemical contamination in the atmosphere, help to develop more efficient combustion engines and possibly even provide insight into the mechanics of reinforced concrete.

The pot plants that could clean up the air in your home

They brighten up our homes and cheer up our offices. But house plants also clean up the air that we breathe.

Research has shown that popular pot plants also absorb dangerous chemicals, leaving the air cleaner for us to breathe.

One of the best ‘natural air fresheners’ is Guzmania lingulata, or the scarlet star, a colourful and tropical type of bromeliad which blooms for months indoors.

Others include the corn plant (Dracaena fragrans) which boasts long, variegated leaves that are particularly good at mopping up acetone, the pungent chemical in nail varnish remover.

The work comes amid mounting concern about the damage done by indoor air pollution, including toxins called volatile organic compounds, or VOCs, which released by everything from paint and printers to cleaning chemicals and dry-cleaned clothes.