The Diverse World of Colubrids
Kingsnakes, hognose snakes, and boomslangs are all very different from one another but have one very big thing in common, they are all part of the Colubridae family. This particular family of snakes is the largest and most diverse family boasting upwards of 2,000 species that can be found on every continent except Antarctica because of the extreme cold and ice that makes the continent impossible for colonization by reptiles. Despite the diversity in the multitude of species that make up the Colubridae family, there are a few similarities that can help to identify each member as a colubrid.
A close up of a kingsnake named Xena.
In general, there are three features that are present in every colubrid species that tie them all together and have laid the groundwork for defining this particular taxon. The first characteristic that can be observed by anyone is the collection of large, plate-like scales that cover the heads of most colubrids. This basically means that most colubrids have noticeably larger scales on their heads than on the rest of their bodies when they are compared to species in other families that have scales that are fairly consistent in size no matter where you look at the snake. If you move a bit deeper than the scales, you will find that colubrids lack a functioning left lung leaving them with only a functioning right lung and a small sack where the left lung would have been. This, however, is not entirely unique to colubrids, and most species of snake have similar respiratory anatomies with only one functioning lung as a result of their narrow bodies.
The third trait that is fairly unique to colubrids is that they have a vestigial pelvic girdle remnant of their lizard ancestors. This basically means that they still have some sort of skeletal structure that is recognizable as a nonfunctioning pelvis that has become obsolete during their evolution, like the appendix in humans. This shadow of their evolution is lacking in snake species that are not members of the colubrid family and seems to have resulted in the constricting colubrid species having a distinctly different technique than their boa and python counterparts. While the extra structure is no longer essential for a colubrid to survive, it does restrict their movement and slightly changes the way they interact with their environment and prey when contrasted with other serpent families.
Hognose snake. Credit: Peter Paplanus - flickr
The three traits mentioned above, however, is where the familial similarities end. Colubrids are just as diverse as snakes as a whole. Colubrids can be found in nearly any habitat from the treetops to the water and can specialize in nearly any diet available to them from rodents to fish, and sometimes even other snakes. Since they have so many living and dining options, colubrids have also developed different strategies to subdue their prey, some species like kingsnakes and corn snakes use constriction to catch a meal, while other species rely on various venom techniques.
Even venom in the colubrid world is diverse, with varying toxicity and fang placement. Species like the hognose snake are popular in the pet trade despite being rear-fanged venomous, meaning that they have fangs situated in the back of their mouths as opposed to the front like a viper or cobra. Hognose snakes boast a fairly mild venom that is often compared to that of a bee, and rarely causes harm to humans unless there is an allergic reaction, again similar to an allergic reaction to a bee sting. The relatively harmless venom of the hognose snake can be contrasted to the boomslang, a rear-fanged species from Africa with highly toxic venom.
Boomslang. Credit: Johan Marais
The Colubridae family is so diverse because it was originally referred to as a “wastebasket taxon” where scientists could lump any snake that did not clearly fit into another family. Through the use of molecular phylogenetics, a branch of science that analyzes genetic differences, researchers have determined that colubrids are a monophyletic clade or group of species that have evolved from one common ancestor. As of May 2018, colubrids have been grouped into eight different subfamilies and 249 genera, but this classification is disputed by some scientists since taxonomy is a constantly changing science.
References:
https://www.britannica.com/animal/colubrid
https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/colubridae
