Egg-eating Snakes

Egg-eating Snake (Dasypeltis fasciata) photo by Bill Bouton

To continue “egg week” we encounter a creature which not only reproduces through laying eggs, it lives entirely by eating them!  Meet Dasypeltis,  a genus of colubrid snakes of Africa.  There are 12 recognized species of Dasypeltis snakes ranging across the great continent (they are non-venomous, by the way).  These serpents are all oophagous , which is to say they eat eggs…  In fact they are exclusively oophagous—they eat nothing but eggs! Gosh!

The adult snakes range in size from 30-100 cm (12-39 inches) in length and come in a variety of unobtrusive colors.  They have ridiculous jaws of vast flexibility which can expand to many times the diameter of their head so that they can eat eggs which are much wider than their bodies.   This leads to some disturbing-yet-amazing-photographs which would make even the greatest champion-eater envious. Egg-eating snakes have a highly developed sense of smell–they are capable of telling if an egg has gone off, or if it has developed past a point where it is easily digestible.

Photo by David A. Northcott

These egg-eating snakes do not have teeth as such; instead they have hard ridges on their spine which allow the snakes to break open the eggs after swallowing them.  So once the egg is safely inside the snake’s gullet, the hungry creature breaks it into pieces inside itself and sucks the nutrients out (whereupon it regurgitates all the shell fragments).  This strikes me as an insane way to get nutrients, but it apparently works surprisingly well:  snake nutritionists (?) calculate that “snakes are remarkably efficient and waste very little of the contents of an egg.”  Because of the way egg-eating works in the wild–where one tends to discover a lot of eggs at once or none at all—the snakes can eat a number of eggs in one uh…sitting (can I say “sitting” in this context?). They then go semi-dormant during the wet season (all of which means that distraught reptile enthusiasts sometimes force feed quail eggs to their pet egg-eating snakes—which also strikes me as insane).

Photo by Jonathan Brecko

 

The African Wildcat

Felis silvestris lybica

Aww! Wook at the wittle puddy-tat… Argh! Wait, that isn’t a puddy cat at all, it is actually Felis silvestris lybica, the African wildcat, a formidable crepuscular predator which ranges across the Sahara and Sahal up through the Arabian Peninsula and around the Caspian Sea. Although they are remarkable hunters, African wildcats are not large—males measure 46–57 cm (18–22 in) in head-to-body length (discounting the elegant tail) and weigh from 3.2 to 4.5 kg (7 to 10 lbs). Using stealth, speed, retractable claws, and athletic lunges, the wildcats hunt and kill everything smaller than themselves: small mammals are their main prey but cats also kill birds, reptiles, insects, amphibians, and miscellaneous arthropods. African wildcats hunt mostly at dawn and dusk, but thanks to incredibly keen senses, they can also hunt at day or night.

An African wildcat executes an insane flip while hunting doves

The senses of the African wildcat are truly astonishing. Their large vertically slitted eyes are extremely efficient in brightest day or in the faintest light (thanks partly to the tapetum lucidum—a layer of reflective cells at the back of the eye which reflects light back into the photoreceptors). Wildcat hearing is among the best in the animal kingdom—they can hear many ultrasonic noises inaudible to humans and dogs (cats developed this sense because many rodents and insects communicate with such noises). Their large mobile ears further augment their acute hearing. Although they do not have the unbelievable noses of dogs or wolves, wildcats have an amazing sense of smell which is estimated to be 14 times more acute than a human’s. Additionally, their heads (and particularly their faces) are covered with vibrissae (whiskers) to help wildcats sense vibrations and navigate in tight pitch black spaces.

African wildcat close-up

As well as keen senses, African wildcats possess other features which help them fit into their harsh arid environment. They have striped stippled coats which are the color of rocks, dry grass, and earth—so they blend in to most environments effortlessly (although they tend to have lighter colored bellies). Living in vast deserts, African wildcats have shockingly efficient kidneys. The animals can live without water on the fluid from prey animals. If necessary, they can rehydrate with seawater. They can also survive extremely hot temperatures and do not show discomfort until 52 °C (126 °F).

African wildcat kitten

Felis silvestris lybica is actually one of several subspecies of old world wildcat Felis silvestris which ranges across all of Europe, Africa, and Asia. Wildcats are very, very versatile, resilient, and effective predators, yet all of the subspecies of wildcat are gradually losing their genetic diversity except for the African wild cat. This is because of interbreeding with the domestic cat Felis silvestris catus. As you have probably gathered by now, domestic cats descend directly from a handful of African wildcats which were domesticated in the Fertile Crescent between 10,000 and 9,000 years ago when humans first became grain farmers. The first domestic cat was found buried in a Neolithic grave in Cyprus which dates back to 9,500 years ago. The wildcats (Felis silvestris) are all fully fertile when breeding across species, so some of the differences between the wildcat and the domestic cat are fairly arbitrary.

Eek, there is an African wildcat in my living room! Wait, that’s my beloved housepet Sepia. You can tell by, um, the white bib and gloves…I guess?

Sensitive Siluriformes–How Catfish Perceive the World

Synodontis schoutedeni catfish (Credit: Oliver Drescher)

So what’s so amazing about catfish?  So far, Ferrebeekeeper has describing all sorts of different variations of these fascinating fish. From the giant truck-sized catfish of the Mekong, to the infinitesimal (yet horrifying) candirus of the Amazon, to the deadly poisonous schooling catfish of coral reefs, to catfish that live underground or in gardens, we have seen a seemingly impossible variety of the irrepressible whiskered creatures. But, aside from their variety, hardiness, and interesting appearance, catfish represent an extraordinary apogee in sensory ability.  They are able to apprehend their watery realms in ways that might as well be supernatural or alien to us.  Catfish have honed familiar senses—taste, smell, touch, hearing, and sight–to outrageous extremes. Yet they have additional senses—electroreceptivity, pressure sensitivity, and possibly other senses–that we are only starting to understand.

Channel catfish, Ictalurus punctatus

Let’s start with catfish’s sense of taste: catfish, unlike us, are not limited to tasting things with their tongues.  Their entire bodies are covered with taste buds.  To quote catfish expert Dr. John Caprio of Louisiana State University, “Catfish are swimming tongues…You can’t touch any place on a catfish without touching thousands of taste buds. To use an analogy, it’s as if the tip of your tongue grew out and covered your body.”  Catfish can literally taste the water all around their bodies and the mud they are swimming over.

Red-tailed Catfish, Phractocephalus hemioliopterus (Photo by Chad Cullen)

Beyond their powers of taste, catfish have a bloodhound-like sense of smell. With astonishingly sensitive olfactory pits near their nostrils, Catfish can smell certain compounds at one part per 10 billion parts of water. The sense of smell does not merely help them while hunting and seeking food, catfish use smell to identify other individual catfish and to maintain a social hierarchy.  A catfish has an elaborate picture of its watery realm, the denizens thereof, and of the history and interaction of these inhabitants based on smell.

Catfish Barbels

Catfish’s scale-free skin is unusually sensitive to touch but that is not the end of catfish’s ability to feel what is going on around it.  The most distinctive feature of catfish—their 8 barbels (whiskers) are literally organs for touching.  Like a blind man’s cane, each of these barbels can touch the substrate or whatever is moving in front of the catfish.  Not only are the barbels covered with taste buds and feeling nerves, the whiskers also vibrate with water disturbance and provide a sense almost like hearing—although catfish also have multiple hearing organs.

Black Bullhead Catfish (notice the prominent lateral line)

Vibrations travel well under water and most fish have excellent abilities to sense sound, but catfish have evolved some additional auditory features.  The swim bladder of a catfish (which the fish uses like a submarine ballast in order to rise and fall through the water column) is connected by a series of small bones (the Weberian apparatus) to the hearing apparatus (otoliths) inside the head. Catfish are therefore able to hear sounds of a higher frequency than other freshwater fish.  Catfish can also sense extremely low-frequency sounds thanks to a different hearing system—a series of small pores running along the fish’s lateral lines. Within the pores are infinitesimal hair-like sensing apparatuses which respond to the slightest water displacement. Using lateral line hearing, a Catfish can sense animals scuttling across the rocks on the bottom of a river, predators swimming above them, and even fishermen walking on the shore. Perhaps most remarkably, the low frequency sensors which catfish have in their lateral lines seem to give the fish the ability to detect seismic activity.  The Chinese and Japanese are said to have used the creatures as advanced earthquake detectors (which probably gave rise to the myth of Namazu, the Japanese earthquake catfish).

Although some catfish have small or underdeveloped eyes, the majority of catfish species can see extremely well. Additionally catfish possess a tapetum lucidum—a layer of reflective tissue at the back of the eyes which allows them to see keenly in low-light conditions (cat owners will recognize the tapetum lucidum as the flashing green glow of feline eyes).

Catfish in an Aquarium (further documentation required)

Finally catfish can sense the electrical discharges within the nervous and electrical-muscular systems of living things (in fact the electrical catfish goes a step beyond and uses electricity for hunting and self-defense).  The cells responsible for electroreception are found grouped together in tiny pits along the catfish’s head and along its lateral line.  Although electroreception has limited range, it is a powerful sense which can allow the fish to sense animals hidden beneath the mud or otherwise camouflaged.

A catfish’s life must be exciting—awash as they are in complicated overlaying sensory perceptions.  Their abilities to perceive the world have taken them farther than other fish. According to the Tree of Life web project:

Catfishes are a species rich and exceptionally diverse group of fishes ranking second or third among orders of vertebrates. The Catalog of Fishes (Eschmeyer, 1998 et seq.) database treats 2,855 species of catfishes as valid. About 1 in 4 valid species of freshwater fishes, 1 in 10 fishes, and 1 in 20 vertebrates, is a catfish.

Several hundred more species of catfish have been discovered since the above paragraph was written.  Paleontologists have even discovered fossils of catfish on Antarctica (the only continent where they can not currently be found living). Catfish are basically sentient sense-organs.  They have diversified and thrived by being able to discern what is going on in the world around them (and they have probably enjoyed the experience).

Ancistrus Bristelnose Catfish