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For some reason, this year we have fewer hummingbirds at our feeders. In recent years, we would have twenty or more hummers buzzing around the feeders on our deck at any given time. This year, only two or three at a time. No idea why. The ruby-throated hummingbird is the only species that breeds east of the Rocky Mountains, so it is the only type we've ever seen at our house. A few other hummingbirds (like the rufous hummingbird) occasionally migrate through Missouri but do not breed here. Here's a male ruby-throated hummingbird I photographed a few days ago. Males have a dark chin that appears ruby-red when the sunlight hits it just right. Ruby-throated hummingbirds weigh, on average, only 0.15 ounce (about 4 grams... less than the weight of a nickel), with a wingspan of about 3.5 inches (9 cm). A hummingbird's pectoral muscles make up almost a third of the bird's weight. These muscles provide the power needed to beat their wings fifty-three times every second. In my view, this makes them superhero birds. This rapid wingbeat sounds kind of like humming, which is how hummingbirds got their name. But the humming sound is more than just the rapid wingbeat. Hummingbird wings are different from other those of other birds in the way they are anchored to the shoulders. Hummingbird wings move more like sculls in a rowing boat, with a rotating motion that allows the bird to fly forward, backwards, and sideways. They can even fly upside down. Anyway, this rotation movement of the wings helps create the humming sound. Astoundingly, a ruby-throated hummingbird's heart beats more than 1,200 times per minute. For comparison, a human heart beats about seventy times per minute. And finally, to further illustrate how mighty these tiny birds are, ruby-throated hummingbirds migrate from all over the eastern half of North America all the way to Mexico and central America... and back. Sometimes over 2,000 miles each way. Amazingly, when they fly over the Gulf of Mexico, they fly as far as 600 miles without stopping. Obviously, they have to bulk up on sugar before a nonstop flight like this. And during hurricane season, this can be a treacherous route.  Photo Credit: Ruby-throated hummingbird - Stan C. Smith
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Last night, Trish and I watched Furiosa: A Mad Max Saga (yes, it’s insanely fun—with emphasis on insane). In the movie is a scene where Dr. Dementus tastes the tears of a victim, and he waxes eloquent about the superb chemical qualities of tears of sorrow compared to other tears. And I’ve recently seen memes about this on social media. Is there truth to this? Let’s take a look. First, we have to consider why humans shed tears. There are three kinds of tears: BASAL TEARS are constantly secreted to moisten and protect your cornea. REFLEX TEARS wash away irritants or foreign matter (like when you cut onions). EMOTIONAL TEARS form when we experience sorrow, joy, or pain. Interestingly, most researchers agree that emotional tears are unique to humans. But are emotional tears really chemically different from reflex tears? As it turns out, they are. Emotional tears contain various hormones (like stress hormones), as well as various proteins not found in basal tears and reflex tears. The question is, WHY? It all has to do with human social behavior. While basal and reflex tears serve biological functions, emotional tears serve social functions. Before we understood the social importance of crying, Charles Darwin once declared that emotional tears were “purposeless” because they didn’t seem to serve a biological function. More recent behavioral research, however, has revealed much about emotional crying. Research on crying at the University of Pittsburgh has revealed that people are more likely to feel better after crying if they receive social support during their crying. The idea is that tears are a visual signal to others that we need emotional support. And, in fact, it may be that the extra proteins in emotional tears help to slow the tears as they flow down our cheeks, thus making the visual signal last longer so that other caring people notice our need for comfort. An awesome reminder that humans are, at our very core, social animals.  In April, Trish and I spent some time on the Pacific coast of Washington state. At one particular stop, I noticed a man playing with his dog on the beach, and I captured a fun photo. Later, as I stared at the photo, I realized the man had a special throwing handle, which allowed him to throw a ball farther and throw it repeatedly without undue stress on his arm. The key word here is "repeatedly." Because we all know some dogs seem to never get tired of fetching a ball. So, I wondered, why do dogs love fetching balls (or other objects) so much? Let's dig into this. First, there is the obvious: Dogs like to please people and interact with people, and playing a game like fetch accomplishes both. And, of course, dogs like to run. But there's a much deeper motivation involved. As I've discussed in previous emails, all domestic dogs come from a common ancestor that was also an ancestor of the gray wolf. Like the wolves of today, this ancestor was a predator. So, domestic dogs evolved from a successful, efficient predator. A killing machine, if you will. This ancestor had a strong prey drive (the instinctive drive for carnivores to pursue and capture prey). Today's domestic dogs still retain some of this prey drive, though humans have bred portions of this instinct out of some breeds more than others. Biologists often break the predatory sequence into several steps: Search → Stalk → Chase → Bite (kill) → Dissect → Consume. Different parts of this sequence are still strong instincts in domestic dogs, particularly the first four (search, stalk, chase, and bite). Humans have bred dogs specifically to emphasize some of these steps. Some, like bloodhounds, were bred to amplify the search stage (using smell). Herding dogs have been bred to enhance search, stalk, and chase, but to reduce the bite (kill) step, to avoid danger to the livestock they are supposed to protect. And some dogs were bred to retain most of the entire sequence, such as rat terriers, bred to find and kill varmints. Most dog breeds have, to some extent, retained the chase and bite portions of the sequence. And this, of course, is why dogs love to chase balls over and over. Dogs are irresistibly drawn to chasing things that move. And they like biting and chewing these things when they catch them. When a dog grabs a ball or other dog toy and shakes it, the dog is essentially "killing" it (like breaking the neck of a small critter). And, of course, dogs like to chew things up and tear them to pieces because this is the "dissect" portion of the sequence. Unfortunately, some dogs even get sick because they ingest portions their toys (the "consume" portion of the sequence). This love of chasing balls is reinforced by the dogs' desire to interact with people. Which in itself is a result of thousands of years of the symbiotic relationship between humans and dogs.  Photo Credit: - Man and dog on beach - Stan C. Smith The first photo is an EASTERN MILKSNAKE. Milksnakes are actually a type of kingsnake. They got their name from an old myth that these snakes get into barns, latch on to the teats of cows, and suck out the milk. I’m not kidding. Of course it isn’t true, but farmers may have come up with this because they found milksnakes in their barn (the snakes were actually there to feed on mice). Maybe a farmer was frustrated by a cow that wasn’t producing enough milk, then blamed it on a snake found nearby? Milksnakes are an example of Batesian mimicry, in which a harmless species resembles a harmful species as a form of protection. Many of the 24 subspecies of milksnakes overlap with venomous coral snakes. The resemblance is unmistakable. However, Missouri does not have coral snakes. But our eastern milksnake is still considered a mimic of the copperhead, even though the colors don’t match. In this case, it is the patterns that are similar. Remember, not all predators can see colors, but they can see patterns, and the eastern milksnake’s pattern is close enough to a copperhead’s pattern to fool some animals into leaving the snake alone. The second photo is a WESTERN WORM SNAKE. Few people ever see these snakes because they live in the soil and under rocks and logs. Their bright pink belly is a striking feature. These harmless little snakes have a hard, pointy tip at the end of their tail, and when attacked, they will poke the attacker with this tip, which sometimes startles the attacker, allowing the snake to escape. Because of this, some people claim this snake can sting. But this isn’t really a sting because the snake has no venom in its tail. In fact, the tail won’t even pierce skin. Another defense is, when picked up, they wriggle like crazy, making them hard to hold. A third defense is, like some other snakes, they secrete bad-smelling gunk when picked up. Trust me, it’s nasty stuff. Worm snakes love to eat earthworms, which they grab by one end and swallow alive. Gotta love snakes, am I right?   Photo Credits: Milk snake and worm snake - Stan C. Smith Our normal response to another person tickling us is to pull away, to put an end to the discomfort. Because it really is discomfort, right? Almost like a type of pain. We squirm, we run away, we do whatever we can to put an end to it. Laughing seems like a weird response to such discomfort. We don’t laugh when we burn our finger on a hot pan, yet we pull away from a tickle as enthusiastically as we pull away from a hot pan. What’s up with the laughing? Why don’t we cry or shout instead? I should point out that humans are not the only animals capable of laughing. Scientists have found that at least 65 other species laugh (hyenas are not one of them, by the way). And some of those also laugh when tickled. Researchers recognize two types of tickling. Light tickling (knismesis), which is light touching with fingers or something like a feather. People can often respond to this in different ways, and they do not have to laugh. Heavy tickling (gargalesis) is intentionally touching sensitive areas like feet and armpits intending to get a reaction. When getting their feet tickled, most people have to laugh, even if they try not to. It’s involuntary. Other species of great apes also laugh when their feet get tickled. When we get tickled, the nerve endings under the skin send signals to our brain. The anterior cingulated cortex analyzes the signals—this is the part of the brain that deals with the perception of pleasure. So, it’s important to know that your brain is interpreting the sensation as a type of pleasure (this helps explain why we respond with laughter instead of aggression). But there’s more. The hypothalamus is the part of the brain that tells us to laugh when we are lightly tickled, but it is also the part of the brain that tells us we should expect pain when something is touching our most sensitive spots. The amalgamation of all these signals usually results in laughter. That may explain how we end up laughing, but it doesn’t explain WHY. Evolutionary biologists and neuroscientists suggest that this response might have evolved as a defensive mechanism. Think of it this way… when a dog is intimidated by a larger dog or person, the dog will show submissive behavior, like rolling on its back to expose its vulnerable belly. This serves to signal that the dog is not being aggressive and is not looking for a fight, and therefore this behavior often prevents escalation. Well, the same idea could be true for laughing when being tickled. Laughing signals that we are not angry, that we are not the aggressor. Contributing to this is the fact that we know tickling is typically something people do out of fun, rather than as an attack, and therefore we do not need to do something more aggressive than laugh. And this helps explain why we don’t laugh when we tickle ourselves. The cerebellum of your brain knows that you are about to self-tickle, and therefore it doesn’t bother wasting energy sending signals to the other parts of your brain that would trigger a laughing response. Your brain knows there is no need for a defensive response. It knows you do not need to signal another person to show that you are not angry.  Trish and I were sitting on our deck recently, and we noticed a little ball of fuzz that seemed to be walking across the glass tabletop. The fuzzball was less than a centimeter long. Fascinated by this strange sight, we looked closer and saw that it actually had legs, and a head with two large, wicked-looking mandibles. The first photo is the best one I could get with my phone. You can see legs and the mandibles. We decided it had to be some kind of insect. Perplexed, we did some research. It turns out this is the larva of a green lacewing. These are often called debris-carrying lacewing larvae. AKA junk bug or trash bug. Yes, it's a real thing. These insect larvae disguise themselves by attaching junk to their backs. You can't make this stuff up. The larvae of some green lacewings have numerous bristles on their backs, allowing them to pick up pieces of junk and attach them to their back, as camouflage. They attach plant fibers, lichens, miscellaneous debris, and their favorite—the dead bodies of their victims. Green lacewing larvae (and adults) are predators, preying on aphids and other tiny soft-bodied insects. Hence the wicked-looking mandibles. They grab insects with those mandibles and suck the juices from their bodies. Then, instead of leaving the dry husks of their victims behind, the larvae plop them onto their back, adding new junk to their clever disguise. The second photo is a debris-carrying lacewing larva sporting the remains of its many victims. So, is there any proof that this trash-carrying habit actually helps hide the lacewing larvae? After all, maybe these little trash-mongers simply consider the heap on their back to be fashionable. Actually, there is proof. I'll explain a few details. You may know that ants are often the guardians of aphids. Ants and aphids have a fascinating symbiotic relationship, in which aphids provide ants with honeydew (a yummy food rich in sugar). The ants actually "milk" the aphids by stroking their backs, causing them to secrete honeydew, which the ants happily slurp. In return, the ants protect the aphids by attacking any aphid-loving predators (such as lacewing larvae) that come near the aphids. Well, biologists, being forever curious, removed the trash from the backs of lacewing larvae. When these trash-free larva attempted to enter an aphid colony, the ants quickly identified them and attacked. However, when the lacewing larvae were allowed to keep their trash piles on their backs (consisting mainly of aphid carcasses), they easily snuck by the ants undetected and gorged themselves on tasty aphids. So, if you ever see a tiny walking pile of junk, take a closer look, and compliment the lacewing larvae on its clever, stylish disguise.   Photo Credits: - Lacewing larva on glass table - Stan C. Smith - Lacewing larva on white background - DepositPhotos A few cool critters I've found near the house recently. The first photo is one of the prettiest GRAY TREEFROGS I've seen. As you might guess, gray treefrogs are usually gray in color, Their mottled pattern makes them look like lichens on a tree. However, especially around their breeding season, many of them turn green, like this one. Gray treefrogs typically eat insects, but when they get larger, they will feed on anything that moves, including smaller frogs. Around our house, whenever it rains, the gray treefrogs start singing (singing in the rain!). The second photo is a FIVE-LINED SKINK I found hiding under a rock. Five-lined skinks are common in Missouri, though they are secretive. If you are walking in the woods and hear something scuttling away in dry leaves, it's probably a five-lined skink. The juveniles of this lizard species have bright blue tails, so some people call them blue-tailed skinks. But this name is confusing because many types of skinks have blue tails as juveniles. When a predator attacks a juvenile skink, the skink's tail will break off and wriggle around—the bright blue wriggling thing distracts the predator, allowing the young skink to escape. The third photo is a RED-BELLIED SNAKE. It's probably obvious how it got its name. These harmless little snakes like to snarf up slugs, snails, and earthworms. They have a special adaptation for eating slimy snails—extra-long teeth. These teeth allow the snake to grab a snail's soft body and pull. The snail eventually grows tired of the fight, and the snake actually pulls the snail's soft body out of its shell to consume it. These snakes also have an odd habit of flaring their lips out, which is probably a behavior that exposes their teeth to better hold on to their slimy prey. Isn't it awesome that so many amazing little critters are hanging around underfoot and in the trees above?    Photo Credits: All photos by Stan C. Smith |
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