Category Zology

Invasive species

Invasive species are those that get introduced to a new ecosystem, where they end up replacing or affecting the native fauna or flora. These are mostly introduced by humans. Let's read up on a few of the invasive species.

WILD PIGS

The wild pigs are native to Eurasia and parts of North Africa. Also called wild boar or feral hogs, the wild pigs arrived in the 1500s in the U.S. and are one of the most invasive species in North America. They were shipped in by Spanish colonisers as a mobile meat source. Over time, they populated the forests of the southeastern U.S., where their genes got mixed with escaped domestic pigs. They are such a threat as they can live anywhere, eat anything, and have a very high reproductive rate. They destroy crops, landscapes and spread diseases.

MOUNTAIN PINE BEETLE     

A small bark insect, the mountain pine beetle depends on a host tree to feed and lay its eggs. They may seem inconspicuous, with just about one-fourth of an inch in length but they are one of the worst invasive species. They have had a massive impact on the pine forests, boring holes in the tree's bark. They lay eggs in these holes under the bark and deposit a fungus that eventually kills the tree. In fact, in 1995, an outbreak of this pest in the western United States and Canada led to the destruction of millions of acres pine forest.

BURMESE PYTHON

The Burmese python is one of the most concerning invasive species in South Florida where they have established a breeding population. They have even replaced alligators as the apex predator in Florida and have led to the decline of many native species, with the population of small animals dropping at alarming rates. Populations of raccoons, opossums, bobcats, marsh rabbits, cottontail rabbits, and foxes have all been on an alarming decline. These pythons got introduced as a result of the exotic pet trade after they escaped from their owners or got intentionally released into the wild by their owners.

BROWN TREE SNAKE

The brown tree snake was introduced to the Pacific island of Guam in the 1950s. And ever since its introduction, it led to the decimation of the native bird and animal populations on the island. It is believed to have been introduced via cargo ships or aircraft. The snakes which easily spread across the island also cause power outages when they climb electrical wires! Among the 11 native bird species in Guam, nine species went extinct after the snake's introduction.

EUROPEAN STARLING

European starlings are an invasive species in the United States. Interestingly enough, its arrival was the result of a plan to introduce all the species referred to in the works of English playwright William Shakespeare. These birds are native to Europe, Asia and northern Africa but easily took to the landscape of the U.S. and spread quickly across the country, affecting the population of native bird species.

LANTANA CAMARA

One of the worst invasive species in the world, Lantana camara was introduced in India by the British in the 1800s. It came in as an ornamental plant but ended up taking over several ecosystems as an invasive plant. Its ability to spread on the forest floor, climb over trees as a creeper or entangle with other native plants aided it in establishing itself. It continues to spread in India even as methodologies are being adopted to weed it out.

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The science behind pronghorn’s speed

When we think of very fast land animals, the first one that comes to our mind is perhaps the cheetah. Why not? It is the fastest land animal! Do you know which one is the second fastest? The pronghorn. And, the theory behind how it developed such. speed is fascinating. Let's find out more about the animal and its sprinting capacity.

A hoofed mammal, the pronghorn is native to North America, and does not have any close relative anywhere in the world. Healthy populations of the animals exist in their range and are listed under 'Least Concern' in the International Union for Conservation of Nature Red List of Threatened Species. Though it looks a lot like an antelope, the herbivore belongs to its own taxonomic family called Antilocapridae. Pronghorns get their name from the forward-facing projection – the prong on their horns. Interestingly, their ‘horns’ exhibit characteristics of both a horn and an antler. The sheath of its horn is made of keratin, the substance horns are made of. But, these horns are forked and shed every year-just like antlers are! While much can be written about what else is unusual about the pronghorn, its most unique characteristic is its speed.

Running at more than 80 kmph, the pronghorn is the fastest land mammal in its entire natural range- from Canada through the US to Mexico in one aspect, it even gets better than the African cheetah-it can maintain a fast speed for a longer period of time than those carnivores. But the pronghom has no natural predator to match this speed, and so scientists had been stumped by the need for this speed. This is where the science of evolution comes in.

According to a study published recently, during the Ice Age, North America was home to several mammals that no longer exist today. Some of them are well-known today – woolly mammoths, giant sloths, and saber-toothed cats. There were lesser-known ones too, such as ‘Miracinongs’ a cheetah-like cat. The skeletal remains of ‘Miracinonyx’ show that “this now-extinct cat shares the morphological characteristics that indicate high speed capabilities with its African counterpart, the cheetah (Acinony)”. It is a close relative of the puma and the African cheetah. Both puma and ‘Miracinonyx’ are native to North America. Results provide support to "the hypothesis that ‘Miracinonyx’ preyed upon Antilocapra, but not exclusively”. Though it is not seen as conclusive evidence and more study is required, scientists say this "may provide an explanation for why pronghorns are so fast. Maybe they were chased by cheetahs after all".

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Glass frogs have a secret!

Glass frogs live on trees, are active at night, and many of them are difficult to spot because of their green skin that merges well with their environment. “But these amphibians become true masters of camouflage during the day when they’re asleep.” How? Come, let’s find out.

When glass frogs rest or sleep, their muscles and skin turn transparent. So, whats visible are their eyes, bones, and internal organs. It is hard to spot them because they sleep on the bottoms of huge leaves and also blend well with the environment due to their transparency. But, how do they turn transparent, and what about the visibility of blood? Red blood cells absorb green light (the colour of light usually reflected by plants and other vegetation), and reflect red light. This makes blood highly visible, especially against a bright green leaf. In the case of glass frogs, though, something extraordinary happens.

A research team recently “observed that red blood cells seemed to be disappearing from the circulating blood” when the frogs rest. They conducted additional imaging tests on the animals, proving via optical models that the animals were able to achieve transparency because they were pushing red blood cells out of their vessels. It was suspected that the cells were being stored in one of the frog’s inner organs. which are packaged in a reflective membrane.

To find out where exactly the blood was going, scientists used a non-invasive imaging technology called photoacoustic microscopy (PAM). And the result was startling. The primary result is that whenever glass frogs want to be transparent, which is typically when they’re at rest and vulnerable to predation. they filter nearly all the red blood cells out of their blood and hide them in a mirror-coated liver – somehow avoiding creating a huge blood clot in the process.” When the frogs “are awake, stressed or under anaesthesia their circulatory system is full of red blood cells and they are opaque”. This unique capacity would explain why there are hardly any other land-based vertebrates that can achieve such transparency.

Also, in “most animals, pooling blood together leads to clotting which can be life-threatening, for example = leading to heart attacks in humans”. So, studying these amphibians can even help us understand blood clotting better.

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Our connection to other mammals

What makes us humans different from our ape cousins? Well, our brain power. And, that came about through tweaks in the genes, according to an ambitious project, whose results were published recently. Come, let’s find out more about this, and also how we are similar to and different from other mammals.

The Zoonomia Project compared the genomes (the genetic material that makes up a living organism) of 240 mammal species, including humans, to trace evolutionary changes over 100 million years. It studied a wide variety of mammals-from the huge North Pacific right whale (59 feet long) to the tiny bumblebee bat, just 3 cm long. It also included our closest evolutionary relatives – chimpanzees and bonobos. Do you know what startling result the study threw up? “The researchers identified genomic elements- 4,552 in all – that were pretty much the same across all mammals and were identical in at least 235 of the 240 species, including people.” It means that certain parts of genomes have remained unchanged across all mammal species, humans included, over millions of years of evolution.

As for how humans are different from other mammals, the study points to areas “associated with developmental and neurological genes”. It suggests that when Homo sapiens evolved, it involved changes in how the nervous system genes were “regulated”. And these were just tweaks rather than any dramatic and major changes to the genes themselves. This explains why we still share a large part of our genetic makeup with our ape cousins.

And, genes are also responsible for traits unique to some mammals. For instance, hibernation and the sense of smell. While some mammals have a keen sense of smell, others have almost none. Humans are “somewhat average”. The study also saw changes in genetic sequences in some species “in relatively short periods of time”, indicating how they are adapting to their environments.

While the findings are fascinating by themselves. scientists believe they “could inform human therapeutics, critical care and long-distance space flight”, and “also can help identify genetic mutations that lead to disease”.

In a study, researchers identified genomic elements – 4,552 in all-that were pretty much the same across all mammals and were identical in at least 235 of the 240 species, including people. It means that certain parts of genomes have remained unchanged across all mammal species, humans included, over millions of years of evolution.

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Does owls have eyeballs?

Owls don’t have eyeballs. They have eye tubes or cylinders, rod-shaped eyes that do not move in their sockets as eyeballs do. Instead, owls have to move their bodies or heads in order to look around. Since moving their torsos would likely make noise that would alert their prey to their presence, owls have evolved to have necks that can spin up to 270° essentially silently.

But why favour neck-spinning over the seemingly simple eye ball-spinning method of looking around? Well, night vision requires large corneas that allow for light to be collected effectively even in the dark, which is why most nocturnal animals (like the slow loris or tarsier) have huge eyes. But owls have small skulls, so their big eyes couldn’t expand out. They instead developed into the rod shape of today’s owls. They aren’t alone though: some deep-sea fish (like the anglerfish) also have rod-shaped eyes for seeing in the dark.

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Why do epaulette sharks walk on land?

Researchers at a Florida university say a species of shark with the ability to walk on land is evolving to survive warming seas and the climate crisis.

The epaulette shark, found on shallow reefs of Australia and New Guinea, can walk for upto 90 feet on dry land using its paddle-shaped fins, and survive hypoxia (deficiency of oxygen) for up to two hours. The 3 foot long sharks are able to slow and fast walk, as well as swim, giving them an exceptional ability to cross land to reach more favourable environments.

Tide pools and coral reef environments are subjected to warm temperatures when the tide is out. These sharks can move from tide pool to tide pool, allowing them to access new pools to forage for food or tide pools with better oxygenated water.

What sets epaulette sharks apart from other shark species with these abilities, is their tolerance of hypoxia for a prolonged period, and ability to not only survive being on land but walk distances up to 30 times its body length. This gives them better agility to evade predators, reach areas with more plentiful food and less competition for it.

Picture Credit : Google