Squirrels can survive a fall from any height, at least hypothetically (McGill OSS)

1 minute read

Squirrels, in theory, can survive a fall from an object of any height due to two factors: their size and their mass. A force (such as the force of gravity) is calculated by multiplying mass and acceleration. The acceleration due to gravity on Earth is always roughly 9.81 m/s2, regardless of what object it is acting on. Squirrels are not very heavy—a grey squirrel only weighs about 0.5 kg—meaning that the force acting on a falling squirrel just isn’t that big.

Force = mass*acceleration = 0.5 kg * 9.81 m/s2 = 4.9 N

We measure forces in a unit called “Newtons”, named for Isaac Newton who gave us Newton’s three laws of motion.

Compare this to, for example, a falling 60 kg human, which would be pulled downward with a force of about 489 N. A factor of 100 higher!

On top of being small, squirrels are fluffy and intuitively spread their bodies out when falling. This allows them to experience as much wind resistance as possible, slowing down their rate of descent. Some squirrels even use this fact to glide through the air. While gliding is not the same as flight, we nonetheless call them flying squirrels.

For these two reasons, the terminal velocity (fastest speed while falling) of squirrels is slow enough that they will, at least in principle, never fall so hard that they hurt themselves.

This article was originally posted here: https://www.mcgill.ca/oss/article/did-you-know/squirrels-can-survive-fall-any-height-least-hypothetically

Advertisement

The Epidemic Facing Ash Trees (McGill OSS)

6 minute read

The Emerald Ash Borer (EAB) is a species of jewel beetle native to eastern Asia. In 2002, the beetle was detected for the first time in North America. First in Michigan, then Ontario, although tree ring analysis suggests that it has likely been present in those regions since the early 1990s. Since then, the number of EABs have increased year after year as the bugs spread across Ontario, Quebec and more than half the continental U.S.

An infection of EABs can kill an otherwise healthy ash in 2-5 years. But how can an 8.5 mm long insect kill a tree anyways? One way would be by eating all of its leaves. Without foliage, a tree has no way to photosynthesize, and therefore no way to make energy. Adult EABs do munch on leaves—a loss of tree canopy is a warning sign of EAB infestation—but not usually to the degree that would kill an ash. Instead, it’s the EAB larva that cause the majority of the damage.

EAB eggs are laid on ash branches, and larvae, once hatched, chomp their way under the bark. The little grubs will chew out 6 mm wide S-shaped tunnels called galleries to live in that can be up to 30 cm long. These galleries disrupt a tree’s internal water transport system, taking away its ability to send necessary nutrients up to its branches and leaves. As a result of nutrient deficiency, EAB-infected ash trees often show signs of chlorosis, or a lack of green colour in their uppermost leaves. Dying ash trees will sometimes send out epicormic shoots—little sprouts from the roots or lower trunk and branches—in an attempt to survive.

Most EABs spend winter inside ashes in their larval form. They’re able to withstand temperatures down to -30 ˚C, and are partially insulated by the tree bark. Eventually, come spring, the fully matured beetles will emerge from the ash trees, leaving small capital D-shaped exit holes about 4 mm wide.

The loss of one type of tree might not seem like such a cause for alarm, but the widespread death of ash trees is having many repercussions. In 2015, Montreal was home to roughly 200,000 ash trees. Mont Royal, the iconic park in the centre of the island was, until recently, home to over 10,000 of those trees. But, as a result of the EAB infestation the City of Montreal was forced to cut down about one-third of those ashes. The other two-thirds they chose to treat with preventative insecticides. To make up for the over 3000 lost trees, the city will plant 40,000 saplings. Of these, about 50% are expected to thrive. In 2016 Montreal committed $18 million to fighting the EAB and replacing the ashes it kills. In the U.S., affected states spend an average of $29.5 million per year to manage EAB populations.

The loss of ash trees can impede ecosystems, bring down home values or disrupt food webs. During bad weather, sick or dying ashes can pose a safety risk if they fall or drop branches. And with the loss of these trees comes an increased risk of landslides and flooding, both of which tree roots help to prevent.

Read the entire article for free by clicking here- https://www.mcgill.ca/oss/article/epidemic-facing-ash-trees

Queen Ants Don’t Have a Divine Right to Their Thrones, Just the Right Genetics

Originally posted here: https://mcgill.ca/oss/article/did-you-know/queen-ants-dont-have-divine-right-their-thrones-just-right-genetics

Humans have classified more than 12,500 species of ants, and there are an estimated 10,000 more waiting to be discovered. Besides their incredible strength, almost all of these species have something in common: queens. 

Ants adhere to a caste system, and at the top is the queen. She’s born with wings and referred to as a princess until she takes part in the nuptial flight, mates with a male ant, and flies off to start her own colony. Since she retains the sperm from this first mating for her entire life, she never needs to mate again,and can digest her wings to nourish herself until her colony is established.

Queens selectively fertilizethe eggs they lay. Fertilized eggs become infertile female worker ants (the larger of whom are referred to as soldiers) and unfertilized eggs become fertile males, called drones. The males exist just to mate with the queen ants and die soon after.

How new princesses are made though has always been somewhat of a mystery. It’s been well established that, when fertilized eggs and the resulting pupae are better nourished, they develop into princesses, but how ants can develop into the two hugely different groups of workers and queens just by being fed more was a conundrum. Until now.

American researchers have found that some pupae are born with a particular gene, insulin-like peptide 2 (ILP2), expressed a lot, while others are born with it barely expressed at all. This causes some pupae to have more of the insulin-like protein in their bodies (which functions much like normal insulin, to allow glucose to be absorbed from the blood), and thus absorb more nutrients.

While in their larval form, all pupae are actually sent signals to suppress ILP2. This way, it’s only the ants born with naturally high ILP2 expression that areable to reproduce. These reproduction-destined ants will be better fed by the workers and will eventually develop into queens. In times of stress, like droughts or when food supplies are low, ants will choose not to feed fertilized eggs better, thus stopping the queen-development process and saving resources for the colony.

So with antsit seems the key to the kingdom isn’t as easy as marrying a prince. You’ve got to be born at the right time, with the right gene expression, in the right place.