Not a Baby, Not Yet an Adult

‘Tis the time of year when the northern hemisphere is inundated with new “teenagers” for lack of a better term. Not a baby, but not yet an adult, the most obvious of these are the hordes of juvenile birds who, although they’ve left the nest, are still largely dependent upon their parents. Perhaps you’ve seen them fluttering their wings, big fleshy-gaped mouths open and squawking in your backyard, the local park, or while out hiking.

Juvenile House Wren. Photo by Jamie Simo.

Do you remember being a teenager? For me, it was all pimples, awkwardness, and angst. So much angst. It was like a 24-7 John Hughes marathon without the catchy soundtrack and zany hi jinks. If I were to relive any age, it would not be a double-digit number beginning with 1.

I’m sure some people would love to go back to being a teenager, though. That’s completely understandable if you didn’t have to buy groceries, hold down a job, or pay taxes. But would you ever choose to be a teenager forever? That’s less John Hughes and more Peter Pan and some animals actually do live out their lives never becoming full-adults, a phenomenon called pedomorphosis, or alternately, neoteny.

Western tiger salamander larva. Photo by Jamie Simo.

Pedomorphosis (from the Latin pedo for child and morphosis for the process of forming) means that juvenile characteristics are retained into adulthood. The best known example is probably the axolotl, a large, Mexican salamander. In Colorado, we have a close relative of the axolotl that also sometimes exhibits this ability, the Western tiger salamander (Ambystoma mavortium).

Barred Tiger Salamander
Barred Tiger Salamander (Ambystoma mavortium mavortium) from Weld County, Colorado, USA. Photo by Andrew DuBois. https://flic.kr/p/NLjL2o

In the typical life cycle of an amphibian like the Western tiger salamander, the salamander would develop from a gilled aquatic larva to a land-dwelling, sexually-mature adult. However, if conditions on land aren’t favorable–if for instance, conditions are too dry– the salamander may stay in its gilled larval form for decades until conditions change. If conditions don’t change, it may even stay a “teenager” forever, becoming able to reproduce despite not technically being an adult.

While I wouldn’t want to stay a teenager, the Western tiger salamander makes it work and is another example of the ingenuity of nature.

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One thought on “Not a Baby, Not Yet an Adult”

  1. Those birds must get one or two eggs to become adults. Horses there are indeed of teenage birds but equally many broken eggs and baby bird bodies. I like how you merged that into a fascinating lesson and example of pedomorphism.

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