My birthday is December 24th. That’s the day before Christmas. Often people ask me if I feel “gypped” or “short-changed” by my birthday’s proximity to the year’s most gift-laden holiday and the answer is: yes. It’s not so much the gifts that matter to me as the acknowledgement. My birthday always feels like a footnote in the larger holiday atmosphere. However, I have noticed that I tend to get double the amount of greeting cards — one for Christmas and one for my birthday, sometimes in the same envelope, and usually from more distant family and friends. This year I got a particularly interesting one:
According to the back, this is a “least weasel” — it’s seven and a half inches long, weighs little over a pound, and is “one of the world’s greatest predators.” Further research led to the explanation that this means least weasels can take down rabbits 5-10x their body weight and their preferred part of the animal to eat is the brain. The word “weasel” comes from the anglo-saxon “weatsop” meaning “a vicious bloodthirsty animal” — I learned that also. However, it’s not the word “weasel” and its extra-cultural associations I’m interested in as much as it is the preceding word — “least” — which would seem to imply that the least weasel is yes, a weasel, but not as much as other weasels.
Of course, “least weasel” is not its scientific name. Its scientific name, in standard binomial nomenclature, is mustela nivalis — literally “snowy weasel,” descriptive of the white coat it dons in the wintertime. The name “least weasel” is what’s known as a common name, the way “human” is to “homo sapien,” and, as far as my research has informed me, the “least” part of its common name is solely a description of its diminutive size. The least weasel is the smallest member of the weasel family and the smallest predator in North America. Again, though, the word “least” is curious in its implication that there are other, more qualified weasels out there, that the least weasel somehow got the short end of the evolutionary stick. And yet, a study recently found that the least weasel has “ounce for ounce the most powerful jaws of any predator in North America,” thus, in at least this one way, it seems the least weasel might actually be the most weasel.
Further, as you may or may not be aware (I wasn’t), there are other “least” animals out there. There’s a least shrew, a least bittern, a least killifish, and a least tern — and, like the least weasel, they are each very small. Let’s look at them…
The least shrew — cryptotis parva (literally “small shrew”) — is indigenous to North America and, at 3 inches in length, is one of the smallest mammals in the world. It’s also one of the only mammals in the world to possess venomous saliva. Chemically similar to cobra venom, a least shrew bite is toxic enough to paralyze small insects, but not potent enough to do more than a bee sting’s worth of damage to larger animals. Due to their large surface-area-to-body-mass ratio, their metabolism is extremely inefficient so they rarely sleep and need to eat constantly. To stay alive, they eat between 60 to 100% of their body weight daily. Their primarily food source is insects and, because their eyes are small and ears concealed, they do most of their hunting by smell and touch. It’s rare for a least shrew to live much more than a year.
Something of a trophy for bird watchers, the elusive least bittern — ixobrychus exilis (literally “slender bittern”) — is the smallest heron in the Americas. Its migratory nature takes it as far north as southern Canada and as far south as Brazil. One interesting fact is that the least bittern prefers to flee its predators by foot rather than flying.
The least killifish — heterandria formosa (literally “differently formed male,” stemming from a sexual dimorphism) — is also known as the “dwarf livebearer.” It’s the smallest fish in North America and one of the smallest in the world. It is also one of the smallest vertebrates in existence, averaging 2-3 cm in length. The least killifish is a popular choice for home aquariums due to their “durability” and low maintenance.
The least tern — sternula antillarum (literally “small tern”) — is the smallest of the American terns. It weighs approximately 1 ounce and averages around 9 inches in length. It’s migratory, spending winters in warmer Central and South American climates. Unfortunately, their nesting behaviors incline them towards human developments such as recreational beaches, gravel paths, and rooftops — where nests are subject to any number of disruptions. Certain subspecies have spent time on endangered and threatened species lists, both at federal and state levels, but recent conservation and awareness efforts have seen population numbers rebound and stabilize.