Swarms!

In keeping with my October theme of creepy critters, I’m bringing you swarms. The sheer number of swarming animals is not just creepy, it’s deeply unsettling for most people. The feeling is such a profound part of the human psyche that swarms even surface in religious teachings – there are the biblical plagues in the Old Testament and the Miracle of the Gulls in Mormonism.

Swarming can be found throughout the animal world, among all types of creatures in the air, on land, and in the sea. The reason behind much of this behavior is still a mystery, but scientists have figured out why some occur. One strong impetus for swarms is the search for food. This is the case for the largest swarms on earth, locusts, and for the daily swarms of bats as they leave their caves in search of food. In the ocean, swarms of sardines and krill will trigger other swarms of animals seeking to feed on them. Swarms born of swarms. Despite drawing predatory attention, animals of all kinds swarm for protection from predators. While some members of the swarm may be picked off, the individual still has an improved chance for survival in a large group. This is the old “safety in numbers” logic. Swarms can be also created by climate, seasonal, or environmental changes. We see this in migratory patterns or the simple business of moving to a new house (which causes swarming in bees and ants). Lastly, swarms are set off by the biological imperative to reproduce. In virtually every part of the natural world there are animals seeking love in large groups.

The effects of swarms are mostly confined to the animals involved, with some important exceptions. Locusts, for instance, cause massive destruction to the environment and decimate food resources wherever they go. Last year (2020) residents of East Africa were beset by a massive swarm that spanned nearly 930 square miles and contained an estimated 200 billion insects. By far the largest swarms on earth, locust swarms have the ability to drastically alter life wherever they go. According to this article, the conditions that locusts need to thrive (dry weather followed by torrential rain) is becoming more common due to climate change. Also, swarming locusts are biologically compelled to reproduce faster and eat more while swarming. So, there’s every reason to believe that these swarms will only continue to grow in frequency and size. Which could become a hazard for life worldwide. Luckily, there are smart people working hard on solutions, including this one that turns locusts into animal feed. 

If you read my centipede blog, you know how I feel about centipedes and millipedes (not a fan of those squirmy legs), so millipede swarms are super-duper creepy to me. Apparently driven by an irresistible food source, millipedes in Senegal pile on top of each other to get at it (see the video here). In Japan, millipedes swarm in large enough numbers to stop train traffic. Scientists have now determined that these poisonous creatures are part of a brood cycle that emerges every eight years, similar to the life cycle of cicada.

One of the most incredible swarms on the planet is the march of the Red Crabs of Christmas Island. This small island is off the northwest coast of Australia and has a population of 2,000. People, that is. Its crab population is 40,000,000. Every year at this time (October-November), the crabs march from their homes in the forest down to the beach for a festival of breeding and nothing stops them. Their relentless march is annoying and messy (especially when thousands lie dead on roadways), but Christmas Island inhabitants have learned how to live with them. Among other concessions to the crabs, they’ve built tunnels under roadways for the crabs to use. For more on this cool phenomenon, including what invasive species is threatening it, check out this article. 

Speaking of crabs, if you who don’t like swimming in the ocean because you don’t know what’s underneath you, you should not look at the video of this next swarm. While researching something else entirely off the coast of Panama, scientists discovered a massive swarm of Tuna Crabs moving along the bottom. According to this video, they say there are thousands of crabs in the horde, but it looks like zillions to me. Cool…and creepy.

Right up the coast from the Tuna Crab swarm is Costa Rica, home to large populations of Olive Ridley Sea Turtles. In the Ostional National Wildlife Refuge females of this species swarm the beach to lay their eggs. Their swarm is known as a mass arrival and happens every month. In November 2016 biologist, Vanessa Bézy captured something special on her drone camera – a swarm of hundreds of thousands of turtles; the largest swarm ever filmed. Why there were so many remains a mystery, but it is a spectacular sight. Protecting these turtles continues to be a high priority to environmentalists. Learn more (and see the amazing video) from National Geographic.

Most people would consider fruit flies to be annoying but otherwise unremarkable. But, as it turns out, those little fliers carry big secrets. It seems they are into free love and they swarm to get in on the action. Their urge to reproduce turns them into sex-crazed, orgy-loving little beasties. According to this article, their initial one-on-one heterosexual coupling escalates into an extended session of group sex. There’s more, but I’ll be discreet and let you read it for yourself. 

Monarch butterflies create epic and beautiful swarms as they migrate to and from their winter homes in the mountains of Mexico. Much of their travels are still a mystery, but we do know that they number in the millions (150,000,000 or more) once they arrive. Here is a video done by National Geographic using a fake hummingbird camera to get up close without disturbing them. It’s amazing. And, this video, lets you hear how sounds there. 

And then there are the spider swarms. And for many people, these are the creepiest of all. In the fall months here in the Southwest, male tarantulas leave their burrows and take to the roads in search of lady tarantulas. They number in the hundreds, and even thousands, as they venture out (here’s more from Marfa, Texas). While the tarantulas we see in our country are generally harmless to people, there are others that are more problematic. Case in point: Australian Diving Tarantulas (yes, they go underwater). These guys have a particularly strong venom that can severely sicken a person. And, in 2015 (for reasons unknown), roughly 25,000 of these spiders swarmed the little town of Maningrada, Australia. That must have been a very scary scene, even for the bravest of spider-lovers.  Another truly frightening spider swarm happed in 2011 in Pakistan and, to be honest, this is where my love of nature crashes right into my tapped-down arachnophobia. That year, after unprecedented flooding, the arachnid population moved to high ground. Specifically, into trees. Once there, they set up house and spun webs. Tree after tree was covered in webs in which millions of 2-inch spiders lived. Altogether too much for me. 

Here’s wishing you a happy, creepy Halloween… and if you come across a swarm, get out of the way. 

Submitted by Pam

Centipedes Creep Me Out

I live in a place where rattlesnakes, scorpions and tarantulas are common, and they do not bother me at all. But the other day I came across a centipede and that triggered some kind of primeval revulsion in me. They always do - it’s all those little legs and all that squirming around…..I just can’t. I know I’m not alone in this (here are some interesting thoughts as to just why we find them so gross), so I really don’t understand how these arthropods have managed to avoid being part of Halloween lore of creepy creatures. I‘m adding them to my list for sure. So, in celebration of their Halloween, here’s a little something about these creepy crawlers.

First of all, there are centipedes and there are millipedes, and while they are both pretty yucky, they have some interesting differences. As their names imply, centipedes have fewer legs than millipedes – one per body segment as opposed to two. Although millipedes have twice as many legs, they are slow-moving burrowers, while centipedes scurry around rapidly. This difference in their movements is down to centipedes being carnivorous and predatory while millipedes feed on decaying organic matter and roots in soil. Millipedes are generally considered beneficial creatures (albeit still creepy), while centipedes are the ones who have venom and can (and will) bite. For more on their differences, check out this article. 

Let’s talk about those legs: First of all,  the word “centipede” would indicate one hundred legs with that the root word of “cent” while “millipede” would indicate one thousand, but that is not accurate. According to this article, centipedes have up to 382, while millipedes have between 40 and 400. Also, they don’t start out with all they end up with – they grow additional legs as they mature. And they can drop a leg to escape a predator (like some lizards do with their tails) and grow it back later. They have an abundance of legs, but they actually use different ones for specific purposes. For instance, centipedes carry their venom in the two legs right by their heads (these forcipules are legs and fangs all in one and are unique to centipedes). They jump on their prey and insert the venom while using some of their legs to completely encircle their victim. Meanwhile, other legs are maintaining their grip on whatever surface the centipedes are hunting from.

Often the creepiest things about the animal world are the mating rituals therein (and, yes, I include humans in this statement), and centipedes are no exception. Except that it appears their genders don’t even want to be near each other; they have developed reproduction without copulation. In most centipede species, males create a web that they deposit their sperm in, after which  females get into it and absorb the sperm to fertilize their eggs. Depending on the species, the females then either deposit their eggs in the ground and leave or stick around to care for and protect their offspring.

There are somewhere around 3,300 species of centipedes in the world, and they come in an array of colors and sizes. Centipedes are generally black or dark, reddish-brown with yellow legs, but they can also be orange, blue, yellow or purple in parts (check out this Google search to see some of them). If they weren’t so darn creepy, some varieties could be considered pretty (and probably are by people more tolerant than I).

One of the most common varieties of centipedes is the House Centipede. These guys are small, look like a combination between a spider and a centipede, and are often found lurking in drains. If you come across one don't kill it; it's busy hunting insects that you really don't want in your house like roaches, flies and termites. While House Centipedes are pretty common, on the other end of the centipede spectrum is the uncommon Waterfall Centipede (Scolopendra cataracta). These natives of Southeast Asia were not even discovered by scientists until 2001. Despite their large size (about 8 inches), they stayed off the radar because they prefer to hide and hunt in and under water - especially around waterfalls. These elusive centipedes can run along the bottom underwater, which is definitely creepy. Here's more on them. 

If small centipedes can cause visceral reactions, large ones are the stuff of nightmares. And they can
get really big. The winner for being the largest is the Peruvian Giant Yellow-Leg Centipede 
(Scolopendra gigantea). This intimidating creature can grow as long as 12 inches and can easily take down prey more than fifteen times its size. These guys seem to be fearless (which makes them even more intimidating) – scientists have observed them hanging from ceilings in caves while feasting on bats. These centipedes are native to South America and the Caribbean, but they have been introduced to the world at large for the pet trade. Needless to say, keeping these large venomous animals is not a great idea. When it comes to centipedes this large, the bite can not only cause all sorts of problems, it can also be fatal. For more on keeping centipedes (including the pertinent warnings), check out this article. And if you want to see a man (unwisely) handling a ginormous centipede, here’s a video. 

One more thing: Even if you find centipedes as creepy as I do, please don’t kill them just because you don’t like the way they look. They have their spot in the ecosystem and have the right to live happy centipede lives.

Take Care.

Submitted by Pam