Invasions and Other Fun Facts

In this video from MinuteEarth, created by Henry Reich et al, you’re going to learn about the invasion of the Yellow Crazy Ants, and other interesting spreading of animals. In the Bonus Facts below, you’re also going to learn a lot of other fun animal facts.  If you like this video, go check them out and subscribe to their channel here. You can also join us in supporting their efforts to make more videos like this by donating via their Patreon page here.

Bonus Facts:

  • How the Yellow Crazy Ant goes about killing the Christmas Island crab is as follows.  As the crabs migrate across the island in extreme numbers, they inevitably disturb an area populated by the crazy ants.  Given these ants are extremely aggressive, they don’t take kindly to this and will spray their formic acid as a defence.  This not only eventually kills the crabs directly sprayed, often blinding them first, but also can kill other crabs as they walk over areas that have been heavily sprayed with the acid.  The ants then are happy to use the red crab as yet another of their food sources.
  • If you’re wondering why rabbits are considered such prolific breeders, it has less to do with them getting it on more than many other animals, necessarily, and more to do with the time frames involved in the process of producing new rabbits.  A baby rabbit becomes sexually mature in an average of just about 5-6 months, and sometimes even sooner.  They can potentially live up to around 10 years.  Further, it takes only around a month from the point of getting pregnant for a female rabbit to give birth.  Their litters can include as many as a dozen rabbits!  What makes this even more astounding is that the female rabbit can get pregnant as soon as the next day after giving birth.  Rabbits are induced ovulators, so the females are pretty much ready to get pregnant anytime they mate (assuming they aren’t already pregnant), with the mating triggering the ovulation.  So even just a single female can give birth to several dozen baby rabbits per year.  Given this, combined with the fact that the babies are ready to make babies at the stage when most human offspring are still mostly just poop and drool factories, you can see how rabbits got this reputation.
  • According to research done at the Rothamsted Experimental Station, depending on soil quality, there can be anywhere from 250,000-1.75 million earthworms per acre of land.  Poor quality soil will have closer to the 250,000 range; good quality soil, such as farm land, will have closer to the 1.75 million worms per acre.  This means that on an average farm with livestock, the weight of the worms beneath the surface of the land will likely outweigh the livestock that walk on top.  What makes this more incredible is that a typical garden variety of earthworm can process about 10 pounds of organic material per worm per year. In the process of doing all this, they process and enrich the soil; they aren’t just nature’s garbage disposals, but also natural gardeners.
  • Earthworms not only work tirelessly throughout their lives cultivating and fertilizing soil for plants to grow, but also form the basis of many food chains.  They are a staple for many types of birds, snakes, moles, hedgehogs, beetles, snails, slugs and also are eaten by a variety of mammals such as foxes, bears, etc. providing essential nutrients to those animals.
  • As you might imagine, it takes a lot of worms to continually cultivate the planet and provide the bases of an awful lot of food chains.  Some varieties of earthworms can live up to 50 years (more typically 1-2 years as it’s a hazardous existence being the bottom of a food chain), with most species having a maximum life span of about 4-8 years.  To compensate for this hazardous existence, they reproduce very quickly, with a freshly hatched worm being ready to breed within about 6-9 weeks of coming out of its cocoon.  They can re-produce about once a month, with one worm being able to produce several offspring in one go.
  • Earthworms MatingNot only this, but earthworms are hermaphrodites.  So when two worms mate, both worms produce children.  The worms mate by getting in more or less a 69 position, exchanging sperm with one another.  Much later, a cocoon is then secreted by the clitellum band, which is visible near the front of the worm.  This is roughly ring shaped.  As it’s sliding out of the secreted ring, the worm deposits its eggs and the other worm’s sperm into the ring.  The ring then seals itself once the worm is completely out.  Eventually, the baby earthworms emerge, lacking only the ability to breed at this point, but otherwise fully developed and ready to go process some soil and be the staple of a lot of animal’s diets.  How long it takes for them to emerge from the cocoon depends completely on the environment.  The cocoon can keep for years without hatching, if the environment isn’t right, or can hatch quite quickly if it’s a nice dry environment.  One cocoon will typically produce 1-5 worms.
  • Earthworms use a gizzard instead of teeth to grind up their food, small rocks, random non-organic garbage, and other materials.
  • Even though earthworms need to breath, they have no lungs.  They acquire oxygen through their skin.  This is why earthworms surface after heavy rains, even though it is extremely hazardous for them to do so.  If they don’t though, they will suffocate and die.  The heavy water content of the soil after rain doesn’t allow gases to diffuse across their skin.
  • Most varieties of earthworms cannot handle direct sunlight for long.  This is for two reason; first, because they can’t allow the mucus on their skin to dry out or they will suffocate; second,  because most also can’t handle direct exposure to UV rays for more than a few minutes to an hour.  If they are exposed to UV light too long, they will become paralyzed and die quite quickly. Earthworms have no eyes, but they can sense light, particularly on their front end.  They use this sense to make sure they avoid light as much as possible.
  • Speaking of invasive species, while earthworms do a bang up job at taking care of soil, they actually do too good of a job in forests.  This can actually, over time, kill the forest.  All the fallen dead leaves and other decomposing vegetation in the forest are essential for many tree seeds to germinate.  The worms process this quickly, leaving the forest floor bare.  This also changes the drainage of the forest, hurting some existing trees.  This is actually a major problem in forests such as in Rhode Island and Minnesota, which had previously been worm free since the ice age; with the arrival of the worm, it is changing the eco-system of these forests.
  • The last Ice Age, where glaciers traveled across North America about 10,000 years ago, also had the negative effect of scraping off most of the top layer of soil.  This killed off the earthworm population in the United States and Canada.  As mentioned in the video, Earthworms were accidentally re-introduced in North America by European settlers.  As the settlers moved west, they brought the worms with them.  In the 200 or so years since North America was fully settled by these worms, they have almost completely populated North America, creating some of the richest soil in the world in the process.

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