Category: The Wonders of Creation

Homing pigeons have been bred to be able to find their way home, almost no matter where they are released. They have been used for more than 2,500 years to deliver messages in a fast, reliable way. For example, a homing pigeon was used to deliver the results of the first Olympiad back in 776 BC.¹ Because they have been used for such a long time, scientists have tried to figure out how pigeons are able to navigate their way from an unknown location back to their home. While scientists have been able to figure out some aspects of homing pigeon navigation, the details haven’t been entirely worked out.

It was once thought that homing pigeons use visual landmarks to help in their navigation, but experiments in which the pigeons’ eyesight was reduced using frosted contact lenses showed that’s not correct. Other experiments demonstrate that homing pigeons can sense the earth’s magnetic field, but many of those same experiments also show that disrupting that sense doesn’t always end up leading the pigeons astray. In addition, some experiments indicate that homing pigeons use the position of the sun in the sky to orient themselves, but that can’t be the entire explanation, either, because pigeons can navigate even on very cloudy days. It seems, then, that pigeons use a wide variety of strategies to navigate their way home.²

The mystery of homing pigeon navigation deepened back in 1997, when the Royal Pigeon Racing Association decided to celebrate its 100th year anniversary by releasing 60,000 pigeons in the south of France. These pigeons came from homes throughout southern England, and they were expected to be able to reach those homes in a few hours. While a few thousand of them ended up returning to their homes over a period of a few days, most never made it back.³

Over the years, several hypotheses have been put forth to explain why those pigeons never made it home. One of them suggests that the pigeons’ navigation was disrupted by the sonic boom of the Concorde jet whose flight path crossed that of pigeons. A recent study by Dr. Jonathan T. Hagstrum adds some support to this hypothesis.

Continue reading “Homing Pigeons May Hear Their Way Home”

When I was in Costa Rica last year, I saw several Central American agoutis, such as the one pictured above. I didn’t know anything about them, so when I got back home, I looked up some information. They can be omnivorous, but they prefer to eat seeds and fruit. One of their interesting behaviors is to follow troops of monkeys. They “hang out” underneath the trees that the monkeys climb, and they eat the fruit that the monkeys drop or inadvertently shake off the trees.¹

Another really interesting thing about the Central American agouti is that it’s a scatter hoarder.² This means it collects seeds and buries them in multiple locations. It remembers these locations and returns to them when food is scarce. However, it doesn’t just bury them once and leave them there. It often revisits its stores of seeds, digs them up, and reburies them somewhere else.

While this behavior is beneficial to the agouti (it provides storehouses of food for when food is scarce), it is also beneficial to the trees that drop the seeds. That’s because the agouti rarely uses all of its stored seeds. As a result, some of the buried seeds grow and develop into new trees. This means that the Central American agouti is, in fact, a “farmer” for the trees. It moves seeds away form the tree that drops them and plants the seeds so they can grow into new trees.

Why is this beneficial to the trees? If a seedling grows too near the tree that dropped the seed, it ends up competing with its parent tree. That’s not good for the parent or the seedling. By carrying the seed far from the tree and planting it, the agouti allows the seedling the chance to grow without competing with its parent. Pretty nifty, huh? Well, recent research shows its even niftier than that. It turns out that these “tree farmers” are smarter than we originally thought.

Continue reading “Nature’s Farmers Are Pretty Smart!”

Almost everyone has experienced it. When you have been soaking in the bathtub, swimming, or just washing dishes for a long time, the skin on your fingers (and toes) wrinkles. From a scientific point of view, there are at least two questions to consider: (1) How does this happen? and (2) Why does this happen? Most textbooks explain (often incorrectly) the how, but I haven’t found any that explain the why. It seems that over the years, scientists have been studying this, and in the end, they have mostly answered both questions.

Let’s start with the “how.” A lot of textbooks and websites incorrectly explain this part. They say that it is the result of your skin absorbing water and swelling. It turns out that’s not true at all. More than 70 years ago, scientists showed that if certain nerves to the hand are damaged, its skin will not wrinkle, no matter how long it stays underwater.¹ Over the years, other scientists have investigated water-induced wrinkling, and it seems to be the result of a process initiated by the nervous system.

Your skin is made of two layers: the epidermis (the layer you see) and the dermis (the layer underneath that contains blood vessels). When your hands and/or feet have been underwater for a long time, your nervous system tells the blood vessels in your dermis to constrict. This reduces the volume of the dermis, which in turn reduces the tension with which the epidermis is stretched. As a result, the epidermis “relaxes,” forming wrinkles.²

This answer is interesting enough, because I have long taught the incorrect explanation for how your skin wrinkles underwater. I am glad that I learned I was wrong on the point, and I will now start teaching the correct explanation. However, the “why” question is also very interesting, and a couple of recent studies have provided a good answer for that question as well.

Continue reading “Why (and How) Your Skin Wrinkles Underwater”

I have always been fascinated by sharks. In fact, of all the times I have been scuba diving, the dive I remember the most occurred off the coast of South Africa. I went with some marine biologists who had been studying sand tiger sharks (Carcharias taurus). As I initially sunk down into the water, I leveled out just a few feet from the bottom, and as I was checking my gauge to determine my depth, a 2-meter (6-feet) long shark swum right underneath me! We ended up seeing more than a dozen sharks of various sizes on that dive. It was incredible.

One of the things that is fascinating about sharks is the way they hunt. While they use their sense of smell (and to some degree their sense of sight), one of their main hunting techniques involves using their electrical sense. Yes, sharks can sense electrical fields, and they are quite good at it. As a recently published book on sharks says:¹

They can detect the minute electrical currents generated by the nervous systems of prey by using electrical sensors called the ampullae of Lorenzini…These sophisticated sensors are very useful in finding prey buried under the sand.

Interestingly enough, these sophisticated sensors often develop while the shark is still an embryo. Is that just to get the shark ready for hunting its prey when it is fully developed, or could there be some use that the embryo has for sensing electrical fields? It doesn’t need to hunt, so for what purpose could it be using its electrical sensors?

Some Australian scientists decided to investigate this issue, and what they found is fascinating!

Continue reading “Even Shark Embryos Detect Electric Fields”

Salmon have an incredible lifecycle. They hatch in freshwater streams, eat and mature a bit, and then they make their way into the ocean. They do most of their growing and maturing in the ocean, and when they are ready to reproduce, they return to the very stream from which they hatched to find a mate and begin the cycle all over again.

A lot of research has been done trying to figure out how the salmon know the way back to the specific stream from which they hatched. Well, each stream has it own mix of soil, rocks, and other environmental elements. As a result, each stream has its own specific mix of chemicals. Most of the data indicate that a salmon remembers the specific chemical makeup of its original stream. Once it gets back to freshwater, then, it starts following a “chemical trail” that will lead it back to the stream from which it hatched.¹

While this is rather impressive, it doesn’t really tell us about the most difficult navigational aspect of the journey. The salmon spends a long time in the ocean growing and maturing. As a result, it often ranges far from the place where it entered the ocean. How does it find its way back to the correct freshwater inlet that will lead to the correct stream? It seems hard to believe that it could follow a “chemical trail” that far! Since we know that salmon are equipped with biological machinery that allows them to sense the earth’s magnetic field, it has been thought for some time that salmon use magnetic guidance to get them to the proper freshwater inlet.²

While that’s a reasonable conclusion based on what we know, there hasn’t been a lot of evidence to back it up. However, a recent study published in Current Biology has begun to remedy that situation.

Continue reading “Sockeye Salmon Use Geomagnetic Details to Guide Them Home”